ENVIRONMENTAL
SCIENCE and
ENGINEERIN
SECOND EDI
HENRY GARY
W. HEINKE
FREQUENTLY USED ATOMIC WEIGHTS
Atomic
Symbol
Element
weight
Magnesium
Manganese
Mg
Mn
24.31
39.95
Mercury
Hg
200.59
74.92
Molybdenum
Mo
95.94
Nickel
Ni
58.71
Nitrogen
N
O
14.01
Oxygen
10.81
Phosphorus
P
30.97
Element
Aluminum
Al
26.98
Antimony
Argon
Sb
Ar
121.75
Arsenic
137.34
Beryllium
As
Ba
Be
Bismuth
Bi
208.98
Boron
B
Barium
Atomic
Symbol
weight
9.01
54.94
16.00
Bromine
Br
79.90
Platinum
Pt
195.09
Cadmium
Cd
112.40
Potassium
K
39.10
Calcium
Ca
40.08
Selenium
Se
78.96
Carbon
C
12.01
Silicon
Si
28.09
Chlorine
CI
35.45
Silver
Chromium
Cr
52.00
Sodium
Ag
Na
Cobalt
Co
Cu
F
Au
He
58.93
Strontium
Sr
87.62
63.55
Sulfur
S
32.06
19.00
Tantalum
Ta
189.95
Tin
Sn
118.69
4.00
Titanium
Ti
47.90
1.01
Tungsten
W
183.85
Uranium
Vanadium
U
V
Zinc
Zn
65.37
Zirconium
Zr
91.22
Copper
Fluorine
Gold
Helium
Hydrogen
196.97
H
126.90
Iodine
I
Iron
Fe
55.85
Lead
Pb
207.19
Lithium
Li
6.94
107.87
22.99
238.03
50.94
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mu
gamma
delta
theta
lambda
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X
X
chi
V
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omega
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Digitized by the Internet Archive
in
2012
http://archive.org/details/environmentalsciOOhenr
Environmental
Science
and
Engineering
Second Edition
J.
Glynn Henry and Gary W. Heinke
with contributions by other scientists and engineers:
Ian Burton
F.
William
Kenneth Hare
Thomas
C. Hutchinson
Donald Mackay
Prentice Hall,
Upper Saddle
J.
Moroz
R.
Ted Munn
O.
J.
River,
C. Runnalls
New
Jersey 07458
Library of Congress Cataloging-in-Publication Data
Henry, J. Glynn
Environmental science and engineering / by J. Glynn Henry and Gary
W. Heinke; with contributions by other scientists and engineers,
2nd ed.
Ian Burton ... (et al.].
—
p.
cm.
Includes bibliographical references and index.
ISBN 0-13-120650-8
I.
1. Environmental sciences.
Heinke, Gary W.
II. Title.
1996
2.
Environmental engineering.
GE105.H46
628—dc20
95-33505
CIP
BILL STENQUIST
IRWIN ZUCKER
Acquisitions Editor:
Production Editor:
Cover Designer:
Buyer:
JULIA
BRUCE KENSELAAR
MEEHAN
Editorial Assistant;
MEG WEIST
Cover photograph by Adrian Dorst shows two Orca Whales off Clayoquot
(pronounced clack-wit) Sound, an 800 square mile rain forest on the west coast
of Vancouver Island, where environmentalists are opposing clear-cutting by the
forestry companies.
©
1996 by Prentice-Hall,
Inc.
Simon & Schuster / A Viacom Company
Upper Saddle River, NJ 07458
All rights reserved.
reproduced,
in
No
part of this
book may be
any form or by any means,
without permission
in writing
The author and publisher of
from the publisher.
this
book have used
their best efforts in preparing this
book. These efforts include the
development, research, and testing of the theories and programs to determine their effectiveness. The author and
publisher
contained
in
make no warranty of any kind, expressed or implied, with regard to these programs or the documentation
in this book. The author and publisher shall not be liable in any event for incidental or consequential damages
connection with, or arising out
Printed in the United States of
10
9876
5
of, the furnishing,
performance, or use of these programs.
America
4321
ISBN D-13-12DbSD-fl
Prentice-Hall International
(UK) Limited, London
Prentice-Hall of Australia Pty, Limited, Sydney
Prentice-Hall Canada, Inc., Toronto
Prentice-Hall Hispanoamericana, S.A.,
Mexico
Prentice-Hall of India Private Limited.
New
Delhi
Prentice-Hall of Japan, Inc., Tokyo
Simon
&
Schuster Asia Pte. Ltd., Singapore
Editora Prentice-Hall do Brasil, Ltda., Rio de Janeiro
2
1
CONTENTS
PREFACE
xvi
ABOUT THE AUTHORS AND CONTRIBUTORS
Part
I
Causes of Environmental Problems
1
1
THE NATURE AND SCOPE
OF ENVIRONMENTAL PROBLEMS, Gary
1
.
1.2
1
.3
What This Book
Some
Is
About
Systems
Interaction of
2
2
1.4
Environmental Disturbances
1.5
Public Awareness and Action
1.6
The Changing Role of Technology
1.7
3
1.6.1
Sustainable Development, 9
1.6.2
Preventive Technology, 10
7
9
Quantification of Environmental Issues
Problems
References
1
1
1
W. Heinke
1
Important Definitions
xviii
II
1
Contents
iv
2
POPULATION AND ECONOMIC GROWTH, Gary
Introduction
2.2
Population Growth
2.2.2
14
14
2.1
2.2.1
W. Heinke
15
The Nature of Population Growth, 15
in More Developed
Population Growth
and Less Developed Regions, 17
2.3
2.2.3
Population Parameters, 22
2.2.4
Population Projections and Methods, 25
2.2.5
Momentum
2.3.2
Measures of Economic Growth and
Technology of Production, 35
2.4.1
Definition of Urbanization,
2.4.2
Growth of
Cities,
2.5
Environmental Impact
2.6
The Dilemma of
References
Industrialization, 31
36
Urbanization
Problems
3
30
Industrialization
2.3.1
2.4
of World Population Growth, 29
37
38
40
Industrialization
and Urbanization
44
46
47
ENERGY GROWTH,
O. J. C.
Runnalls and Donald Mackay
3.1
Sources of Primary Energy
3.2
Current Consumption of Energy
3.3
Future Consumption and Availability of Energy Sources
3.4
Environmental Impacts of Energy Development
3.5
Environmental Impact Matrices
52
64
69
3.5.2
Environmental Impacts of Oil, 70
Environmental Impacts of Natural Gas, 72
3.5.3
Environmental Impacts of Coal, 73
3.5.4
Environmental Impacts of Hydroelectric Development, 75
Environmental Impacts of Nuclear Power, 76
3.5.1
3.5.5
3.6
50
Case Study: Canada's Energy Situation
Problems
References
82
84
78
60
49
1
v
Contents
4
NATURAL ENVIRONMENTAL HAZARDS, Ian Burton
85
4.1
Introduction
4.2
Classification and
Measurement of Natural Hazards
4.3
What
Hazard?
4.4
Extreme Events and Environmental Change
4.5
Impacts and Trends
4.6
Adjustments and Their Classification
4.6.1
4.7
is
a Natural
92
93
98
Preindustrial Approach, 98
98
Industrial Approach,
4.6.3
Postindustrial Approach, 101
4.6.4
Classification,
103
Theoretical Perspective: Future Possible Responses
Problems
104
107
References
5
86
89
4.6.2
A
85
1
08
HUMAN ENVIRONMENTAL DISTURBANCES,
F.
Kenneth Hare and Thomas
5.1.
Overview
5.2.
The Greenhouse
1
Hutchinson
1
Global Issues
5.3
C.
Effect and
1
Ozone Depletion:
13
5.2.1
Carbon Dioxide and Other Greenhouse Gases, 113
5.2.2
Effects of
5.2.3
The Ozone Depletion Problem, 119
5.2.4
Control Measures: The Climate Change Convention, 120
A
Acid Rain:
Greenhouse Gas Buildup. 115
Regional Issue
122
5.3.1
The Nature of the Problem, 122
5.3.2
Sources and Distribution of Acid Rain, 122
5.3.3
Effects of Acid Rain on Aquatic Systems, 123
of Acid Rain on Terrestrial Ecosystems, 129
on Groundwater, Materials,
5.3.4
Effects
5.3.5
Effects of Acid Rain
and
5.3.6
Buildings, 133
Remedial and Control Measures, 135
5.4
Lessons Learned
5.5
Epilogue
Problems
References
138
1
39
1
40
137
111
5
Contents
vi
Part 2
Scientific
6
Background
PHYSICS AND CHEMISTRY,
Gary W. Heinke and J. Glynn Henry
Introduction
6.2
Particle Dispersion
6.3
6.4
and
Colloidal Dispersions, 145
6.2.3
Methods of Expressing Particle Concentrations, 146
Settling of a Particle In a Fluid, 147
Distribution,
150
Solutions
and
150
6.3.1
Solutions
6.3.2
Methods of Expressing
6.3.3
Acid-Base Reactions, 158
Solubility,
the Composition of Solutions, 152
Gases, Gaseous Mixtures, and Gas Liquid Transfer
179
6.5.1
Concept of Material Balance, 179
6.5.2
Guidelines for Making Material Balances, 183
6.5.3
Examples of Material Balances, 184
Reaction Kinetics and Reactors
189
Reaction Kinetics, 189
6.6.2
Types of Reactors, 195
6.6.3
Determination of Reaction Rates, 203
6.6.4
Principles of Reactor Design, 205
Problems
208
References
2
1
ATMOSPHERIC SCIENCES,
F.
Kenneth Hare
216
7.1
Introduction
7.2
Basic Atmospheric Properties
217
7.2.1
Composition and Physical
7.2.2
Thermal and Electrical
Energy Outputs and Inputs
7.3.1
169
Gas Laws, 169
Gas Liquid Transfer, 175
Material Balances
6.6.1
7.3
143
Particle Size, Shape,
6.2.2
6.4.1
6.6
142
6.2.1
6.4.2
6.5
142
142
6.1
6.2.4
7
142
Solar Radiation, 221
217
219
State,
State,
221
216
1
Contents
7.4.
7.5.
7.6.
vii
Terrestrial Radiation.
7.3.3
Surface Radiation Balance, 224
7.3.4
Energy Use
Wind.
Stability,
7.4.
7.4.2
Motion of the Lower Atmosphere, 229
Turbulence and Stability, 232
Water
in the
7.5.1
Humidity and Precipitation, 235
7.5.2
The Hydrologic Cycle, 238
Climate
at the Surface,
228
and Turbulence
229
235
Atmosphere
242
7.6.1
World Distribution, 242
7.6.2
Climatic Variability, 245
7.6.3
The Climatic System, 246
7.6.4
Urban Climates, 247
Problems
250
252
References
8
223
7.3.2
MICROBIOLOGY AND EPIDEMIOLOGY, Gary
254
8.1
Introduction
8.2
Fundamentals of Microbiology
8.3
8.4
8.5
255
255
8.2.1
Classification of Microorganisms,
8.2.2
Bacteria,
8.2.3
Growth and Death of Bacteria, 260
Viruses, Algae, Fungi, and Protozoa, 265
8.2.4
W. Heinke
256
Applied Microbiology
271
and Solid Waste Microbiology, 271
8.3.1
Soil
8.3.2
Water and Wastewater Microbiology
8.3.3
and Indicator Organisms, 273
Atmospheric and Indoor Air Microbiology, 275
Epidemiology and Disease
and
8.4.1
Sanitation
8.4.2
Pathogens, 279
Health,
278
278
8.4.3
Waterborne Diseases and Water Quality, 283
8.4.4
Airborne Diseases, 288
8.4.5
Insect-
and Rodent-borne Diseases, 290
Noninfectious Diseases
8.5.1
292
Inorganic Contaminants. 293
8.5.2
Organic Contaminants, 297
8.5.3
Safe Limits, 298
254
Contents
viii
Problems
299
References
9
301
ECOLOGY, Thomas
9.1
Introductory Concepts
9.2
Energy Flow
9.2.1
9.2.2
in
303
Hutchinson
C.
303
Ecosystems
304
Estimates of Primary Production, 306
Comparison of Primary Productivity
World Ecosystems, 308
in Different
9.2.3
Energy Flow
Ecosystems beyond Primary Producers, 310
9.3
Food Chain and Trophic Levels
9.4
Nutrient Cycles
9.5
9.6
311
313
9.4.1
Carbon
9.4.2
Nitrogen Cycle. 314
9.4.3
Phosphorus Cycle, 316
Cycle,
313
Elements of Limnology
320
9.5.1
Quantity and Quality of Water, 321
9.5.2
Biotic Communities, 321
9.5.3
Light
9.5.4
Temperature and Vertical Stratification of Lakes, 324
in
Lakes, 322
326
Eutrophication
9.6.1
The Problem, 326
9.6.2
Physical Chemical and Biological Changes, 327
9.6.3
Control of Eutrophication, 328
9.6.4
Case Study: The Great Lakes, 329
9.6.5
A New
Problems
Challenge: Coastal Estuaries, 333
334
References
Part 3
in
335
337
Technology and Control
10 WATER RESOURCES,
J.
Glynn Henry
337
10.1
Introduction
10.2
Water Resources Management
10.2.1
Importance of Water. 338
10.2.2
Need for
10.2.3
Objectives
Control,
in
338
339
Water Resources Management, 340
337
Contents
10.3
10.4
ix
10.3.1
P rope rtU's of
10.3.2
Annual
10.3.3
Quantity of Water Available. 343
341
Water,
Precipitation.
342
10.3.4
Water Use, 347
10.3.5
Options for Meeting Water Demands, 349
10.3.6
Quantifying Ecological and Social Effects, 352
354
Planning Requirements
Purpose of Planning, 354
Stages in the Planning Process, 355
10.4.1
10.4.2
10.4.3
Formulation of the Study, 355
10.4.4
Evaluation of Alternatives and Their Effects. 357
10.4.5
Adoption of a Plan. 361
10.5
Legislative Controls
10.6
Political Influences
361
363
10.6.1
Pressure Groups, 363
10.6.2
Management
10.7
Future Challenges
10.8
Case Studies
Policies.
365
368
371
10.8.1
The Peripheral Canal. 371
10.8.2
The Occoquan Watershed, 376
Problems
379
References
381
11 WATER SUPPLY, Gary
W.
383
Introduction
11.2
Water Quantity Requirements
1
.4
384
11.2.1
Water Demand, 384
11.2.2
Fluctuations in Water Use, 386
Water Quality Requirements
389
11.3.1
Water Quality Standards, 389
11.3.2
Physical Characteristics, 390
1
1
383
Heinke
11.1
11.3
341
Technological Considerations
Chemical Characteristics, 392
1.3.3
Sources
of"
Water
392
11.4.1
Groundwater, 392
11.4.2
Surface Water, 394
11.4.3
Seawater, 395
6
Contents
x
11.4.4
1 1
.5
11.5.2
11.5.3
11.5.4
.6
11.7
Water Treatment Plants, 395
Removal of Particulate Matter, 397
Disinfection, 405
Removal of Dissolved Substances, 407
Transmission, Distribution, and Storage of Water
77.6.7
Transmission, 409
11.6.2
Distribution,
11.6.3
Storage, 411
420
12 WATER POLLUTION,
12.1
Introduction
12.2
Wastewater
12.5
12.6
415
41
References
12.4
J.
421
Glynn Henry
421
422
422
72.2.7
Constituents,
12.2.2
BOD
12.2.3
Municipal Wastewater, 427
12.2.4
Industrial Wastewater,
12.2.5
Stormwater, 428
Measurement, 425
428
Pollution of Receiving Waters
431
431
72.5.7
Effects of Pollutants,
12.3.2
Water Quality Requirements, 433
12.3.3
Need for
Pollution Control,
Wastewater Collection
435
436
12.4.1
Early Systems, 436
12.4.2
Present Systems, 436
12.4.3
Pollution
from Combined Sewer Overflows, 438
440
Principles of Wastewater Treatment
440
72.5.7
Effluent Requirements,
12.5.2
Treatment Processes, 440
12.5.3
Selection of Treatment Method,
Land-Based Treatment Methods
12.6.1
12.6.2
409
410
Future Needs and Development
Problems
12.3
395
Water Treatment Processes
77.5.7
1 1
Reclaimed Wastewater, 395
450
451
Land Application Systems, 451
Impoundment Systems, 452
1
Contents
12.7
xi
12.7.1
Suspended-Growth Systems, 457
12.7.2
Suspended Growth
12.7.3
Fixed Film Processes, 470
12.7.4
Sludge Processing, 474
12.7.5
Residuals Disposal, 479
12.7.6
12.8
12.9
12.10
12.8.1
Waterless Systems. 482
12.8.2
Septic Tanks. 482
12.8.3
Package
Plants,
483
Government/Public Role
in Pollution
12.9.1
Government
12.9.2
Direct Regulation, 485
12.9.3
Municipal Bylaws, 485
12.9.4
Public Involvement. 485
Trends
in
Subsidies.
Control
484
484
Controlling Water Pollution
486
487
49
13 AIR POLLUTION, William
13.3
461
481
On-Site Treatment Facilities
References
13.2
Kinetics.
Odor Problems, 481
Problems
13.1
456
Wastewater Treatment Plants
Air Pollution
in
J.
Moroz
Perspective
492
492
13.1.1
Introduction,
13.1.2
Air Pollution Episodes, 493
13.1.3
The Los Angeles Smog, 495
13. 1.4
Global and Regional Pollutants, 497
13. 1.5
The Principal Atmospheric Pollutants, 497
498
Effects of Air Pollution
1 3.2. 1
Health Effects, 498
13.2.2
Effects on Plants
13.2.3
Effects
13.2.4
Ambient Air Quality Standards, 503
and Animals, 502
on Materials and Services. 503
506
Sources of Air Pollution
13.3.1
Identifying Air Pollutants,
13.3.2
Natural Sources, 508
13.3.3
Domestic Sources, 510
506
13.3.4
Commercial Sources, 511
13.3.5
Agricultural Sources, 512
13.3.6
Industrial Sources,
13.3.7
Transportation-related Sources. 517
513
492
1
Contents
xii
13.4
13.5
Control of Air Pollution
521
13.4.1
Natural Cleansing of the Atmosphere, 521
13.4.2
Air Quality Control, 522
13.4.3
Particle Emission Control, 523
13.4.4
13.4.5
Gas Emission Control, 536
Flow Diagrams for Typical Recovery
13.4.6
Nitrogen Oxide Emission Control, 546
13.4.7
Ambient Air Quality Control by
Dilution,
Predicting Air Pollutant Concentrations
13.5.1
Air Pollution Meteorology, 548
13.5.2
Pollution Dispersion Models, 552
13.5.3
Plume Rise Models, 556
13.5.4
Processes,
538
547
548
Other Pollutant Dispersion Models and the Accuracy
of Predictions, 558
13.6
Air Pollution Control Costs
559
13.6.1
Coal-Fired Power Plant, 559
13.6.2
Automobile Emissions Control Costs, 560
Problems
560
References
14 SOLID WASTES,
565
567
14.1
Introduction
14.2
Characteristics of Solid Wastes
14.3
14.4
567
Glynn Henry
J.
14.2.1
What
14.2.2
Changes
14.2.3
Quantities, 571
14.2.4
Characteristics,
is
568
Solid Waste?, 568
in
Municipal Solid Waste, 569
572
Considerations in Solid Waste
Management
14.3.1
Protection of Public Health
14.3.2
Source Reduction, 578
14.3.3
Recycling,
14.3.4
Recovery of Energy, 580
14.4.
the Environment,
578
Collection Systems
14.4.2
and
581
Ease and Frequency of Pickup, 581
Collection Equipment, 582
14.4.3
Transfer Stations, 583
14.4.4
Rail Haul,
14.4.5
Route Selection, 585
584
577
577
Contents
14.5
14.6
14.7
14.8
xiii
Separation and Processing of
At-Source Separation and Processing, 586
14.5.2
Central Separation and Processing. 587
Conversion of
MSW
590
Incineration.
14.6.2
Composting, 595
14.6.3
Other Conversion Processes, 596
596
Landfilling
597
14.7.1
Design Criteria for Sanitary
14.7.2
Problems with Landfilling, 598
14.7.3
Leachate Generation Control and Treatment, 600
14.7.4
Gas Production, 608
14.8.3
610
610
Incineration, 610
14.8.4
Landfilling. 611
14.8.1
Legislation,
14.8.2
Collection,
Landfills,
609
Future Opportunities
612
617
15 HAZARDOUS WASTES,
J.
Glynn Henry and
0. J. C.
Runnalls
620
15.1
Introduction
15.2
Nuclear Wastes
622
15.2.1
Health and Environmental Effects, 622
15.2.2
Nuclear Wastes from Uranium Mining and Processing, 628
15.2.3
Nuclear Wastes from Power Reactors, 629
15.2.4
Management of Nuclear
15.2.5
Decommissioning of Nuclear Power Reactors, 636
Concluding Remarks, 636
15.2.6
15.5
590
14.6.1
References
15.4
586
14.5.1
Proble ms
15.3
MSW
Wastes, 631
636
Biomedical Wastes
15.3.1
Types of Waste, 636
15.3.2
Control of Biomedical Wastes, 637
Chemical Wastes
638
15.4.1
Need for
15.4.2
Environmental
Control,
638
Effects,
638
Identifying a Hazardous Waste
15.5.1
Methods, 640
15.5.2
United States Practice. 641
640
620
Contents
xiv
15.6
Hazardous Waste Management
15.6.1
15.7
15.8
15.9
15.10
Quantities of Hazardous Wastes Generated, 646
15.6.2
Components of a Hazardous Waste Management Plan, 649
15.6.3
Hazardous Waste Minimization, 650
Treatment and Disposal of Chemical Wastes
651
15.7.1
Treatment and Disposal by Industry; 651
15.7.2
Off-Site Hazardous Waste Treatment and Disposal, 653
Be
654
15.7.3
Quantities to
15.7.4
Practices in Western Europe
15.7.5
Practices in North America, 662
The Secure
Landfilled,
and
Function, 665
15.8.2
Acceptable Wastes, 665
15.8.3
Site Selection
15.8.4
Design and Construction, 667
15.8.5
Problems, 668
15.9.1
Combined
15.9.2
Separate Treatment, 670
Treatment,
Remediation
15.10.2
Kingdom, 656
and Approval, 666
Treatment and Disposal of Leachate
Site
the United
665
Landfill
15.8.1
15.10.1
670
670
671
Remedial Techniques, 673
Case Study: Remediation at the Seymour, Indiana,
Superfund
15.11
645
Future Challenges
Problems
Site,
676
677
679
References
682
16 ENVIRONMENTAL MANAGEMENT, R. Ted Munn,
Gary W. Heinke, and J. Glynn Henry
685
16.1
Introduction
16.2
Sustainable Development
16.3
Environmental Impact Assessment
686
687
687
16.3.1
Historical Perspective,
16.3.2
Elements of the Environmental Impact
Assessment Process, 689
16.3.3
Design of an Environmental Impact Assessment, 692
16.3.4
International ElAs,
16.3.5
Conclusions, 695
695
685
1
xv
Contents
16.3.6
Case Study: Atmospheric Component of an E1A
Power Station, 696
for a Coal-Fired
16.4
Pollution Control Strategies
700
16.4.
Economic Aspects, 700
16.4.2
Ambient and
16.4.3
Regulations for Controlling Environmental Pollution, 702
16.4.4
Case Study: Toxic Chemical Wastes
Effluent Standards, 701
—
The Niagara River Problem, 709
16.5
Environmental Ethics
16.5.1
715
Ethics in Society, 715
16.5.2
Environmental Consequences, 716
16.5.3
Responsibility for Environmental Degradation,
16.5.4
Ethical Theories
16.5.5
Ethical Problem Solving, 19
16.5.6
Changing
16.5.7
Conclusions, 724
Problems
References
and Codes of
Ethics,
717
718
Attitudes, 722
726
728
Appendix A
SYMBOLS, DIMENSIONS, AND UNITS
730
Appendix B
PHYSICAL PROPERTIES AND CONSTANTS
748
Appendix C
ABBREVIATIONS AND SYMBOLS
755
SPECIAL ENVIRONMENTAL PROBLEMS
758
Appendix
INDEX
D
761
PREFACE
This second edition of Environmental Science and Engineering
is,
like the first, intended
We
believe
and undergraduates
in envi-
for an introductory environmental course at the college or university level.
even more strongly now, than we did before,
that all engineers
ronmental studies need a course that deals quantitatively with environmental problems;
their causes, the scientific
and engineers
in
background needed
to
understand them and the role of scientists
solving them.
Improvements
to the
book,
updating of charts, graphs, tables and other
in addition to
on comments from instructors who used the
data, are based
and on the
text
results of ques-
who had
tionnaires given to second year engineering students at the University of Toronto
completed the course. Environmental Engineering
Instructors
I.
wanted more problems
number
(with solutions) so these have been increased by about one-third raising the total
of examples and problems to over 300.
Students liked the
first
edition (over
cover the complete text
rated
it
Very
Good
that trying to
•
that
•
that environmental ethics should be given greater emphasis.
more case
to Excellent) but felt
60-hour term was unrealistic
•
in a
studies should be included
These are sensible suggestions
in
75%
that instructors
may want
to consider.
The
specific
changes
content are outlined below.
In Part
1,
Causes of Environmental Problems (Chapters
changing role of technology has been added (Section
1
to 5) a discussion
1.6) that includes
on the
an introduction to
the concept of "preventive technology" as an alternative to traditional "end-of-pipe" solutions.
in his
W. H. Vanderburg
Alerting students to this idea has, for years, been the mission of
research and teaching at the University of Toronto. In subsequent chapters the most
recent information available has been incorporated into: population and
(2),
energy growth
turbances
(5).
(3), natural
environmental hazards (4) and
economic growth
human environmental
dis-
Several figures and sections in Chapters 4 through 5 are new, modified, or
replace ones that have been dropped.
Part 2, Scientific
Background (Chapters 6
to 9) is relatively
unchanged with
the ex-
ception of Chapter 7 which has been retitled as Atmospheric Sciences (from Climatology
and Meteorology), revised with recent data and parts of several sections deleted.
ter 8
In
Chap-
information about Cryptosporidium has been added.
Part 3,
Technology and Control (Chapters 10
revised part because techniques for the control and
resources are continually evolving.
to 16) has
been the most extensively
management of our
air,
water and land
Data on water consumption (Chapter 10) and drink-
ing water standards have been brought up to date.
Chapter
new information on land-based treatment methods,
12,
Water Pollution, contains
trickling filters, rotating biological
The efUse or Disposal
contactors and dual processes, because of renewed interest in these old processes.
fect of the
new
U.S.
EPA
regulations (40
CRF
Part
503 Standards
for the
of Sewage Sludge) on future biosolids management has also been considered.
xvi
A new
sec-
Preface
xvii
tion outlining the trends in controlling
water pollution has been added that covers the spec-
trum from source control through collection and treatment
13,
to effluent reuse.
In
Chapter
Air Pollution, most sections have been modified but others like Section 13.2 "Effects"
and 13.3 "Source" have also been expanded.
The chapter on Solid Wastes (14) has been completely reorganized with revised tanew material on source reduction, separation, recycling, recovery, composting
bles and
and incineration
Changes
Chapter
15.
(v\ith Detroit as
an example).
hazardous waste management have necessitated major revisions
in
New
to
There are new sections on:
tables have been added, old ones updated.
A
environmental effects, waste minimization, incineration, co-disposal and other topics.
summary of
the processes used at the 14b hazardous waste treatment facilities in the
US
has been included as well as an extensive discussion of site remediation with a superfund
Environmental Management, the
Indiana as a case study.
site in
final
chapter (16), covers
three topics: environmental impact assessment, pollution control strategies and environ-
The material
mental ethics.
A
ics, largely rewritten.
As
the other
hand
more
universal,
and the use of either of these systems
and science need
in
is
described.
from an educaAmericans on
at least
(SI) units.
Consequently we have adhered
practice adopted for the Inst edition of providing data in SI or
ers of engineering
case of environmental eth-
problems
Systeme International
favor the familiar U.S. units.
still
in the
measurement, Canadians have converted,
for the units of
tional standpoint, to the
each has been revised and
in
rational procedure for solving ethical
US
examples and problems.
units
to the
where appropriate
Students and practition
to be familiar with both systems, not just
because of
between countries but also because of the increasing acceptance of
"mutual recognition agreements" between professional bodies that allow, for example, en-
the trend to free-trade
gineers licensed
one jurisdiction
in
The success of
to practice in another without passing examinations.
the Hist edition, written
by 9 authors with advice from
leagues and assistance from graduate students, reveals that the book
been a credit
this
his
to those pioneering contributors.
second edition: Professor
Bill
We
also
want
Vanderburg for allowing us
to
filled
their col-
a need and has
recognize contributors to
to present,
however
briefly,
philosophy on preventive technology; Dr. John Newton for helping Ian Burton revise
Chapter 4 and providing new problems; Durga Prasad
ters in Parts
I
and
and
2
for updating
Chapter
X.
for proofreading
We
most of the chap-
are especially indebted to Kevin
Rich, a graduate student, tor his thorough literature survey and for the major role he
played
in the
extensive revisions of Part 3: namely Chapters 10. 12, 14. and \5 for Glynn
Henry and Chapters
I
1
and 16
lor
Gary Heinke.
Without his help the improvements
Environmental Science and Engineering would have been
far less
comprehensive.
to
Yuan
Cathy He deserves our gratitude lor accomplishing the difficult task of obtaining permission to use material from other sources. Our grateful thanks also to Diane McCartney who
was
solely responsible for the typing of the manuscript and
ness through
its
many
Finally, this
whose
efficiency and cheerful-
iterations are greatly appreciated.
second edition
is
dedicated to those Scientists and Engineers
who
serve
society and conserve the environment by solving environmental problems.
Toronto. Ontario
Canada
Glynn Henry
Gary W. Heinke
./.
ABOUT THE AUTHORS
AND CONTRIBUTORS -
GLYNN HENRY,
J.
Professor Emeritus of Civil Engineer-
ing at the University of Toronto and President of J.G.
Associates
Limited,
since 1973.
He was
Environmental
Consulting
Henry
Engineers
Director of the Environmental Engineer-
ing Laboratories at the university from 1974 to 1993 and
Chairman of
the
Environmental Engineering Program, a
collaborative undertaking by four graduate engineering de-
He
partments from 1977 to 1986.
is
a graduate in civil en-
gineering of Queen's University, Princeton University, and
the University of Toronto.
He
spent over twenty years in the
consulting engineering field as Principal and Director of R.V.
Anderson Associates, Toronto, before joining
His responsibilities included
activities
all
the university.
environmental and research
of the firm, including the design and construction
of over twenty major wastewater treatment projects. During
his
academic and consulting career he has taught 16 different
engineering and environmental courses and written over 120 technical publications and reports.
His current research activities include the biological solubilization, precipitation and extraction of
metals from municipal sludges, industrial wastes, and acid mine drainage.
fessional Engineer in Ontario, a Fellow of the
been a consultant
XVlll
to various agencies of the
He
is
a registered Pro-
Canadian Society for Civil Engineering and has
Canadian Government.
About The Authors and Contributors
GARY
W. HEINKE,
Professor of Civil Engineering
University of Toronto on the full-time staff since
at
the
1968.
In
1993 he began a 4-year term as Director of the Institute for
Environmental Studies, Hong Kong University of Science and
Technology. At the University of Toronto he was Dean of the
Faculty of Applied Science and Engineering from 1986 to 1993
and Chairman of the Department of Civil Engineering from
He
1974-1984.
is
a graduate of the University of Toronto in
engineering and of
civil
McMaster University
in
chemical en-
gineering, and spent ten years in consulting engineering in the
municipal and environmental held before joining the univer-
He
sity.
undergraduate course. Environmental En-
initiated the
gineering
I
at the
University of Toronto in 1975 and teaches
graduate courses in water and wastewater treatment processes.
His major research interests include cold-climate environmenengineering, physical-chemical treatment, and public health
tal
engineering.
His work has resulted
in
about 70 technical articles and reports.
He
is
a registered
Professional Engineer in Ontario and the Northwest Territories and a Fellow of; the Canadian So-
Hong Kong Institution of
Hong Kong Academy of Engineering
ciety for Civil Engineering, the
Engineers, the Canadian
Engineering, and the
Science.
all
Canada have
types of industries and levels of government in
ilar
organizations in
Hong Kong, China and Southeast
IAN BURTON,
Group,
Academy of
His consulting activities for
recently broadened to include sim-
Asia.
Director; Environmental Adaption Research
Atmospheric
Environmental
Service,
Environment
Canada, since 1990 and Senior Policy Advisor, Corporate Policy
1
96
Group. Environment Canada, from 1989
1
to
1
990
the
was Professor of Geography
to
1990.
at the
From
University
of Toronto, and Director of the Institute for Environmental
Studies from 1989 to 1984.
in
He
is
a graduate in geography and
water resources and resources management of the University
of Birmingham and the University of Chicago. Before joining
the University
o\'
Toronto, he taught environmental courses
at
Indiana. Queen's. Clark, and East Anglia Universities. His ma-
jor research interests include natural environmental hazards
and
their risk assessments.
He
has edited or contributed to ten
books and written over 100 scholarly papers,
reviews.
reports,
and
Appointments by Canadian governments, by several
universities,
and by the Ford Foundation on resource manage-
ment, on development of environmental programs, and on water resources planning have given
him
a broad perspective
on environmental problems
in
North America, Africa, and India.
consulting (inns have employed his expertise on Hood control matters.
Many
XX
About The Authors and Contributors
F.
KENNETH HARE,
from 1989
1980
until
1986
to
Chancellor
of Trent
at the
University of Toronto, and Director of
from 1974
the Institute for Environmental Studies
He
University
1995 was Provost of Trinity College from
to 1979.
a University Professor (Geography), the University of
is
He was educated
Toronto's highest academic honor.
University of
London (Kings College,
the
at the
London School of
Economics) and the University of Montreal.
He
holds ten
honorary doctorates, the Patterson and Massey Medals, the
Medal of the Royal Geographical Society and the
World Meteorological Society. He is a Fellow of the Royal Society of Canada and a Companion of the
Order of Canada. He has served on the National Research
Council (Canada), the National Environment Research CounPatron's
IMO
cil
(Washington, D.C.).
A
Prize of the
(U.K.), and as a Director of Resources for the Future, Inc.
lasting interest in his
wide range of atmospheric research has been the bio-
climatology of the boreal forest, as well as northern climatic variation.
energy and water balances
culation
of the
north
in
He
has studied surface
North America, the climatology of the desert margin, and the
polar stratosphere.
He
cir-
150 papers, books, and
has published about
monographs. He was Chairman of the Climate Program Board of Canada from 1974
to 1990,
is
World Climate Programme, and was responsible for the convening and editing of the
overview papers for the 1979 U.N. World Climate Conference, for which he wrote the paper on
active in the
climate variability and variation.
In 1977, he
was
the senior author of the background paper on
climate prepared for the U.N. Conference on Desertification.
THOMAS
HUTCHINSON,
C.
Environmental
Chair,
Resource Studies Program, Trent University since 1989. He
was Professor of Botany at the University of Toronto, from
1967-1989 and Chairman of the Department from 1976 to
1982. He was cross-appointed as Professor of Forestry and
had a long standing association with the
ronmental Studies.
He was educated
Manchester and the University of
at
Institute for Envi-
the University of
His major
Sheffield.
re-
search interests include studies of effects of acid rain and
heavy metals on
of
terrestrial
oil spills in the arctic
and aquatic ecosystems, impacts
and physiological mechanisms by
which plants have adapted
to pollution stress.
two books and has authored over 130
ports and
book
chapters.
He organized and
International Conference on
ment held
at
Toronto
in 1979,
in the Arctic.
Heavy metals
and acted as Chief Editor for the proceedings.
ecological stress has been sought by
He
has edited
scientific articles, re-
chaired the 1st
in the
Environ-
His knowledge of
WHO in Europe and by the Canadian Government for studies
About The Authors and Contributors
XXI
DONALD MACKAY,
lndustry-NSERC Chair
Professor and Chair of the Chemical
in
Environmental Modeling
He
University, Peterborough since 1995.
Emeritus
at
the University of Toronto
1967 after working
unit operations in
and environmental
Trent
which he joined
in
petrochemical industry. All his de-
in the
grees were obtained at the University of Glagow.
on
at
also Professor
is
He
lectures
Chemical Engineering and on energy
His major research interests
issues.
in-
clude the behavior of toxic substances in the environment, the
modeling of toxic organic substances
environment
in the
in-
cluding quantification of partitioning reactivity, persistence,
transport and accumulation.
His studies on
oil spills
on land
and water have taken him to the Canadian Arctic and East
Coast offshore regions.
He
has authored over
and reports, contributed chapters
articles
400
scientific
to several books, co-
edited a text on hydrocarbons in the environment and co-au-
He
thored five books on aspects of environmental science.
in
is
a registered Professional Engineer
Ontario and a Fellow of the Chemical Institute of Canada.
His expertise has been sought by
Canadian governments, the U.S. Environmental Protection Agency, the National Bureau of Standards and by
many
industrial organizations.
WILLIAM
*>'{
ates,
try
J.
MOROZ,
Principal of
W.
J.
Moroz Associ-
providing consulting services to government and indus-
on
air pollution
electric
monitoring and control for incineration,
power generation and
as Director of the
Assessments
industrial processes.
He
served
Department of Environmental Studies and
Ontario Hydro from 1980 to 1985, and Ad-
at
junct Professor in the Department of Mechanical Engineering
at the
sulting
He was a diMacLaren Limited, an environmental con-
University of Toronto from 1978-1986.
rector of
James
firm
F.
in
Toronto for ten years, a professor
at
the
University of Toronto and Director of the Center for Air En-
vironment Studies
eight years.
He
is
at the
Pennsylvania State University for
a graduate in mechanical engineering of
the University of Toronto and the University of Michigan.
His main research interests are
in air pollution.
He
has published about 40 technical papers,
is
a registered Professional Engineer in Ontario and Pennsylvania and a Fellow of the Royal Mete-
orological Society.
team
As an advisor to the Ontario Ministry of Health, he supervised
Commission study on transboundary pollution.
for an Intern, ional Joint
the
Canadian
1
About The Authors and Contributors
XXI
R.
TED MUNN,
ronmental Studies
cated
at
an Associate of the Institute for Envithe University of Toronto,
at
McMaster University
was edu-
(physics), the University of
Toronto (meteorology), and the University of Michigan
He was
(Civil Engineering).
previously Chief Scientist of
Branch of Environment Canada, and Head
of Environmental Programs, International Institute of Apthe Air Quality
plied
System Analysis (Laxenburg,
His accom-
Austria).
plishments include the design of a global environmental
A
monitoring system,
later
adopted as the basis for the
present world system, preparation of a
designing urban
studies,
and assisting
Sao Paulo,
for
in the
Brazil.
WHO
manual on
systems for epidemiological
air pollution
preparation of a Clean Air Act
His major research interests are
in
long-term environmental policy which includes the fields
of environmental impact assessment, cumulative environmental assessment, the design of early-
warning systems and the development of methods for multi-issue assessments. For 25 years he
was Editor-in-Chief of
the International Journal of
Boundary Layer Meteorology. He has written
seven books, authored more than 200 scientific papers and
is
a Fellow of the Royal Society of
Canada.
O.
JOHN C. RUNNALLS, Principal of
& Associates Limited and advisor to
O.J.C.
nails
and industry on nuclear power.
He was
Run-
governments
Professor of En-
ergy Studies in the Faculty of Applied Science and Engineering, University of Toronto from his appointment to
this
new Chair
this
important post because of his wide experience in en-
ergy
matters
in
1979
until 1989.
He was
selected for
gained in holding senior positions with
Atomic Energy of Canada Limited, Energy, Mines and Resources of the government of Canada, and Uranium Canada Limited.
From 1983
to
Chairman of the new Centre
the University of Toronto.
1989 he served also as
for Nuclear Engineering at
He
obtained
all his
engineering from the University of Toronto.
degrees in
His current
research interests include energy systems studies, uranium
supply and demand, nuclear fuel development, nuclear
materials technology, and radioactive waste management.
and technical papers and reports.
He
is
He
has published over 100 scientific
a registered Professional Engineer in Ontario, a Fellow
of the Royal Society of Canada, and a Fellow of the Canadian
Academy of
Engineering.
PART
1
Causes of Environmental Problems
CHAPTER
1
The Nature and Scope
of Environmental
Problems
Gary W. Heinke
1.1
WHAT
The
THIS
BOOK
objective of this
IS
ABOUT
book
is
to introduce engineering
and science students
disciplinary study of environmental problems: their causes,
and how we can control them.
•
why
to the inter-
they are of concern,
The book:
Provides a description of what
is
meant by environment and by environmental
systems
•
•
Gives information on the basic causes of environmental disturbances
Reviews or introduces basic
scientific
knowledge necessary
to
understand the
nature of environmental problems and to be able to quantify them
• Covers the current state of the technology of environmental control in
tion to water, air,
•
its
applica-
and land pollution problems
Exposes the considerable gaps
ing and controlling
many of
in
the
our current scientific knowledge of understand-
complex interactions between human
activities
and nature
•
Points out that there are
many environmental problems
that
could be eliminated or
reduced by the application of current technology but which are not dealt with
The Nature and Scope
because of society's lack of will to do
of Environmental
so, or in
many
Problems
Chapter
1
instances because of a lack
of resources to do so
Stresses the need
•
in,
and the opportunities
tion of wastes through technological
1.2
for,
avoiding or minimizing the crea-
changes and appropriate design methods
SOME IMPORTANT DEFINITIONS
Where
shown
they are
first
used
in
the book, definitions are introduced in block form, as
here, or printed in bold type.
Environment
is
the physical and biotic habitat which surrounds us; that
we can see, hear, touch,
System can be defined as "a
which
smell,
and
taste.
set or arrangement of things so related or
connected as
to form a unit or organic whole; as, a solar system,
system, supply system, the world or universe."
Pollution can be defined as an undesirable change
cal, or biological characteristics of
the
air,
affect the health, survival, or activities of
When
in
irrigation
the physical, chemi-
water, or land that can harmfully
humans
the goal of improving environmental quality
or other living organisms.
taken to be improving
is
human
word environment broadens to include all kinds of social, economic, and
cultural aspects. Such broadness is unworkable in many real situations and impractical
Our examination of environmental
in a textbook designed for a one-semester course.
well-being, the
problems
1.3
is
therefore limited by our definition of environment.
INTERACTION OF SYSTEMS
In Part 3,
we
water,
or land systems.
air,
deal with a
number of
Many
different environmental
problems associated with
of these problems will apply only within one of these
systems, justifying the breakdown into these categories.
Such a
classification
is
useful for easier comprehension of related problems within one system. Moreover,
also
it
is
sensible because, for managerial and administrative reasons, such subfields as air pollution,
water supply, wastewater disposal, and solid waste disposal are often dealt with
separately by governmental agencies.
Unfortunately,
many important environmental problems
water, or land system but involve interactions
the acid rain problem,
stemming from
are not confined to an
between systems.
A
current
air,
example
is
the emission of sulfur dioxide and nitrogen oxide
gases into the atmosphere from the stacks of generating stations, smelters, and automobile
exhausts.
Rainfall
These gases are then transported by
"washes them
out," creating acid rain,
which
air currents
is
over wide regions.
harmful to aquatic
life, forests,
Sec. 1.4
3
Environmental Disturbances
and agricultural crops.
Chapter
In
5,
two examples of
interaction
between systems
that
cause major environmental disturbances are presented: the buildup of atmospheric car-
bon dioxide,
a global problem,
and the acid rain problem, normally of a regional nature.
Whereas many environmental problems discussed
may
gional and
be dealt with effectively
overall water-air-land interaction standpoint
A
simple illustration of
an insecticide such as
this interaction is
DDT
is
now
chapters are local or re-
on a
shown
in
national, continental, or global basis.
Figure 1-1 and helps to explain
how
ubiquitous.
Figure 1-1
1.4
in later
at these levels, others must be viewed from an
Water-air-land interactions.
ENVIRONMENTAL DISTURBANCES
Many major improvements
to
our standard of living can be attributed to the application
of science and technology.
A
few examples are noted here.
•
The production of more and
•
The
Can you
think of others?
better quality food
creation of housing as protection from extremes of climate and as living
space
4
The Nature and Scope
means of
of Environmental
•
The building of
•
The invention of various systems of communication
•
The invention of machines
•
The supply of
•
The elimination of many
•
The elimination of most waterborne diseases
fast
and
safe water
reliable
Chapter
1
transportation
human
to replace
Problems
power
or animal
and the disposal of wastes
infectious diseases
in the
developed world through im-
proved water technology
The
•
availability of leisure time through greater productivity, providing the oppor-
tunity for cultural
and recreational
The protection from
•
activities
the worst effects of natural disasters such as floods, droughts,
earthquakes, and volcanic eruptions
With these improvements, however, have come disturbing side
arable land, disappearing forests, environmental pollution, and
to controls.
Many
effects originally considered to be just nuisances are
as potential threats to nature and to
harmony with
in
tially
effects,
humans.
such as
new organisms
now recognized
In an agrarian society, people lived essen-
nature, raising food, gathering firewood,
and making clothing
and tools from the land. The wastes from animals and humans were returned
as fertilizer.
problems of water, land, or
air pollution
to the soil
occurred (Figure
and the disposal of wastes had
to
be kept
in
balance with the changing
commu-
but no serious environmental problems were created.
The
to supply
Rome
thw
any,
if
For the small settlements that grew up, the supply of food, water, and other es-
1-2).
sentials
nity,
Few,
lost
resistant
cities
of ancient times, particularly those of the
(population about
1
Roman
Cloaca Maxima, the best known and one of the
many
centuries by those
who
built cities
and waste disposal were neglected, resulting
typhoid, and other waterborne diseases.
was not
earliest
sewers to be
in
cities
seems
built, are
to
ex-
have been
throughout Europe. Water supply
many outbreaks of
dysentery, cholera,
Until the middle of the nineteenth century,
it
realized that improper waste disposal polluted water supplies with disease-car-
rying organisms.
The
Industrial Revolution in nineteenth-century Britain, Europe,
North America aggravated the environmental problems since
ization with the industrialization.
were unable
it
air pollution
and
brought increased urban-
Both phenomena, urbanization and
were and are fundamental causes of water and
which
industrialization,
the cities of that time
to handle.
Rapid advances
in
of wastewater took place
technology for the treatment of water and the partial treatment
in the
developed countries over the next few decades. This led
to a dramatic decrease in the incidence of waterborne diseases.
the waste disposal cycle for an industrialized society.
the environment and thus pollute our water,
Following World War
boom
the ancient city of
million) with safe water from the Apefinine Mountains, and
amples of such systems. The municipal technology of ancient
forgotten for
Empire, had systems
The aqueducts supplying
water and to dispose of wastes.
II
air,
Note
Figure 1-3 illustrates
that all wastes discharge into
and land systems.
the industrialized countries experienced an
economic
fueled by a burgeoning population, advanced technology, and a rapid rise in en-
Sec. 1.4
Environmental Disturbances
o
/\
Physical Environment
Waste Producers
Waste Producer
Animal
Human
Waste Products
Processing
Human and
Animal Wastes
By-products of combustion
Crop Residues
Figure 1-2
ergy consumption.
Waste cycle
in
an agrarian society.
During the 1950s and 1960s
this activity significantly increased the
quantity of wastes discharged to the environment.
New
chemicals, including insecti-
cides and pesticides, used without sufficient testing for their environmental and health
effects, caused,
and continue
were introduced.
to cause,
enormous problems not anticipated when they
is worsening as the variety and amounts
Unfortunately, the problem
The Nature and Scope
of Environmental
Problems
Chapter
Waste Producers
Human and Animal Population
(
)
Physical Environment
Industry
Transportation
Energy
Waste Producer
Waste Products
Waterborne:
/\
Human and Animal Wastes
Industrial
Processing
and Commercial Wastes
Transportation Wastes
Domestic and
Airborne:
Industrial
Combustion Products
Open Burning Emissions
Industrial Gases and Particulates
Transportation Wastes
Domestic and Industrial Refuse
Sludges
Hazardous Wastes
Soilborne:
Figure 1-3
Waste cycle
in
an industrialized society.
1
Sec. 1.5
Awareness and Action
Public
7
of pollutants discharged to the environment increase inexorably while the capacity of
our
J?1.5
air.
and land systems
water,
wastes
to assimilate
is
limited.
PUBLIC AWARENESS AND ACTION
A
few voices began
to
Among
speak out about the new problems.
crusaders to heighten public awareness were Rachel Carson
Hardin
in his
Commons
fatuous essay The Tragedy of the
Population
Bomb
Commoner
in
Meadows
most effective
the
Spring (1962); G.
in Silent
(1968); Paul Ehrlich in The
Growth 1972); Barry
The End of Affluence
(1974): Barbara Ward and Rene Dubos in Only One Earth: The Care and Maintenance
of a Small Planet (1972); Erik R. Eckholm in Losing Ground (1976). The Picture of
1968); D. H.
(
The Limits
et al.. in
to
The Closing Circle (1971); Paul and Ann Ehrlich
Down
Health (1977). and
ment 1972-1982
(
1983).
Earth (1982); and Holdgate
to
(
in
The World Environ-
et al.. in
These are fascinating books, available
convenient paperback
in
form, that provide extremely important and stimulating reference reading.
Another reason why pollution came
pressed by
Goldman
to the forefront in the
United States was ex-
(1967):
Finally public attention
was directed
legislation
had been adopted
missionary
Goldman
among voters and
dumps were dirt)
it."
also stated
highway expansion, poverty control, urban renewal
was something that could evoke a similar
politicians alike.
One may
that
"there
is
to afford the luxury
There could be no Great Society
reason to believe that
of clean water and
air,
argue with this statement, but until recently
delegates of developing countries
ally did not
in
if
the
'
wealthy countries, able
about
mid-1960s
Pollution control
spirit
water, air and
the
Alter years of battle.
contend with most of the major challenges; medicare had
to
been approved, as well as programs
and education improvement.
By
to pollution tor unusual reasons.
our government had almost run out of domestic crusades to conduct.
at the
United Nations and
it
its
is
it
that
only the verj
can make a fuss
was often
cited by the
They gener-
agencies.
wish to heed advice from developed countries urging them "not
to
make our
mistakes over again by omitting pollution controls lor new industrial developments."
In
lution
most countries of the Western world, legislation to control many aspects of pol-
was introduced from
agency created
tal
Protection
in
1970
some
mains
to administer
Agency (EPA).
boards or agencies.
1960s to the
the late
All of the states followed
Similar developments occurred
extent in other parts of the world.
to be done.
ence on the
An
Human Environment
in
women's
in
1972
rights
in
.
the
In the
is
United States, the
called the
Environmen-
by establishing environmental
other Western countries and to
encouraging
The United Nations focused on
dealing with population, food,
1970s.
late
environmental program
start
was made,
but
problem by organizing
Stockholm.
desertification,
Later,
much
re-
a Confer-
U.N. conferences
human
settlements, sci-
ence and technology, and the Third World continued the emphasis on environmental
problems. The 1992 U.N. "Earth Summit" conference on environment and development
The Nature and Scope
8
in
of Environmental
Problems
Rio de Janeiro was attended by 182 countries and 102 heads of
lution
many key
warming,
issues, including global
forest protection,
Cairo was equally unproductive.
in
state: the largest ec-
ocean pol-
The 1994 U.N. "Population and De-
and population control, were not resolved.
velopment" conference
1
Expectations that global problems would be shared were
ological meeting ever held.
unrealized and
Chapter
This
is
not surprising and
points up the difficulty in reconciling the widely divergent views in different areas due
economic,
to distinct
social, religious,
and
These inconclusive con-
political conditions.
ferences, while discouraging to environmentalists, have brought environmental problems
to the attention of the world.
Public opinion
have to force political action.
At the moment people seem
most effective means we
after all, the
is,
away ahead of
to be
politi-
cians in their concern for the environment.
The enormous
by Eckholm
in
task faced by the Third
World countries was described graphically
1982:
Reasonably clean and
plentiful water, clean excreta-disposal facilities,
sanitary principles are together essential to better health;
yet
...
and the practice of
more than
half the people
Third World (excluding China) do not have reasonable access to safe water supplies;
in the
three out of four have
no adequate waste disposal
facilities,
not even a bucket latrine.
During the decades of the 1960s and 1970s the percentage of
the Third
dents with ready access to clean water and sanitary facilities rose significantly.
ulation soared, the absolute
numbers lacking these
necessities
climbed.
still
World
resi-
But as popAgainst
this
backdrop, the United Nations declared the 1980s the International Drinking Water Supply
and Sanitation Decade.
that
The hope
—known
to
be hollow even as
it
was announced
—was
Third World governments and international aid donors would drastically step up their
investments in water and sanitation, providing these goods to
all
by 1990.
Achieving
this
goal would require a three-fold to five-fold increase in expenditures over the 1979 invest-
ment
levels of
$6-7
billion, one-third
of which was provided as international
aid.
It
would
also require ending the urban bias in water and sanitation spending, wider use of simple
new forms of community involvement and education to ensure
new wells and latrines are better maintained than they have often been.
The needed funds sound large until they are compared to other global expenditures.
Meeting the financial needs of the Decade would require global spending of some $80 mil-
technologies, and pursuit of
that
lion a
day
—
this in a
world
$1.4 billion a day on arms.
to
genuine
water and sanitation has emerged
The
difficult
economic times of
priorities of the public
came
that lays out
No
the
and
its
more than $250 million
political
among
in 1992, the lessened threat of nuclear
become
unstable.
aid givers or
a day on cigarettes and
to providing universal access
most Third World governments.
the 1980s and early 1990s forced changes in the
governments.
major concerns, and understandably
the world have
commitment
Inflation,
so.
unemployment, and energy be-
With the breakup of the Soviet Union
war and increasing nationalism, many
strife is more evident.
Racial and religious
parts of
Crime,
education, medical care, family breakdown, and racial- and gender-related discrimination
compete
past and the
for politicians' attention.
enormous increases
caused huge financial
deficits for
The galloping
in the social costs
increases in energy costs of the
of welfare and unemployment have
governments of the developed world and have brought
The Changing Role
Sec. 1.6
many underdeveloped
of
countries to the brink of financial disaster.
nary statesmanship and wisdom
How
the next decade.
at
It
will take extraordi-
national and international levels to steer us through
high the priority for environmental improvement will be
difficult times remains to be seen.
the health
9
Technology
However,
it
seems clear
and safety aspects of toxic and hazardous wastes
that public
in
these
concerns about
will continue to increase for
a long time.
1.6
THE CHANGING ROLE OF TECHNOLOGY
As we move
problems
there
is
into the twenty-first century, the use of technology to solve environmental
will increase, but
will be applied in a different
it
evidence that the role
two important
oi'
technology
in
way
than before.
environmental matters
is
Already
changing
in
areas: sustainable development, dealing primarily with global problems,
and preventive technology, designed
to reduce the
environmental effects of processes,
operations, and products.
1.6.1 Sustainable
Development
The thought-provoking and widely acclaimed 1987 U.N. report "Our Common Future"
by the World Commission on Environment and Development (chaired by then Norwegian Prime Minister Gro Harlem Brundtland) provided the following definition:
Sustainable development is development that meets the needs of the
present without compromising the ability of future generations to meet their
own needs.
The concept of sustainable development has challenged
society to change from
its
destructive, exploitative philosophy to one that fosters long-term protection of the environ-
ment and
when
its
inhabitants.
For scientists and engineers
it
means
a shift
from past practices
technological developments were guided by efficiency, productivity, profitability,
and similar economic
criteria.
These remain
valid, but
added
to
them now
are concerns
about health and environmental impacts, resource and energy conservation, waste man-
agement and
social impacts such as public inconvenience,
unemployment and crime.
Overfertilizing the land, harvesting old growth forests, avoiding pollution controls
and similar harmful practices
to
solutions that can not continue.
meet the needs of a growing population, are short term
Ultimately global sustainable development will require
a stabilized world population living in a secure social and physical environment.
situation
is
led conditions.
ity
This
unlike the "steady-state" attainable in laboratory experiments under controlIf
global sustainability
and the natural adaptation of
Section 16.2 for further
is
achieved
it
will be
because of human ingenu-
living things to a continually
comments on
sustainable development).
changing world.
(See
10
The Nature and Scope
of Environmental
Problems
Chapter
1
1.6.2 Preventive Technology
Until the
mid-1970s and even today
Eastern Europe and
in
many underdeveloped coun-
economic and technological decisions for development were and are guided by
market and profit concerns, with little or no consideration for environmental and social
impacts. As these negative impacts became unaccecptable to society in the developed
countries, their governments passed laws that forced the adoption of pollution control
tries,
Treatment plants for industrial and municipal wastes, emission controls for
measures.
incinerator stacks, and safe landfills for solid waste disposal were created to control
water, and land pollution.
Treatment of wastes
streams, or for municipal effluents,
trol for the
the
past
20
continuation
years.
There are
of this
traditional
Many governments and
power everything
else
industries
becoming
the
often referred to as
end of
end of pipe or
air,
production
after the fact
the primary philosophy of pollution con-
powerful forces tending to drive societies into
still
approach, particularly
still
industrial
regard the
in
economy
the
developing world.
as the engine that
must
by circulating wealth, regardless of other consequences. Accord-
ing to their view, a society
ing or
is
The end-of-pipe treatment has been
treatment.
at
must make inevitable and
difficult
choices between remain-
internationally competitive and having a healthy environment,
between
productivity of labor and socially healthy workplaces and communities, between energy
production to keep the economic engine running and the risks associated with producing
this energy,
between affordable municipal taxes and
In other
difficult choices.
industrial
and
words,
all that
livable cities,
and a host of similar
appears possible to them
is
to use the resulting wealth to help
continue with
to
development and urbanization guided primarily by market and
profit motives,
pay for unavoidable environmental and social
costs.
But objections
to the traditional
approach, by those
who
favor a preventive strat-
They ask how processes, operations, and products of
egy, are growing.
the industrial
system can be redesigned or adjusted so as to avoid or minimize the production of
wastes
in the first place.
Rather than viewing
this
concept as one that will increase
costs and thus reduce profits, they see the larger implications of avoidance of after-thefact pollution control measures,
and possible cost savings
there.
They see
benefits in
the reductions in energy and maintenance costs, reductions in natural resource require-
ments, reduction or elimination of pollution control costs, reduced need for occupational
health and safety measures, because of cleaner production processes, reductions in the
risks flowing
from accidental
spills or discharges,
improved worker morale as they take
pride in their "green" products, and better acceptance by consumers of green products.
These
efforts,
by companies embracing
this
new
philosophy, can help reduce a nation's
expenses, such as health care and environmental costs, thus reducing deficits and tax
loads.
Preventive technology has had special appeal to industry because of the potential
economic
benefits
and the publicity gained from the extensive media coverage.
Partly excerpted
ventive Engineering.
from a forthcoming book by W. H. Vanderberg, The Ecology
(Publisher not selected)
oj
One of
Technology and Pre-
1
Chapter
Problems
1
the earliest and best
1
known examples of
preventive technology
is
the
3M
company's
"Pollution Prevention Pays Program," which involved product reformulation, process
modification, equipment redesign and recovery of waste products for reuse. Total savings by the
company were over $30
million in 3 years (Campbell and Glenn, 1982).
Similar conservation measures are being instituted by car manufacturers,
signing parts
and materials
to be reused
turers of refrigerators, stoves,
end of the useful
at the
life
of a
who
and other "white" appliances are beginning
are de-
Manufac-
car.
to design for
disassembly and reabsorption of materials into the production and consumption cycle.
Economists have begun
1.7
of these strategies.
to realize the potential
QUANTIFICATION OF ENVIRONMENTAL ISSUES
As
a future engineer or scientist,
effects of environmental
it
problems
express the perceived problem and
you
not sufficient for
is
to understand the causes
You must
terms only.
in qualitative
Many
potential solution in quantitative terms.
its
vironmental issues are very complex.
and
also be able to
en-
Often the problem can be divided into several
components, which can be analyzed by making material or mass balances on each component, which then leads to a solution for the total system.
and are introduced
effective tool in this regard
the
at
end of each chapter, and
System) units are used
Problems are provided
examples are used where appropriate
illustrative
AES
Both SI (Systeme International) and
throughout the book.
in
Material balances are a very
in later chapters.
(American Engineering
Conversion factors and practice problems are given
in the text.
Appendices A.I through A. 3.
PROBLEMS
1.1.
For each of the following products, indicate one of
mental effects on the environment or quality of
its
life:
beneficial uses
and one of
synthetic fertilizers,
detri-
its
DDT, phosphate
detergents. PC'Bs. antibiotics.
1.2.
List three pollution
each
is
a problem,
problems with which you are personally
and describe how nunc than one system
familiar.
(air.
Explain briefly
water, land)
is
why
involved
in
each ease.
1.3.
Study the table
ol contents of this
book and
list
those environmental problems that appear
to be missing.
1.4.
Find out which agencies are responsible lor environmental management of (a) water supply.
(b) water pollution, (c) air pollution, (d) solid wastes,
local
1.5.
1.6.
community
and
level, (2) the state or provincial level,
(e)
and
hazardous wastes
at
(I) the
(3) the federal level.
"Poor nations cannot afford the luxury of environmental control." Discuss.
You
are taking this course because
someone has decided
riculum or because you have decided to take
to get out of the
course
'
Make
a
list
of a
it
as
it
should be part of your core cur-
one of your
number of
electives.
What do you hope
points you can think of now.
At the
12
The Nature and Scope
end of the course, go back
changed? Have they been
1.7.
problem and review your
list.
Chapter
Problems
1
Have your expectations
satisfied?
Explain your interpretation of "sustainable development" as
downtown
population growth, (b) the
1.8.
to this
of Environmental
core of a
and
city,
might apply
it
to:
(a)
world
(c) a thriving agricultural area.
Select an industry where preventive technology as described in Section 1.6 could be used
(pulp and paper mill, a fast-food chain, furniture manufacturer, etc.) and
list
some of
the
benefits that the industry might realize.
1.9.
to
newspaper
mental problem.
that has
used preventive technology
article
(which should be attached) dealing with an environ-
Evaluate the validity of the report and the seriousness of the problems.
among
Consider,
other things,
•
Is
•
Can
•
How
•
What costs are involved, and who
why solid waste disposal by
it
local, regional, or global in nature?
it
be corrected?
long will
it
What
steps are necessary to
do
this?
take?
Explain
more than one
1.12.
your area
in
avoid or reduce waste production.
1.10. Discuss a current
1.11.
company
Prepare a 500- word essay on a
part of our
will provide the
funds?
sanitary landfill
is
environment
is
affected,
an environmental problem,
how
and by what.
Select a local environmental issue that you believe will be of increasing concern in the future
and write a brief of 500 words
to an appropriate political official.
The following
points
should be covered.
•
Statement of the source of the problem and
•
Reasons why the
•
Actions that should be taken soon under the headings (1) research. (2) environmental
situation
its
adverse effects.
may worsen, by how much, and when.
control and technology development, and (3) legislative needs
REFERENCES
Campbell, M.
E.,
and Glenn, W. M. Profit from Pollution Prevention. Toronto: Pollution Probe
Foundation, 1982.
Carson, R.
Silent Spring. Boston:
Commoner,
B. The Closing Circle.
Houghton
New
Mifflin, 1962.
York: Alfred A. Knopf, 1971;
New
York: Bantam, 1972.
Losing Ground: Environmental Stress and World Food Prospects.
Eckholm, E. P.
W. W. Norton, 1976.
Eckholm,
E.
P.
The Picture of Health: Environmental Sources of Disease.
New
New
York:
York: W. W. Nor-
ton, 1977.
Eckholm,
E.
P.
Down
to Earth:
Environment and
New
Human
Ehrlich,
P. R.
The Population Bomb.
Ehrlich,
P. R.
and Ehrlich, A. H. The End of Affluence.
Goldman, M.
I.,
Needs.
New
York: W. W. Norton, 1982.
York: Ballantine, 1968.
ed. Controlling Pollution:
New
York: Ballantine, 1974.
The Economics of a Cleaner America. Englewood
Cliffs, N.J.: Prentice Hall, 1967.
Hardin, G. "The Tragedy of the Commons." Science 162 (1968): 1243.
Holdgate, M. W., Kassas, M., and White, G.
cooly, 1983.
F.
The World Environment 1972-1982. Dublin: Ty-
Chapter
1
MEADOWS,
13
References
D. H..
Meadows,
D. L., Randers,
York: Universe Books. 1972;
United Nations
Common
Ward,
B. and
York: W.
New
J.,
and Behrens, W. W. The Limits to Growth.
New
York: Signet, 1972.
World Commission, World Commission on
Environment and Development. Our
Future. London: Oxford University Press, 1987.
Dlbos, R. Only One Earth: The Care and Maintenance of a Small Planet.
W. Norton.
1972.
Vanderberg, W. H. The Ecology of Technology and Preventive Engineering.
New
CHAPTER
2
Population and Economic Growth
Gary VU Heinke
2.1
INTRODUCTION
Until about
250 years ago, humanity existed
Any environmental
technology.
in relatively small
well within the environment's capacity to absorb them.
ries,
numbers with limited
disturbances caused by people were local and usually
However,
in the last
two centu-
four developments have occurred that have created environmental problems beyond
nature's assimilative capacity.
creating
earth.
Second,
nied by
First, there
has been an explosive growth of population,
enormous environmental pressures because of
new
this
the sheer
numbers of people on
growth, particularly in the developed countries, has been accompa-
industrial processes,
whose wastes have caused environmental damage.
Third, population growth and industrialization have given rise to urbanization
movement of people from small
settlements to cities and towns
—thus
environmental problems, because of the high density of people and industry.
the explosive growth of energy use
ularly since
World War
II,
and the introduction of many new products,
have added more environmental
—
the
increasing local
Finally,
partic-
stress.
a negative, and in some areas a disasThe economic successes and high standards
urban centers of the more developed nations have been accom-
These developments have generally had
trous,
impact on the physical environment.
of living of people
in the
panied by the consumption of natural resources such as water, timber, mineral deposits.
14
15
Population Growth
Sec. 2.2
The growing domestic and
energy supplies, and land.
industrial
demands
for
more
products and the corresponding depletion of natural resources cannot be sustained indef-
without severe environmental disorder.
initely
2.2
POPULATION GROWTH
The Nature of Population Growth
2.2.1
Population growth
is
often characterized as exponential; that
Mathematically,
this
P =
P =
/
e
increases (or de-
= PQ e
rt
(2.1)
future size of the population
current size of the population
tl
r
it
a unit period of time.
can be expressed as
P
where
is,
number over
creases) by a fixed percentage of the existing total
=
=
=
number of years
for the extrapolation
assumed constant growth
rate for
each of the
/
years (as a fraction)
base of natural logarithms
The growth rate r is usually expressed as a percent increase per year, or as the increase
in the number of people per 1000 population per year.
Currently, the world population
growth
rate
is
approximately 1.7% per year, or 17 people per year per 1000 population.
For any country, the growth
rate of a population
nents: births, deaths, immigration,
determined by four principal compo-
is
Growth
and emigration.
rate can be defined by the
equation
,=(h where
h. d,
i.
and e are the
tion,
The excess of
-
e)
(2.2)
immigration rate, and emigration rate,
numbers per 1000 population per year or percent per
births over deaths
is
referred to as the natural increase of popula-
and the difference between the number of immigrants and emigrants
migration.
time.
(i
birth rate, death rate,
respectively, expressed as either
year.
+
d)
Another useful basis
for expressing exponential
growth
is
is
called net
that of
doubling
Simply, the doubling time refers to the length of time necessary for the quantity
being considered to double
in size
when growing
proximation used to estimate doubling time
rdb *
where 7db
is
at
a constant growth rate
r.
An
ap-
is
the doubling time in years and
70
-
(2.3)
r
/•
is
the
growth
rate as a
percentage per
year.
Figure 2-1
1851 to 1990.
is
The
a graphical presentation of the population statistics for
illustration
shows
that the
Canada from
annual growth rate underwent tremendous
16
Population and Economic Growth
—
50
Rate
Birth
Birth
Chapter 2
Rate
Death Rate
Net Migration Rate
40
Growth Rate
c
o
3Q.
30
O
Q.
O)
c
To
X
lu
20
Dc
CO
<n
Z3
O
1
8.
°
CO
rr
x
Net Migration
Rate
o"
n10
i
*.
i
i
i
i
i
i
i
i
J
i
I
I
1851 1861 1871 1881 1891 1901 1911 1921 1931 1941 1951 1961 1971 1981 1991
Year
Figure 2-1
Birth
death
rate,
rate,
net
1851-1990, per 1000 population. Source:
migration,
and
growth
rate
Canada.
for
Ministry of Industry, Trade and
Commerce
(1989, 1992).
increases in the decade after 1986 and for 20 years after 1936.
crease in population prior to 1906
migrants caused the
jump
in the
was
declining,
growth
rate
it
is
Since the natural in-
evident that a high influx of im-
between 1986 and 1906.
On
the other
hand, the soaring growth rate between 1936 and 1956 was due to a high birth rate (the
postwar baby boom), as well as another period of high immigration.
increase in the growth rate
was
The most
recent
a result of high immigration.
Worldwide population trends have been outlined by Bramwell (1977):
Figure 2-2 gives a graphic picture of the growth of world population over the
lennia.
By
The population of
—
about 1650
nology
—
the world during the Christian Era
often referred to as the beginning of the
that population
last
two mil-
was some 300 million people.
modern
era of science and tech-
had increased to 500 million, but since then growth has been so
Sec. 2.2
17
Population Growth
t
1987
_0)
Q.
O
QL
1977-.
m
1959
4-
1929 /- 2
1850
A
The Urban
Explosion
—
1650
,
World Population
17^
1
"
AD
Figure 2-2
i
i
500
AD
World population. Source:
R. D. Bramwell.
I
1000
2000
1500
Towns and
Cities
(Gage Studies
Copyright 1977. Gage Educational Publishing Limited.
Series),
by
Reproduced
by permission of the publisher.
explosive that the population
in
most of humanity's time on earth
billion,
which
add a second
is
1983 stood
at
about 4.7
the estimated population in 1800.
billion,
billion.
—perhaps 500,000 years—
But
it
In other
words,
it
took
for the population to reach
only a further 30 years (to I960) to add a third billion, and a mere 15
years more (to 1975) to add a fourth billion, giving an estimated world population of 4
lion in 1975.
one
took only 130 years (to 1930) to
The world population has
therefore
grown
at rates
bil-
which have increased from
18
Population and Economic Growth
Chapter 2
annum
about two percent per thousand years during the Paleolithic Era to two percent per
mid-1950s
in the
David Suzuki,
—
a thousandfold increase.
renowned
a
product (GNP), energy use, pollution, or
portion to
At
one
is
the tube
1
we
1:00
1
1:59.
1
1:01 there are two, at
used bacteria to
anything else that grows steadily
The question
is
when
is
1
in pro-
medium
a test tube with a bacterial
So
in
at
1
it:
1:00
1:02 there are four, and so on until at 12:00,
The answer, of course, is at
that there was a space (or
the tube half full?
you were a bacterium, when would you become aware
population) problem? At
rium were
activist,
introduce one bacterial cell with a doubling time of one minute.
cell, at
full.
is
If
in fact
He suggested (1986) imagining
its size.
there
and environmental
geneticist
of continued exponential growth of population, gross national
illustrate the impossibility
to say to its
out of the tube
1
1:58, the tube
mates
at
1
1:55, "I
would be
l
-
—any sensible bacterium could see
be 5 minutes away from being
full, at
think we've got
it
1
1:57,
a space
i
full, etc.
If a bacte-
problem" he'd be laughed
was 97 percent empty Yet they'd only
!
full.
at 11:58, some enterprising cells got out, scoured the planet for new recame back with three test tubes of food.
That is a phenomenal find, three times the known supply! (Can you imagine how reassured we'd be if we made such an oil find?) How much time would that buy? At 12:00.
Suppose
sources, and
the
tube would be
first
full,
at
would be packed! Quadrupling
time
if
growth continued
at the
would be filled and at 12:02, all four
amount of food would only buy two more minutes of
12:01, the second
the
same
rate.
2.2.2 Population Growth in More Developed
and Less Developed Regions
It is
examine the rapid growth period of
instructive to
the last
250 years
growth between the more developed regions
(MDR)
more
in
Because of the very significant differences
as presented in Figure 2-3.
in
detail,
population
of the world and the less developed
regions (LDR), they are presented separately in the two portions of the graph.
On
large-scale division of the world into these two regions, net migration between them
small compared to overall growth and can be neglected.
rate in
each of the two regions
and the death
•
rate.
It
clear
is
is
in
rate
figure that the following have occurred:
MDR
from about 40 per annum per
about 1800 to less than 15 now.
In the less developed regions,
Birth rates have dropped dramatically in the
1000 population
Therefore, the overall growth
determined as the difference between the birth
from the
a
is
40 per annum per 1000 population continued until the
century but have dropped sharply in the last 25 years to about 25
the high birth rates of about
middle of
per
•
this
annum
Death
10 per
rates
per 1000 population.
have declined sharply
annum
minimum, and
in the
per 1000 population now.
that
aging population.
it
may
MDR
from about 35
in
There are suggestions
1800
that
to less than
about 10
is
a
increase slightly for the rest of this century because of
The same decline has occurred
in the
LDR,
but
it
started
much
19
Population Growth
Sec. 2.2
Birth
Rate
40
Wartime and
Postwar
Death Rate
Fluctuations
30
More Developed
Regions
20
c
o
™ 10
Growth Rate
Q.
O
Q.
O
O
O
CD
Q.
Birth
Rate
CD
n
40
/
t
Z
Death Rate
30
Tai-Ping Rebellion
and Indian Mutiny
Growth Rate
20
Wartime Losses
and Epidemics
Less Developed
Regions
\
10
1700
Figure 2-3
Growth
2000
1900
Year
1800
rate lor the
more developed and
less
developed regions. Source:
Data to 1050
from U.N. (1971); data after 1950 from U.N. (1081).
More Developed Regions (MDR)
Europe.
(CIS;
Commonwealth of Independent States
formerly USSR) United States, Can-
ada, Japan, temperate South America, Australia.
New
Zxaland
Less Developed Regions (LDR)
All other areas
20
Population and Economic Growth
near the beginning of this century, to reach levels approximately equal to
later,
those of the
Growth
•
Chapter 2
birth rate
now.
shown graphically
and death
200 years
tions,
MDR
rates,
at
rate lines,
in
annum
about 10 per
Figure 2-3 as the vertical distance between the
have stayed about the same
in the
such as the effects of war and postwar baby booms. There
important variations within the
the graph
shows very
prior to 1900 to over
many
clearly that
MDR for the
past
per 1000 population, but with important varia-
making up
nations
growth
rates
of course, also
are,
MDR.
the
For the
LDR,
have increased greatly from about 5
20 per annum per 1000 population
for
most of
this century.
The graph shows that it is decreasing death rates, and not increasing birth rates,
which are responsible for the population growth. Improved public health measures
and improved agricultural food production
in the less
developed regions have dra-
Consequently, historically high birth rates are no
matically lowered the death rate.
longer offset by high death rates, and the result
is
sharply increased growth rates.
more developed regions, declining death rates have been experienced with the
advent of improvements in sanitation and medicine in the nineteenth century. SubIn
sequently, there has been a lowering of birth rates brought about in part by urbanization.
after
In the less developed regions, the decrease in birth rates did not start until
World War
The
II.
have been successful
30
efforts of the past
decreasing the birth
rate is
now approximately
shown
as being about parallel in the figure.
It is
tion
in
40 years
to
rate.
The
equal to the rate of decrease in the death
in the
trates the point:
MDR
and
LDR
countries in order to appreciate the trends in world
of every 10 people living today, four
less
developed countries, China and India.
less
developed regions.
Tables 2-1 and 2-2 indicate that about
outweighed by growth
Declines
One simple
of the world's population lives in the
developed regions and are likely
a constant growth rate of about 1.6% in the period 1985-2010.
many
in
South and Central America, are
standard of living, which
pital,
is
much lower
house, road, water treatment
to be duplicated within the next
these projections
worn out or
do not account
fact illus-
one or the other of the two
more developed regions' growth
in the
rates in the less
75%
live in
socioeconomic implications of a constant 2.5% growth
such as
graphically
rate,
important to understand the difference in the situation with regard to popula-
growth
population growth and the related socioeconomic implications.
at
campaigns
in birth control
rate of decrease in the birth
rate for less
rate
to
have been
be balanced
In absolute terms the
developed countries,
that just to maintain their present
than in developed countries, every school, hos-
facility,
28 years.
market, power plant, and so on, would have
The phrase absolute terms
is
used because
for such things as the replacement of services that have
the increasing per capita
many
of
and technology necessary just
to
consumption of goods and services.
the less developed regions the scale of industrialization
In
maintain the present standards for the rapidly increasing population simply does not exist.
Slowing the growth
rate in
well-being of the population.
such countries
is
of paramount importance to the future
S
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21
22
Population and Economic Growth
In the
most recent population trends there are indications of a
the growth rate in
ever,
it
LDRs
will require
some
Chapter 2
slight decrease in
and, consequently, in the world population growth rate.
How-
years to determine whether this decrease will be a lasting one.
The average world growth
rate in
2000
estimated at 1.6%.
is
2.2.3 Population Parameters
A
few of the more frequently used population parameters are as follows:
Age
structure refers to the distribution
of
ages
in
Population pyramid is a graphical representation
where male population is plotted on the negative
axis and female population is shown on the other
as percent
of total population occurring within
Fertility
a measure of the
is
Total fertility rate
her
is
number
number
the
of
the population.
of
age and sex
distribution
(left)
side of the horizontal
side.
Figures are indicated
each age group.
annual
live births in
of children the
average
a population.
woman has
during
lifetime.
Replacement growth occurs when
the total
fertility
Zero population growth occurs when the death
and the net migration is zero.
rate
about
is
2.1.
rate equals the birth rate
Figure 2-4 shows three population pyramids for the 1974 populations of Mexico,
the United States,
off
on the
and Sweden. As can be seen, a typical pyramid has the ages marked
vertical axis, with
age zero
at the origin.
The male population
the negative (left) side of the horizontal axis, while the female population
the positive (right) side.
lation occurring within
trast to
regions.
side,
showing
total
The
scaling on the horizontal axis
each age classification.
numbers,
The pyramid
itself is
facilitates
is in
is
is
plotted on
shown on
percent of total popu-
This percentage type of scaling, in con-
comparison between two or more countries or
composed of
18 horizontal bars
on the male and female
with each bar representing five-year intervals.
The leftmost pyramid
population, that of Mexico.
in the figure
shows
the age structure for a rapidly
This pyramid, with sharply tapering sides,
population with a large base of young people.
is
growing
typical of a
Rapid growth will occur as each
large,
young age group moves up the pyramid into its reproductive years. In sharp contrast is
Sweden's pyramid, on the right, which is almost straight-sided until the oldest age
groups are reached. Sweden's base age groups are no larger than those above it, implying that each reproductive generation has simply been replacing itself for so long that
we do not witness a swelling in the numbers of Sweden's young people. Sweden's pyramid is characteristic of a no-growth population. The U.S. pyramid in the middle represents a population whose stage of development is between that of Mexico and
Sweden. Many people in the United States are in their early reproductive years as a result of the growing up of the children of the World War II baby boom. Note, however,
1
23
Population Growth
Sec. 2.2
Rapid Growth
Slow Growth
(Mexico)
(United States)
No Growth
Years
Age
Before
85+
80-84
75-79
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
Female
Male
m
J
L
I
j
i
Female
5-9
0-4
j
1
890
1890-94
1895-99
1900-04
1905-09
1910-14
1915-19
1920-24
1925-29
1930-34
1935-39
1940-44
1945-49
1950-54
1955-59
1960-64
1965-69
1970-74
15- 19
10- 14
8642 02468
(Sweden)
of Birth
4
2
2
4
ll
1
i
i
4
6
6
Female
T=P?
,
6
4
Male
2
2
4
6
Percent of Population
Percent of Population
Percent of Population
Median Age 16.3
Median Age 28.6
Median Age 35
Figure 2-4
States,
Population pyramids (age structure) for the
and Sweden. Source:
Zito
(
1974 population of Mexico, the United
1979).
base age classifications are actually shrinking in size, thus making the U.S.
pyramid typical of a slow-growth population. Figure 2-5 shows the population pyramid
that the
for the world's population
in
further social, economic,
MDRs
1985 and 2025, shown separately for the
LDRs. The disproportionate growth between
these
two regions and
and environmental pressures
in the
and
the implications for
LDRs
are
emphasized by
this graph.
Fertility
is
The
time.
number of annual live births in a population, whereas
number of children the average woman has during her lifein the United States was about seven 200 years ago and has
a measure of the
the total fertility rate
is
the
total fertility rate
steadily fallen to about
two now.
Total fertility rates for selected countries and regions
of the world are listed in Table 2-3.
Replacement Growth occurs
if
at a fertility rate
of about
2.1.
One might
expect that
each couple has two children, the couples are just replacing themselves and no growth
will
occur
First, for
in the
population.
In fact,
however,
this
is
normally not
most countries the population age distribution
is
so, for
tering their reproductive years than are leaving them. Therefore, even
rate
—
would
tion
that
still
is,
the average
be more
would continue
number of children
women
to
in their fertile
grow
quires the birth of just over
for each
two reasons.
such that more people are en-
woman
if
the total fertility
— were exactly two,
there
years than before, and therefore the popula-
for several generations.
Second, replacement growth
two children per woman, because some females
re-
will die
24
Population and Economic Growth
I
I
Population
IB Increase
Years
of
in
to
(Millions)
2025
Years
Age
Males
Females
Males
1985
1985
Chapter 2
of
Age
Jipi Females
?5-
300
240
180
120
60
60
120
180
240
300
PRB
60
MDR
LDR
Figure 2-5
60
Age-gender composition of world population, 1985 and 2025. Source:
(1988).
TABLE
2-3 TOTAL FERTILITY RATES
FOR SELECTED COUNTRIES AND REGIONS
Country/region
World total
More developed
Total fertility rate, 1992
3.3
regions
1.9
Less developed regions
3.8
Africa
6.1
East Asia
2.1
China
2.2
Japan
1.5
South Asia
3.4
Indonesia
3.0
Philippines
4.1
Latin America
3.4
6.0
Haiti
Dominican Republic
North America
3.6
2.0
Canada
1.8
United States
2.0
Europe
Sweden
Germany
CIS (former USSR)
2.2
Oceania
2.6
Source:
PRB
(1992).
1.6
2.1
1.4
Sec. 2.2
25
Population Growth
will be unable to
have children, some
in general, there are slightly
smaller percentages
some
before they reach their reproductive years,
choose not
will
to
have children, and
of female children than male children.
growth
will vary
from country
to country
The exact number required
for replacement
depending on the age distribution of the
dren and the percentage of male and female children.
From Table
2-3,
chil-
one can see
that
such countries as the United States, Canada, Germany, and Japan are below replacement
growth, the CIS
is
near replacement growth, and countries such as Haiti, Indonesia, and
most African countries are above replacement growth.
Zero population growth
a term that
is
Neglecting
frequently misunderstood.
is
any immigration or emigration from a country, zero population growth occurs only
when
rates
Replacement growth does not mean zero
the death rate equals the birth rate.
growth
reasons discussed earlier, unless replacement growth
in the population, for the
have occurred for a long time.
2.2.4 Population Projections and Methods
Population projections are needed by an engineer or scientist for the design of
for a
community, region, or nation and
facilities
which
to control future environmental impacts in
population growth will play a major role. The length of time in the future for which estimates need to be
made may be
short term
(
up
to 10 years) for the kinds of facilities
can be extended relatively easily after the end of the period, or long term (up to 50
that
years) for those facilities that
would be very costly
to duplicate or
extend
in the
near fu-
ture.
Both short- and long-term population projections depend heavily on past records.
They
also
depend heavily on
the accuracy of predictions for future
growth of the com-
mercial and industrial activity of a region, which can have an important effect on the net
migration to the region.
tant influences
ple's
attitudes
Many
other factors are difficult to assess but can have impor-
on population growth and long-term projections.
still
requires a lot of crystal-ball gazing! Nevertheless, population planners
have learned much
in
recent years, and engineers can
draw on
their help to obtain the
best possible population forecasts for projects under consideration.
ties
and regions the
However,
it
is
local planning
in
In
commissioner's office will provide
important for engineers to
sumptions behind the forecasts
the predictions.
of these are peo-
The "science" of population
technological developments, and government attitudes.
projection
Some
toward having children, economic conditions, wars, natural disasters,
know something about
most communithis information.
the data
and the
as-
order to appreciate the possibility of fluctuations in
Often, the projections are given as two or more alternative estimates,
such as high, medium, or low projections.
It
is
wise to
to build into the design of facilities flexibility for
stantially higher or
treat estimates
changes
in
with caution and
case actual growth
is
sub-
lower than past projections.
Graphical methods.
to estimate future population.
Graphical projections of past population data are
Projections can be
by arithmetic or geometric extension, or by
least
made by simple
squares regression
made
graphical extension,
lines.
Sometimes
it
26
is
Population and Economic Growth
Chapter 2
helpful to use growth curves of similar but larger communities for comparison in
making
Graphical methods are simple to use and easy to ap-
the graphical extension.
ply; however, the results
from different estimators may
vary,
depending on the experi-
ence of the persons making the projection.
Mathematical methods.
assumed
tial
to follow a
or follow one of the
various situations.
curve, as
shown
in
For mathematical methods, population growth
mathematical relationship.
many mathematical formulations
A common
method
to use
is
is
Growth may be arithmetic or exponenthat
have been proposed for
an expression that describes an "S"
Figure 2-6.
Ceiling
Decreasing Rate
of
Growth
Point of Inflection
Q.
O
Q.
Increasing Rate of Growth
Years
Figure 2-6
Component method.
complex of
the three, but
ture characteristics
this projection
it
S-shaped population growth curve.
The component method of
projection
is
the
most
usually yields a very detailed picture of a population's fu-
and numbers.
Fertility
and mortality trends are taken into account
in
by breaking down the base population into age and gender components
(usually five-year groupings) and then applying age- and gender-specific fertility and
mortality rates to each group.
lated as well,
The
effects of immigration
and emigration can be calcu-
on the assumption of a future number of migrants. These migrants should
then be subdivided into age and gender components so that appropriate
mortality assumptions can be applied to
them
The choice of method of projecting population
or lack thereof of past population data.
fertility
and
also.
When
often depends on the completeness
only total numbers are available and no
27
Population Growth
Sec. 2.2
information on birth and death rates or on immigration and emigration rates exists, a
simple graphical or mathematical projection
the only choice.
is
By
contrast,
when
suf-
component method can be employed, including the use of
a sophisticated computer. A more detailed discussion of population projections is beyond the scope of this book. However, Demographic Techniques is a good book on the
ficient data are available, the
subject iPellard et
Example
al..
I
u 74).
2.1
Estimate the population of the town of Waterville
past population data projected
Year
in the
sear 2000 based on the following
beyond 1983.
1900
1910
1920
1930
1940
1950
1960
1970
1980
1983
10.24(1
12.150
18,430
2d.2!0
22.480
32.410
45.050
51.200
54,030
54,800
Midyear
population
The town has been
actively trying to increase
industrial
its
growth but has had only limited
success over the past 10 years.
Solution
tions
A
graph of the past population data
between the 10-year census
is
made
(Figure 2-7).
by an assumed linear change between censuses.
One can
of the changes, based on experience elsewhere: the drop
pression of the 1930s, probably caused by people
the rapid growth in the
down
in
Since actual popula-
one can connect the data points
intervals are not available,
speculate on the reasons for
in
moving away because of
a lack of jobs;
war and postwar boom periods of the 1940s and 1950s; and
growth during the
1970s.
difficult
What about
some
population during the Great De-
a slow
the period to the year 2000.'
The
70,000
High 66,200
60,000
Medium 59,165
Low 54,900
50,000
40,000
30,000
- 20,000
10,000
1900
10,000
1920
1940
1960
Year
Figure 2-7
1980
2000
28
Population and Economic Growth
Chapter 2
statement of the problem specifically mentions recent attempts, with only limited success,
to attract industry.
jobs through
new
Will the 1980s be a repeat of the 1930s? Will the drive to achieve more
industries succeed?
Could the
growth
rate of
coming years be
in the
as
high as during the 1940-1960 rapid growth period?
Without further information on the particular town and region,
answer these questions
make more
In fact,
specifically.
it
is
not possible to
no one, even with extensive information, can
The
than an informed, educated guess.
best
we can do
are the following pro-
jections.
•
High projection. Assume current growth
rates will continue for 5 years, followed
maximum
an increasing rate of about two-thirds of the
growth
rate to the year 2000.
54,800
,io«n
iofi^
(1980-1983)=
-
54,030
45,050-32,410
,m™
,QAm
(1950-1960)=
—
High population
•
Medium
projection.
Medium
•
Low
projection.
in
2000
=
54,800
+
5 x 257
=
54.800
+
1285
+
=
.__
257 per year
=
1264 per year
+
12 x
10.1 12
]
=
x 1264
66.187
=
66,200
Current growth rates will continue for the next 17 years.
population in 2000
There
=
54,800
will be a population
years, followed by a slow
growth
at
50 per
+
17 x 257
=
59,165
drop of 100 per year over the next 5
year.
The
large drop of the 1930s will
not be repeated because of the existence of social assistance programs keeping
ployed people
Low
Thus
by
previously experienced
in the
population
unem-
community.
in
2000
=
54,800
-5x100+12x50 =
the estimated range of population growth
is
54,900
from
high of 66,200
present population of 54,800 to
medium
of 59,165
low of 54,900
or a range of
that
would
1
fall
1,300, or about
20%
of the size of the present population.
under purview of the town engineer,
about the following:
3300 housing
units
20 miles (32 km) of new roads
20 miles (32 km) of sewers and water mains
Extensions to the water treatment plant
Extensions to the waste treatment plant
Extensions to the hospital
this
In terms of
works
range of population translates into
29
Population Growth
Sec. 2.2
A new
high school
new
Several
A
public schools
regional shopping center
Several neighborhood shopping centers
Three new
Two new
fire halls
libraries
Most important,
the growth or lack of growth will have important financial im-
town
pacts on the revenue of the
for capital expenditures and for operating and mainte-
Therefore, what appears to be a small extension of the upper
nance expenditures.
right-hand corner of the population graph has very important consequences for the future of the town.
2.2.5
A
Momentum
some very thought-provoking population
presentation of
made by
T. Frejka in
growth.
when
a
Growth
of World Population
1973
is
projections for the world
a fitting end to the discussion of material on population
projections correspond to various assumptions regarding the year
Frejka's
worldwide
replacement
level of
fertility
would be reached. As shown
in
Figure
2-8. the two lowest projections are based on replacement growth being reached by the
early 1970s or early 1980s, with a corresponding stabilization of world population at 5.7
billion or 6.5 billion, respectively, about
100 years afterward.
now
is
It
apparent that
strict
two lowest projections will be exceeded. This is because, while the need to rethe birth rate seems obvious to the social planner, population growth has been fos-
tered
by
these
still
social attitudes that
had validity
Two hundred
valid today.
in the past and, in
years ago, a
woman was
some
parts of the world, are
expected to have four to seven
children to ensure the community's survival: half of these children
reaching
and many
fertility,
women
died during childbirth.
terns did not immediately alter with the falling death rate.
social attitudes
begun
to change.
would die before
But these childrearing patonly recently have
In fact,
Furthermore, the lack of social welfare legislation
developing countries influences social attitudes toward having children:
where few people can look forward
and shelter them
in their
to a pension,
people expect their children to support
2020-2025
about 10
down,
2010.
lines
billion.
To
will be
feed, house, clothe,
billion after re-
about twice as
and employ them
conceivable by the
level is
the
year
2000-2005 and
stabilized world population
This information has staggering implications.
than 100 years from now there
are today.
15.1
However, with world growth appear-
a worldwide replacement fertility
Thus Frejka's projection between
seems most likely, yet it would result in a
ing to be slowing
year 2000 to
of
achieved, by the year 2040.
fertility is
in
a country
old age.
Frejka's highest projection has world population at about
placement
in
many people
will be a
It
in
means
that in less
the world as there
monumental
task.
30
Population and Economic Growth
Chapter 2
16
2040-2045
2020-2025
w
c
o
2000-2005
m
c
o
Q.
O
1980-1985
a.
1970-1975
Figure 2-8
Momentum
in
population growth. Source:
±
1970
"The Prospects
2000
2050
2100
2150
T. Frejka,
for a Stationary
World
Population," Scientific American,
Year
2.3
world
March
1973.
INDUSTRIALIZATION
For most people, the word industrialization
is
connected historically to the Industrial
Revolution of the eighteenth and nineteenth centuries, with
It
is,
ing
however, a continuing phenomenon, which
many of
is still
the less developed regions of the world.
ceived as bringing higher standards of living,
it
is
its
origin in Great Britain.
spreading globally,
now
Because industrialization
a goal pursued by
all
affectis
per-
nations.
The Industrial Revolution began in Great Britain during the eighteenth century. It
was distinguished by numerous technological inventions, including, most notably, the
spinning jenny and the steam engine. Such traditional trades as sewing, flour milling,
Sec. 2.3
31
Industrialization
The
brewing, and shoemaking were transformed into mechanized ventures.
vance was
enabled mines
ery for
thermodynamic conversion of heat energy
in the
many
pumped
be
to
dry. coal
and ore
to
This
be moved long distances, and machin-
human
tasks to operate almost free of
real ad-
into kinetic energy.
or animal motive power.
was a higher
The higher wages generated increased purchasing power. This meant that people were making more demands for products, resulting in increased resource consumption and the output of more airborne and waterborne
effluents from factories.
Industrialization was also accelerated in the more developed
The ultimate
benefit of the Industrial Revolution for the individual
standard of living through higher wages.
nations by exploitation
o\'
cheap
and the resources of
labor, land,
less
developed regions
of the world.
2.3.1 Measures of Economic Growth
and Industrialization
The most w idely used economic
indicator of a country's standard of living
is
the gross
national product (GNP).
Gross national product (GNP) is the sum of
expenditures on goods and services within a
all
personal and governmental
country, including the value of
net exports.
Gross environmental improvement (GEI)
is
reforestation or pollution control
GNP
is,
but also what
it
GNP
is
in
not.
mind,
The
country's economic health and well-being, nor does
in a nation.
sumed
merely totaled
to yield this
can
it
in
p.
not disclosed by the
one economic
viding an incomplete picture.
(Treshow. 1976,
is
The
of natural resources.
pletion and environmental
GNP
it
important to recognize not
does not by
statistic,
288) claims
American auto
all
more wastes from
in
In
to
is
very widely used and useful, but pro-
an economic indicator.
that in
modern technological
Economist John Hardesty
societies
components of
linked to environmental destruction, and that a high
industry,
which accounts
steel production,
and further degradation
indicate the ex-
it
goods and services
Several people have argued for inclusion of resource de-
damages
some way be
GNP, nor does
dollar value of
An example
for possibly
10%
greater production of automobiles will help to maintain a growing
in
itself reflect the
reveal the distribution of wealth
probably also reflects a high rate of resource depletion.
the North
is
GNP
Also, whether the environmental impacts of the goods and services con-
are beneficial or harmful
tent of the depletion
the
that
money spent on
measures.
With the preceding definition of
only what the
GNP
a component of the
includes the costs of environmental improvements, such as
more
GNP
of the
GNP
GNP.
is
A
but will result
toxic gases released from gasoline engines,
our landscape from highways, parking
response to the need to relate the
GNP
Hardesty cites
lots,
and scrap yards.
quantitatively to environmental
damage and
32
Population and Economic Growth
resource depletion, a
among
these
number of
alternatives to the
GNP
have been suggested.
the statistic called the gross environmental
is
can be used
The wide gap
in
in
GNP
GNP
on a per capita
basis.
Figure 2-9 illustrates the wide range in per capita
in various regions of the world and relates this
GNP
high per capita
in a
more developed
becomes evident if we ex-
the rich nations of the
regions and the poor nations of the less developed regions
press the
Other
to the ex-
GNP
place of or in conjunction with the
economic growth between
Notable
improvement (GEI).
proposed alternatives that include environmental effects have not been refined
tent that they
Chapter 2
GNP
to population
growth
rate.
4.5
Kuwait
4D Saudi Arabia
00
oo
3.5Nigeria
CT>
I
o
oo
3-
en
2.5
- D Ethiopia
D Philippines
Mexico, Brazil
o
D India
O
c
o
a
CL
O
World
1.5
Q_
China
"nj
c
c
1
-
D U.S.A.
DC.I.S.
Canada
D
<
CD
CD
0.5
Japan
-
<5
>
<
United Kingdom
DWest Germany
-0.5
i
i
r
i
1
r
10
2
12
r
i
14
r
t
r
~~
i
r
20
16
(Thousands)
GNP
Figure 2-9
countries.
per Capita per Year (1988 U.S. $)
Average annual population growth
Source:
A
country means that in that country there will probably be a
rate versus per capita
GNP
for selected
Adapted from World Bank (1989). "Gross National Product" and
"Population and Growth Rates."
22
Sec. 2.3
33
Industrialization
number of cars, high steel production, an abundance of food, good housing, and
its natural resources
It also means that the fuel for this industrialized society
and those of other countries supplying them to the consuming nation are being delarge
—
so on.
pleted and that the waste products of industrial production
ants
—
—
—
water, and land pollut-
air,
Thus from an environmental point of view,
high-GNP country can create pressure on the environment and re-
will create environmental problems.
one person living
in a
sources equivalent to that caused by perhaps hundreds of people in a
In this sense, statistics on
GNP
low-GNP
between countries
are useful comparisons
in
country.
determin-
on resources: the benefits and conven-
ing relative pressures on the environment and
iences of a high standard of living in the developed countries can be translated into
potential environmental
GNP
damage and resource depletion through
the use of per capita
statistics.
A
word of warning, however, about making
comparisons of
direct
GNP
per capita
data between countries and regions which have very different characteristics: to con-
clude that a person in an urbanized, developed country with $10,000 a
is
$1000
GNP
per capita figure
is,
per capita
food, clothing, and fuel by their
Many of the needs of the urban
who may also provide most of their
of course, erroneous.
dweller are not required by the rural inhabitants,
own
hands,
which case these products would not be
in
GNP.
included in the
Steel production has been
acknowledged
as another
major index of industrial de-
Henry Bessemer's discovery of the process of converting pig
velopment.
by burning off impurities by introducing
Revolution.
advent of
GNP
10 times better off than a person in a rural, underdeveloped country with a
figure
Prior to that, iron
charge was
air to the
iron to steel
critical to the Industrial
With the
had been smelted by roasting ore over coke.
construction of railways, ships, bridges, and heavy machinery, which
steel, the
had previously been very limited due to the structural inadequacies of
iron,
was
possi-
ble.
Global
steel
production increased dramatically from 0.5 million tons
million tons in 1900.
In
1988, world steel production
in
1870
metric tonnes.
Table 2-4
Notice that
but three countries, China, India, and Brazil, are considered to be
all
developed nations.
headed the
list
production
in
less
It is
to
28
was approximately 780 million
a ranking of the top 16 steel-producing countries in 1988.
is
not surprising to see that in 1988, the
together with Japan.
However,
in
CIS and
more
the United States
recent years the rate of growth of steel
developed countries has declined, while
it
has increased sharply
in
some
developed countries, an indication of the spread of industrialization to the less de-
veloped regions.
The
tistic,
fact that industrialization is
the annual
growth
rate
facturing, construction, electricity,
industrialization
availability of
is
included
spreading
of industry.
in this
This
is
highlighted by another industrial sta-
statistic
encompasses the mining, manu-
and gas industries. The multiplier or ripple
raw materials, and the supporting infrastructure, such as road,
transport, are considered.
rail,
or air
Since these variables are related to population, consumption,
and pollution, the index serves as an indirect measure of the annual increase
mental degradation.
effect of
index because such variables as the labor supply, the
In recent years this index has
been highest
in the less
in
environ-
developed
34
Population and Economic Growth
TABLE
2-4
Rank-
Chapter 2
SIXTEEN LARGEST STEEL-PRODUCING COUNTRIES, 1988
Country
1
1
(1)
CIS
2
(3)
Japan
3
(2)
4
11
(former
Steel production-'
Share of world
(millions of metric tons)
production" (%)
USSR)
164.0
(151.0)
21.0
(21.2)
105.7
(102.1)
13.6
(14.3)
United States
90.6
(124.3)
11.6
(17.5)
(5)
China
59.0
(31.0)
7.6
(4.4)
5
(4)
West Germany
41.0
(41.2)
5.3
(5.8)
6
(13)
Brazil
24.6
(12.2)
3.2
(1.7)
7
(6)
Italy
23.7
(24.3)
3.0
(3.4)
8
(22)
South Korea
19.1
(5.0)
2.5
(0.7)
9
(8)
United Kingdom
19.0
(20.3)
2.4
(2.8)
10
(7)
France
19.0
(22.8)
2.4
(3.2)
1
(9)
Poland
17.0
(19.5)
2.2
(2.7)
(2.2)
1
12
(11)
Republic Czech/Slovekia
15.4
(15.4)
2.0
13
(12)
Canada
15.1
(14.9)
1.9
(2.1)
14
(14)
Rumania
15.0
(11.6)
1.9
(1.6)
15
(10)
Belgium/Luxembourg
14.9
(17.4)
1.9
(2.4)
16
(16)
India
14.2
(9.5)
1.8
(1.3)
779. X
(711.8)
World
total
'Figures for 1978 in parentheses for comparison.
b
ClS:
Commonwealth
Source:
of Independent States formed
in
1991 from
1
of 12 Soviet Republics.
I
AISI (1978. 1988).
countries, ranging
between 4.5 and 7.2% per annum.
The more developed nations
is that more developed
eraged about 3.2% per annum. The reason for the difference
tions already have large, well-established industrial bases
avna-
and have reached a plateau
in
their industrial growth.
Statistics
on the growth of
tant
measure of
ing
aluminum,
steel
cement,
building
automobiles, and airplanes.
production have been provided as but one impor-
Many
industrialization.
Such
others could be cited, such as statistics regard-
materials,
statistics are
plastics,
farm
fertilizer,
machinery,
provided by national and international
organizations annually, or at least every few years.
They generally confirm
that in-
creases in industrial production have occurred worldwide, being particularly rapid in the
more developed countries
in certain
in the
two
to three decades following
World War
The more developed countries have
noring environmental effects.
and now
tried to pass
on the lessons learned from
poorer, overpopulated countries, industrial growth with
GNP,
more important than environmental
damage will grow in the
increases and economic growth occurs.
is
pected that environmental
ig-
However, the newly developing countries are usually un-
der severe financial constraints, and not surprisingly, the advice
higher
II,
of the less developed countries.
its
protection.
less
is
resulting
It
is
To the
employment and
ignored.
therefore to be ex-
developed regions as population
Sec. 2.3
35
Industrialization
2.3.2 Technology of Production
The post- World War II period experienced unprecedented growth in the economy of most
of the more developed countries, particularly the United States, Japan, and the former
West Germany. In the United States this growth has occurred in many sectors of the econ-
omy
—
in agriculture
and
air conditioners, detergents,
fiber
goods, synthetic
less effective, not as
thetic tibers replaced
mal wastes as
communications, transportation, the
forestry, manufacturing,
source industries, and others.
New
products were mass produced
snowmobiles,
plastics,
—
computers, microcomputers, synthetic
and insecticides. Some of these replaced goods
fertilizers,
wool and cotton, and synthetic
fertilizers.
examples demonstrate
•
In
some
instances, the
this point.
(
fertilizers
replaced compost and ani-
new products and
the wastes
tificial
DDT,
and thus increase
to control insects
DDT
in
some
agri-
countries.
where they are fed
the concentration of livestock on small land areas
ar-
foods to obtain high productivity, "agricultural industries" have emerged.
Chicken hatcheries,
wastes
their
had very serious side effects on wildlife and humans.
This led a few years ago to the banning of
Through
from
Numerous
1972):
pesticides, particularly
cultural production, has
•
were
Barry Commoner, the eminent U.S. ecologist. discusses
book The Closing Circle
The use of
that
durable or more costly. For example, detergents replaced soaps, syn-
production were later found to have been quite harmful to the environment.
these in his
re-
television sets, stereos,
in a
broilers,
and pig and beef feedlots may produce more organic-
country than the domestic wastes from the people.
shortage, the wastes which previously were put on the land are
Because of land
now
often
dumped
untreated or poorly treated into rivers, contributing greatly to water pollution.
•
The
intensive use of synthetic fertilizers, particularly nitrogen, has led to high ni-
trate levels in surface
waters and groundwaters.
mia, or "blue babies" disease, in infants.
is
•
another side effect of the overuse of synthetic
The production of
is
methemoglobinelakes
fertilizers.
synthetic organic chemicals as raw material for synthetic libers,
pesticides, detergents, plastics,
chlorine
Nitrates cause
The problem of eutrophication of
and synthetic rubber has increased
frequently used in these processes,
its
as well, requiring in turn greater production of mercury, since
produce chlorine.
greatly.
Since
production has increased sharply
mercury
is
used to
Increased release of mercury to surface waters, however, has
resulted, via the food chain process, in high concentrations
mercury poisoning of people
who
ol'
mercury
eat a steady diet of such fish.
in fish
and
Synthetic prod-
ucts also require high energy for their production, and creation of this energy further contributes to environmental pressures.
•
The
vast increase in the
number of automobiles (and
until recently
of high-pow-
ered automobiles), together with the shift in the transportation of goods from
to trucks, has significantly increased air pollution
•
The introduction of
the nonreturnable bottle and the
creased the solid waste disposal problem and the
rail
problems.
throwaway can has greatly
litter
problem.
in-
36
Population and Economic Growth
The emergence of food packaging,
•
Chapter 2
as well as other kinds of packaging, has gen-
erated high quantities of solid wastes to be collected and disposed of.
The enormous
•
(NO
power has provided a growing
(S0 2 ) and various nitrogen oxide
increase in the production of electric
source of pollution problems.
Sulfur dioxide
emissions from power plants are major contributors to acid
v )
power
radioactive emissions from the operation of nuclear
rain.
Potential
plants, together with
the disposal of low- and high-level radioactive wastes as well as high-temperature
cooling water discharges, are other environmental problems.
Many
One
other cases could be cited.
will challenge
you
of the questions
and use of many new products since World War
tion
for the
much
In sum,
to prepare a particular case study.
II
These disturbances go
far
end of
this
chapter
clear that the produc-
are in large
measure responsible
many
of the highly indus-
increased environmental disturbances evident in
trialized countries.
at the
it is
beyond those
can be explained by
that
in-
creases in population and economic growth alone.
2.4
URBANIZATION
Urbanization refers to an increase
in the ratio
of urban to rural population.
may have been sown
the seeds of urbanization
as far back as
what has been called the Agricultural Revolution.
food gatherers of these early times settled down
animals and grow food. The result of
which freed people from
plus,
Frjm
toiling
amongst
specialization of labor
Historically,
5000 B.C.,
in
Gradually, the nomadic hunters and
numbers
in increasing
this transition
was
to domesticate
the development of a food sur-
on the land. There soon developed a division and
newly emerging nonagrarian population group.
this
recognizable today as
cities.
The
first cities
Euphrates rivers between 4000 and 3000 B.C., in what
played the largest role
and rich
soils
in the
were necessary for
cess to and from the
site,
for these purposes.
cultivation.
Iraq.
and water had
Nearby flat land
was a need for easy acavailable. The floodplains of the
to be readily
and Indus
rivers,
This early urbanization led to possibly the
lumber and
to provide
Environmental fac-
cities.
In addition, there
of the most disastrous, environmental impacts
Middle East
arose along the Tigris and
now
is
development of these early
Tigris and Euphrates, as well as those of the Nile
the
to
these primitive social developments, society developed complex, interrelated so-
cial structures
tors
7000
in history
—
fuel for the cities.
were ideally suited
first,
and certainly one
the destruction of forests in
The
resulting soil instability,
the consequent desertification, and ultimately the loss of productive land were the tragic
consequences from which
this region still suffers.
was not until the eighteenth century, however, that modern urbanization really
accelerated. The limited urbanization that had taken place before then was almost enIt
tirely
due
to migration
in agriculture.
from
The spur
to
rural areas to
who were no longer needed
200 years has been technological
towns by people
urban growth over the
last
development, that has stimulated industrialization and increased the demand for labor
the cities.
in
37
Urbanization
Sec. 2.4
2.4.1 Definition of Urbanization
on urbanization trends and
Statistics
The problem
because of the
arises
rates in various countries are difficult to
many
countries distinguish between urban and rural areas by the size
what point does
at
A
sand?
hundred
compare.
Some
different definitions of urbanization.
of the community.
But
concentration of people become urban? Five thousand? Ten thou-
a
thousand'.'
What may be
defined as urban in one country
may
be rural
For example, areas with as few as 400 inhabitants are designated as urban
in
another.
in
Albania, while
other countries
in
Japan the lower limit
m
200
built-up areas with less than
between houses.
is
employed
in
some
status in
Sweden, urban areas are those
In
In India, places
of not less than 1000 persons per square kilometer where
male adult population
Urban
50,000 inhabitants.
is
assigned on the basis of density.
is
work
nonagricultural
having a density
of the
at least three-fourths
Other
are called urban.
countries define urban areas in terms of the extent of urban characteristics, such as the
number of plazas
Still
ities.
or schools or the availability of sewers, electric, or water supply facil-
other countries classify urban areas by the type and extent of administrative
control exercised over them.
The many
definitions of urban areas that have resulted
and administrative differences among nations make
Most
tern.
20,000
often, a population of
called urban, and this
is
from
historical, cultural,
difficult to discern a
it
common
pat-
used as the size above which an area
is
is
the criterion used in this book.
Current situation.
Accelerating urban growth
eth century has been a global
phenomenon.
It
in the last
half of the twenti-
has been most dramatic in the less de-
at a rate of 4% or more during the post-World
more developed regions during the same period, urbanization avwhich is about double the population growth rate in these regions.
veloped regions of the world, proceeding
War
II
period.
In the
eraged about 2 f/f,
Although the population growth
portion has
due
grown from 55 l/
<
to
rate in the
10%
MDR
has been decreasing, the urban pro-
of the total population.
Much
of this increase
is
to the decline in rural population through rural-to-urban migration rather than to the
new immigrants to the cities.
The extremely rapid growth of the urban population
arrival of
in the
MDR
is
clearly evident in Figure 2-10.
large an urban population as the
was almost double
that of the
jections suggest that the
1.1
billion in the
MDR
LDR
LDR,
MDR
in the
1950, the
LDR
MDR
compared
to that
had almost twice as
but by 1990 the urban population in the
(1.5 billion to
875 million: figure 2-9).
have over 4 billion
will
by 2025.
In
in
Note from the figure
rates are declining in the rural areas of the
the
LDR.
the
The trend toward greater urbanization
more developed and the less developed
MDR.
will
the
U.N.
LDR
pro-
urban population, compared to
that although population
same trend
is
growth
not yet evident in
have important ramifications for both
regions.
II
the
economic growth
rate in a
country does not exceed the rate of urban population growth, urban living conditions
that nation will not
improve.
urban growth, the implication
On
the other hand,
may
if
the
be that most of the
in
economy does keep pace with
resources will be consumed to
38
Population and Economic Growth
Chapter 2
4.5
Rural Population
4
~1
1
950 1 955
I
1
960
I
I
1
I
965 1 970
1
I
I
975 1 980
1
I
985
1
990
I
I
1
in
MDR
o
I
I
995 2000 2005 201
I
I
201 5 2020 2025
Year
Figure 2-10
Urban and
rural
population
in
more developed and
less
developed regions.
Source:
U.N. (1990, 1991a).
support the urban population, with
little, if
any, remaining to develop the rural
economy.
Agricultural output per farmer will have to increase to provide for the increasing
num-
bers of urban inhabitants and the declining or slower-growing rural population.
2.4.2 Growth of Cities
One
It
of the current characteristics of urbanization
has been estimated that
more almost doubled
in the
is
the trend toward "urban giantism."
period 1950-1975 cities with 5 million inhabitants or
their share of the total
urban population, while
than 100,000 inhabitants declined in relative importance.
ble 2-5.
Also evident
in this table is the
the less developed regions.
LDR
in the
year 2000.
cities
is
with fewer
reflected in Ta-
tendency toward urban giantism
in
many
of
For example, the percentage of urban inhabitants of the
living in cities over 5 million has
23.5%
This trend
been projected
Similar statistics for the
from 2.2% in 1950 to
jump from 9% in 1950
to increase
MDR
show
a
3
Sec. 2.4
to only
York
16.4%
LDR
in the
39
Urbanization
in the
in
2000.
Therefore, cities such as Mexico City, Sao Paulo, and Shanghai
soon have much larger populations than
will
MDR.
cities
such as Tokyo and
year 2000 for a few of the large cities to illustrate this point further.
such as Paris and London had dropped off the
cities
New
Table 2-6 traces the recent population history with projections to the
list
Large historical
of the 12 largest cities in the
world by 1990.
2-5 ESTIMATED PERCENTAGE OF URBAN POPULATION BY CITY-SIZE
CLASSIFICATIONS IN 1950, 1975, AND PROJECTION TO 2000
TABLE
MDR
World
1950
100
Total
Over 5 million
2000
1975
100
100
LDR
2000
1975
1950
100
100
100
1950
100
1
2000
975
100
100
6.6
12.6
20.9
9.0
14.2
16.4
2.2
10.9
23.5
2 to 5 million
10.2
10.4
13.0
10.5
8.9
13.3
9.5
11.8
12.9
to 2 million
7.8
9.5
10.0
8.6
10.1
10.3
6.5
8.9
9.9
9.6
9.9
8.9
9.1
10.0
9.3
10.6
9.8
8.6
11.8
12.7
10.7
11.6
12.5
11.5
12.1
12.9
10.2
1
500,000
to
200,000
to 500.(100
1
million
100.000 to 200,000
Other urban
Source:
U.N.
TABLE
8.6
8.0
6.6
8.2
8.0
7.1
9.3
8.1
6.3
45.4
36.9
29.9
43.0
36.3
32.1
49.8
37.6
28.5
(1979).
RANK AND POPULATION (MILLIONS) OF SELECTED
2-6
1960
Rank
City
Mexico City
New
Pop'n
5.4
4
9.4
10.7
2
14.9
15
4.7
10
8.1
1
3
14.2
1
4
8.8
Los Angeles
Rank
2 000°
1990
1980
2
York
Shanghai
Rank
Pop'n
1
Tokyo
Sao Paulo
1970
CITIES, 1960-2000
Pop' n
Rank
Pop'n
Rank
Pop'n
3
14.5
1
20.2
1
16.9
2
18.1
3
19.0
4
12.1
3
17.4
2
22.1
16.2
2
15.6
4
16.2
5
lh.8
11.2
5
11.7
5
13.4
4
17.0
1
25.6
7
6.5
7
8.4
7
9.5
6
11.9
9
13.9
12
5.5
14
6.9
8
9.0
7
11.8
6
15.7
6
6.8
6
8.4
6
9.9
8
11.5
12
12.9
Bombay
17
4.1
16
5.8
15
8.1
9
11.2
7
15.4
Seoul
30"
19
5.3
13
8.3
10
11.0
15
12.7
8.1
9
9.0
II
10.8
8
14.0
7.0
10
8.8
12
10.7
16
12.5
Calcutta
Buenos Aires
Beijing
Rio de Janeiro
9
6.3
9
14
4.9
13
'Estimate of population.
Source:
U.N.
(1990. 1991a)
Global density
to be very high, but
ters
—
cities.
in
it
1976 was 20 people per square kilometer.
This does not seem
does not take into account the human tendency to gather
Only 30% of
the earth's land
is
potentially arable.
in clus-
The remainder,
in
40
Population and Economic Growth
mountains, frigid areas, deserts, and other barren areas
For
all
practical purposes, the limited arable land
of
is
little
Chapter 2
use for agriculture.
must support the world's growing
population.
In contrast to the low global density, the density in urban areas may be greater by
two orders of magnitude. For example, the density of Hong Kong is over 6000 persons
per square kilometer. The problems of water supply, waste disposal, housing, and trans-
portation created by such high densities are staggering.
2.5
ENVIRONMENTAL IMPACT
It
is
important to recognize the impacts that urbanization and industrialization have on
The environmental impact matrix provides a convenient inventory and
The pioneering work in this area was done by Leopold et al.
(1971) and has been reviewed by Munn (1979). The matrices for the impacts of urbanization and industrialization are illustrated in Tables 2-7 and 2-8. The horizontal axis
the environment.
display of these impacts.
lists
the
various aspects of urbanization or industrialization, while the vertical axis contains
components of
impacts, and others
teractions
the environment
—
between each
each element
in the
—
as appropriate.
activity
the atmosphere, hydrosphere, lithosphere.
The elements of
human
the matrix identify potential in-
and each environmental characteristic. Questions about
matrix can then be considered.
For example, does the mining
in-
dustry affect air quality? (Answer: yes, from particulate matter released from open-pit
operations, and the gaseous and particulate emissions from processing.)
technique ensures that most questions are asked.
of ignorance of
its
If
an impact
is
missed,
The matrix
it
is
because
existence rather than because of forgetfulness.
The impacts identified can then be classified as severe, moderate, slight, and zero,
scheme may be used. The classification is ultimately subjective and
or a numerical
should preferably be done by several people, each influencing the opinion of others,
the hope that an informed, impartial consensus will emerge.
ten placed
on environmental changes
that are irreversible,
Particular emphasis
is
in
of-
such as severe terrain distur-
bances, extinction of rare or endangered species, or widespread contamination.
The environmental impacts of urbanization
predominant atmospheric effect of urbanization
are
is
many and
varied (Table 2-7).
The
the alteration of the atmosphere's
chemistry through the release of massive quantities of
C0 2
gen, dust, particulate matter, noxious and toxic chemicals.
,
oxides of sulfur and nitro-
The sources of
these con-
taminants are diverse: industry, most forms of transportation, the heating of buildings,
municipal incinerators, sewage treatment works, open
tion, significant heating
from heat-absorbing surfaces such
tion to the heat released
fires,
and
landfill sites.
In addi-
of air masses over urban centers occurs as a result of reradiation
from
all
as roads, parking lots,
and rooftops. This
types of combustion and industrial systems.
is in
addi-
The com-
bustion of hydrocarbons, particularly those used in the transportation sector, also gives
rise to
photochemical "smog" as a result of the interaction of various by-products of the
combustion process and energy from solar
radiation.
TABLE
41
Environmental Impact
Sec. 2.5
ENVIRONMENTAL IMPACTS OF URBANIZATION
2-7
Urban
Environmental
Population
component
(numbers and density)
Atmosphere
t
omponent
Land use
Air pollution from
Increased average
Increasing release of
Services
Transportation
carbon dioxide, de-
temperatures for
creased oxygen pro-
most urbanized
duction, as plant
eas
Particulates, noxious
fumes from
combustion of fuels
Creation of photo-
ar-
chemical smog
sew-
age treatment
Emission of lead from
colonies are de-
inciner-
ators, landfills,
works,
etc.
some engines
stroyed by spreading urban areas
Hydrosphere
Greater
demand on
More
Human
sources causing
subsurface)
creased pollution
tered by infrastruc-
load
ture
re-
Drainage patterns
in-
Complete changes due
ban wastes and
agricultural or un-
landscaping,
scape, etc.
stallation, repairs of
etc.
utilized land to ur-
services disturb
ban uses
landscape
Psychological impacts
that
of runoff from rainfall
may
the hydrosphere
severe because of the large
Stormwater also has an impact. Although the
may
total
quan-
not be altered significantly, the rate and characteristics
be changed sufficiently to cause
considerably greater than the rate
As
is
must be provided and the correspondingly large volumes of
which water runs off a paved road or parking
course or park).
ol
noise, air pollution
used water requiring disposal.
of the runoff
in-
Increased noise levels
Health effects
The impact of urbanization upon
if
Sanitary landfill of ur-
Disruption or disfig-
urement of land-
volumes of pure water
and
age outfalls
Pollution from boats
to construction.
sity living
at
landfills
Discharges from sew-
al-
tion oi uninhabited
pacts of high-den-
tities
from
polluted with lead
(both surface and
Psychological im-
impacts
Leaching of pollutants
Rain, surface waters
hydrologic
Increased transforma-
Lithosphere
intense use oi
water resources
it
damage
lot,
or inconvenience.
The
rate
or off a smooth pitched roof,
is
runs off a rural or forested area (such as a golf
a result, water can accumulate rapidly in an urban drainage system,
an overflow occurs, extensive flood
damage
is
possible.
Moreover, these storm-
waters are often contaminated by chemicals or particulates adsorbed or absorbed during
rainfall, or material
such as
oil
being washed off streets and parking
of water resources by stormwater
is
a
problem
in
potential contributor to the contamination of the hydrosphere
chate,
that
comes from
landfills
lots.
Degradation
most urban environments.
is
Another
the drainage, called lea-
of municipal solid wastes or toxic and hazardous
wastes.
From
lithosphere
The
a visual inspection of the urban environment,
was
the part of the environment
original state of the
you would conclude
that the
most dramatically altered by urbanization.
environment appears
to
have changed irreparably.
tions of the surface have been altered, rivers diverted,
The
eleva-
and lowlands either excavated for
42
Population and Economic Growth
harhors or
The "water edge"
filled in for building.
the character of
cities
In fact, the construction of buildings
facilities.
many
many
has been pushed
far-
development and expansion of industry, transportation,
ther into the lake to facilitate
and recreational
in
Chapter 2
and roads has revamped
Native ecosystems have been replaced by urban patterns.
regions.
Circulation of air has been altered (on a local scale) by the presence of obstructions,
such as
tall
buildings and smokestacks.
Transportation, both public and private,
is re-
sponsible for substantial alteration of the landscape because of the construction of
roads, railroads, parking lots, airports, harbors, and warehousing and shipping facilities.
The provision of municipal
sanitary landfills,
services such as water towers,
pumping
stations, reservoirs,
and other structures accounts for some of the changes observed
in the
urban environment.
The human impacts of urbanization tend
The
health effects of noise,
and assess.
to be rather difficult to define
and water pollution, and the psychological stresses
air,
caused by high density and a relatively "fast-paced" environment are not easily quantified.
Many
exposure
of the effects are not particularly harmful in isolated contacts, but continued
to inhalation
may
of low-level concentrations of lead, for example,
be a
much
more serious problem. The psychological impacts are the least understood and as a result are the. most difficult to evaluate. However, there are few people who would deny
that these stresses do exist.
The environmental impacts of industrialization tend to be a little easier to establish compared to those of urbanization, because the focus is on a smaller group of interests.
Table 2-8, which presents the environmental impacts of selected groups of
industries, is arranged in a fashion similar to Table 2-7 for display of the effects of urbanization.
Although the table
is
reasonably self-explanatory, a brief review using the
mining industry as an example may be helpful.
The impact of
mining industry on the environment
the
is
substantial.
m.ning and the transportation of ores contribute particulate matter
Processing of the metal ores (smelting, roasting,
etc.) contributes
to the
oxides of sulfur and
nitrogen to the atmosphere, depending on the material being processed.
ous emissions
may be
noxious, toxic,
or. in
Open-pit
atmosphere.
Various gase-
the case of the oxides, precursors of acid
rain.
Runoff from mine
tailings
subsurface water resources.
the receiving water body,
may wash hazardous
materials into nearby surface or
Occasionally, processing wastes are discharged directly to
where they impair water quality and
most obvious impacts of mining on the lithosphere are
(
1
)
affect aquatic
the residues
life.
The
from the dump-
ing of tailings and processing wastes directly on the landscape, and (2) the disruption of
many
activities,
such as agriculture, forestry, and recreation, particularly from open-pit
mining and quarrying.
The impact of
much
debate.
the
mining industry on human health and well-being
is
a subject of
However, the adverse effects of the sustained exposure of miners to min-
erals such as coal (causing black lung disease)
been established beyond doubt.
near inhabited areas
local population.
may
and asbestos (causing asbestosis) have
Noise pollution from mining or quarrying operations
also have negative effects
on the health and well-being of the
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44
2.6
Population and Economic Growth
Chapter 2
THE DILEMMA OF INDUSTRIALIZATION
AND URBANIZATION
Industrialization and urbanization are
are living in larger and larger cities.
More and more people
These high-density communities pose a special
worldwide phenomena.
challenge in the provision of potable water, clean
waste disposal, transportation, and
air,
Modern communication has made
recreational space.
raised expectations in most of us for a better
life.
the world a global village and has
It
will take
enormous
plomacy, and determination for the world's leaders and those
engineers, lawyers, economists, and managers
tists,
next century.
emerged
To
—
who
to guide
ingenuity, di-
help them
—
scien-
development over the
influence governmental policies on these matters, pressure groups have
that often put their case
forward
in a
biased and exaggerated way.
not
is
It
surprising that on a particular environmental issue reports appear that are diametrically
opposed
and
each other.
to
We
in the scientific field.
have
It
all
witnessed
becomes
popular press, radio, television,
this in the
difficult at
times to
know whom and what
to be-
lieve.
Some groups
claim that continued economic growth by nations
is
an impossible
goal that will inevitably lead to the failure of world society and environmental disaster.
They argue
fairs,
that a steady-state
although the timing of
their current state of
economy
is
this will vary
development.
a necessary
and desirable future
considerably
among
state of af-
nations, depending
on
For example, Daly (1977) asserts that "a U.S. style
high-mass consumption, growth dominated economy for a world of 4\ billion people is
impossible. Even more impossible is the prospect of an ever growing standard of per
capita consumption for an ever growing world population."
Meadows
Schumacher (1973), Ward (1976), and Ward and Dubos (1972) have
et al.
(1972),
also dealt with the
controversial topic of limited growth.
On
the other hand, virtually every nation
global economy.
is
attempting to increase
derdeveloped countries, attempting to industrialize, find that their
scale gives
them
its
share of the
Multinational companies compete vigorously for world markets.
Un-
much lower wage
a competitive edge over developed countries in certain fields.
Eco-
unemployment have a predictable effect on how governments view the apparent conflict between economic growth and environmental
protection.
Unfortunately, when the issue is presented simplistically as jobs versus a
nomic recession and
its
resulting
clean environment, the pressure on politicians to allow industry to "defer" pollution
control measures
Two
U.S.
is
often irresistible.
"doom and gloom" and
The Global 2000 Report to the
commissioned by President Carter, was
reports highlight the controversy between the
"things are getting better" environment philosophies.
President of the United States (Barney, 1980),
produced to a large extent by government and quasi-government agencies.
may
Although
it
be presumptious to classify such a massive report into one of the two categories
in the "doom-and-gloom" category. An updated
2000 Revised and produced by a group of independent scientists under the leadership of J. L. Simon and Herman Kahn, disagreed comThe report, later retitled The
pletely in many aspects with the earlier version.
mentioned, on balance
it
does belong
version, originally entitled Global
The Dilemma
Sec. 2.6
of Industrialization
45
and Urbanization
Resourceful Earth (Simon and Kahn. 1985), stated that "if present trends continue, the
world
2000
in
will be less
crowded,
more
less polluted,
nerable to resource-supply disruption."
Two
and
stable ecologically
same
serious studies on the
less vul-
topic thus have
very different conclusions!
One
of the most comprehensive reports on the effects of environmental abuse on
economy was carried out over a three-year period by the Norwegian Prime
Gro Harlem Brundtland, and her 22-member U.N. commission (United Nations. 1987). The report warned that pollution and the overuse of resources threaten to
alter radically both the planet and the lives of many species upon it. including the human species. The Bhopal chemical accident (the worst industrial accident to date), the
the world's
Minister.
African famine, and the deaths of about 20 million children per year from diseases
lated to unsanitary drinking water
The prediction
for the 1990s
was
re-
and malnutrition were a few of the calamities noted.
would be even more
that there
disasters
—
particularly
droughts and floods, which are most directly associated with environmental mismanagement.
A
watch
tems
similar warning
Institute,
who
that support
was expressed by Lester Brown (1987), president of
noted that
life
human
use of the
on earth was pushing those systems over "thresholds" beyond
which they cannot absorb such use without permanent change and damage.
In recogni-
importance of environmental protection, the World Bank announced
tion of the
that
World-
the
water, land, forests, and other sys-
air,
environmental factors would be one of the primary considerations
in
in
all
1987
of the
bank's future lending and policy decisions.
The
is
large
gap
in the quality
of
life
between the world's richer and poorer nations
expected to widen because of the higher population growth rates
regions.
The developed nations have recognized
have found
it
the
amounts of
difficult to divert sufficiently large
in the less
developed
uneven distribution of wealth but
their resources to aid the
poorer countries, since they themselves are faced with difficult problems of slow eco-
nomic growth and
inflation.
The escalating
costs of resources, particularly of energy,
have caused very serious economic problems for
tries,
which must pay
For the three-fourths of the world
to reach the
same standard of
now
impossible.
could also
residing in the less developed regions that aspire
a
tenfold
peaceful means ?
in the
We
to assimilate.
in the richer
standard of living
must hope
that a
in the
regions,
approximately tenfold
this is clearly
consumption of energy and resources
in the
increase in pollution, which
environment
whether the standard of living
allow an increase
more developed
to increase
Considering the present energy reserves and their value,
likely) impossible for the
tion of
would have
Furthermore, a tenfold increase
mean
but especially for the poor coun-
whatever exports they can manage.
living as the one-fourth in the
global energy and resource consumption
for that to occur.
all,
for their energy imports with
would be
Ultimately,
countries will have to
poorer countries.
way can be
difficult
we must
found.
Can
or (more
face the ques-
come down
this
to
happen by
46
Population and Economic Growth
Chapter 2
PROBLEMS
2.1.
Define or explain the following terms.
Population growth
(a)
(b) Natural increase of population
2.2.
(c)
Net migration
(d)
Zero population growth
(e)
Replacement growth
(f)
Total fertility rate
(g)
Age
rate
rate
(i)
Urban versus
(j)
Population density
1975 a country had a population of 10 million.
In
of 30 per thousand per year and
tively constant.
structure
(h) Gross national product
What
its
Over
the past
rural
20
years,
its
live birth rate
death rate of 14 per thousand per year have been rela-
2000? What
will be the population in
is
the doubling time of this
population and the annual growth rate?
2.3.
1977 Ghana had a population of 11.3 million.
In
Assume
deaths during that year.
(d)
(a)
Explain
(b)
Give
(b)
(c)
2.5.
examples
that
(d)
A
A
A
A
(e)
A
(b)
(c)
state or province) for
Calculate the average annual population growth rate from this information.
in the
examples provided
Which
rate
for:
declining population
stable population
stable population having recently experienced
major war casualties
stable population experiencing recent large immigration of
was instantaneously reduced
(a)
Plot the population
(b)
By
from
1
This situation continued
young people
800
What
in
until
birth
1900,
to 2000.
and growth
rate
on the same time
scale,
show
the
population (called the demographic transition) that occurred.
that
because popu-
increases exponentially, whereas food supplies increase arithmetically, population
would soon
outstrip the available food
Why
distinction has been
this
1980 the
conditions would have caused this to take place.
global catastrophy.
world
In
rates
the death
remaining constant.
About 200 years ago, Robert Malthus, an English economist, predicted
A
and death
when
remained constant.
to 20, but the birth rate
plotting the birth rate, death rate,
dramatic increase
lation
likely to
rapidly growing population
birth rate fell to 30, the death rate
(c)
is
Figure 2-3?
in
of 50 and 45 per thousand per year.
2.10.
your country (or
the birth rate, death rate, immigration, and emigra-
is,
1800 an undeveloped country had a population of 20 million with
In
20 years?
growth or decay.
statistics for
Sketch hypothetical population pyramids
(a)
2.9.
persists for
meant by exponential growth or decay.
is
that follow exponential
zero.
Distinguish between zero population growth and replacement growth.
occur
2.8.
five
words or by an equation what
most recent period available:
tion rate.
2.7.
in
Obtain the average annual demographic
the
2.6.
was
What were the birth and death rates in that year?
What was the rate of natural increase in population?
What was the approximate doubling time in years?
What will the population be in 1997 if this growth rate
(a)
2.4.
There were 542,400 births and 192,100
that the net migration
in the
and population would have to be limited to avoid
has this not happened?
made between
the
more developed and
material presented on population and
has been done?
less
developed regions of the
economic growth.
Why
do you think
Chapter 2
47
References
why world
2.11. State and discuss the reasons
population
is
going to
at least
double over the next
100 years.
2.12.
List the
advantages and disadvantages for a country having
rate; (b) a
high economic growth
2.13. List several of the
you be prepared
methods
have been used to control population growth. Which would
that
your country, assuming you
to support in
high population growth
(a) a
rate.
live in (a) a
country with a stable
population; (b) a country with a rapidly growing population?
2.14.
The book by Meadows
lished.
It
now
is
et
and prepare a short essay on your reaction
2.15.
A
if
I
it
than
do."
I
know what
"I
them.
institute
about
I
need
to
do
What
is
to solve the
one example of each and discuss the consequences.
problems raised
in
relation to
in this
book, but
less
Revolution has produced social, economic, and environmental changes.
meant by urbanization.
List
and explain as many environmental implica-
you can think of which were not mentioned
Explain how the environment and
GNP
in a
developed country are
in
Table 2-7.
related.
Prepare a case study for a product that has been invented, produced, and marketed
years which has caused significant environmental problems.
What,
and should be done about such a product? Use the matrix method
uct's
it
your reaction to his perceived dilemma?
Industrial
is
Read
and replaced by someone who knows
State
what
was pub-
it
Library).
it.
will be defeated at (he polls
I
tions of urbanization as
2.19.
to
The
2.17. Explain
2.18.
New American
Western statesman was quoted as having posed the following dilemma
Meadows's book:
2.16.
when
(1972) caused considerable controversy
al.
available in paperback (Signet Books,
to
in
in recent
your opinion, can
demonstrate the prod-
environmental impact.
2.20. Select a specific industry that
mental impact matrix for
is
of major importance
in
your area, and prepare an environ-
Discuss your findings.
it.
management of municipal
2.21. Prepare an environmental impact matrix for the
solid wastes un-
der the following headings: Sources; Collection and Transport; Processing; Disposal; Rec-
ommended
Controls.
2.22. Prepare an environmental matrix for one of the following:
•
A
•
An
•
A
A
•
leather tannery outside a
automobile repair shop
town of 3000
in a
downtown
location
sanitary landfill for 20,000 people
wastewater treatment plant to serve a population of 100,000
in a city
on a lake
REFERENCES
AISI. Annual Statistical Report. 1978. Washington, D.C.: American Iron and Steel Institute, 1978.
AISI
Annual
Statistical Report. 1988.
Washington. D.C.: American Iron and Steel
BARNEY, G. O. The Global 2000 Report to the /'resident of the United
D.C: U.S. Government Printing Office. 1980.
BRAMWELL,
R. D.
Towns and
Cities:
Yesterday.
Institute, 1988.
Slates. Vol. 2.
Washington.
Today and Tomorrow: Agincourt, Ontario: Gage
Educational Publishing. 1977.
BROWN,
L. (ed). State oj the World.
Commoner,
B. The Closing Circle.
19X7. Washington;
New
D.C: WorldWatch
York: Bantam. 1972.
Institute,
1987.
.
48
Population and Economic Growth
Daly, H.
Frejka.
E. Steady-State Economics.
San Francisco: W. H. Freeman, 1977.
The Future of Population Growth.
T.
Leopold, L.
B.,
Clarke,
Hanshaw,
F. E.,
Chapter 2
New
York: Wiley. 1973.
B. B., and Balsey, R..
Jr.
"A Procedure
for Evaluating
Environmental Impact." U.S. Geological Survey Circular 645. Washington, D.C: U.S. Gov-
ernment Printing Office. 1971.
Meadows, D.
H.,
Meadows.
D.
L..
Randers,
to Growth. New
New American Li-
and Behrens, W. W. The Limits
J.,
York: Universal Books, 1972; also available as a Signet
Book from
the
brary, 1972.
Ministry of Industry, Trade and
Commerce. Canada Yearbook. Ottawa: Ministry of
Industry, Trade
and Commerce, 1970.
Ministry of Industry, Trade and
dustry,
Trade and
Commerce. Canada Yearbook. 1988/89. Ottawa: Ministry of
Commerce
In-
1989.
Census 1991. Ottawa: Ministry of Industry, Trade and Commerce, 1992.
Miinn. R. E. Environmental Impact Assessment. Scope
5.
Toronto: Wiley. 1979.
Pellard, A. H., Yosuf. F, and Pollard, G. W. Demographic Techniques. Sydney, Australia: Per-
gamon
Press. 1974.
PRB. Population Reference Bureau, World Population Data Sheet 1988. Washington. D.C:
1988.
PRB. Population Reference Bureau. World Population Data Sheet
1992.
Schumacher,
Simon,
J.
L.,
E. F. Small Is Beautiful.
New
York: Harper
and Kahn, H. The Resourceful Earth.
Suzuki, D. "Exponential growth
is
New
&
1992. Washington.
D.C:
Row, 1973.
York: Oxford University Press, 1985.
Merely Another Case of False Worship," The Toronto
Star,
1
1
January 1986.
Treshow. M. The Human Environment.
New
York: McGraw-Hill, 1976.
U.N. Concise Report on the World Population
in
1969 (Population Studies No.
48).
New
York:
United Nations. 1971.
New
U.N. Prospects of Population: Methodology and Assumptions (Population Studies No. 63).
York: United Nations. 1979.
U.N. Concise Report on the World Population
in
1980 (Population Studies No.
78).
New
York:
United Nations, 1981.
U.N. World Commission on Environment and Development. Our
Common
Future. London:
Ox-
ford University Press, 1987 (Brundtland Report).
U.N. World Urbanization Prospects, 1990.
New
U.N. World Urbanization Prospects, 1991a.
York: United Nations, 1990.
New
York: United Nations, 1991.
U.N. World Population Prospects, 1990 (Population Studies No.
120).
New
York: United Nations,
1991b.
Ward.
B.
Human
Settlements: Crisis
Conference on
Ward.
B..
Human
and Opportunity. Report prepared
and DUBOS, R. Only One Earth.
World Bank.
World Bank
Zito. G. V.. Population
Atlas.
and
for Information
Settlement. 1976.
its
New
York: W. W. Norton. 1972.
Washington, D.C: The World Bank, 1989.
Problems. Syracuse. N.Y: Syracuse University, 1979.
Canada.
CHAPTER
3
Energy Growth
O.J.C. Runnalls
Donald Mackay
As
indicated in Chapter 2. the world's population and
grow
to
for at least the next several decades.
and gross national product
is
more developed ones (Barney,
—
rely
its
economic output
larger
growth
in
will continue
both population
projected for the less developed countries than for the
1980).
Currently, three of every four inhabitants of the
earth live in the less developed countries,
ple
Much
and two-thirds of these
—over 2
on the gathering of wood and crop and animal wastes
billion peo-
to provide fuel for
cooking and warmth (World Bank, 1981).
Clearly, the world faces substantial increases in energy consumption, particularly
in
those disadvantaged areas where population growth
tations for
with
it
is still
high but individual expec-
improvement are also understandably high. The production of energy brings
the inevitable
consequence of environmental disturbance.
the denudation of forests to supply
wood
Whether we consider
for the people of the developing world, or the
atmospheric pollution that accompanies the generation of electricity
power
plants,
environmental problems grow as energy requirements
of this chapter, therefore,
is
to
examine the
availability of
in
rise.
energy sources
coal-burning
The purpose
in the future
and the environmental impacts from increased energy output.
49
50
3.1
Energy Growth
Chapter 3
SOURCES OF PRIMARY ENERGY
The sources of primary energy
available for our use have often been categorized as ei-
ther renewable or nonrenewable.
tion
They might
who
adopted by Putnam (1953),
also be thought of in terms of the descrip-
used the phrases energy income and energy
Energy income, or renewable energy resources, comprises those resources
capital.
are being continuously
renewed because of the presence of
tidal forces,
that
wind, falling
water, thermal gradients in the ocean, geothermal heat, direct solar input, the generation
of vegetable and animal matter, and so on.
Energy
nonrenewable energy
capital, or
re-
sources, refers primarily to fossil fuels, which were deposited on earth hundreds of millions of years ago, or to radioactive minerals,
When
formed.
tually, the fossil fuels are
time scale of
which were present when the planet was
such materials are mined, the quantity of energy capital
being replaced
human development
in nature,
but at a rate that
as to be insignificant.
coal can be considered nonrenewable in the practical sense.
Hence
The
is
is
reduced.
Ac-
so slow on the
natural gas, and
oil,
radioactive fuels ura-
nium and thorium are not being replenished either. In fact, over a long time span,
measured in billions of years, they are being transformed through radioactive decay
processes to stable elements. The currently available sources of energy are listed as renewable or nonrenewable
TABLE
3-1
Table 3-1.
in
AVAILABLE ENERGY SOURCES
Nonrenewable (energy
Renewable (energy income)
Hydroelectric energy
Crude
Tidal forces
Natural gas
Geothermal heat
capital)
oil
Coal
Biomass (wood, animal
refuse.
vegetable matter, etc.)
Nuclear fission
Synthetic
Wind
oil
(from
oil
sands and
oil shales)
Solar input
Ocean
heat
During the twentieth century, the annual consumption of primary energy provided commercially in the world has increased more than 10-fold, as
shown
in
Figure 3-1.
Part
of the increase was required by a growth of about 2\ -fold in the world's population during that period.
Another important part of the
rise in
energy consumption, however, was
a consequence of increasing mechanization, particularly in the industrialized world.
This
is
illustrated in Figure 3-2,
the twentieth century in
where the growing importance of machine energy
one of the industrialized countries, the United
States,
is
in
readily
apparent.
Wood
in
served as the predominant fuel
Figure 3-3.
of coal to the
in the
world
until
about 1875, as illustrated
The percentage contribution
world's primary energy supply reached a peak some 40 years later, at
Then
it
began
to be supplanted
by
coal.
Sec. 3.1
51
Sources of Primary Energy
100
400
/Nuclear
t«//Hydro
300
Machine Energy
HAvNatural
111
£200 -
_/
/
:
Crude
0l1
//
« 100
Gas _
4
T
1
-
//
//
I
I
1920
1900
y^Solid -
/
1
I
1960
1940
Fuels
1980
1850
2000
1900
1950
Figure 3-1
Figure 3-2
World's primary energy consumption during
the twentieth century.
Sonne:
1975
Year
Year
World Energy Conference
Growth of machine energy
Slates since 1850.
Source:
the
United
importance.
Now
in
Wyatt(1978).
(1986): British Petroleum (1992).
which time
its
there are those
use began to decline as
who
feel that oil
oil
and natural gas grew
may have passed
its
peak
in
in the contribution to the
world energy supply.
The growth of machine energy has been
by the rapid development of
fuel for
rising
internal
them by sophisticated
facilitated during the twentieth century
combustion engines and the provision of liquid
transportation, refining,
consumption of petroleum products has
and distribution systems.
led to intensive
the search for crude oil and natural gas deposits.
Many
The
worldwide programs
in
such deposits have been discov-
Most of the nations that are principal users of these
two commodities, however, do not have significant domestic supplies and must look to
other countries to obtain them. This imbalance in the supply of and demand for liquid
ered during the twentieth century.
and gaseous fuels forms the basis for a serious energy supply problem, which was
recognized by the world
in the
1970s.
first
52
Energy Growth
Chapter 3
10 2
0.99
10
0.90
Q.
Q.
C/3
Coal
0.70
10°
0.50
u.
0.30
o
10 M
Synthetic
^ **/jf
I
-
Hydro
«_
1850
1900
/,v
c
o
o
0.01
2000
1950
0.10
Liquids
Solar
xi
10 n
t
—
2050
Year
Figure 3-3
1981
by
World energy sources, 1860-2030.
the
International
Source:
Applied
for
Institute
Hafele, (1981) (copyright
Systems Analysis;
reprinted
by
permission from Ballinger Publishing Company); British Petroleum (1992).
3.2
CURRENT CONSUMPTION OF ENERGY
The world's annual consumption of commercially provided energy in 1991 was about
375 EJ [exajoule = 10 18 joules (J)] and was subdivided as shown in Figure 3-4 (see Table A-1.3 in Appendix A.l for SI prefixes).
Significant quantities of energy are provided internally in some industries by combustion of wastes, recycling of residues, and
so on, and are not accounted for in the normal commercial sense. A good example is
the forest products industry. Noncommercial energy also plays a particularly important
where wood and animal refuse
role in the developing countries,
sources of heat.
produced
EJ.
in the
Western world. Hence
Using the percentages shown
total
The use of other
to describe
units
is
energy consumption
in Figure 3^1,
sumption of commercially provided energy
in alternative
aid in the conversion process.
Now,
if
in
it
is
in
1991 was about 410
terms of exajoules as shown
ways.
The data
Hence
in
it
is
in
Table 3-2.
often desirable
Table 3-3 are intended to
3-2 are expressed
Table 3^1 are obtained.
the data in Table
usual units for each commodity, the results outlined in
in
more
more than one-third of the world's primary energy in
The enormous consumption of crude oil lies at the root of
world's energy problem. The growth of this appetite over the past 26 years is deNote from Figure
1991 was provided by
the
serve as essential
possible to express the 1991 con-
also widespread in the literature.
energy outputs
still
EJ of such internally generated energy was
In 1991, an estimated 35
3-^4 that
oil.
53
Current Consumption of Energy
Sec. 3.2
6.3%
38.5%
21.7°
26.8%
Figure
3—4
World consumption of commercially provided energy.
British Petroleum
(
TABLE 3-2 WORLD CONSUMPTION
OF COMMERCIALLY PROVIDED ENERGY.
Commodity
Crude
Quantity (EJ)
38.5
144.4
oil
Natural gas
21.7
Coal
26.8
demand,
in
in
in
81
1
100.5
Hydroelectric energy
6.7
25.1
Nuclear power
6.3
23.6
100.0
375.0
Source
a doubling
Source:
1991
Percentage
Total
picted graphically
1991.
1992).
British
Petroleum (1992).
What
Figure 3-5.
demand during
is
immediately apparent
is
that there has
been
Of necessity, production has risen to meet that
Many of the principal consumers, however, mainly
that time.
as indicated in Figure 3-6.
the industrialized Western world,
do not possess
substantial conventional crude oil
deposits, as illustrated in Figure 3-7.
The ex-USSR
countries,
States (CIS), plus Eastern
supply
at
present.
currently
called
Europe and China,
However,
this
is
the
Commonwealth
of
Independent
arc collectively self-sufficient in crude oil
not the case lor the
Western world.
The United
54
Energy Growth
TABLE
3-3
Chapter 3
ENERGY OUTPUTS AND CONVERSION FACTORS
Heat
Energy form
vali ae
AES
SI units
units
Energy output
Crude
38.512 TJ/10 3
oil
m3
m3
5.803 x 10 6 Btu/barrel
1.000 x 10 6 Btu/10 3
Natural gas
37.229 TJ/ 10"
Bituminous coal
29.993 TJ/10 3 tonne
TJ/GWh
TJ/GWh
(2)
b
3.6
3
Btu/MWh
Btu/MWh
10.000 x 10 6
(l) a 10.5
Electricity
ft
25.800 x 10 6 Btu /short ton
3.412 x 10 6
Conversion factors
Crude
oil
1
m
3
1
L
1
barrel
Natural gas
1
m
Coal
1
tonne
Energy
1
kJ
6.293 barrels
=
=
=
=
3
0.264 gal
42
gal
35.3
ft
3
1.1023 short tons
2204.6
a
For primary energy calculations,
this value is
adopted for hydraulic, nuclear, and purchased
assuming the conversion efficiency
the equivalent thermal energy of a coal-burning plant
b
lb
0.948 Btu
is
For secondary energy calculations, such as conversion of electrical to thermal energy, as
heating, this value
is
3-4
in resistance
1991
Commodity
Crude
Quantity
oil
Natural gas
10.4
x 10 6 cubic meters per day
69.4
trillion
cubic feet
Coal
3.6 billion tons
Hydroelectric energy
6.7
x 10 12 kilowatt hours thermal,
x 10 n
6.2 x 10 12
2.0 x 10 i:
2.2
Nuclear power
example, produced in 1991 only
55%
kilowatt hours electrical
kilowatt hours thermal,
kilowatt hours electrical
of the
output was the highest of any country in the world.
oil
it
consumed, even though
crude
oil*
*
stood
of that in 1970.
at
5.4
As of
x 10 9 m-\ about
Proven reserves are defined as
that
the
volume of
conditions.
oil
level,
end of 1985, the proven reserves of U.S.
six times larger than the 1991
neering information indicates to be recoverable from
its
Production within the United States
reached a peak in 1970 and has been declining slowly since then, to the 1991
80%
is
WORLD CONSUMPTION OF COMMERCIALLY
PROVIDED ENERGY,
which was
it
adopted.
TABLE
States, for
electricity;
similar.
remaining
known
in the
consumption
rate
ground which geological and engi-
reservoirs under existing
economic and operating
55
Current Consumption of Energy
Sec. 3.2
Total
1965
1945
Consumption
7 Mb / day
Figure 3-5
(1992);
EMR
1970
World
1975
1985
1980
1990
Year
World's crude
oil
consumption. 1965-1991.
Source:
British
Petroleum
(1993).
World
Total
60
Q
^r
40
OPEC
TO
CD
C
o
Rest
^r^—"
of
World
ill ill
20
1965
-
U.S.A.
"
1970
1980
1975
1985
1990
Year
Figure 3-6
(1992);
of 9.4 x
10 x
more than $50
EMR
m\
World's crude
oil
production.
1
965- 991.
1
Source:
British
Petroleum
(1993).
The United
billion
worth of
States relies heavily on foreign supplies
oil in
and imported
1991.
Western European nations and Japan are large consumers of
oil
products as well.
Except for the United Kingdom and Norway, with their newly discovered deposits under
the North Sea,
most of these countries
rely heavily
on imported
oil
obtained from for-
many of whom belong to the Organization of Petroleum Exporting
Countries (OPEC). The volumes of crude oil that each of the 13 OPEC members proeign producers,
duced
in
1991 are shown in Figure 3-8.
Comparing
this
with Figure 3-7,
it
will be
noted that the CIS, the United States, and Saudi Arabia are the three largest producers.
Mexico
10
3
is
the largest
mVday.
non— OPEC
oil-exporting country, with a 1991 output of
472 x
56
Energy Growth
Chapter 3
3.0
]
Consumption
]
Domestic Supply
2.0 -
1.0
V.
o
O
r
V\
Figure 3-7
World's principal consumers of
oil
and
their
domestic supply of
oil
products
in
More
than
45%
of the crude
oil
requirements for the world (excluding the CIS,
Eastern Europe, and China) was provided in 1991 by
that output
came from
bia, Iraq, the
the six
members of
OPEC
OPEC
countries.
Nearly
oil reserves,
is
Middle East extends
of
Nature has favored them
nearly 20 times larger than
those remaining in North America, for example, as illustrated in Figure 3-9.
quently, the impact of the
62%
located in the Middle East: Saudi Ara-
United Arab Emirates, Kuwait, Iran, and Qatar.
with large, easy-to-recover conventional crude
present
1991
British Petroleum (1992).
Source:
far
beyond
its
Conse-
population, which at
fewer than 50 million people.
Saudi Arabia, with a population below 10 million, has the greatest influence in
OPEC
because
it
is
potential of, the 13
by
and pricing appear
tion
may
far the largest
to be the
ing
for
Western countries,
most moderate.
its
policies
In general, however, the
on produc-
Middle East
be unstable politically and subject to the ever-present threat of local conflicts,
which have the potential of escalating
was
producer among, and has the largest production
members. Fortunately
the
into military confrontation.
A
recent example
August 1990 invasion of Kuwait by Iraq and the subsequent Gulf War, involv-
many
nations around the world.
57
Current Consumption of Energy
Sec. 3.2
1500
=
1000
/
a
500 -
*
Y\
V\
m
I.
i
V\
Figure 3-8
Production of crude
in
oil
OPEC
countries in
v\
v\
1991.
^
v\
Source:
British
Petroleum (1992).
Unquestionably, access to the
economic health of
on
consumers,
oil
the
oil
resources in the Middle East
Western world.
first in
essential for the
is
Meanwhile, the price shocks imposed by
1973-1974, and again
in
1979-1980, resulted by 1981
than a 10-fold increase in current dollars in the world price for
oil,
as
shown
OPEC
in
in
more
Figure
This heavy economic burden has led oil-dependent nations to search for energy
3-10.
alternatives,
on the one hand, while attempting
to
curb existing appetites, on the other,
even though prices have since fallen back close to $135 per cubic meter (see Figure
Efforts to reduce oil
3-10).
consumption have been particularly apparent
of the Western world, as indicated
they were, and
still
are,
in
Table 3-5.
Some would
excessive users.
portion of the reduction
was due
increases in the price of
oil in the
to
for oil
It
is
and
plain
its
countries
argue, however, that a significant
decreased economic activity brought on by the huge
1970s.
Other contributing factors have been the con-
version to cheaper energy forms and measures to conserve energy.
mand
in
This might have been expected, since
As
a result, the de-
price per barrel have decreased significantly since 1980.
from Table 3-5
veloping areas of the world are
that the
still
at
growth
rates in
high levels.
consumption
Such
in
statistics are
many of
the de-
somewhat mis-
58
Energy Growth
Figure 3-9
Source:
Total discovered
Chapter 3
oil.
British Petroleum (1992)
leading, however, because populations in the developing areas are increasing annually at
a rate about four times higher than those in the developed countries, and per capita en-
ergy consumption
is
much
rope consumed more crude
East combined.
less in the
oil in
underdeveloped areas.
For example. Western Eu-
1991 than did Africa, Latin America, and the Middle
The disproportionately high growth
rate in the
poorer countries and the
excessive consumption by the richer nations will impose severe economic and environ-
mental pressures on the world community during the coming decades.
Sec. 3.2
59
Current Consumption of Energy
TABLE 3-5 CHANGES IN OIL
CONSUMPTION (%) IN SELECTED
AREAS AND COUNTRIES
1991 over 1979
Country/area
United States
-10.8
Canada
Latin America
-17.0
OECD
-13.9
+23.9
Europe
-6.7
Japan
+103.1
Middle East
+47.8
Africa
CIS
1.6
+29.4
China
Source:
Petroleum (1992).
British
250
TO
CO
<D
Q.
c/j
1990
1985
1980
1975
1970
Year
Figure 3-10
NEB
Average cost
(1991, 1992).
ol
crude
oil
imports
in
Canada.
Sonne:
EMR
(1987)
60
3.3
Energy Growth
Chapter 3
FUTURE CONSUMPTION AND AVAILABILITY
OF ENERGY SOURCES
War
After the end World
II,
As
generating stations.
to the possible
maximum
the period 1950-2050.
The
was
demands for energy extending over
(Putnam, 1953) still make for fascinating reading.
of a hypothetical world trustee whose task was to
plausible world
results
cast himself in the role
and describe those contingencies
identify
the subsequent 100 years.
timate the
maximum
According
to
development and use of nuclear
a result, in 1949, Palmer Putnam, a consulting engineer,
asked to investigate the
The author
Atomic Energy Commission became concerned
the U.S.
about public policy problems related
One
could affect energy consumption during
that
important component of the overall equation was to es-
world population prior to predicting the requirements for energy.
Putnam's carefully projected
results, the
world's population could grow to
2.9 billion in 1975, 3.7 billion in 2000, and 6 billion in 2050.
lation has
grown considerably beyond Putnam's
At the time of the forecast
According
to recent
U.N.
will top the 6 billion
in
In fact, the actual
popu-
forecasts.
1950, the world population was about 2.3 billion.
data, the population reached the 5 billion
mark by 1998. Most of
mark
in
1987 and
the unanticipated increase occurred in the
developing countries, primarily because of a significant decline in infant and childhood
mortality, as discussed in Chapter 2.
ited
by
It
now seems
likely that the
world will be inhab-
9 billion people by 2050 (see Figure 2-8). The demands of such a large
at least
populace on the world's energy resources will tax the ingenuity of those charged with
resource recovery and the conversion of wastes to useful forms of heat and power.
Energy consumption has been predicted
tween 1985 and 2060, as shown
by then
ing
how
will
this
in
Figure 3-1
be larger than the world's
total
to
1.
more than double or even triple beThe uncertainty in energy needs alone
consumption
huge future demand might be met
is
in 1991.
One
estimate outlin-
depicted in Figure 3-12, with coal
playing the dominant role as an energy source in the twenty-first century.
Serious envi-
ronmental problems from gaseous emissions will have to be solved, however, before
coal can be burned on the scale envisaged in the figure
if
a safe environment
is
to be
preserved.
Future energy growth rates in the less developed regions, sometimes referred to as
the South (Asia, Africa, Latin America),
may
be nearly double those
in the
more devel-
oped regions or North (North America, Europe, CIS, industrialized countries of the Paas shown in Figure 3-13.
Nonetheless, levels of energy
2060 could still be seven times lower per capita in the South than in the
North (Frisch. 1986). The dominant sources of energy in the South in the early decades
of the next century will be oil and hydroelectric power (see Figure 3-14), simply because nature has provided that part of the world with a greater endowment of these recific,
South Africa),
consumption
in
sources.
External
demand from
the North for oil supplies will be particularly severe as the
more and more of its indigenous deposits internally. Thus pressures
will develop in the North to find economic substitutes for ever-more-expensive and diminishing quantities of crude oil. The available production data support the suggestion
South moves
to use
Sec. 3.3
61
Future Consumption and Availability of Energy Sources
1500 —
/
"55"
©/
o
(E:
/
oo
.
/
Projections
Consumption
©A ©
W
Annual
oo
©,
/%\ Average Annual
i
1960
1980
Growth Rate
Each 20 Years
i
I
I
2000
2020
2040
Figure 3-11
2060
World primary energy
production. Source:
Frisch, by permission
of the World Energy Conference. 1986.
Year
Coal
Natural
Gas
Nuclear
New Sources
Petroleum
Hydroelectric
Noncommercial
Energies
1960
1980
2000
2020
2040
2060
Year
Figure 3-12
ihe
Evolution
oi
world energy supplies.
World Energy Conference. 19X6.
Source:
Frisch, by permission of
62
Energy Growth
Chapter 3
- 300
Q.
o
Q.
03
O
D"
LU
200
O
Q.
E
o
O
a.
E
c
o
100
O
<
c
<
1960
1980
2000
2040
2020
2060
Year
Figure 3-13
Levels of energy consumption.
Source:
Frisch,
by permission of the
World Energy Conference, 1986.
that
world
oil
output
may
already have peaked, in about 1979.
since 1970 indicate that the Western world
oil
price rises in
were
illustrate the
proven reserves of
oil
rates,
we need
only to note that the
whole of Western Europe, principally those under the
North Sea, would be needed to supply
tion in 1991.
OPEC-induced
the countries of the Eastern Bloc
from Figure 3-5.
magnitude of the production
for the
Oil consumption figures
seriously affected by the
1973-1974 and 1979-1980, whereas
relatively unscathed, as is evident
To
was
little
more than seven months of world consump-
Furthermore, the North Sea discovery was one of only three major finds
made in the world during the past 20 years, the others being in Mexico and at Prudhoe
Bay in Alaska. We face the clear prospect, therefore, of a decreasing contribution of oil
to the world's
way through
primary energy needs.
the next century, after
Natural gas could reach that position as well mid-
which time the quantities of
oil
and gas recovered
Sec. 3.3
63
Future Consumption and Availability of Energy Sources
Oil
E?
<5
m
c
CD
c
I
-,
<5
a.
Nuclear
Figure 3-14
Energy production
developed regions. Sonne:
2020
1978
in less
Frisch,
by
permission of the World Energy
Conference. 1983.
are expected to drop as deposits are exhausted.
portance as sources of energy
possible to meet the energy
major increases
in
in
Now,
if oil
and gas are
to decline in im-
the twenty-tirst century and beyond,
demands of
energy production are
how
will
it
a still-growing world population? Clearly,
to
be achieved, they must
come from
nuclear sources; the renewables, hydroelectric energy, and unconventional
be
if
coal and
oil
and gas,
(primarily from sands and shales), will be important also, but not nearly to the
same ex-
tent.
Similarly, potentially
not expected to
make
a
More economical and
lar
—
is
likely to
new
sources, from thermonuclear fusion, for example, are
major contribution
efficient use
to the world's
medium
— nuclear power
in particu-
be achieved during the next 40 years by the development of energy
storage techniques which will permit reactors to operate
storage
energy needs before 2050.
of energy sources
is
at
higher outputs.
hydrogen, produced by the electrolysis of water. Another
from the development of materials which become superconducting
at
One such
may result
liquid nitrogen
temperatures and above.
The greatest single fossil fuel resource available is coal, as indicated
The resource/demand ratios for both coal and uranium tabulated in this
comfortably
large.
However, as indicated
in
in
Table 3-6.
table appear
Figure 3-11, utilization of these two
re-
64
Energy Growth
sources could grow markedly during the coming decades.
measured
particularly for uranium, might be
once
in
Chapter 3
Thus resource/demand ratios,
However,
decades rather than centuries.
breeder reactors and advanced thermal reactors are substituted for current ther-
fast
mal reactor designs, known uranium and thorium resources
will be utilized
more
effec-
and the energy contribution from nuclear power should be increased 50—
tively
60— fold.
Nuclear fission would then provide considerably more energy
than that available from
TABLE
all
remaining
fossil fuel resources.
WORLD NONRENEWABLE ENERGY RESOURCES
3-6
Source
Proved
World demand.
Resource/demand
resources (EJ)
1985 (EJ)
ratio
Coal
102.1
393
125.8
39
3,314
69.0
48
64
15.2
77
40.123
Crude
to
in the future
4,344
oil
1
582
Oil sands and shales
j
Natural gas
Uranium
•'
1
.
1
'Current thermal reactors.
British Petroleum (1986): Frisch (1986).
Source:
An
important factor influencing the future use of energy sources
mental and social impact of each source.
is
the environ-
This applies particularly to the use of coal
and nuclear power. The hazards of mining and transporting huge quantities of coal, and
the disabilities, such as black lung disease, generated in miners, are important consider-
The environmental damage incurred by exhausting
ations.
into the
growing quantities of residues from the burning of coal may place
Although the removal of
that fuel.
sulfur-
atmosphere ever-
limits
on the use of
and nitrogen-containing gases from the com-
bustion process offers the greatest technical challenge, reduction in heavy metals in
scrubber effluents
concerns
is
also an important task.
in its potential
creasing the
CGs
all
is
content in the atmosphere (see Chapter
Nuclear power
benign of
Then, looming over
impact on the world's climate
is
considered by
energy sources
in
many
all
such environmental
the effect of significantly in5).
technically-trained people to be the most
terms of environmental impact.
Others, however, are
fervent campaigners against the nuclear option, claiming that the potential dangers from
low-level radiation hazards, nuclear accidents, and the proliferation of nuclear
render
it
intolerable as a future source (see Chapter 15).
risks associated with their production.
Many
weapons
Other energy sources also have
of these problems are environmental
in
nature and are considered further in the following section as well as in other chapters.
3.4
ENVIRONMENTAL IMPACTS OF ENERGY DEVELOPMENT
Having examined the
sumption,
we
past, present,
and future patterns of energy production and con-
turn to a discussion of the environmental impacts of these technologies.
65
Environmental Impacts of Energy Development
Sec. 3.4
Many books and
reports have been written
on the environmental impacts of energy de-
Most discussions of energy technology and
velopment.
environmental aspects, since
it
can constrain energy production, especially when the environment
Most
texts
an account of
politics include
generally recognized that environmental considerations
is
exposed to
risk.
air pollution
from
is
on environmental issues contain sections on topics such as
automobiles and power plants, thermal pollution from power plants, and water pollution
Some books and
from
oil spills.
more
detail include those
(1973).
in the
It
sue.
The matrix format of
Biswas volume
is
is
(1) a
listing the
impacts of energy on environment developed
followed here.
useful to discuss
These are
reports that explore the energy-environment issue in
by Fowler (1975), Tuve (1976), Chigier (1981), and Biswas
some
first
recurring themes in the energy-environment
comparison of current energy use
"background" of solar radiation
that
we
as food for survival; (2) the
volumes of
changing picture of energy
availability;
receive and with the
fuels that
and
we
is-
an industrial society with the
in
minimum energy
necessary
generate, process, and use; (3) the
(4) the issue of toxic substance dispersion
from energy development.
Background
of solar radiation
and food energy.
Commercial energy
consumption by society can be compared with the background of energy received
through solar radiation and the
ple follows, and
it
is
minimum food energy
specified country or region (see
Example
necessary for survival.
An exam-
suggested that the reader undertake a similar calculation for a
Problem
3.10).
3.1
Compare and discuss the energy consumption or flow
gawatts (GW), and watts per person as fuel, food, and
ulation density
rate of
150
20 persons/km 2 an area of
,
250 GJ per person per
W/m 2
calories)
1
million
rates in units of joules per year, gi-
solar radiation for a country of pop-
km 2
,
and a
fuel
energy consumption
Solar radiation reaching the ground
year.
The average person consumes food containing 2000
per day [1 (kilo) calorie = 4182 J],
is
approximately
"calories" (actually kilo-
.
Solution
Fuel energy:
Total energy (J/yr)
=
250 x
=
5 x 10 18 J/year.
l()
(Energy
J/s
=
watts
y
is
(J)
5 *
1
59 x 10"
_
= L2ZJL22L_
h
20 x 10
'°
^ ec
, nn
365 x 24 x 3600
I
Watts/person
)
x 10 6 (km 2
usually expressed in watts
(W)=
{
x 20 (persons/km 2
7950
=
=
)
J/s)
1.59 x
10"
W
=
159
GW
66
Energy Growth
Chapter 3
Solar energy:
Total energy (watts)
=
=
1.5
=
150.000
J/yr=
=
14
x 10
x 10 6 (m 2 /km 2
)
)
x 10 6 (km 2
)
W
GW
x 10 14
1.5
x 3600 (s/h) x 24 (h/day) x 365 (days/yr)
(J/s)
4.7 x 10 21 J/yr)
—
5
i
=
Watts/person
H
(W/m 2
150
x in 14
-^—
=
20 x 10 6
7.5 x 10 6
Food energy:
J/yr
=
person) x 4182 (J/"cal")x 365 (days/yr)
2000 ("car/day
x 20 x 10 6 (person)
i-,
.
Watts/person
=
6.1
=
9
1.94 x 10 J/s
=
x 10 6 J/yr
1.94 x 10 9
=
(W)
=
;
20 x 10 6
'
1.94
GW
97
Summary:
GW
J/yr
Watts/person
5 x
10' 8
159
Solar
4.7 x
10 21
150,000
Food
6.1
Fuel
Comments:
Note
x
l()
lh
7950
7.5
Human
1
x 10 6
943
0.012
97
1.94
that the population density
used
in this
example, 20 persons/km 2
typical of the United States, about one-tenth that of the United
of Canada.
Ratio
Kingdom and
energy needs are small compared to solar radiation, but
,
is
10 times that
it
is
the
wide
Food energy needs
are very small, although each person is generating nearly the same heat as a 100-W bulb.
The fuel energy consumption of 7950
(7.95 kW) is 80 times the food consumption, thus leading to statements that "modern industrialized man has the equivalent of 80
dispersal or "dilution" of solar energy that
makes
it
difficult to exploit.
W
energy slaves".
If the
population density increases by 100 times or more (as
eas) fuel and solar energy flows
insolation in winter.
ies are often
The
in
Obtaining
in
urban
ar-
Hence winters
in large cit-
suburbs.
potential for environmental disruption by energy-related
can also be elucidated by calculating the
person per year.
may occur
equal, particularly during low rates of solar
This leads to local climatic modifications.
milder than those
Fuel volumes.
activities
become more
this
mass of
mass or volume of fuel used by each
it from other undesired materi-
fuel, separating
als,
67
Environmental Impacts of Energy Development
Sec. 3.4
transporting
it,
and eventually burning
all
it
have environmental impacts. Table 3-7
indicates the energy densities of selected fuels in units of
By energy
density
we mean
MJ/L (megajoules
the amount of energy contained
a unit
in
or 10 6 J/L).
volume of
the
fuel. Coupling this to per capita energy use shows that we are each responsible for the
production and movement of a considerable volume of energy-related materials annu-
MJ/yr, which corresponds to over 10,000
ural gas. or
it
may "consume"
For example, a resident of an industrialized country
ally.
oil.
6000 L of
coal,
1
1
million
L of
nat-
45,000 L (45m 3 ) of wood.
These volumes are substantial, especially when
may require the removal of other material (e.g.. rock
noted that obtaining the fuel
is
L of
400.0()()
mining).
in coal
TABLE
ENERGY DENSITIES
3-7
OF SELECTED FUELS
Energy density (MJ/L)
Fuel
Natural gas
0.036
35
Oil or gasoline
(petroleum)
Coal
65
(solid)
Wood
9
Although each stage from extraction
ticular
problems
arise
of undesirable materials, such as sulfur.
coal or oil
ide, are
is
to
5, 7.
with radioactivity
in these
itself,
only
in the
1
%
of the volume of
form of sulfur diox-
This creates major
and
par-
even small percentages
air
and
13.
fuels present a unique situation in that the
volumes
re-
However, the hazards associated
quired for energy production are exceedingly small.
materials counterbalance this small amount, since radioactiv-
an exceedingly potent "poison" (see Chapter 15).
Availability.
In the exploitation of
energy resources, there has been
an understandable tendency for industrialists to exploit
est,
if
of sulfur, usually
emitted into the atmosphere following combustion.
Uranium and other nuclear
be disruptive in
fuel contains
For example, even
sulfur, considerable quantities
water pollution problems, as discussed in Chapters
ity is
may
marketing
from combustion when the
and
least
contaminated energy sources.
first
These sources lead
Rightly or wrongly, less desirable sources tend to be
left
in the past
the cheapest, closest, richto
maximum
protit.
for future generations.
Ac-
cordingly, rich coal seams and abundant oil supplies close to the surface and low in sulfur tend to be exploited
first
to be developed:
first;
uncomplicated and nearby hydroelectric schemes were the
onshore petroleum has been preferred
to offshore;
where
available,
natural gas has been used as an energy source in preference to coal or coal gas;
cheap imported
A
oil,
when
general consequence
is
it
is
available, has
that future
been preferred
energy supplies
may
to
expensive domestic
(1) tend to
and
oil.
come from more
remote areas, incurring longer transportation distances; (2) be more contaminated with
undesirable elements; and (3) be more "dilute"
(e.g.,
coal seams
may be
thinner or oil
68
Energy Growth
Also, the fossil fuels exploited
production rates lower).
thus be
more
and expensive
difficult
to find
may
and produce.
deeper
lie
In total,
it
Chapter 3
in the earth
and
likely that future
is
energy developments will be more environmentally disruptive and will often occur
in
areas that have traditional competing uses, such as fishing, agriculture, and tourism.
These areas may be populated by people who have a
light
lifestyle that results in relatively
who
energy demands compared to the industrial urban energy system and
under-
standably resent the intrusion of energy developments into their "backyard."
Toxic substances.
In 1962, Rachel
Carson published her now classic book
Silent Spring, an account of the adverse effects of pesticides, used largely for agricultural purposes,
on nontarget organisms (or victims) such as
Since then wide-
birds.
ranging concern has developed, about the dissemination of toxic substances throughout
These may be metals such as lead or mercury, organics such as
the environment.
or
PCBs
The
or radioactive materials.
there
may be
or asbestos,
toxic effects are, fortunately, rarely lethal to
humans, but
or sublethal effects on other organisms; resulting in ecological
lethal
For example, there may be loss of reproductive capacity
changes.
DDT
compounds
(polychlorinated biphenyls), inorganics such as sulfur
behavioral changes affecting predator— prey relationships.
It
in fish or birds,
may
observe the natural environment closely for change, since a toxic effect on birds
act as a
warning of a potential human
effect.
We
same biochemical building blocks.
The energy industries handle considerable
stances, for example,
tion of oil
and
or
thus prudent for us to
is
are, after all, constructed
quantities of these
from the
hazardous sub-
uranium for nuclear fuels and sulfur compounds from the combus-
Of
coal.
particular concern
Examples
mutations or cancer.
is
the generation of substances that induce
are polynuclear aromatics, such as benzopyrenes, and
various heterocyclic organic compounds, which include the elements nitrogen and sulfu..
These compounds may be produced during combustion or
thetic liquid fuels
from
change from gasoline
They
coal.
to
are present in exhaust
diesel-powered automobiles, which
energy viewpoint, can cause increased adverse health
and
In the past, engineers
scientists
in the synthesis
of syn-
from diesel engines; thus any
may
be desirable from an
effects.
have often failed to predict, and thus to con-
health.
new energy developments on the environment and on human
Hydroelectric dams have caused fish kills and siltation, sulfur dioxide has
harmed
forests
trol,
the adverse effects of
and
lakes,
levels of radioactivity.
tried
mechanism
excuse, however.
now
and uranium mine
tailings
for assessing future environmental impacts.
Practical techniques
and
(in
many
exist to ensure that these avoidable impacts
minimized (see Chapter
One approach
16).
ces in which
we examine, on
tivity, in this
case, the energy development,
what the impacts
have produced undesirably high
These mistakes are partly excusable
will be of
ponent of the environment.
is
to
was no
in that there
No
longer do
countries) regulatory
do not occur, or
well-
we have
this
mechanisms
at least that
they are
compile environmental impact matri-
the one hand, the environment and,
and ask
on the
other, the ac-
in a systematic, exhaustive
manner
each component of the energy development on each com-
We
use this approach in the next section.
Sec. 3.5
3.5
69
Environmental Impact Matrices
ENVIRONMENTAL IMPACT MATRICES
The environmental impact matrix was introduced
Chapter 2 and again provides a
in
convenient inventory and display of the impacts of energy production (Leopold et
al.,
As illustrated in Table 3-8. the matrix is compiled with the horizontal axis listing the components of the development, such as exploration, mining, transportation, or
utilization. On the vertical axis are components of the environment: the atmosphere, the
hydrosphere, the lithosphere. and human impacts. The matrix indicates potential inter1971).
actions between activities and the environment and provides answers to such questions
Does
as:
oil
exploration affect water quality? (Answer: yes, by
oil spills.)
Or does
the
use of hydroelectricity affect air quality? (Answer: probably no.) With the methodical
matrix method, potential impacts are not likely to be overlooked.
In the
we
matrices adopted
in this section for the
environmental impacts of energy,
use four columns and four rows.
•
Column
1.
production.
This includes the search for fuel sources prior to any
Exploration.
Exploration
often unsuccessful and possibly earned out in remote
is
areas in competition with other uses of the land or water.
TABLE
3-8
ENVIRONMENTAL IMPACTS OF
OIL
Type of
activity
Extraction,
production.
Environment
Atmosphere
Exploration
H: S
and hydrocarbons
Emissions of
as a result of a
blowout
Hydrosphere
BLOWOUTS AND
SPILLS FROM
EXPLORATORY
WELLS AT SEA.
LEADING TO
OILCONTAMI
processing
Transmission
—
Refinery emissions
Use and disposal
Emissions of
SO :
.
of SO,, H,S.
COi. and hydro-
CO
carbons
NO,, and
:
hydrocarbons
.
BLOWOUTS AND
SPILLS Brine
TANKER
ACCI-
DENTS, LEADING TO OIL
and drilling
chemicals dis-
CONTAMINA-
posal
TION
Groundwater contamination by
leaking tanks
Refinery effluents
NATION
Lithosphere
Blowouts and
on land
spills
Blowouts and spills
Sludge disposal
Pipeline construction
and
Damage
to
Used
oil
disposal
spills
perma-
frost
Human
impacts
Disruption of
style
life-
Interference with
fisheries
Interference with
Hydrocarbons and
fisheries or land
polynuclear aro-
use
matic hydrocar-
Disruptions of
st) le
lite-
during con-
struction
bons from
combustion
70
Energy Growth
•
Column
2.
the fuel
from
Extraction, Production,
and Processing. This includes
Chapter 3
the removal of
present location by mining, drilling wells, constructing dams, re-
its
fining the fuel (eg., in an oil refinery),
and
in the
case of electricity generation, the
production of thermal effluents.
Column
•
3.
Column
•
4.
This
Transmission.
by pipeline, road,
site
is
the transportation of fuel
from
production
its
tanker, or electricity transmission line to the site of use.
rail,
Use and Disposal.
This includes the generation of products of com-
bustion, spent fuels, and oxides of sulfur, nitrogen, and carbon.
Note
gas
ral
Row
•
do not necessarily occur
that the processes
For example,
is
oil is
remove
extracted, processed to
order just given.
and then transported.
sulfur,
This includes the immediate atmospheric environment
Atmosphere.
I.
in exactly the
usually extracted, transported, and then refined, whereas natu-
around the development and the impact of the long-range transportation of pollutants, especially
when
tall
more widely
stacks are used to disperse the pollutant
in
an attempt to solve a local problem by dilution.
Row
•
ter
Hydrosphere.
2.
— and
This includes fresh water
We
the oceans.
bacteria to fish and marine
Row
•
3.
lakes,
soil,
rock, and bottom sediments of rivers,
and oceans, including the attendant vegetation and animal
In the three categories
above,
we have
We
the environmental impact.
and groundwa-
rivers, lakes,
mammals.
This includes
Lithosphere.
—
also include biota indigenous to the water, ranging from
life.
included the resident biota as potential victims of
give special consideration to
human impacts
in the final
category.
Row
•
4.
Human
Impacts.
This includes
human
welfare in
its
broadest sense, in-
cluding effects on health, the economy, security, lifestyle, social structure, and
aesthetic considerations.
The impacts with
Some
the greatest severity are capitalized in Tables
3-8 through 3-12.
impacts are "chronic," with continuous emission and a continuous effect
(e.g., oil
refinery wastewater discharge), while others are occasional and accidental, with a
sive effect,
spill).
which may occur once
in five
Comparing these fundamentally
years and last for a few months
mas-
an
(e.g.,
oil
different impacts is challenging.
3.5.1 Environmental Impacts of Oil
Figure 3-8 gives the environmental impacts of
shore or offshore, there
is
a risk of
oil.
During
oil
exploration, either on-
blowout should control of the well be
lost.
This can
lead to severe and prolonged oil spills, which are harmful to the marine environment.
The 1979
Ixtoc blowout in the Gulf of
Mexico
is
an example.
blowout can take considerable time and often requires
the oil flow.
tion
This problem
is
Regaining control of a
drilling a relief well to interrupt
particularly severe in northern climates,
and movement may seriously impede or even prevent drilling of
where
ice
forma-
relief wells.
may
Oil spills
in
71
Environmental Impact Matrices
Sec. 3.5
result in mortality to birds
and contamination of shorelines, resulting
severe biological effects on intertidal and nearshore organisms, including valuable shell
There may also be fouling of vessels,
fisheries.
The impact of
pensive cleanup.
assess, but
likely that the spill will
is
it
organisms present
viewed
in the
nets,
and harbor
more
is
have some effect on fisheries and,
ocean surface waters.
The
difficult to
in general,
on
been
re-
issue of oil pollution has
number of books, including those by Nelson-Smith (1973) and Matins
in a
Exploration, production, and transmission activities
remote areas.
lifestyles in
traditional
requiring ex-
facilities,
on the open ocean environment
oil
modern
pressures of
There
is
For example,
communities
Inuit
—
in
northern
may have
(
1977).
a profound effect on
Canada and Alaska
—
especially in
people are not well equipped to withstand the social
industrial life.
on land prior
also a risk of spillage during oil production and collection
petroleum
to its transmission to
refineries.
At these refineries there
a potential for
is
emission of hydrocarbons, sulfur oxides (SO,), which can cause lake acidification and
human
respiratory problems, hydrogen sulfide
(H 2 S), which
highly toxic and odorous,
is
(CO : which may lead to the "greenhouse effect" (see Chapter 5), oxides of nitrogen (NO
which cause photochemical smog and acidification, and some
odorous substances. Refineries also generate liquid effluents that may contain hydrocar-
carbon dioxide
).
).
v
bons, phenols, ammonia, and other toxic substances.
ents are
Dissolved organics
normally treated by biological oxidation processes, and
oil
in these efflu-
is
removed by
Sludges are inevitably formed which consist of mixtures of hydro-
physical separation.
carbons and organisms often contaminated with metals, particularly nickel and vana-
dium, which are usually present
During
local
ten
oil
environment by
is
crude
oil
formation
oils.
potential for
is
drilling chemicals,
produced from the
Oil
in
production, there
in
damage due
muds, and brine
to
contamination of the
(a salt solution),
association with the crude
which
is
of-
oil.
transported both by tanker and by pipeline in very large quantities, and nei-
ther of these
immune from
is
causing environmental pollution.
In fact, there
have been
several impressive oil tanker accidents resulting in widespread contamination of coastal
regions, notably the Torrey
nel.
The
Canyon and
the
Amoco Cadiz
effects are generally similar to those of
incidents in the English
blowouts discussed
leases from pipelines are usually less severe because the oil
although there
special
may
problem
is
easily controlled,
A
the construction of pipelines for transmission of oil or natural gas in
Normally,
power requirements.
oil
is
is
pumped
underlain by permanently fro/en ground, called
hot to diminish
its
viscosity and thereby reduce
Therefore, the pipeline must be well insulated to prevent the
ground from thawing, which could
common
more
ChanOil re-
be fouling of agricultural land, leading to loss of productivity.
northern climates where the ground
permafrost.
is
earlier.
engineering practice
is
quate insulation, thus separating
result
in
land subsidence, called thermokarst.
to build the pipeline
it
on
piles, or in
from the vulnerable ground.
The
A
trenches with adefirst
of this type was the trans-Alaska pipeline from Prudhoe Bay to Valde/.
major pipeline
Such pipelines
often pass through sparsely populated wilderness areas where the construction activities
can have severe impacts on local
A
lifestyles, fisheries, trapping,
controversial and as yet unresolved issue
is
that
and land use generally.
of the possible interference with car-
72
Energy Growth
may
ibou migration by aboveground pipelines, which
these animals in northern
The use and disposal of crude
Some
all
oil results in
emissions of hydrocarbons and oxides
may
cause environmental and health prob-
of which
of the hydrocarbons produced during incomplete combustion are polynu-
clear aromatics such as benzopyrenes,
is
which are potential carcinogens.
In principle,
it
is
obviously desirable to reprocess this
hydrocarbons and eliminate
fill
this
A
final
impact
which may be contaminated with
the disposal of used oil, particularly lubricating oil,
lead.
effectively present a barrier to
Canada and Alaska.
of sulfur, nitrogen, and carbon,
lems.
Chapter 3
source of pollution, but
it
oil to
recover the valuable
often disposed of in land-
is
sites.
3.5.2 Environmental Impacts of Natural Gas
Table 3-9 shows the environmental impacts of natural gas.
is
readily apparent that
oil.
leases of natural gas (methane) into the environment
minor, provided that there
accompanying
phere, having
TABLE
It
these impacts are considerably less severe than those of
3-9
fire
little
or explosion.
The methane tends
is
Generally, the impact of re-
to dissipate rapidly into the
no
is
atmos-
adverse environmental effect.
ENVIRONMENTAL IMPACTS OF NATURAL GAS
Type of
activity
Extraction,
production,
Environment
Atmosphere
Exploration
Gas
Emissions of gas
and H 2 S during
an accidental
blowout
Hydrosphere
Transmission
processing
Blowouts
Emissions of
plant emis-
sions of
Use and disposal
H 2 S,
C0 2
,
NO,
SOt, and hydrocarbons
Blowouts and
drill-
ing
Disposal of chemicals
Lithosphere
Construction of
pipeline
Damage
to
perma-
frost
Human
impacts
LNG ACCIDENTS
LNG ACCIDENTS
H2 S
Disruption of
emissions
style during
life-
con-
struction
Again, there
more severe
is
is
a risk of emission of
the risk of
hydrogen
sulfide
hydrocarbons during blowouts, but probably
(ITS) emissions during exploration and pro-
Hydrogen
duction.
ervoirs,
which normally accompanies
The usual procedure is to remove
sulfide,
highly toxic.
is
methane
at a "gas plant" close to the well.
H
sulted in severe
with
73
Environmental Impact Matrices
Sec. 3.5
there
oil,
natural gas in petroleum res-
the hydrogen sulfide
from the
Repeatedly, gas plant malfunctions have re-
S emissions, requiring rapid evacuation of large areas downwind. As
2
an impact from the disposal of brine and drilling chemicals.
is
construction of gas pipelines can be disruptive and
may be
Also,
particularly difficult in the
permafrost regions.
One
area of increasing concern
the possibility of severe accidents occurring as
is
a result of transportation of liquefied natural gas
port gaseous natural gas
the cargo, permitting
at
more
very low temperatures
pressures.
to be carried per voyage.
(i.e.,
which then evaporates very
and explosion are
is
fails,
not economical to trans-
These cargoes must be maintained
for
hazardous condition
There have been several
LNG
example, loss of an entire cargo.
fires,
elevated
a compelling incentive to locate these facilities far
from human
which
in
fire
but fortunately
Extreme care
designing the liquefaction, transportation, and gasification
in
at
there will be emission of the liquid methane,
rapidly, creating a highly
likely to occur.
no major incidents involving,
essar)
It is
below the boiling point of natural gas) or
containing vessel
If the
(LNG).
by tanker; liquefaction greatly increases the energy density of
is
nec-
and there
facilities,
habitation.
3.5.3 Environmental Impacts of Coal
The environmental impacts of coal are presented in Table 3-10. Normally, coal is recovered by one of two processes. In strip mining, coal that lies close to the surface is
removed by earth-moving equipment, the overburden of soil being removed and stored
for later replacement. The area can then be filled in and revegetated after the removal
of the coal.
mining for deeper deposits with substantial quantities of sulfur and
In
compounds which have remained inert in their subsurface environment throughout
geological times, exposure of the mined minerals to oxygen and water initiates a series
metal
of reactions, particularly oxidation and dissolution, which were previously not achievable.
The
result
is
the formation of oxides of sulfur (and hence sulfuric acid), metal so-
phenols, and various other compounds,
lutions,
harmful.
Coal
piles
many
of which are environmentally
and slag heaps thus can generate considerable quantities of these
substances, and the leachate must be controlled and prevented from entering surface waters or
groundwaters.
An
important
coal mines.
human
issue
is
of the safety and health of those working
that
in the
Problems of mine safety are well known, and there have been many tragic
losses of life in underground accidents.
Less dramatic, but as devastating,
is
the severe
on human health by diseases such as black lung, which are caused by exposure of
workers to particulates or dust in coal mines.
toll
A
fuel
related
and growing concern
production from coal.
crude
oil
and natural gas.
Coal
is
*'coal
human exposure to the products of
many respects a more inconvenient
Conversion of the coal into a liquid or gaseous
in easier transportation, distribution,
duce
is
in
and
use.
synthetic
fuel than
fuel results
Traditionally, coal has been used to pro-
gas" (a mixture of carbon monoxide and hydrogen) in
many
countries, al-
74
Energy Growth
Chapter 3
ENVIRONMENTAL IMPACTS OF COAL
TABLE 3-10
Type of
activity
Extraction, production,
Environment
Exploration
Use and disposal
Transmission
processing
EMISSIONS OF S0 2 NOA
Emissions of SOi and
PNAs from processing
Atmosphere
,
C0
and particulates
,
2
to gas or liquid fuel
Coal dust dispersal
LEACHING OF ACIDS
AND METALS
Hydrosphere
Thermal
effects
Organic compounds
formed with
"synfuels"
Siltation
DISRUPTION FROM
STRIP MINING AND
SUBSIDENCE
Lithosphere
Fly ash disposal
Slag heaps
LUNG DISEASE
Human
Exposure to emissions from
combustion and coke ovens
MINE SAFETY
impacts
though
United Kingdom
in the
natural gas produced
it
has been displaced recently by the more convenient
from the North Sea.
Considerable research
is
under way into coal
gasification, a liquefaction process that usually involves high-temperature, often high-
During these processes,
pressure conversion of the coal into liquid or gaseous products.
the synthetic organic
compounds formed
often have structures that
cl: in biological organic material, and they can be very toxic.
do not normally oc-
Notable are polynuclear
many of
aromatic hydrocarbons (PNAs) and organonitrogen and sulfur compounds,
which have offensive smells.
in future
If
coal conversion to gas or liquid fuels plays a major role
energy economies, there
may
be significant environmental impacts resulting
from the formation and dispersion of these substances
into the air
and water environ-
ments.
As
ploited,
the
demand
and as
oil
for electricity increases
becomes
and hydroelectric
less available, there will again
used as a source of electric power.
This
may
result in the
sites
become
fully ex-
be a tendency for coal to be
emission of large quantities
of oxides of sulfur, nitrogen, and carbon, as well as particulate matter, into the atmospheric environment.
into the
downwind
this
regard
well established that emissions of sulfur and nitrogen oxides
is
regions, often
is
many hundreds
result in the acidification of
or thousands of kilometers distant.
Notable
in
the acidification of lakes in Scandinavia from emissions in Central Europe
(especially in the
State
It
atmosphere over a prolonged period of time can
Ruhr Valley) and
from major emissions
in the
the United
Kingdom, and
in
Ontario and
United States (from Ohio in particular).
vulnerable are lakes that have a low buffering capacity, that
amounts of natural alkaline material such
is,
as bicarbonate ion
New
York
Especially
which contain only small
which can neutralize
the
75
Environmental Impact Matrices
Sec. 3.5
acid that falls into the lake in rain or
discussed in detail
ification,
in
caused environmental problems.
vising systems for
snow or by dry deposition. The problem of acid5, is probably one of the most severe energy-
Chapter
A
considerable technical effort
removing sulfur from the coal or from the
is
being devoted to deUnfortunately,
flue gas.
these processes are likely to be very expensive.
The generation of
of the energy,
in the
electricity
from coal involves a
form of waste
heat,
loss of
from the generating
dissipated through both the flue gases and the cooling water.
water can result
lake or river
tions in
in
may
which
approximately two-thirds
plant.
The waste heat
"thermal pollution" of the local aquatic environment; for example, a
be subjected to an unusual temperature
a river
is
Most serious are situapower plants. Under
rise.
subjected to repeated heating by several
conditions of low flow, especially during the summer, the temperature of the water
rise
beyond
is
Discharge of the cooling
limits tolerable to aquatic life
medium
the use of air as a cooling
is
and
fish mortality
preferable, although
may
it
is
In
result.
generally
may
such cases,
more expen-
sive
3.5.4 Environmental Impacts of Hydroelectric
Development
Table 3-1
1
shows
the environmental impacts of hydroelectric development.
forms of energy production, hydroelectric power
disruptive, in the sense that there are rarely
sult
from changes
habitat,
and changes
in local
hydrology
In
some
—
probably the
any chemical
to the local region arising
of rivers and groundwater.
is
for
least
The major
effects.
Of
all
the
environmentally
effects re-
from submergence of land, loss of animal
example, alteration of flow characteristics
cases, there
may
be severe siltation problems.
In-
creasingly, remote hydroelectric sites are being sought, often in wilderness areas with a
sparse population
o\'
residents
who
rely
on trapping and a simple
loss of their land or the disruption of their lifestyle
TABLE
3-11
lifestyle.
To them,
the
can be devastating.
ENVIRONMENTAL IMPACTS OF HYDROELECTRIC DEVELOPMENT
Type of
activity
Extraction, production,
Environment
Exploration
processing
transmission
Atmosphere
CHANGES IN
FLOW CHARACTERISTICS
OF SURFACE WATER AND
GROUNDWATER
Hydrosphere
SILTATION,
Lithosphere
SUBMERGENCE OF LAND.
LOSS OF ANIMAL HABITAT
Human
Disruption of lifestyle from loss of
impacts
land
Transmission lines
Use and disposal
76
Energy Growth
Chapter 3
3.5.5 Environmental Impacts of Nuclear Power
Table 3-12
lists
the environmental impacts of nuclear power.
Paramount
is
the question
of environmental contamination by radionuclides as a result of mining, accidents involving discharge of fuel, failure of the nuclear reactor system, or contamination from spent
In the
fuel.
minds of many, the nuclear power issue
is
intimately, but irrationally, linked
with the horrors of Hiroshima, Nagasaki, and nuclear warfare in general.
No
other en-
vironmental issue has developed such widespread concern.
ENVIRONMENTAL IMPACTS OF NUCLEAR POWER
TABLE 3-12
Type of
activity
Extraction, production.
Environment
processing
Exploration
—
Atmosphere
Transmission
Use and disposal
—
—
Accidents
Radon emissions from
mine
Hydrosphere
tailings
Thermal
Accidents
Leachate from mine
effects
tail-
ings
—
Lithosphere
Accidents
Transmission lines
DISPOSAL OF SPENT
FUEL AND WASTE
Accidents during fuel
Exposure
Tailings contamination
—
Human
ACCIDENTS AND
MINEPLANT
impacts
to wastes
TERRORISM
transport
EXPLOSIVE MINING
HAZARDS
Except for the 1986 explosion
Chernobyl nuclear station
at the
maining few nuclear power plant accidents,
down
like the
in
Ukraine, the re-
Three Mile Island reactor break-
all resulted in very minor releases of radioactive
Even if the Chernobyl victims are included (31 deaths
at the time and an estimated 2000 extra cases of cancer in Europe over the next 50
years),* a much greater loss of life and damage to health can still be attributed to the
in
Pennsylvania
in
1979, have
material and no recorded deaths.
coal industry (see also Section 15.2.1).
There have been cases of undesirably high exposure of miners
terials,
both
sidual
but
disposed of
in the
mine and
low-level
in the
in
mineral processing.
radioactivity,
proper manner.
of or reprocessing spent
and
This fuel
fuel.
in
There
is
is
to radioactive
Also, mine tailings
may
ma-
contain re-
some cases these tailings have not been
much concern about the issue of disposing
highly radioactive and will remain so for cen-
Processing the fuel to ensure that this and future generations are secure from ex-
turies.
posure
is
a
considerable
sociopolitical challenge.
'Editorial,
London Free
A
technological
challenge,
worrisome aspect
Press,
is
but
possibly
an
even
greater
the possibility of terrorism resulting
London. Ontario, March 26, 1987.
-
from
a
77
Environmental Impact Matrices
Sec. 3.5
group of protesters obtaining quantities of radioactive material. As with the gen-
from
eration of electricity
Example
may
coal, there
on
a thermal effect
The disposal of nuclear wastes
ing purposes.
local water used for cool-
discussed more fully in Chapter 15.
is
3.2
A 100-MW
coal-burning electricity generating station operates
coal containing
5%
Assume
ash and 295 sulfur.
at
33%
efficiency burning
a coal heat content of 30kJ/g.
If
95%
of
the ash and 5095 of the sulfur are trapped before emission from the stack, calculate (a) the
emission rate
SO :
generated
to the
at
(in
C
(c) If the sulfur is
and atmospheric pressure,
area of stagnant air 500
m
km
high and 5
(A knowledge of Sections 6.3.2 and
r
Coal use =
a
x
l0° x
30 x 10'
l(,
"
J/s
emitted into an urban
would take
it
(parts per million
=1
Sulfur production
=1
x 10
x
4
x 0.05
=
4
x 0.02
= 200 g/s
1
500
SO
x in4
10 4 b
g/s
r,
1.0
/
!
x 0.33
Removed
Ash production
for the
by weight)?
required)
is
=
in g/s,
how long
ppm
6.4.1
;
J/g
SO,),
diameter,
in
concentration to reach the undesirable level of 0.3
Solution
and (b) the volume of
atmosphere of ash and sulfur
20
475
g/s
Emitted
25 g/s
g/s
100 g/s
100 g/s
The molecular weight of SO, =64. Therefore,
(b)
=
100 g/s SO,
From Equation
(6.41
Volume SOi
1.56
mol
I.
——- =
= nRT
1.56 (mol) x 8.314 (Pa mVmol
.„. „,^ ^
101.325 (Pa)
=
in
7s
air
=
P
0.037
Volume of
(C)
=
-£?
64
•
—
K) x 293(K)
-
500 x - (5000) 2
4
Concentration
ol
SO,
volume SO,
=
volume
Volume of SO,
„lime
.
for 0.3
,.,
to reach 0.3
ppm
" =
°" 98
ot air
x l0
volume SO,
,.„
ppm SO, =
Example
A
=
2.94 x I0 3
m
3
—=
(mVs)
:
Emission
=
°' 3
*
,
10"
rate
7.95 x 10 4
s
SO :
=
m
3
2.94 x 10 3 (m-1 )
0.037(mVs)
22 h
3.3
petroleum refinery processes
energy efficiency of 90%.
MJ/L.
The
1
()().()()()
oil
barrels of crude oil per
day and operates with an
and the petroleum products have energj contents
ol
55
78
Energy Growth
(a)
(b)
What
volume flows
are the energy and fuel
If oil is
supplied by a pipeline
in
which
and from
to
flows
it
at
Chapter 3
this refinery, in
J/day?
0.8 m/s, what pipe diameter
is
re-
quired?
(c)
stocks a 5-day supply of
If the refinery
oil (in
case of interruption of supply), what
be the storage tank volumes required? Suggest dimensions, assuming that the
will
tanks are cylinders of height half their diameter.
1
barrel of oil
159 L.
is
Solution
100,000 bbl/day
(a)
Product:
90,000 bbl/day
=
Energy
in:
out:
(b)
m
14,300
3
=
(at
159 x 10 5 L/day of
90%
90%
efficiency
The
pipeline flowrate
Q=
159 x 10 2 mVday.
is
=
Q =
=
and the diameter
D=
143 x 10
5
mVday
of
oil
L/day of product
5.01 x 10
14
5.57 10 14 J/day
J/day
=
uA, where the velocity u
Therefore, the area of the pipe
~
it
24 x 3600 (s/day) 0.8 (m/s)
m =
2
0.23
0.8 m/s and the flowrate
is
159 x 10 2 (nvVday)
2300 cm 2
54 cm.
The volume of storage tanks required
V=
Choose 10
=
159 x 10 5 L/day x 35 x 10 6 J/L
at
=
159 x 10 2
of product
Q_
(c)
efficiency)
=
oil
tanks, each of
for a 5-day supply of oil
x 5
=
volume 7950
m
159 x 10
2
7.95 x 10
3
4
and height
m
is
3
till.
Then
ml 2 J
volume of tank
4
2
Therefore,
d
=
7950 x
V
Thus 10 tanks 27.3
3.6
m
in
2 x 4
3/
K
diameter and 13.6
m
=
„
.
27.3
m
high are required.
CASE STUDY: CANADA'S ENERGY SITUATION
For nations to balance their energy needs with the energy supplies available will be-
come
sis
increasingly difficult in the future.
That
it
can be accomplished on a regional ba-
has been demonstrated by the Florida Power and Light Corporation, which serves a
large portion of the state.
On
a national scale, neither the United States nor
developed a comprehensive long-term energy policy.
serve to illustrate the difficulty
in
Canada has
Canada's energy situation will
implementing such a plan.
Canada
is
one of the few
l
79
Case Study: Canada's Energy Situation
Sec. 3.6
become
industrialized countries in the world that has the potential to
The fundamental reason
energy supplies for the long term.
large land mass and
relatively small population, has
sources, including crude
tential.
oil,
is
self-sufficient in
that the country, with
been well endowed with natural
and hydroelectric po-
natural gas, oil sands, coal, uranium,
Unfortunately, however, most of the resource-rich areas are separated by large
distances from the principal
consuming regions
in the nation.
Not only does
comes involved
in
resource
management and
taxation policy.
As
this
add
to
government be-
transportation costs, but because interprovincial trade occurs, the federal
vincial
its
re-
a result, federal-pro-
confrontations have arisen in the past over such issues as pricing, revenue
sharing, exploration incentives, and ownership of offshore resources,
of the consuming public.
Hence
all to
the detriment
not certain whether the country will ever achieve
is
it
long-term energy self-sufficiency.
Canada's National Energy Board has reported on the possible supply of and de-
mand
for
Canadian energy over the period 1980-2000 (NEB, 1981).
trate the nature
of the problems and the uncertainties that
may
The
results illus-
be encountered
in the
provision of future energy supplies.
The primary energy demand
lation
in
Canada
in
Assuming
1980 was 10.3 EJ.
growth averaging 1.0% per year and an annual increase of 3.2%
in real
a
popu-
gross na-
1980-2000, energy requirements could grow to
The demands would be met as shown in Figure 3-15.
A large fraction of the coal produced, as well as some oil and natural gas, is burned to
produce electricity, and the total role of electricity in the energy demand picture is
shown in Figure 3-16.
tional expenditure during the period
16.2 EJ
by 2000 (NEB, 1981).
Renewable Energy, 5.2%
Renewable Energy, 3.1%
Coal,
*LPGs, 0.9%
*LPGs, 0.3%
9.8%
1980
10,356 Petajoules
2000
16,176 Petajoules
Figure 3-15
'Gas plant
Primary energy demand, in Canada. Source:
liquid
petroleum gases
only.
NKB
l
(
)Sl
i.
1
80
Energy Growth
Renewable Energy, 5.2%
Renewable Energy, 3.1%
Coal,
*LPGs, 0.3%
Chapter 3
LPGs, 0.9%
Coa 2 .5%
,
2.8%
1980
10,356 Petajoules
2000
16,176 Petajoules
Figure 3-16
Source:
*Gas
NEB
Primary energy demand
in
Canada showing
total
role
of electricity.
(1981).
plant liquid petroleum
gases
only.
Two
important components on the supply side for the future are oil and natural
The locations of the major sources are shown in Figure 3-17. Comparing the
NEB's base-supply case for crude oil and equivalent products with its middle-demand
assumptions, we see that demand will exceed supply by 183,000 mVday in 2000, as
shown in Figure 3-18. Of course, the level of required imports could be reduced siggas.
nificantly if oil prices,
where
which collapsed sharply
profitable investment in
new
oil
in
1986, were to recover to the level
sands recovery plants could be made.
However,
as long as such recovery does not occur, the modified base supply curve in the figure
not likely to be achieved.
Hence
the base supply curve
seems the more
likely
one
is
at
present.
The domestic supply of
natural gas
is
more encouraging. As of year-end 1985.
(NEB, 1987). Hence at 1985 pro-
established reserves were estimated to total 77.4 EJ
duction rates of about 2.7 EJ/yr, this equates to nearly 30 years of supply.
If all
available production capability were to be utilized, frontier and offshore supplies
the Beaufort Sea, the Arctic Islands,
2000.
the
from
and the Atlantic coast would not be required before
Undoubtedly, new gas discoveries will be made which will extend the period of
Canada's heavy reliance on natural gas.
volumes of natural gas
to the
The prospects
for continuing to export large
United States beyond the year 2000, however, appear
doubtful.
Canada enjoyed a positive balance of trade in energy commodities, as inThe net dollar inflow to the country from energy trade was $1
billion (Canadian), approaching the $14.5 billion inflow from total merchandise trade.
The energy trade picture should remain healthy into the 1990s, when significant deIn 1985,
dicated in Table 3-13.
Sec. 3.6
81
Case Study: Canada's Energy Situation
WESTERN CANADA
SEDIMENTARY BASIN
Oil and gas resource regions of Canada.
Figure 3-17
Source:
Procter et
al.
(
1984).
400
CD
Q
300
CD
ny
o
Q.
200 -
</>
Q)
3
O
CO
<2
100 -
2000
1980
Figure 3-18
Source:
NEB
Supply of and demand
(1981).
lor
crude
oil
and equivalent products
in
Canada.
82
Energy Growth
creases in exports of
and natural gas are
oil
likely to occur.
have to import large quantities of offshore crude
At
Chapter 3
Canada may
that time
oil.
TABLE 3-13
CANADA'S ENERGY TRADE, 1985
(MILLIONS) OF CANADIAN DOLLARS)
Crude
Exports
Imports
5,930
3,701
Oil products
2.318
1.419
Natural gas
3.912
oil
899
—
3,912
122
869
887
1,109
34
136
-102
1.408
8
1,400
822
28
794
17,411
6.301
11,110
Electricity
Uranium
EMR(I986).
Source:
Many
229
991
Coal products
Total
2
1,996
Liquid petroleum gases
Coal
Balance
other industrialized countries in the world will also be seeking
from sources
that
may
not be able to supply the total required.
may be forced in
solved many years ago:
cians
answer a question
the near future to
that
is
how
oil
supplies
Hence Canadian
that
politi-
should have been
re-
from
oil
to ensure that the country's vast potential
sands, coal, uranium, and hydroelectric sources can be developed and utilized with the
objective of ultimately achieving energy self-sufficiency.
Other countries will face more
the United States, and the problems
critical
decisions on energy needs than
on a global basis
will be
even greater.
for cooperative world planning in energy use, population growth,
protection cannot be ignored indefinitely
if
Canada or
The need
and environmental
severe economic and social upheaval are to
be avoided.
PROBLEMS
renewable and nonrenewable sources of energy.
3.1.
List the
3.2.
List the available energy sources for the
world today and 40 years from now
in
order of de-
creasing importance according to your perception (see Figure 3-12).
3.3.
3.4.
If
you were designing a cylindrical tank
sumption of crude
oil,
of the tank
its
is
half
in
Problem
burnup of 7300
kg/m 3 .)
one day's supply of the world's conto specify?
Assume
that the height
diameter.
What volume of uranium
ergy as
to contain
what dimensions would you have
3.3
MWd
fuel
would be needed
to
supply the same amount of thermal en-
from natural-uranium-fueled power reactors operating with a
(
fuel
thermal )/tonne uranium? (Assume a uranium density of 9300
Chapter 3
3.5.
As
83
Problems
a group project, evolve a case study similar to the one given in this chapter for Canada.
using a country of your
3.6.
The Syncrude
own
sands plant
oil
choice.
northern Alberta
in
Assume
is
designed to produce 129.000 barrels per
power
Edmonton which operates with an efficiency of 35% and a capacity factor* of
What would be the gross electrical output of the power plant?
809!
How much has world energy consumption increased during the twentieth century, and why
daj nf synthetic crude
oil.
that all of this output is delivered to an oil-fired
plant in
.
3.7.
has
3.8.
it
Name
thus increased?
the three largest nation-producers of crude oil in the world in 1991, and tabulate their
Did any of the three export crude
outputs.
3.9.
An
office building has
how much?
oil? If so.
whom
500 workers, each of
spends 8 hours
There are 150 office machines, each generating 500
per week.
W
in the
building 5 days
for 5 hours per
working
Calculate the annual (52-week) amount of energy generated by the workers and the
day.
machines assuming
a
worker "energy" of 100 W.
cents/kWh for the heat provided, what would be
total
each worker were
If
be paid 3
to
annual payment and the payment per
worker'
3.10.
A
country of area 200.000
late the total
of
sity
person/km :
1
W/m
radiation of 150
3.11.
A
has an annual energy consumption of 10 15 Btu/yr.
Assume
.
:
the fuel
An
that
10%
is oil,
is
coal.
20 c/c
a
food consumption of 8 MJ/person
natural gas,
is
volumes used annually (except for
electricity generating plant
it
operates
at
is
to
5%
water
sity
3.13. (a)
is
in
65%
day and a solar
•
is
MJ
wood, and
of energy per year, of which
25%
is
Calculate
electricity.
electricity).
produce 200
MW
Assuming
of electricity from coal.
3592 thermal efficiency, calculate the coal utilization in tonnes per year
given that the coal has a heat content of 30 kJ/g.
converted
Calcu-
reaching the ground.
person living and working on a farm consumes 500,000
40%
3.12.
km 2
wattage of solar radiation, fuel, and food for the country for an average den-
of heat and rises
in
If the
cooling-water flow accepts the un-
temperature by 5 C. what must be the flow of cooling
cubic meters per second? The heat capacity of water
is
4.18 J/g
•
C, and
its
den-
dam,
elec-
1000 kg/m\
Select an energy development facility such as an oil refinery, hydroelectric
tricity
generating station, or coal mine
late the
energy flows occurring
in
an area with which you are familiar.
in the facility
Calcu-
from published performance data such as
refinery throughput or wattage.
(b)
Compile an environmental impact matrix
for the facility in part (a), listing
and identifying environmental technologies that have been installed
—
all
impacts
for example.
wastewater treatment.
3.14. Prepare an environmental impact matrix for a hydroelectric project under the following
headings: Site preparation: Reservoir:
3.15.
A 100-MW
Dam; Power Transmission.
coal-fired generating station has been built
dustrial area.
on Lake Erie
to serve a
growing
Storage of Coal; Burning of Coal; Generation of Steam; Distribution of Power.
what environmental controls should be
"Capacity factor
in-
Prepare an environmental impact matrix for this station under the headings
=
actual energy production
installed.
—
perfect production.
Identify
84
Energy Growth
Chapter 3
REFERENCES
Barney, G. O. The Global 2000 Report
Pergamon Press, 1980.
to the President
of the United
Washington, D.C.:
States.
Biswas, A. K. Energy and Environment. Ottawa: Environment Canada, 1973.
British Petroleum.
BP
Statistical
Review of World Energy. London:
British Petroleum
Company,
BP
Statistical
Review of World Energy. London:
British Petroleum
Company,
1986.
British Petroleum.
1992.
Carson, R.
New
Silent Spring.
York: Fawcett Crest, 1962.
Chigier, N. Energy, Combustion and Environment.
EMR,
EMR,
EMR,
New
York: McGraw-Hill, 1981.
Current Energy
Statistics.
Ottawa: Mines and Resources, Canada, 1986.
Current Energy
Statistics.
Ottawa: Energy, Mines and Resources, Canada, 1987.
Current Energy
Statistics.
Ottawa: Energy, Mines and Resources, Canada, 1993.
Fowler,
Frisch,
M. Energy and
J.
J.
the Environment.
Myth
R. "Energy Abundance:
New
York: MacGraw-Hill, 1975.
or Reality?" Paper presented
at the
1
3th Congress of the
World Energy Conference, Cannes, France, October 1986.
Frisch.
J.
R. "Energy 2000-2020:
World Prospects and Regional
Stresses." Paper presented at the
World Energy Conference, London, 1983.
Hafele, W. Energy
in
a Finite World: Global Systems Analysis, Vol. 2 Cambridge, Mass.: Ball-
inger, 1981.
Leopold, L.
Clarke,
B.,
F
E.,
Hanshaw,
B. B., and Balsey,
J.
R.
"A Procedure
for Evaluating
Environmental Impact." U.S. Geological Survey Circular 645. Washington, D.
Government Printing
Malins, D. C.
ganisms,
Munn,
(ed.). Effects
Vols.
1
and
C:
U.S.
Office, 1971.
of Petroleum on Arctic and Subarctic Marine Environments and Or2.
New
York:
Academic
Press, 1977.
R. E. Environmental Impact Assessment, Scope
5.
Toronto: Wiley, 1979.
NEB. Annual Report
1986. Ottawa: National Energy Board of Canada, 1987.
NEB. Annual Report
1990. Ottawa: National Energy Board of Canada,
NEB. Annual Report Supplement
March 1991.
1991. Ottawa: National Energy Board of Canada, August 1992.
NEB. Canadian Energy Supply and Demand, 1980-2000. Ottawa:
National Energy Board of Can-
ada, 1981.
Nelson-Smith, A. Oil Pollution and Marine Ecology.
Procter, R. M., Taylor, G.
C, and Wade,
J.
New
York: Plenum Press, 1973.
A. "Oil and Natural Gas Resources of Canada."
Geological Sun>ey Paper 83-31. Ottawa: Energy, Mines and Resources, Canada, 1984.
Putnam,
P.
C. Energy in the Future.
New
York: Van Nostrand, 1953.
Tuve, G. L. Energy, Environment, Populations and Food.
New
York: Wiley, 1976.
World Bank. World Development Report. London: Oxford University Press,
World Energy Conference. Survey of Energy Resources. Oxford: Holywell
Wyatt, A. The Nuclear Challenge.
Toronto:
Book
Press, 1978.
1981.
Press, 1986.
CHAPTER
4
Natural Environmental Hazards
Ian Burton
4.1
INTRODUCTION
Natural environmental hazards are those conditions or processes in the environment that
damage or loss of life in human populations. Natural hazards are
human environmental disturbances by the fact that they owe their or"God-given" environment rather than to human action. The most important
give rise to economic
distinguished from
igin to the
natural hazards include floods, droughts, earthquakes, tornadoes, and
human environmental
fire.
Examples of
disturbances include air pollution, water pollution, improper dis-
posal of toxic wastes, the hazards associated with the failure of the manufactured parts
of our environment
(e.g..
a building or bridge collapse), and the accidental release of ra-
diation from a nuclear generating station or chlorine gas from a ruptured tank car in a
train derailment.
This distinction between natural and
because
it
human environmental
suggests where attention should be directed
the hazards.
In
in
examining flood hazards, for example,
it
disturbances
is
useful
seeking to alleviate or control
is
clearly necessary to focus
on the natural processes of precipitation, runoff, and stream behavior to mitigate their
effects.
In
examining problems of pollution or technological hazards,
processes and the design of engineered systems that
natural processes that
esses
is
may
a necessary part
demand
be affected by pollution.
it
is
the industrial
attention, in addition to the
Understanding the natural proc-
of natural hazards management, but as
is
shown
later,
it
is
not
85
86
sufficient
by
because natural hazards are not
itself
1983).
Nor
tivities
of people.
The
First, the
astrophic
is examined
more detail.
This issue
in
in
in fact entirely
more depth
owes
topic of natural environmental hazards
"natural" (Hewitt,
disturbances entirely due to the acafter the
problem of natural
importance to two
its
facts.
damage and loss of life inflicted upon human society are often substantial catevents, making the problem of natural hazards a salient one for the people at
and for
est history
hazards.
human environmental
for that matter are
hazards has been described
risk
Chapter 4
Natural Environmental Hazards
their
governments.
of experience
is
Second,
found
in the
in the field
record of
of environmental control, the larg-
how people have coped
with natural
Studies of that experience are a potential source of understanding and
in finding effective
lems covered
ways
to deal with the
more
wisdom
recently identified environmental prob-
in other chapters.
AND MEASUREMENT
4.2 CLASSIFICATION
OF NATURAL HAZARDS
Natural hazards clearly include a wide range of different phenomena. They can be classified
according to their principal causal process (Table 4-1).
In this chapter
primarily on geophysical hazards rather than biological hazards;
hazards are treated in Chapter
relate to the processes of the
8.
some of
we
focus
the biological
Geophysical hazards can be separated into those
that
atmosphere (climatic and meteorological phenomena) and
those that relate to the geological and geomorphological processes of the earth's crust
and
TABLE
4-1
its
surface.
CLASSIFICATION OF NATURAL HAZARDS BY PRINCIPAL CAUSAL AGENT
Geophysical
biological
Climatic and
Geologic and
meteorological
geomorphic
Snow and
Avalanches
ice
Droughts
Earthquakes
Floods
Erosion (including
Faunal
Floral
Fungal diseases
(e.g.,
Dutch
athlete's foot.
soil
Fog
erosion and shore
Frost
and beach erosion)
elm disease, wheat
stem disease,
rust)
Infestations (e.g.,
Bacterial and viral dis-
eases
(e.g.. influenza,
malaria, smallpox,
rabies)
Infestations (e.g., of
Hail
Landslides
weeds, phreato-
rabbits, termites, lo-
Heat waves
Shifting sand
phytes, water hya-
custs)
Tropical cyclones
Tsunamis
Lightning and
Volcanic eruptions
fire
Tornadoes
Source:
cinth)
Hay
Venomous animal
bites
fever
Poisonous plants
Adapted from Burton and Kates (1964).
The investigation of natural hazards is allocated to various scientific disciplines.
Thus meteorologists and hydrometeorologists study weather, storm formation and be-
Sec. 4.2
87
and Measurement of Natural Hazards
Classification
and other factors
havior, the intensity of rainfall,
that give rise to floods.
Hydrologists
The
concern themselves with flood magnitude and frequency and flood forecasting.
of geology and geophysics are subdivided into specializations such as seismology
fields
(dealing with earthquakes) vulcanology (having to
ogy
and landslides).
(treating erosion
mechanisms and processes and
This gives
related hazards.
plified in the attempts to
sorts of
are less concerned with
rise to
some fundamental
how
are natural hazards
these approaches
to the
exem-
Different
different purposes.
impacts and
tries to
clearly seen in the
is
and manage the
measured? There are two main approaches.
directed to the geophysical process and tries to measure
The second looks
to control
differences in approach, as
develop scales of measurement for natural hazards.
measurements are needed for
How
do with volcanoes), and geomorphol-
Usually, these specialists study the basic physical
two
its
size
The
measure those.
The
first
is
by volume or energy.
difference between
scales that have been devised for the meas-
The Richter scale measures earthquakes in
is measured by a seismograph, a
very delicate instrument calibrated so that the amount of the displacement of the pen reflects the amount of energy released as transmitted by the seismic waves. The range of
urement of earthquakes (see Figure 4-1).
terms of the energy released, in ergs/
earthquake magnitude
is
This energy
extremely large, from the barest tremor that can be detected
human beings, to massive moveTo accommodate this large range, the Richter scale is
logarithmically constructed, which often causes confusion in its interpretation.
News
reports of earthquakes commonly make use of the Richter scale. Clearly, however, this
only by an instrument and
ments
that
shake
down
scale conveys very
assume
quake. Thus an
likely to
is
little
information except to experts, since, for example, the public
that a Richter
but
itself,
6 earthquake
in
its
scale,
may be
on the other hand,
impact on people.
An
earthquake
created.
tries to
is
level
measure not the earth-
designated number
strong enough to be perceived by most people and causes
At
is
only twice as severe as a Richter 3 earth-
entirely misleading impression
The Modified Mercalli
quake
not directly perceived by
buildings.
damage
to glass
V
and
if
it
is
plaster.
X, an earthquake causes damage to many structures and the destruction of
some.
The fundamental
difference between the
two approaches stems from
objectives of the geophysical scientist (Richter scale) and the hazard
the different
manager (Modified
Whenever and wherever it may occur, a Richter 6.5 earthquake always
same energy release. The measurement is standard and universal and exists
Mercalli scale).
involves the
independently of the presence of
human
settlement in the earthquake zone.
from two earthquakes may bear no relationship
very strong earthquake (Richter 7)
than a
much weaker earthquake
in
may cause
'An
erg, a unit of
dyne acting
lor
I
in the
second on
a
work or energy
in the
is its
1
gram, gives
it
in
scale.
A
a sparsely populated area
human
settlement.
The
ad-
universal applicability on a constant basis
centimeter-gram-second system,
direction oi the force through a distance oi
mass of
damage
an area of concentrated
vantage of the Richter scale, therefore,
1
less
The impact
on the Richter
to their level
an acceleration oi
I
I
centimeter.
is
the
One dyne
work done by
is
a force oi
the force which, acting
centimeter per second per second.
88
Chapter 4
Natural Environmental Hazards
Impact Scale (Modified Mercalli)
Modified
Mercalli
IV
I
VI
VII
IX
VIII
XI
XII
Number
Persons
Perceived
I
Damage
Some
Few
None
by;
Many
Most
All
Glass
Furniture
Plaster
Chimneys
Structures
to:
O rdinary
Poor
Resistant
Destruction
Many
Most
All
Some
Many
Most
to:
Energy Scale (Richter)
Richter
Number
Energy
Release
in
In
1.2
4.47
4
3
X10 12
X10 14
7.94
2.51
6
5
X 10 16
7.94
X10 17
2.51
7
X 10 19
7.94
8
X10 20
2.51
X 10 22
Ergs:
Multiples
of
1-31.6
31,600
1,000
31,600,000
1,000,000
1,000,000,000
31,600,000,000
Base
Figure 4-1
Comparison of the Richter and Modified Mercalli scales for earthquake magnitude.
The Environment as Hazard, by Ian Burton, Robert W. Kates, and Gilbert F. White.
Source:
Copyright
anywhere
©
by Oxford University Press,
in the
world.
Its
big disadvantage
actual
amount of damage incurred.
The impact of an earthquake
flects
both the character of
human
as
is
that
it
conveys no information about the
measured by the Modified Mercalli number
soils are likely to suffer
As measured
much more damage
than those of proper construction and foun-
earthquake records a higher or lower level on
in these terms, the
the Modified Mercalli scale according to the quality of construction.
Mercalli scale therefore gives a measure of the impact
versality of the Richter scale.
whereby one can
cist's scale; the
ured
in
is
at the
The Modified
expense of losing the uni-
Both scales serve useful purposes, but there
reliably be converted to the other.
Modified Mercalli scale
is
some equivalent of
The Richter
scale
is
is
no means
a geophysi-
a hazard manager's scale.
Similar problems of measurement exist for
cases there
re-
settlement in the earthquake zone and the strength of
Poorly constructed buildings or those located on unstable slopes or
the earthquake.
dation.
Reprinted by permission.
Inc.
all
the Richter scale.
other natural hazards.
Thus
In almost all
tropical cyclones can be
meas-
terms of their central pressure, the pressure gradient from the center to the pe-
riphery of the storm, the
weather system.
given point on the
drograph.
wind
velocity,
and the speed of movement of the whole
Floods are usually measured
river,
and the
rise
and
fall
in
terms of the discharge of water
at
a
of water levels as reflected in a flood hy-
Blizzards can be measured according to the depth of
snow accumulation and
What
Sec. 4.3
the associated
89
a Natural Hazard?
is
wind speeds.
for other hazards,
There are few equivalents of the Modified Mercalli scale
and reliance
damages. This partly
is
reflects the
often placed on monetary (dollar) estimates of the
emphasis of
More important
esses themselves.
some
natural hazards.
major
city.
geophysical proc-
scientific interest in the
the difficulty in producing scales of impact for
is
Consider, for example, the impact of a heavy snowstorm on a
The same snowstorm
measured
as
in
depth of snow accumulation and wind
speed will have a different level of impact according to a series of factors
This variability of impact applies to other natural hazards.
4-2.
ume
may
of discharge in a river
and the moisture
deficit as
bear
or no relation to the
little
listed in
Table
For example, the vol-
amount of flood damage;
measured by the Thornthwaite water balance method (Thorn-
thwaite and Mather, 1955) or the Palmer drought index (Palmer, 1965) does not measure
the
actual
damage
suffered by
Both these measures of moisture
agriculture.
deficiency are climatic scales that do not take into consideration the drought resistance
of various crops or the cultivation methods used.
TABLE 4-2 FACTORS AFFECTING THE IMPACT OF SNOWSTORMS
IN URBAN AREAS
Frequency of major snow
The more
storm events
Slope of
streets
less
terrain, especially
more prepared
frequent, the
Snow accumulations on
and highways
the city will be
and the
impact there will be per unit of snowfall.
sloping streets have a
ruptive impact on traffic than
much
greater dis-
do similar amounts of snow on
level ground.
Time of occurrence
Snowstorms occurring
less
impact on
at
traffic
night or in the middle of the day have
than do snowstorms
Snowstorms occurring during
on
Associated temperature level
traffic
the
at
rush hour.
weekend have
At temperatures close to freezing, applications of
ways
less
impact
than do those occurring on weekdays.
them quickly;
clears
at
salt to
high-
lower temperatures, the snow
has to be ploughed and physically removed.
Availability of public transpor-
A
city with a
well-developed public
transit
system, including a
subway (underground) railway system, has an
means of transportation not available in cities
tation
alternative
that are
more
heavily dependent on private cars.
Good
ing.
The
measures
4.3
WHAT
IS
In the
scales of
measurement
is
that the unit of
is
A NATURAL HAZARD?
opening paragraph of
hazards.
Viewed
just as
takes
it
for the impact of natural hazards are generally lack-
economic loss or damage. The difficulty with such
measurement itself keeps changing (see Section 4.5).
best available yardstick
in
two
this chapter,
we gave
a
commonsense
the light of our discussion about measurement,
to
make
a quarrel, so
it
takes
two
to
make
definition of natural
it
is
now
clear that
a hazard: nature and hu-
90
Natural Environmental Hazards
man
In trying to understand the
beings.
human component
of natural hazards, the con-
should be considered.
tribution of anthropological research
Chapter 4
Looking closely
the
at
relationship of different cultural groups and their environments can enlighten our under-
how humans have responded successfully to environmental hazards (Sutlive
Where humans and their works are absent, however, there can be no nat-
standing of
1986).
et al.,
ural hazards.
mean
This does not
any
that
on an uninhabited continent
had arrived from across the Bering
settlers
when such
curred, but simply that
in its
ards, but in another, stricter, sense a flood
is
in
terms of
its
A
occur).
commonsense meaning
it
is
at
(i.e.,
any point on a river
be expected to occur on average once
is
their probability.
usual to describe the flood of a given magnitude
return period or recurrence interval
100-year flood
a natural haz-
is
it
understand extreme geophysical
important characteristic of extreme geophysical events
case of floods, for example,
In the
North America before
merely an extreme geophysical event.
we must
Thus, to understand natural hazards,
One
(e.g.,
no floods or earthquakes oc-
events occurred they were not hazards to people.
The word flood now has two meanings:
events.
Strait)
in
is
how
often
it
may
that discharge of
be expected to
water which
100 years. As shown diagrammatically
may
in Fig-
may be defined in terms of a specific flood frequency. A line can
map showing the areas expected to be flooded by the 100-year flood.
floods may still occur, but with a lower frequency. Similarly, within
ure 4-2, a floodplain
be drawn on the
Beyond
that line
more frequently, until one reaches the river channel itself. In most
humid and temperate environments, rivers reach the top of their banks almost once an-
the line floods occur
nually.
This introduces another element into the definition of a natural hazard.
event becomes so frequent that
channel of a river
event
is
it
is
is
all
normal condition
part of the
no longer a hazard.
expected to occur very rarely on a
hazard for
So
—
it
—
as
is
Similarly, at the other extreme,
human time
scale,
it
When
water
an
in the
when an
ceases to be a natural
practical purposes.
to restate
our definition:
A natural hazard is an extreme event in
mans and occurring infrequently enough
nature, potentially harmful to hu-
be considered not part of the
normal condition or state of the environment, but often enough to be of concern on a human time scale.
The
distinction
to
between hazards and normal conditions
standing of hazard
management
Canadian Arctic
certainly a difficult place to live.
is
These are examples of harsh environments.
Canada and
that
is
It
is
important for an under-
But
So
to cultural
well adjusted to
its
environment.
The
are the world's hot deserts.
groups such as the Inuit
nomads of the Sahel in Africa, their harshness does not
only when unusual events occur that a hazard exists for a
the pastoral
tute a hazard.
is
or adjustment as described later in Section 4.6.
in
consti-
society
What
Sec. 4.3
Flood Fringe
a Natural
is
91
Hazard 9
3
3
Flood Fringe
Floodway 2
No Development
Conditional
Conditional
Development
Regulatory Flood Level
100
-
Development
V
Year Flood Level (minimum)
_
"v"
Channel
v
Figure 4-2
Sonne:
Hydrological
of
definition
Ontario Ministry
nt
and
floodplain
;i
its
use
land-use
in
regulation.
Natural Resources
Notes
1.
The
floodplain
For example,
river
2.
The floodway
The
to
(e.g..
the 100-year flood or by a large flood of record).
Ontario the floods caused by the passage of Hurricane Hazel
In
1954 are used
in
some
basins
served
3.
defined by a flood frequency
Is
in
for
is
the lowest part of the floodplain, where no development
permitted and which
is
is
re-
the passage of flood flows.
flood fringe
is
an area
of floodplain land
where
filling
and development may be permitted subject
land-use and building code regulations designed to minimize damage.
Considering,
therefore,
environmental
that
hazards are
interactive
phenomena
rather than independent events, Mitchell (1990) considers the degree of hazard to be a
function of risk, exposure, vulnerability, and response.
Hazard
Risk
is
considered
to
=
/(risk
x exposure x vulnerability x response)
Exposure
Vulnerability can be measured
be the frequency of events causing losses.
nitude of population and structures
at risk.
is
in
the
mag-
terms of
preparedness, where a high degree of preparatory actions, often based on previous experiences, results in a
low
vulnerability.
tioned above, preparatory actions
hazardous events normal.
fected and external
The
phenomena"
As
may
Response includes
government agencies
made
might cause.
point being
lute,
(Mitchell, 1990).
here
to
is
in
that
drastic environmental change.
fore involves an appreciation of
how changes
compare with changes by human
action.
life."
the actions taken by those directly af-
mitigate losses the environmental hazard
"hazards are reactive, rather than abso-
Not only can the environment change due
also result
menmaking otherwise
often the case for the cultural groups
is
be part of "everyday
to natural events,
human
actions can
A
consideration of natural hazards there-
in
the environment through natural events
92
4.4
Chapter 4
Natural Environmental Hazards
EXTREME EVENTS AND ENVIRONMENTAL CHANGE
When
extreme events occur
in nature, they
property damage, deaths, and injuries.
have a direct impact on humans by causing
They
also have an indirect impact by changing
the character of the environment.
There has been a long-standing controversy among students of the history of the
earth about the relative importance of extreme events versus gradual change.
who emphasize
Those
the importance of extreme events (sometimes called catastrophists) can
point to the role of floods in erosion and deposition, the role of earthquakes in mountain
building, and the role of sudden glaciation in shaping the landscape of mountains and
On
lakes.
the other hand, the uniformitarians
emphasize the slow evolution of the earth
under the long continuation of processes that can be observed every day.
Until very recently the forces of nature, including both extreme events and gradual
processes, have far outweighed the effect of
on a local
scale.
phenomenon
(see
human impacts on
the environment, except
The modification of climate by volcanic eruptions is a well-known
Chapter 7). The dust particles in the atmosphere increase the albedo,
resulting in colder temperatures over large regions at the surface of the earth for periods
as long as
of
two years following
Mount Tomboro
in
the eruption.
Indonesia
in
For example, the great volcanic eruption
1815 led to two successive years of cold, wet grow-
ing seasons throughout the world beginning in 1816
—
"the years without a summer."
The effects were aggravated in Britain, France, Germany, and the Netherlands by the
economic consequences of the Napoleonic wars, and much suffering resulted (Post,
1977).
eroon
Volcanic eruptions can also release poisonous gases, as happened
August 1986, when 1700 people were
in
killed
in the
Cam-
and 10,000 were otherwise
af-
fected by the toxic emissions.
By
in
contrast, air pollution
urban areas.
don, England, great
Burton, 1973).
caused by human action has been heavily concentrated
Approximately 4000 "excess deaths" have been attributed
smog episode of December
to the
Lon-
5-9, 1952 (Larsen, 1970; Auliciems and
Valid comparisons of these diverse kinds of events in terms of
human
consequences are not easily achieved.
The changes
that
have occurred
by the extraction of
in the hydrological cycle
groundwater, the deforestation and urbanization of watersheds, cloud seeding, and reservoir construction
They
all
seem very small by comparison with
can, of course, have major impact on a small scale but
bal basis
when compared with
the scale of natural events.
seem
insignificant
on a glo-
the vast forces of nature.
This conventional view that the greatest environmental impacts are from natural
hazards has been questioned in the past few years.
It is
now
generally accepted that the
burning of fossil fuels has substantially increased the carbon dioxide content of the
mosphere and
warming
sibility
—by
that this
may
lead to significant climatic change
the middle of the next century (see Chapter 5).
—
Recognition of the pos-
of humans changing the environment on a global scale, either deliberately or
advertently,
at-
specifically, a global
in-
has led to a major redirection of scientific effort toward the study of
biogeochemical cycles (White and Tolba, 1979).
Most extreme geophysical events do not cause
a permanent change to the environ-
93
Impacts and Trends
Sec. 4.5
The) ma) he regarded as
ment.
a fluctuation or
temporary disequilibrium from which
environmental systems will return to a more "normal" or equilibrium
these temporary environmental changes have severe impacts on
because the) are extreme and short
conditions to which
tivities
humans have
lived.
adjusted.
and for what
4.5
Where
societies are
difficult to
measure im-
take place slowly and thus give opportunity for adjustment.
many
pacts of natural hazards
we can
more
is
it
The study of
variables are changing simultaneously.
therefore doubly important:
is
learn that
is
course,
society, largely
They represent a departure from the normal
By contrast, most changes from human ac-
adjusting to deteriorating environmental conditions,
pacts because too
Of
state.
human
has value both in
it
human environmental
applicable to
its
the im-
own
right
disturbances.
IMPACTS AND TRENDS
Everyone
Major disasters are one end of
disaster occurs.
bances of fluctuations
in
losses recorded
full
from major
a
is
from
since
when
a
in
aggregate,
amount
to
The losses
more than the
disasters.
spectrum of impacts
is
suggested
in
Figure 4-3. which shows approxi-
famous 1906 earthquake
a recurrence of the
meant the same-size earthquake
1906.
tend to
dramatically reported
spectrum that extends to minor distur-
mate estimates of impacts of various kinds (from death
sult
is
environment that cause small losses.
the natural
caused by many minor events, however, can,
The
We
affected by natural hazards, not only the obvious "victims."
is
think of the term victims because the impact of hazards
(8.3 as
to taxes) that are
in
San Francisco.
measured on the Richter
expected to
By
re-
recurrence
scale) as occurred in
The impacts now would be very different since the city has changed so much
1906. In that event, 450 people were killed and 514 city blocks containing 28,000
buildings were almost totally destroyed by the earthquake or the subsequent
fire
which
continued for 4 days.
Scientific simulation (Algermissen et
al.,
1974) permit
that an
some estimates of
al.,
1972) and social scenarios (Cochrane et
the impacts of a recurrence.
Bay area
in
the range
2000
to
10.000. and there could be as
pending on the time of day the earthquake occurred.
be dislocated
— uninjured but homeless.
The
the aftermath of an earthquake, as well as
since
1906.
iVlany
more people would
be caused by damage
earnings.
those
who
fires
changes
and the
in
in
in
in the
as 40.000 injured, de-
would
ability to control these
building codes and practices
In
some cases
the thousands of dollars.
the area of physical impact,
as a result of the disruption.
to an
estimated
this
would
to buildings and oilier property or by indirect loss such as loss of
damage
would be disturbed.
As in all major
is
deaths
additional 20,000 people might
suffer financial loss.
Per capita losses might well be
suffer
An
many
it
in
scale of loss of residential buildings
be greatly affected by the subsequent occurrence of
in
Thus
earthquake of the magnitude of that of 1906 would today result
disasters,
many
The normal functioning of
the
In addition to
others would suffer loss
economy
in a
wide area
many more people would make voluntary contributions
These donors are people who voluntarily agree to
earthquake disaster relief fund.
94
Chapter 4
Natural Environmental Hazards
Environment as Hazard
10 6
-\
'in
Dead
13
if)
5
% 10
2
Injured
CD
6
10 4
Dislocated\^
and
DamagedNw
($
o
isses
CJ
Distrurbed^v
_l
E
10 2
CO
Donors^v
o
O
Taxed ^v
o
Capita
Figure 4-3
Loss sharing: future San
The
Francisco earthquake. Source:
Q-
I
I
10 4
10 3
I
I
10 6
10 5
I
Environment as Hazard, by Ian Burton,
10 8
10 7
Robert W. Kates, and Gilbert
Population Affected
(Number
of
making
share the loss by
Persons)
Inc.
©
F.
White.
by Oxford University Press,
Reprinted by permission.
a financial sacrifice through the
Beyond
charitable organizations.
Copyright
Red Cross
or various private
government of the United States would un-
that, the
doubtedly provide disaster assistance extending perhaps to several billion dollars, de-
pending on the scale of the
disaster.
The
entire population of the United States as
taxpayers would thus contribute to the costs of relief and rehabilitation, and the eco-
nomic
into Canada and beyond.
number of deaths can be larger than
would no doubt extend
ripple effect
In
major natural
disasters, the
environmental disturbance except war.
Hwang Ho
the great
It is
(Yellow River) floods
in
any human
believed that 3.7 million people perished in
in
China
in
August 1931. Some 830,000 are
thought to have died in the earthquake that struck Shensi Province, China, on January
23, 1956.
Such estimates
brought a storm surge 7
delta in
1
million people.
The
tropical cyclone that
tide to the outer islands of the
Ganges
November 1970 was initially reported to
More realistic estimates later put the death toll
in
around 225,000, but accurate figures are not available.
High
loss of life as a result of floods, earthquakes,
most exclusively
is
above normal high
Bangladesh (then East Pakistan)
have killed more than
at
are notoriously unreliable, however.
m
in
developing countries.
usually very low by comparison, but property
cal storm,
Agnes,
Pennsylvania, and
that
New
and droughts now occurs
al-
In developed, industrial societies, loss of life
damages can be very
high.
The
tropi-
brought floods to the eastern United States (especially Virginia,
York)
in
June 1972 was a very similar meteorological phenom-
Sec. 4.5
enon
lion,
to the
but
95
Impacts and Trends
Bangladesh cyclone of 1970. The damage caused was estimated
The damages were
118 people died.
onl)
at
$3.5
much
because
so high
bil-
urban
development had taken place on the narrow floodplains on which many eastern towns
were located. Loss of live was comparatively low because effective warning and evac-
remove 250.000 people from
uation plans were used to
their
There was no effective warning and evacuation scheme
225.000 people
The
who
pattern
high loss of
life
is
died
a familiar one.
In the floods
of
In
due
to
The Great Flood of
Hurricane Hazel
at
the Mississippi River
more than $10.2
attributed to the flood
measured
(EOM,
a relatively low 6.6
most costly natural disaster
in
in
Toronto
$3.5 million in the
widespread natural disasters to occur
acres and caused
moved
the
poorer countries, natural disasters tend to cause
and
in the
billion in
1993).
its
Valley alone (Burton,
United States.
It
1965).
1993 was one the most
tributaries in
submerged 13.5 million
However, very few deaths were
damages.
that struck
Los Angeles
scale, but estimates of the
history ranged
U.S.
in
Don
The earthquake
on the Richter
In more developed indusdamages can be very high.
1954, the death toll was 81 and
losses.
generally low but economic
life is
damages were estimated
the
out of danger.
could have
Bangladesh.
in
and comparatively lower economic
trial societies, loss
homes and
that
from $30
to
$40
in
1994
damage from
the
billion with the loss
of 55 lives (Maclean's 1994).
In highly organized industrial societies, the costs of disruptions
caused by natural
hazards and other perturbations of the system can be higher than the direct damages.
Few
detailed estimates have been made, but a study of the impact of the Mississauga,
November 1-17. 1979 showed that while
damages were very small, the cost of the disruption to the 225,000 people
evacuated was $68.7 million, by a conservative estimate (Burton, et al.. 1981).
The health impacts of natural hazards of the geophysical type are now generally
Ontario, train derailment and evacuation of
1
physical
small
in the
developed countries, but continue
and disaster assistance teams
in
to
be a major concern of relief workers
developing countries because epidemics
cholera will probably break out. due to the poor sanitary conditions
oi'
typhoid and
common among
the
survivors.
The
social
and psychological impacts of the major hazard events are much more
difficult to assess.
In the
management of emergencies, concern
the threat of natural hazards
will result in panic, social disorders such as looting
and psychological
distress.
is
often expressed that
and the associated social disruption, when an event occurs,
While
all
and increased crimes of violence,
these do occur on occasion, the evidence from re-
cent studies strongly suggests that well-established and normally healthy societies are
slow
to panic,
do not
resort to looting or violent crime,
and are
resistant to psychologi-
commonly responds with a burst of constructive
ergy and community spirit. Volunteers man the dikes, till sandbags, help search lor
missing, take care of the injured, and provide shelter for the homeless.
In many
cal
harm.
In fact, a healthy society
The derailment
carrying
90 tons
ol chlorine gas.
resulted in fires
ol chlorine
developed
and explosions
a large hole.
ol tank cars carrj ing
enthe
in-
propane ami toluene, and a tank car
The evacuation was necessitated
bj fear
<>i
a
sudden escape
96
Natural Environmental Hazards
stances the official governmental
ble help
In
emergency services could not cope without considera-
from volunteer organizations, which
where there
societies
Chapter 4
often forthcoming in abundance.
is
problems concerning
are already serious
interracial or
class hostility, lack of trust in responsible government, and latent social or political unrest, the
social
occurrence of a hazard event
American
may
And
cities.
The unpopularity of
Islamabad (West Pakistan) was attributed partly
Similarly, the overthrow of the
of the cyclone.
1973 was attributed
in
again, the separation of East Pakistan (Bangladesh) from Pakistan
occurred soon after the cyclone of 1970.
in
be seized as an opportunity to manifest these
For example, looting has been associated with natural hazard events
ills.
in part to the failure
drought that affected his country
to
its
the national
government
lack of concern for the victims
Emperor Haile
Selassie in Ethiopia in
of his government to respond effectively to the
in the early
1970s.
Natural hazards probably facilitate, rather than cause, such political and social
They
events.
do, nevertheless, appear to have a great deal to
do with the timing of
so-
disturbances by providing a pretext for the expression of discontents
cial or political
that already exist.
The impacts of major hazard events are well known and well documented (Nash,
While there are difficulties in the precise measurement of impacts, at least some measurements are made. However, with a few exceptions, there is
no systematic record of hazard losses that permits firm conclusions to be drawn about
1976; Gibney, 1978).
trends.
There are good reasons why
ment apparatus
data.
In
many
is
all
In
enough
many developing
countries, the govern-
to devote time to the gathering of such
of the smaller, developed, industrialized countries, the occurrence of ex-
treme natural events
Where
territory.
this is so.
not large or strong
is
relatively infrequent,
statistics are collected, they
because of the limited extent of the national
tend to be for a specific hazard and not for
hazards.
The
best data readily available
come from
the United States.
As one example,
infor-
mation on the frequency of tornadoes together with information on deaths and property
losses
is
available from the U.S.
National Oceanographic and Atmospheric Administra-
The number of tornadoes reported in recent decades is substantially higher than in
the early decades of this century (over 6800 in the 1960s compared to about 1300 in the
1920s), presumably because of more complete reporting rather than an actual increase in
frequency of tornadoes. Care must be taken when looking for trends in statistics on deaths
and property losses, as the change in the number of tornadoes reported, casts doubt on the
tion.
comparability of later figures with those of earlier years.
Death from four natural hazards
— lightning
(7124),
tornadoes
(4892),
floods
(1879)— in the United States from 1940-1975, as documented
by Mogil and Groper (1977). show slight trends over a 36-year time frame. The longterm trend appears to be down for deaths from hurricanes and lightning and up, or a
best unclear, for tornadoes and floods. The trends are hidden within a high range of
(3277), and hurricanes
variation on a year-to-year basis.
The most comprehensive survey of
concluded
that
natural hazards in the United States to date
aggregate (not per capita) damages from natural hazards are increasing
Sec. 4.5
in
most cases (Table 4-3).
deaths
is
97
Impacts and Trends
some
In
instances there
declining or staying about the same.
about the trends
ties the losses
in
damages,
it
appears likely that
from natural hazards continue
TABLE
TRENDS
4-3
is
Although
in
evidence that the number of
it
is
not possible to be precise
many developed,
industrial socie-
to rise.
DEATHS
IN
AND DAMAGES FROM SELECTED NATURAL
HAZARDS IN THE UNITED STATES, 1954-1978
Hazard
Damages
Deaths
+
+
+
NA
NA
+
+
NA
NA
-
Avalanche
Coastal erosion
Drought
?
Flood
+
+
Frost
+
Hail
+
+
+
Earthquake
Hurricane
Landslide
?
Tornado
+
Tsunami
NA
?
+
+
Urban snow
NA
Volcano
Source:
White and Haas (1975).
There have been few attempts
scale.
A
summary
statistical
indicated a total worldwide loss of
deaths per year.
+
+
Windstorm
wide
+
Lightning
The number of
to estimate losses
from natural disasters on a world-
for the 35-year period
life
1947-1981 (Thompson, 1982)
of 1,208,000 people, giving an average of 34,514
natural disasters per year as recorded in the
New
York
Times Index shows a generally downward trend from 1955 to 1975 and strong upward
trend since 1975 (Mogil and Groper, 1977).
natural hazards or disasters in
Flood losses
damages (White
in the
et al.,
United States have often been quoted as an example of rising
1958).
Even
doubt on such conclusions. There
to
mask long-term
There are no world estimates for loss from
monetary terms.
trends.
is
here, however, the unreliability of the data casts
a great deal of year-to year variability,
Major expenditures on flood control began
States with passage of the Flood Control Act of 1936.
that date,
trend.
when reduced
to constant-dollars terms,
The record of
in
which tends
the United
flood losses since
does not provide clear evidence of a
98
4.6
Chapter 4
Natural Environmental Hazards
ADJUSTMENTS AND THEIR CLASSIFICATION
In a simplified but generally valid way,
we can view
the history of our attempts to
cope
with natural hazards as being divided into three periods: preindustrial, industrial, and
postindustrial.
4.6.1 Preindustrial Approach
In traditional preindustrial societies, the
means were not generally
or to attempt serious modifications of the natural environment.
nuity to defend themselves
from the
perils of the
available to control
People used their inge-
environment, using the technology
they possessed and their experienced judgment as to what nature might do.
and paper houses
were unlikely
in
Japan were either resistant to earthquakes,
to crush those trapped inside.
or, if
Small wood
they did collapse,
Alpine villagers designed houses with
steep-pitched roofs to withstand heavy snowfall and located them in places where they
knew, from experience,
ical
that
avalanches were unlikely to occur.
Peasant farmers
in trop-
savannah climates practiced intercropping of a variety of plants as a protection
against drought.
Peasant farmers in India timed the planting and harvesting of rice and
other crops to harmonize with the arrival of the
monsoon
rains.
Everywhere, the rhythms and technologies of traditional societies were attempting
environment while trying
to use the resources of the natural
ards.
For
much
of the time
this
worked
successfully, and
to avoid the
it
impacts of haz-
failed only
when extreme
events of high magnitude occurred (Figure 4-4).
In a
few instances, preindustrial societies did organize
the control of water.
The construction of polders
control dikes along the
gris
Hwang Ho
River
in
in the
to build
major works for
Netherlands, the massive flood-
China, and the irrigation systems
and Euphrates valleys are well-known examples.
in the Ti-
These systems were part of the
development of advanced civilizations and certainly permitted a greater density of population to be supported
on the
land.
Yet
when major
droughts
tidal surges, floods, or
occurred, disaster resulted on a scale that previously would not have occurred.
4.6.2 Industrial Approach
Early major water-control schemes in the industrial period were precursors of the application of
modern technology
teenth century to
built
to the control of the
From
environment.
the early nine-
the present day, technological control systems have been designed and
on an increasing scale and
at
an accelerating
rate.
Many
of these systems are de-
signed to provide protection from natural hazards or from extreme fluctuations
ral
systems.
In the last
few decades, many large dams have been
built to store
in natu-
water for
the purpose of flood control and to provide a reliable supply of water for irrigation in
areas of low and uncertain rainfall.
Other examples of the application of science and technology
to control nature in-
clude cloud seeding to produce rain in drought areas and modifications of the force and
track of hurricanes.
Various technologies have been developed for hail suppression, fog
Sec. 4.6
99
Adjustments and Their Classification
40
5
-
9
-
year Moving Average
year Moving Average
35
30
-
Q.
</)
All
to
oS
£3
E
Disasters
25
10
Large
1950
1955
1960
-
Area Disasters
1970
1965
1975
1980
Year
Figure 4^1
dispersal,
Global disasters, 1947-1981. Source:
and avalanche control.
coastal flooding and erosion.
of chemical pesticides are
ural hazards, there
is
achieve such control.
In the
made
Thompson
(
1982).
Seawalls and groynes are built to protect against
category of biological hazards, massive applications
to control pests.
evidence of attempts
at
Practically wherever one looks at nat-
control or of research and development to
In fact, the discovery that the
deep disposal of liquid wastes
Colorado triggered a series of very small earthquakes has even led to the suggestion
in
that
these strains in the earth's crust could be gradually alleviated in a controlled process.
Many
human
of these technological achievements have brought great benefit to
society. Clearly,
by the criterion of benefit-cost analysis, the benefits
ronmental control have generally exceeded the costs.
to society
In flood control, for
example, the
costs of building, maintaining, and operating dams, dikes, and channels are
exceeded, sometimes by
far,
project feasibility studies for
by the value of the flood damages
dams have
of envi-
commonly
that they prevent.
Most
the built-in requirement that the flood-control
and other benefits must exceed the costs.
Why,
then,
is
there evidence of rising losses from natural hazards in general?
possible explanations that are sometimes given can quickly be dismissed.
crease
is
not due to the declining value of the dollar through inflation: estimates of
age from natural hazards are
made
in constant-dollar
Two
First, the in-
dam-
terms by discounting present-day
100
Chapter 4
Natural Environmental Hazards
dollars back to a
common
way, to changes
in a small
base value.
in the
when
the record
is
is
not due, except perhaps
more frequently now than before
or other extreme events occur
false
Second, the increase
environment: the perception that floods, earthquakes,
examined.
Similarly, while
it
turns out to be largely
true that climate changes, the
is
trends are too long-term to be reflected in the relatively short period during which
age data have been collected.
dam-
Also, short-term fluctuations have an impact but average
out over decades.
The
found
better explanations for rising losses
in the limitations
cally,
it
from some natural hazards are
of technology and in changes in
human
not practical to design and construct hazard-control systems to
is
the very low-frequency, high-magnitude events.
In flood control, for
sign storm usually has a recurrence interval of 100 years.
dam
ducing the flow of water that a
That
is,
to
be
Technologi-
society.
accommodate
example, the de-
the conditions pro-
designed to control are expected to occur on the
is
average once every 100 years. The larger the dam. the higher the marginal cost of each
additional increment of storage capacity.
go up with
scale, so
As
the marginal costs of construction tend to
do the benefits decline. Whatever the economic losses
likely to be
caused by a 100-year flood may be, the average annual benefits of prevention, when
duced
to present value,
control,
means
may amount
to very
more frequent
usually pays to control the
it
that
when
the design capacity of the system
ards) will continue to occur.
The second explanation
changes
in
human
growth
for the
in
re-
economics of environmental
This
rather than the rarer events.
is
exceeded, floods (or other haz-
Thus, although a spillway
dam when its storage capacity
dam may not be safe from flooding.
flow safely past a
below the
In the
little.
is full,
is
provided to carry the excess
the residents of the floodplain
damages from natural hazards is that
As populations grow and econ-
society are the cause (Hewitt, 1983).
omies develop, and as people concentrate
pioperty and wealth to be damaged.
ards might be expected to
in cities, there is a greater
accumulation of
Other things being equal, losses from natural haz-
grow along with population and gross national product.
sofar as environmental control systems are effective, they
may be
In-
expected to reduce
losses or, at any rate, to keep the increase in losses to less than the increase in population
and GNP. The indications, however, are
that in
some
instances at least, the reverse
is true.
If
expanding population and physical property were randomly distributed over the
face of the earth, or over a national territory, one might expect losses to rise in step with
development.
If
environmental control systems were always effective, and
sought to avoid areas
known
to be hazardous, losses should decline.
if
people
However, losses
have increased because people have not avoided hazard zones, but seem almost deliberately to have
chosen
to put
themselves
in the
path of danger.
In the case of floods this
may
be because of a false sense of security generated by flood-control works: knowl-
edge
that the floodplain is
now
protected up to a 100-year design discharge appears to
give people confidence and encourage
them
to build
on floodplains.
In the other places,
people flock to Alpine ski resorts and encourage the development of settlements
paths of avalanches.
slightly
Elsewhere, waterfront homes are built
above mean high-tide
levels.
in
in the
hurricane zones only
In the latter cases, the recreational
and amenity
101
Adjustments and Their Classification
Sec. 4.6
value of the
often what draws people regardless of the existence of coastal de-
site is
fenses or avalanche protection.
some cases
In
the actual physical existence of environmental control systems gen-
erates the confidence that leads to disaster.
In other cases,
seems
protection against extreme events in nature, the confidence
shared faith
in
the
of this hubris are
sooner or
later,
for those that
first
ventured
many hazardous
in
in
or those that
move
to
and stay
in
places that they
confidence and miscalculation of risk
in
little
or no
widely
to be part of a
sites in total
know
to be
later.
1978, Haas et
al.,
ignorance.
hazardous are many.
no doubt a strong factor
in
many
other instances, each of the occupants
new Alpine ski resorts, and thus
In some cases (e.g.. in the
is
matter.
is
in the
OverIn oth-
cases.
In
more
risk.
hazard zone only temporarily, as
willing to take the risk, or does not consider the
outer islands of the
Ganges
delta or
slopes of volcanoes), the lack of alternative economic opportunity
the choice.
al.,
The reasons
perceived recreational, aesthetic, or economic benefits exceed the perceived
ers, the
In still
is
come
locations (Burton, et
1977) suggests that few people occupy hazardous
people
is
power of technology and our ability to control nature. The benefits
good while they last. However, disaster is almost certain to follow,
Field research
that
where there
affluent societies there
may
on the
often a strong expectation that
is
fertile
literally force
if
the
worst does happen, government disaster assistance will be provided.
Perception, however, can be modified by external influences such as the
news me-
dia or scientific risk assessments, thereby amplifying the social perception of the event
(Kasperson
et al..
1988).
difficult to differentiate
An
amplified risk will lead to secondary responses, which are
from the primary actions but can cause the general magnitude of
the response to grow.
4.6.3 Postindustrial Approach
For
all
its
systems
is
achievements, the application of technology to the control of environmental
increasingly seen to be deficient unless
it
also takes into account both
inherent limitations and the probable future behavior of people in social and
systems.
control.
Failure to
The
do so can
result in the loss of
many of
its
own
economic
the benefits of environmental
application of technology to the control of natural hazards can also pave
way for larger disasters and promote a sense of dependency upon government
among the public and even among large private organizations.
What is now being consciously sought, therefore, is a more flexible response to
the
hazards
in
which environmental control systems
economic policies
development with
that seek to bring
a balance.
be blended with a
set
There are
it
is
now common
of adjustments
set
of social and
about a more harmonious relationship of
the natural environment, especially in
For these purposes,
include within the
will
all
to
its
more extreme
human
fluctuations.
speak of adjustments to hazards and to
possible actions that might be taken to achieve
fives sets, or kinds, of adjustments:
1.
Sharing and bearing losses, or acceptance
2.
Hazard control, or technological control
102
Chapter 4
Natural Environmental Hazards
3. Social adjustments, or regulation
4.
Radical use, change and migration, or relocation
5.
Emergency planning, or emergency measures
These may be thought of as a sequence of changing responses or of learning behavior
of mounting experience with hazards of increasing severity.
in the face
Acceptance.
accept the losses.
it
is
This
The most common response to natural hazards, even today, is to
is true both because many hazard are events are quite minor and
easier to suffer the loss than to spend the time and resources required
response.
Many
ers as a soil moisture deficiency
loss.
become severe
droughts, for example, do not
which
results in a lower yield rather than a total crop
Moderate and expected snowfalls cause delays and inconvenience
cepted with complaints, but with
Where
that are ac-
or no corrective action taken.
little
upon
actual or expected losses have too high an impact
family, or the
on an active
but are recorded by farm-
community, sharing mechanisms are developed.
Where
extended families bring help (Newton, 1992).
assistance widens to the tribe or larger social groups.
formal processes of sharing occur, especially
in
individuals, the
In traditional societies
this is insufficient, the circle
modern
In
societies the
same
of
in-
emergencies, and to these are added the
more formal arrangements of insurance schemes,
disaster relief,
and governmental
as-
sistance including compensation.
A
Technological control.
at
second
set
deep
historical roots but
have reached
of people to control nature
is
of adjustments consists of those aimed
As we have
controlling the natural events themselves.
are generally accepted as
Modern attempts
more effective.
eas.
been alluded to before
is
to
dances to alleviate drought are
to control nature, despite their limitations,
Regulation.
There is a wide range of
human society that can reduce vulnerability to
that has
The wish
Anthropological studies reveal that propi-
long standing.
tiation of the gods, to prevent catastrophic floods, or rain
expressions of this wish.
seen, these adjustments have
their full flowering in the present day.
possible adjustments in the operation of
natural hazards.
An
obvious approach
keep people and property away from hazardous
ar-
This can be done by means of land-use planning and regulations, a particularly ef-
fective adjustment to floods (see Figure 4-2).
Where hazards
are
more widespread and
not confined to definable locations, other planning devices, such as building regulations
(earthquake-resistant structures) or cropping patterns (adjustments to drought and hail),
can be adopted.
Many
social policies have an indirect
ability of a society to natural hazards.
and often unintentional effect on the vulner-
For example, urban renewal or redevelopment
programs may increase or decrease future flood
ruption from snowstorms, and building codes
damage.
losses, transportation policy affects dis-
may change
the extent of tornado-related
An extreme form
Relocation.
gration.
so too
103
Adjustments and Their Classification
Sec. 4.6
Just as hazards are created
may
of social adjustment
For example, residential and other prop-
on the floodplains of the Don and Humber rivers
sorily
land-use change and mi-
they be reduced or eliminated by changing the land use or by (temporary or
permanent) mass migration away from danger.
erty
is
hy human use and occupation of hazardous lands.
Toronto, Canada, was compul-
in
purchased by government after the Hurricane Hazel floods of 1954; the buildings
were demolished and the land use was converted
to
open space for recreational purposes
Similarly, the entire population of the South Atlantic island of Tristan
(Burton, 1965).
da Cunha was evacuated by Britain following a volcanic eruption
Many
people were evacuated from the Mount
in the
in
1961 (Blair, 1964).
Helen's region of Washington after a
Migration away from areas
volcanic eruption in 1980.
known phenomenon
St.
hit
by drought
drought polygon of southeastern Brazil,
is
in the
also a well-
Sahel zone of
North Africa, and elsewhere.
Emergency measures.
Many
and international government
local, national,
agencies have formally established emergency organizations to prepare for and respond
of both human and natural
emergency organizational plans to
to disasters
ing
Preparatory measures include establish-
origin.
facilitate
coping with unexpected events, testing
these plans through mock-disaster exercises, and providing training and education to
designated emergency
response coordinators and response team members.
Public-
awareness material and campaigns complement these focused measures by informing
the general public of their individual responsibilities within larger response efforts.
Adjustments of
made on a continuous basis, guided by experience
The value of preparation cannot be underestimated.
this nature are
gained from previous disasters.
Having the proper resources and a knowledgable operator can save
aster.
Sir Robert
Baden-Powell's motto "Be Prepared" applies to
sessions might be
at risk
due
to a
all
lives
and avert
whose
dis-
lives or pos-
hazardous environment.
4.6.4 Classification
For any natural hazard, there are so many theoretical possibilities for adjustment
becomes
it
mon
use.
helpful to classify
The
first,
them
into types.
already described,
is
Three main classifications are
the distinction
that
com-
in
between those adjustments
di-
rected at control of the environment or the natural processes themselves and those that
involve changes in
human
society or in the pattern of social action and behavior.
In
Western industrial nations, after a period of heavy emphasis on the adjustments of the
first
kind, there has been a general broadening of response to include
more
social ad-
justments.
The second
it
classification of adjustments
is
based on the criterion of timing
specifies those actions to be taken before, during,
ditional societies the adjustments
could be taken during the event.
were often caught
no
avail, as
is
totally
and
were largely confined
In the
after the
to those
hazard event).
(i.e..
In tra-
emergency actions
that
absence of effective warning systems people
unprepared, and emergency actions, including
dramatically observed in the excavated ruins of Pompeii,
flight,
Italy.
proved to
104
Chapter 4
Natural Environmental Hazards
With the
tion has
of modern science and technology, an emphasis on hazard preven-
rise
developed
in
which the occurrence of a natural disaster
lowed by an inquiry and then programs of action directed
Because extreme natural events are the
again".
result of
at
is
almost invariably
"never letting
random
this
fol-
happen
fluctuations in natural
processes, there will always be a future consequence which, given the passage of
enough time, exceeds
the
magnitude of
previously experienced events.
all
Therefore,
all
adjustments after the event are also adjustments prior to the next occurrence, whether
greater or lesser than experienced previously.
The
effectiveness of adjustments in reducing hazard-related losses has to be eval-
uated in terms of the relationship between the environment and the changing character
of
human
settlements.
extreme natural events?
Will society slowly achieve a less vulnerable state in relation to
In other
words, do
adjustments to natural hazard events
ought
more
decrease over time.
to
to learn about
A
how
to
is
we
learn
from hazard experiences?
The fact that they have not done so suggests
manage natural hazards.
third classification of adjustments
is
making
Here, again, a clear trend
that there is
seen in the distinction between actions
taken by private organizations, such as companies, and by government
local to federal.
If
part of a learning process, hazard-related losses
may
be discerned
at all levels
from
of adjust-
in the selection
ments: the rise of large-scale urbanized societies in the modern world has been accom-
panied by a decline
in attention to
adjustments
at the individual
and household
level
and
a growth in the responsibility of organizations, especially governments, to protect people
from natural hazards.
That
hazards there has been a decline
on the
4.7
is,
as has occurred elsewhere, in the realm of natural
in individual self-reliance
and a growth
in
dependency
state.
THEORETICAL PERSPECTIVE:
FUTURE POSSIBLE RESPONSES
In the introduction to this chapter
it
was suggested
that natural hazards are not entirely
natural: while the physical or environmental processes that give rise to
are natural, the intensity of their
extreme events
consequences or impacts depends a great deal on what
people have decided to do or not to do about them.
A
traditional
view of flood hazards
as events in the natural environment that
and damages.
An
alternative
is
illustrated in Figure 4-5a.
Floods are seen
impinge upon human society and cause deaths
widespread view (Figure 4-5b)
is
that the forces of nature
can be controlled or modified to eliminate or lessen the impacts on society.
can be represented as a positive feedback model as shown
in
This view
Figure 4-5c.
Systematic research on and observation of the effects of policies based on the
model or
theoretical approach represented in Figure
4-5c have revealed
that the positive
feedback efforts to control floods also produce negative feedback effects which provide
human
tion
ment
populations with incentives to expand floodplain activities, adding more popula-
and property.
relief
The negative feedback
effect
and rehabilitation programs designed
can be further reinforced by governto distribute losses or share
them with
Sec. 4.7
105
Theoretical Perspective: Future Possible Responses
(a)
Human
Flood Hazard
and
Deaths
Human
Injuries
and
Population
Activities
Damages
Population
Activities to
Control Flood Hazard
(b)
Reduced
Controlled
Human
and Modified
and
Population
Deaths
Activities
Injuries
Flood Hazard
Damages
(c)
Control and
of
Hazard
Reduced
Human
Flood Hazard
and
Population
Deaths
Activities
Injuries
Damages
(d)
Control and
and
Share Losses
and Damages
Distribute
Modification of
Hazard
Human
Flood Hazard
and
Figure 4-5
the wider
community,
man responses
Residual Losses
Population
and Damages
Activities
Hazard models:
I.
as illustrated in Figure 4-5d, in
are indicated.
The
"residual*" losses
which a few of
the possible hu-
and damages can become higher
over time than they would have been without these feedback effects.
Identification
damages has
through research of the processes of reinforcement that increase
led to shifts in public policy.
Chiefly, these changes have been intended to
—
106
Chapter 4
Natural Environmental Hazards
widen the options available
to decision makers, specifically to include a range of social
These include improved policies for sharing
adjustments.
losses, strengthened proce-
dures for emergency planning, and, on occasion, even steps to change land use in more
ways
radical
to facilitate migration
away from hazard zones.
For any given hazard, the range of social adjustments
creased further by research or policy innovations.
is
large
and can often be
in-
In the case of floods, for example, in-
surance has generally not been available from the private insurance industry except on
a very limited scale.
adjacent states
is
Coastal property on the Atlantic and Gulf coasts of Florida and
sometimes insured with Lloyd's of London.
Premiums, however, are
very high.
Among
the reasons for the lack of private insurance against floods
the fact that
is
many householders expect not be flooded during their term of residence, even though
they know that they live on a floodplain. A reason given by the insurance industry is
that the
narrowly defined extent of the risk (only those resident on floodplains) means
that there
fire
is
an insufficiently wide basis over which to spread the
To make
everybody needs
flood insurance
adjustment available to floodplain residents
social
this
States, the federal
government has passed
the United
in
legislation to create a federally sponsored
scheme (Kunreuther, 1977) which
industry and underwritten by the government.
that
risk:
insurance, but only those on flood-prone areas need flood insurance.
A
is
marketed by the private insurance
danger was perceived
in this action
by making flood insurance available, the process of development of floodplain lands
might be accelerated, resulting
this danger, the
U.S.
federal
in
higher damages and big insurance claims.
government requires
sponsored insurance programs, each community must have
To
offset
government-
that to qualify for the
in place a floodplain land-
use plan with zoning regulations approved by the state government.
The conceptual model shown
nic.n
response.
described
specified.
in
Section 4.6,
This
in
Figure 4-5d includes only a limited range of hu-
Findings from empirical research have resulted
is
in
depicted
which a "multiple-means"
in
set
refinements as
in further
of alternative adjustments
is
Figure 4-6.
Consideration of the factors that enter into the selection process has led to the
1964; Burton and Kates,
adoption of a cognitive view of hazards (White,
which
the perception of hazard
nificant variable.
Most of
this
1964)
and adjustments by the decision maker becomes a
model remains
at the
hazard adjustment to everyday places and work
conceptual level and
activities,
in
sig-
fails to relate
or to take into account
choices about livelihood and location, or to account for differences in individual as op-
posed
to collective decision
making.
Some
past four decades in the areas of behavioral
valuable progress has been
made over
the
and perception research of environmental
hazards (Sarrinen, 1966; O'Riordan, 1986), causing the traditional structural approach,
such as dikes and avalanche sheds, to be but one of a number of potential responses
(Smith and Tobin, 1979).
Both empirical and theoretical evidence suggest
that despite a
powerful and grow-
ing ability to excise control over nature by technological means, deaths and
well as other impacts of natural hazards will continue to occur
in
damages
the future.
as
In fact,
damages may well increase and take more catastrophic forms unless management im-
Chapter 4
107
Problems
Control and
Social
Sharing
Emergency
Modify Events
Adjustment
Damages
Radical Use
Change and
Planning
Migration
Human
Adjustments
i
Human
and
i
Population
Activities
«
Flood Hazard
Residual
Losses and
Damages
Figure 4-6
As modern
proves.
Ha/ard models:
II.
more control over their environment, the
some of the most basic natural hazards
protection against overconfidence and naive optimism in attempts to control
fact that success
should be a
societies seek to exercise
eludes us in relation to
still
the environment in
all
its
varied aspects.
PROBLEMS
4.1.
All natural hazards have a natural
terests you. describe
4.2.
and human component.
Choose
a natural hazard that in-
each component briefly and comment on their interaction.
Despite accumulated expenditures of billions of dollars to mitigate the impacts of flooding
in the
United States annual losses have risen from a few million
tury to over SI
billion
today.
Why
do
in the early
twentieth cen-
losses continue to rise despite significant invest-
ments.'
4.3.
Explain
how
the
magnitude of each of the following natural hazards
is
measured and note
deficiencies with this approach.
Floods
(a)
(b) Earthquakes
4.4.
(c)
Cyclones
(d)
Blizzards
Explain
that
in
4.5.
why our
preliminary definition of a natural hazard
causes economic loss or loss of
life)
was incomplete.
(i.e.
an environmental condition
What
four factors are included
the revised definition'.'
Choose
a natural hazard that has occurred in
on the impacts caused.
your area and plot
Explain \our estimation of
how
its
line
on Figure 4-3 based
losses were shared.
108
Natural Environmental Hazards
Chapter 4
Blizzards and flooding are seasonal hazards throughout certain parts of the world requiring
4.6.
With reference
adjustments by the populations affected.
commonly used adjustments
most
to Section 4.6, identify the
impacts of blizzards and floods.
to mitigate the
Comment on
the success or failure of these measures.
For a term project select a river or stream
4.7.
in
your area for which topographic and hydro-
logic data are available and:
(a)
Describe the watershed and any seasonal variations.
(b)
Draw
From
(c)
the annual discharge curve at a
community located on
the river.
the hydrologic record calculate the flood stage for the 100-year flood and plot
it
on a map of the community.
(d) Decide
community is prepared for the 100-year flood? Indicate
damage and comment on possible means of reducing losses.
if this
ticipated
the areas of an-
For a specific natural hazard of your choice prepare a conceptual model of the hazard
4.8.
manner of Figures 4-5 and 4-6
to
show how
the hazard
is
in the
generated and to model the proc-
ess of adjustment.
You work
4.9.
for a regional or state
government where flooding
is
becoming an annual hazard.
Draft a policy statement to deal with this situation and aid in reducing losses.
Consider
both physical and social options.
4.10. In preparation for, or response to, a natural hazard, perception will precede and guide actions.
Select a natural hazard that occurs in your region and describe the perception of this
hazard by the following people.
(a)
Those people exposed
(b)
Government
(c)
Engineers or scientists
(d)
The general public
4.11. Building codes
to the
hazard
officials
who manage
or control the hazard
must consider potentially hazardous conditions.
local or national building
code
that
List those sections in
concern natural hazards and explain
how
your
these rules re-
duce potential losses and protect the general public.
REFERENCE
Algermissen,
S.
T,
et al.
A Study of Earthquake Losses
in the
San Francisco Bay Area: Data and
Analysis. Washington, D.C.: National Oceanic and Atmospheric Administration, U.S. De-
partment of Commerce, 1972.
Auliciems, A. and Burton,
I.
"Trends
in
Smoke
Concentrations Before and After the Clean Air
Act of 1956." Atmospheric Environment 1 (1973): 1063-1070.
Blair,
J.
P.
"Home
to Tristan
da Cunha." National Geographic 125 (1964): 60-81.
"A Preliminary Report on Flood Damage Reduction." Geographic
tawa: Department of Mines and Technical Surveys, 1965.
Burton,
I.
Burton,
I.,
and Kates, R. W. "The Perception of Natural Hazards
in
Bulletin 7 (3). Ot-
Resource Management."
Natural Resources Journal 3 (1964): 412-441.
Burton,
I.,
Kates, R. W., and White, G.
versity Press, 1978.
F
The Environment as Hazard.
New
York: Oxford Uni-
Chapter 4
Bi RTON,
109
Reference
VICTOR,
I..
P.,
and White, A. V. Final Report on the Mississauga Even nation: A Report
the Solicitor-General of Ontario. Toronto:
to
Ontario Ministry of the Solicitor-General.
1981.
Cochrane. H. C.
et al.. Social Science Perspectives on the Coming San Francisco Earthquake:
onomic Impact, Prediction, and Reconstruction. Natural Research Working Paper 25.
Ei
Boulder. Colo.: Institute of Behavioral Science. 1974.
EOM
Girney.
HAAS,
'93." Earth
"The Flood of
F. (ed.).
E.. KATES, R. W.,
J.
MIT
bridge. Mass.:
HEWITT, D.
&
Observation Magazine, September (1993): 23-27.
When Nature
Disaster!
Strikes
and Bov/DEN, M.
J.
Back New York: Bantam/Britannica Books.
1978.
Reconstruction Following Disaster,
Cam-
(eds.).
Press. 1977.
(ed.) Interpretations
of Calamity from the Viewpoint
oj
Human
Ecology. Boston: Allen
Unwin. 1983.
KASPERSON, R.
ysis 8(2)
E. et
al.
"The Social Amplification of Risk:
A
Conceptual Framework." Risk Anal-
H988): 177-187.
Kl NREl CHER, H. Limited Knowledge and Insurance Protection: Implications for Natural Hazard
Policy. Philadelphia: University of Pennsylvania Press. 1977.
LARSEN, R.
"Relating Air Pollutant Effects to Concentration and Control." Journal of the Air
I.
Pollution Control Association 20 (1970): 214-225.
M\(
"A Powerful Earthquake Paralyses Los Angeles." Maclean 's Magazine 107(5). .hum-
Li \\s.
an
31 (1994).
MITCHELL,
K.
J.
Kirby
"Human Dimensions
(ed.).
of Environmental Hazards." In Nothing to Fear.
Andrew
Tucson, Ariz.: University of Arizona Press. 1990. pp. 131-175.
MOGIL, M. and Groper, H.
S.
"NWS
Severe Local Storm Warning and Disaster Preparedness Pro-
grams." Bulletin of the American Meterological Society 58(4), April (1977).
NASH,
R. Darkest
J.
to the Present.
Hours: A Narrative Encyclopedia of Worldwide Disasters from Ancient limes
Chicago: Nelson-Hall. 1976.
NEWTON, J. "Living on the Edge of
ber-December 1992): 10-14.
a Disaster."
Emergency Preparedness Digest
19(4).
Octo-
(
O'RlORDAN,
T.
"Coping with Environmental Hazards."
ment. Vol.
II.
R.
W. Kates and
I.
Burton
(eds.).
In
Geography, Resources, and Environ-
Chicago: University of Chicago Press, 1986,
272-309.
pp.
PALMER, W. C. Meteorological Drought. U.S. Weather Bureau. Office of Climatology Research
Paper 45. Washington. D.C.: U.S. Weather Bureau. 1965.
POST,
J.
D. The Last Great Subsistence Crisis in the Western World Baltimore: Johns Hopkins
University Press, 1977.
Sarrinen.
T. F.
Perception of the Drought Hazard on the Cheat Plains. Research Paper 1056. Chi-
cago: Department ol Geography, University of Chicago, 1966.
SMITH, K. and TOBIN, G.
Human
Adjustment
to the
Flood Hazard. Topics
in
Applied Geography.
London: Longman. 1979.
SUTLIVE,
et al. (eds.).
Natural Disasters and Cultural Responses. No. 36. Williamsburg. Va.: De-
partment of Anthropology, College of William and Mary. 1986.
THOMPSON,
S.
A. Trends
ard Research
ami Developments
Working Paper
in
Global Natural Disasters. 1947-1981. Natural Haz-
45. Boulder, Colo.. Institute lor Behavioral Science, 1982.
110
Natural Environmental Hazards
Thornthwaite, C. W., and Mather.
8.
J.
Chapter 4
R. The Water Balance, Publications in Climatology, Vol.
Centerton, N.J.: Laboratory of Climatology, 1955.
White, G. F,
et al.,
Changes
in
Urban Occupance of Flood Plains
in the
United States. Research
Paper 57. Chicago: University of Chicago Press, 1958.
White, G.
F.
Choice of Adjustment
to Floods.
Research Paper 93. Chicago: University of Chicago
Press, 1964.
White, G. F, and Hass G. Assessment of Research on Natural Hazards. Cambridge, Mass.:
MIT
Press, 1975.
White, G. F, and Tolba, M. Global Life Support Systems, United Nations Environment Programme Information 47. Nairobi, Kenya: United Nations Environment Programme, 1979.
CHAPTER
5
Human
Environmental
Disturbances
Kenneth Hare
Thomas C. Hutchinson
F.
5.1
OVERVIEW
In
Chapter
human
1
we reminded
ourselves of the
existence and the enjoyment of
life.
many
technological improvements
But there
is
no denying
pacts on the environment have occurred even in the most remote places.
have been detected high above the Antarctic continent.
nature are often detected in remote places.
phere from car exhausts, can be found
Untouched
erful disturbers of their
survival
in the glacial ice
on earth depend on
its
that are
beings are the most pow-
their health
much of
the surface.
clearly.
Some
much
huge
size of
extensive.
larger spills have devastated
modern
tankers,
it
and perhaps
their
Oil seeping from ships has
of these occur as small nodules
washed up on beaches worldwide, especially near shipping
there
in
condition.
The oceans show some disturbances very
spread hydrocarbons over
unknown
into the atmos-
of Greenland and Antarctica.
Human
own environment, even though
for
Polluting gases
Synthetic chemicals
Lead compounds, released
forests or grassland can hardly be located.
made
that destructive im-
is
communities
lanes.
Here and
living along shorelines.
Given the
surprising that these spills have not been even
Tritium, radioactive hydrogen-3, from airborne nuclear
bomb
more
testing in the
1950s and early 1960s has penetrated several hundred meters into the ocean waters. As
yet, the
deep waters are largely unaffected, but
pollutants unless
they, too, will slowly
absorb persistent
we change our ways.
Ill
Human
112
Forests and prairies
show
been cleared
North America, for example,
In
At
a different kind of disturbance.
world's original forest cover has
land.
Environmental Disturbances
least half
of the
for agriculture or pasture-
hard to find surviving areas of prairie grass-
is
it
make way
to
Chapter 5
land on the high plains, or of deciduous forest that resembles what the eastern pioneer
saw when they colonized the
Over one-fourth of the carbon stored
settlers
atmosphere as carbon dioxide
to the
by farm animals.
The
world's soil has been oxidized and returned
soil, too,
has been drastically changed.
—because of plowing by farmers and overgrazing
Obviously, people must feed themselves and find firewood, timber,
But doing so has badly damaged the natural environment, and the dam-
and minerals.
age
land.
in the
accelerating.
is
Clearly, there are
two reasons
damage. One
for this
is
that
With the continuing increase
in
world population for
at least
All
cities
reason, however,
is
carelessness, or
and industries continue
agriculture
to
pour
excessive resource consumption and wastage as individuals.
and
scientist is thus obvious: to raise the level
this
lives.
100 years,
is
many of
our
air or water,
us are guilty of
The duty of
the engineer
of technology to the point where the real
needs of humanity can be met, while the environment can
can
to
little
waste products into the
their
often unnecessarily destructive of the soil, and
is
50
the next
we can do
our technology and use of resources are efficient and create as
our
choice but
to make sure that
damage as possible.
even wanton destruction. Too many of
only get more intense.
this legitimate pressure will
The second
we have no
environment: food, minerals, and shelter are essential to our
to exploit the natural
still
But how
be protected.
be done?
The problems to be dealt with occur on all scales. Some problems, such
smoky or malodorous industries, are local and can readily be controlled; the trouble
Other cases affect large regions and involve
disposal, albeit at considerable expense.
Acid
thousands of polluters and millions of victims.
rain (Section 5.3)
is
like this.
It
from emissions of sulfur dioxide and nitrogen oxides from chimneys and exhaust
results
pipes and
now
affects all of northeastern
All of us contribute to
it
Many
affected by the result.
whenever we
other
actions needed to
by questions of scale
effect (Section 5.2)
is
Still
of this
And everyone
light a fire or drive a car.
human environmental
"progress" are covered in detail in Part
The
North America and northwestern Europe.
The greenhouse
other problems are literally worldwide.
tated
is
and can usually be corrected by better methods of combustion or waste
easily located
sort.
as
is
disturbances attributable to
3.
remedy these human environmental disturbances will be dicand by the kind of technology involved. The first job is to
understand the problem: the physician cannot cure the patient before accurately diagnosing the illness.
In particular,
affects other things.
In
one must see the problem as a whole and understand how
environmental management
hensive a solution as possible, because so
is
often
made
difficult
many
is
is
usually best to
things are connected.
because of constraints of a
Air pollution, for example,
it
go
done
may
Unfortunately, this
often found to be relevant to water quality, the health of
be quite simple, even
in these other sectors will
it
compre-
political, legal, or jurisdictional nature.
crops and humans, the corrosion of buildings, and even aesthetic appeal.
pollution itself
for as
be
if
expensive. But repairing the
much more
difficult
Controlling air
damage
and certainly expensive.
already
The Greenhouse
Sec. 5.2
Earlier in this
book (section
move towards
essary part of the
so again in chapter 16
must
strive
that the
1.6)
we argued
that
such technological change
We
sustainable development.
argued there
—
is
— and
a nec-
do
will
engineer has a duty to be concerned with such issues, and
toward quantitative analysis of the problems confronting
respect for quality
The
—
113
and Ozone Depletion: Global Issues
Effect
Strength
us.
lies in
but also for the respectful use of quantified evidence.
interaction
among
water, and land systems
air.
evident in the next three
is
sections that deal with major environmental issues of today: the greenhouse effect,
ozone depletion, and the problem of acid
are almost certainly attributable to
rain.
human
All three are fairly well understood, and
may
Control
activities.
be technically possi-
ble but will be very costly to undertake.
5.2
THE GREENHOUSE EFFECT AND OZONE DEPLETION:
GLOBAL ISSUES
5.2.1 Carbon Dioxide and other Greenhouse Gases
One
now
of the most important environmental changes
mospheric carbon dioxide
coming from
humus
(C0 2
).
in
progress
the burning of fossil fuels, the cutting of forests,
(the colloidal organic
complex
in the soil).
is
likely to be a
a buildup of at-
is
atmosphere
in the
and the wastage of
Moreover, other gases are
added, with similar properties (see also Section 7.3.2).
buildup
C0 2
Undoubtedly, the added
now being
The main outcome of
change of climate, notably toward greater warmth.
is
soil
This
the
may
well affect the world economy.
The atmospheric
C0
2
content
usually measured in terms of
is
relative to all other gases in parts per million
large diurnal variations in the
C0
2
Moreover, concentrations are much the same
C0
of
2
is
well
is
1995 were near 360 ppmv.
recorded from
all
mixed
at all levels in
concentration
in the
in
lower atmosphere.
both hemispheres.
Figure 5-1 shows
has changed since serious monitoring began
year to year
al.,
in
its
Although there are
concentration near the ground (because of the action
of green plants or fuel consumption), the gas
average values
by volume (ppmv).
1958.
A
how
Annual
the concentration
persistent increase
from
monitoring stations throughout the world (Houghton
et
1992).
Unfortunately, we have no systematic records prior to 1958, so we do not know
when the increase started. Preindustrial atmospheric C0 2 was probably near 280 ppmv.
The subsequent increase has been about 75 ppmv. At the Mauna Loa Observatory in
Hawaii, the annual increase since 1958 has varied from 0.5
1974-1975
to 2.2
ppmv
in
1972-1973.
The
ppmv
than earlier in the century but has itself fluctuated considerably.
whole, the increase was
at the rate
of
4%
per decade.
the early 1990's, but appears to have resumed.
Few
The
rate
1962-1963 and
in
recent rate of increase
is
Over
clearly higher
the
1980s as a
of increase slowed
in
other global environment changes
of such magnitude have actually been measured.
Since the mass of carbon in the planet is virtually constant, the increase must be
coming from another storage reservoir. Figure 5-2 shows an estimate of the identified
Human
114
>
E
Environmental Disturbances
Chapter 5
360
Q.
Q.
c
o
c
o
§
320 -
O
O
O
CM
Point
Barrow,
Alaska
300
-J
1955
>
£
1965
1975
1985
1995
1975
1985
1995
1975
1985
1995
360
Q.
Q.
c
o
S
340 -
c
CD
o
c
o
320 -
O
tf0W
eg
o
o
Mauna
Loa,
300
Hawaii
1955
>
£
1965
360
Q.
Q.
c
o
§
340
o
°
320 -
,.""
O
o
South
300 -
Pole
1
1955
1965
Year
Figure 5-1
Alaska,
season
Trends
Mauna
variation
hemisphere.
in
mean annual carbon dioxide concentration at
The annual rhythm
Loa, Hawaii, and the South Pole.
in
plant
and
soil
absorption
All stations round the world
decade. Source: Houghton,
et al. (1992).
and releases, chiefly
show a
similar
in
Barrow,
Point
is
due
the
to the
northern
upward trend of about
4%
per
The Greenhouse
Sec. 5.2
Effect
and Ozone Depletion: Global
and transfer
reservoirs and transfer pathways, with storages
10
9
=
tons
10
12
kg) of carbon per
1995 was believed
to
annum
115
Issues
rates in gigatonnes
The atmospheric
(Gt/yr).
be about 760 Gt. as against 610 Gt
in
(
1
Gt
=
store of carbon in
Three net transfers
1860.
are indicated:
1.
An
addition to the atmosphere of about 5 Gt/yr due to the burning of fossil fuels
and
(coal, oil. gas.
2.
An
plant tissues,
storage
soil
3.
peat),
whose storage
addition to the atmosphere of
is
litter,
assumed
and
soil
60 Gt of
living biomass,
exist for
A
the atmosphere to the oceans of
net transfer
from
These estimates suggest an annual increase of
The average observed increase
is
2 to
equivalent to a
consumption
in
(
this figure is
(the retention rate).
is
(the differ-
in the
atmos-
Hence
under 3 Gt/yr.
may
disagreement about the transfers from living biota, and from
annual atmospheric buildup
63 Gt/yr.
very uncertain.
4 Gt of carbon
the
be wrong, since the fos-
thought to be reasonably accurate.
1) is
at
4 Gt/yr of carbon
little
additions under (2) or the transfers to the ocean under (3)
fuel
Total
and 1670 Gt of
each estimate.
ence between very large two-way exchanges). Again,
sil
litter,
humus. Photosynthesis and respiration transfer are assumed equal
Major uncertainties
phere.
exceeds 5000 Gt.
carbon from the oxidation of
carbon, due mainly to the cutting of forests.
590 Gt of
to be
in the earth's crust
to 2 Gt/yr of
is
wide
ocean.
The
In fact, there
soils, into the
about half the release of carbon by fossil fuel burning
The oceans
are the only identified major sink for atmospheric car-
bon.
Answers
to the question "Will the increase continue?" obviously
future use of fossil fuels
Of
sources.
most
.
on the future use of
and solar power offer any
efficient of the fossil fuels,
Furthermore,
C0 2
to a lesser extent
depend on the
and
soil
forest re-
the available energy options, only nuclear fission (and, in the distant future,
fusion), hydroelectricity,
ural gas, the
and
we now
relief to the
C0 2
adds
realize that other gases
C0 2
buildup.
Even
nat-
to the atmosphere.
have an effect similar
to that of
These other greenhouse gases include methane (CH 4 ), nitrous oxide (N 2 0). and
various synthetics, notably the chlorofluorocarbons
fluorine).
Chlorofluorocarbons have been
lants in spray cans,
behavior.
and for expanding
plastic
Although they are present only
in
(compounds of carbon,
chlorine, and
widespread use as refrigerants, as propel-
in
foam.
All are similar to
C0 2
in radiative
minute quantities, these other gases are be-
C0 2
in warming effect. (World Meteorological Organization, 1981). The
warming may well be double the effect expected for C0 2 alone, and
nearly equivalent in heating effect to a 1% increase in C0 2 per annum.
lieved to rival
global greenhouse
is
5.2.2 Effects of Greenhouse Gas Buildup
The buildup of greenhouse gases inevitably influences the temperature of the atmosphere and the earth's surface. Carbon dioxide emits and absorbs radiation at wavelengths
typical
of the
earth
and atmosphere.
If
its
concentration
increases,
the
s
o\
u «
C/3
c
r
-C
T3
=;
-^
a
C
C
(H
r
^
01)
r
n
—
W)
c
L^
c
<*-.
C
r3
h
<LI
~ E
oo
5
(A
O
£
<r>
p
rl
u
ir,
ca
V
-
>,
^n
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u
51 J3
5
o
X
Q)
DC
O
116
r.
- U
The Greenhouse
Sec. 5.2
Effect
atmosphere offers increased resistance
Since incoming solar radiation
of
C0 2
is
117
and Ozone Depletion: Global Issues
the necessary escape of radiation to space.
to
much
not
affected by the change in the concentration
surface temperatures must rise as a result of the increased resistance to the re-
,
Although not
turn flow.
The height
in the
identical, the influence of the other
slightly (see also Sections 7.3.2
To
greenhouse gases
atmosphere from which the radiation eventually escapes
and
is
similar.
is
also raised
7.3.3).
predict the consequences of this radiative change,
the redistribution of available energy
by winds and.
if
we must
take into account
by ocean currents.
possible,
means of simple one- and two-dimensional models led to
would definitely become warmer as CGs increased, but the calculated warming varied from estimate to estimate.
In 1990, an Intergovernmental Panel on Climate Change (IPCC) brought together
Early attempts to do this by
the conclusion that the earth's surface
expert opinion on future emissions, on various feedbacks that might offset the heating,
and on the
sensitivity of the
atmosphere to such altered energy inputs.
Figure 5-3,
taken from a 1992 update (Wigley and Raper, 1992). shows on the left-hand side the
range of future emissions of carbon thought possible, to emphasize the high degree of
Also shown
uncertainty.
may
this
lie
the corresponding concentration of
is
CGy
between 485 and 985 ppmv, a range of over 100%
By
the year
in uncertainty!
2100
The
curves on the right-hand side show the corresponding prediction of temperature and sealevel
we
change, using a simple model. Clearly,
are
nowhere near
certainty about future
outcomes.
More
elaborate models are used to represent the general circulation of the atmos-
phere and oceans, which transport heat and moisture.
(Houghton
1.
If
business as usual
is
assumed
no new control measures), global mean
(i.e.,
face air temperature will be about
1
C
may slow this warming
60% will be needed even
If control
measures are introduced
promptly, they
but are unlikely to stop
tions of over
to hold concentrations at present levels).
it
(because reduc-
The warming may be more pronounced over southern Europe and
America, accompanied by reduced summer
3.
Global sea level
is
expected to
rise
rainfall
by about 20
cm
and
soil
Global mean surface
air
central North
moisture for crops.
by 2030 and by 65
end of the twenty-first century (more recent estimates suggest lower
4.
sur-
higher by 2025 than in 1990, and 3°C
higher by the end of the twenty-first century.
2.
IPCC reviewed 22 such models
1990) and concluded as follows:
et al.
temperature has risen between 0.3 and 0.6
cm
by the
figures).
K
in
the past
century, and sea level has risen by 10 to 20 cm.
These predictions of
ica,
some good and some
1.
A
decrease
creases
2.
A
in
in
rising temperatures
bad.
The good
have major implications for North Amer-
effects
may
include the following:
space heating costs due to warmer winters, partly offset by
in-
air-conditioning costs.
longer growing seasons lor crops, and hence the possibility of better harvests
in
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The Greenhouse
Sec. 5.2
119
and Ozone Depletion: Global Issues
Effect
northern regions, again partly offset by decreased yields farther south (where sum-
mers are often too warm for good crop
3.
Much
yields).
easier navigation, and for a longer period during the
summer,
in the
Arctic
seas (e.g., Beaufort, Bering, Baffin Bay) and in the Canadian Arctic (Hudson's
Bay and
Strait,
Lancaster Sound, Barrow
Strait,
and other
straits),
together with
easier conditions for offshore oil and gas development.
Less welcome effects
4.
Canadian
and
sive
many
Prairies, requiring
parts of the
still
midwest and Great
Plains, including
greater use of irrigation water, already expen-
in short supply.
Widespread melting of the permanently frozen ground (permafrost) now underly-
many
ing
parts of
Alaska and northern Canada.
ogy and conditions
Such changes are
who
as follows:
Drier crop conditions in
the
5.
may be
for road
still
This will alter building technol-
and pipeline construction
hypothetical and
may
never take place.
suggest a smaller effect on atmospheric temperatures.
in the early
in these areas.
Such
There are sceptics
conflicts are
common
days of studying natural systems. They arise from the difficulty of incorpo-
rating adequate detail into the
boundary conditions of the models and
their different sys-
tems of equations.
5.2.3 The Ozone Depletion Problem
As
shown in Chapter 7, the solar radiation reaching the earth's surface is sharply
290 nm (see Figure 7-2, curve 3), although the radiation entering the
top of the atmosphere includes considerable amounts at shorter wavelengths. The reason is that small quantities of ozone (0 3 ), chiefly in the layers between 15 and 40 km
will be
cut off at about
above ground
level, filter out the
missing radiation and use
it
to
produce the
warm
con-
ditions of the upper stratosphere (see Figure 7-1).
— needed
damages DNA in the husome cases skin cancer owes its existence to the
ultraviolet itself. All living tissues are to some extent at risk. This energy-rich radiation
is capable of splitting
2 molecules, and the single O molecules can combine with
2
to create Gy This process has been in progress ever since free oxygen first entered the
This protective layer
man
skin,
producing sunburn and
since ultraviolet radiation
—
in
atmosphere, as the result of photosynthesis.
more powerful
In
ultraviolet
is
filtered out
nature, the creation of
3
is
Life has flourished on earth because the
completely.
continuous as long as the sun shines, yet the
amount of 0^ remains small and is largely confined to the stratosphere. This is because
ozone is attacked by other gases diffusing upward from the earth's surface. The most
important of these in nature is nitrous oxide (N 2 0), emanating from the soil and from
certain industrial processes.
attacks
Ov
In the stratosphere
it
is
quickly oxidized to
NO, and
this
This and other processes create a natural equilibrium: ultraviolet irradiation
creates ozone, and other natural processes lead to
its
decay.
Human
120
Environmental Disturbances
Chapter 5
human economic activity has added other compounds capable of
The chief of these are chlorine compounds, notably the chlorofluoro-
Unfortunately,
attacking ozone.
carbons, already discussed because of their role as greenhouse gases.
In the lower and
middle stratosphere these compounds are broken up to allow free chlorine atoms
ist,
to ex-
many samples
Since the process was identified in 1974,
and these attack ozone.
have revealed high concentrations of chlorine dioxide, a by-product of the ozone-de-
But the chlorine dioxide
stroying process.
This
is
far greater than the
is
Moreover, the effectiveness of ozone destruction
clouds are present.
may
spring
—
fall
below 200
essentially in
K
and
losses
seems
is
quickly
A
repeated.
it
when temper-
In the Antarctic
low and decreasing ozone
known
But the
up.
as the
ozone hole.
intensity of the spring
although on a smaller scale, have
effects,
is
ozone hole
in
not yet certain that this
—
1981 —
These quite recent discoveries
the
made
stratospheric
if
small general decrease in ozone seems to have affected
other areas, notably in spring, although
phenomenon of
or below.
This has become
be increasing, and similar
in the Arctic.
destruction.
K
—remarkably
the sun returns, the loss
to
180
in the Antarctic to
October and November
When
been feared
enhanced
is
This occurs only in the great cold of the polar night,
amounts have been recorded since 1975.
the
is
amount of CFCs
would imply.
released
atures
and the cycle
itself dissociates,
a catalytic process, so that the ozone loss
the threat
was
illustrate the
is
due
to chlorine
identified only in 1971,
and
importance of atmospheric
chemistry, and in particular the small quantities of active chemical species that have so
striking a climatic effect.
Like the greenhouse
This
may be
ozone depletion problem
effect, the
The atmosphere
tackled only by world action.
worldwide and can be
is
an efficient diffuser of pollutants.
is
But
useful in dispersing local air pollution.
it
also guarantees that insolu-
ble gases can be spread throughout the atmosphere and thereby create chemical imbal-
ances that
we
did not foresee
—but must now combat.
5.2.4 Control Measures:
The Climate Change Convention
At the U.N. Conference on Environment and Development held
Rio de Janeiro
in
in
June 1992, the nations present adopted a Climate Change Convention that confirmed the
seriousness of the greenhouse
warming and ozone depletion problems and
called for ac-
In particular, the convention identified national actions that
tion to abate the threat.
should be taken to stabilize greenhouse gas emissions and to bring the ozone depletion
problem under control.
that attack
ozone are
turers' plants).
everyone
is
The
latter is
identified
source
(i.e., at
is
more
the manufacdifficult since
a contributor.
ships, or oil, natural gas,
main source of
is
at the
But control of other greenhouse gas emissions
Fossil fuel consumption,
gineer
a technologically tractable issue, since the gases
and can be controlled
C0 2
whether
and coal
buildup and
is
oil
and gasoline
in electricity
clearly vital to
faced with the urgent need to
in
cars,
planes, trains, and
generation and space heating,
move toward
human work and
comfort.
greater energy efficiency
is
the
The enand away
The Greenhouse
Sec. 5.2
from carbonaceous
One such measure,
is
But such
fuels.
much
Accordingly,
take effect.
and Ozone Depletion: Global
Effect
efforts,
even
ital
the technological removal of
it
is
sponsored nationally, will be slow to
if
attention has been given to other possible measures.
and
feasible but prohibitively energy intensive
ergy has argued that
121
Issues
C0
2
from
costly.
feasible only in an all-electric
flue gas
and exhaust pipes,
The U.S. Department cf Eneconomy, since otherwise, cap-
investment requirements are out of the question. (U.S. Dept of Energy 1980b.) For
centralized flue emissions, removal by
monoethanolamine (MEA) absorption/stripping
the least energy-intensive technology available, but net
from an assumed
38%
for zero
removal
20%
about
to
deep ocean, which would add further costs and pose a
attempt to increase
and
fiction
plant efficiency
is
for complete removal
is in
C0
2
threat to the
is
reduced
—
a
Disposal of the immense volume of carbon removed would have to be
burden.
Any
power
huge
in the
ocean carbon cycle.
absorption by the oceans seems in the realm of science
any case dangerous given the present unsatisfactory
of knowledge
state
of the oceanic carbon cycle.
Of
seems
other possible measures, only the control of biotic and soil carbon exchanges
of carbon
trees,
on other grounds as well as for the removal of
useful,
in biota, chiefly in the
woody
C0 2
.
The present storage
stems, branches, trunks, and roots of shrubs and
has been variously estimated from about 500 Gt to over 900 Gt, with annual ex-
change
rates
storage
is
due
to photosynthesis
and respiration
in the
range 45 to 70 Gt/yr.
thus comparable to the carbon mass in the atmosphere.
This
Forest clearance, with
subsequent use of the land for less efficient carbon storage, obviously transfers carbon
atmosphere, chiefly due to burning.
to the
atmosphere as
fer to the
age
in soil is
A
recent careful estimate puts the net trans-
to 2 Gt/yr, although higher estimates are also current.
estimated to be in the range 1450 to 1730 Gt, about
the agricultural revolution.
25%
Stor-
less than before
Present-day transfers of soil carbon to the atmosphere are
variously estimated from negligible values to one remarkable figure of 4.6 Gt/yr.
Forest clearance for agriculture and the reduction of forest biomass because of
Most of
poor forestry practices are clearly within the realm of possible management.
the storage
is
in the tropical rain forest,
Large amounts are also stored
It
which
is
rapidly being converted to other uses.
in northern forests (about
one-eighth of the world
has been estimated that total forest storage in Canada alone
38 Gt
is
stored in the high northern muskegs.
is
44 Gt and
total).
that a further
Good forest management should aim at
Much forest exploitation works today
a high level of stored biomass, or standing crop.
other direction.
in the
forestry in
which
In fact, the
may
it
world now faces the need for an era of
two
centuries.
The
political difficulties of reconciling the interests
The
final
outcome of
the debate started
very great, and have not yet been resolved.
by the Rio Conference
is
achieved
—
is
of so
is
as yet unclear.
many differing countries are
is now clear to us all: that
What
is
needed
—once
political con-
a broad approach that recognizes the interrelated character of
aspects of the environment.
ply, sea-level,
managed
But one thing
simple, one-dimensional solutions will not work.
sensus
fully
be possible to rebuild some of the biomass losses of the past
The greenhouse
effect, for
all
example, touches on food sup-
and hence the safety of the teeming but productive deltas of the tropical
countries; on forest yields (and the need for forest protection); and most of
all
on the
Human
122
Environmental Disturbances
Chapter 5
problem of human numbers, resource depletion and the well-being of future genera-
The need
tions.
now obvious
5.3
to
manage our environment
to
responsibly, the subject of Chapter 16,
But only broad-gauge measures
all.
is
will help us.
ACID RAIN: A REGIONAL ISSUE
5.3.1 The Nature of the Problem
Acid Rain,
wet and dry acidic deposition,
the label regularly given to both
was
recent addition to our language. Although the term
the British chemist
Angus Smith from
actually coined
was developed
in northern
1950s that the widespread occurrence of acid rain was recognized.
acid rain has been a major concern as
Acid
rain occurs within,
sulfur dioxide
S0 2
After
and
(S0 2 ) and
NOx
Normal, clean rain
and downwind
is
to earth as
decade,
of major industrial emissions of
into mild sulfuric or nitric ac-
C0 2
weak carbonic
pH
sleet,
snow, and
level of about 5.6.
in the air,
which dissolves
acid solution.
America and northern Europe where heavy
pH
last
was
in the
(NO,) (Environment Canada 1981).
dew, drizzle, fog,
slightly acidic, with a
extent in the droplets to give a
with a
of, areas
combining with water vapor,
the equilibrium between rainwater and the
falls
For the
it
continues to defile major areas of our planet.
the oxides of nitrogen
These acids then return
eastern North
Europe
are emitted into the atmosphere, they are transformed into sulfate
or nitrate particles and, by
ids.
it
a fairly
is
10 years ago by
Manchester, England,
his studies of air in
not until a rain quality monitoring network
1
on
fish
is
due
to
to a sufficient
Today, over wide areas of
rainfalls
value close to 4.0 and, on rare occasions, 3.0.
largely to the effects of the acidity
rain.
This
predominate, rain
The concern
relates
populations and other aquatic animals, to po-
damages to crops and forests, and to accelerating deterioration of building mateeven seems likely that acidified rains may enter the groundwater storage and
increase the solubility of toxic metals. Acid waters can also dissolve metals, such as
tential
rials.
It
These problems are now very wide-
lead and copper, from hot and cold water pipes.
spread.
The
potential effects
are enormous.
on tourism and on the recreational uses of lakes and
rivers
Estimates for Ontario alone are for a multimillion dollar loss of tourist
dollars per year unless the
problem
is
ameliorated.
5.3.2 Sources and Distribution of Acid Rain
The
pollutant material that
particulates
comes down with
and gases scavenged from the
ground by gravity during dry
lates, gases,
and aerosols.
may
wet deposition, and includes
by raindrops.
intervals, is called
Pollutants
ometers by prevailing winds.
rain, is called
air
The material reaching
the
dry deposition, and includes particu-
be carried hundreds or even thousands of
kil-
known as the long-range transport
Svante Oden from Sweden demonstrated that
This phenomenon
is
of airborne pollutants (LRTAP). In 1968,
the precipitation over the Scandinavian countries was gradually becoming more and
more
acidic, that sulfur
compounds
in the polluted air
masses were primarily responsi-
Acid Rain:
Sec. 5.3
ble.
and
A
123
Regional Issue
came from emissions in the inSoon afterward, data on changes in lake
Trajectory studies in North America have demon-
that large quantities of the acidifying substances
Europe and
dustrial areas of Central
were developed.
acidity with time
more than 50% of
strated that
Britain.
the deposition of acid rain in central Ontario
masses passing over the major sulfur-emitting sources
midwestern
in the
United States, especially Ohio and Indiana (Environment Canada 1981).
the
Adirondacks and southern Quebec, on the other hand, often appear
igins in the industrial eastern seaboard states of
and from Pennsylvania and other
land,
states
New
to air
Acid rains
to
in
have their or-
York, Massachusetts, and Mary-
over which the air has previously passed
The Canadian maritime provinces
(Figure 5—4).
due
is
states of the
from the
are affected by emissions
U.S. eastern seaboard and also on occasions from smelter sources in Ontario and Que-
More
bec.
than
10% of
the acid rain that falls in the northeastern United States
comes
from Canadian sources.
Figure 5—5 depicts the distribution of emissions of
ica.
S0 2
Figure 5-6 shows the areas vulnerable to acidification.
NO
and
The
North Amer-
in
v
lines indicate the inci-
dence of wet sulfate deposition, and the numbers show the levels of deposition
kg/ha
Levels of deposition exceeding 20 kg/ha
yr.
regarded as threatening
same
threaten the
given
in
vulnerable areas.
•
in
yr) are generally
shown on
Nitrate depositions, not
the
map,
areas.
A
comparison between sulfur and NO, sources
in
Table 5-1.
The major contribution from
jor sulfur-emitting states
tucky, while the
yr (18 lb/acre
•
is
apparent
in
in several states
Ohio, Pennsylvania, Indiana,
predominance of the nickel-copper smelters
source for Ontario (and beyond)
emissions have been dispersed
tall-stack pollution dilution
also noted.
is
in the
late
in
Ontario
is
maand Ken-
at
Illinois,
Sudbury as a sulfur
In all cases, these very large
atmosphere as a
technology of the
and
coal-fired generating plants in the
result of the
source
development of the
1960s and 1970s and
now
contribute
to regional acid rain problems.
in the fro/en snowpack in regions subjected to acid
The first major melt of the spring releases the majority of the acidic accumulation, which runs off as meltwater over still-frozen soil and quickly enters the rivers
Acidic materials accumulate
deposition.
and streams.
One consequence
is
the sudden intrusion into lakes of a "p' u t
waters, especially in their shallow inshore areas.
pression"
in
Ontario.
As
one of the
six inflowing
aquatic
The
life.
spawning
streams to Harp Lake, a study lake
the spring runoff increases the
melted snow causes the
fish are
pH
to
amount of water
in
in
pH
de-
Muskoka.
the stream, the acidic
drop, producing severe chemical
disastrous effects of this type of
considered
°f acidic
Figure 5-7 shows the "spring
"shock effects" on
phenomenon on shallow-water
later.
5.3.3 Effects of Acid Rain on Aquatic Systems
The most important
tions,
which
economic.
is
effect of acid rain
especially
damaging
Other aquatic effects
on aquatic systems
to sports lishing.
oi acid rain
The
is
include those on
ing an increased concentration of metal in their flesh
the decline in fish popula-
indirect result
on tourism
humans who
and the reduction
is
eat fish hav-
ot certain
groups
Human
124
SUMMER
Environmental Disturbances
Chapter 5
WINTER
ATLANTIC
OCEAN
(b)
(a)
Figure 5^4
and
Storm
(b) winter.
Note:
trajectories over
Source:
S0 2
major
-
NO
and
A
-emitting areas in (a)
summer
Ontario Ministry of the Environment (1980).
U.S. emission rates from the
SURE
II
data base are 1977-1978 emission rates
for
area sources.
Canadian data from Environment Canada are estimated 1978 emission rates for major S02
point sources and 1974 emission rates for other area sources.
Storm trajectories by J.
Kurtz, meteorological scientist.
Environment Ontario based on 40 years of data. U.S.
Weather Bureau.
EASTERN NORTH AMERICA: MAJOR S0 2 AND N0 2 -EMITTING AREAS
-
Geographical area
1.
East and West Pittsburgh:
8.
Upper and Central Ohio
9.
River Valley
2.
New
3.
Toledo, Ohio; Detroit,
4.
Western Kentucky;
York,
New
Jersey
Michigan
5.
6.
7.
Grams/s
southern Indiana
Chicago, Illinois
Cincinnati, Ohio;
northern Kentucky
Cleveland, Ohio;
western Pennsylvania
98,718.7
81,892.2
10.
65,421.6
53,623.7
53,040.7
Geographical area
Grams/s
Sudbury, Ontario
Lower and Central Ohio
River Valley; Clarksburg,
43,915.3
West
42,401.3
Virginia
Eastern Missouri,
Illinois
11.
Indianapolis, Indiana
12.
Western Kentucky
13.
Mobile: southern
Alabama
50,051.0
14. Toronto, Ontario
15.
47,997.7
16.
41,298.8
30.202.9
25,849.3
Rouyn-Noranda, Quebec
Southern Louisiana
24,138.5
18,584.7
16,404.2
14,596.8
Sec. 5.3
A
Acid Rain:
125
Regional Issue
5-1
QUANTITIES OF S0 2 AND NO x
EMITTED ANNUALLY FROM VARIOUS
US STATES AND ONTARIO
TABLE
Sulfur dioxide
Nitrogen oxides
(10 3 tons/yr)
(10 3 tons/yr)
3259
1187
Ohio
(Reduced
to
2700
I980)
in
Ontario
2495
2 00"
Indiana
1891
960
Illinois
1
707
1274
Pennsylvania
1023
Unknown
1
Kentucky
1
63
569
I
Texas
154I
2117
Missouri
1507
61 x
Tennessee
1
277
560
Arizona
1239
276
West Virginia
1226
471
Michigan
1225
742
Alabama
1038
511
New
1022
906
675
1284
York
California
'Includes emissions from Ontario
Hydro and smelters from
the
Sudbury complex.
Government of Ontario
Source:
J^stf*
t>3^
(
-
/
I
1981.
r^o \^^\ CV
^
\
report.
•
v^\*
/J )\S
u
*
//
**
•
• •
•
•
f
* •
^v^,»
(a)
Figure 5-5
Source:
Distribution
ol
emissions
Environment Canada (1984)
oi
(a)
sulfur
dioxide
(SO
,);
(hi
nitrogen
oxides
(NO,).
126
Human
^m ^
Chapter 5
/^*° x^X. $
^
V
Environmental Disturbances
1
>^J
IT?
X7
1
Figure 5-6
acidification,
Areas vulnerable
surficial deposits.
Appfiunrtjtc
j
M (I'jwl
i'l,r4(i'.>|.|i
to
based on bedrock geology and
Source:
Environment
Canada (1984).
15.0
10.0
fi
-
5.0
6.50
=
600
-
5.50
-
March
Figure 5-7
Spring
Environment (1980).
pH
depression of a stream.
Source:
Ontario Ministry of the
Sec. 5.3
Acid Rain:
A
127
Regional Issue
of zooplankton. algae, and aquatic plants, which disrupts the overall food chain in lakes,
thereby causing potential ecological imbalances.
trout
Studies have clearly demonstrated that
and Atlantic salmon are particularly sensitive
low
to
pH
levels,
which
interfere
with their reproductive processes and frequently lead to skeletal deformities (Beamish
al.,
et
1975).
High aluminum concentrations
that kills fish
waters are often the actual trigger
in acidifying
and probably other sensitive biota, such as planktonic crustaceans.
aluminum concentrations
previously insoluble aluminum
are very low.
kaline or near-neutral lakes,
however, the
creases,
that
is
As
present
in
the
In al-
pH
very
de-
high
concentrations in rocks, soils, and river and lake sediments begins to go into solution
Once
(Figure 5-8).
aluminum
in solution,
low concentrations
life at
(i.e.,
from
increases exponentially below a
higher
is
0.1 to
pH
1
remarkably toxic to many forms of aquatic
mg/L).
Although aluminum concentration
of about 4.5 to 4.7, toxicity to fish occurs at a
pH than this. Studies at Cornell University by Baker and Schofield (1980) show
maximum toxicity of aluminum to fish occurs around pH 5.0. This is due to
that the
the rather
complex chemistry of aluminum,
tios in solution
change with pH.
extremely toxic. At a
pH
mg/L
which the chemical forms and
their rais
of around 5.0 the hydroxyl forms predominate, and the toxic-
declines above and below this
ity
for
Free ionic aluminum occurs mainly below 4.2 and
or greater cause fish
gill
pH
At
level.
damage and
pH
5.0,
aluminum concentrations of 0.2
mucus onto the gills in brown
secretion of
it* •
iQ.
6.0
• •
• •
i
••
•
.
• •
5.0
-
m
• • •
•
••••
•
• •
>:•
4.0
100
200
300
400
500
600
700
Al (ug/L)
Figure 5-8
Source:
Relationship between lake
Dickson (1980).
pH and
total
aluminum
in
some Swedish elearwater
lakes.
Human
128
and
trout
in
whitesuckers.
Environmental Disturbances
The slimy mucus appears
to plug the gills, causing respira-
In addition, the essential integrity of the
tory problems.
Chapter 5
semipermeable
gill
membranes,
through which exchanges of gases and salts take place, is altered. It thus seems that not
only can an increase in H + ions cause fish kills and declines in populations, but also
that
aluminum can be an
5.0,
and
Although
duce.
pH
certainly at
fish
Yearlings
additional and perhaps crucial toxic factor in waters around
4.0, (Harvey, 1980;
can die of acidification, more
fail to
pH
Harvey and Pierce 1981).
commonly
they simply
fail to
enter the stock or else enter in low numbers, and after a
repro-
number
of years of this reproductive failure, which produces an increasingly old population, the
species eventually disappears from the lake or stream.
failure of year classes
•
About
illustrated
This aging of a population and
by the data on yellow perch for Patten Lake, Ontario
(Harvey, 1980; Beamish and Harvey. 1972).
(Figure 5-9).
Some
is
of the areas affected by acid rain are as follows:
a
dozen
rivers in
Nova
Scotia, far
removed from
local
upwind pollution
sources, no longer support healthy populations of Atlantic salmon.
•
About 200 lakes
in the
New
Adirondacks of upper
York State no longer support
35
Patten Lake
30
25
20
CD
E
15
10
-
Figure 5-9
Age composition of yellow
pereh from Patten lake, Ontario.
Sonne:
(
4
Age
5
6
(Years)
7
10
1980).
P.
M. Ryan and H. H. Harvey
© 1980 by Dr. W. Junk
Copyright
Publishers.
Reprinted by permission of
Kluwer Academic Publishers.
A
Acid Rain:
Sec. 5.3
brook
trout
129
Regional Issue
Thousands more lakes
and smallmouth bass.
in the area are losing
their capacity to buffer acid rain, (Harvey, 1980).
•
Of
4016 lakes
the
tested in the Province of Ontario, 155, or
of 2896 lakes had
some
A
total
D. W. Schindler (personal
susceptibility to acidification.
communication, 1987) suggests
4%, have been found
extremely limited.
to be acidified, with their ability to support aquatic life
that these estimates substantially understate the
magnitude of the problem.
phenomena have occurred
Similar
in
southern Norwegian rivers, in a good
lakes in Galloway, Scotland, and in the Erzgebirge region in East
many
Germany, where
fish
populations have either vanished or suffered marked reductions over the past 30 years.
Many
rary pools
are
species of amphibians
formed by spring
exposed
rains
(i.e.,
to the springtime acid shock,
established that
80%
and salamanders) breed
frogs, toads,
in
tempo-
and melted snow. The eggs and developing embryos
and deformity or death occurs. Fieldwork has
of salamander eggs failed to hatch in waters with a
pH
below
level
6.0.
For the cricket frog and northern spring peeper, an exposure to waters with a
level
of about 4.0 resulted in more than
members of both
sects
85%
Amphibians
mortality.
As both major
the water and land ecosystems.
pH
are significant
predators of aquatic in-
and high-protein food for many birds and mammals, they are important links
in
the food chain.
Some groups
of biota, such as the molluscs, which include animals with shells
(e.g., snails, limpets,
mussels, and oysters) are strongly dependent on calcium for their
outside skeletal protection.
Many
Since acid water readily dissolves calcium carbonate and in-
calcium uptake by these organisms, they cannot survive
terferes with
in
such waters.
of the crustaceans (lobster family) in the small free-swimming group
as zooplankton (microscopic animals in the water
creased acidity of fresh waters.
sources of food for
effect of the acidity
Since
fish, their loss
on the
fish
many
Green plants
to in-
of these zooplankton are very important
could eliminate certain
fish species
without any direct
themselves.
Finally, in considering food-chain effects, the
be recognized.
known
column) are also very sensitive
key role of the green plants has to
are the support system for the entire aquatic biota, since
they are the only organisms able to
fix
carbon
the essential carbohydrates, fats, and proteins.
(in the
presence of light) and so produce
Their demise would cause a direct col-
lapse of the food chain.
5.3.4 Effects of Acid Rain on Terrestrial Ecosystems
on forests. The forests of Canada, the United States, and Scandinaenormous economic importance. Hundreds of thousands of people are emthe various wood- and forest-associated industries. One in 10 Canadians is
Effects
via are of
ployed
in
employed
ilar
directly or indirectly in such industries,
employment
tourist
profile.
In addition, the forests
and recreational areas.
Acid
and Sweden and Norway have a simand lakes
in
rain poses an insidious
these countries are major
and potentially devastating
Human
130
threat to our forests.
acidic rain
(pH
Environmental Disturbances
has been shown that seedlings can be
It
in Central
fir
is
is
of rain in
in
fall
to
at the
the past 25 years,
areas, has
Germany
western
combined with
are also in
less well-buffered
whereupon
these fine roots,
and acidic snow-
the high
same time has increased aluminum concentrations
When
uptake into the fine absorbing roots
ity in
in
growth decline on the
caused leaching of calcium and magnesium from the
Thus, the Ca/Al ratio has been reduced.
num
in a
Bernhardt Ulrich of the University of Gottingen, the increased acid-
Germany over
mountainous
and
soils,
Mountains and the Black Forest
1980).
According
ity
Thousands of hectares of spruce and
in the past 15 years. The
a catalyst for such concerns.
beech and spruce dying or
(NATO,
soils
dam-
Czechoslovakia and eastern Germany have died
forests of the Hartz
trouble, with
in in-
Direct, visible acid rain
not being seen, but the dramatic and striking death and dieback of trees
Europe
forests in
damaged by moderately
Researchers are beginning to evaluate the role of acid rain
4.6).
creasing the vulnerability of trees to disease and insects.
age to foliage
Chapter 5
this
molar
in the soil solution.
ratio falls
below
favored, and this results in
is
may
the roots
1.0,
aluminum
die or have reduced vigor.
alumitoxic-
This in turn
allows the entry of pathogenic (disease-causing) bacteria and fungi which infect the
trees
and gradually play a role
concentrations in the
vere
in their decline.
soil solution
summer droughts have
The occurrence of increased aluminum
has been especially prominent in years in which se-
occurred, such as in 1975 and 1976 in Europe.
Under those
circumstances, the aluminum concentrations are increased as a result of the drought-in-
duced concentration of the
Germany have
soil solution.
Certainly, the rates of forest decline in western
accelerated markedly since 1975.
and around western Germany
is
The high
of the mountain areas, where effects are most severe.
cloud waters bathe the trees
in
level of industrial activity in
believed to be a key factor in
this,
as
is
the high rainfall
In higher-altitude forests, acidic
fog for long periods each year.
Figure 5-10 illustrates
the effects of acidic air pollution.
One
of the greatest difficulties
effects of acid rain
on
it
is
we
face in studying forest growth and the possible
caused by normal climatic fluctuations and by insect attack.
fold
est
from year
to year.
It is
extremely
difficult, therefore, to
growth decline over a short period of time.
made use of
from year to year
Growth can differ several-
the very considerable variation in growth
the annual width of
wood
down
laid
pick up small trends in for-
Assessments of
this
type have usually
in tree trunks as annual rings.
Such
studies have been done in the United States and Norway. All have made use of a limited amount of data, have had difficulties in taking account of the differential normal
growth at different ages within a species, and have been inconclusive. One American
study suggests that "acid rain merits strong consideration as a factor suppressing tree
growth
in the
Pine Barrens of
can be inferred from the data.
New Jersey," but others
We thus have a most
might be facing a serious decline
in forest
suggest that no clear conclusions
frustrating situation in
vigor but are unable
at this
which we
time to sort out
the various alternative explanations.
In experiments,
acid has been sprayed in the field or in controlled laboratory
(greenhouse) conditions.
Several of these studies have
increasing acidity of the spray
down
to
pH
3.0.
shown an enhanced growth with
In a study
by the U.S.
Environmental
Sec. 5.3
A
Acid Rain:
Figure 5-10
(a)
(Photos courtesj of T. C. Hutchinson.)
Effects of acidic air pollution,
Severely affected region located about 8
per smelters
In
the province of Ontario
km
The
from two of the Sudbury area nickel-copforest destruction
about by sulfur dioxide fumigations over
many
stunted birch and red maple remain here.
Soils
with heavy metals.
(b)
131
Regional Issue
Aluminum
Die-back and decline
ual loss of
seen.
This
of
is
spruce
is
similar to
much
has largely been brought
Conifers are absent and only
have been
acidified
and contaminated
solubilized in the strongly acidic soils.
in
needles from the top
years.
the Adirondack region of
of the forest
New
York State.
The grad-
and from the tips of the branches can be
damage in Germany.
of the tree
Human
132
Protection
Agency (Lee and Neely,
Environmental Disturbances
1980), increased seedling growth occurred in four
were unaffected down
species, while seven others
Chapter 5
pH
to
was a
ing to soil properties, the growth effect
3.0.
was suggested
It
fertilization
that
ow-
of sulfur uptake
effect
through the foliage.
The most
down
was done on Scots pine stands
detailed study
Applications were
Tollan, 1980).
made above
served in the
first
pH
four years of the experiment, even at
upon by some as "proof
beneficial fertilization effect
It
effect
was
attrib-
Unfortunately for
Norwegian data reversed this trend, showing a
with acid as compared with the control plots. The
the
was apparently overcome by
is
the detrimental acidity-alumi-
important to realize that acidic
by themselves, are not harmful
soils,
to plant
Acidification of soils and leaching of nutrients from them, especially of cal-
cium, magnesium, and other bases, are normal
extending worldwide
in
developed since the
acid rain hazard
is
last
major glaciation of 10,000
whether the increases
to
vast boreal forests
in acidity will
The
12,000 years ago.
The question we
old to which they are not physiologically adapted.
known.
The
soil processes.
high latitudes of the northern hemisphere are growing on acid
plants are, therefore, adapted to the acid soil.
ently
values from 5.6
effects.
growth.
soils
The
2.0.
that acid rain will only benefit the forests.
two years of
decline in growth in the plots treated
num
pH
These data have been seized
uted to nitrogen fertilization from the nitric acid additions.
this hypothesis, the last
at
and diameter growth were ob-
In Scots pine saplings, increased height
to 2.0.
Norway (Drablos and
in
canopy and
the
face in evaluating the
push these forests over a thresh-
The answer
is
crucial but
Certainly, the decline of red spruce in eastern North
is
not pres-
America
documented (Klein and Perkins, 1987). and the spread of sugar maple dieback
bec and adjacent areas since 1982 is cause for great concern.
well
is
in
Que-
Another effect of acid rain on forests includes the leaching of easily acid-soluble
components from
soils.
Some
the foliage,
from the trunks of
of these are redeposited in the
or the groundwater.
The increased
soil,
trees,
and from the upper layers of the
or else leached into the drainage basin
levels of K, Ca,
Mg,
Al, and
S0 4
appearing
streams in areas affected by acid rain are believed to be derived from the
soils.
It
in
is
possible that with time, the base components of such soils will be so depleted that nu-
Aluminum
trient deficiencies will occur.
sons, high
toxicity
aluminum concentrations appear
through effects on their root systems.
num
has a number of effects on other ions,
Effects
on crops.
greater than that of
many
field
(NATO,
in a
1980).
A
also be induced.
For two rea-
and
becoming short and brittle. Second, alumiamong which are interference with phospho-
aluminum phosphate.
While the
many crops appears to be much
damage by acid rain, no solid evbeen damaged by acid droplets in the
sensitivity of
tree species to direct foliar
idence exists that the leaves of crops have yet
even
may
be harmful to many higher plant species
First, cell division in the roots is inhibited,
the roots lose their flexibility and plasticity,
rus uptake and precipitation as
to
number of
begun
to suggest that
be detrimental.
In a study by
detailed studies, however, have
well-buffered agricultural system acid rain
Lee and Neely (1980) of 27 crop plants grown
in
may
pots and exposed to simulated acid
A
Acid Rain:
Sec. 5.3
133
Regional Issue
pH range from 2.5 to 5.7. visible, unsightly foliage lesions appeared in 21
pH of 3.0 (which occurs with a rainfall frequency of 0.5 to 1. 09c in affected
rain over a
crops
a
at
Studies of major Ontario crops by Hutchinson (1981)
regions of North America).
showed
that lettuce, beets, onions,
of
in rains
affected
pH
upon healthy foliage
the
respectively,
a
pH
et
al.,
Studies
at the
to plants
Brookhaven National Laboratory
in
1983) demonstrated that plants exposed to simulated
exposed
to
ambient
2.6, 6.5,
to losses of
many
and 11.4%,
Such seed losses
rainfall only.
in
millions of dollars per
United States.
in the
Experiments have shown
pollen
severely
all
and spinach depend
as tobacco, lettuce,
and 3.5 had decreased seed yields
4.2, 3.8.
compared
Such crops
major crop, such as soj beans, would amount
year
which
that the critical stage in the life cycle of plants at
transferred to the female flower and germinates to produce a long fertilization
is
(pollen) tube
is
len germination
very sensitive to low
pH
pine pollen was not.
For
at a
pH
of 3.5 and below.
was found
1983), birch pollen
fruit crops,
Generally, apple and grape pol-
(Sidhu. 1983).
and tube growth are reduced
boreal forest species (Cox.
at
soybeans, pinto beans, and tobacco were
3.0.
for their sale.
United States (Evans
acidic rainfalls of
and
2.5
In studies of
to be very sensitive while
which are obviously dependent on
a
good
fruit set
pollination time, acid rain poses a hazard that has not been evaluated.
summary,
In
it
seems clear
sition than are aquatic systems.
systems are
that terrestrial
Some
less sensitive to acid
of the short-term effects of acid rain
be beneficial, probably because of the fertilizing nitrogen inputs.
however,
ances
quite possible that
is
it
in the forest will
damaging
Over
depo-
may even
the longer term,
Nutrient cycling and bal-
effects will occur.
undoubtedly be affected, and tree growth may decline.
5.3.5 Effects of Acid Rain on Groundwater, Materials,
and Buildings
Groundwater and drinking water
quality.
Groundwater
accumulates
very slowly by the percolation of surface waters through the soil and bedrock to the water table.
If
groundwaters became acidified, those municipalities depending on ground-
water as
a
drinking
acceptable standards.
water
supply
However,
in
might
many
have
chemically
to
adjust
areas and especially
rural
wells are driven below the water table and the water
is
pumped
in
the
to the surface for direct
consumption, with no provision for treatment. Scientific evidence indicates
water acidification and
in
some
areas.
its
consequent contamination by acid-soluble metals
The major metals of concern
are lead, copper,
water to
cottage areas,
ground-
that
is
occurring
and zinc, which may be
leached from water pipes and containers, and aluminum coming from the bedrock
Studies by the Geological Survey of
1982) have shown that
den except
corded
ground
in
is
in the
pH
Sweden (Swedish Ministry of
values between 5 and 6 occur
southwestern parts, where
pH
in
groundwater
itself.
Agriculture,
all
over Swe-
values between 4 and 5 have been re-
shallow wells, with a lew such wells even being below 4.0.
The water
in the
quite susceptible to infiltration and replacement by acid waters percolating
from above.
The
risk that this
groundwater
and aluminum increases substantially as the
will
pH
become contaminated by heavy metals
of rain and percolated soil water
falls to
Human
134
4.0, leading to adverse health effects.
drawn from a well of
lakes are
their
The
fact that
over
own, and about half of these
common, emphasizes
the importance of the
Corrosion of water pipes.
Chapter 5
Environmental Disturbances
1
million
Swedes use water
where acidified
live in areas
problem
in
such areas.
Acidic water corrodes water pipes.
This leads,
of course, to more frequent pipe replacement, but more important, to the risk that metals
leached from the pipe walls can reach humans directly through water consumption.
Sweden copper
a whole.
houses
in
Old lead pipes
still
occur
Britain and Ireland.
widely used.
Canada and
pipes predominate, as they do in
in the older
eastern North
residences and are also
In
America as
common
in old
Galvanized pipes, with a high zinc content, are also
Copper solubility increases sharply below pH 5.0, and also with increasHot water pipes with acid water in them are the most susceptible to
Concentrations as high as 20 mg Cu/L have been reported in cold water,
ing temperature.
dissolution.
and 45 mg/L
in hot
1.5
rinsing in
(WHO) recommends
that
copper content be a
maximum
Cases have been reported from Sweden of people's hair turning green
mg/L.
warm
to levels of
The
water that has stood in the pipes overnight (Figure 5-11).
World Health Organization
of
after
water with high copper levels, and of children contracting diarrhea due
copper as low as 0.5 mg/L.
Cadmium and
lead can also be dissolved from
20
CD
E
10 -
Q.
Q.
O
o
°8o
5.0
6.0
^o^
Figure 5-11
7.0
in
PH
Copper content
Western Europe. Source:
in tap
water
Swedish
Ministry of Agriculture (1982).
Acid Rain:
Sec. 5.3
A
135
Regional Issue
soldered joints, and zinc from galvanized pipes.
similar problems have occurred.
copper, lead, and
In
some
aluminum have been found
in the
on buildings, materials, and
Effects
Adirondacks of
In the
New
York
State,
groundwater areas, high levels of
acidified
water systems of the houses.
paint.
Stone
buildings,
statues,
and monuments are eroded by a number of airborne pollutants, including acid
Building materials such as
stone, sandstone,
need
to
steel, paint, plastics,
and marble also
risk
cement, masonry, galvanized
steel,
The frequency with which
damage.
have new protective coatings replaced
rain.
lime-
structures
increasing with resulting additional
is
costs, estimated at billions of dollars annually.
The
effects of the various pollutants cannot yet be reliably separated
However,
other.
ing materials
is
it
is
from each
generally accepted that the major single corrosive agent of build-
sulfur dioxide and
its
by-products.
Sandstones and limestones have often been employed as materials for monuments
and sculptures.
country
Both corrode more rapidly
When
air.
in sulfur-laden city air
sulfur pollutants are deposited
than in sulfur free
on a sandstone or limestone surface,
they react with the calcium carbonate in the material, converting
uble calcium sulfate (gypsum), which washes off in the rain.
it
into the readily sol-
In the
Acid Rain Report
commissioned by the governor of Ohio in 1980 (Scientific Advisory Task Force, 1980),
the committee states that "acid rain is of special concern because of its effects on structures having archaeological or historical significance."
The
of famous statues and monuments such as the Acropolis
in
disfiguration and dissolution
Athens and famous
art treas-
ures in Italy has accelerated greatly over the past 30 years, often after they have stood
for centuries.
This
is
economic
a tragedy that defies
analysis.
5.3.6 Remedial and Control Measures
Since
it
is
apparent that very substantial harm
clear that remedial action
problem, with
effects
on
its
is
needed.
is
and microbes.
that the action will
we need
it
is
If
air, soil,
water, and sediments, and
its
large costs are likely to be associated with
to be sure that these costs are justified
and
be effective.
There can be no quick solutions.
In the past
being done to our environment,
have to be aware of the complexity of the
ramifications and interactions in
plants, animals,
certain types of remedial action,
today.
We
The cleanup may take decades, even
if
we
start
few years we have established the fundamental requirements for ac-
tion:
•
The recognition
•
The knowledge
that acid rain
is
that reduction of
a serious problem
emissions
is
the best solution
Sulfur oxides are produced from the burning of fuels, smelting of ores, and other
industrial processes.
Sulfur oxide emissions can be reduced by taking the following
measures before, during, and
after
combustion.
Human
136
Environmental Disturbances
Chapter 5
BEFORE COMBUSTION
Changing from
Fuel switching
fuels with higher sulfur content to those
with lower sulfur content
Blending fuels with higher and lower sulfur content
Fuel blending
produce a
fuel with a
Removing
Oil desulfurization
to
medium-level sulfur content
sulfur during the oil refining process by hydro-
genation (adding hydrogen)
Coal washing (physical clean-
Crushing and removing sulfur and other impurities from
ing of coal)
coal by placing the coal in liquid (the clean coal floats, the
impurities sink)
Chemical cleaning of coal
Dissolving the sulfur
in coal
with chemicals
DURING COMBUSTION
Fluidized bed combustion
Mixing
(FBC)
suspension
Limestone injection
stage burners
in
multi-
finely
ground limestone with coal and burning
Injecting finely
ground limestone
it
in
into a special burner
(LIMB)
AFTER COMBUSTION
Flue gas desulfurization
Mixing
(FGD), or scrubbing
with the flue gas to remove sulfur dioxide
a
chemical absorbent such as lime or limestone
Sulfur oxide emissions from nonferrous smelters can be reduced by a variety of
means, including
Removing some of
Mineral separation
the sulfur-bearing minerals
from the
metal-bearing minerals before smelting
Using smelting processes producing
Process change
less
SO> or producing
waste streams that are more easily controlled
S02
Capturing
By-product production
after the smelting process, to
furic acid (used in
many
ing fertilizer), liquid
industrial processes
SOi (used
in
produce
and
in
sul-
mak-
pulp and paper
processing), or elemental sulfur (used in industrial processes)
The Organization
for
Economic Co-operation and Development (OECD), which
includes most of the Western industrialized nations, has carried out extensive research
into the
looked
consequences of long-distance transport of acid rain (OECD, 1981
in detail at the control technologies
mentation.
The research
quences will be severe
The OECD's
if
and the costs associated with
has also
is
done.
calculations apply to the northwestern and southern parts of Europe
dollar.
USSR),
put at
$780 per ton
Commonwealth
cf Independ-
The average cleaning
of sulfur. Applied to the whole of Europe exclusive of the
lion per year.
It
their imple-
leaves no doubt that the political and socioeconomic conse-
nothing
and are based on the 1980 U.S.
ent States (former
).
the cost of a
50%
reduction in
cost
is
S0 2 would
be about $8
bil-
137
Lessons Learned
Sec. 5.4
The General Accounting Office of
SO :
report on acid rain that an
would cost $3
eastern United States
1980 SGs emissions
the U.S.
the
in
(Total
United States were 24.1 million tons.) Clearly, the United
in the
technology and a certainty of success
Over
1982
in its
1980 dollars (GAO, 1981).
to $4.5 billion
program
States will not risk implementing such a costly
priate
government has suggested
emissions reduction of 10 million tons per year
until
it
is
sure that
it
has appro-
mitigating the effects of acid rain.
in
the next few years, decisions will have to be
made on
these technologies.
Meanwhile, tensions between the United States and Canada and between the Scandinavians and
some of
their
are further degraded
European neighbors are
environments
likely to increase as their
and tourism, recreation, and perhaps soon agriculture and forestry
are affected.
5.4
LESSONS LEARNED
Although the two issues of human environmental disturbances examined
and 5.3 are very
different, they
Among
pervasive environmental problems.
Human
Sections 5.2
in
can teach us important lessons about controlling these
these lessons are the following.
technology can be the cause of serious economic impacts over very large
areas of the world, including areas hundreds or thousands of kilometers from the emitters
of the pollution.
gases and particles.
This
is
so because the atmosphere
CO
Poorly soluble gases such as
:
is
a most effective carrier of
and various synthetics
like the
halocarbons are spread worldwide and become long-lasting or permanent parts of the
More
mosphere.
soluble gases such as
nents and cause serious
and
to buildings
It
damage
NO
SOt and
v
to ecological systems, tourism, agriculture,
to cooperate.
much of
forestry,
governments
the
from the emitters,
states
and provinces
Since high costs are involved, and since
the eastern half of the continent.
the victims are far distant
if
North America, any attempts to solve the acid rain
In
problem involve the U.S. and Canadian governments as well as the
in
and
and materials.
follows from this that corrective action can be taken only
concerned agree
at-
can affect large parts of conti-
will be very difficult for the
it
governments
to act jointly.
Nevertheless, public pressure
ture technology will
have to be
tinual search for sources of
escape to the atmosphere.
tion
growing for remedial action. This implies
that fu-
cleaner than before and that there will be a con-
energy and raw material
that create less
waste which can
Control of such problems has two main components: regula-
and technical control.
Regulation by government
ter pollution
the
is
much
on the
local scale.
pathway followed by the
dose-response basis
is
a long-established
On
this scale
it
is
measure
pollutant, to identify real effects,
to the concentrations of the pollutants.
to design suitable regulations for
in
the case of air and
wa-
easy to identify the polluters, to trace
and
It
is
to relate these
on the
correspondingly easy
emission or ambient standards and to monitor their
usefulness.
It
is
much more
difficult
to
proceed
in
this
manner
in
the case of regional or
Human
138
Environmental Disturbances
worldwide problems such as those of acid rain and
C0
can plead, often successfully, that the costs outweigh the benefits, that the
dial action
true culprits
cannot be identified, or that there
no hard,
is
Sections 5.2 and 5.3, there
in
tainty
is
not likely to be
removed
much
is
proof that the ad-
scientific
may even
verse effects are truly the result of the pollution; and there
saw
Opponents of reme-
buildup.
2
Chapter 5
be benefits. As
we
uncertainty in both cases, and this uncer-
quickly.
Technical control measures are the special province of the scientist and engineer.
The
best of these measures
methods
the choice of pollution-free
is
power generation and metal
dustry (e.g., in
For example, nuclear generating stations are a
problems.
in the originating in-
But even
smelting).
much
this
may
However, the public
ducing energy than are coal-fired generating stations.
cause
still
way of
"cleaner"
pro-
alarmed
is
at
the possible danger of accidents in the reactors and at the potential difficulties of future
Hence although
waste disposal.
reduces
it
S0 2 NO
,
v
may
tion of nuclear reactors for coal or oil furnaces
,
and
C0 2
emissions, the substitu-
not be acceptable as a permanent
some people. Nevertheless, the scientist and engineer must constantly seek
more efficient methods to remove the problems at their sources.
Removal of such pollutants as S0 2 NO v and C0 2 from flue gases is technically
feasible, but very expensive. The technical means to achieve this are presented in Chapsolution to
cleaner and
,
ter
13.
In the case of
C0 2
the removal of carbon
,
net heat conversion so greatly that the cost
sors are
A
more
,
would reduce
would be
the efficiency of the
The
prohibitive.
acid rain precur-
easily dealt with, but even here the cost of removal will be high.
political value
judgment has
to be
made on such
questions: the representatives
of the public must decide whether environmental protection justifies the cost. The prob-
move toward higher
ability is that they will gradually
specialists in pollution control
5.5
levels of protection;
hence the
must be ready with the technical solutions.
EPILOGUE
Finally,
it
should be emphasized that only two
been discussed
that
Of
in this chapter.
the
many
human environmental
disturbances have
other disturbances to our global ecosystem
could have been considered, the clear-cutting of tropical rain forests
most destructive.
In 3 acres of a
Malaysian rain
forest, there are
(with their interdependent plant, animal, and microbial
life)
is
one of the
more species of
than in
all
trees
of the United
States.
About half
United States
to
the trees harvested
91%
in India).
and other paper products.
priceless resource.
The
used
fuel (from
22%
However, from an environmental standpoint,
by a car traveling 18,000
km
soil,
trees are a
family of four breathing for a year.
[Life, 13(6).
May
lb)
of
1
m
3
,
the
1990]
Harvesting only the annual growth rate of a forest
than clear cutting) should be standard practice.
C0 2
amount emitand produce enough oxygen to keep a
absorb 12 kg (26
(11,000 mi),
in the
in construction, furniture, newsprint,
For example one fully grown deciduous tree can; withdraw
(265 gal) of water per day from the
ted
worldwide are used for
rest are
(i.e.,
sustainable logging rather
Clear cutting destroys the ecosystem of
Chapter 5
139
Problems
some
a forest and causes soil erosion (in
cases, desert)
from which the land can never
recover.
There are other innumerable human environmental disturbances
Can you
every day.
some of them? Do you consider
think of
that confront us
these problems as chal-
lenges that society will resolve, or are they signs of the eventual demise of the
race?
Our
important
collective response could be a self-fulfilling prophecy.
Technology
human
will be
correcting environmental problems and achieving global sustainable devel-
in
opment (defined in Section 1.6.1). However long-term sustainability will be even more
dependent on cooperation among governments, industries and society, in implementing
sound environmental policies. Guidelines for proper environmental management are
covered in Chapter 16 along with an explanation as to why sustainability must be an evolutionary process that adapts to changes in economic and social conditions (Section
16.2).
PROBLEMS
5.1.
List the gases
Ozone
5.2.
and possible sources of these gases
that contribute to (a)
Global warming; (b)
depletion.
Global warming seems to be progressing inexorably.
ing from (a) natural causes and (b)
human
activities
What environmental
would tend
conditions aris-
to offset this
warming
trend'.'
5.3.
Why
5.4.
In this chapter
the
is
ozone layer decreasing, and what are the possible consequences?
examples of global (CCM, regional/continental (acid
rain),
bances have been presented.
From your
natural or manufactured,
other examples that in your opinion are
list
current
and
local distur-
knowledge of environmental disturbances,
(a)
global; (b) re-
gional/continental; (c) local in scale.
5.5.
Problem
Select one of the examples listed in
5.4,
and prepare a short (two- or three-page)
statement of your understanding of that particular environmental problem.
5.6.
Several types of evidence have suggested that increased acidity of lake and river waters
responsible for a decline
5.7.
If
S02
Trees require adequate sulfur (S) and nitrogen (N) for healthy growth.
Wh>
is
Explain.
this
such regions as California. Michigan, and Ontario? (See Table 5-1.)
in
acid rain be a problem for
5.9.
populations.
emissions are controlled by an appropriate technology, what will be the effect of
on rain
5.8.
in their tish
are the gases
S02
Why,
then, should
them?
and NO, believed responsible
that long-distance transport of pollutant air
masses
is
for regional acidification?
Why
is
it
believed responsible for the regional
acid rain problem?
5.10.
Old and aging
5.11.
Why
5.12.
last
is
up
it
fish
populations
difficult to
to
five
in
a lake
may
indicate the presence of acid rain.
Why?
use annual ring increments as an indication of acid rain damage'.'
global or regional
greenhouse effect and acid
rain.
lutionis) to this disturbance.
human environmental
disturbances
in
addition to the
Select one of these and discuss the causes and possible so-
Human
140
Environmental Disturbances
Chapter 5
REFERENCES
On Carbon
Houghton,
Dioxide Buildup
Jenkins, G.
J. T.,
Houghton,
J.
and Ephraums,
(eds) Climate Change, 1990:
J. J.
IPCC
The
Sci-
Assessment. Cambridge: Cambridge University Press, 1990.
entific
J. T.,
Callander, B. A. and Varney,
mentary Report
to the
IPCC
S.
K. (eds) Climate Change, 1992: The Supple-
Scientific Assessment.
Cambridge: Cambridge University Press,
1992.
U.S.
Department of Energy. A Comprehensive Plan for Carbon Dioxide Effects Research and
Assessment. Part 1, The Global Carbon Cycle and Climatic Effects of Increasing Carbon
Dioxide, Carbon Dioxide Effects Research and Assessment Program. Report 008. Washington, D.C: U.S. Department of Energy, 1980a.
U.S.
Department of Energy, Environmental Control Technology for Atmospheric Carbon Dioxide, Carbon Dioxide Effects Research and Assessment Program. Report 006. Washington,
D.C: U.S. Department of Energy, 1980b.
Wigley,
T.
M.
L.,
and Raper.
S. C. B.
"Implications for Climate and Sea Level of Revised
IPCC
Emission Scenarios." Nature 357 (1992): 293.
World Meteorological
Role of
Organization. World Climate Programme: On the Assessment of the
on Climate Variations and Their Impact. Villach, Austria and Geneva, Switzer-
World Meteorological Organization, 1980 and 1981.
land:
On
C0 2
Acid Rain
Baker,
J.
and Schofield, C. L. "Aluminum Toxicity
P.,
and Adirondack Surface Water Quality."
to Fish as Related to
In Ecological
Acid Precipitation
Impact of Acid Precipitation, D.
Drablos and A. Tollan (eds), Sandetjord, Norway: SNSF, Oslo, 1980, pp. 292-296.
Beamish, R.
J.,
and Harvey, H. H. "Acidification of the La Cloche Mountain Lakes, Ontario, and
Resulting Fish Mortalities." Journal of Fisheries Research Board of
Canada 29
(1972):
1131-1143.
Beamish, R.
J.,
Lockhart, W.
L.,
Vanhoon,
J.
C, and Harvey, H. H. "Long-Term
Ambio 4 (1975): 98-102.
Acidification
of a Lake and Resulting Effects on Fishes."
Cox, R. M.
New
"Sensitivity of Forest Plant Reproduction to
Long Range Transported Air
Dickson, W. "Properties of Acidified Waters."
Drablos and A. Tollan
(eds.).
In Ecological
D., and Tollan, A. Ecological Impact of Acid
SNSF, Oslo, 1980.
Environment Canada. The Acid Rain
Story. Ottawa:
Environment Canada. Downwind: The Acid Rain
L. S.,
Lewin, K. F, Petti, M.
Soybeans Exposed
to
GAO. General Accounting
ing Office, 1981.
Impact of Acid Precipitation, D.
Sandefjord, Norway: SNSF. Oslo, 1980, pp. 75-83.
Drablos,
Evans,
Pollutants."
Phytologist 95 (1983): 269-276.
J.,
Norway:
Environment Canada, 1984.
Story.
Ottawa: Environment Canada, 1981.
and Cunningham, E. A. "Productivity of Field-Grown
Simulated Acidic Rain."
Office Report
Precipitation. Sandefjord,
New
Phytologist 93 (1983): 377-388.
on Acid Rain. Washington, D.C: U.S. Government
Print-
Chapter 5
141
References
Harvey, H. H. "Widespread and Diverse Changes
and A. Tollan
Harvey, H.
H.,
(eds.).
Biota of North American Lakes and Riv-
in the
ers Coincident with Acidification." In Ecological
Impact of Acid Precipitation, D. Drablos
Sandefjord, Norway: SNSF, Oslo, 1980, pp. 93-98.
and Pierce, R. C.
Canadian Aquatic Environment. Ot-
(eds.). Acidification in the
tawa: National Research Council of Canada, 1981.
Hutchinson,
T.
C
"Report to the Ontario Ministry of Environment on the Relative Sensitivity of
Ontario Crops to Acid Rain Spray." Unpublished 1981.
Klein, R. M., and Perkins,
T.
D. "Cascades of Causes and Effects of Forest Decline."
Ambio 16
(1987): 86-93.
Lee,
J. J.,
and Neely, G. E. Sulfuric Acid Rain Effects on Crop Yield and Foliar
Injury. Corvallis,
Oreg.: U.S. Environmental Protection Agency, 1980.
NATO.
Effects
OECD. "The
of Acid Precipitation on Terrestrial Ecosystems.
Costs and Benefits of Sulfur Oxide Control:
ization for
A
New
York: Plenum Press, 1980.
Methodological Study." Paris: Organ-
Economic Co-operation and Development, 1981.
Ontario Ministry of Environment. The Case Against Acid Rain. Toronto: Ontario Ministry of
the Environment. 1980.
Ryan,
P. M., and Harvey H. H. "Growth Responses of Yellow Perch to Lake
La Cloche Mountain Lakes of Ontario." Environmental Biology of Fish
Scientific
Advisory Task Force. Acid Rain: Report
to the
Acidification in the
5 (1980): 97-108.
Governor of Ohio. Columbus. Ohio:
State of Ohio, 1980.
Sidhu,
S. S. "Effects of Simulated Acid Rain on Pollen Germinations and Pollen Tube Growth of
White Spruce (Picea Gtauca)." Canadian Journal of Botany 61 (1983): 3095-3099.
Swedish Ministry of Agriculture, Acidification Today and Tomorrow. Stockholm: Swedish
Ministry of Agriculture, 1982.
PART
2
Scientific
Background
CHAPTER
6
Physics and Chemistry
Gary W. Heinke
J. Glynn Henry
6.1
INTRODUCTION
Much
of this book deals with water, with
or sludges.
When we
rain, rivers, lakes,
air,
say water, normally
groundwater, or seawater.
and with mixtures of solids such as refuse
we mean
In
not
H2
but water in the form of
each of these cases
we
are dealing with
very dilute systems that have particles dispersed and solutes dissolved in water, the universal solvent.
When we
say air
we
generally
mean
not just the pure mixture of nitro-
gen, oxygen, and trace gases, but also the gaseous pollutants, as well as the liquid and
solid particles
suspended
in the air.
In this chapter
we
therefore
summarize some fun-
damentals concerning particles and particle dispersions, and then present some basic
in-
formation from physics, chemistry, physical chemistry, and reaction kinetics that are
relevant to water and air systems.
courses in the various disciplines, and
6.2
Some
some
of this material
will be
new
is
covered
in
elementary
here.
PARTICLE DISPERSION
To be able to describe and treat natural waters, wastewaters, air,
sludges, knowledge of the medium and the particles and solutes in it
142
solid wastes,
is
essential.
and
Some
properties of the
medium may be
polluted wastewaters,
greatly affected or only slightly affected by the pres-
For example, the density of various waters, including heav-
ence of particles or solutes.
ily
143
Particle Dispersion
Sec. 6.2
so close to that of water that the small differences can
is
Even seawater, with a total dissolved solids concentration of about
34,500 mg/L, has a density only 2.5% greater than that of pure water. Other properties
usually be ignored.
medium may be
of the
iar
greatly affected by the presence of particles or solutes.
example would be the
loss of visibility in air
when
A
famil-
fine liquid particles are present
(fog) or fine solid particles are present (smoke).
6.2.1 Particle Size, Shape, and Distribution
A
particle can be defined as
any distinct
(i.e.,
particulate) portion of solid, liquid, or
gaseous matter larger than a single small molecule [larger than
Water,
ameter].
air,
and solid wastes contain many particles
For many situations
size.
1
nanometer (nm)
will be important to find a convenient
it
and
size of particles, their shape,
in di-
that vary considerably in
way
to express the
their size distribution.
Figure 6-1 presents a schematic diagram on a logarithmic scale to cover the range
of sizes of particles of importance
in
environmental engineering. The boundaries shown
when they can be removed
The lower limit for this is about 0.4 (am.
They normally range in size from be-
are flexible.
In water, particles are said to be in suspension
by
by
settling or
through
filtration
filter
paper.
Particles smaller than that are called colloids.
tween
1
to
Because of
400 nm, so they
their
are not visible with an ordinary high-powered microscope.
importance
in
environmental engineering, colloids are discussed sepa-
Below about
rately in section 6.2.2.
1
nm,
particles are considered to be dissolved, with
diameters ranging from those of a single atom (about 0.2 nm) to the size of a molecule
(about
1
ical in
They
nm).
Seldom
are dispersed in the solvert to
will the particles in a
shape.
To describe
for solid wastes,
where
length, width,
ticle
more
easily characterized.
and height of the particle
is
settling
its
example, the sphericity 4/
,
is
especially
Small particles
in air
Irregular shape as defined by the
may compare the parOne such
velocity to that of an equivalent sphere.
presented
in
Section 6.2.4
in
equation (6.8).
size distribution of spherical or equivalent spherical particles generally cannot
Instead, classification
measured.
is difficult,
normally related mathematically to an equiv-
be expressed by a single parameter or function,
eter.
and shape.
Other methods are based on shape factors, which
surface area or
The
the mixtures of particles analytically
particles differ greatly in size
or liquid suspensions are
alent diameter.
form a solution.
mixture or suspension be of uniform size or spher-
may depend on
as, for
example, average particle diam-
way
particle diameters are actually
the
Methods range from the viewing of material
counting through a microscope for small sizes.
In
for coarse sizes to particle
any case, particles are classified into
an arbitrary number of size ranges which may, for example, be sieve sizes.
mation can be plotted as shown
than a given diameter d
/(
in
Figure 6-2, which
versus particle diameter.
is
This infor-
a plot of cumulative weight less
Mathematical expressions are also
used to describe particle size distribution, but these are beyond the scope of
this
book.
144
Physics and Chemistry
Chapter 6
0.4-0.8 u.m
Lower
Lower
Limit
of Visibility
to
Eye
Limit of
Lower
Limit
Microscope
of Electron
Visibility
Microscope
i
I
t
Rain
Mist, Fog,
Smog
Clouds
Tobacco
Coal Dust
l
Smoke
i
Atmospheric Dust
1
i
1
Foundry Dust
1
Agriculture
Boulders
Gravel
Course
Fine
Sand
Sand
Solid
Viruses
Bacteria
Suspended
wastes
Clays
Silt
Pollen
Compacted
Smoke
Oil
Sprays
1
Molecular
Colloidal
Settleable
1
i
i
Water and Wastewater
Air
1
i
i
1,000,000100,00010,000 1000
(1
m)
(1
100
10"2
10"
10
mm)
microns
Typical range of particle size.
"\i"
(=
micrometers
Source:
Common
Units:
Adapted from several sources,
microns (1x 10~ 6 m), and
u,
mu,
millimicrons
common
were
SI Units:
p
is
mp
(Both systems are
still
in
use,
(1
x I0~ 9 m)
terms before SI was adopted.
replaced by urn, micrometers
is
(1
replaced by nm, nanometers
and both are used
in this
nm)
"|im")
including Williamson (1973), Hidy and Brock (1970), and Perkins (1974).
Note:
10" 3
(1
Particle diameter in
Figure 6-1
1
i
(1
book.)
x 10~ 6 )
x lO
9
)
10"
145
Particle Dispersion
Sec. 6.2
Figure 6-2
Particle size distribution.
6.2.2 Colloidal Dispersions
Colloidal dispersions consist of very small particles ranging in size from about
nm, separated by
the dispersion
Although dispersions
liquid, or gaseous.
dium of
medium. The dispersed
interest in the
in a solid
environmental fields
is
1
to
400
colloidal particles can be solid,
medium
occur, the dispersion
either a liquid or a gas.
me-
Common names
for dispersions are given in the following table:
Liquid
Liquid
Liquid
Emulsion
Gas
Liquid
Foam
Solid
Gas
Gas
Smoke, aerosol
The
how
Fog, aerosol
characteristic properties of colloidal particles can be attributed to their small
which provides
a very large surface area per unit
large a surface area they possess, consider a
a surface area of
total
Suspension
Solid
Liquid
size,
COMMON NAME
DISPERSION MEDIUM
DISPERSED PHASE
6
cm 2
surface area to 12
If
.
cm 2
we
,
divide
but the
it
into eight
volume.
cm to
cubes
cm
cube
volume remains
1
j
the same.
To demonstrate just
Such a cube has
a side.
to a side,
By
we double the
make
continuing to
smaller and smaller cubes until they are well into the colloidal size range, or about 10~ 5
mm
to a side, the total
increased from 6
cm
2
volume
to
600
be the same but the
will
still
m2
a millionfold increase.
,
total surface
Because of
area will have
this
high sur-
146
Physics and Chemistry
face/volume
ratio, colloids
have tremendous adsorptive capacity relative to their small
mass. Also, with the large surface area the
come
weak atomic
surface charges on colloids be-
a significant factor in their behavior.
The two
ity
Chapter 6
surface-related properties of colloids are therefore their adsorptive capac-
Adsorption
and electrokinetic charge.
on
centrate
charge
refers to the ability of certain solids to con-
substances from the surrounding medium.
their surface,
may be
that all colloidal particles carry
positive or negative
nitude depending on the type of material the colloid
is
made
The
electrical
and varies
repel each other and thereby prevent the formation of larger particles through
This repulsion' between particles makes
eration.
their dispersion
by adding
is
medium.
remove
mag-
agglom-
difficult to separate the particles
from
Coagulation, a treatment process that overcomes the problem
particles (ions) of opposite charge,
also used to
it
in
Like-charged particles
of.
from polluted
particles
is
discussed in Chapter
air
(Chapter
11.
Coagulation
13).
6.2.3 Methods of Expressing Particle Concentrations
The mass of
particles in a unit
tions in
volume
(or
mass) of dispersion medium
There are several different ways of expressing
cle concentration.
is
called parti-
particle concentra-
water, and wastewater.
air,
The usual units for expressing the concentration of small particles susgrams of particulates per cubic meter of air. The concentration is determined by drawing a known volume of air through a preweighed filter and weighing
the amount of particulates that have been trapped. For dust, which consists of larger
particles that settle quickly, measurements are made by collecting the settleable material
in dustfall jars for a specific time and determining the accumulated weight.
The conAir.
pended
in air are
centration
is
then expressed in weight collected per unit area over a given period.
Ex-
amples of such units are ton/mile 2 x month, or kg/m 2 x month. Several other methods
of expressing the concentration of particles in
Water and wastewater.
Concentrations of particles
expressed differently than in wastewater.
ticles in
most natural waters, particularly
rather than a gravimetric method.
that causes light to
algae, silica, rust, bacteria,
named
(APHA
is
et al.,
is
and other
is
particulates.
is
used
an expression of the optical property
in straight lines
caused by suspended matter such as
is
the water industry
after the instrument
It
water are normally
an optical method
in drinking water,
Turbidity
Turbidity in water
measurement adopted by
cloud).
in
Because there are only small amounts of par-
be scattered and absorbed rather than transmitted
through the sample.
mud,
use (see Chapter 13).
air are also in
The
clay,
standard unit of turbidity
the nephelometric turbidity unit
(NTU)
used to measure turbidity, the nephelometer (Gk: nephos,
based on a specified concentration of a formazin polymer suspension
1985).
For wastewaters and sludges, the suspended solids (SS) concentrations are generally sufficiently
mg/L.
A
high that gravimetric methods are best, and the units normally used are
small sample (100
mL)
of wastewater or sludge
is
filtered
through a glass-
Sec. 6.2
147
Particle Dispersion
is dried and weighed before and after filtration in order to determine the
SS concentration. An alternative, gravimetric procedure, useful when filtration is difficult, is to weigh a known volume of sample before and after evaporation of the liquid
Solids concen(at 103 C). with the residue representing the SS (APHA et al.. 1985).
fiber filter that
may
exceed 10,000 mg/L
trations that
be expressed
in
percent
c
(\ /c
=
10,000 mg/L).
6.2.4 Settling of a Particle in a Fluid
The
principles involved in the settling of a particle in a fluid can be applied to the re-
moval of suspended
ter treatment
particulates
solids in a river or lake (Chapter 9), the design of clarifiers for
(Chapter
from
air
1
1
)
(Chapter
13).
Consider the situation of a single sand particle
fluid.
A
particle falling
wa-
or wastewater treatment (Chapter 12), and the settling of
settling at velocity u in a quiescent
under the action of gravity will accelerate
until the frictional
drag of the fluid just balances the gravitational acceleration, after which
to fall at a constant velocity
known
it
will continue
as the terminal settling velocity u, (Rich,
1980).
This velocity can be calculated by making a force balance on the particle (see Figure
6-3):
FK
where
FE =
(6.1.
/',,
external force on particle, in this case gravity (but could be another
external force such as centrifugal force in centrifugation)
FB =
FD =
FR —
buoyancy force
friction or drag force,
resultant force
(=
opposing
when
settling
of particle
terminal velocity
is
reached)
Figure 6-3
Forces acting on a particle
settling in a quiescent fluid.
148
Physics and Chemistry
Chapter 6
These forces can be expressed as
FE
Ma E = Mg
==
FB =
where
Ma E =
M
=
mass of
u
=
=
settling velocity of particle
aE
rco
2
,
£-
Mg
particle
acceleration, equal to
=
where
co
=
p
=
density of fluid
pp
=
density of particle
Substituting the values of
we
P_
£-
g for gravitational
settling (for centrifugation,
aE
angular velocity)
FR FE FB
,
,
,
and
FD
and rearranging,
into equation (6.1)
get
Tr-^*-M
Experimentally,
it
has been found that
Fn =
where
CD
is
,62)
C D A p pu 2
the coefficient of drag or friction (dimensionless) and
area of particle at right angles to direction of settling.
equation (6.2),
we
get
du
—
= Pp-P
-di
Assuming
M
is
the projected
pu 2
(63)
2M~
du
*
nd p /4
3
(Kdl /6)p p
2p p d p
(6.4)
Therefore, substituting this value of
the particle diameter.
tion (6.3) yields
The terminal
8
is
that the particle is spherical yields
AP
where dp
CD A
Ap
Substituting these values into
=
settling velocity u, is
—
PP
-P
s-
3C D pw 2
±
dt
=0
into equa-
<6 5)
-
^pt;
reached very quickly.
d
A p IM
At
that point,
Sec. 6.2
149
Particle Dispersion
so solving for
»,,
we
get
3C
Equation (6.6) applies to settling particles
such as
It
nolds
oil
-
4g(p p
=
14,
p)d p
(6.6)
p
> p)
(p,,
as well as rising particles (p
p
< p)
or air in water.
has been found experimentally that
CD
is
a function of the dimensionless Rey-
number Re:
Cd ~
Re"
where the values of b and n are as given
Flow
following table:
in the
Remarks
Re
Laminar
<2
Intermediate
2-500
24
Friction drag predominates
1
0.6
18.5
Friction and
form drag both
important
500-200.000
Turbulent
'Reynolds number. Re,
is
defined as
Re
where
(i
is
the
Form drag predominates
0.44
"d,,P
=
dynamic (absolute) viscosity of
medium.
the
For laminar flow conditions,
Cn =
By
substituting into equation (6.6),
we
u,
24
24fi
_
pud r
Re
obtain
=
(6.7)
18m
Equation (6.7)
occurs and
is
the Stokes terminal velocity equation.
if the particles
It
applies only
if
laminar flow
are spherical.
Both the suspended matter
in natural
waters and wastewaters and particulate emis-
They have a greater surface area per unit voltherefore settle more slowly than spheres of equivalent
sions settling in air are seldom spherical.
ume
than a sphere and will
volume.
For particles of irregular shape, an index called sphericity has been defined,
such that
1.5
Vd P
(6.8)
150
Physics and Chemistry
where the sphericity
Note
sionless.
ways be
4>
41
is
a relative index of the roundness of the particle
that for a sphere *F
less than
= 0.66,
= 0.95.
4^
1.
The
1
is
water or
in
0.28, for jagged
is
more
settling tanks for
air
water or wastewater (Chapters
(Chapter
13).
6.1
0.001
mm
2.65.
Assume laminar
2
sand
Therefore, experimental or empirical methods
not quiescent.
Calculate the settling velocity of two spherical particles of diameter
is
flint
normally discrete particles and the
air are not
and 12) or treatment units for cleaning polluted
Example
dimen-
is
and for nearly spherical Ottawa sand
0.73,
must normally be used for the design of
1
=
and
particles *F will al-
practical application of the Stokes terminal velocity equation
medium
air
=
4*
coal
complicated, since particles
water or
whereas for nonspherical
1,
For example, for mica flakes 4*
pulverized
for
=
Chapter 6
h.
in still
water
temperature of 20 C.
at a
flow conditions.
The
A common
(a) 0.1
mm
and (b)
specific gravity of the particles
is
detention time for sedimentation tanks
Will these particles settle to the bottom of a 3.5-m-deep tank in that time?
From Appendix
Solution
B.2,
P2()oC. water
=
" 8 kg/m3
p,,
=
2.65 x 998 kg/m 3
M-200C. water
=
1
00 x 10
we
Therefore, using equation (6.7),
(a)
u,
=
=
So
(2.65
-
3
N
•
s/m 2
m/s
the time to settle 3.5
=
u,
So
the time to settle 3.5
This settling rate
is
3
1.00 x 10
kg/m
s
obtain
18 x 1.00 x 10" 3
kg/m
•
s
= 9.0mm/s
m=
x 10~ 3
3.5/9.0
tling rate is certainly practical for particle
(b)
=
998 kg/m 3 x 9.81 m/s 2 x
1.00)
9.0 x 10-
3
=
9.0 x 10" 7 m/s
m=
much
coagulation/flocculation must be
390 x 10
4
s
=
390
s
=
6.5
min
«
2h.
This
set-
removal by sedimentation.
9.0 x 10" 4
=
1083
mm/s
h.
too slow for particle removal by sedimentation alone, so
employed
to increase the particle size
and thus achieve
dissolve in water to form true solutions.
The substance
greater settling velocity (see Chapter 11).
6.3
SOLUTIONS
6.3.1 Solutions and Solubility
Gases, liquids, and solids
that dissolves
is
is
may
called the solute, and the substance or
called the solvent.
A
solution
may have any
medium
in
which
it
is
dissolved
concentration of the solute below a cer-
Sec. 6.3
151
Solutions
of that substance
tain limit, called the solubility
tains,
at
a given temperature, as
dissolving substance
is
much
can hold
it
called a saturated solution.
are called unsaturated, and those
that
A
medium.
in that
solute as
solution that con-
the presence of the
in
Solutions that contain less solute
(under special conditions) contain more are
called supersaturated.
Temperature and the chemical character of the
Several factors affect solubility.
substances involved are the most important.
Pressure
relatively unimportant for liq-
is
The
deep underground supplies or deep ocean water.
uids, except for
solubilities of
most substances increase as temperature increases, but there are important exceptions.
In general, if a substance dissolves at saturation with absorption of heat, the solubility
will increase as the temperature
On
goes up.
the other hand,
if
heat evolves in the so-
lution process, solubility will decrease with an increase in temperature of the solvent.
number of
the calcium
in solubility as the
CaC0 3 CaS0 4
compounds, including
,
The
temperature goes up.
solubility of
oxygen
creased capacity of natural waters to supply oxygen for aquatic
water also de-
and for oxidation of
life
summer months.
The chemical character of
forms
in
A
decrease
,
This has important consequences, because of the de-
crease with rising temperature.
organic pollution during the
and Ca(OH) 2
,
may be such
the solute and solvent
that a solution
For example, alcohol (C 2 H ? OH) and water (H 2 0) mix easily, with no
readily.
That
saturation limit.
On
they are completely miscible.
is.
mercury are almost completely immiscible.
There
is
the other hand, water and
a wide range of miscibility be-
Handbooks provide information on the solubilities of substances
The solubilities of many substances are af-
tween these extremes.
(solubility constants) in various solvents.
fected by chemical reactions with water or other solvents.
bonate
if
is
only slightly soluble
in
pure water, but has a
the water contains carbon dioxide
CaCO} and C0 2
ter to
.
(C0 2 ), because
much
ions.
In
higher apparent solubility
of the chemical reaction between
In general, substances such as salts, acids,
form solutions containing
For example, calcium car-
and bases dissolve
in
wa-
such solutions the presence of excess amounts
of any of the ions can greatly affect solubility.
In precipitation reactions, a
ity
product.
For example,
CaC0
[CO^ 2 = A" sp
where
.
Ksp
is
form of the equilibrium constant
,
the solubility product
called the solubil-
is
the reaction of calcium carbonate
Ca +2 + CO^ 2
(solid) ^=
3
]
in
(CaCO^)
is
in
water,
defined as [Ca +2 ]
the solubility product constant, an [] indicates the concentration
Numerical values of
of the substance in mol/L.
Ksp
for precipitation reactions
can be
obtained from handbooks.
The
solubility of gases in liquids
depends on the nature of the gas, on the nature
of the solvent, and on pressure and temperature.
For example, nitrogen (N 2
),
hydrogen
(H 2 ), and oxygen (0 2 are relatively insoluble in water, whereas ammonia (NH 3 and
hydrogen sulfide (H 2 S) are quite soluble. A discussion of the gas laws, including those
)
)
of importance to gas-liquid transfer,
is
presented
in
Section 6.4.
Natural waters always contain dissolved ions, which
come from
the contact of
with minerals such as limestone, magnesite, gypsum, and salt beds.
mon cations found in natural water are calcium (Ca +2 magnesium
ter
),
(Na + ), and potassium (K
f
).
The most common anions
wa-
The most com-
(Mg
1
-1
are the bicarbonates
).
sodium
(HCO^),
152
Physics and Chemistry
chlorides (CI"), sulfates
electroneutrality
ter,
sum
is
(SO^-
and to a lesser extent, the
),
maintained, so that the
sum of
nitrates
(NO^
).
Chapter 6
In any
wa-
must always equal the
the cations
Water containing ions that interfere with the action of soap is called
"Hardness" is due mainly to Ca +2 and Mg +2 ions which react with
form precipitates and with various anions to form scale in boilers and hot water
of the anions.
"hard" water.
soup
to
piping.
measure of the
Alkalinity, a
is
ability (buffering capacity)
largely attributable to bicarbonates, hydroxides
found
ionic species
in
water include, for example, the following:
ANIONS
CATIONS
Iron (Fe+ 2 or
Manganese
Fe+ 3 )
(Mn +2
Aluminum (A1+
Human
(CO^ 2
Carbonate
)
Hydroxide (OH~)
)
Sulfur (S~ 2
3
)
Ammonium (NH 4+
Copper (Cu+
of water to neutralize acid
and carbonates (see page 163). Minor
Phosphates
)
,
SOj 2
)
(PO^ 3 HPOj 2 H 2 POj 2
,
,
)
2
)
activity, principally
through industrial waste discharges,
may add
which may be toxic
to
ions to natural
The heavy metal
waters, sometimes resulting in widespread pollution problems.
ions,
microorganisms, plants, and animals, are prime examples.
6.3.2 Methods of Expressing the Composition
of Solutions
The following two systems
for expressing the composition of solutions are
commonly
used:
1.
Mass/mass (commonly stated as weight/weight), or more explicitly, the mass of
solute per mass of solution. A typical unit used is mg/kg, also expressed as ppm*
(parts per million). This method is not temperature dependent.
2.
Mass/volume (commonly stated as weight/volume), or more explicitly, the mass
of solute per volume of solution. A typical unit used is mg/L.* This method is
temperature dependent, since volume varies with temperature. Therefore, temperature should be reported
The
solution
unity,
is
units
unity,
ppm and mg/L
which
is
when
stating concentration
are often used interchangeably. This
is
by
this
method.
justified if the specific gravity of the
approximately true for most waters and wastewaters.
If the specific
gravity
is
not
conversion can be calculated from
concentration in
ppm
(mg/kg)
=
concentration
in
(mg/L) x
specific gravity of solution
For very dilute solutions
This
is
it
may
be more convenient to express the concentration
equivalent to parts per billion (ppb). where a billion
is
micrograms per
in
understood to be 10 9
.
liter
(Ug/L).
Sec. 6.3
153
Solutions
Within each of these two systems, there are several methods for expressing concentrations:
1.
Mass/mass
(or weight/weight)
(a) Percent
by weight
Example: Solute 1% NaCl
99% H 2
Solvent
Example: 10,000
(b) Parts per million
10,000
(c) Molality,
m =
gram mole of NaCl
1
,,.....,
(d)
in
Mole
=
=
(solute)
H2
H2
solute per 1000 g of solvent
58.5 g
1000.0 g
1058.5 g
1
of solution
number of moles of solute, n
total number or moles, n
=
,.
.
fraction, X.
NaCl/kg
water with a molality of
(solvent)
2
mg
number of gram moles* of
Example: NaCl solution
H
parts NaCl/million parts
;
;
l
The following example
Example
will illustrate the conversion
mass/mass
2%
by weight NaCl solution
=
For(b)
'T5o
For
(c), molality,
For
(d),
mole
.
mole
HTo^
m=
fraction
c
fraction
is
refers to a fixed
cules or particles;
appropriate units
example,
I
water
in
terms of the other
'
2/58 5
XNaC1 =
v
X^
=
=
(Any other weight would
also do.)
We
PP m
0.349
2 /58 5
2/58*5 +98/18
98/18
2/585+98/18
=
°'° 062
0.9938
= r^oo
unity.)
amount of a substance that contains Avogadro's number of molecules. Therefore, the
number of any type of particles rather than a weight. In practice, we do not count mole-
the
we weigh them.
—
=20 000
nnQQQ
(The sum of mole fractions must equal
One mole
in
units.
Solution Choose 100 g of solution as a basis.
have 2 g of NaCl and 98 g of H 2 0. Thus
"
to the others.
6.2
Express the composition of
mole
from one method
Therefore, an engineering definition of a mole
g. kg. lb, ton, etc.)
gram mole of oxygen
=
which
is
is
that
mass of a substance
(in
numerically equal to the molecular weight of the substance. For
32 g of oxygen.
154
2.
Physics and Chemistry
Chapter 6
Weight/volume
(a)
mg of NaCl in 1 L of solution
number of gram moles of solute per 1 L of solution
Example: NaCl solution of molarity =
M, contains gram
mole or 58.5 g of NaCl per liter of solution.
Solutions of equal molarity have equal numbers of molecules
mg/L
Example: 1000
(b) Molarity,
M
=
1
of dissolved substance per
(c)
Normality,
N =
liter
1
or per any other unit volume.
number of gram-equivalent weights of
solute per
1
L
of so-
lution (eq/L)
(d)
meq/L.
more convenient
For very dilute systems,
it
milliequivalents per
(meq/L) instead of (gram) equiva-
liter
Note
lents per liter (eq/L).
eq/m 3
1
Expressing Normality.
=
is
often
that
1
eq/L
=
to use
1000 meq/L, and
meq/L.
1
Because a given substance can have more than one
gram-equivalent weight, depending on the reaction
it
undergoes,
it
is
necessary, in ex-
pressing a concentration as a normality, to specifiy in what reaction or type of reaction
the solution
is
going to be used.
.
.
.
In general,
,
equivalent weight (g/eq)
=
—
atomic or molecular weight (g)
where n
is
—
:
//
(6.9)
(equivalents)
a positive integer and
-number of protons donated
total
change
in
oxidation
(in
acid-base reactions)
number of
a
compound
(in
oxidation-reduction
reactions)
For example,
n
=
1,2, and
in the
acid-base reactions,
H3PO4
+ NaOH
->
NaH 2 P0 4 + H 2
H3PO4
+ 2NaOH
-»-
Na 2 HP0 4 + 2H 2
H3PO4
+ 3NaOH
->
Na3 P04 + 3H 2
3, respectively.
The advantage of normal
B
is
the same,
1
mL
of
A
solutions
is
that if the normality of
will react with exactly
1
mL
This
of B.
two solutions
is
VA NA = VB N B
where /VA /VB are the normality of solutions
equivalent weights in
L of solutions of A an
,
1
A(B) of normality
Therefore,
if /VA
mality of an
NA
= NB
unknown
(/V B
,
)
that reacts with
then Va
solution.
= VB
.
A
A
and
because
(6.10)
and B, which
is
the
number of gram-
B and VA VB are the volume of solution
volume VB (VA of normality NB (NA ).
,
)
This relationship can be used to find the nor-
Sec. 6.3
Example
155
Solutions
6.3
NaOH/L.
solution contains 5 g
If a
weight/volume units expressed as
ture of the solution
The
20 C.
is
the concentration
calculate
mg/L.
(a)
reaction
and
(b) molarity,
NaOH
of
normality.
(c)
in
terms of
The tempera-
is
H,P0 4 + 3NaOH
-> Na-,PO_,
+ 3H :
Solution
Concentration
(a)
Concentration
(b)
Note:
To convert molarity
mg/L =
=
5000 mg/L
molarity
=
——
-
=
0.
125
M
mg/L, use
to
gram molecular weight x 10 3
0.125 x 40 x 10 3
=
Equivalent weight tor
NaOH
ot equivalent weights ot
NaOH
(c)
Number
in
molarity x
=
mg/L
in
5000 mg/L
in
L
1
=
reaction
in this
=
solution
40=s
s
—
= 40 g/Eq
o/L
5 &
An
/r,
40 g/Eq
=
0.125 Eq/L
Therefore.
N = 0.125
Normality
Example
Eq/L
6.4
Determine the normality of
tion of 35.0
mL
of a 0.2
NaOH of
A drop
a solution of
N
HCI
solution.
which 17.5
mL
is
required
in the titra-
of methyl orange indicator in the acid
solution serves to indicate the end point of titration, by a change in color.
Solution
NaOH
From equation
Then
(6.10).
VA NA
= VB /V B
Let
.
A
be the HCI solution and
„
WnuOH
=
Concentration
—
v hc\
x ^hci
r,
v
Therefore, the normality of the
NaOH
terms of a
in
=
— —
35.0 x 0.2
ptt
llJ
NuOH
solution
is
=
0.4
water.
different chemical forms,
0.4 N.
common
This method
is
all
containing the
constituent.
nitrogen
common
It
has been found
common
constituent
constituent, are present in
not used in general chemistry and therefore requires explanation.
For example, nitrogen compounds can be present
Ammonia
the
N
useful in water chemistry to express concentrations in terms of a
when
B
solution.
NH 4
T
.
NH
3
Organic nitrogen
various forms
Nitrite nitrogen
NOt
Nitrate nitrogen
NOj
in
the following forms in wastewater:
156
Physics and Chemistry
It is
compared
customary
to report all results in terms of nitrogen (N) so that values
For example, Figure 6-4 shows the changes occurring
directly.
of nitrogen in a wastewater under aerobic conditions.
as
Chapter 6
mg/L N. The expression 10 mg/L
mg/L expressed as N.
NO^ N
means
in the
that the nitrate
(NO-^
)
concentra-
en
E
O
Figure 6-4
Example
A
Forms of nitrogen compounds
wastewater under aerobic conditions.
in
Sawyer and McCarty (1978).
6.5
nitrogen analysis of a wastewater sample gave the following results:
Ammonia
30.0
mg/L
NH
Nitrite
0.10
mg/L
NOJ
Nitrate
1.50mg/L
Organic nitrogen (various forms)
5.0
Find the
total
mg/L
3
N0 ~
3
N
concentration of nitrogen.
Solution
Ammonia
Nitrite
NH =
3
NOT1 =
j^
^
46
forms
All concentrations are expressed
tion is 10
Source:
can be
x 30.0
=
24.70 mg/L
x 0.10
=
0.03
NH " N
mg/L NO,"
l
3
N
,
Sec. 6.3
157
Solutions
NOf =
=
0.34
mg/L
Organic nitrogen
=
15.0
mg/L N
Total concentration of nitrogen
=
40.
mg/L N
Nitrate
^
The common-constituent method
tration
x 1.50
is
1
NOj N
also frequently used for phosphorus concen-
and for expressing the hardness and alkalinity of water, both of which are part of
+2
the carbonate system. Hardness is caused by divalent metallic cations, principally Ca
2
+2
while alkalinity is contributed by the anions
and OH~. It
and
Mg
CaCO}.
HCO^ CO^
.
has been
,
common
but the use of "equivalents"
hardness
(in
mg/L
as
is
We
increasing.
CaCOO = M+ 2
50 "ig/meq
mg/L) x
(in
M +:
Note
represents a divalent metallic ion.
mg/L of
have*
equiv wt
where
,
practice to express hardness and alkalinity in terms of
(6
No-
that n in equation (6.9) is
,
}
now
equal to 2 based on the reaction
CaCO,
Example
—
Ca+ 2
+ CO^ 2
6.6
Calculate the hardness, in
mg/L CaCO,, of
Cone.
Cation
40 mg/L
23
Mg+ 2
mg/L
55 mg/L
2 mg/L
20.0
10
K+
Only
equation (6.1
1
wt
Equiv.
Na +
Ca+ 2
Solution
a water sample with the following analysis:
the divalent
ions
12.2
39.0
Ca +2 and
Mg +2
contribute to hardness.
Thus, from
).
hardness (mg/L CaCO-,)
=
=
55 x
138
'For conversion between milliequivalents per
-^- +
+
liter
milhequivaient weight of CaCO-i
10 x
40/2
=
41
of Ca'
= —
2
24.3/2
179
:
or
mg/L
Mg
—
-
meq/mol
'
2
=
as
CaCO,
and milligrams per
50 mg/meq
liter
as
CaCOj,
158
Physics and Chemistry
Chapter 6
6.3.3 Acid-Base Reactions
Acid-base reactions, perhaps the most important class of chemical equilibria, are partic-
Examples include
ularly important in water chemistry.
the carbonate system
and
its
re-
lationship to pH, acidity, and alkalinity; the concentration of metal ions in water; water
softening; and certain precipitation reactions and oxidation-reduction reactions.
Lowry-Bronsted definition of acid-base. There are several definitions
The most common is that of Lowry-Br0nsted. It states that:
of an acid and a base.
An acid is a substance having the tendency to lose or donate a proton (H+),
and a base is a substance having the tendency to add or accept a proton.
we must always
Therefore, in an acid-base reaction,
some substance
base),
Two
an acid because
the proton to
become
other proton and
is
H
it
a conjugate acid, here
conjugate acid-base
first is
ci-
3
conjugate
conjugate
acid
base
(6.12)
can donate a proton (H + ) to the base H 2 0, which can accept
+ Once an acid has donated a proton, it is able to accept an.
3
therefore termed a conjugate base, here Cl~.
having accepted a proton,
When
H 0+ +
?=
base
acid
is
The
reactions, both involving water, further illustrate the definition.
HCI + H 2
HCI
have, in addition to the acid (or
that will accept (or donate) the proton.
Similarly, a base,
now in a position to donate a proton and is therefore called
+ HCI and Cl~ differ only by a proton. They are called a
is
H3
.
pair, as are
H 3 0+
H 2 0.
NH a
and
water reacts with ammonia,
3
rather than as a base as in equation (6.12).
NH + H
3
base
^
2
,
We
base, the water behaves as an acid
have
NHJ + OH"
acid
conjugate
conjugate
acid
base
Here we are dealing with the conjugate acid-base
pairs,
(0.13)
NH^ and NH
3
,
and
H2
and
OH".
The
strength of an acid, that
can be measured by comparing
base, as
shown
in the
HA
large or small
tendency against a
its
tendency
common
is
base.
to lose a proton,
Water
is
such a
general reaction
HA + H
where
how
is,
this
stands for an acid.
2
^
H
+
3
+ A-
The equilibrium constant
for this reaction
(6.14)
is
Sec. 6.3
159
Solutions
[H,Q + [A-j
]
KA =
where
[•]
means
Table 6-1
versa.
also indicated.
KA is then also called the acid disconjugate base will be weak, and vice
"the concentration of," in mol/L.
When
sociation constant.
constants at a
[HA]
a
lists
common
an acid
strong,
is
number of
its
acids, their conjugate bases,
The use
temperature of 25 C.
and
their dissociation
or occurrence of these acids
Information on other dissociation constants
at different
is
temperatures can
be obtained from handbooks of chemistry.
Examples of strong acids
All strong acids are completely dissociated.
vided
in the
Weak
Strong acid
HCL
H 2 S0 4
HNO,
HC104
Hydrochloric acid
Sulfuric acid
Nitric acid
Perchloric acid
As we have
Ionization of water.
HS0 4
NOf
cio 4-
learned, water can act either as an acid or
—
base
acid
dissociation constant
K=
which
is
itself
It is
weakly and reversibly ion-
shown by
H.O + H 2
The
conjugate base
ci-
a base, depending on the other reacting substance.
ized, as
K
is
[H 3 0+]
OH
H3O+ +
conjugate
conjugate
acid
base
[OH-]
=
1.8
x 10"
I6
mol/L
(at
[H 2 0]
usually simplified to
]
•
[OH"]
= K\H
2
0\
where
,h 2 o]
=
m^
18g/mol
so that
KH =
is
called the ion
(6.15)
given by
[H,0 +
KH
are pro-
following table:
1.8
x 10"
product constant
l6
x 55.5
for water.
=
1.0
x 10"
l4
25°C)
IS
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Sec. 6.3
As
161
Solutions
in the
case of the acid dissociation constants
ion product constant for water, as
shown
T(
C)
C
dissociation at 100
The pH
10
x lO"
2.9 x 10"
20
6.8
25
1.0
30
1.5
x lO" 15
x 10" 14
x 10" l4
100
7.0
x 10" 13
However, because
pOH
is
the
this is
awkward,
in
at
0°C.
its
molar
the convention has
terms of
its
negative log-
Thus
of the solution.
pH = and similarly,
,
15
been established to express the hydrogen ion concentration
pH
Kw
l5
strength of an acid or base can be indicated by
concentration of hydrogen ions.
arithm, called the
temperature affects
more than two orders of magnitude greater than
is
The
scale.
,
K»,
1.1
The
Ka
following table:
in the
log[H 3 0+]
(6.16)
used to signify the negative logarithm of the hydroxide ion con-
centration, so
pOH = -log[OH"]
= Kw =
Because [H,0+][OH-]
10"
l4
at
25°C,
pH + pOH =
An aqueous
solution that
H
equal concentrations of
solutions with a
3
pH below
is
it
(6.17)
follows that
14 at 25 °C
neutral (i.e., neither acidic nor basic) has by definition
+ and OH" ions, and at 25 °C its pH = pOH = 7. Aqueous
7 are referred to as acidic, and those with a
called basic or alkaline.
Example
6.7
pH
of a solution with
(a)
Find the
(b)
Find the [H,0 + ]
Solution
(a)
if the
From equation
pH
[H,0 +
]
of a solution
=
3.4 x
10
4
mol/L.
is 6.7.
(6. 16),
pH
=
-log|H,0 +
=
-log3.4
-
=
-0.53
+
4
=
3.47
]
= -
log 10
log(3.4 x 10" 4 )
4
pH above
7 are
162
Physics and Chemistry
6.7
(b)
= -
Chapter 6
|og[H3 0+]
or
10- h7
LO
-
x 10-
3
7
=
[H,0+]
= H,0+
or
|H,0 +
]
The carbonate system.
air-water interactions
=2
x 10- 7 mol/L
The most important acid-conjugate base system
the carbonate system.
is
It
controls the
pH
in
of most natural waters
and consists of the following species:
C0 2 in
H 2 C0 3
•
Carbon dioxide,
•
Carbonic acid,
•
Bicarbonate ion,
•
Carbonate
•
Carbonate-based
gaseous form
C0 2 {g)
or dissolved in water
C0 2 (aq)
HC07T
CO^ 2
ion,
Examples of
,
solids, principally
calcium and magnesium
the importance of the carbonate system in the environmental field in-
clude:
C0 in biological respiration
C0 2 in photosynthesis
interchange of C0
•
The production of
•
The consumption of
•
The air-water
•
The
dissolution
2
2
of carbonate
minerals,
principally
CaC0 3
and
MgC0
3
,
by
groundwater
•
The
buffering capacity of natural waters, principally due to the carbonate system
(acidity
•
and
alkalinity)
Water softening
•
Several water and wastewater treatment processes
•
The interchange between
solid
and dissolved forms of
CaC0 3 (MgC0
3
)
at
the
bottom of lakes
The nature of the carbonate system is difficult to establish. It may be involved in homogeneous (one-phase) solution equilibria as well as heterogeneous air-water and water-solid equilibria.
Snoeynik and Jenkins (1980) have
1.
2.
3.
4.
An open
An open
A
A
identified four systems:
system with no solid present
system with a solid present
closed system with no solid present
closed system with a solid present
1
Sec. 6.3
163
Solutions
shown and described in Figure 6-5. The calculaopen and closed systems, and in the presence
of metal ions and of carbonate-containing solids, is beyond the scope of this book. A
Some examples
of real systems are
tions of carbonate species concentration in
detailed treatment can be found in Snoeynik and Jenkins (1980) and Butler (1982).
The
equilibria for the carbonate system are as follows
Equation
Equation
Equilibrium
Air
= water
C0 2 (g)
= CO
number
Equilibrium constant?
KH =
: <</</
2
3.2 x It)-
(6.IS)
(see Henry*s law,
Section 6.4)
C0
In v^ater
2
(aq)
+H
-H
:
:
H 2 CO;
h
K,„
=
x 10" 3
1.6
(6.19)
(dimensionless)
H 2 C0 + H.O
3
HCO,+H
Solid = water
T
•Constants are for
*K„,
=
1.6
customary
x 10- 3
to let
:
— H,0- +
— H,0- +
CaC0 3 (.9)
?=
Ca+
CaC03(i) + H,0+
j=i
Ca~ 2
=
=
25 C.
For values
at
2
= 4.2
x 10" 7 mol/L
HCO3-
A'„,
CO^
Ka2 = 4.8 x
+ CO,
2
Kso = 5.0
2
+ HCO, + H
lO"
11
(6.20)
mol/L
(6.21)
x 10~ 9 mol 2/L 2
(6.22)
K = Kso /Kal
:
(6.23)
other temperatures, refer to handbooks.
that [H 2 C0 3 ] « [C0 2 (aq)l
[C02(aq)] + [H2 C03 ],
[H : CO,/CO : (a^)]. indicating
|H : COj] represent the sum of
However,
a ratio of about 1:600.
it
is
Buffering capacity of natural waters.
A knowledge of the carbonate
helps
us
understand
how
waters
system
to
most natural
are able to resist changes in pH
upon the addition or formation of acidic or alkaline material.
buffering capacity
tem.
in
is
Bases such as
pH when
In natural waters this
attributable mostly to the presence of species of the carbonate sys-
HC0 ,CO^
:
3
a strong acid
.
added.
is
and
OH"
give the water the ability to resist changes
Acids such as
H^CCMCOt), HCO^
and
,
H
+
3
provide buffering against the addition of strong bases.
A
buffer
is
6
to 9 that
to a
weak
titration
is
is
added
to or
acid
(FTCO, and
)
this
a strong acid
pH when
(H 2 S0 4 ).
curve of carbonic acid that buffering
pH
range.
in the solution.
Within the
most natural waters, only weak acids and bases have
characteristic of
whereas the steepness of the sulfuric acid
in
formed
Figure 6-6 shows what happens to
capacity.
pH when
pH range
a substance in solution that offers resistance to changes in
acidic or alkaline material
in the
titration
This resistance to change
in
a strong base
(NaOH)
Note from the sloping
pH
range 6 to about 8.5
is
this
added
part of the
is
provided,
curve indicates no buffering capacity
pH upon
the addition of alkaline or
acidic material will be explained shortly.
In a natural
(HCO,"
)
water (pH about 7) containing free
the reactions of the
CO
:
and HCO^"
C0 2
dissociation of the water itself (equation (6.15)) illustrate
restate these equations as
and bicarbonate
alkalinity,
[Equations (6.19) and (6.20)1 mid the
how
buffering occurs.
Let us
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Sec. 6.3
165
Solutions
\tL
/y
Acid,
10
4
S0
2
Sulfuric
H
H 2 C0 3 + H 2
8
with K,
=
=
+
H3
4.2 x 10
7
at
+
HC0 3
25 C
IQ.
6
~
4
2
I
I
I
I
I
I
I
I
I
i
i
i
i
i
i
NaOH
Figure 6-6
Titration curves for carbonic acid and sulfuric acid.
2
^
H 2 C0
H 2 C0 + H 2
^
H3
^
H3O+ + OH-
CO + H
:
3
H2
If
we add
a small
+
= Kw =
But a decrease
].
tion (6.24), to the right,
net result
is
in
pH
H
3
ter
pH
(6.25)
(6.26)
,
an increase
(i.e.,
OH"
in
will shift equation (6.25),
|
a slight increase in pH.
[HC0
3
]
+
and [H 3
J
we add OH"),
then
causes a decrease in
and therefore also equaand reducing
C0
2
.
The
This addition of hydroxyl ions can be continued
until all free
C0 2
has been converted to
HCOf
at
of about 8.3. Similarly, if we add a small amount of a strong acid, say, HCl, the
+ will increase. This will shift the equations to
the left, the end result being an in-
crease in free
in
-14
producing more
in
+ HCO,
a highly alkaline material
10
+
[H 3
without any marked increase
a
2
amount of NaOH,
because [H 3 0^][OH~]
[H 3
+ H
+
(6.24)
3
C0 2
and a
slightly
lower pH.
an extremely important property, because
upon
This buffering capacity of natural waters
it
prevents large shifts in the
the addition of acidic or alkaline contaminants.
aquatic
life
stroyed
if
forms have a relatively narrow range of
pH
Many
pH
of the wa-
bacteria and other
tolerance and would be de-
they were not protected by the carbonate system.
166
Physics and Chemistry
and
Acidity
The acidity of
alkalinity.
to neutralize bases; alkalinity
is
a water
a measure of
is
a measure of the water's capacity
Chapter 6
capacity
its
to neutralize acids.
From an examination of the titration curves of a strong acid (H 2 S0 4 and a relatively
weak acid (H 2 C0 3 (C0 2 )) in Figure 6-6, it is apparent that below pH 4.5, acidity is due
)
(H 2 S0 4 ), whereas between pH 4.5 and 8.5,
(NaOH).
waters, carbon dioxide from the atmosphere and from the bacterial oxidation
to the presence of a strong mineral acid
H 2 C0 3 (C0 2
In natural
the source of the acidity tending to neutralize the strong base
is
)
of organic matter and mineral acidity from industrial wastes, from mine drainage, and
from acid
man
Acid waters are not a
rain are the principal sources of acidity.
threat to hu-
and because
health, but they are of great concern because of their corrosiveness
they upset the ecology of lakes.
known volume of
end point,
at
pH
Acidity
is
determined
by
in the laboratory
titrating a
sample with a standard solution of an alkaline reagent
the
4.5 or 8.5 (depending on the type of acidity present),
points can be indicated by a
pH
is
until the
reached.
meter or by chemicals that change color
at
pH
End
4.5 or
8.5 (methyl orange or phenolphthalein).
Bicarbonates, formed by the action of
C0 2
on basic materials (equation
(6.27)),
enter surface waters, where they represent the major form of alkalinity:
C0 2 + H 2
At higher
pH
levels, natural waters
and hydroxide
shown
alkalinity, as
may
->
Ca(HC0 3
also contain considerable
Total alkalinity
pH
4.5.
m 6 /L
as
is
The
total alkalinity
,
A
is
convenient for expressing alkalinity
CaC0 3
since the equivalent weight of
(mg/L
as
CaC0
=
Example
with dilute sulfuric acid to the endpoint
titration
The use of N/50 H 2 S0 4
CaC0 3
waste sample of 100
alkalinity in
Solution
total
mL /V/50 H,S0 4
to
We
at
about
terms of
have
pH
x
4.5
-
mL
100°
(6.28)
,
sample
mL
requires 7.5
mL
of
N/50 H 2 S0 4
From equation
sum of
pH
4.5.
What
is
(6.28),
The forms and concentrations
accurately,
to titrate to
mg/L CaC0 3 ?
=
7.5
in
x
^5
which
=
75
mg /L
alkalinity
found from the preceding alkalinity measurements
the
50.
is
in
3 )
total alkalinity
more
from
6.8
its total
or,
C0 2
alkalinity of water, either
on humans, but highly alkaline waters are unpalatable.
effects
ill
measured by
amounts of carbonate
be caused by algae, which remove
water through photosynthesis and thereby increase pH.
high or low, has no
(6.27)
)2
Figure 6-7, which indicates the relative amounts
in
pH may
Higher
of carbonate in water.
+ CaC0 3
(i.e.,
is
by
as
CaC0 3
present in a water can be
titration
with /V/50
by calculations based on the equilibrium equations and the
the cation concentration
must equal
that of the
anion concentration.
H 2 S0 4
)
fact that
Sec. 6.3
167
Solutions
100
E
CO
o
o
o
to
w
CO
c
76
-2£
Figure 6-7
Relative amounts of
CO
:
HCO3.CO,".
.
and
(values calculated for water with a total alkalinity of
100
OH
at
mg/L
various
at
pH
25 C).
levels
Source:
Sawyer and McCarty (1978).
For the calculational method, the applicable equations are equation (6.15) relating
H^O
and OH. namely,
[H 3 0+][OH-]
= Kn =
1
x 10-
l4
at
25
C
from which, by measuring pH, the hydroxide alkalinity |OH| can be calculated, and
equation (6.21) relating
CO3 and HCO3,
|H 3 0+l[CQ:r 2
l
namely.
= K„7
=4.8 x 10-"
25
at
C
(6.29)
[HC03-]
Now, because
all
the cations and anions
the cations being
measured except
[alkalinity!
Note
+
[H3 0+]
that the carbonate concentration
must balance, and since
+ ion,
H3
for the
we
alkalinity
= HCO^ + 2[C0^ 2 + [OH
[
[COf 2
|
]
is
is
equivalent to
can write
]
multiplied by 2 since
|
it
(6.30)
combines with
168
Physics and Chemistry
two hydrogen ions
forming carbonic acid, and
in
mol/L. Concentrations
in
mg/L
CaC0 3
equivalent weight of
The unknowns
CaC0
as
3
that the ion concentrations are in
are 50,000 times these values, since the
[HCO^]
can be found by solving these equations simultaneously.
Carty, 1978)
gram
50.
is
equations (6.29) and (6.30) are
in
Chapter 6
The
and [CO3" 2
].
These
(Sawyer and Mc-
result
is:
carbonate (CO3" 2
total alkalinity
)
(mg/L
alkalinity
(mg/L
as
CaC0
as
CaC0 3 +
)
3 )
- 50,000(K u ,/[H O+])
50,000[H 3 O+]
3
:
(6.31)
l+[H 3 0+]/2£
fl2
bicarbonate
(HCO^
total alkalinity
)
(mg/L
alkalinity
(mg/L
as
as
CaC0 3
)
CaC0 3 + 50,000[H 3 O+] + 2K„ 2 /[H 3 0+]
)
50,000(K ./[H 3 O+])
ll
(6.32)
1
Example
6.9
The following information
available
is
Total alkalinity
75 mg/L as
Temperature
25 °C
pH
10.1 (by
CaC03
pH
on a waste water sample.
(by titration)
meter)
Calculate the bicarbonate, carbonate, and hydroxide alkalinities.
Solution
From equation
(6.16),
10.1
log[H 3 0+]
101
=
[H,0+]
10""
=
[H3O+]
[H3O+]
=
7.9 x
10"
10 09 x
From equation
= -
=
75 +50,000 x 7.9 x (10)-"
I
75+3.9
I
-
50,000[10~
l4
/
(as
x 10" 6
-
6.3
+0.82
™
r
CaC0 3 =
.
75
68.7
=
37.8
1.82
+
3.9
)
1
(6.15),
/(7.9 x 10"")]
+(7.9 x 10-")/(2 x 4.8 x 10-")
(6.32),
/i
urn
mg/L
HCO,
From equation
mol/L
(6.31),
mg/L CO3- 2 (asCaCQ 3 )
From equation
10"
+
x
1
10^-6.3
/0 82
=
68.7
2~22
=
.
Sec. 6.4
169
Gases. Gaseous Mixtures, and Gas-Liquid Transfer
[OH
]
=
x 10" 14
1
[H,0-
mg/L [OH-]
CaCO,)
(as
=
—
50.000 x
7.9 x
Check: Total alkalinity
=
37.8
+
30.9
+
=
6.3
10""
=
6.3
75 (by calculation).
GASEOUS MIXTURES,
AND GAS-LIQUID TRANSFER
6.4 GASES,
A
knowledge of
conditions
tal
is
the behavior of gases
necessary for
and land pollution.
gases,
rich,
CO : CH 4
,
and gaseous mixtures under varying environmen-
air pollution control as
For example,
H 2 S, are produced, which are, respectively, corrosive, energy
Gas from organic decomposition in landfill sites can lead to fires
and
,
and poisonous.
and explosions, which can be dangerous
dition, the dissolution
of gases
in liquids
to
any development on or near the
of
all
from liquids are of particular significance
In this section
most environmental
most
well as for the control of water
anaerobic digestion of wastewater, three main
in the
we
to the environmental engineer
Through
low enough pressures
tion 6.3, Raoult's
and
scientist.
that they
In
behave
al-
the experimental study of gases, certain "laws" or gen-
eralizations have been evolved: Boyle's law, Charles's law (also
law), the ideal gas law,
In ad-
review ideal gases and the laws describing their behavior.
situations, gases are at
like ideal gases.
site.
kinds and the removal of dissolved gases
and Dalton's law (Mahan, 1975).
known
as
Gay-Lussac's
For the reasons noted
in
Sec-
law and Henry's law, which deal with gas-liquid systems, are pre-
sented after the gas laws.
6.4.1 Gas Laws
Boyle's law.
The volume
That
Boyle's law states:
of a gas varies inversely with
its
pressure at constant temperature.
is,
'at
T constant
^
7>
(0.33)
T
a
7>
(6.34)
or
''at
constant
or
PVx
Figure 6-8a
T2
,
and
73
these curves
is
/constant
=
a plot of pressure versus
volume
with the experimentally measured
would be
the
same
=K
constant
P-V
(6.35)
for a gas at three temperatures
data points shown.
as equation (6.35), of the
form xy
=
'/',
Equations for
constant,
which
is
170
Physics and Chemistry
Chapter 6
Q.
to
Q.
CD
a.
Volume,
l/(L)
(a)
Figure 6-8
Relationship of pressure to volume.
the mathematical expression for a hyperbola.
A
plot of
P
versus \IV (Figure 6-8b)
at
a constant temperature should yield a straight line; therefore, a plot of the experimental
values enables us to judge
how
closely the gas follows Boyle's law.
Boyle's law has direct application in converting measured gas volumes
pressures
(i.e.,
at
various
altitudes) to standard conditions.
Charles's law (or Gay-Lussac's law).
The volume of a gas
Charles's law states:
at constant pressure varies in direct
proportion to the absolute
temperature of the gas.
Experiments, show that for
ume
all
gases held
at a
constant low pressure, the increase in vol-
for each degree Celsius rise in temperature
is
^
the
volume of
273
+ Tr
the gas at
C, or
At constant P:
V=
If
we
define a
Vo
c
new temperature
T
-\
273
scale
Tk
TK =
where Tc
tually,
is
V °° c
V o°c
such that
T=
273
+ Tc
the temperature in degrees Celsius; and at
273.15); and
TK = T =
(6.36)
273
Tc =
0°C,
TK = T = 273
()
absolute temperature in kelvin, equation (6.36)
At constant P:
Tn
(ac-
becomes
171
Gases. Gaseous Mixtures, and Gas-Liquid Transfer
Sec. 6.4
or
Vn
V
Figure 6-9
is
ture,
and
constant
P
=
T
T
constant x
(6.37)
a plot of equation (6.37) relating the volume of any gas (since
have the same volume
at different
at
at
the
same temperature and pressure)
all
gases
to the absolute temperature
Charles's law applies over a limited range of tempera-
constant pressures.
Theoretically, at
straight lines result.
=
T
{)
K,
V
=
0.
however,
In fact,
gases will liquefy or solidify long before the absolute zero temperature
is
reached, and
would be shorter than shown. Nonetheless, extrapolation of the lines
where they intersect the temperature axis would show
point of intersection is the same for all gases and near
K (— 273°C).
the straight lines
for different gases to the point
that the
Figure 6-9
200
7"(K)
Relationship of volume to
temperature.
Charles's law can be used to calculate pressure in rigid containers as the temperature varies.
Determination of the required size of gas tank and the pressures to be ex-
pected over a range of temperatures would be a practical application of the combination
of Boyle's and Charles's laws.
Ideal gas law.
temperature
V:
).
late
T of
Experimentally,
V2
.
Let us
a gas vary
now examine
between
state
we have measured
V,
7",
Pj, T\, V,
,
,
when
and V,) and
P2
,
and
7\,
the pressure
state 2
(P 2
and we wish
,
P
T2
,
and
and
to calcu-
Then, from Boyle's law.
a ' 'constant
where
the situation
(P,,
1
is
the
volume of
the gas at T\
_
'
and
:
I
P2
Vx _
—
77"
.
P,
~n~
(6.38)
172
Physics and Chemistry
From
Chapter 6
Charles's law
V
=
at Constant
Pi- 77
=
X
T
^
(6.39)
I
or
I/,
= V
v
-
=
V,
=
constant
-i x
^
which, upon rearranging, becomes
V,/>,
V2 /
/-,
/
=K
2
In general, then,
PV = AT
The numerical value of
units of
P,
V,
and
T.
A" is
It is
(6.40)
determined by the number of moles of gas involved and the
independent of the type of gas. Let
K = nR
where n
gas).
is
the
number of moles of gas and R
is
the universal gas constant (per
mole of
Then
PV = nRT
Equation (6.41)
is
called the ideal gas law.
tion of state that applies to real gases.
It is
(6.41)
the simplest
form of the general equa-
For low pressures and normal temperatures, most
The numerical evaluation of R can be obtained from the
gram mole of any ideal gas at standard conditions [standard
temperature and pressure (STP)] of 0°C (273.15 K) and 101,325 Pa occupies a volume
gases, behave like ideal gases.
experimental fact that
of 22.414 L.
1
Therefore,
R
_PV
~ nT
101,325
'"
=
8.31
N/m 2 x 22.414 x 10~ 3
lgmol x 273.15 K
N m/K
•
•
mol
=
8.31 J/K
•
m
3
mol
(Exact value 8.31441)
The dimensions of R
are
ML
t
If
of
2
2
T molj
•
P is in atmospheres and V is in liters, R = 0.082056 L atm/K
R in different systems of units can be obtained from handbooks.
•
•
mol.
Other values
173
Gases, Gaseous Mixtures, and Gas-Liquid Transfer
Sec. 6.4
Dalton's law of partial pressures.
Dalton's law states:
In a mixture of gases, each gas exerts pressure independently of the other gases.
The
partial pressure of each gas
is
proportional to the amount, as measured by
percent volume or mole number, of that gas in the mixture.
That
is.
where
P,
is
the partial pressure gas
the pressure
If
+ P2 +
P,
total
/
+
Py
would exert
=
••
if
IP,
filled the total
it
volume alone.
and temperature of a gaseous mixture are not extreme, we may use
which contains n k moles of gas A, n B moles of gas
volume V and at temperature T. In that case, the
the ideal gas law for the mixture,
B. and n c moles of gas C, with a total
gases are given by
partial pressures of the three
*A
Pb
PC
n
-
RT
x
y
V
rtota
,
"total
=-L
= -V"
v
(6-42)
^.o«a.
"total
n c RT
= —y~ =
r
and the pressure
n.
-
—
nc
P.otal
"total
is
P.otai
=
Pa
+
^b
+
Pc
=
RT
("a
+
+
"b
=
«c) x ~y
RT
" tolal
(6 43)
'
~V
Example 6.10
The pressure gauge on
kPa.
a watermain indicates 80 psig.
The atmospheric pressure
is
100
Calculate the absolute pressure in pascals in the watermain.
Solution
Absolute pressure
=
gauge pressure
=
80
=
551,600+ 100,000
=
651,600 Pa
=
65
psi
1
.6
in
x 6,895 Pa/psi
+
atmospheric pressure
100,000 Pa
some time
to get used to.
For those famil-
with pounds per square inch (psi) or pounds per square foot, the conversion to pascals
seems awkward.
I
+
kPa
Note: The pascal as a unit of pressure will take
iar
main
atm (14.7
Germany and
(Chapter
1).
psi)
However, one simple relationship
is
that,
100 kPa. which
is
called a bar.
is
approximately
other countries, and the millibar (100 Fa)
is
lor elevations near sea level.
a
The bar
is
used
in
basic unit in meteorology
174
Physics and Chemistry
Example
Chapter 6
6.11
Calculate the required volume of a gas tank that must hold at least 7 days of
duced in a digestion process. Daily gas production
is 25 °C, and the pressure in the tank is 200 kPa.
is
CH» gas proThe temperature of the gas
500
kg.
=
16 g
Solution
CR,
Molecular mass of
u
Number
ht
=
12
i/i =
+
x
(4
1)
7 x 500 x 1,000
—
off g mol/week
1onen
= ~218,750
16
From equation
(6.41),
nRT
p
v
218.750 (g mol) x 8.31 (J/K
g mol) x 298 (K)
20a000(Pa)
_
-
._
„
nc
J/Pa
2708.5
,
Since
Pa
= N/m 2 =
=
(kg
m/s 2 )/m 2
kg/m/s 2
and
J
it
follows that J/Pa
Example
= m3
=N m=
•
kg
•
m 2/s 2
and the required tank volume
=
m
3
.
6.12
The composition of
CH 4 30% C0 2
,
,
digester gas from the anaerobic digestion of wastewater sludge in
and
2% H : S.
1000 kg of the gas mixture
If
sure of 300 kPa(/?,), calculate the partial pressure of each
Solution
The molar masses of
For
CH 4
C0 2
44 g/mol
For
H2 S
34 g/mol
For
2708.5
the
components
is
component
are:
16 g/mol
The amount of each component present
is
given as follows:
——
1000 kg
x 1000 g/kg
£——
^—2 x 0.68
.„
.„
=
42,500 mol
n co
=
6,820 mol
nH s
=
590 mol
=
49,910 mol
n CH
ru
and therefore
=
4
;
.
16 g/mol
ra totai
stored in a tank
present.
at
68%
a pres-
175
Gases, Gaseous Mixtures, and Gas-Liquid Transfer
Sec. 6.4
The
partial pressures are then
—V,
Pch =
4
=
g^
x300kPa =255kPa
Pco
=
41 kPa
PHS
=
4 kPa
P, oljl
=
300 kPa
6.4.2 Gas-Liquid Transfer
Raoult's law deals with the vapor
Raoult's law and vapor pressure.
whose properties are a molar average of
corresponding properties of the components of that solution). Raoult's law states:
pressure of an ideal solution (defined as one
the
If a solution
obeys Raoult's law, the partial pressure of any component depends
and second, on how much of it is present in the solution.
The vapor pressure of the component measures the first property, while the mole
fraction of the component measures the second.
first,
on how
volatile
Mathematically,
this
it
is,
can be expressed as
Pa
=
PA =
where Pa
partial pressure
=XA PA
A
of component
vapor pressure of substance
in
(6.44)
equilibrium with the solution
A when
pure
at the
temperature
of the solution
XA =
Note
mole
that Raoult's
fraction of
which may be quite
partial pressure
from
different
The separation of components with
evaporation/distillation and condensation
and processing operations.
Gases dissolved
in
Raoult's law allows the calculation of
phase on the basis of the composition of the liquid.
on the other hand, defines the
the gas phase
in the solution
law differs from Dalton's law.
partial pressures in the gas
law,
component A
in liquids:
that
of the liquid phase.
different vapor pressures through repeated
is
This technique
Dalton's
on the basis of the composition of
is
achieved
in a
a practical
Henry's law.
number of
industrial waste
example of Raoult's
Many
situations
law.
encountered
environmental science and engineering involve the transfer of gases into and out of
liquids.
from the
For example, the aeration of rivers and lakes involves the transfer of oxygen
air to the water, thus
many forms of
aquatic
life.
The
supplying the dissolved oxygen essential for
aeration of waters and wastewaters to
fish
and
remove odorous
gases and the aeration of wastewater for biological oxidation are other examples.
The degree of
solubility of a gas in a liquid
depends on the kind of gas
nature of the solvent liquid, the pressure, and the temperature.
The
it
is,
the
solvent liquid in
176
Physics and Chemistry
many environmental
is
NH
and He.
.
2
applications will be water.
on the other hand,
.
3
For example,
important.
N2
2
,
alcohol) than in water, whereas
is
and
,
H2 S
and
Slightly soluble gases include
The nature of
a very soluble gas.
C0 2
NH
are
3
Chapter 6
are
N2 H2
,
,
the solvent
much more soluble in alcohol (ethyl
much more soluble in water than in
alcohol.
Many
of the solutions occurring in the environmental field are very dilute mix-
Henry's law
tures.
is
a special case of Raoult's law applied to dilute solutions.
which
solutions the partial pressure of the solute,
from
different
(i.e.,
that predicted
linearly related) to
Suppose
we
that
its
by Raoult's law, but
mole
fraction (Breck et
it
In such
may be
will nevertheless be proportional
1981).
al.,
are dealing with a solution of a small quantity of ideal gas
solvent A, as for example
ideal
present in small quantities,
is
oxygen dissolved
in
B
in
Then, mathematically,
water.
Henry's law can be expressed as
=XB K H (A,B)
PB
(6.45)
= partial pressure of the solute B in the gas
XB — mole fraction of B in the solution
Ktf(A,B) = K H = Henry's constant, which depends on
where P B
ute
B and
Quite often, Henry's law
the solvent
is
the properties of both the sol-
A
stated as
X B = K*H P B
which
is
is
same
the
as equation (6.45) except that
(6.46)
KH (A,B) =
1/
K*H
.
And sometimes
C B = KtfP B
where
(or
CB
is
(6.47)
the concentration of the gas dissolved in the liquid at equilibrium [in
mg/L)] and K*H*
know
to
looking up values for Henry's constant
which of the three equations the values apply.
Henry's constant
for a
is
also temperature dependent.
number of gases of importance
mL/L
and dimensionally different from K*H and
will be numerically
KH (A,B). When
to
it
stated as
in the
atures over the range normally encountered.
in
handbooks,
it
is
important
Table 6-2 provides values of
environmental
field
and
at
Values for other gases can be found
gineering handbooks, such as Perry (1984).
Through
KH
selected temperin
en-
the combination of Dalton's,
Raoult's, and Henry's laws, gas-liquid transfer problems at equilibrium can be solved.
Note carefully
that
Henry's law
calculation of the dissolved
certain temperature.
the dissolved
oxygen
concentration
in the
is
an equilibrium law.
oxygen equilibrium
If this river receives
in the water,
water.
For example,
from the
allows the
organic waste,
it
uses up a portion or
all
of
thereby creating an undersaturated dissolved oxygen
The magnitude of
the differential
concentration and the actual concentration will govern the rate
ferred
it
(saturation) concentration in a river at a
air to the river water.
between the equilibrium
at
which oxygen
This can be expressed mathematically as
is
trans-
(N
©'
5
NO
(N
ri
O^
<N
©
Q
LU
>
_l
O
©
**
vi
£ 2
—
©
VI
**
«N
o
rn*
oo
t~»
vO
cs
NO
m
o
©
o
©
ci
o
—
o
ri
On
r-.
U
0\
en
00
v>
^t
©
^o
o
©
•*
©
d
S<
On
t~-
©
©
X
c/3
V)
-
Q
6u
2
<N
CO
00
LU
to
<
00
©
©
o
o
so
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<
©
<n
—
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o>
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r^
en
rvi
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IT)
v>
r>
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>
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CO
IT)
LU
<*
CI
CD
V,
rTf
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<
"i
*
X
c
03
a
<o
a
or
2
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~o
©
ON
o
ON
IT)
•G
UJ
(\l
O
fN
t
00
t/3
D
_J
<
>
©
V,
©
r-
to
©
—
©
00
©
sO
©
fi
Oj
©
—
©
<N
00
t.
>/")*
.c
II
-^
fc!
t*5
"3
a.
'£
j2
i
(J
§
S:
(/I
CD
01
<
3
—
c\
©
&
C
\i
C
«J
X
-5
Q
to
177
178
Physics and Chemistry
—
The
Example
oc
C
(Cequi
oc
,
- Cactua[
(6.48)
)
kinetics of this gas-liquid transfer are not considered in this book.
6.13
Calculate the amount of dissolved oxygen (abbreviated
at
Chapter 6
20
C
and
at
OC
DO)
in
Assume
under saturated conditions.
mg/L
that
present in river water
atmospheric pressure
100 kPa.
Solution
From Table 6-2,
KH
=
4060
MPa
=
2580
MPa
20°C
KH
From equation
(6.45),
P 0n = X 0i
From equation
P
Kw (H
x
2
0,
2
)
(6.44),
=
0.209 x 100 kPa, since
=
20,900 Pa
20.9% oxygen
air contains
Therefore,
C X °2 =
20 90°
4060 x 10 6
At0CX °2
o =
2580 x 10 6
At 20
-
,
=
5.15 x 10- 6
and
The mass of oxygen
at
6
8.10 x 10
fraction of
'
„
each temperature
5.15 x 10- 6
The mass
20 90 °
2
=8.10x
10-"
is
mo!O
2
x 32 g/mol
=
1.65 x
mol
2
x 32 g/mol
=
2.59 x 10" 4 g
10- 4
gat20°C
at
is
1.65 x 10" 4
1.65 x 10" 4
+
=
9.2 x 10~ 6 at
=
14.4
20°C
18.0
and
2.59 x 1Q- 4
2.59 x 10" 4
+
18.0
x 10" 6 at0 o C
0C
is
179
Material Balances
Sec. 6.5
Therefore, the dissolved oxygen concentration
D0
1()
c
=
at the
two temperatures
9.2
mg/L (ppm)
14.4
mg/L (ppm)
is
and
DO
()
Note
that
creases
6.5
oxygen
is
=
c
a rather insoluble gas in water
and
that
an increase
in
temperature de-
solubility in water.
its
MATERIAL BALANCES
6.5.1 Concept of Material Balance
When
orate
rain falls,
some of
it
will evaporate directly into the
from the land and water surfaces back
atmosphere, more will evap-
atmosphere, a portion will be ab-
to the
sorbed by vegetation and transpirate back to the atmosphere, and the remainder will run
off directly to rivers and lakes or infiltrate into the groundwater, to eventually rejoin the
surface water.
This water system
is
Figure 6- 10a
called the hydrologic cycle.
is
a sim-
schematic diagram of the hydrologic cycle for a small land/lake region.
plified
number of separate "systems" can be
lake, (b) the land,
system.
An
and
(c) the lake
identified: (1) the
and land;
atmospheric clouds over
(2) the land; (3) the lake;
and
A
(a) the
(4) the entire
examination of Figure 6- 10b shows that the quantities of water crossing the
boundaries of each subsystem balance.
(For a similar water balance on a global basis,
see Figure 7-10.)
This example illustrates the law of conservation of matter.
In chemistry, scientists
have found that the sum of the weights of the substances entering into a reaction always
equals the
sum of
the weights of the products of the reaction.
The general concept of
the law of conservation of matter can be illustrated by three equations, applied to an en-
closed, isolated system.
First, there is
input
or,
simply stated, "What comes
If
in
=
must go
output
(6.49)
out."
material accumulates within the system, then
accumulation
Furthermore,
if
material
is
=
input
-
output
(6.50)
produced or consumed within the system, the most general
case can be described as
(rate of)
-I-
accumulation
(rate of)
where the parenthetical
rates,
and consumption
=
production
(rate of)
rates,
(rate of) input
—
(rate of)
—
(rate of) output
consumption
allows for changes with time
and therefore
in
(6.51)
in
flow rates, production
accumulation rates (Bird
et al.
1960).
180
Physics and Chemistry
60
I
J
\/
I
I
Rainfall
X^/^iver Land
Chapter 6
Rainfall
over Lake
Net Transfer
Atmosphere T
in
30.
Evapotranspiration
from Land
Direct Runoff
and from Groundwater
(a)
Atmospheric
Clouds over
Net Gain
from Clouds Net Loss to
over Lake
Land Clouds
4
l
30
Land
Evapotranspiration
from Land
30
Evapotranspiration
30
from Land
60
30
Rainfall to
(Net)
Evaporation
from Lake
Rainfall to
Evaporation 100
from Lake
Land
60
Atmospheric
Clouds over
Lake
Land
(Net)
30
70
100
Rainfall
to
70
Lake
Rainfall to
Lake
30
Land
Lake
Inflow from
Runoff
Runoff and
Groundwater
(b)
Figure 6-10
Hydrologic cycle
in
small
a
land/lake
region:
(a)
schematic of the
hydrologic cycle; (b) material balance on the hydrologic cycle.
Material balances, also often referred to as mass balances, are a very useful tool to
examine a process or
parts of a process.
They
are used extensively in chemical engi-
neering, and can be also very useful in the environmental
useful as a check on measurements of
to
measure
counting of
a process.
directly.
all
They
all
streams that
field.
may
be
Material balances are
difficult or
are also helpful in the design of a process
and
impossible
in the ac-
materials of production and consumption (including waste products) in
When
there
is
no accumulation
in a
system,
it
will
be called steady state.
181
Material Balances
Sec. 6.5
For the unsteady state, the
rate of
accumulation
is
The
changing with time.
or
rilling
emptying of a storage tank would be an example of an unsteady material balance.
The following
examples
illustrative
will
demonstrate applications of single material
balances.
Example
A
6.14: Settling of
Suspended Solids from Wastewater
used to remove suspended solids from wastewater.
settling tank is
wastewater into the tank
is
The removal
200 mg/L.
The
rate of flow
of
10 L/s, and the influent concentration of suspended solids (SS)
is
efficiency of the settling tank for suspended solids
is
60%.
Calculate the amount of suspended solids (sludge) accumulating in the sludge zone each
day.
be helpful to draw a diagram of the process and to mark
Solution
It
data on
as well as the
it.
Q ,=
C, =
will
10
unknown,
identified
known
the
all
by a question mark (Figure 6-11).
Us
Q e =10LVs
200 mg/L
C =?
Settling
>
Zone
~
Amount
System
Boundary
of
Sludge = ?
Longitudinal Section
Figure 6-11
Now, draw
the appropriate system boundaries
this case the
boundary
sumptions,
any are necessary.
if
around the
will be
In this
if
there
settling zone.
is
more than one system.
In
make
as-
To solve
the problem,
case a reasonable assumption
is
that the
amount of
water that will be withdrawn when pumping out the sludge from the sludge zone
small compared to the inflow of wastewater and can therefore be neglected.
The concentration
C.
=
C
.
t
100—
—
(removal efficiency)
C,
=
material to be balanced in this case
no accumulation of suspended
drawn the boundary. There
-,,„,
200
60
flOO
100
=
within the settling zone.
very
can easily be calculated:
100
The
is
Therefore,
is
the
200 x 0.40
=
mass of suspended
solids in the settling zone, the system
is
80 mg/L
solids.
around which
There
is
we have
also no production or consumption of suspended solids
Therefore, equation (6.49) applies, and
we
have:
182
Physics and Chemistry
Solids balance:
input
=
output,,,
+
effluen ,
output,,,
s|
Chapter 6
udge zone
or
output,,,
In solving
sumed
s , udge
=
zone
problems of material balances,
it
-
input
output m
helpful to use a fixed time interval or an as-
is
quantity of materials as a basis for calculations.
convenient time period to use.
input
SS
=
10 L/s x
=
172.8 kg/day
We
effluen ,
For
this
flow problems,
day
1
is
a
obtain
60 s/min x 60 min/h x 24 h/day x 200 mg/L x 10" 6 kg/mg
Similarly,
SS
output
=
in effluent
69.1 kg/day
Therefore,
output,,,
Example
An
S | udge
zone
=
—
172.8
69.1
=
103.7 kg/day
6.15: Dilution
industry discharges
The. major pollutant
its
liquid waste into a river that has a
waste
in the
is
stream has a flowrate of 0.1 m-Vs, and the concentration of
mg/L.
minimum
P
minimum
100 mg/L P
set a
occurs in the
Solution
maximum
river.
limit of
P
The waste
is 3000
in the river
The
flowrate conditions.
Assume
in the river.
P.
waste stream
in the
Upstream pollution has caused a concentration of 20 mg/L
of the industrial discharge under the
agency has
flowrate of 10 m-Vs.
a nonreactive organic material called
that
upstream
state regulatory
complete mixing
Will the industry be able to discharge the waste without treatment?
Figure 6-12
is
a diagram of the process for
minimum
flow conditions
in the
river.
A
material balance on
P
for an interval of
input
=
1
second
is,
output
or
Waste Stream,
Q
C
W
=0.1 m 3 /s
= 3000 mg/L
Q
=10.1
m 3/s
River +
River
Complete
Mixing
System
Boundary
Figure 6-12
Waste
Sec. 6.5
183
Material Balances
input u[ , slream nver 4- input wasle
10
m
3
=
x 10 3 L/m 3 x 20 mg/L
=
m3
10.1
outputj,, unslream nver
+
m3
0.1
x 10 3 L/m 3 x
Ce mg/L
200
+ 300=
x 10 3 L/m 3 x 3000 mg/L
so
10.1
Ce
or
Ce
Therefore, no treatment
=
m
= 495
mg/L
required.
is
6.5.2 Guidelines for Making Material Balances
A
few general guidelines for solving problems can be stated as follows (adapted from
Himmelblau, 1982):
1.
Draw
2.
Calculate
a diagram or flowchart of the process.
all
mined from
weights, flowrates, concentrations, and so on, which can be deterthe information provided without
3.
Show
4.
Give appropriate symbols
all
known
making balances.
data (flowrates, concentrations, etc.) on the diagram.
to
any unknown quantities, and indicate each unknown
by a question mark.
5.
Select a convenient basis on
which
suitable time interval, such as a
such as 100 kg or
1
to carry out all calculations, for
example, a
day or a second, or a fixed quantity of material
lb.
6. Select the appropriate
system boundaries for the material balance(s) to be made.
Choose boundaries
such a way that calculations are kept as simple as possible.
7.
in
Write the material balances.
These may include a balance on the
algebra
we know
that
we must have
as
total material
equations as
From
we have
problem simpler.
Experi-
and a balance for each of the component materials involved
many independent
in the
problem.
unknowns.
8.
Make
assumptions,
if
any are necessary,
ence will be required to do
The following examples
make
the
will provide practice in solving problems.
problems on material balances are given
later
that
this wisely.
at the
Additional
end of the chapter, and several occur
chapters where such problems are appropriate.
in
184
Chapter 6
Physics and Chemistry
6.5.3 Examples of Material Balances
Example 6.16
The sludge removed from the sludge zone of the settling tank in Example 6.14 has a solids
concentration of 3%. To be able to burn the sludge in an incinerator, it must be dewatered.
This
to be carried out
is
8%, and then
tion of
move 75%
by a gravity thickener which can achieve an underflow concentra-
vacuum filter that will reThe density of wet sludge is approximately
the sludge will be concentrated further in a
of the water from the feed stream.
equal to that of water.
by the vacuum
Calculate (a) the flowrate of thickened sludge that must be handled
and (b) the composition of the
filter,
cake produced by the vacuum
filter
fil-
ter.
The process can be broken
Solution
drawn showing
all
Qe (Returned
C.
=
into
its
two components, and a diagram can be
data and system boundaries (Figure 6-13).
to
Waste
Treatment Plant)
3%
Filtrate
to
Returned
Waste Treatment
Plant
Ce = 0%
Filter
Cake
(Assumed)
System
Boundary
I
System
Boundary
|
Thickened Sludge (8%)
Q..
I
C.
=
.
8%
Vacuum
Thickener
Filter
Figure 6-13
Thickener.
(a)
of solids
at
The
rate of flow Q, associated with the
a concentration of
3%
103.7 kg/day x IP*
1
Q,=
=
Qi
is
that
thus
Q =
,
c
withdrawal of 103.7 kg/day
is
mg/kg
86,400 s/day x 30,000 mg/L
0.040 L/s
0.4% of the inflow to the settling tank (10 L/s), which shows
Q, made in Example 6.14 was reasonable. Similarly,
Q«
=
that
assumption
mg/kg
86,400 s/day x 80,000 mg/L
=
Note
103.7 kg/day x 10 h
that the
0.015 L/s
we have assumed
that all the solids settle to the
and hence the effluent concentration
C ~
.
(
0.
This
may
bottom of the thickener,
not always be a
good assumption.
Sec. 6.5
185
Material Balances
Ce
but certainly
<5C
Therefore, this part of the question can be answered without
C„.
mak-
ing a material balance.
(b)
sume
Vacuum
filter.
Choose
kg of thickened sludge as a basis for calculation. As-
1
amount of solids in the filtrate
shown in the boxes in Figure 6-14.
that the
streams
is
H2
= 0.92
U
Vacuum
*[
Filter
the three
Solids = ?
\\
//
t
H2
/
y/
\V
\v^
Thickened
Sludge
The composition of
O
/>
Solids = 0.08
negligible.
is
Filter
= ?
Cake
Solids =
(Assumed)
H 2 = 0.69
Filtrate
(75%
of
Water Removed)
Figure 6-14
We
have
H2
The
final
removed
amount of
=
solids in the filter cake
in
—
removal
0.92
The composition of
0.75 x 0.92
-
the filter cake
0.69
is
=
is
0.69 kg/kg thickened sludge
0.08 kg, and the associated water
=
remainder
=
0.23 kg
%
Solids
0.08
25.8
H2
0.23
74.2
0.31
100.0
Total
Note
that
although the
filter
H2
as follows:
kg
cake
a piece of wet felt and cannot be
is
still
contains about
pumped.
It is
75%
water,
it
has the consistency of
therefore transported by a conveyor belt to
a storage/loading area.
Example
6.17: Sludge
Drying
The filter cake from Example 6.16 is fed to a rotary kiln dryer. After 500 kg of water
removed in the dying operation, the dried sludge is found to contain 30% water. What
the weight of the
Solution
A
filter
cake fed to the dryer?
diagram of the process
is
shown
in
Figure 6-15.
is
is
.
186
Physics and Chemistry
Chapter 6
System Boundary
Filter
Cake (FC)
- Dried Sludge (DS)
Dryer
Solids = 0.258
Solids = 0.70
H 2 Q = 0.742
H2
= 0.30
Water Removed W)
500 kg
(
Figure 6-15
Choose 500 kg of water removed
(solids
and water)
is
input
=
solids balance
the total material balance
output
W=
FC = DS +
The
Then
as a basis for calculation.
given by
DS + 500
kg
is
0.258
FC =
DS
0.70
or
——
0.258
DS =
FC =
0.369
FC
Substituting into the total materials balance gives
FC =
A
6.18:
FC + 500 kg
FC =500
0.631
Example
0.369
FC =
ol7 =
DS =
292 kg
792k s
Mixing with Accumulation*
mixing tank contains 30
ft
3
A
of water.
waste stream containing 2
flows into the tank at a flowrate of 3 ft-Vmin.
ft
3
/min.
Assume
that the tank in
completely mixed
to the tank concentration of pollutant A).
when
the tank contains
'Adapted from
a similar
50
ft
3
of solution.
p.
1
1
(i.e.,
3
of pollutant
at
that the pollutant
Jeffreys,
is
A
A
a rate of
the effluent concentration
Calculate the concentration of
Assume
problem by V.G. Jenson and G.V.
Engineering (New York: Academic Press, 1963),
lb/ft
Liquid flows from the tank
is
I
equal
in the effluent
nonreactive.
Mathematical Methods
in
Chemical
Sec. 6.5
187
Material Balances
This problem involves the accumulation of water and pollutant
Solution
diagram of the process
= 3
C
ft
= 2
of
3
made, showing
is
/min
lb/ft
oe
-
all
data (Figure 6-16).
It
is
A
in the tank.
A
an unsteady case.
:1ff
3
A
<
F
\/
= 50
ft
3
f
ce =?
c,=
V = 30
c
ft
3
= o
Completely Mixed
Tank
Figure 6-16
Accumulation of water. The
- Qe =
Q,
=
so the time to reach V,
50
ft
/
=
3
3
accumulation of liquid
-
=
1
tank
in the
is
2 ft-Vmin
is
V„
-
Qi
0.
rate of
-
50
30
10 min
- Qe
Accumulation of pollutant A. Initially, there is no pollutant
unknown concentration of A is given by C
After 10 min. the
]()
Then
linear variation occurs with time in the concentration of A.
A
in the tank,
= Ce
.
so
Assume
a material balance
C =
()
that a
on
A
can be made over the time period of 10 min as follow:
in
[Q, x t)C, -((?,/)
- out
C 10 -
accumulation
=
v,„ x
Q
=
2
x
(3
10)
x 2
-
(1
x 10)
C 10 -0
50 x C|„
i
60-5C,„ = 50
C,
A
more
=
I?
x
109
C 10
lb/ft
3
detailed treatment, not assuming a linear increase in the concentration of A.
can be made as follows.
effluent/tank. C,
ties
=
Cm
(lb/ft
,
(.
Let both the volume
Wt
be a function of time,
of the system at times
/
and
t
+
dt
/
3
),
and the pollutant concentration
(min).
A
can be made thus:
systematic listing of
all
in the
proper-
188
Physics and Chemistry
Properties of the system
Input rate of
A
Output
= Qn
= C
= Qe
= Ce
= V
= VCe
(ftVmin)
A
Input concentration of
(lb/ft
3
)
(ftVmin)
rate of solution
Output concentration of A (lb/ft 3 )
Volume of liquid in tank (ft 3 )
Content of A in tank (lb)
Volume balance over time
At
t:
=
3
=2
=1
= f(t)
= f(t)
=/(/)
interval dt:
—
input
=
output
._,
,_,
accumulation
—
dV
=
7>dt- \dt
J
dt
dt
or
dt
Pollutant
A
balance over time interval
input
-
3x2*By
dt:
output
=
\Ce
=
dt
accumulation
e
dt
.
dt
simplification
6
Substituting for dV/dt
=
2 and
_
Ce
= Ce
V = 30 +
dC
- + V^
dV
2/
and rearranging gives
dCe
- 3Ce
6
e
dt
30
+ It
Integrating yields
where
i
- 3Ce ) =
ln(6
ln(30
I
+
/ is the integration constant.
Now we know
that at
t
=
Ce =
0,
-
!
0; therefore,
In6
=
I
ln30
+
/
whence
/
By
substituting
and combining, we
= -
|
ln6
find that
-
i
ln30
2t)
+
I
Chapter 6
Sec. 6.6
189
Reaction Kinetics and Reactors
—
ln(
-0.5CJ =
I
I
1
ln(l
+0.067/)
-0.5Ce =(1 +0.067r)" 3/2
Ce =2-2(1 +0.067O" 3/2
Note
that the
assumption of a linear increase
not quite correct, since for
not a linear assumption
is
/
=
10 min.
Ce =
2
—
concentration of pollutant
in the
2 x 1.67 _3/2
=
1.07 lb/ft 3
A
is
Whether or
.
depends on the accuracy of the data and the use of the
justified
Often, complex problems can be greatly simplified by making certain assumptions.
results.
Whether
to
do so and what assumptions
to
make depends on
the experience of the engineer
or the scientist.
In
dium, the
examples so
the material balance
pollutant has been involved.
rate of
In practice,
far,
many
change being described by a
neither production nor consumption of a
pollutants will undergo change in the
rate equation.
This topic
Section 6.6, and a material balance problem with chemical reaction
6.6
is
is
me-
introduced
in
illustrated there.
REACTION KINETICS AND REACTORS
6.6.1 Reaction Kinetics
Not
chemical reactions reach equilibrium quickly.
all
are called kinetic reactions.
There are many cases
a reaction of a pollutant or other substance in a
amples
Reactions that are time dependent
in the
medium
environmental
is
field in
time dependent.
which
Some
ex-
are:
•
The removal of organic matter
•
The growth of biological masses
•
Radioactive decay
•
Chemical disinfection
•
Gas-water
•
Industrial waste reactions
in
water
transfer
Reaction kinetics can be defined as the study of the effects of temperature, pressure,
and concentration on the
rate
of a chemical reaction.
kinetics presented here can be
The
brief introduction to reaction
supplemented by reference to Levenspiel (1972) or sim-
ilar texts.
The rate of reaction, rh is a term used to describe the rate of formation or disappearance of a substance (or chemical species). Reactions such as biological oxidation
and disinfection, which occur within a single phase
called
homogeneous
reactions.
Those
like ion
(i.e.,
liquid, solid, or gaseous), are
exchange and adsorption, which occur
at
surfaces between phases (the solid-water or air-water interface) are referred to as het-
erogeneous reactions.
There are other classifications between homogeneous and heter-
ogeneous systems and those where
are the
most
common
and
will be
a catalyst affect the rate, but
emphasized
here.
homogeneous
reactions
)
190
Physics and Chemistry
Chapter 6
For homogeneous reactions,
=
r,-
——
—
moles
unit
volume x
—
moles (or mass)
(or
mass)
;
:
:
,„ _-.
(6.52)
;
unit time
For heterogeneous reactions,
=
r,
The sign convention
;
tion (/) of temperature (T)
The
., ._.
(6.53)
x unit time
positive (+) for the formation of a substance
is
The
for the disappearance of a substance.
tant(s).
——
:
;
unit surface
rate at
and negative
which these reactions occur
is
(
—
a func-
and pressure (P) and also of the concentration of the reac-
rate relation is therefore,
=f(T P [Al\B],-)
ri
(6.54)
1
l
Usually, the temperature (T) and pressure (P) effects are separated from the effects of
the concentration; therefore,
rt
where
mean
A
is
l
[B],
(6.55)
•••)
the rate constant, normally a function of temperature only, and
"function of
Assuming
how
= kf (T,P); MIA],
and
f
x
f2
(•)."
that the pressure
the concentration of one or
and temperature are kept constant, we can examine
more of
For the
the reactants affects the reaction rate.
stoichiometric equation
ah + bB
where
a, b,
rate
equation
rA
[A], [B],
is
and
B
=-
&[A] a [B]P
= k[CV
(6.57)
(3, and y are empiriand B are disappearing while
The negative
sign indicates that
A
increasing.
The order of reaction
a +
A
is
and [C] are the respective concentrations and a,
cally found exponents.
C
(6.56)
and c are the stoichiometric equation coefficients for the reactants
and the product C, the
where
-* cC
is
defined as the
p\ and the order with respect to reactant
The exponents
occur.
In
are often
many
whole numbers
sum
A
(i.e., 0,
cases, reactions will be zero,
is
of the empirically found exponents
a, to
1,2,
first,
B
etc.),
is
p, and to product
C
is y.
but fractional exponents also
or second order.
Expressed mathe-
matically,
rA
= —k
zero-order reaction
(6.58)
rA
= — k[A]
first-order reaction
(6.59)
rA
= — k[A
second-order reaction
(6.60)
rA
= — k[A][B]
second-order reaction
(6.61)
2
]
Sec. 6.6
A
191
Reaction Kinetics and Reactors
more complex example
is
*[A]
(6.62)
+ k[A]
•
At a low concentration of
reaction reduces to
•
A
Equation (6.62)
rate is
end of the reaction),
A:[A]
<5C
1;
therefore, the
A
(at the
beginning of the reaction), A[A] ^>
1;
there-
reduces to zero order.
is
an example of a saturation reaction, which
environmental problems.
where the
(at the
order.
At a high concentration of
fore, the reaction
in
first
It
has a
maximum
rate near the
is
quite
common
beginning of the reaction,
independent of the concentration of the reactant(s), and then decreases
becomes limiting.
Figure 6-17 is a graphical representation showing how
as a reactant
the reaction rate r(d\A]/dt)
varies with time for different orders of reaction.
CO
cr
c
o
o
03
Time,
Figure 6-17
Graphical representation of rate equations.
Types of reactions.
occurring
in a
single step
t
Elementary reactions
where
are defined as those reactions
the stoichiometric equation represents not just a
mass
—
a, b
balance but also what actually happens on a molecular scale.
=
(3,
and c
=
y,
and the
rate
In these cases,
equation can be written from stoichiometry.
mentary reaction of equation (6.56), the
rate
equation becomes
a
For the ele-
192
Physics and Chemistry
r= -
k[A}" [B] h
= k[CY
rate of reaction (and the rates of r A
and the overall
Chapter 6
rB
,
,
(6.63)
A
rc for reactants
and B and
product C) are
r
r=—a = ^b = -cc
'"a
'"b
(6.64)
With nonelementary reactions there
ric
equation and the reaction
rate.
It is
is no direct relation between the stoichiometassumed that a series of elementary reactions is
taking place, and consequently, rate constants must be determined experimentally.
Elementary reactions
in the
environmental
field
may
be single, as in
A
—
C
(6.65)
->
B -> C
(6.66)
or multiple, as in
A
and either type may be reversible.
For example, for the elementary, multiple,
irreversi-
ble reaction
aA
—U
bB
—
->
cC
(6.67)
the rates of reaction are
r,
=
= -|*
-±
a
(6.68a)
b
r2
B2
=—
= -p
rA
=
ar
rB
=
&r,
rc
=
cr 2
b
(6.68b)
c
and
(6.69a)
]
+
br2
(6.69b)
(6.69c)
Example 6.19
(a)
A
reaction has the stoichiometric equation
A
->
C +
D.
What
is its
order of reac-
tion?
(b)
If
it
is
known
that the reaction
action with respect to
is
elementary and irreversible, what
is
the order of re-
A?
Solution
(a)
The question cannot be answered,
mentary and
(b)
;
A
= — )t[A].
since
it
is
not stated whether the reaction
irreversible.
Therefore, the reaction
is first
order.
is
ele-
193
Reaction Kinetics and Reactors
Sec. 6.6
Example 6.20
An
elementary irreversible reaction has the stoichiometric equation
culate the rates of formation and disappearance of the three
their relationship to
2A +
'
B —
C.
Cal-
components of the reaction and
one another.
Solution
From stoichiometry we know
rA
= -MAp[B]i /2
rB
=-k
2
[A} 2 [B)
rc
=+*
3
[A] 2 [B]" 2
m
that
-i
-2
+1
Therefore.
t =-[
rA
=
-2rB
or
fc,
=
J =
2* 2
on reaction rate constant.
Effect of temperature
It
has been found
experimentally that most reaction rates increase with increasing temperature, as shown
in
Figure 6-1 8a doubling (approximately) for a 10°C increase
at
plot of In k against \IT (Figure 6-1 8(b)) provides a straight line
reaction rates at different temperatures.
dOn
k)
=
Ea =
.
,
...
Ea
and
universal gas constant
temperature (K)
R
=
Ea
—
R
,, -,„
(6.70)
Arrhenius activity energy
T =
=
.
constant (slope of line)
R =
k
A
Therefore,
d( \IT)
where
lower temperature.
and a means to predict
reaction rate constant (various units)
have
to
have consistent
units.
Equation (6.70) can be integrated to give
k
where A
is
is
(5 71,
the van't Hoff-Arrhenius coefficient, in appropriate units.
Equation (6.71)
It
_ Ae (-EalRT)
is
known
as the
often convenient to rearrange
it
as
Arrhenius temperature-dependence equation.
194
Physics and Chemistry
Chapter 6
o
o
re
0)
cr
Absolute Temperature,
T
1/7
(a)
Figure 6-18
(b)
Effect of temperature on reaction rate constant:
(a)
rate
of reaction versus absolute
temperature; (b) natural logarithm of reaction rate constant versus reciprocal of absolute temperature.
*2
-=
to facilitate
/
(e
comparison of the reaction
EalRTJ^Ji-T.
i
rate constants at
mental engineering the range of temperatures
approximately constant.
EalRT Ti =
Let e
9, where 9
\
can be rearranged
is
is
is
two temperatures.
In environ-
usually small, so the product
the temperature coefficient.
T2 T
Then equation
x
is
(6.72)
to yield
k,
Equation (6.73)
(6.72)
-)
=
»(T,-r,)
(6.73)
*,
frequently used in both biochemical reactions and physicochemical
reactions for easy calculation of temperature effects, provided that information on 9
is
available.
Example
6.21
The
rate of
growth of a biochemical system
constant & 2 o-
Solution
Calculate the relative rate
From equation
(6.73), & 30
the rate for a 10'C temperature rise.
=
at
at a
30°C
^20
temperature of 20°C has the reaction rate
if
1
the temperature coefficient
7 2<3o-20)
_
2 jt20
,
that
is,
=
1.072.
a doubling of
195
Reaction Kinetics and Reactors
Sec. 6.6
6.6.2 Types of Reactors
A number
of physical (sedimentation, nitration, equalization,
tion, etc.)
etc.),
chemical (precipita-
and biochemical (activated sludge, anaerobic diges-
tion, coagulation, softening, etc.),
treatment methods are used
ture occurs within a tank, the tank
is
environmental engineering
in the
When
generally carried out within tanks.
field.
They
are
a reaction of a chemical or biochemical na-
usually referred to as reactor.
Reactors can generally be divided into two types: batch reactors and flow reactors.
In a batch reactor, the materials are
added
is
removed from
the tank.
Because the material
composition within the reactor
uniform
is
at
tank
in the
is
left
normally well mixed, the
However, as the reac-
any instant of time.
A
composition changes with time.
tion proceeds, the
mixed, and
to the tank, thoroughly
At the end of the given time, the mixture
for a sufficient time for the reaction to occur.
batch reaction
therefore re-
is
ferred to as an unsteady-state operation.
and out of the
In a flow reactor, material flows into, through,
on the mixing conditions and flow patterns within the tank,
reactor.
we speak
Depending
of ideal and real
reactors.
Figure 6-19 shows the spectrum of flow reactors, with an ideal reactor at
each end.
The
ideal reactor of part (a)
is
called a plug flow tubular reactor (PFTR),
or sometimes just a plus> flow, piston flow, or tubular flow reactor.
within the tank
is
tank and are discharged
remain
in the
That
characterized as uniform.
in the
same sequence
may
There
not be
is
no mixing of the
some
lateral
when water
The particles
The situation is
mixing. The operation can be steady,
stant with time, or unsteady, if
flows through a garden
fluid in a longitudinal direction,
it
of flow reactors (Figure 6- 19c)
changes with time.
is
pattern
that they entered the tank.
tank for a period equal to the theoretical detention time.
equivalent to forcing a fluid through a long tube, as
hose.
The flow
the fluid particles pass through the
is,
the other ideal
if
although there
may
the rate of flow
is
or
con-
At the other end of the spectrum
flow reactor, called a completely
stirred tank reactor (CSTR), or sometimes just a stirred tank or backmix reactor.
It
has the characteristic that the contents of the tank are so completely mixed that the
composition
same
is
uniform throughout.
Therefore, the composition of the effluent
thereby flow patterns) which
mixing).
Some
fall
ideal flow reactors.
PFTR
between the
real flow reactors
the
CSTR
(no mixing) and
(complete
can be approximated by one or the other of the two
In other cases correction factors
developed for reactions occurring
is
Real flow reactors have mixing conditions (and
as that of liquid in the tank.
in ideal
reactors,
have to be applied to the solutions
which are simpler
to
develop than
for real reactors.
A
comparison of the batch. PFTR, and
CSTR
reactors
is
made
in
Table 6-3.
In
an industrial operation that produces various waste products of relatively small quantity
but perhaps high strength, a batch operation for the treatment of waste
It
allows intermittent operation whenever there
and may allow easy change from one waste
is
to another.
plating industry, or in certain operations of the textile industry, are
batch treatment
On
is
used.
the other hand,
Certainly
it
is
may
be useful.
volume of waste produced
Waste treatment in the metal
a sufficient
examples where
untrue that batch operations are old fashioned.
where waste streams are large and being produced continuously,
a
196
Physics and Chemistry
Feed
Product
In
Out
Chapter 6
Feed
(a)
PFTR
Feed
In
Varying
Conditions
of Mixing and
Flow Pattern
(b)
REAL REACTOR
Product
Out
Product
Out
(c)
Figure 6-19
CSTR
Flow
reactors:
(a)
plug flow tubular reactor (ideal reactor); (b) real
reactor; (c) completely stirred tank reactor (ideal reactor).
much more
Examples include municipal waste treatment of doAnother variation, called a semibatch reactor, is
used when intermittent feed to a reactor with long detention time occurs. An example
of this is the anaerobic digestion of sewage sludges in a municipal waste treatment plant
flow reactor
is
sensible.
mestic and liquid industrial waste.
(see Chapter 12).
Detention time. In a PFTR, by definition, each fluid particle spends exactly
same amount of time flowing through the reactor. This flow-through time is generally called the detention time. For a PFTR, the detention time for each particle can
the
be obtained from the equation
/
where
=
V=
detention time,
t
q
volume of
=
=
(6.74)
[t]
liquid in the ideal reactor, [L 3 ]
volumetric flowrate of feed (inflow) q
[L] indicates dimensions of length
or product (effluent) qj, [L 3 /t] and
For liquids, q = qe, but with gases there may be a volume change, and q
equal to q t
In this case, q^ should be used to calculate detention time.
.
may
not be
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197
198
Physics and Chemistry
CSTR some
For a
may move
fluid particles
through the reactor in a
or longer time than the average detention time, but the latter can
still
Chapter 6
much
shorter
be calculated from
equation (6.74).
Nonideal flow and tracer studies.
have
like the
two
most
In practice,
real tanks
do not be-
Deviations from the ideal pattern occur as a result
ideal flow reactors.
of (1) "channeling" of parts of the liquid through the reactor because of density differ-
ences caused by temperature variations; (2) short circuiting, perhaps because of uneven
weir outlet elevations; (3) the existence of stagnant regions, and (4) dispersion caused
by turbulence and
tention time
Because of these deviations, the effective average de-
local mixing.
others
still
Some
less than that calculated for the ideal reactor.
is
may
flow through the tank very quickly, others
may
fluid particles
may
take several average detention times, and
reach stagnant or "dead volume" regimes, thereby reducing the useful
volume of the tank. To obtain a complete picture of the flow of fluid in the tank, velocities would have to be measured throughout the tank. This is a very time-consuming
A
task.
time
less
arduous task
remains
f
to find out
is
A
at a later time.
how much
of the fluid that was in the tank
A
residence time distribution of the flow through the tank.
nonreactive material
at the outlet
introduced into the
is
inlet to the
Two common methods
of the tank.
at
technique using tracers can provide a picture of the
dye, salt solution, or other
tank and monitored continuously
of introducing tracers are the follow-
ing:
•
Continuous input:
•
A
C
concentration of
tracer
Pulse input: All the tracer
so that the
is
until the
is
put into the inlet continuously to provide a tracer
end of the experiment: also called step
dumped
concentration
initial
C
input.
into the inlet in as short a time as possible
in the reactor
=
Q/V, the quantity of tracer
added/reactor volume: also called slug input.
The response of
6-20.
In both cases
Suppose
actor
uid
is
the outlet in each of the
is
white.
added
stream,
C
that red
at
making
is
used as a tracer and that the
In the case of a
it
for a real reactor
is
shown
in
Some
slightly pink.
continuous input,
at
time
/
flowing through the re-
fluid
=
a steady flow of red liq-
red particles will flow in a very short time to the outlet
As time goes
on, the outlet stream will
become
pinker until a steady color of pink appears in the outlet, the degree of which
mined by
the relative flow
volumes of white and red
at the outlet,
but since
all
and then begin
Example
in the
at the outlet will
to fade until eventually the liquid will
deter-
continuous case
of the red liquid would have been
once, with no further additions, the color
steadily
is
liquid.
For the pulse input, the same early appearance of pink as
would occur
Figure
the concentration of tracer in the outlet stream.
is
dye
the inlet.
two cases
be
dumped
in at
reach a peak intensity of pink
all
white again.
6.22
Describe mathematically the response
tracer input to the inlet of a
at
CSTR. The
the reactor outlet to a continuous
volumetric flow rate
is q.
nonreactive
199
Reaction Kinetics and Reactors
Sec. 6.6
Tracer
Concentration
Time,
(a)
Tracer
Concentration
Input Signal
Output Signal
(/
curve)
Time, 6
(b)
Figure 6-20
put.
=
(
ical
C/C =
(j
Reactor outlet response to
inlet tracer: (a)
proportion of tracer in the outlet stream
for a pulse input.
detention time.
Time 9 (dimcnsionless)
=
continuous input; (b) pulse
= F
for continuous input
tit, the actual
in-
and
detention time/theoret-
200
Physics and Chemistry
Chapter 6
Solution
C =
C =
By
concentration of tracer in continuous input
concentration of tracer in tank (and in outlet stream of a
CSTR)
a material balance on the tracer,
input
gC
=
output
+
accumulation
=qC+j (VC)
t
Dividing by
qC
{)
,
we
obtain
'
From
=#
C + -*
q
J,
dt
7T
C
before
C
^Q)
and since 8
=
tit
V
- =
=F
(see Figure 6-20),
_-!
_L
dd~*
(By convention, we
t
q
call the
response
the response to a pulse input, a d
dt
at the outlet to
a continuous input an
F
curve, and
curve.) Therefore,
1=F+^
dQ
1
dF
F
ln(l
-
F)
or
F=
In a
to a
manner
CSTR,
similar to that of
Example
the response at the outlet
If the
proportion
F
or
d
-
6.22,
«•
e
it
can be shown that for a pulse input
is
=
/
1
e~
of tracer present in the effluent
of tracer remaining in the tank can be determined.
outlet will be identical to the input, delayed
and outlet concentrations are identical by
is
known,
by the detention time
definition.
the proportion
For a PFTR, the response
~t
.
For a
at the
CSTR,
inlet
Figure 6-2
and
provides information for a
1
curves for tracer inputs.
<
201
Reaction Kinetics and Reactors
Sec. 6.6
sometimes given
PFTR, CSTR, and
to these curves.
For example,
/
may
bution.
age
F or
C7C
occur frequently
may be
referred
in the literature, they tend
earlier, reactors deviate
from the flow regime of
These models are discussed further
either a
PFTR
PFTR
in
Levenspiel (1972).
General Case
CSTR
~L
-»
Age
(•
various mathematical and physical models have been developed to ap-
proximate nonideal behavior.
Internal
F,
and have therefore not been used here.
For reasons stated
CSTR, and
/,
distribution, output tracer distribution, or output residence time distri-
Although such expressions for
to be confusing
or
on the
be called the age distribution of
molecules within the tanks, or residence time distribution, while
to as effluent
real reactor
Various names other than fraction of tracer present are
y
-»
&
Distribution
Max. Slope
0=0.5
1
d
Continuous Input
Pulse Input
A
Area = 1 „
Width -0
Figure 6-21
/,
F, and
Levenspiel (1972).
6
curves for various reactor types.
Source:
Adapted from
202
Physics and Chemistry
Typical tracer studies.
ance of three primary
shows
figure
the
The use of
The
Ontario, sewage treatment plants.
tained
from
considered
at the
6-22 and Table 6-4.
Windsor, Sarnia, and
CCIW
The
(Burlington),
table lists the hydraulic efficiency parameters ob-
curves under various flow conditions expressed as an overflow rate.
d
concept of overflow
is
tracer studies to evaluate the perform-
settling tanks is illustrated in Figure
curves for the tanks
<>
Chapter 6
in
of the inflow
rate, i.e., the ratio
Q
(The
to the surface area of the tank,
Section 12.5.2)
ZA
Windsor r
\
2.0
CCIW
\
1.6
8
c
'
Sarnia
I
.2
re
1.2
c
CD
o
c
o
O
0.8
iS
CD
CE
0.4
I
I
i
I
0.5
1.0
1.5
2.0
Relative Time, tIT
Figure 6-22
CCIW
Typical
(Burlington),
<
curves for the primary sedimentation tanks
Ontario,
sewage treatment
M. A. Qazi, Journal of the Water
The hydraulic
detention time
t
g
plants.
Source:
at
G. W.
the Windsor, Sarnia.
Heinke. A.
J.
Pollution Control Federation, 52 (1980): 2946.
efficiency of a tank can be defined as the ratio of the actual
to the theoretical detention time
ideal settling tank, this ratio will
always be considerably
and
and
Tay.
T
be unity (or 100%).
less than unity
expressed as a percent.
For an actual
mean
For the
settling tank,
it
will
because of the presence of stagnant zones within
The efficiency of the tank at Sarnia (about 73%) is much higher than it is at
Windsor (30 to 42%). Also, the time to the initial appearance of the tracer and to the
peak concentration occurs much earlier at Windsor than at Sarnia, indicating that severe
the tank.
short circuiting occurs at Windsor.
The hydraulic parameters
tween those of Windsor and Sarnia.
It
at
the
CCIW
plant
fall
be-
can be concluded, supported by the suspended
Sec. 6.6
203
Reaction Kinetics and Reactors
TABLE 6-4 HYDRAULIC EFFICIENCY PARAMETERS
FOR WINDSOR, SARNIA. AND CCIW (BURLINGTON),
ONTARIO, PRIMARY SEDIMENTATION TANKS
Hydraulic efficiency
Overflow
parameters a (min)
rate
(mVirr
day)
t,
V
h
T
t
K
m
c/c)
Sarnia
36
29
48
79
110
72
49
24
39
59
80
74
73
19
31
39
53
73
98
16
25
29
40
73
24
20
46
60
200
30
49
10
25
33
100
33
73
7
18
27
67
40
98
5
15
21
50
42
38
Windsor
CCIW
29
8
28
42
110
49
5
25
36
66
55
73
5
20
30
50
64
98
5
16
24
33
73
Where
/,
=
time interval for
initial
detection of the tracer in the
effluent (min)
t
p
=
time interval to reach peak concentration of tracer
in
effluent (min)
f.
=
actual
mean
detention time (centroid of the
(
curve)
(min)
T
=
theoretical detention time (min)
G. W. Heinke, A. J. Tay. and M. A. Qa/i, Journal oj the
Water Pollution Control federation 52 (1980): 2946.
Sonne:
solids removal data, that the Sarnia plant has a very efficient settling tank,
Windsor
whereas the
plant provides poor removal of suspended solids.
6.6.3 Determination of Reaction Rates
To develop expressions
for the rates of
plant experiments are conducted.
of the
The
—
— laboratory
chemical or biochemical reactions
determine the order of a reaction and the reaction rate constants
objective
is
to
that
is,
to
or pilot
develop data on the concentration
reactants and/or products versus time for a batch reactor or versus flowrate
(which amounts
to a time scale) for a
continuous-flow reactor.
Either a batch or a continuous system could be used, but batch reactors are
common
because they are simpler.
rate constants, the
Of
method of integration
the several
is
the most popular and
simplicity, only irreversible reactions involving
more
methods available for determining
one reactant
is
presented here.
will be considered.
For
204
Physics and Chemistry
By
integrating the rate equations [equations (6.58) to (6.61)] for zero-,
=
second-order reactions from [A]
[A
at
]
time
t
=
to [A]
obtain expressions that can be plotted as a straight line
The
shown
results for an ideal flow reactor are
in
if
=
[A]
we choose
time
at
Chapter 6
first-,
and
=
we
t
t,
suitable ordinates.
Table 6-5.
TABLE 6-5 PLOTTING PROCEDURE TO DETERMINE ORDER OF REACTION
BY METHOD OF INTEGRATION FOR A PFTR
Order
Rate
Linear
Integrated equation
equation
Slope
Intercept
-k
[Ao]
plot
[A]
-
[A„]
=
-fe
[A] vs.
t
dt
1
^
^
=
-Jfc[A]
"
dt
2
Note:
=
~ k[A]2
[A] indicates reactant
The data
A
-
ft
1
1
[A]
[A,,]
-
In
[A] vs.
-k
t
ln[A
(1 ]
1
vs -'
?
k
[A
Fa1
]
concentration.
method are obtained by measuring the decreasing reand calculating the rate constants for zero-, first-,
for the integration
actant concentration at various times
and second- order reactions.
We
engineering.)
fit.
(Higher-order reactions are not
common
in
environmental
could also plot the data to see which order of reaction gives the best
Example 6.23
illustrates the
procedure.
Example 6.23
The following data were obtained
for the reaction
A -» B +
reaction and the value of the reaction rate constant
t,
(min)
A. (mg/L)
Assume
Solution
90
Determine the order of the
C.
fe.
10
20
40
60
72
57
36
23
that the reaction is zero or first order.
The following
table gives the ap-
propriate calculations:
Zero order,
t
A
(min)
(mg/L)
First order,
InIM
[A]/[Ao]
[A„]
90
1.00
0.0
10
72
0.80
-0.223
20
57
0.63
-0.457
40
36
0.40
-0.916
60
23
0.26
-1.347
(mg/L
•
min)
+ 1.80
+ .65
+ 1.35
+ 1.12
1
(min
')
-0.0223
-0.0228
-0.0229
-0.0225
205
Reaction Kinetics and Reactors
Sec. 6.6
A
sample calculation
[A,„j-[A„1
37—
=
fto
rate
A,
much more
is
vals of time, the reaction
is
72
min
to 10
—w
=
- 90
is
as follows:
|Rn
=+1.80
,
= -0223 = _ 00223
InlAJ/tA,,]
^ =
Since the
from zero
tor the period
consistent than the k {) rate calculated for the various inter-
judged
to be
order and the average rate constant
first
=
k\
-0.0226.
We
It
could also have found
would then have been clear
versus
t
than on the graph of [A| versus
of the straight line
Note
y.
graphically by plotting [A] versus
A
that the data
—
is
Therefore,
first
order
is
t
and
In
[A] versus
on the graph of
selected,
In
t.
[A]
and the slope
jfcj.
that with the
can be determined.
/.
a straight line better
fit
If
method of
it
is
integration only
whole numbers of the exponents a,
(3.
desirable or necessary to determine fractional exponents, be-
cause the data appear to justify
it.
method of
the
differentiation (not described here)
must
For further information, see Levenspiel (1972).
be used.
6.6.4 Principles of Reactor Design
Reaction rate equations determined from an analysis of a batch reactor can provide a
basis for the design of a continuous-flow reactor.
If
sure drop through the reactor can be neglected, a
mass balance on
the temperature
change and presthe
change
in the
quantity of reactants relates the residence time, degree of reactant conversion, and the
reaction rate.
The
results will vary with the type of reactor
and the order of the reaction
taking place.
The general
material balance for any
component
A
in
an element of volume
in the
reactor will be
=
input
—
output
loss
(rate
(rate
of
A
of flow
(rate
=
into
the element)
of
A
of flow
of
—
out of
the element)
A
by reaction
+
accumulation
of loss
due to
(rate
of accumulation
/^ 75)
+ ofAinthe
chemical
element)
reaction in
the element)
The procedure
CSTR
at a
for a first-order reaction
steady state, reactant
and does not accumulate.
entire reactor,
A
A
is at
a
in
an ideal
CSTR
is
as follows.
In a
uniform concentration throughout the reactor
mass balance can therefore be made on reactant
A
over the
and equation (6.75) becomes
input
=
output
-
loss
by reaction
or
G[A
]
= G[A]-rA V
(6.76)
206
Physics and Chemistry
Q =
=
=
[A
[A] =
rA =
—
where
]
rate of inflow
rate of outflow
(m 3 /h)
A
A
concentration of reactant
concentration of reactant
in
feed (mol/m 3 )
in
tank and in effluent (mol/m 3 )
A
rate of reaction of reactant
concentration [A]
at
(mol/m 3
—A' [A] for a first-order reaction
V =
liquid
=
mean
/
Chapter 6
volume
tank (2/(m
in
t
and
-k[A],
rA
or residence time,
rA
[A]
=
[A
=
(h),
~t
gives
() ]
1
and since VI Q
h)
)
hydraulic detention time
Dividing equation (6.76) by (2[A
•
3
it
[A ]Q
]
follows that
k[A\t
[A]
.
"
V
[A
[AJ
]
[A]
+kt)
(1
[A
]
so that
kt
[Aq]
=
1
[A]
A
similar procedure for other reactors and/or orders of reaction results in the ki-
netic equations
summarized
in
Table 6-6.
TABLE 6-6 KINETIC EQUATIONS RELATING MEAN RESIDENCE TIME
AND REACTANT CONCENTRATION [A] IN PFT AND CST REACTORS
Type of reaction
Equation
A
->
C
A
-*
C
2A
->
C
Order
Type of reactor
Rate
2
Example 6.24 shows
=
kt
[A
"=
-*[AJ
-*[A] 2
Mixed flow
Plug flow
-k
1
t
]
-
[A]
kt
,n
kt
TAT
A/
kt
[A
]
I
[A]
)
=
~
[Ao]
-
[A]
"[A]l[A]
the application of these kinetic equations.
[A]
'
l
)
'
207
Reaction Kinetics and Reactors
Sec. 6.6
Example 6.24
A
reactor
is
used to carry out conversion of component
to be
tions call for a 999c conversion of
Because the reactor
component A. The
relatively long
is
to product C.
feed rate
1000 ftVh? What
is
in
By assuming
required volume of reactor will the engineer
=
make
if
the
be? Assume (1) a constant-volume
will the actual conversion
reaction for the fluid of density p
.
along the reactor,
at intervals
the actual mixing conditions are those of a completely stirred tank reactor.
plug flow conditions, what error
Specifica1.0 h _l
=
and narrow, the engineer assumes plug flow condi-
However, because there are powerful mixers situated
tions.
A
first-order rate constant k
1.00, (2) that steady-state conditions apply,
and
(3)
that all conversion takes place in the reactor.
PFTR: For
Solution
Table 6-6
a first-order reaction in a
99%
ln
I
TXT
conversion.
_
[Ail
=
Q =
1
I.Oh"',
1
Since
100
"
[Al
and for k
the applicable kinetic equation from
[A ° ]
L, =
"
For
PFTR.
is
1000
ft-Vh, the
CSTR: For
required
x
t
=
—
In
V= Q x
t
=
=
1000 x 4.6
CSTR,
a first-order reaction in a
4.6 h
=
4600
ft
3
.
the applicable equation
from Table 6-6
is
[A]
For
99%
conversion.
I
Ail
_
=
100
[A]
and for
A:
=
1.0
h"
1
1
.
t=!f -l=99h
The required volume V
quired volume
=
Qi
=
1000 x 99
=
99,000
ft
3
.
Therefore, the error
in the re-
is
99,000
- 4600 =
94,600
ft
Actual conversion
If
ot a
the actual
CSTR,
that
volume of
the reactor
is
4600
3
ft
is.
k,-^
[Al
-I
but the
working conditions are those
208
Physics and Chemistry
Chapter 6
and
t
= —V —
4600
ft
3
:
Q
1000
=
r
4.6 h
ft -Vh-'
then
10 °
^
X46=
A
[A]-
so that
[A]
= —— =
17.9% remaining
5.6
and the actual conversion
is
100-
17.9
=
82.1%
100
Example 6.24 shows
tion is about
the
CSTR
dence
sign
had
reactors as
all
PFTR.
=
99,000/4600
to be
we might conclude
removal efficiency of a
that the
less than for a
-
saw
also
CSTR
that for the
21.5 times larger than the
because they are so
that
PFTRs.
We
much more
for a first-order reac-
same 99% conversion,
PFTR. From this evi-
efficient,
decrease with lower orders of reaction and lower removal requirements.
PFTR
tice, full-scale
somewhere between
order, but in
units
a
we
should de-
However, the differences between the two types of reactors
do not perform close
PFTR
and CSTR.
between zero and
first
Moreover, reactions
In any case, the
order.
Also, in prac-
to ideal conditions but, rather,
may
perform
not be exactly
first
volumes provided are nor-
mally well above the theoretical requirements for conversion and the slightly lower efficiency of the
CSTR may
be offset by
its
greater stability and
with reactors in series or
ous reactions
is
more uniform
effluent
Information on more complex systems
characteristics under varying loading conditions.
in parallel, variations in inflow, recirculation,
and heterogene-
available elsewhere (Levenspiel, 1972).
PROBLEMS
6.1.
Balance the following equations
(a)
+ HC1 -> FeCI 2 + H 2 S
+ KOH -* KC1 + KCIO, + H
Mn0 2 + NaCl + H 2 S0 4 -> MnS0 4 + H + Cl 2 + Na 2 S0 4
H C 4 + KMn0 4 + H 2 S04 -> C0 2 + MnS0 4 + K S0 4 + H 2
-> Fe(OH) 3
Fe(OH) + H 2 +
FeS
(b) Cl 2
(c)
(d)
(e)
2
2
2
2
2
2
2
6.2.
Calculate the rise velocity of an air bubble 100 urn in diameter in a tank of water at 20 C.
6.3.
Calculate the length of time
diameter of 0.8
mm
it
will take for a
to settle to the
jagged
flint
sand particle with an equivalent
bottom of a 4-m-deep tank.
Chapter 6
6.4.
C
water, of a spherical sand particle of diameter
coal-fired electric generating station has a
100-m-high stack from which particles are emit-
Find the terminal settling velocity,
A
ted and rise an additional 100
wind speed between
downstream from
fore
6.6.
20
in
mm.
0.07
6.5.
209
Problems
it
m
due
to
the earth's surface and the
The weight of
then weighed,
is
is
from a laboratory
the clean
48.610
filter
will travel be-
test to
A
100-mL sample
at
a thermal efficiency of
88%
of the
is
filtered
through a
filter
is
48.903
What
g.
S02
is
the concentration of suspended
of
CaS04
mg/L?
How many moles of H 2 S0 4 are required to form 65.0 g
A 1000-MW coal-burning power plant burns anthracite
the ash and
its rise.
determine the suspended solids con-
After filtration, drying at 104°C, and cooling, the weight of the
g.
solids in the wastewater sample, in
phur
g/cm 3
pad and crucible, both of which were dried, cooled, and
and dried solids
crucible, filter pad,
6.8.
horizontal
Estimate the distance
level is 10 m/s.
the stack that a 15-|im (micron) particle of density 2
centration of a sample of untreated wastewater.
6.7.
m
200
reaches the earth's surface. Neglect the horizontal travel of the particle during
The following information
pad.
The average
plume thermal buoyancy.
40%. Heat content of
the coal
are trapped before emission
from
containing
is
5%
CaC0 3 ?
ash and 2.5% sul-
31,280 kJ/kg.
from the
If
99.5% of
stack, calculate:
The rate of coal input to the furnace (kg/day)
The emission rate of ash and S02 to the atmosphere (kg/day)
(c) The volume of S0 2 emitted (mVday) at 20C and atmospheric pressure
A sample of 25.26 g of hydrated magnesium sulfate (MgS04 X H 2 0) is heated to 400C to
remove the water of crystallization. It is found that 12.34 g of anhydrous magnesium sulfate is left. What is the value of XI
(a)
(b)
6.9.
6.10. Ethanol
is
accidentally spilled into a river, where
is
it
degraded by microbial action accord-
ing to the reaction equation
C 2 H 5 OH + 30 2
How many
(a)
->
2C0 2 + 3H 2
kilograms of oxygen are consumed
in the
process
if
500
lb of ethanol
were
spilled?
How many kilograms of C0 2 are
How many grams of magnesium will
(b)
6.11.
6.12. Air
is
a solution
whose major components
tions of 0.781, 0.210.
6.13.
A
produced?
be necessary to form
and 0.009, respectively.
sample of 7.14 g of potassium iodide
1
kg of magnesium carbonate?
are nitrogen, oxygen, and argon, with
is
dissolved in 145 g of water.
What
molality and (b) the mole fraction of KI in the solution?
6.14. Fill in the blanks in the following table.
Ion or
compound
Na +
meq/L
mol/L
io-
mg/L
9.3
(HCO)^
122
-2
so 4
OCL
ppm as
CaCOj
3
Fe +3
32
5 x
10
4
mole
frac-
Calculate the mass fractions of each.
are (a) the
210
Physics and Chemistry
pH
6.15. Calculate the
mg/L sodium hydroxide
(b) 25
100 mg/L acetic acid
(c)
100 mg/L hypochlorous acid
(d)
A
of a solution, which before dissociation contained:
25 mg/L hydrochloric acid
(a)
6.16.
Chapter 6
smelter emits
1
S02
tonne of
which
H 2 S0 4
converted to
is
moist atmosphere ac-
in the
cording to the reactions
SO : + H 2
2H 2 S0 3 +
When
pH of
C0 2
rain based
C0
2
1-L aqueous solution contains 100
NaOH
(d)
concentration of
1
dissociation of
mg/L of HC1.
mol/L, also
after the addition of 2
after the addition of 3
2
total area of 400 km
what
pH component is incorporated into
H2 S0 4 and a pH of 5.6 for normal
over a
,
Its
pH
to
is
be altered by the addition
aqueous solution.
in
mL
mL
of
of
Calculate:
NaOH
NaOH
the environmental control officer for a zinc and lead smelter
trolling acid rain emissions.
removed from
that
is
(a)
Based on
This
is
kg of
S02
how many
liters
H 2 S0 3 + Ca(OH) 2
(b) If the calcium hydroxide
6.19. Explain
sists
how
changes
to
are in charge of con-
is
only
make 100 L of
of 2
M
Ca(OH) 2 would be
required to
produced each day?
S0 2 + H 2
be diluted
you
be accomplished by neutralizing the sulfur dioxide
to
the stacks during the smelting operation.
the reaction below,
neutralize the 120
A
rainfall
the only other
1
The pH
The pH
(c)
6.20.
2H 2 S0 4
The initial pH of the solution (HCL only)
The pH after the addition of mL of NaOH
(b)
As
H 2 SO,
levels.
of
at a
if
Assume complete
on ambient
A
(a)
6.18.
levels?
10-mm
in a
25 "C might be expected
rain at
ambient
6.17.
ground
this rain falls to the
2
—
95%
the 2
->
H 2 S0
-»
CaSO, + 2H 2
3
pure by weight,
how many kilograms
of
it
must
M solution?
the carbonate system in natural waters provides "buffering" capacity that rein
pH.
water sample has been analyzed with the following
results:
Amount
Calculate the
alkalinity as
6.21.
Assuming
Cation
(mg/L)
Ca+ 2
104
Mg+ 2
38
Na+
19
number of milliequivalents
mg/L CaC0 3
per
liter
of each cation, the
total
hardness, and the
.
that all the cations
and anions present
pare the reported cation and anion concentrations
in a
in
water have been accounted for com-
meq/L.
In a perfect analysis, cations
Chapter 6
211
Problems
and anions contained
in the
The reported
water would balance.
results of a water
sample
are as follows:
Anions (mq/L)
Cations (mq/L)
Na+
90
CI-
102
Ca+ 2
60
HCO^
220
Mg+ 2
20
SO4
Fe+ 2
Does
6.22.
An
maximum
this analysis fall within a
64
NOJ
2
1
acceptable error of
10%?
analysis of a water sample yields the following results:
Total alkalinity
72 mg/L as
Temperature
25
pH
9.8
CaC03
C
Calculate the carbonate, bicarbonate, and hydroxide alkalinities.
6.23.
A 200-mL
water sample from Lake Scugog required 2
phenolphthalein endpoint and an additional
Samples taken
total alkalinity
of 90
mL
What forms
phthalein to the methyl orange endpoint.
CaCO, )?
from Lake Muskoka
10
mL
of 0.02
of acid to
N H S0 4
2
titrate
to reach the
from the phenol-
of alkalinity are present and in what
concentrations (as
6.24.
pH
reduced the
mg/L
to 8.6
in
(both as
1975 had a phenolphthalein alkalinity of 50 mg/L, a
CaC03
),
and a
pH
reach the phenolphthalein endpoint and an additional 10.0
from the phenolphthalein
nents
(OH - COf 2
,
,
and
to the
menthyl orange endpoint.
HCO^
)
that
were
in the
water
mL
If
Lake Ontario water has concentrations of Ca+ 2 and
mol/L, respectively, what
6.26.
is
Cations
mg/L
Ca+ 2
60
Mg+ 2
20
Na+
15.5
Calculate the hardness and alkalinity as
equivalent weights.
(a) the
H 2 S0 4
the alkalinity
to
titrate
compo-
each component.
of 0.00096 and 0.00022
mg/L
of
CaCO;?
8
mg/L CaCO^.
20 mg/L of Ca +2 and
6.27. Calculate the alkalinity of water containing
Use
/V
cations were obtained from a water analysis:
K'
CaCOv
in
Mg +2
of 0.02
beginning and end of the
the hardness of the water, expressed in
The following concentrations of
pressed as
mL
of standard acid to
Compare
at the
20-year period and determine the percent removal or increase
6.25.
Since then, acid rain has
of 10.3.
by 1995 and 200-mL sample required 2.0
formulas provided
in
15
mg/L of
Mg +2
,
ex-
Section 6.3.3 and (b) the method of
212
6.28.
Physics and Chemistry
Upon
analysis, a
sample of water
found
is
Chapter 6
to contain the following constituents at the
con-
centrations indicated:
Carbon dioxide (C0 2 )
8.8
Calcium bicarbonate [Ca(HC0 3 ) 2
Calcium
(CaS04
sulfate
Lime (Ca(OH) 2 )
186.3
]
81.6
)
C02
used to precipitate the
is
mg/L
mg/L
mg/L
Ca(HC03 ) 2
and
,
and soda ash (Na 2 C0 3 )
is
able to precipitate the calcium sulfate according to the following equations:
C0 + Ca(OH) 2
2
Ca(HC0
+ Ca(OH)
3 )2
2
CaS0 4 + Na 2 C0 3
-+
CaC0 3 (ppt) + H 2
-»
2CaC0 3 (ppt) + H 2
->
CaC0 3 (ppt) + Na2 S0 4
Calculate the mass of lime and soda ash required to theoretically soften
L
1
of the water
completely.
6.29.
6.30.
What
pressure (kPa)
is
needed
is
1000 mbar?
A
cylinder storing oxygen at 20
At what
maximum
to
make
MPa
at
air at
0C
may
temperature (°C)
20C
as dense as air at
might explode
if
0°C whose pressure
the pressure exceeds
50 MPa.
be safely stored, allowing for a
this cylinder
safety factor of 2.0?
6.31.
An
engineer wishes to store methane gas (CH4) produced
sewage treatment
at a
6.32.
If the gas,
plant.
produced
200 kg/day,
is
to
be stored
at
20°C and 4 MPa, what volume of tank is required for a 10-day storage period?
A 50-mL sample of oxygen at a pressure of 0. MPa is mixed with a 250-mL sample of
nitrogen at the same temperature and at a pressure of 0.0667 MPa. The mixture is placed
1
in a
1
50-mL
gas and the
no change of temperature.
vessel, with
total
6.33. Calculate the
Calculate the partial pressure of each
pressure in the vessel.
amount of oxygen (mg/L) dissolved
in river
conditions, at an atmospheric pressure of 100 kPa.
6.34.
an anaerobic sludge digester
in
a rate of
at
A sample of 1.002
mL of oxygen at a
and the
total
g of graphite (C)
pressure of 1.00
is
completely burned
MPa
at
27C.
water
water
(k H in
30°C under saturated
at
at
30
C
is
in a steel vessel
4810 MPa.)
containing 250
Calculate the mole fraction of each gas
pressure after combustion, assuming that
all
gases are ideal and that the tem-
perature increases 2.5°C.
6.35.
What volume of oxygen
at
27°C and 0.21 atm
is
required for the combustion of 25 g of
methane gas?
6.36. Anaerobic digestion of an industrial waste, largely acetic acid, produces carbon dioxide and
methane
gas.
Calculate the volume of
6.37.
A new
power
S0 2
removal
produced daily
of about 5
will,
plant.
km
in
facilities is
of 6.2.
20°C
for an av-
going
to
be built on the outskirts of a
It
is
estimated that an area
each direction from the plant will be affected by the smokestacks and
under the worst circumstances, contain about
The
at
3
Coal with a 1.8% by weight sulfur content will be used.
city.
pH
plant without
CH 4 gas
CH COOH.
COi and
erage daily waste production of 500 kg of
1
day's production of SOk from the
precipitation records indicates a typical rainfall of 5
Calculate the
maximum
in the rainfall to less than 5.0.
the affected area dissolves
all
cm
in
24 h with an average
permissible daily use of coal without lowering the
The following equations apply (assume
the
S02
present there):
pH
that the rainfall in
Chapter 6
213
Problems
S
2S0 2 +
6.38.
4-
+ 2H
2
-> SO,
2
2H 2 S04
-*
2
The acid rain problem was discussed in Chapter 5. From this general information and the
knowledge gained in Chapter 6, consider the following situation: An industrial plant emits
S0 2
atmosphere on a steady
into the
cipitation
is
face area
=
80 cm/yr.
8
km 2
pH
at a
average depth
,
basis.
A
of 4.5.
=
Rainfall records indicate that the annual pre-
nearby lake has the following characteristics: sur-
10 m,
pH =
5.5, alkalinity
area from which runoff drains directly to the lake
on the land reaches the
rain falling
is
Assume
lake.
25
=
25 mg/L as
km 2 Assume
that
.
CaC0 3 The
20% of the
.
only
also that on a yearly basis the lake
is
completely mixed and that the small river flowing into and out of the lake can be neglected
as far as acidification
pH
a
6.39.
A
city situated
ment plant
mg/L)
1
How many
concerned.
on a large
river disposes
The minimum flow
basis.
(
is
years will
it
be before the lake will reach
of 5.0?
stream
is
be safely
m3
12.5
is
in the
/s.
of
in the river is
If the
downstream
maximum
river,
m-Vs,
and the discharge
and the "background" concentration of
ppm, what is the maximum concentration of
released from the water pollution control plant?
lease of the pollutant,
and
rate
from the
acceptable limit for a certain pollutant
0.4
6.40. In the situation described in
on a continuous
treated wastes to the river
its
210
Problem 6.39, assume
that
one factory
is
treat-
1.0
ppm
this pollutant
the pollutant, in
that overall treatment plant efficiency for
is
mg/L,
that
up-
can
responsible for the re-
removal of
this material
60%. If the average waste flow out of the factory is 0.05 mVs, then, neglecting volumes
removed from flows (i.e., in sludges, etc.), what is the maximum concentration of the polis
mg/L,
lutant, in
6.41.
A
cilities
5.0%
6.42.
A
that
may
be released to the sewer system?
domestic wastewater contains 350 mg/L of suspended
remove 65% of these
solids will be
form 3.0%
to
Primary sedimentation
fa-
produced per million gallons of wastewater handled?
gpd of wastewater sludge and increases the
gravity thickener receives 33,000
tent
solids.
Approximately how many gallons of sludge containing
solids.
7.0% with 90%
solids recovery.
solids con-
Calculate the volume of thickened
sludge.
6.43. Dust
is
removed from
the airstream of a municipal incinerator by four dust collectors oper-
ating in parallel, each handling one-fourth of the total airflow of
200 mVmin.
stream contains 10 g/m 3 of suspended solids and collector efficiency
linearly to
74%
as the airflow
is
doubled.
from the combined stack discharge
is
If the
1.0
maximum
g/m\ can one
is
98%
The
air-
decreasing
permissible solids concentration
collector be temporarily taken out
of service (a) by overloading the other three units; (b) by not treating one-fourth of the
air-
flou ?
6.44.
The
rates of
enzyme-catalyzed reactions sometimes follow a
1
(a)
What
(b)
Indicate an approximate
and
/
is
such as
-k[A]
+*'[A|
the order of this reaction?
method of
plotting the experimentally obtained data for |A|
by the method of integration, so that two straight lines are obtained
equation
(c)
rate equation
is
followed.
Comment on
the delects of fitting a straight line to the
(Courtesy of C. Crowe, McMaster University.)
two
plots.
if
the rate
214
6.45.
Physics and Chemistry
Benzene diazonium chloride decomposes according
C 6 H 5 N 2 CL
At 50°C, with an
to the equation
C 6 H 5 C1 + N 2
-»•
concentration of 10 g/L of
initial
Chapter 6
QH
5
N 2 C1,
the following results were
obtained:
Time
6
9
12
14
18
22
24
26
30
OO
19.3
26.0
32.6
36.0
41.3
45.0
46.5
47.4
50.4
58.3
(min)
N
2
evolved
(cm 3 )
(a)
By
(b)
Use
A
method of
the
likely order of reaction, with reasons for
chemical reaction
rate equation
is
CSTR. Component A
carried out in a
is
converted to product C, the
being reported as
=
rA
-0.15 [A] mol/L-
90%
Calculate the volume required for a
(a)
your choice.
integration to determine the order of the reaction and the rate con-
(Courtesy of C. Crowe, McMaster University.)
stant.
6.46.
most
inspection, suggest the
100 L/s, assuming
(b) After the design
is
order of reaction.
that [A,,]
=
s
conversion of
A
for a volumetric flow rate of
0.10 mol/L.
completed, the engineer finds out that an error has been made
It
turns out not to be
first
in the
order, but zero order, the correct equation
being
rA
What
6.47.
A
effect will this
wastewater
—A [A] where
volume
is
20
A
in a
stream
sity
an irreversible, first-order reaction r A =
can be handled if the reactor
What volume would be
the treatment efficiency need only be
One
CSTR
reactor
reactors operating at steady state in par-
twice the size of the other.
is
re-
92%?
The
total feed
appropriately between the two reactors to achieve the highest fractional conis
0.70.
The smaller
reactor needs to be taken out of service for
feed rate stays the same, what
If the total
the larger reactor?
A
if
same temperature.
is split
s
3
version of reactant, which
repair.
6.49.
CSTR. Assume
liquid-phase reaction takes place in two
allel at the
•
= 0.15 per day. Determine the flowrate that
m and 98% treatment efficiency is required.
k
quired for the same flowrate
6.48.
—0.15 mol/L
have on the design?
be treated
to
is
=
Assume
that the reaction
is first
is
the resulting fractional conversion in
order.
(Courtesy of R. Missen, Univer-
of Toronto.)
second-order, liquid-phase reaction (A -> products)
is to
take place in a batch reactor at
The rate constant is 0.05 L/mol min. The initial concentration [A]
is 2 mol/L.
If the downtime tD between batches is 20 min, what should be the reaction
time t R for each batch so that the rate of production is maximized on a continuing basis?
constant temperature.
Note
6.50.
A
that the total batch time
liquid reaction
sion
•
is
PFTR;
achieved
(b) in a
is
in
is t R
+
t
D
.
(Courtesy of R.
Missen, University of Toronto.)
A 50%
conver-
same conversion
(a) in a
carried out in a batch reactor at constant temperature.
20 min.
CSTR?
How
long will
it
take to achieve the
Chapter 6
6.51.
215
References
The required detention time of a plug flow tubular reactor, used for wastewater treatment is
a minimum of 3 h. The dimensions of the tank are: length 100 m, width 10 m. depth 4 m.
Calculate the maximum flowrate. in m-Vs, that can be accommodated and the velocity of
flow, in m/s.
6.52. Air bubbles 100 microns
PFTR
(a)
(um)
through which water
at
in
diameter are injected into the bottom
20C
inlet
of a 1-m-deep
flows with a detention time of 4 min.
Will the air bubbles reach the water surface before the water overflows at the outlet of
the tank?
(b)
Draw
the tracer output curve for the
PFTR
and label
all
Assume
parameters.
continu-
ous tracer input and ideal flow behavior.
6.53.
Why
in
theory does a
PFTR
have a higher removal efficiency than a
CSTR, and why
is
this
difference not evident in practice?
REFERENCES
APHA, AWWA,
and
WPCF
Standard Methods for the Examination of Water and Wastewater,
American Public Health Association, American Water Works As-
16th ed. Washington D.C.:
sociation, and
Water Pollution Control Federation, 1985.
Bird, R. B., Stewart, W.
E.,
and Lightfoot, E. N. Transport Phenomena.
New
York: Wiley,
1960.
Breck, W. G., Brown, R.
ronto:
Butler,
J.
ley,
J.
C, and McCowan,
J.
D. Chemistry for Science and Engineering, To-
McGraw-Hill Ryerson, 1981.
N. Carbon Dioxide Equilibria
and Their
Applications. Reading, Mass.: Addison-Wes-
1982.
Hidy, G. M., and Brock,
J.
R. The
Dynamics of Aero-colloidal Systems. Oxford: Pergamon
Press,
1970.
Himmelblau, D. M. Basic Principles and Calculations
in
Chemical Engineering. Englewood
Cliffs, N.J.: Prentice Hall, 1982.
Levenspiel, O. Chemical Reaction Engineering.
Mahan,
New
York: Wiley, 1972.
B. H. University Chemistry. Reading, Mass.: Addison-Wesley, 1975.
Perkins, H. C. Air Pollution,
ford Research
Institute
New
York: McGraw-Hill, 1974 (originally from C. E. Lapple, Stan-
Journal 5(94) (1961
Perry, R. H. Chemical Engineer's Handbook.
).
New
York: McGraw-Hill, 1984.
Rich, L. G. Unit Operations of Sanitary Engineering.
Sawyer, C.
N.,
and McCarty,
P.
L. Chemistry for
New
York: Wiley, 1980.
Environmental Engineering.
New
York:
Graw-Hill, 1978.
Snoeynik,
V. L.
Williamson.
J.
and Jenkins, D. Water Chemistry.
New
York: Wiley, 1980.
Fundamentals of Air Pollution, Reading, Mass.: Addison-Wesley, 1973.
Mc-
CHAPTER
7
Atmospheric Sciences
F.
7.1
Kenneth Hare
INTRODUCTION
The atmosphere
is
a vital
component of
the
the solar energy that controls our climate.
human environment.
It
It
transmits and alters
acts as a shield, protecting us
from dam-
aging meteoritic impacts and from penetrating radiation, such as ultraviolet rays from
the sun.
It
supports the flight of birds and insects and transports seeds and spores.
gases provide the raw materials for
life itself:
without them,
we
could not
Its
exist.
Weather and climate are the two aspects of the atmosphere of which we are most
aware.
Weather
the
is
Weather elements are
ence of weather
is
name we
rain,
give to the states of the sky,
snow, heat, wind, thunder, and fog.
by atmospheric gases.
Weather
oughly monitored.
ent
wavelength bands.
A
pheric properties, in
216
However, no other
satellites
look
part of the
downward
at
cover, fog, or haze
is
is
shortwave sunlight
environment
the atmosphere in
is
so thor-
many
differ-
Radiosonde balloons, measuring temperature, pressure, and
humidity, are sent up to over 30
around the globe.
wind, and water.
integrated experi-
the climate, the characteristic annual cycle of weather.
Most of us are aware of the atmosphere only when cloud
present, or when we look at the blue of the daytime sky, which
scattered
air,
Our
km
once or twice daily from more than 1000 stations
close network of ground observing stations also measures atmos-
some cases hourly and
in
some cases continuously, by recording
in-
217
Basic Atmospheric Properties
Sec. 7.2
This
struments.
product of 150 years of evolution,
effort, the
World Meteorological Organization, with headquarters
The study of weather gave
and chemistry of the lower atmosphere.
km
above sea
field
level,
behaves
coordinated by the
is
Geneva.
meteorology, which is the physThe upper atmosphere, which begins 100
birth to the science of
ics
aeronomy.
in
The
differently.
scientific study
of
is
it
sometimes called
Electromagnetic forces and chemical activity are more important in
than in meteorology.
Climatology, the study of climate,
the earth's atmosphere behaves over long periods of time.
is
this
concerned with how
All these areas of study, to-
gether with atmospheric chemistry, form the atmospheric sciences.
The engineer and
for several reasons.
scientist
need
to
know
the facts about the weather
For example, not only does the control of
and climate,
air pollution require
knowledge of how the lowest layers of the atmosphere behave, but some pollutants
spread through the entire atmosphere, so that the higher layers also need to be studied.
An
understanding of world climate
home.
larly,
lic
useful as well in projects undertaken far from
works, such as drainage improvements, reservoirs, dams, and water supply
Also,
air
a
is
The vagaries of climate can make supplies of food and water unreliable. Simiknowledge of rainfall occurrence and intensity is essential for the design of pub-
snow and wind must be considered
in the
facilities.
design of structures; and the range of
temperature relates directly to the design of heating and air-conditioning systems and
insulation requirements.
7.2
BASIC ATMOSPHERIC PROPERTIES
7.2.1 Composition and Physical State
The atmosphere is a mixture of gases, with numerous suspended particles, some solid
and some liquid. The lower atmosphere is electrically neutral, containing few free ions;
for the most part, it is composed of molecules. The upper atmosphere, by contrast, is
extensively ionized: many gases are broken up into single atoms or into free radicals
such as hydroxyl (OH). Because of its special role, water vapor (H 2 0) is often dealt
with separately. The atmosphere is then said to be made up of dry air and water vapor, together with suspended particles. Table 7-1 shows the main constituents of dry
air.
As
Oxygen and
99.04% by volume, and inert argon atoms a further 0.93%. All the remaining constituents of dry air make up only 0.03%.
Yet they are important. Carbon dioxide, for example, is essential to life and is critical
to climatic control. Ozone, present chiefly above 15 km, is very toxic and also affects
climate. In addition, it shields us from damaging ultraviolet radiation. Carbon dioxide,
illustrated in Table
7-1 most gases have constant concentration.
nitrogen molecules, both with two atoms, form
ozone, and radon fa radioactive decay product escaping from the solid earth) vary
in
concentration.
Dry
air is so nearly fixed in
composition
a molecular weight of 0.028964 kg/mol.
that
we can
treat
it
as a single gas with
At the range of temperatures and pressures
218
Atmospheric Sciences
Chapter 7
TABLE 7-1 COMPOSITION OF PURE DRY AIR (WITHOUT WATER VAPOR)
IN LOWER ATMOSPHERE, WITH MOLECULAR WEIGHTS AND ENVIRONMENTAL ROLES
Concentration
Formulas
Gases
(% by volume)
Molecular
weights
(kg/mol x 10 3 )
Environmental roles
Active gases
N2
Nitrogen
78.09
28.0
Inert as
N2
life as
Oxygen
20.95
0:
32.0
;
essential to
N
Essential to
life;
chemi-
cally active
H
Hydrogen
5.0 x
2
10" 5
2.0
Important
in
atmos-
pheric chemistry
Inert gases
Argon
Ar
0.93
39.9
Inert
Neon
Ne
He
x 10" 3
5.2 x 10" 4
20.2
Inert
Helium
1.8
4.0
Inert;
escapes from
earth's crust
Krypton
Kr
Xenon
Radon
Xe
Rn
x 10~ 4
8.0 x 10" 6
6.0 x 10" 18
83.7
Inert
131.3
Inert
222.0
Radioactive; variable in
1.0
height and time, be-
cause of decay
Variable gases
co 2
Carbon dioxide
3.6 x
10" 2
44.0
Essential to
life;
opti-
cally active
o3
Ozone
1.0
x 10" 6
48.0
Toxic, optically and
chemically active
Other trace constituents include sulf jr dioxide (SO2), carbon monoxide (CO) oxides of single nitrogen
(NOJ, and various pollutants
Source:
p.
R.
389, with
J.
List,
C0
2
Smithsonian Meteorological Tables (Washington, D.C.: Smithsonian
Institution. 1951. Table
1
10.
updated.
observed
in nature,
dry air obeys the law for a perfect gas, that
is,
PV = nRT
[Equation
(6.41)], or slightly differently stated,
p
where
=
p =
T =
R —
p
pressure
density
(N/m 2
(kg/m
=
= RpT
(7.1)
pascal)
3
)
Kelvin temperature (K)
gas constant for dry air (287.0 J/kg
•
K)
This equation of state is one of the laws governing atmospheric behavior. Only
two parameters of state are really needed, so in practice we use temperature and pressure, which are easy to measure. The mean surface temperature of the earth is 288 K,
219
Basic Atmospheric Properties
Sec. 7.2
and the mean sea-level pressure
is
1.013.2 mbar.
|For convenience, the meteorologist
One mbar
equal to 100 pascal (Pa).) Note that
uses the millibar (mbar) as a unit.
is
pressure does not determine temperature, or vice versa: cold air can have low pressure,
and
warm
air
high pressure.
Water may be present
por
always present.
is
V<
about
m
:
The
b> volume.
vapor present
in
The
It
The molecular weight of
because of earlier
The smaller
particles in a gas)
10
bomb
occasionally reaches
natural water
is
I
kg/m : in
50 kg/m : in temperate North America.
Natural water contains two
0.018016 kg/mol.
'H and deuterium
2
(
H
3
(
or D), which contains an
H
or T) are present, chiefly
atmosphere form an aerosol
particles within the
-3 micrometer (|im)
(i.e.,
in radius.
At sea there are fewer of them, but maritime
key role
in
atmospheric particles
air contains
many
Certain sizes of par-
condensation.
and form the reduced
ticles reflect sunlight diffusely
colloidal-sized
The smallest detectable particles
Such particles are very numerous inland,
to fall out rapidly.
larger non-chloride particles that play a
Many
is
column of area of
the most humid parts
testing.
and are too small
especially in cities.
mist, or fog.
most of the water vapor
In practice,
Very small quantities of radioactive tritium
extra neutron.
to
the liquid water equivalent of the water
very cold air to about 60
in
stable isotopes of hydrogen, ordinary
-1
is
Water va-
solid, or liquid.
be as high as 40 mbar, equivalent to
precipitable water for the entire vertical
of the tropical countries.
are 10
may
precipitable water
from almost zero
varies
atmosphere as gas (vapor),
in the
partial pressure
any column of the atmosphere.
lowest 5 km.
in the
Its
visibility conditions called haze,
are, in fact, liquid, since they attract
water va-
por condensation and go into solution.
Without the aerosol, clouds,
cles
rain,
and snow could not form.
from chimney smoke, car exhausts, or loose
health prohlems.
Most
air pollution is
soil
But too many
parti-
may
cause
reduce visibility and
of this variety.
7.2.2 Thermal and Electrical State
Figure 7-1 shows the permanent layers of the atmosphere.
sphere, capped by a surface of
tween 10 and 17
since the
km
above the
main heat source
sea.
is
Temperature decreases with height
about 5.0 K/km.
reaching a
the tropopause.
maximum
about as high as
at
50
at
ground
diation from the sun by
found
in the stratosphere,
The notation 'H and
:
H
to
is
ground
in the
level.
Winds tend
also the level
at
the tropo-
be-
at levels
troposphere,
The
rate of deo\'
the
to be strongest at the
which
temperature increases with height
in
jet aircraft cruise.
the stratosphere.
55 km. the so-called stratopause. where temperature
level.
where
warmth
Its
oxygen (0 2
is
is
The troposphere contains most
water vapor, clouds, and storms of the atmosphere.
tropopause, the level of the jet streams. This
Above
At the base
temperature called the tropopause
solar radiation absorbed at
is
crease, called the lapse rate,
minimum
it
)
is
due
to the absorption
and ozone (O3).
may exceed
Most of
of ultraviolet
the world's
5 parts per million by
ozone is
volume (ppmv).
used here to differentiate between an ordinary hydrogen atom of mass
proton) and a hydrogen atom of mass 2 (one proton and one neutron). Tritium,
'II.
is
ra-
has an extra neutron.
I
(one
220
Atmospheric Sciences
Chapter 7
60
Mesosphere
50 -
i\
)
40
-
30
-/
s
E
£
//
Stratosphere
X
20
4\
10
~
T
I
^^^v>^
Figure 7-1
^^
—
-80-70-60-50-40-30-20-10
Troposphere
areas, all year;
r-
i
i
i
i
III,
10
20
30
Temperature (°C)
Hence
stratospheric air
is
lethal to
Typical temperature
distributions with height.
II,
I,
hot, tropical
polar regions,
summer;
polar regions, winter (T marks the
tropopause on each curve; S
is
the
stratopause).
human
beings.
There
is
very
little
water vapor
at
these heights.
The mesosphere extends from the stratopause at 50 to 55 km to another temperat 80 km, the mesopause. The mesosphere is a windy and turbulent region, but there is usually too little water vapor for clouds to form.
Above the
mesopause, temperature increases indefinitely upward into the thermosphere, the hot
ature
minimum
upper atmosphere.
The air nearest the earth's surface is called the boundary layer. The planetary
boundary layer (below 1000 m) is the layer in which the wind is affected by friction with
the earth's surface. The bottom 50 m is often called the surface boundary layer. These
layers are very important to the engineer, most of whose work is done at such levels.
The temperatures of the air, sea, and land surface are controlled by unequal heating and cooling by the sun or outgoing radiation.
This accounts for the familiar
changes of heat and cold during a typical day and between seasons.
why
the tropics are
warm and
ocean currents also affects
air
The lower atmosphere
mosphere.
is
polar regions cold.
The
It
also explains
transport of heat by winds and
temperature.
usually electrically neutral, unlike the ionized upper at-
Nevertheless, strong potential gradients do exist, especially in and around
thunderstorms.
In a thunderstorm, gradients of
50,000 volts/m are sometimes observed
Sec. 7.3
near the ground.
to
when
Lightning (a discharge) occurs
300.000 volts/m are generated
structures like steel towers or
7.3
221
Energy Outputs and Inputs
in the
gradients on the order of 100,000
towering clouds of thunderstorms.
Engineered
buildings are often struck by such discharges.
tall
ENERGY OUTPUTS AND INPUTS
7.3.1 Solar Radiation
The sun provides 99.97% of
The only other sources are
(
the heat used at the earth's surface for all natural processes.
geothermal energy, the source of which
1 )
grations in the earth's interior, and (2) starlight from space.
with the heat from the sun. The energy
we
use in our
and natural gas contain solar energy stored
oil.
in the
remote
Both are
economy
is
is
tiny
nuclear disinte-
by comparison
also mainly solar. Coal,
of photosynthesis
in plant tissues as a result
Burning them releases ancient solar energy and carbon dioxide into the
past.
atmosphere. Currently,
we burn
these fuels
at
a world rate under 10' 3
W, which
small
is
which the earth receives solar energy (1.74 x 10 17 W).*
The annual mean energy received is 5.5 x 10 24 J, or 1.5 x 10 18 kWh.
by comparison with the rate
The sun
at
a fairly constant
is
and intensity of the radiation
it
star.
emits.
We
can detect only small variations
Hence we speak of
in the nature
which
the solar constant,
is
the intensity of solar radiation reaching the top of the earth's atmosphere.
136X
sun.
Measured at right angles to the solar beam, the solar constant is estimated to be
on each square meter of the circular outline (disk) of the earth as it faces the
The spin of the earth distributes this power over the whole surface of the sphere,
W
whose area
four times as great as that of the disk.
is
unit area of the earth's surface
is
342
W/m
2
.
Hence
the
mean
solar constant per
(Surface area of a sphere
=
Solar radiation resembles that of a blackbody (perfect radiator) near
47ir
2
.)
6000 K. The
500 nm (see Figure 7-2), with most of the
in the range 200 to 5000 nm.
Meteorologists call this shortwave radiation, because it is of shorter wavelength than radiation emitted by the earth itself.
The human eye detects light between about 400 and 700 nm. which is called the visible-light waveband. Shorter radiation (200 to 400 nm) is called ultraviolet, and longer
highest intensity occurs near a wavelength of
power contained
radiation, infrared.
Figure 7-3 shows the
This amount
is
weakened on
their
mean annual
solar radiation received at the earth's surface.
well below the areal average solar constant, because the sun's rays are
way down through
the atmosphere.
On
average, the radiation
is
dis-
tributed as follows:
1.
About
\l'/(
atmosphere
The
watt,
per second (J/s).
}6 x
W
s
J.
.i
A
is
absorbed by clouds, water vapor, and carbon dioxide, heating the
directly.
unit ol power,
kilowatt
(kW)
is
the rate
is
I0 3 W.
at
I
« hich energj
is
he kilowatthour
produced, consumed, or transmitted.
is
commonly used
.is
,i
unit
of energy.
Ii
is
It
I
joule
equals
222
Atmospheric Sciences
Chapter 7
1000
Blackbody Radiation, 6000 K
100
E
Blackbody Radiation
a.
300 K
Window
10
1
Wavelength
Figure 7-2
Spectra
of
Adapted from
Source:
solar
(shortwave)
and
(/jvn)
terrestrial
(longwave)
radiation.
Sellers (1965).
Power per unit area (W7m 2 per micrometer wavelength emitted by a black body at 6000 K
and another at 300 K (curve 4), roughly the surface temperatures of the sun and
1
earth, respectively. Other curves have the following meaning; 2, actual power of solar
radiation at the top of the atmosphere; 3, the same at the base of the atmosphere; 5, power
radiation passing directly from the earth's surface to space, showing atmospheric window.
)
(curve
2.
)
About 30%
is
reflected
back
to space
of
from clouds (which accordingly appear
white to an observer on a spacecraft) and from atmospheric gases or particles.
3.
About 53% reaches
the ground.
About two-thirds of
sunlight, capable of casting shadows.
the sky and the gray of a cloudy day.
The remainder
this is in the
is
diffuse
—
form of
direct
the blue light of
Sec. 7.3
223
Energy Outputs and Inputs
Figure 7-3
Average annual solar radiation on
a horizontal surface at
M. Budyko, The Heal Balance of the Earth's Surface,
D.C.: U.S. Department of Commerce, 1958).
The
varies
mean
actual
from about 250
intensity (averaged over
W/m
Obviously,
subpolar areas.
2
is
it
near zero
in clear
To accumulate
area of 6 to 8
m
2
per unit area and
kW
1
even
,
is
mean
when
if
the sun
W/m
2
)
perfect absorption
is
is
80
at
ground
W/m 2
is
W/m 2
on a 24-h
therefore necessary to collect
achieved.
needed
in
level
cloudy
nearly vertically over-
if
it
basis.
over an
Solar radiation has low power
thus expensive to convert for high-temperature uses.
tors as well as extensive storage capacity are
Sonne:
).
are observed for short peri-
values are close to 130 to 160
it
:
and day values are considerably
at night,
weather,
of solar power,
(W/m
24 h) of solar radiation
head, values approaching the solar constant (1368
ods. In midlatitude areas,
level
in subtropical deserts to as little as
At times
higher than average.
ground
translated by N. S. Stepanova (Washington,
the energy
is
Large collec-
to be
used as heat.
7.3.2 Terrestrial Radiation
Year
in
and year out the sun goes on heating the
remains almost the same.
ergy back to space.
much
like a
at
can only do
blackbody with
body emits energy
is
It
at
a
diation.
whose temperature nevertheless
by means of
radiation.
The
earth's surface acts
At such a temperature, a black-
wavelengths between about 4000 and 50,000 nm.
Clouds also radiate
The necessary
this
temperature of 288 K.
almost exactly 10,000 nm.
earth.
earth,
Therefore, the earth must be sending the same amount of en-
return
Thus
like
How
to
terrestrial radiation is often called
Peak
intensity
longwave ra-
black bodies and are only slightly cooler than the
space takes the form of longwave radiation from
the earth's surface or (b) the atmosphere, especially the tops of clouds.
(a)
224
Atmospheric Sciences
The atmosphere
much
is
most of
chiefly transparent;
its
Chapter 7
gases neither absorb nor emit
radiation, with three important exceptions:
Water vapor (H 2 0) absorbs and emits radiation very strongly between 5000 and
7000 nm and above 17,000 nm.
1.
Carbon dioxide (C0 2
2.
absorbs and emits strongly near 4500
)
nm
and above 13,500
nm.
Ozone (0 3
3.
Thus,
in
absorbs and emits near 9,600 nm.
)
weather there
in cloud-free
is
a gap or
which longwave radiation emitted by the
space.
H
In addition, the gases
wave bands
An
listed.
longwave radiation
C0 2
0,
,
and
satellite
that has originated
By
earth's surface.
2
observer or
"window" between 7000 and 13,500 nm
earth's surface or clouds escapes freely to
3
send radiation upward to space
looking
from various
the right choice of
levels of the
In this
its
Movies of
sees
way,
in the
upcoming
atmosphere or from the
level
intensity can estimate the temper-
satellites
night and can identify clouds and measure their heights.
can also be measured.
at the earth
waveband, the observer can identify the
from which the radiation comes, and by means of
ature of the emitting layer or surface.
down
can scan the earth even
at
Vertical profiles of temperature
made from satellite data
The longwave absorption and
of making the escape of energy
the motion of clouds can be
of both reflected visible and longwave emitted radiation.
emission by these gases and by clouds have the effect
to space
more
difficult than
gases and clouds
is
it
would be
in a clear,
greenhouse
otherwise would be.
often called the
about 33 °C warmer than
it
dry atmosphere.
This action by the
makes
the earth's surface
effect.
It
7.3.3 Surface Radiation Balance
The
rate of net radiative heating or cooling at the earth's surface
ure this quantity.
It is
the
is
called the net radi-
Instruments called net radiometers are available to meas-
ation, or radiation balance.
sum
of
all
the gains and losses of radiant
power
at the earth's
surface (see Figure 7-4), given by
R„
=
Terms:
where
=
/ =
a =
Rl =
o =
/?„
T —
e
=
net radiation
(W/m 2
-
I(\
a)
+ Rl - ear4
(1)
(2)
(7.2)
(3)
)
solar radiation at surface
(W/m 2
)
albedo for shortwave radiation (dimensionless)
downward longwave
(W/m)
radiation from atmosphere
Stefan-Boltzmann constant (5.67 x 10
8
W/m
2
•
K4
)
temperature of the surface (K)
emissivity of surface (ratio of actual to blackbody radiation) (dimensionless)
Sec. 7.3
225
Energy Outputs and Inputs
Convective Fluxes
Radiative Fluxes
Figure 7-4
Surface heat balance.
Radiative heating and cooling include:
/,
the incoming solar (shortwave) radiation
-a/, the fraction of
eof4
,
/
back unused
reflected
the longwave radiation leaving the surface
R[. the longwave radiation back from the
air
(from
C02
.
H2
vapor,
3
,
and clouds)
Convective heating and cooling include:
H, the flux of sensible heat (usually
upward) due
to
eddies
LE. the flux of latent heat, also due to eddies, associated with evaporation or condensation at the surface
G, the flux of heat into and out of the
A
plus sign
unit area) are
soil,
due
means an energy gain
primarily to conduction
Since
at the surface.
measured or computed with respect
all
fluxes
(i.e.,
power per
to a horizontal surface, they
can be
thought of as vertical energy transfers.
Term
(1)
on
the right-hand side of the equation
is
with a the albedo, the fraction of the solar radiation that
albedo depends on the nature of the material
usually exceeds 0.8, and water
Term
(2),
R[,
is
the
is
is
the
or water).
in the
Typical values
range 0.1 to 0.3.
warming of
longwave radiation from
the surface due to the
It
is
usually smaller than
[term (3)], the escape of longwave radiation from the surface, so that the
longwave gains and losses
almost as blackbodies
at
is
Snow
well below 0.1.
clouds, water vapor, carbon dioxide, ozone, and aerosols.
ea74
absorbed solar radiation,
The surface
reflected back.
(e.g., soil, plants,
Most land surfaces have albedos
are given in Table 7-2.
the
usually a net cooling.
these temperatures; that
according to the Stefan-Boltzmann law.
is,
Most
natural materials radiate
they emit energy
at a flux
However, actual losses are normally a
than blackbody values, with the emissivity £ usually in the range 0.90 to 0.98.
sentative values of e are given in Table
7-2
also.
sum of
of
aT4
bit less
Repre-
226
Atmospheric Sciences
TABLE
7-2
Chapter 7
RADIATIVE PROPERTIES OF NATURAL SURFACES
Albedo,
Emissivity (all-wave),
a
£
Remark
Surface
Dark, wet
Soils
0.05-0.40
0.90-0.98
0.20-0.45
0.84-0.91
0.16
0.90
0.26
0.95
0.18-0.25
0.90-0.99
Light, dry
Desert
Long
m)
Short (0.02 m)
Grass
(1.0
Agricultural crops
and tundra
Orchards
—
0.15-0.20
Forests
Deciduous
Leaves fallen
0.15
0.97
Leaves on
0.20
0.98
0.05-0.15
0.97-0.99
Small zenith angle
0.03-0.10
0.92-0.97
Large zenith angle
0.10-1.00
0.92-0.97
Old
0.40
0.82
Fresh
0.95
0.99
Sea
0.33-0.45
0.92-0.97
Glacier
0.20-0.40
Coniferous
Water
Snow
Ice
Source:
Example
Oke
(1978).
7.1
Rn
Calculate the net radiation
•
Incoming solar radiation
=
• Albedo of surface, a
•
under the following conditions:
Emissivity, e
=
Downward longwave
Solution
From equation
Rn =
=
=
Each of
midday,
=
/
1000
W/m
2
0.20
0.95
T
• Temperature of surface,
•
at
=
K
300
radiation from atmosphere,
R
I
=
250
W/m
2
(measured)
(7.2),
100(1
-
0.2)
800
+
610
W/m
250
+
250
-
0.95 x 5.67 x lO" 8 x 300 4
- 440
2
the streams of radiation varies daily and annually; therefore, so does R„.
Figure 7-5 illustrates a typical
summer
day's radiation, with
its
wide
variation.
In-
cluded are the following:
1.
Solar radiation
is
near zero
at night.
returns to zero just after sunset.
sun
is to
vertical at
noon
The
It
rises to a
peak near local noon, and then
total daily influx
(a function of season
and
depends on how close the
latitude).
It
is
readily meas-
Sec. 7.3
227
Energy Outputs and Inputs
Warming
Cooling
Figure 7-5
Energy exchanges over short
1971. Source:
Oke
grass.
Matador. Saskatchewan, July
The curves are
and
fl;, the
radiation (a
30.
(1978).
typical of a clear, sunny day. The surface is heated by
the solar radiation,
longwave radiation from the atmosphere. It is cooled by al, the reflected solar
is
/,
the albedo),
longwave exchanges vary
and by eaT"4 the longwave
during the 24 h.
,
urable.
Albedo can also be determined quite
coming
radiation
reflected back.
easily,
simply by measuring the
and then reversing the instrument
The
Note that the
radiation emitted.
little
ratio
to
in-
measure the sunlight
of outgoing to incoming radiation gives the albedo.
Longwave heating from the atmosphere and longwave cooling of the surface are
much more difficult to observe. They are usually calculated from measurements
of
air
temperature and humidity.
Unlike solar radiation, they vary rather slowly.
Usually, they add up to a cooling both by day and by night.
heating by the sun offsets the net longwave cooling, but
control.
Temperature
falls until
dawn.
at
During the day the
night the latter
is
in
228
Atmospheric Sciences
A
3.
considerable variation in the amounts of
An
weather changes.
is
caused by
overcast sky, for example, largely prevents longwave cool-
because downward longwave radiation
ing,
the types of radiation
all
Chapter 7
So
clouds also reduce solar radiation.
is
The
strong during such conditions.
and cloudy days have quite different
clear
temperatures.
7.3.4 Energy Use at the Surface
How
A
the energy of equation (7.2) used?
is
We
1-4) provides the answer.
R„
- G=
H + LE + MS + Q
(heat gained)
Rn =
where
G =
H =
=
Q —
M=
L,
(W/m 2
)
(W/m 2 )
into soil (soil heat flux)
due to upward flux of heated eddies (turbulent heat
loss of heat
flux)
)
evapotranspiration of water (evaporation plus transpiration through plant
tissues)
5
by conduction
loss of heat
(7.3)
(heat used)
net radiation, as in equation (7.2)
(W/m 2
E =
simple heat balance equation (see Figure
have
(kg/m 2
s)
snowfall to be melted (kg/m 2
•
s)
energy conversion by photosynthesis
latent heats of vaporization
in
green plants
(W/m 2 )
and melting (fusion) of water and
ice (nearly
constant at 2.44 x 10 6 and 3.33 x 10 5 J/kg, respectively)
Heat flows into and out of the
measured by
upward
strong and
soil
mainly by conduction
soil heat flux transducers.
other times.
at
It
The
flux
Rn
).
garded as a small reduction of the net radiation [which
(7.3)].
The even smaller geothermal heat
be ignored except
The
in
H
and
LE
is
is
is
any
usually ignored, or else re-
why
from the
it
appears on the
left
of
earth's interior can also
— G)
is
the heat source for the processes
on the right-hand
are the sensible and latent heat fluxes, respectively, that are carried to
movements
MS
flux
It is
is in
These are as follows:
and from the surface by turbulent eddies
2.
that is readily
solar heating
volcanic areas.
net heating (R n
side of equation (7.3).
1.
G
tends to vanish over a day or a year and
case small (of the order a tenth to a hundredth of
equation
at a rate
downward when
is
typical of
the heat needed to melt snow.
snowfall as
much
as
in the
wind
—
the gusts and
up-and-down
windy weather.
10%
This
is
usually small, but in regions of heavy
of the annual net radiation influx
may
be used
in this
way.
3.
Q
is
the very small
amount of heat used by green plants during the manufacture
It is rarely more than 1% of the net radiation.
of tissues by photosynthesis.
Wind,
Sec. 7.4
Example
A
7.2
typical
summer
— 10 W/m
:
value of net radiation by day
Hence
.
Photosynthesis,
5
H
85
Latent heat due to evapotranspiration.
tant role in
The
In
:
and of the
soil heal
LE
400
W/m
W/m
W/m
ratio
HILE
called the
is
cold or dry conditions
it
is
Mux
is
soil, typical
2
:
:
however, most of the available heat will produce sensible heat
If the soil is dry,
about 0.21.
W/m
+500
is
Q
Sensible heat How.
evaporation.
is
490 W/m-. Over a moist, plant-covered
equation (7.3) would be as follows:
net heating
values of the other terms in
7.4
229
and Turbulence
Stability,
Bowen ratio. In this example
much higher. The Bowen ratio
it
is
flux, not
85/400, or
plays an impor-
hydrology and climatology.
WIND, STABILITY, AND TURBULENCE
7.4.1 Motion of the Lower Atmosphere
If air
is
moves
set in
1.
we
relative to the ground,
motion
feel
it
or see
it
as
wind
—
just air in motion.
It
accelerated) by a series of forces:
(i.e.,
The pressure gradient force tending
to impel air
motion from areas of high
to ar-
eas of low pressure.
2.
Gravitation,
which tends
accelerate
to
the
air
downward
at
a
rate
close
to
9.8 mis-.
3.
Friction, acting opposite to the wind direction and proportional roughly to the
4.
The
square of the wind speed.
Coriolis force, caused by the rotation of the earth, often called the deflecting
force of the earth's rotation.
It
proportional to the wind speed.
isphere and toward the
In practice, the
left in
wind tends
thus acts toward the right in the northern
the southern hemisphere
speed or direction) relative to the earth.
usually be in balance; that
blow with constant
is,
velocity.
(i.e.,
no change
Newton's second law says that
plied, a proportional acceleration will occur.
there can be no forces acting.
(when viewed from above).
blow with constant velocity
to
wind direction and is
hem-
acts at right angles to the
It
It
follows that
if
there
is
if
in either
a force
is
ap-
no acceleration,
Since the preceding forces do exist, evidently they must
they cancel one another.
In
Only
way can the wind
moves under balanced
in this
other words, the air usually
forces.
We
can see
the atmosphere.
it
this
It
is
if we consider a unit kilogram of air somewhere in
downward at 9.8 m/s 2 by gravitation. Yet, in practice,
same level. Thus the downward gravitational force must be
most readily
accelerated
usually remains at the
balanced by an equal and opposite force or forces.
Actually, the
upward pressure
gra-
230
Atmospheric Sciences
Pressure (Force per Unit Area) Due
of Air above z+ dz
Chapter 7
Weight
to
z+dz
p-dp
gpdz
dz
Height
Pressure
P
m
1
Figure 7-6
pressure
z
+
Hydrostatic equation: variation of pressure with height.
—dp due
which
dz,
2
to the layer
#p
is
The pressure
dz.
The decrease
dz reflects the weight of the 1-m 2 column between
at level z is
/>
due to the weight of
all
z
in
and
such layers
above.
client
of thin slabs
gp
Atmospheric pressure
force does the balancing.
weight of the overlying
m
1
where g
dz,
any level
2
is
in
m/s 2 p
,
is
is
the density in
sum of weights of
tributes
its
mass so
balances the
in air at rest is
due simply
consider the air column to be
all
j:
is,
by
definition,
z is the height in meters.
At
HP dz
the layers are above the level
that the
downward
kg/m 3 and
to the
made up
given by
P
the
we
If
area and dz meters thick, the weight of each slab
9.8
the pressure
z,
(Figure 7-6).
air
upward
thrust
due
acceleration of gravity.
The atmosphere
z-
at rest dis-
to the decrease of pressure with height
This
is
expressed by the hydrostatic
equation
dp
= —gp
dz
(7.4)
Solving equation (7.1) for p and substituting into equation
p
which can be used
range of heights.
Usually,
we
we can
feel
tionless
motion
=
=
V =
co
<|)
get
dZ
(7.5)
p is the same in all directions.
mean the horizontal movement of air, which
The balance of forces for steady, straight, fric-
hydrostatic pressure
restrict the
word wind
to
expressed by
2co
where
RT
we
to set altimeters or to calculate pressure differences over a small
The
on our faces or our backs.
is
-
(7.4),
sin(j)
pVg
rate of rotation of the earth (7.3
x
dp
dn
(7.6)
L0~ 5 rad/s)
latitude
wind
velocity, parallel to isobars (lines of constant pressure)
m/s
Wind.
Sec. 7.4
=
dpldn
pressure gradient
n
(i.e.,
rate of
angles to isobars)
at right
231
and Turbulence
Stability,
change of pressure p with respect
(N/m 3
In this case, the pressure gradient force per unit
force, the term
ity
VH which
,
on the
is
enough
just fast
The
of equation (7.6).
left
to
make
wind, an idealized wind
1000
m
Figure 7-7 shows
N/m 2 /10 6
balanced by the Coriolis
magnitude to the
Equation (7.6) defines the geostrophic
that is quite close to the real
how
wind
heights from
at all
600
to
since hypothetically
preceding value
In other words, to
in
At point P, using the distance scale we
mbar/1000 km, which is equal to 15 x 10 2
the balance works.
15
at
The wind blows along
m.
its left,
insert the
ample.
is
above the ground.
can estimate the pressure gradient
sure on
mass
flows along the isobars at a veloc-
air
the left-hand term equal in
pressure gradient term on the right-hand side.
to distance
)
we
the isobars at a speed
we
equation (7.6),
make
Vg
,
keeping the low pres-
are dealing with the northern hemisphere.
get V^ «s
20 m/s
at
30°
If
we
latitude, for ex-
the deflecting force equal and opposite to the pressure
gradient force, the wind must blow along the isobars at 20
m/s
in the
case shown in
Figure 7-7.
We
can, of course, easily measure the
wind by tracking
mounting a wind vane with a speed sensor attached.
pressure by
their
means of
But
it
is
floating balloons or
Hence weather maps use pressure distribution as
is measured simultaneously at thousands of stastandardized to sea level using equation (7.5), and then
a barometer.
main indicator of wind.
Pressure
tions worldwide, the values are
Pressure (mbar)
1000
PGF
1
p
—f
Plan Showing Horizontal
v
,
9
>
1005
I
Balance of Forces above
ground at 600 -1000 m
cf\
1010
1000
PGF
Plan Showing
p
'
y\^--
F.^f
*
i
w
*
*
V
1
° 05
A
Balance of Forces
at Surface
500
11111111111
1000
i
Figure 7-7
by
even easier to measure
Distance (km)
1010
Relation of wind lo pressure
in the
horizontal plane.
232
Atmospheric Sciences
the isobars are
drawn
The
in.
resulting
of wind as well as of pressure.
map
is
a
good approximation
Chapter 7
to the distribution
Equation (7.6) allows us to calculate wind speed, the
isobars being roughly streamlines.
how wind
Figure 7-7 shows
At 600
stant pressure.
related, in an idealized fashion, to isobars of con-
is
1000 m, the wind flows along the isobars
to
a speed V„ (the
at
geostrophic wind) that makes the Coriolis force (CF) equal and opposite to the pressure
At
gradient force (PGF).
the surface, friction (F) with the
so that the Coriolis force
To balance
ground slows down the wind,
decreased and no longer balances the pressure gradient
is
wind turns across the isobars (lower diagram) so
The angle of the
surface wind Vs to the isobar is on the order of 40°, and the speed is about half that of
the geostrophic wind V
Between the two levels, as one ascends, the wind increases
g
force (PGF).
that
CF
F
and
the
PGF,
the
PGF
together balance
(see the parallelogram of forces).
.
and turns toward the
The wind arrow
isobar.
point traces out a spiral curve on the
up (see the lower diagram, where a sample midlevel wind
is
The system
shown).
way
is re-
versed in the southern hemisphere.
On
real
weather maps the isobars are rarely
straight.
maps show
Instead, the
oval
or circular areas of high and low pressure hundreds or even thousands of kilometers
across.
The
free air flows clockwise along the isobars of a high-pressure
system (an
anticyclone), and anticlockwise in a low-pressure system (a cyclone).
This rule for the
Even though isobars
are in fact curved
northern hemisphere
reversed in the southern.
is
and the wind thus changes
in
its
direction, the speed
close to the geostrophic value
is still
most cases. Anticyclones and cyclones represent gigantic horizontal eddies
They migrate
mosphere.
Near the equator the
clones) weather.
in the at-
them fair (anticyclones) or foul (cybetween wind and pressure breaks down
slowly, bringing with
relation
and pressure differences are small (because the Coriolis force
is
zero
at the equator).
7.4.2 Turbulence and Stability
The
rules just described allow
both organized motion, which
or turbulence, which
is
many
is
kinds of motion.
In practice
we
think of
wind
as
described by equation (7.6), and unorganized motion,
not described by that equation.
Both organized winds and
tur-
bulence are important environmentally because they transport water vapor, carbon dioxide, heat,
in
and pollutants.
In this section
bringing about vertical transport.
discussed
and
in
Chapter
13.
It
is
It
we
is
look
at
turbulence, which
very important
in the
is
most important
study of air pollution,
also crucial in the design of buildings, aircraft, bridges,
other structures exposed to the wind.
The gusts and eddies
in turbulent air
cause
the worst stress that these structures have to withstand.
In the
occurs
atmosphere, turbulence
is
of two kinds, forced and
free.
Forced turbulence
when wind encounters obstacles, as it always does at the earth's surface. Free
when the atmosphere encourages the growth of small initial distur-
turbulence develops
bances.
Usually, this
is
because the motion releases buoyancy.
lence occur near ground level as well as in the higher layers.
convection as
it
the atmosphere.
is
better called,
In
Figure 7-1
is
Both kinds of turbu-
Free turbulence, or free
encouraged by certain distributions of temperature
we
in
see that temperature in the troposphere usually de-
Wind.
Sec. 7.4
creases with height
dTId:
(i.e.,
is
or forced,
ing
its
K
falls
If a
and the volume expands. Work
This leads to a cooling of the rising
air.
air,
dz
the acceleration
is
due
constant pressure (1.0 kJ/kg
•
is
c
to gravity (9.8
air rises, either freely
done against the surround-
given by the equation
(7.7)
p
m/s 2 and cP
)
is
the specific heat of air at
This equation defines the dry adiabatic cooling
K).
The word adiabatic means
rate, valid only as long as condensation does not occur.
"without communication of heat." signifying that the change of temperature
energy conversion, not
Since g and cp are almost constant, dTldz
loss.
K/ km. Air becomes buoyant
at 9.8
with height
at a rate
exceeding
if
is
is
due
to
also constant
is
the temperature in the surrounding air decreases
when
This usually happens during the day
this figure.
Hence buoyant convection near
the sun heats the ground, rather than at night.
ground
usu-
It is
=_ L
41
where g
bubble or slab of
defined
is
one ascends through the atmosphere.
per kilometer of ascent.
pressure
The environmental lapse rate
negative).
as the rate of decrease of temperature as
ally close to 5
233
and Turbulence
Stability,
the
largely confined to the daytime.
moist and becomes saturated as
If the air is
heat of vaporization
is
released into the ascending
typical cooling rate for saturated air
4
is
values of the environmental lapse rate.
of the atmosphere
—can
it
ascends, a cloud forms.
air,
which then cools
K/km. which is quite
Hence rising saturated air
to 5
air,
latent
A
similar to the usual
—
usually ascend farther than can dry
The
less rapidly.
the cloud systems
because
it
remains
buoyant longer.
Stability
may
to
grow.
the condition in the air that tends to
is
be present.
Instability
For unsaturated
Saturated air
ble.
is
air,
is
the opposite
—
damp down any
convection that
the condition that encourages convection
K/km
an environmental lapse rate of less than 9.8
stable if the environmental lapse rate
is
less than the
is sta-
reduced cool-
ing rate in the ascending currents.
The preceding
In the early
relationships are visible on
morning, the
air is stable
most sunny days
and the sky
is
in the
As
cloudless.
ground, however, the environmental lapse rate increases rapidly,
with lapse rates greater than the dry adiabatic cooling rate (9.8
Figure 7-8).
km
deep.
clouds
This layer
is
turbulent,
and as the day progresses,
Flight in light aircraft in this layer will be very
may form on many
heights, especially
if
until a
ground, very cool above
1
may
If the air is
rise to
— they
may
moist,
considerable
—
rise far
above the freezing
clouds (see Figure 7-12), from which heavy showers originate.
however, the solar heating
level.
at
ground
level ceases
The cloud tops
cumulonimbus
As evening
progresses,
and conditions become more stable
The clouds stop growing and then disperse. Nocturnal thunderstorms, common
humid air masses, especially in the Great Plains of the United States, also reunstable conditions, but in this case a different mechanism triggers them.
very
quire
(see
or 2
is cool.
The cauliflower-head-like cumulus
Under very unstable conditions warm near the
then spread out to form the familiar anvil-shaped thunderheads called
in
shallow layer
the upper troposphere
clouds mark such rising columns.
again.
seasons.
K/km) is created
it may become
bumpy.
of the ascending thermals and then
warmer
the sun heats the
234
Atmospheric Sciences
Negative environmental lapse rates
are
common
lapse rates
is
usually
at night,
is
and
in
winter
may
Chapter 7
an increase in temperature with height)
(i.e.,
The top of
persist all day.
the layer of negative
Such conditions are very
called an inversion (Figure 7-8).
stable.
Dense fog may be present if the air is moist.
lake waters and may be drawn short distances
of California and
at
many
localities
1000
Inversions often occur over cool sea or
inland.
This occurs in the coastal valleys
along the shorelines of the Great Lakes.
\2
V
\
4\
1
\
\
\
4
\
500
h
03
x
<
.\
°i
^l
>*v
>\
^
\
s\
\.
\3a
2^- ""jC
P
5
10°C
283 K
278
273
Temperature
Figure 7-8
The dry
5
C
Lapse
rates of temperatures in the
adiabatic cooling rate of 9.8
(278
K).
Air rising
K per 1000
from the ground
will
boundary
m
is
layer.
shown
for air at
cool at this rate unless
it
10
is
C
(283 K) and
saturated.
Curve
shows conditions typical of midday hours with strong heating. Heated air at point P will
rise and cool along dashed curve 4, whereas the actual temperature of the surroundings,
as measured by actual sounding (curve 1), is colder, because the environmental lapse rate
exceeds the dry adiabatic rate. Hence the rising air will be buoyant, because warm air is
less dense. Curve 2 shows an example of a surface inversion (marked I), with air at 220
m 4 K warmer than at the ground. A second inversion occurs at 450 m. Curve 3 shows
a much stronger inversion at 400 m, typical of dawn, with the temperature at the inversion
7 K warmer than at the surface. Later in the morning, with the sun heating the ground and
1
a wind
stirring
the lower layers, a shallow layer of normal, near-adiabatic lapse rate
—
curves 2, 3, and
Air rising from the ground in any of these cases
3a will soon become colder than its surroundings and will thereby cease to be buoyant.
Smoke, haze, and pollutants are trapped by such inversions.
develops (curve 3a).
—
There
wind, and pollutants emitted into the inverted layer are slow to disperse.
little
Water
Sec. 7.5
7.5
WATER
IN
235
Atmosphere
in the
THE ATMOSPHERE
7.5.1 Humidity and Precipitation
Water has the special property
gaseous, and solid.
that
called a
is
It
it
atmosphere
exists in the
vapor when
in all three
the gaseous phase.
in
water vapor can attain, called saturation.
limit to the concentration that
phases: liquid.
There
At
an upper
is
this limit
it
tends to condense to liquid or solid forms, provided that suitable surfaces exist on
which
this
The saturated vapor condenses on small hygroscopic
can happen.
within the aerosol called condensation nuclei.
forms liquid water
at
nm
in
The water and
ice crystals.
diameter
Only below 233
ice particles are
and remain suspended as cloud or fog.
l
nuclei
atmosphere, condensation usually
temperatures well below the melting point of pure ice (273.2 K);
the droplets are then said to be supercooled.
ways form
In the
K
At ground
also condense as
dew or
when supercooled
droplets freeze on contact with solid surfaces.
hoarfrost.
Rime
is
the
does condensation
al-
very small (usually below 2000
name given
level the
may
vapor
to the clear ice
formed
Saturation vapor concentration depends only on the temperature of the vapor (or
of a plane water or ice surface with which
to
water
in
the
atmosphere
,
is in
it
equilibrium).
vapor pressure
may approach
about 40 mbar (4 kPa) and
pressure over water. es
called the
is
e,
zero in very cold
The
which
air.
partial pressure
always
is
The
due
less than
saturation vapor
given to a good approximation by
is
log 10 «,(mbar)
=
9.40
- 2345
-y-
(7.8)
where T is taken to be the temperature of the air in which the vapor is mixed. Figure
7-9 is the curve oi this function, compared with that for ice below 273.2 K. Note that
there
is
much lower vapor
pressure over ice than over supercooled water.
por pressure increases rapidl) as temperature
ter
\apor becomes saturated
at a
rises.
If
unsaturated air
temperature called the
dew
point.
is
Saturation va-
cooled, the wa-
Condensation then
begins on any suitable surface.
Several other measures are used to express the actual humidity of
pressure e has ahead) been mentioned.
tual
relative
humidity
vapor pressure divided by the saturation vapor pressure
humidity mixing ratio
«
of moist
air.
,.
Some
is
air.
The vapor
the ratio eles
at the air
,
the ac-
temperature.
The
mass of water vapor mixed with a unit mass of dry air,
the mass of water vapor in a unit mass of moist air. The
the
is
and the specific humidity q
absolute humidity a
ume
The
is
vapor density,
or the
is
the
mass of water vapor per
unit vol-
useful formulas arc
I
r
=
-q
p-e
l****
8(/; - e)
,7.11)
236
Atmospheric Sciences
where p
is
the atmospheric pressure in
mbar and
and r are
q, x,
all
Nevertheless, x and q are usefully measured in g/kg, and r
tities.
percentage of saturation
(i.e.,
a relative humidity of 0.7
is
Chapter 7
dimensionless quanis
usually given as a
referred to as 70%).
Because cloud droplets are so numerous, they can easily accommodate increased
in their radius. At these still small sizes, the
condensation with only a small increase
droplets are kept suspended by the turbulence in the
thick clouds.
1.
If the
How
does
this
come about? There
cloud's temperature
is
below 273
droplets are usually dominant.
If
air.
Yet rain or snow often
are at least
K
falls from
two known explanations:
but above 233 K, supercooled water
small ice crystals form in or
clouds, they will be in an environment that
is
fall
into such
supersaturated with respect to ice
Hence they grow rapidly by direct solid condensation. This is
Bergeron-Findeisen process. Eventually, the ice crystals may fall
(see Figure 7-9).
known
m
as the
bar
70
60
50
m
40
Cl>
0_
o
Cl MO
m
>
20
— - ~zl
light
See ile
1.0
10
"""--Left
|
Scale
CO
DC
- 40
- 30
20
-10
+ 10
273
233
+20
+30
+40
deg C
K
303
Temperature
Figure 7-9
Relation of saturation vapor pressure (over a plane water surface) to
temperature (°C and K).
Dashed curve (use
over ice at the
right scale) is the ratio of saturation
same
K), the saturation
temperature.
At
C
vapor pressure over water
(273 K), the two are the same.
At
vapor pressure over water exceeds that over ice by a factor
to that
-40 C (233
of 1.47.
Water
Sec. 7.5
the
in
237
Atmosphere
as snow, often after coalescing with other crystals or with supercooled droplets
when such
superstruts.
on
that freeze
This
As
2.
A
cooled droplets freeze on to leading edges, such as wings, propellers, and
is
to
them.
significant hazard for aircraft occurs
called rime icing.
there are always differences in size
among
droplets and crystals, differences in
velocity lead to growth of the larger droplets
fall
circumstances, the droplets
may grow
Under favorable
by accretion.
to the point
where they can
fall
Typical rain and drizzle have drop sizes in the range 0.5 to 2.5
ground.
Experience has shown that both of the preceding processes are usually
to the
mm.
at
work
in
the cold clouds of middle-and high-latitude rainstorms and snowstorms, in that signifi-
cant
originate in clouds that reach well above the freezing level.
falls
may. however,
fall
from warm cumulus
All significant precipitation
by
clouds
(i.e.,
rain,
marine tropics.
in the
snow, and hail)
Rising moist air cools adiabatically below
uplift.
of clouds are recognized:
(
1
)
Substantial rain
its
falls
from clouds formed
Two
dewpoint.
broad families
those due to slow, slanting uplift, called layer clouds, that
are typical of cooler season cyclonic storms in both hemispheres, and (2) those due to
rapid convective uplift of air
bus clouds.
over mountains.
The
moist
columns
in
called cumulus and cumulonimwhen moist air is forced to climb
shown in Figures 7-10 to 7-12.
unstable
Both of the situations described
Different types of clouds are
air.
exist
layer cloud family includes stratus (usually
air),
altostratus or nimbostratus (rain and
and cirrocumulus (the
thin,
formed when warm, moist
wispy clouds
air rises
snow
common
gradually
formed by surface
chilling of
clouds), and cirrus, cirrostratus,
against the blue of the sky).
(at rates
typically about 0.1
All are
m/s) as
it
moves eastward or northeastward over cooler air, usually in developing cyclones. Such
cloud masses often become thick enough and cool enough to start snowfall via the
Bergeron-Findeisen process. As the snow falls into the lower layers, it melts to rain,
except in cold, wintry conditions. Much of the prolonged rain and snow of the cooler
seasons in middle and high latitudes is formed in this way. The cloud systems responsible
may cover
tens of thousands of square kilometers and be 5 to 8
The cumulus type of cloud,
der of 0.5 to 100
of a
fair
day
to
km 2
in
arising
from rapid
uplift in small
km
the or-
cumulus
typical
height.
These
cross section), ranges from the small puffs of
huge cumulonimbus masses
rising to over
15
deep.
columns (on
km
in
They are the dominant rainclouds of the tropics
and of the midlatitude summer. Thunder and lightning often accompany the heavier
falls.
Cumulonimbus cloud is also common over the warm oceans when cold air Hows
toward the equator. In the most violent of these storms, the rising column of air may
clouds produce short, violent showers.
acquire a rapid rotation about a vortex core with very low pressure.
as they are called, are the
km
across) but
may
most destructive of
travel long distances,
all
storms.
and are unrelated
They
These tornadoes,
are small (less than
to cyclonic storms.
I
238
Atmospheric Sciences
Figure 7-10
Carl Milles"s statue.
Cumulus. Stockholm. Sweden.
The Hand of God.
(Photo courtesy of
F.
silhouetted against fair-weather
K. Hare.)
These clouds form when shallow convection currents carry moisture upward
condensation
level but
Chapter 7
to the
are then stopped by an inversion.
7.5.2 The Hydrologic Cycle
The movement of water hctween
air,
sea. lakes
and
rivers, land, soils, glaciers,
Figure 7-13.
ing organisms forms the hydrologic cycle, sketched
in
used earlier (Figure 6-10) to
in a
balance on
a global basis
is
illustrate a
shown.
water balance
small region.
and
liv-
This cycle was
Here a similar
This movement almost balances out.
Water
is
fci-
Figure 7-11
New
Zealand.
Figure 7— 12
Pacific
Riehl
Stratus (below) and altostratus cloud on a winter's day. Rakaia Gorge.
(Photo courtes>
ol
F.
K. Hare.)
["hunderheads (cumulonimbus clouds)
Ocean between
llav.au
and
Fiji
ol
tropical
(Photo courtes)
ol
I
disturbance over the
S
Simpson and
II.
i
These thunderheads are caused by the convergence
hemispheres over warm ocean surfaces.
of the trade
winds
of the
two
239
240
Atmospheric Sciences
Chapter 7
c22i
Snow
Front
irMass
;.
•
•„
(Cold-Dry) Transpiration
/"^7'Vvr
Ra
'
n
Evaporation
||
|
|
\
Evaporation
|
C -* •& flUx j
Transpiratioj
/
l/l
|
U
|
*™
'
Transpiration
J.
>/'
\
t
"*
\±J±%J>^
t
\
Snow and
A^dsA^^*"^
il
Ice
Moisture
.
Rivers
Soil Moisture
Lakes
Groundwater
Ocean
Groundwater
Atmosphere
0.035% ot All Fresh Water
The
A
Hydrologic
Cycle
£>
Horiz. Advection of
Precipitation Evaporation
100 Units
= Mean
Ann. Global
in
from
Ocean
Ocean
(33.8
cm
in.)
of All
Lands
Runoff
<r
to
Rivers
0.03%
Soil
Oceans
Ocean
Ice
Lakes
Moisture 0.06%
0.3%
Glaciers
Groundwater
(<
2500
ft)
11%
Oceans
of All
Fresh Water
Groundwater (2500 - 12,500
ft)
Storage
Reservoirs
14%
Continents
(Percentages Refer
Figure 7-13
Sheet
and
75%
Water
Qn Lands
from
Surface
97%
p reC jpjtation
transpiration
Precip.
85.7
Evapo-
Water Vapor
Hydrologic cycle.
Source:
to
Fresh Water Total)
Adapted from R. G. Barry and R.
J.
Chorley. Atmosphere.
Weather and Climate (London: Methuen, 1982).
Shown
is
The exchanges in the cycle are given as
(33.8 in.) The percentage storage figures
fresh water. The saline ocean waters make
the hydrologic cycle and water storage of the globe.
percentages
of the
mean annual
global precipitation of 85.7
for
atmospheric and continental water are percentages
up
97%
of
all
water.
of
all
cm
Sec. 7.5
Water
in
the
241
Atmosphere
we know,
chemically active and enters into compounds very easily.
As
chemical exchanges release as much water as they remove.
Overwhelmingly, the main
mass of water
is
far as
oceans, which cover two-thirds of the earth's surface.
in the
shown in Figure 7-13.
cycle begins when evaporation occurs.
these
A
small
part cycles annually through the storage reservoirs
The atmospheric
part of the
place off open water surface and also off ice, plants,
wetted by precipitation.
1.
soil,
Evaporation requires:
An energy source, which is mainly the net radiation at the evaporating surface but
may also be heat from the soil, the turbulent heat flux in the atmosphere (common
when warm air moves over cold surfaces), or heat from warm ocean or lake waThe
ters.
273
K
heat required to evaporate
x 10
to 2.43
6
J/kg
at
kg of water varies from 2.50 x 10 6 J/kg
1
To melt
303 K.
These are very large amounts of
J/kg.
able net radiation
lakes, or
is
may
ice at
On
heat.
273
K
requires 3.33 x
a typical day
much
growing crops (which deliver water
to their leaf surfaces
word evapotranspiration is often used
process, which requires the same energy as evaporation.
ted leaves.
A
Hence
the
sink for the vapor produced, which
transport
it
is
s
soil,
through the
Off a plant-covered land surface, the
be dominant and can rarely be separated from evaporation off the
at
10
of the avail-
used to evaporate water from moist surfaces such as wet
physiological process of transpiration).
2.
This takes
and other surfaces recently
latter
soil or
wet-
for the collective
simply the capacity of the atmosphere to
away, mainly by turbulent diffusion.
Strong winds and unstable lapse
rates favor rapid evaporation.
The measurement of evapotranspiration
is
the evaporation pan. in
which the
mechanically. For turfed, cropped, or base
lated block of soil, in
the percolation
soil, the
difficult.
compute
pans.
is
measured
is
an iso-
the evaporation or evapotranspiration. All such gauges
that unless great care is used, they will
ation and turbulent characteristics from natural exposures. This
procedure
is
lysimeter can be used. This
from the base. Knowing the precipitation into the block and allowing for
from the drawback
oration
The standard instrument
from a confined surface
which grass or crops can be planted, from which one can measure
storage changes, one can
suffer
very
is
loss of water
Except
to rely
at
research
is
have different net
radi-
especially true of evap-
with sophisticated instruments, the usual
stations
A
on semiempirical formulas.
selection of these
may
be found
in
Hare and Thomas (1979). Mather (1974). Oke (1978). and Lins et al. (1990). Over a
wide range of surface conditions and over periods of a day or so, a simple relation between net radiation R„ and evaporation E can be used:
E=
asR n
,
.
L{s
where
"
(7.12)
+y)
= deJdT (mbar/K) from Figure 7-9
y = 0.64 mbar/K
a = a proportionality constant whose value
s
is
near 1.0 over a wide range of sur-
242
Atmospheric Sciences
faces, except under very dry conditions;
fully
with £,
/?,,,
and L, as before (see equation
is
removed, but
the flow of water through plant tissues
The
leaves and stems.
root systems of plants,
soil.
Much
some
availa-
has been stored in the
rainfall that
by plants and released
ble water that can be extracted
is
of 1.26 over
(7.3))
of this water is held too tightly to be easily
which
maximum
moist surfaces
The main source of evapotranspiration
tion,
rises to a
it
Chapter 7
all soils
to the
and
its
which tap the
contain
atmosphere by transpiraloss as moisture through
soil water, are
usually shal-
low, the top meter of soil normally providing most of the evaporated and transpired water.
A
Once
this soil
water
removed, evapotranspiration ceases and plants tend
is
recently wetted soil that contains
water
is
available water but has drained
all its
to wilt.
surplus
said to be at field capacity.
Precipitation and evaporation are normally
is,
all its
measured
in
millimeters of depth, that
snow that would accumulate on or be lost from an imsurface per unit time. The usual SI unit is kg/m 2 per unit time, which is
mm of rain for the same period. Rain and snow gauges simply catch the
the depth of rain or melted
pervious
flat
equivalent to
1
precipitation as
A
it
falls,
and the depth
water balance must exist
[equation 7.3)]
is
the
is
measured and recorded
any point.
at
is
precipitation,
change term indicates
from storage.
Note
annual totals
N
that
it
fixed intervals.
balance equation
E
occurs
is
common
in
storage change
percolation and runoff,
is
may be
kg/m 2 (i.e..
water
All units are
that
at
like the heat
water balance equation,
P=N+ E+
where P
Much
E
(7.
evaporation, and the storage-
is
millimeters of depth) per unit time.
runoff ratio
C =
NIP, which varies from
very dry areas to as high as 0.9 in extremely wet, cool climates.
precipitation that finds
its
way
3)
either stored in plant soil or subsoil or released
both the heat balance and the water balance equations.
to use the
1
into the streams, is the
For
nil
in
Runoff, the surplus
main subject of study of
the sci-
ence of hydrology.
7.6
CLIMATE
7.6.1 World Distribution
Figures 7-14 and 7-15 show the average or expected distribution of precipitation and
temperature around the globe.
We
have good pictures of the distribution of pressure,
solar radiation (see Figure 9-1), temperature, precipitation, wind, humidity, and clouds
at
many
These
levels in the atmosphere, especially
distributions have a long history.
though significant
in
human
history,
below 30
km
(a
pressure of 10 mbar).
For the past 10,000 years climatic changes,
have not been
large.
Before
that,
were many times when the world's climate was colder and drier than at present.
are known when
the glacial epochs
past 2 million years, at least nine phases
—
—
al-
however, there
In the
ice
and
Sec. 7.6
243
Climate
December- February
25
50
100
200
4O0
600
800
1000r
zrzxz;
June- August
Figure 7— 14
World
distribution
oi
precipitation
Geographische Mitteilungen, 95 Jahrgang, 1951,
Mean
global precipitation
(mm)
for the
(annual
pp.
mean).
Source:
I
M811er,
1-7.
periods December-February and June-August.
Petermann'
244
Atmospheric Sciences
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Chapter 7
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60° 40°
100° 80°
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100° 120°
80°
160° 180°
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Figure 7-15
120°
100*
World
80°
—
Mean
^yl^.-*
•
l
'
,
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*—
/
/
/ j^
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40°
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20°
40°
Se^?-~^Z-/
LL:>^XS
60°
80°
-I'yi'yy .yijiro.
100°
120°
140°
distribution of temperature (January and July means).
sea-level temperatures
shown by dashed
20°
line.
in
y->,—f-y
7*
1
9^35*
60°
/
/
yL
/
/
4-— s-|
+^3^?
R. S. Chorley, Atmosphere, Weather
are
"^/^-.
/
i-io
1
-a^J.
j
N
SN-^V
1
/
""
L^LA
/
1
—
WM
V iTp
and Climate (London; Methuen,
January and July
(
C).
The approximate
-
.
l,.lv
v
160° 180°
Source: R. G. Barry and
1982).
positions of the thermal equator
-
245
Climate
Sec. 7.6
snow were more widespread than now. Other glacial ages occurred in the remote past,
one of them 650 million years ago. Thanks to much geophysical and geochemical work
on the sediments of the deep oceans, we now have a detailed knowledge of the most reSince rapid fluctuations of climate
cent age of glacial epochs, the Quaternary period.
characterized this period,
it
is
Can
natural to ask the question:
the present climate
change?
The fundamental controls of climate
which influences tem-
are the solar constant,
perature on earth; the composition of the atmosphere; the distribution of land, sea, and
mountains; and the rate of the earth's rotation.
All these have changed over the long
history of the earth but, with the possible exception of the atmosphere,
now seem
rela-
tively stable.
7.6.2 Climatic Variability
Despite the stability of the climate-controlling factors,
(Schneider 1989).
year by as
much
Surface
±
as
K
ground warming of 0.6
erable
economic
member
that climate
is
inherently variable.
Present practice
years.
1961-1990
is
are, they
To define
rainfall, etc.)
fluctuations,
climate,
we
currently in standard use.
From
it
is
important to re-
average the values for
over some arbitrary period, usually 30
to recalculate these averages every
is
have consid-
in precipitation in
1994).
meaning of such changes or
element (temperature,
a particular
however, there has been a slow back-
Small though these changes
There have also been significant changes
et al.,
In addressing the
direct evidence of
temperatures averaged over the world vary from year to
In the past century;
(a trend).
effects.
some regions (Boden
air
0.5 K.
we do have
which good records are available
fluctuations of climate during the past century, for
this
10 years.
average state
we
The
set for
recognize the
fol-
lowing:
1.
Periodic variations with various periods.
warm days and
daily variations (e.g.,
tions (e.g..
warm summers and
The only common ones
in climate are
cold nights) and seasonal or annual varia-
cold winters).
Most other periodic
variations ("cy-
cles") allegedly found in climate turn out to be spurious.
2.
Quasi-periodic variations, where a few years of high values are followed by a few
years of lower values but without any regular period.
3.
Upward or downward
4.
Impulsive changes of central tendency,
trends, in
which the element slowly
in
rises or falls.
which the mean value changes suddenly
to a nev,. stable level.
5.
Short-period variations, without apparent pattern, resembling "noise" cluttering a
radio signal.
ena as
These include the familiar weather changes but also such phenom-
warm and
cold or wet and dry years.
Climatic change occurs only
cessive averaging periods.
if
there
The changes
is
a statistically real difference
between suc-
that occur within an averaging period are called
246
Atmospheric Sciences
the variability of climate.
erage values.
Good measures
Chapter 7
of this variability are as important as the av-
and engineers, dealing with climate-related environmental prob-
Scientists
lems, need at least the following information:
1.
Good
averages, such as
mean monthly and
annual, temperature, rainfall, and solar
radiation.
2.
Some measures
of variability.
and extreme values
data,
These can include standard deviations, frequency
likely to recur every
decade or century.
Data on return
periods (probable intervals between specified values) are also needed, especially
by the
3.
Some
civil
engineer and hydrologist.
estimate of future trends, or impulsive changes.
tant to civil engineers
and agricultural
This
is
especially impor-
scientists, but also affects heating
and ven-
tilating specialists.
Most national weather services can provide up-to-date data of these kinds. Estimates of
come by. They form the main subject
of research in modern climatology.
The art of climatic modelling has become the key to an understanding of climatic
change. The word "art" is deliberately chosen, since the methods go beyond pure scifuture trends and changes are, however, harder to
ence.
Science enables us to write
down
the full set of differential equations that express
the laws and approximations set out in the previous sections,
and
to apply suitable con-
stants
and boundary conditions, such as the acceleration of gravity,
earth,
and the
set
fact that matter
of equations
is
rate of spin of the
can be neither created nor destroyed.
only solvable on the largest mainframe computers
But the resulting
—and then only
if
good approximations can be made, and wise choices of computational technique chosen
which involves the judgement and skills of the operator; hence the word "art".
The models used often inspired guesses or deductions as to what would work
best
were originally developed to improve global weather forecasting, much needed
when intercontinental aviation became a commonplace. As interest in climatic change
grew, the models were altered so as to make them able to simulate outcomes over much
longer periods, which in effect arc climate. In addition, use was made of much simpler
—
—
—
models
to try out
hypotheses such as the greenhouse
effect, the radiative
changes
fol-
lowing from pollution, and the transport of pollutants such as the sulphur and nitrogen
oxides that cause acid deposition (see Chapter
5;
also
Houghton
et al.,
1990;
IPCC
1990; Hengeveld, 1991; Mintzer. 1994; Atmospheric Environment Service. Environment
Canada, 1994).
7.6.3 The Climatic System
Climate interacts with
system
is
soil,
rock, plants, animals, surface water, and ice.
the climatologist's
by which they mean
physical environment.
name
for this interaction.
the relation of living organisms and
Whichever term
is
The climatic
Biologists talk of ecosystems,
communities
to their total
used, one must try to see the linkages.
It
is
247
Climate
Sec. 7.6
exchange, disturbance, recovery, and lasting change within these systems that are
who
Environmental engineers and scientists
root of environmental science.
things are interconnected court environmental disaster (sec also Chapters
Our climate and the oceans are closely linked.
particles are
exchanged between sea and
air at
The
deep.
much
prodigious rates.
deeper ocean waters are largely isolated
1000 years
as
to
Actually,
much
be
amounts of
most of the
100
from the atmosphere, taking as
exchange water and materials with
heat.
16).
surface, a layer less than
Ocean
ocean surface.
the
They
currents are in part driven by the winds, which exert a powerful drag force.
port large
the
Water, energy, carbon dioxide, and
exchanges take place within the water layer near the ocean
m
&
1
at
forget that
trans-
Without such transport, world temperature contrasts would
greater.
Similar links exist between climate and the great continental glaciers that cover
Greenland and Antarctica.
For many millennia, much of the snow that has fallen on
which now lies several kilometers deep
The sun and atmosphere are unable to deliver enough energy
Antarctica discharges most of its surplus ice into the ocean as gigantic
these land areas has accumulated as glacial ice,
over their central areas.
to melt the ice.
bergs or floating shelf
ice.
Greenland loses about half
and the other half as icebergs
that drift
its
annual surplus as meltwater
down toward Newfoundland.
In
each of the gla-
America and
9000 years ago. But
there is little prospect that the predicted warming of climate in the next century will do
m in
likewise for Greenland and Antarctica. Sea level is unlikely to rise more than
cial
epochs of the Quaternary period, similar
northern Europe.
Remnants of
the
sheets covered North
ice
most recent vanished 6000
to
1
the next century, because any marginal melting of the ice will be
in part,
compensated,
by increased snowfall on the upper slopes of the glaciers.
fully or
Melting of sea
ice
leaves the sea level unaffected.
7.6.4 Urban Climates
Engineers do
much
of their work in cities or heavily industrialized areas.
of such areas differ from those of open country in
tion (dealt with in
Chapter 13)
see Landsberg (1981) and
Oke
is
mainly found
(1978).
many ways.
in cities.
The climates of
The climates
Also, serious air pollu-
For more complete reviews
cities are
modified by several
factors:
1.
Cities are rougher than
open country, so
that
more turbulent by contact with obstacles such
2.
as buildings or
power
cities are quite unlike natural soil or vegetation.
many tall concrete,
pumps much water into
much of the area.
brick, or steel
In
the city, the heat
countryside.
The
structures.
is
is
absent over
and water balances are changed from what they are
lots,
There
Vegetation, which in nature
the atmosphere, keeping the plants cool,
buildings, streets, parking
made
lines.
The surface materials of
are
3.
wind flowing across them
ami industrial plants of
have quite different properties from open countr) as regards
in the
a cit)
(a) storage o\' heat.
248
Atmospheric Sciences
(b) storage of water, (c) absorption
the hydrologic cycle,
(i.e.,
of solar radiation, and (d)
all
Chapter 7
components of
evaporation, percolation, runoff, and water storage).
4. In addition, cities release a great deal
of heat to the atmosphere from furnaces, au-
tomobiles, and other fuel-consuming activities.
A
direct
consequence of these factors
is
quite unlike that over the surrounding country.
The modified boundary
than by night.
boundary layer over a
that the
city is
Figure 7-16 depicts the main effects.
layer over the city forms a sort of
dome, which
higher by day
is
At night a strong inversion may occur, trapping the pollutants.
Most of
dome, although some is carried off by the
of water and energy in Figure 7-16 carry the same symbols
the pollution released by the city stays in this
wind. The various transfers
as in the heat
and water balance equations, (7.3) and
(7.13).
The main
differences are
that:
Day
Rural
+-
-+•
R
Wind
Direction
V
Urban
,<--v.
\
•^
"N,
s_2Lc!
Night
-+
Wind
Rural
Urban
Direction
H
"O
Figure 7-16
Urban boundary layer by day and
Schematic representation
uncertain.
R„
=
Dashes
net radiation;
of the
indicate
H
urban and
dome
of
rural
F=
photosynthesis by green plants (day only);
Sonne:
heat balances.
urban boundary
and LE are convective
out of buildings, ground surfaces, etc;
night.
Oke
(1978).
Directions of
H
and LE
fluxes of sensible
and
latent heat;
G=
flux of
heat generated within buildings by vehicles;
A =
at night
are
layer.
advection.
All
units
W/m 2
.
heat into or
Ph = heat used
in
1.
During both day and night there
which
2.
249
Climate
Sec. 7.6
The
is
due
to the use of fuel
is
an extra heat source
and mechanical energy
in the city,
in buildings
strikes
them, and release the heat
F,
They warm up by
structures of the city have a high heat storage capacity.
day as the sun
marked
and vehicles.
at night.
warmer than the country. Figure 7-17 shows,
mean temperature on 12 nights at Winnipeg, Manitoba, a city of
650,000 population. The temperatures are shown as deviations from those measured at
the airport on the edge of the built-up area. Over the central business district, temperatures are on the average 2 to 3 K above those in the open country. The lines of equal
temperature differences clearly follow the outline of the city. The warm city area is
The
result
is
that the city is usually
as an example, the
called an urban heat island.
in a city center at night
All large cities have them.
may be
over 10
K warmer
In
extreme cases, temperatures
Down-
than the surrounding country.
wind from a city, advection by wind (A in Figure 7-16) carries heat and pollutants
away, and distributes them on to other settlements, crops and forests.
Heat islands form most readily
in
calm weather.
them, and with the heat the pollutants, too.
weather as that of the surrounding country.
A
Strong winds tend to disperse
windy day gives
the city
much
Interference by high buildings
Figure 7-17
Urban heal island
Winnipeg. Manitoba.
Thomas
the same
makes the
Source:
at
Hare and
(1979).
The urban heat
Winnipeg based on mean
at
deviation from airport temperature during 12
experimental runs
1
2
Kilometers
business
district.
(
C).
"CBD" means
central
250
Atmospheric Sciences
wind even
fect.
The
With
over the inner city
air
ter or ice droplets to
As
cities
bigger the
bigger
use in a city
if
Mean
These
may compare
used per unit area
are for
its
For city dwellers,
annual temperature
Tokyo, Japan, rose by 1.4
in
one remembers
effects are not surprising if
in selected cities.
Note
is
that the figures
a
borough of
Observe
that in
heating exceeds the natural annual net radiation
shown
New
are not in
York
City,
In
sum
the
K
be-
energy
all
of
all
cases lor
and the data for
Manhattan and Moscow the
(i.e.,
outputs of power by radiation of various kinds).
that
K
cli1
Table 7-3 shows the power
with natural radiative heating.
inner area only.
The
has been a real
this
example, mean annual temperature rose almost
For example. Manhattan
cities.
fog forms, the pollutants combine with the wa-
the heat island.
is
In Paris, France, for
tween 1915 and 1970.
Sydney
trapped by the obstacles and remains in the urban
form smog.
between 1880 and 1965.
whole
is
have grown bigger, their heat islands have become more intense.
city, the
matic change.
in the city
winds, however, the buildings have the opposite ef-
iight
Pollutants accumulate, and
canyons.
wind gusts
All of us have observed the violent
gustier in the city.
center near skyscrapers.
Chapter 7
artificial
natural inputs and
Manhattan, the
artificial
power
is
actually about eight times the natural source.
From
experience,
we
find that each city
is
different
and Milan, are
geles, Vancouver, Fairbanks,
the urban
from
Many
ences of topography, for example, have marked effects.
neighbors.
its
Differ-
such as Los An-
cities,
built in valleys or basins that tend to trap
boundary layer within walls of high ground. These areas have much more
vere air pollution problems than do cities in open sites, such as Chicago, Illinois.
quite shallow basins can produce
examples of
marked
effects
on calm nights.
London and
se-
Even
Paris are
this.
TABLE
POWER USE PER UNIT AREA. SELECTED
7-3
CITIES
Power use per
City
Population
Area
unit area
(millions)
(km 2 )
(W/m 2)
630
1.7
234
Moscow
6.4
878
Sydney, Australia
0.1
24
West Berlin
2.3
233
21
Los Angeles
7.0
3.500
21
Manhattan, N.
Source:
Landsberg
Y.
(
127
"
57
19X1).
PROBLEMS
7.1.
Why
is
the height of the troposphere in tropical areas different than
it
is
in
northern re-
gions'.'
7.2.
Explain
how and why
stratosphere.
the temperature changes with height in (a) the troposphere; (b) the
Chapter 7
Warm
7.3.
7.4.
251
Problems
air may.
be as dense as cold
Ki as dense as
air at
Solar radiation
at
short grass
o
('
noon on
and has
particular daj
a
measured
is
Using the hydrostatic equation
a
measured
is
15
C
to be
(288 K).
make
to
30°C (303
air at
W/m2
MOO
The surface is
The downward longwave ra-
upward longwave
879i ol the
at
needed
is
1000 mbar?
is
.
radiation from the
Calculate the probable value of the net radiation.
surface
at
pressure
measured temperature of
a
diation from the atmosphere
7.5.
What
air.
(273 K). whose pressure
pressure of 700
m
layer 10
thick,
mbar
decrease of pressure with height
(7.5), calculate the rate ol
the temperature
if
C
3
is
(270 K).
(Hint.
Assume
that d:
is
a
i
7.6.
The pressure gradient on a particular occasion is 10 mbar per 1000 km. Calculate a probable value lor the wind speed at 600 m above the ground. [Assume that the air temperature
7.7.
Air with a relative humidity of 509?
is
7.8.
-
C
7
(280 Ki and the
What
to 25 ('
(298 K).
What
meant by
is
air
will be
Using
library
distribution.'
7.10.
its
1000 mbar: latitude
is
at
C
12
(285 Ki
specific humidity
at
is
30
.]
heated without change of pressure
is
the
new temperature?
What examples can you
the periodic variation of a climatic element'.'
own
of such variation.' Use your
7.9.
pressure
experience as well as the
sources, locate the world's main desert regions.
Can you suggest
give
text.
What can you
sa\ about their
reason tor their dryness?
a
Near the North Pole, winter temperatures
quickly to
tail
-35 C (238 K) and then remain
Can you suggest
near that level, even (hough several months of complete darkness remain.
why
7.11.
the temperature does not continue to fall?
Prepare a rough checklist of design problems
weather data are
7.12.
Suppose
years.
LIST
that there
What
effect
a long
is
series of
might such
OF SYMBOLS AND UNITS USED
IN
a series
in
the field of civil engineering
Where would you
to be important.
likelj
major volcanic eruptions over
have on world
CHAPTER
which
a
period ol several
climate'.'
7
English
Numerical
Meaning
symbols
a
in
get these.'
albedo (fractional
Units
reflectivity)
specific heat ol air at constant pres-
values
dimensionless
K
kJ/kg
1.0
sure
e
£
saturation vapor pressure of water
N/m
\7m
evaporation or evapotranspiration
kg/m 2 (mm
vapor pressure of water
:
(pascal)
(pascal)
depth of waien/h
per unit time
F
release oi heat by city
G
soil heat (lux
//
turbulent (convective) heal flu*
I
fuel
burning
W/m
W/m
W/m2
W/m
2
2
solar radiation flux
2
L
latent heat ol
vaporization of water
J/kg
2.44 x
M
latent heal ol
melting ice
J/kg
5.33
«
distance (horizontal)
m
N
runoff of water pel unit time
p
atmospheric pressure
kg/m (mm depth ol water)/h
mbar (mean sea level averages)
I0 6
x 10 5
:
1013.25
252
LIST
Atmospheric Sciences
OF SYMBOLS AND UNITS USED
IN
CHAPTER
Chapter 7
7 (continued)
English
Numerical
Meaning
symbols
Units
P
precipitation per unit time
kg/m 2 (mm of
q
specific humidity
g/kg (dimensionless)
Q
photosynthetic energy conversion
r
relative
W/m
humidity
values
precipitation )/h
2
percent of saturation (dimensionless)
RN
R
R i
net radiation flux
W/m
universal gas constant (dry air)
J/kg
long-wave radiation flux from
W/m
at-
2
K
287.0
2
mosphere
s
deJdT
S
snowfall per unit time
mbar/K
kg/m 2 (mm depth of snow)/h
T
V
temperature
K
wind
vg
v
geostrophic wind
m/s
m/s
m/s
X
humidity mixing ratio
g/kg (dimensionless)
z
height
m
velocity or speed
wind
surface
s
Greek
symbols
Note:
Numerical
Meaning
Units
a
Parameter
Y
Psychrometric constant
mbar/K
e
Emissivity of surface
dimensionless
M
Micro
—
4>
Latitude
deg or rad
P
Air density
kg/m 2
a
Stefan-Boltzmann constant
W/m
CO
Rate of rotation of earth
rad/s
The
S.I.
system
is
in
Equation 7.12
values
dimensionless
0.64
1/1000
2
K4
5.67 x 10" 8
7.3
used where possible. For lengths (including wavelength), measures are
in
micrometers (pm) or nanometers (nm). Precipitation, runoff, and evaporation are usually measured
accumulated (mm). Snowfall
preferred.
Snow
melt has a
is
usually measured in
mean
mm
density of 0.1; hence,
of snow melt:
1
cm
of snow
if
is
measured
meters (m),
in
terms of depth
fresh, the centimeter
roughly equal to
1
mm
x 10" 5
(cm)
is
of snow-melt water.
REFERENCES
Atmospheric Environment Service. Modelling
gest Report
CCD
the Global Climate System, Climate
Change Di-
94-01, Toronto: Environment Canada, 1994.
Barry, R. G. and Chorley, R.
S.
Atmospheric, Weather and Climate. London: Methuen, 1982.
F. W. Trends '93: A Compendium of Data
on Global Change. Oak Ridge, Tennessee: Carbon Dioxide Information and Analysis
Boden,
T. A.,
Kaiser, D.
Center, 1994.
P.,
Sepanski, R. V. and Stoss,
Chapter 7
253
References
Bi'DYKO. M. The Heat Balance of the Earth's Surface, translated by N.S. Stepanova, Washington,
D.C.: U.S. Department of Commerce, 1958.
Hare.
K..
F.
and Thomas, M. K. Climate Canada. 2nd ed. Toronto: Wiley, 1979.
Hengeveld. H. Understanding Atmospheric Change.
SOE
Report 91-2. Toronto: Environment
Canada. 1991.
Houghton.
J.
T, Jenkins, G.
J.,
and Ephraums,
J. J.
(eds.).
Climate Change: The
IPCC
Scientific
Assessment. Cambridge: Cambridge University Press, 1990.
IPCC Intergovernmental Panel on Climate Change. Climate Change: The IPCC Response
Strategies.
Geneva and Nairobi: World Meteorological Organization and United Nations
Environment Programme. 1990.
La.ndsberg. H. The Urban Climate.
Lins, H.
Hare,
F.,
F. K.
New
and Singh. K.
G. and RlGGS, H. C.
(eds.).
P.
York: Academic Press, 1981.
Influence of the atmosphere. Chapter 2 of
Wolman, M.
Surface Water Hydrology. Boulder, Colorado: The Geological
Society of America. 1990.
List, R.
Smithsonian Meteorological Tables, 6th revised edition. Washington, D.C.: The Smith-
J.
sonian Institution. 1951.
Mather,
R. Climatology:
J.
Fundamentals and Applications.
M. (ed.). Confronting Climate Change:
bridge: Cambridge University Press, 1992.
Mintzer,
Oke.
I.
T. R.
Schneider.
Risks,
New
York: McGraw-Hill, 1974.
Implications
and Responses. Cam-
Boundary Layer Climates. London: Methuen, 1978.
S. H.
Global Warming.
New
York: Vintage Books, 1989.
Sellers. W. D. Physical Climatology. Chicago: Chicago University Press, 1965.
CHAPTER
8
Microbiology and Epidemiology
Gary W. Heinke
8.1
INTRODUCTION
Although the word health does not appear
the protection of
human
in the title, this
chapter deals with health
health from environmental influences.
Epidemiology, the
sci-
ence concerned with the study of epidemics, was the basis for environmental sanitation
and preventive medicine for the past century and a half and
sion here.
Because
is
worthy of a brief discus-
of the great importance of microorganisms in environmentally trans-
mitted diseases of humans, and because of their importance in ecology and in the
technology of environmental control, microbiology (the study of microorganisms and
their activities) is also introduced in this chapter.
Microbiology (Greek micros, small,
of microorganisms and their activities.
cerns itself with microorganisms
cases soil that
may
bios,
commonly found
affect public health,
life,
and logos, study
of)
is
the study
Environmental or sanitary microbiology conin water, wastewater, air,
decompose organic
and
in
some
matter, or perform a useful
function.
Epidemiology (Greek epi, upon; demos, people, and logos, study of) means "the
come upon the people"; taken in the context of disease, it means the
study of the causes of disease among a population. Epidemic describes the widespread
outbreak of an infectious disease in a community. Endemic refers to diseases that arc
study of what has
254
255
Fundamentals of Microbiology
Sec. 8.2
Since the objective of epidemiological
continuously present in a particular population.
Studies
is
to control the
spread of disease, the determination of the etiologic agent (that
which causes the disease) and the mode of transmission of the disease are of prime importance for successful control.
Only recently have we realized
that
plicated,
many
noninfectious diseases are caused by the
Both inorganic and organic contaminants are im-
toxic substances in industrial wastes.
and long-term epidemiological studies are needed
to
determine the "safe" con-
centrations and exposure times that can be tolerated without adverse environmental
effects.
Endemic
refers
a disease prevalent
to
in,
and confined
to,
a particular
population.
An epidemic
an outbreak
is
of
an infectious disease spreading widely
in
an
area.
Epidemiology
Microbiology
8.2
is
the study of the causes of a disease
in
a community.
the study of microorganisms and their activities.
is
FUNDAMENTALS OF MICROBIOLOGY
8.2.1 Classification of Microorganisms
Most
living things
imal kingdom.
were originally
classified as belonging to either the plant or the an-
However, many microorganisms did not
two categories, and Haeckel proposed
these
The
nized, the protista.
were unknown
in
1866
fit
unequivocally into either of
that a third
With advances
1866).
into
knowledge of
in
two categories:
cell
kingdom be recog-
and bacteria (viruses
protista included protozoa, algae, fungi,
were further subdivided
otista
in
ultrastructure, the Pr-
the higher protista (the eukaryotes).
consisting of either unicellular or multicellular organisms that have a true nucleus, and
the lower protista (the prokaryotes), consisting of organisms that have
no true nuwhich include only bacteria and blue-green algae, the ge-
In the prokaryotes,
cleus.
netic material of the cell
chromosomes and
is
blue-green algae are
ria; thus,
—
the
DNA — is
not organized into structures recognizable as
not separated from the cytoplasm by a nuclear
now
prokaryotes and bacteria are synonymous terms.
are grouped as eukaryotic protists.
ther of the foregoing groupings.
grouped as the eukaryotic
membrane.
The
generally referred to as blue-green bacteria or cyanobacte-
Viruses,
Based on
protists. the
Protozoa, algae, and fungi
which are noncellular,
this classification,
are included in nei-
microorganisms can be
prokaryotes and the viruses (Gaudy and Gaudy.
1980).
Bacteria are the most important group of microorganisms.
the nutrient cycle of the ecosystem.
the
They
are essential to
Pathogenic (disease-causing) bacteria have received
most attention and are discussed further
in
Section 8.4.
Many
other bacteria are im-
256
Microbiology and Epidemiology
Chapter 8
portant in water and wastewater treatment processes, in the natural self-purification of
streams and lakes, and in the decomposition of materials in
Viruses, which are smaller than bacteria,
heaps.
animals as well as
in
may
landfills, soils,
and compost
also cause diseases in plants and
humans.
Algae are a group of photosynthetic plantlike microorganisms. They can cause
problems in water supplies by imparting tastes and odors and by clogging filters. They
are beneficial in oxidation ponds, providing oxygen for low-cost wastewater treatment.
On
amounts of nutrients
the other hand, excessive
water can lead to algal blooms,
in
which when they decompose, remove dissolved oxygen from
trient
enrichment called eutrophication
Fungi
is
lakes.
discussed in Chapter
The process of nu-
9.
are unicellular or multicellular nonphotosynthetic protists that are able to
survive under
low-pH
industrial wastes
Protozoa
and
conditions.
They
are generally an order of
in the biological treatment
magnitude larger than bacteria and are useful
processes discussed in Chapter
12.
Rotifers are multicellular microorganisms which are sometimes present
fluent of biological waste treatment plants.
consuming organic
colloids, bacteria,
They perform
are microscopic in size
and algae.
and serve as food for
of normal, unpolluted conditions
in the ef-
a "polishing" function by
Crustaceans are multicellular organisms with a hard body or
them
some
are useful in the biological treatment of
composting of solid organic wastes.
in the
fish.
in receiving waters.
They
shell.
Some
of
are considered indicators
Figures 8-1 and 8-2 show some
of the aforementioned microorganisms.
According
microbial nomenclature, microorganisms are given two names, to
to
indicate their genus (plural: genera) and species.
For example, Escherichia coli
is
combination of two names: Escherichia indicates the genus and coli the species.
generic
name begins with
a capital letter and the species
name with
a lowercase
the
The
letter.
8.2.2 Bacteria
They
Bacteria (singular: bacterium) are unicellular microscopic organisms.
in water,
mans
wastewater,
soil, air,
(skin, intestinal tract).
and milk, on plants
are found
animals, and hu-
(fruits, vegetation),
Bacteria reproduce by binary fission and are characterized
by their shape, size, structure, and arrangement of cells.
Individual bacteria have one of
three general shapes: spherical (cocci, singular: coccus), cylindrical or rodlike [bacilli,
singular: bacillus),
be arranged
in
and spiral-shaped
groups such as
amples of important bacteria
(spirilla, singular: spirillum).
pairs, clusters, or chains (Figure
in the
environmental
field are listed in
p.m
c).
Table 8-1.
bacteria range in size from 0.5 to 5.0 |itn long and 0.3 to 1.5 urn wide.
0.1
may
Some ex-
Bacterial cells
8— lb and
Most
Cocci are about
in diameter.
Figure 8-3
rigid cell wall,
is
a schematic diagram of a typical bacterial
which maintains the shape of the
motic pressure.
If the cell
from the pressure of
counts for 10 to
40%
its
cell
cell.
All bacteria have a
and protects the contents from os-
wall were removed, the cell would quickly collapse or burst
contents.
The wall
is
usually 0.02 to 0.03 jim thick and ac-
of the dry weight of the organism.
Sec. 8.2
257
Fundamentals of Microbiology
Hexagonal
Head
Nucleic Acid
Core
r
Contractile
Tail
<
Base
Bacteria Streptococcus
(b)
Sheath
pneumoniae. One of the causative
agents of ppeumonia showing the typical
arrangement of pairs of spherical bacteria
plate
Size ranges from 0.5 to 1 .25 urn in
diameter. Source: M.J. Pelczar and
E. C. S. Chan, Elements of Microbiology
(New York: McGraw-Hill, 1981).
cells.
Tail
(a)
Fiber
Virus (Bacteriophage) Source: Ward's
Natural Science Establishment,
Rochester, N. Y., 1964.
Inc.,
Anabaena
urnTfrmTTrrrrrpr9r, , r r
BBa
Anacystis
E wo«u«
(c) Bacteria Salmonella typhi. The
causative agent of typhoid are typical
rod-shaped bacteria (bacilli). Source:
M.J. Pelczar and E. C. S. Chan,
Elements of Microbiology
(New York: McGraw-Hill, 1981).
(e)
Fungi (Mycelium). Source: Buckman and Brady (1960).
Figure 8-1
Some
slime layer.
Algae. Two forms of algae suspected
be responsible for tastes and odors in
drinking water. Source: Palmer. (1959)
(d)
to
Virus, bacteria, algae, and fungi.
bacteria are covered by a layer of viscous substance called the capsule or
It
is
believed that capsular material
of the viscosity of the slime,
it
is
on some pathogenic bacteria increases
some other cases
blamed
excreted from the
some
cause disease.
more of
found mainly on
bacilli.
but because
Loss of the capsule
in
Capsules have also been
industrial processes.
bacteria are motile, or capable of rapid
ing of one or
cell,
The presence of capsules
their infective capacity.
results in loss of the ability to
for the production of slimes in
Many
is
not readily diffused away.
their whiplike flagella.
movement
in liquids
by rapid
lash-
These are long threadlike appendages
There may be one or more
flagella attached at
one end of the
258
Microbiology and Epidemiology
Chapter 8
A protozoan
Source: Ontario
Ministry of the Environment, Activated
Sludge Process Workshop Manual. 5th
ed. (2nd revision). (Toronto:) Ministry of
(b) Rotifer. A multicellular animal
that feeds on bacteria and organic
matter. Two rows of cilia surround
Government Services,
food into the oral cavity.
Clark etal. (1977).
(a)
Protozoan
covered with
Vorticella.
hairlike cilia.
head of the organism and
appear to be rotating as they sweep
the
Publication Centre,
August 1978.
Daphnia
Source:
Cyclops
(c) Crustaceans. Very small microscopic multicellular organisms with
hard shells. They feed on other microorganisms and organic matter and
are in turn food for small fish. Source: Clark et al. (1977).
Figure 8-2
cell,
or there
may be many
rotifer,
and crustaceans
distributed along the length of the bacillus.
flagella are usually nonmotile.
between various
Protozoan,
The existence and form of
Bacteria without
flagella help to differentiate
bacterial groups.
Immediately beneath the cell wall is the semipermeable cytoplasmic membrane
(about 7.5 x 10~ 3 jam thick).
It serves the very important function of providing a
semipermeable boundary separating the protoplasm from the external environment while
allowing the passage of nutrients into the
cell
and waste products
membrane by chemical or physical agents can cause
The protoplasm, or the internal contents of the
out.
cell,
in
appearance, due
in part to the
to this
can be divided into three
ferent areas: the cytoplasm, the nuclear area, and the polyribosomes.
granular
Damage
the death of the cell.
abundance of RNA.
The
dif-
The cytoplasm
fluid portion
is
of the
TABLE
SOME BACTERIA OF SIGNIFICANCE
8-1
Group of
259
Fundamentals of Microbiology
Sec. 8.2
IN
THE ENVIRONMENT
Genus
bacteria
Pathogenic bacteria
En\ ironmental significance
Salmonella
Cause typhoid fever
Shigella
Cause dysentery
\/i
i
Indicator bacteria
obat terium
I
(
!ause tuberculosis
u hid
Enterobacter
Fecal pollution
Streptococcus
Clostridium
Decaj bacteria
Pseudomonas
Degrade organics
Flavobacterium
Degrade proteins
Zooglea
Roc-forming organism
(
activated sludge plants
in
'lostridium
Produce lain acids from organics
Microcot
i
in
anaerobic digester
us
Methanobacterium
Produce methane gas from
Methanococcus
anaerobic digester
fatty acids in
Vfethanosarcina
Vitrobacter
Nitrifying bacteria
Oxidize inorganic nitrogenous compounds
Vitrosomonas
Bacillus
Denitrifying bacteria
Psi
Reduce
Azotobacter
Nitrogen-fixing bacteria
nitrate
and
nitrite to
nitrogen gas or nitrous oxide
udomonas
Capable
oi
tixing
atmospheric nitrogen to
NH^
Beijerinckia
Oxidize sulfur and iron
Sul Hr bacteria
Thiobai
Sulfate-reducing bacteria
Desulfo\ ibrio
Photosynthetic bacteria
Chlorobium
t
<///n
Involved
Reduce
in
corrosion of iron pipes
sulfides to elemental sulfur
Chromatium
Iron bacteria
Filamentous
Sphaerotilus
Responsible for sludge bulking
Imn oxidizing
Leptothrix
Oxidize ferrous iron
cytoplasm contains dissolved nutrients.
matin, which
RNA
is
in
activated sludge plants
The nuclear area contains
the
(ribonucleic acid)
is
a long-chained, single-helix
ble for the biosynthesis of protein, helping to arrange the order of the
the specific proteins required by the cell.
In
tonus densel) packed particles called polyribosomes.
complex organic
DNA
curs
in
(deoxyribonucleic acid),
the nuclear area of
mine.
clear
Although the
membrane,
It
is
indispensa-
amino acids
conjunction with protein.
that
RNA
These produce the enzymes,
i.e.,
catalysts generally specific to each biochemical reaction.
all
cells.
a
It
very long-chained, double-helix
it
is
DNA
molecule, oc-
contains phosphoric acid, 2-deoxy-D-ribose (a
sugar), the purine bases adenine and guanine,
tin
or chro-
molecule containing phos-
phoric acid. D-ribose (a sugar), adenine, guanine, cytosine, and uracil.
make up
DNA
diffused throughout the cell in prokaryotes.
of a bacterial cell
and the pyrimidine bases cytosine and
is
diffused anil not contained in a nu-
conlined to certain areas within the
cell,
and these can be consid-
260
Microbiology and Epidemiology
Chapter 8
Cytoplasm
Containing
RNA
Capsule
Cell Wall
Cytoplasmic Membrane
Nuclear Area
Containing DNA
Many Polyribosomes
Figure 8-3
Schematic diagram of a typical bacterial
DNA
ered a primitive form of nucleus.
is
cell.
responsible for the genetic stability of the
species.
Some
bacteria (e.g., Bacillus and Clostridium)
dormant or resting phase of the
plants.
A
spores
may
normal, active cell
is
and
cell
called a vegetative cell.
many
may form
generations.
exist as vegetative cells for
adverse growth conditions, spores
These features are useful
analogous to the seeds of
Bacteria capable of forming
When
the cell
within the cytoplasm.
smaller or larger than the vegetative cell and
the center.
form spores, which represent a
in this respect are
may occur
in characterizing
at the
exposed
is
to
The spore can be
end of the
cell or
near
spore-forming bacteria.
Spores are extremely resistant to adverse chemical or physical environments.
Sporeforming bacteria are
(1)
common
in the air, soil,
and water. Their resistance
is
due
to
an impermeable spore wall made up of a dipicolinic acid-calcium complex and (2)
Under conditions conducive
the dehydration of the cell contents.
germinates and a
new
vegetative cell emerges.
ing bacteria difficult to destroy, but
is
for growth, the spore
This survival ability makes spore-form-
of obvious benefit to the bacterium.
8.2.3 Growth and Death of Bacteria
All living organisms have nutritional and physical requirements that must be
der to sustain their
in nutritional
teria
grow
at
life.
Among
the
many
met
in or-
species of bacteria, there are wide variations
requirements and the physical conditions they can withstand.
temperatures below 0°C, others
at
Certain bac-
temperatures as high as 99°C.
bacteria require atmospheric oxygen, whereas others are hindered by
its
presence.
Some
261
Fundamentals of Microbiology
Sec. 8.2
Bacteria are divided into two broad groups with respect to their energy and carbon
sources: heterotrophic and autotrophic.
ergy and carbon from an organic
Heterotrophic bacteria obtain both their en-
compound
Autotrophic bacteria re-
or organic matter.
quire carbon dioxide as their carbon source and obtain their energy from sunlight or by
the oxidation
inorganic compounds.
o\'
autotrophs require sunlight as their energy
If
source, they are called photoautotrophs.
If
they obtain their energy by oxidizing inor-
ganic chemical compounds, they are called chemoautotrophs.
addition to carbon, nutrient requirements include nitrogen, sulfur, phosphorus,
In
and traces of metallic elements such as magnesium, calcium, and
widely
in the
way
they obtain these nutrients.
Some
iron.
Bacteria vary
bacteria can "fix" or obtain nitro-
ammo-
gen from the atmosphere: others obtain nitrogen from inorganic sources such as
nia or nitrates.
A number
of bacteria are very specific in their nutrient requirements, whereas oth-
ers are able to utilize a variety of sources for their needs.
can manufacture their
bacilli will not
own
For example, Escherichia coli
vitamin requirements from other compounds, but the lacto-
grow unless
specific nutrients are
immediately available.
The
latter or-
ganisms are called fastidious heterotrophs.
Many
ture range within
at
which
to
C
and pH.
their
temperatures as low as
optimal temperature of 15
20
growth occurs.
C
Psychrotrophs
are bacteria that can
grow
C and up to 25 to 30 C. Those psychrotrophs that have an
C or lower and a maximal temperature for growth at about
are called psychrophiles.
optima of 40
factors are temperature,
Bacteria can be grouped according to the tempera-
Mesophiles grow best within the temperature range 30
40 C. while thermophiles can grow
ture
The major physical
factors affect bacterial growth.
the gaseous environment,
at
temperatures up to 99
C
and have tempera-
or higher.
The most important gases involved
directly in bacterial
growth are oxygen for
obic biological oxidation and carbon dioxide as a source of carbon for autotrophs.
cause of the importance of oxygen,
it
is
often
following groups on the basis of their need for free
useful
(i.e.,
divide
to
bacteria
into
aer-
Bethe
molecular) oxygen:
•
Aerobic bacteria require free oxygen for growth.
•
Anaerobic bacteria can grow without free oxygen.
•
Facultative bacteria can
•
Microaerophilic bacteria grow in the presence of minute quantities of molecular
grow with or without oxygen.
oxygen.
The
adjectives facultative and obligate describe the degree of
ular condition.
all
in the
uses
C0
pounds
2
For example, an obligate anaerobe
presence of free oxygen.
A
is
facultative autotroph
as a source of carbon, but can also
dependence on a
a bacterium that will not
is
partic-
grow
at
an organism that normally
grow heterotrophically with organic com-
as energy sources.
The third major factor influencing bacterial growth is pH. Most
optimum growth at a pH range from 6.5 to 7.5, with maximum limits
bacteria exhibit
for
growth be-
262
Microbiology and Epidemiology
pH
tween
The metabolic
4.0 and 10.0.
activities
Chapter 8
of bacteria can cause shifts
pH
in the
Therefore, the environment must have a buffering capacity to
of their environment.
neutralize these shifts
if
growth
is
to continue for an
physical conditions are important for
some
extended period of time.
Other
For example, pho-
species of bacteria.
totrophic bacteria require light as their source of energy and a few bacteria require un-
Dead Sea
usually high salt concentrations, like those found in locations such as the
Utah's Great Salt Lake.
must be dissolved
in
All bacteria require moisture for growth, since
cell;
new
the cell occur as nutrients are taken into the cell and
Nuclear material
cell material.
is
reproduced and distributed
a cell wall or septum develops that divides the bacterium and separates
The reproductive process of
viable cells.
bacterial
or
nutrients
order to penetrate the cell membrane.
Growth and reproduction of
processed into
all
bacteria,
binary
it
in the
two
into
fission, is a characteristic of
growth (Figure 8-4).
Parent Cell
Cell Elongation
C
—J^-—
Invagination of Cell Wall and
Distribution of Nuclear Material
\
Formation
C53G3
of
Transverse Cell
Wall and Organized Distribution
of Cellular Material into
Separation into
Two
Two New
Cells
Cells
Figure 8-4
Each
Cell
Repeats Process
cells.
Binary fission of bacteria
Pelczar et
Source:
Bacterial populations can reach high densities very quickly.
double
at a rate characteristic for
time interval
to
20 min
is
for
known
mum
as the generation time.
Escherichia coli
somonas europae).
each organism under a given
to several
Generation times
set
at
The
in a
(1977).
individual cells
of conditions.
(
1
1
15
h for Nitro-
wide variety of conditions,
growth requires a specific environment for each species.
This
20°C range from
hours for other species
Although bacteria can grow
al.
opti-
263
Fundamentals of Microbiology
Sec. 8.2
The
of growth of a bacterial population
rate
directly proportional to the
is
number
This can be expressed mathematically as
of bacteria present.
^ = kB
(8.1)
dt
=
B =
A =
where dBldt
growth
rate of
concentration of bacteria
first-order
growth
time
at
t
rate constant
Integrating equation (8.1) yields
nf-=fr
where B
B =
{)
2B
,
the initial population concentration.
is
If
as a function of time
/
the generation (doubling) time,
(8.3)
we can
Taking the logarithm of
this equation,
logfl
plot of
B
0.3/6' (log2
against
=
=B
we
2" (i
obtain
= logfl + i
B
(8.5)
is in
until stabilization at a
line
with a slope of
.
reality typical of
maximum
only a small portion of the
batch culture, as shown in Figure
in a
period of what appears to be
initial
'og2
on semilog paper would produce a straight
/
0.3) and a y intercept of
This type of logarithmic growth
After an
(8.4)
{)
normal growth pattern of a bacterial population
growth occurs
express the bacterial population
as
B
8-5.
is
^
=
Substituting this value of k into Equation (8.2),
A
G
and equation (8.2) can be rewritten as
k
B
(8.2)
little
or no growth, rapid exponential
population
is
reached followed by a de-
clining or death phase.
During the
lize the
cells.
start
deficient in certain
surrounding nutrients.
The
toplasm
period, called the lag phase, the cells adjust to their
initial
They may be
ronment.
is
These enzymes, therefore, have
individual cells also increase
developed.
When
enzymes or coenzymes required
this
in size
beyond
adjustment period
is
their
regular intervals.
It
bacterial population
is
is
growth phase,
in
metabo-
normal limits as new pro-
is
cell
can divide and
a gradual transition into
which the population doubles
most uniform during
this
period
in
at
The
terms of chemical compo-
the period of most rapid growth under optimal conditions.
the
envi-
be synthesized by the
complete, the
reproducing normally. At the end of the lag phase, there
the log (logarithmic) or exponential
to
new
to
264
Microbiology and Epidemiology
6
r
5
Stationary Phase
(May Be Very Long)
4
£
Chapter 8
CO
I
3
I
2
Exponential Phase
Lag Phase
o
-
1
Death Phase
I
,
I
i
i
4
2
1,1,1
i
6
10
8
12
Time
Figure 8-5
metabolic
sition,
rates,
16
14
(h)
Typical bacterial growth curve.
Source:
Mitchell
and other physiological characteristics.
(
1974).
This phase of rapid
growth obviously cannot continue indefinitely because of food limitation, and the
start
to die off.
This results
in
cells
a decrease in the growth rate until zero growth
is
achieved.
When
a
the
number of new
dynamic equilibrium
is
cells
reached
at
being produced equals the number of cells dying,
which there
is
no further increase.
This
is
called
The reason for cessation of the growth phase is usually due to
exhaustion of one or more nutrients.
The death or declining phase is reached when the death rate starts to exceed the
the stationary phase.
the
growth
In addition to the depletion of nutrients, toxic by-products of cell
rate.
metabo-
lism can build up in the environment, inhibiting further growth.
In
continuous biological waste treatment processes (Chapter
population degrading the waste organic matter
is
predominantly
12),
the bacterial
in the stationary to de-
clining phase.
Just as conditions can be created for the
optimum growth of
rable conditions can be used to eliminate bacteria.
life
is
struction of pathogens (disease-causing organisms).
amount of material
destroyed.
is
to heat
it
quire a higher temperature for destruction.
steam
at
The simplest means of
which the cell
to a temperature at
Living organisms are destroyed
lization with
Complete destruction of microbial
Disinfection, on the other hand, implies the selective de-
called sterilization.
a small
bacteria, so unfavo-
at
100 C.
sterilizing
protein
However, bacterial spores
At a temperature of 121 C, complete
about 105 kPa (15 psig)
is
is
re-
steri-
generally achieved in less than 20
min.
Microorganisms can also be destroyed by shortwave radiation (200
by high-frequency sound.
Shortwave
ultraviolet irradiation can
be used
to
400 nm)
or
to sterilize sur-
.
The
faces or large enclosed areas.
sonic waves
(sonification
cell
not
is
)
radiation destroys the cells' nucleic acids.
Ultra-
frequencies in the range of 200,000 hertz (cycles per second) can
at
rupture
effectively
method
265
Fundamentals of Microbiology
Sec. 8.2
walls
of
employed
Usually,
bacteria.
however,
energy
ultrasonic
to control microbial populations, but
it
useful as a
is
for disrupting cells to extract their intracellular constituents.
Disinfection
is
most often achieved by the use of chemical bactericidal agents.
Oxidizing chemicals such as chlorine, chlorine compounds, iodine, and ozone are very
effective for killing
extent,
microorganisms
destroy the cell or parts of
They
agent.
water and wastewater.
in
ozone are the most widely used disinfection agents.
it
so that
cannot reproduce even after the removal of the
it
by oxidizing the enzymes and other material
act
nonspecific action of chlorine and ozone
will develop.
cell
Chlorine and, to a lesser
These agents permanently
The
rate of disinfection
is
makes
cytoplasm.
The
dependent on the nature of the disinfectant, the
Some
physiology, and the environment.
in the
unlikely that resistant bacterial strains
it
important variables are the concentration
of the disinfectant, the contact time between the microorganisms and the disinfectant,
the temperature, and the pH.
cussed
in
Chapter
1
The application of
disinfection in water treatment
is
dis-
1
8.2.4 Viruses, Algae, Fungi, and Protozoa
Other microorganisms of importance
viruses, algae, fungi,
Viruses.
The smallest of
10~ 3 |im). By comparison, the
or
not
1
in
environmental science and engineering include
and protozoa.
the viruses range
from
size of a small bacterium,
10 to 250
nm
Salmonella typhi,
nm =
(1
1000 nm,
is
Viruses are unique in that they contain no internal enzymes and therefore can-
|im.
grow or metabolize on
their
own.
They
are obligate parasites, infecting the tissues
of bacteria, plants, and animals, including humans.
Some examples
of
human
patho-
genic viruses are those that cause smallpox, infectious hepatitis, influenza, and poliomyelitis.
Figure 8-6
composed of
is
The capsid
called a capsid.
plete virus unit
symmetry.
each other.
is
mumps and
is
DNA
made up of
called a virion.
influenza viruses.
or
RNA,
In general, viruses are
surrounded by a protein covering
smaller units called capsomeres.
A com-
Viruses are formed according to geometric rules of
The types of protein making up the capsid help to distinguish viruses from
Each type of virus can infect only a specific type of host cell so that, for
example, an animal
According
have the
a sketch of
a nucleic acid core, either
viral
disease cannot be transmitted to humans.
to cell theory, viruses are not
ability to
living organisms.
They do, however,
reproduce or replicate themselves within their specific host
cause they are not really alive outside a host
cell,
cells.
Be-
they survive for a lone time between
infections and can only be "killed" by alteration of their molecular structures.
The
algae, fungi, and protozoa are
much more complex and have more
structures than those of the viruses or bacteria
specialized
266
Chapter 8
Microbiology and Epidemiology
a;
Figure 8-6
Sketch of
mumps and
nm in size).
influenza viruses (80 to 120
Source: Pelczar
et al. (1977).
(Suggested by a drawing by R. M.
Mumps
Influenza
Jr.,
November
Time,
Chapman
17, 1961.)
Except for the blue-green algae they have a discrete nucleus
Algae.
rounded by a nuclear membrane and are therefore
"having a true nucleus." They have thick cell walls.
classified as eukaryotic,
sur-
meaning
Algae therefore include members
Their size ranges from microscopic unicellular
of both the higher and lower protista.
phytoplanktons to the large multicellular seaweeds.
can be spherical, cylindrical, clublike, or
spiral.
The shapes of
unicellular algae
Multicellular colonies can
grow
in fil-
aments or long tubes or simple masses of single cells that cling together (Figure 8-7).
The filamentous or tubelike growths can be branched or bundled together and may
even contain
cells that
higher plants.
perform special functions.
all
pigments and are thus capable of photosynthesis.
thetic
distinct bodies called plastids, chloroplasts, or
primary producers
in the
runs, and cause high chlorine
blooms, forms
in
Table 8-2.
The pigments
ehromatophores.
are
found
in
Algae are important
demand.
and odors, clog water intakes, shorten
Excessive growth of algae,
known
filter
as algal
of organic material that interferes with the recreational use of
Algae are classified on the basis of
waters.
shown
a blanket
like the
algal cells contain photosyn-
aquatic food chain, although they can be a problem in water
supplies, since they contribute to tastes
field
These appear superficially
Regardless of the size or complexity,
Groups
I,
II,
because of their appearance
in
IV,
their pigments.
and VII are of
Seven general groups are
interest in the
both clean and polluted water.
environmental
The others
are
mostly marine algae.
Fungi.
Fungi are nonphotosynthetic higher protists (eukaryotes) and
may be
divided into three groups: molds, which are filamentous fungi; yeasts, which are nonfilamentous fungi; and mushrooms, which are macroscopic fungi. Fungi (Figure 8-8)
meaning that they feed on decaying organic
wide range of complex organic substances as food
sources and are much more tolerant of acidic conditions than are most other microorganisms. Except for yeasts their mode of reproduction is by either sexual and/or asexare typically aerobic and saprophytic,
matter.
They
are able to use a
ual spores.
Molds grow by extending long
mass called mycelium
strate to
threadlike structures called hyphae. which form a
(plural: mycelia).
The vegetative mycelium penetrates
the sub-
absorb dissolved nutrients, while the reproductive mycelium forms reproductive
structures (spore sacs, spores, etc.).
267
Fundamentals of Microbiology
Sec. 8.2
Figure 8-7
Some
types of algae found
in
polluted water.
Source:
Yeasts are unicellular, considerably larger than bacteria
(1
Palmer
to 5
(
1454).
|im
in
width and
5 to 30 |im in length), and generally egg-shaped, spherical, and ellipsoidal cells that are
widely distributed
in nature.
Sexual reproduction
tative; that
is,
is
they can
They reproduce asexually by binary
by the formation of ascospores.
fission or
by budding.
Unlike molds, yeasts are facul-
grow both aerobically and anaerobically. Yeasts are used in a
(for making wine, beer, and bread) and for syn-
wide variety of fermentative processes
thesis of certain vitamins, fats,
and proteins from simple sugars and ammonia nitrogen.
Others, like Candida, can cause serious
Mushrooms
human
infections.
are highly differentiated forms of fungi.
The mycelium
is in
the soil.
and under certain conditions the hasidia are formed above ground as the structures
call
mushrooms.
we
268
Microbiology and Epidemiology
TABLE
8-2
CLASSIFICATION OF ALGAE
Color
Division
I.
Chlorophyta
Grass
Scenedesmus), mostly colonial, filamentous.
Clean, cold water; mainly cellular, some colonial.
Yellow
Chrysophyta
have
green
III.
Yellow
Pyrrophyta
Environment/cell arrangement/comments
Fresh water; mainly clean-water algae (except Chlorella,
green
II.
Chapter 8
Diatoms
silica in cell walls.
Mostly marine;
90%
unicellular,
two
flagella.
brown
IV.
Fresh water; requires organic nitrogen; will grow as a proto-
Green
Euglenophyta
zoan
in
absence of
light; unicellular, motility
by
flagel-
lum.
V.
Rhodophyta
Red
Mostly marine; very clean, warmwater, colonial; sheets are
Phyophyta
Brown
Marine; cool-water; colonial, large.
common.
VI.
Example: Macrocystis,
giant kelp.
VII.
Blue-green a
Cyanophyta
Fresh water, warm, often polluted; unicellular, gelatinous
clumps; no chloroplasts or true nucleus; nitrogen
often responsible for algal blooms.
^Blue-green algae are
now
generally referred to as blue-green bacteria or cyanobacteria.
The hyphae form a mycelium on
the surface and extract
surfaces are attached by stolons.
The spores are in a sporangium at the tip of a specialized
hypha, called a sporangiophore.
nutrients from
it.
New
Spores
Sporangiophore
Sporangium
Erect
Hypha
Stolon
Rhizoid
Figure 8-8
Sketch of a fungus. Source:
Mitchell (1974).
fixers,
269
Fundamentals of Microbiology
Sec. 8.2
The three groups of fungi are differentiated on the basis of their structure and
method of reproduction in the simplified classification scheme shown in Table 8-3.
TABLE
8-3
AND AQUATIC FUNGI
CLASSIFICATION OF SOIL
Type
Characteristics/examples
Division
Molds (filamentous)
Phycomycetes
Sexual or asexual spores; Mucor, Rhizopus
Fungi imperfecti
No
Yeasts (nonfilamentous)
Ascomycetes
Sexual spores
Mushrooms (macroscopic)
Basidiomycetes
Sexual stage on basidia:
Sonne: Adapted from Mitchell
Protozoa.
Most
walls.
l
l
l
sexual stage; Penicillium, Aspergillus
Neurospora, Candida
in sacs;
common mushroom
;74).
Protozoa are the most highly specialized unicellular organisms.
are nonphotosynthetic, reproduce asexually by binary fission, and lack true cell
Most species
motion (see Table
on the means of loco-
are motile, and classification can be based
8—i).
Their si/e varies from a few to several hundred microns.
tozoa are widespread in nature and occur in most habitats where moisture
They survive adverse conditions by forming cysts with
saprophytic (obtain food
in
dissolved form).
found wherever bacteria are prevalent.
Some
They
thick walls.
is
Protozoa
Pro-
present.
may
be
on bacteria and can be
are predators
are parasites capable of causing disease in
animals and humans.
TABLE 8-4 CLASSIFICATION SCHEME FOR COMMON AQUATIC
AND SOIL PROTOZOA
I.
Pseudopods (Sarcodina)
Motile by pseudopods; Mowing amoeboid motion;
II.
Motile b)
III.
Amoeba, Entamoeba
Flagellates (Mastigophora)
llagella:
mans photosynthetic; Euglena, Volvox, Giardia
C'iliates (Ciliophora)
Free-swimming; motile by many
cilia thai
move
in
unison;
Paramecium
Attached; fixed bj stalk to a surface; Vorticella
IV
Parasitic protozoa
(Suctoria)
Free-swimming
ciliates earlj
in
life
cycle, tentacles in later adult stalked stage
(Sporozoa)
Usuall) nonmotile; rarely free living; parasitic;
Plasmodium
Sonne: Adapted from Mitchell (1974).
The
cell
membrane
of sarcodina chanties shape continually.
by extending their cytoplasm
in
search of food.
The organisms move
These extensions are called pseudopo-
270
Microbiology and Epidemiology
Chapter 8
Pseudopod
Nucleus
Contractile Vacuole
Food Vacuole
Figure 8-9
An amoeba, a member
of the
Sketch of Amoeba.
Mitchell (1974).
and are typical of the amoebae (Figure 8-9).
dia, or false feet,
Entamoeba
phytic.
Source:
subphylum Sarcodina
histolytica
is
a
common
Sarcodina are sapro-
pathogen causing amebic dysentery in
humans.
The mastigophora have
thetic
and algae.
Some mastigophora
sleeping sickness in humans.
cilia.
flagella,
and some species are photosynthetic.
Photosyn-
organisms (such as Euglena) exhibit some of the characteristics of both protozoa
Trypanosoma, a blood
are parasitic.
The ciliophora
are characterized
parasite, causes
by having
In addition to providing motility, cilia aid in the capture of food.
these are parasitic.
Paramecium
is
fine hairs or
Very few of
a typical ciliate (Figure 8-10).
Oral Groove
Macronucleus
Gullet
Cilia
Food vacuale
Micronucleus
Anus
Ectoplasm
Endoplasm
Figure 8-10
A member
motility.
Sketch of Paramecium. Source:
of the
subphylum Ciliophora. The
cilia
Contractile
Cell
Vacuole
membrane
Mitchell (1974).
are used to capture food and
for cell
Sec. 8.3
271
Applied Microbiology
The
parasitic protozoa include suctoria
(free-swimming) and sporozoa (nonmo-
Four species of Plasmodium, the cause of malaria
tile).
in
humans, are members of the
The
male Anopheles mosquito.
latter
8.3
vector (carrier) that conveys these parasites to a
group.
human
host
is
the fe-
APPLIED MICROBIOLOGY
8.3.1 Soil and Solid Waste Microbiology
Most land-based
living
things
—
plants,
wastes eventually find their way into the
animals,
soil.
and
protista
—and
associated
their
There, microbial activity transforms this
Without
material into the substances that constitute soil.
this activity, nutrient cycles
such as the carbon cycle or the nitrogen cycle would not be complete, and
life
on earth
would be threatened.
make up
Soils
a very thin layer of material
Soil depth and
on the earth's surface.
the physical and chemical properties of soil vary with location, but in general there are
major components:
five
1.
These
Inorganic mineral particles.
particles, primarily
of aluminum,
silica,
and
amounts of other minerals, range in size from very small clay particles
(0.002 mm) to sand grains and pebbles. The proportions of such particles in the
lesser
soil
determine
and
nutrients.
the
2.
3.
most
its
common
Organic residues.
of the
soil
known
as
waterholding capacity,
humus.
in peat
Water.
Water
4.
Gases.
larly
ter.
5.
is
Plant and animal remains that
Organic
is
make up
component
the organic
fairly stable
substance
formed mostly of organic residue) are
necessary for microbial activity.
is
The amount of water
factors, including precipitation, soil structure,
contained
in the
pore spaces between particles
in
dry
soils.
in soil
de-
and microbial
in saturated
Various nutrients are dis-
water and are therefore available to microorganisms.
Gases, principally nitrogen and oxygen, but also carbon dioxide (particu-
where biological
activity
In saturated soils, small
Biological systems.
up the
soils (those
adsorbed on particle surfaces
in the
availability of air
bogs and marshes.
Water
population.
solved
and the
soils.
pends on a number of
and
structure,
through various stages of decomposition to a
found
soils
its
Inorganic soils (those consisting chiefly of mineral particles) are
fifth
occurring),
fill
the pore spaces not filled by
soil.
One gram of
wa-
will be dissolved in the water.
Plant root systems, small animals, and microorganisms
component of
billion bacteria,
is
amounts of gas
rich agricultural soil
may
make
contain 2.5
500,000 fungi, 50,000 algae, and 30,000 protozoa.
Aucomplex organic and inorganic substances.
Bacteria and fungi constitute the largest group of microorganisms in soils.
totrophic and heterotrophic bacteria degrade
272
Microbiology and Epidemiology
Chapter 8
some under aerobic conditions and others under anaerobic conditions. The fungi
compose cellulose and other major components of plant tissues, and, as might be
where aerobic conditions
pected, are generally found near the surface,
deex-
prevail.
In a fertile soil, the activities of algae are not as important as those of the bacteria
However, on very barren or inorganic
and fungi.
and rocks they are the primary
soils
Protozoa are also abundant wherever there are bacteria
producers of organic material.
and aerobic conditions.
The
extent and type of microbial growth in soil depend on the
same
factors that
control growth in aquatic environments:
•
Whether
•
The
•
Suitable temperature and
sufficient nutrients are present
availability of moisture and, for aerobic organisms, air
pH
Under favorable environmental conditions created by
or composting, soil
landfilling,
The most common means
Chapter 14). The waste mate-
organisms can be used to degrade municipal solid wastes.
of disposing of solid waste
is
organic matter,
is
rial, rich, in
day with a layer of organic
in sanitary landfills (see
placed
soil
in
trenches or
compacted, and covered each
pits,
which provides a large and
diversified population of
under aerobic and
microorganisms.
Microbial activity takes place
initially
obic conditions.
The
microorganisms break down the com-
facultative or anaerobic
later anaer-
plex organic substances into simpler organic acids which can be oxidized by the fungi
and aerobic bacteria into
lack of
oxygen once
C0 2
and
H 2 0.
In time the aerobic activity
is
limited by a
Carbon
ammonia, and other products from the decomposition
can cause environmental problems. These are discussed
the organic material
buried and saturated with water.
is
dioxide, organic acids, ethanol,
of organic matter
in
Chapter
When
in landfills
14.
the decomposition of municipal solid waste
aerobic environment, organic degradation
posting.
ful for
The
objective of composting
reclaiming land or improving
is
is
to
soil.
piles called
windrows
erates heat,
which destroys the pathogens
carried out in a controlled
is
accelerated and the process
Penicillium, and Aspergillus
Whether composting
is
)
about 3 days
in
70°C so
com-
done naturally
in
long
at
60°C.
However, the tem-
as not to kill the fungi {Mucor, Rhizopus,
and the thermophilic bacteria
(the
same genera
aerobic waste treatment processes) that produce the compost.
is
called
or mechanically in special equipment, the biological activity gen-
perature must be kept below about
composting
is
produce a nutrient-rich, stable product use-
as in other
Further information on
presented in Section 14.6.2.
Other applications
in
which biological
activity in the soil plays a role include
land-based wastewater treatment methods and sludge
These are considered
in
Sections 12.6.1 and
utilization
12.7.3, respectively.
on agricultural
land.
273
Applied Microbiology
Sec. 8.3
8.3.2 Water and Wastewater Microbiology
and Indicator Organisms
All water derives from precipitation in the
they
fall,
remove
particles of dust
precipitation, the dust, along with the
the air and the rainfall thereafter
snow,
few microorganisms
hail,
or sleet, which, as
after the first
it
contains,
few minutes of
is
relatively free of these contaminants.
is
washed out of
After reaching
into the
ground
to be-
or runs over the ground into streams, ponds, rivers, and lakes.
Because of the
and the lack of
rain,
However,
air.
up by vegetation either percolates
the ground, the water not taken
come groundwater
form of
from the
light,
filtering action
of the
soil,
low nutrient
levels,
groundwaters are normally free of organisms.
rocky areas, especially
in
low temperature,
However,
in
some
limestone formations, there can be fairly large underground
conduits, and surface water reaching the groundwater system through cracks or tunnels
can cause microbial contamination of the groundwater.
many
Surface water picks up
substances during
its
travel over agricultural lands
Agricultural lands contribute nitrates, phosphates, and
and through industrial areas.
other nutrients, plus microorganisms from the
soil.
Organic material such as leaves,
grass clippings, bird and animal droppings, and wastes from food-processing plants,
with their associated microbial population, also have access to surface water.
toxic contaminants are excessive, the result
is
all
Unless
that virtually all surface waters in the
world (with two possible exceptions*) support a thriving microbial population.
Many forms
of microbial
life
can exist
in
water provided that the appropriate
physical and nutritional requirements for growth are met.
sary for the growth of aerobic bacteria and protozoa.
an indication of water quality.
the
In clean water or water with a
number of microorganisms
nutrient
number of
content
species
is
is
increases,
neces-
low nutrient content, the
limited, but a great variety of species can exist.
the
number of microorganisms
bic or facultative bacteria will predominate.
increases
As
while the
few species of anaero-
In a polluted anaerobic stream, a
reduced.
is
The number and types of microorganisms present give
as light, are essential to algae.
total
Dissolved oxygen
Nitrogen and phosphorus, as well
Typical numbers of bacteria for various
waters are presented in Table 8-5.
In addition to the
that has
other
—
been described
in either a
in the
preceding sections, microorganisms can interact with each
cooperative or a competitive way.
environment, and
in the
independent behavior of the diverse types of microorganisms
we need
ological waste treatment systems.
enon and are described
1.
Algae-bacteria.
to be
Such
interaction occurs frequently
aware of these relationships
The following
three
examples
in the
design of bi-
illustrate the
phenom-
in
more
A
close association between algae (which need carbon dioxide
detail in
Chapter
12:
and produce oxygen) and aerobic bacteria (which need oxygen and produce car-
'
Lake Tahoe, straddling the California-Nevada border, and Lake Baikal
ents that they contain no microbial
life.
in
Russia are so lacking
in nutri-
274
Chapter 8
Microbiology and Epidemiology
TABLE
8-5
TYPICAL BACTERIAL COUNTS
Bacteria per 100
Source
IN
WATER
Coliform bacteria 3
per 100 mL
mL
0-1
Tap water
10
Clean, natural water
10 3
Polluted water
10 6 -10 8
10 3-10 5
Raw sewage
10*
10 5
0-1
2
•'Coliform bacteria are present in sewage but die off with time in natural waters.
Their natural habitats are the intestines of warm-blooded
bon dioxide) develops
in
mammals and
the soil.
oxidation ponds, swamps, lakes, and similar environ-
ments.
2.
Protozoa-bacteria.
the treatment of municipal wastewater
In
by the activated
sludge process, bacteria are the primary agents in the conversion of organic wastes
to
stable
bacterial population in
balance
At the same time, protozoa consume and
end products.
in the
limit
the
a predator-prey relationship, thus maintaining a dynamic
microbial population.
The anaerobic digestion of organic matter demonstrates
3. Bacteria-bacteria.
the
interdependence of two groups of bacteria: the acid-forming bacteria, which convert organic matter to fatty (e.g. acetic)
and other organic acids, and the methane
formers, which use these acids to produce methane.
Indicator organisms.
Water used for drinking and bathing can serve as a
vehicle for the transmission of a variety of
human
borne diseases, a detailed discussion of which
tion of pathogens in water
analyses.
ination.
Instead, water
is
is difficult,
is
enteric pathogens that cause water-
The
detec-
in routine
water
presented in Section 8.4.3.
uneconomical, and impractical
tested using a surrogate that
is
an indicator of fecal contam-
Since nonpathogenic microorganisms also inhabit the intestines
bers and are always present in feces together with any pathogens, these
in large
num-
may be used
as
indicators of fecal contamination.
The main
characteristics of a
good indicator organism
are that (1)
its
absence im-
plies the absence of enteric pathogens; (2) the density of the indicator organisms
is re-
lated to the probability of the presence of pathogens; and (3) in the environment the
indicator organisms will survive slightly longer than will the pathogens.
such ideal indicator organism
exists.
However, the presence of
Obviously, no
total coliforms, fecal
coliforms, fecal streptococci, and Clostridium perfringens are regarded as evidence of
fecal contamination
and have been
in use for
assaying water quality for
Of the many indicator organisms, the total
most commonly used. It includes, by definition,
many
coliform group of bacteria
"all
years.
is
the one
aerobic and facultative anaerobic,
gram-negative, non-spore-forming, rod-shaped bacteria that ferment lactose with gas
formation within 48 hours
at
35°C"
(APHA
et al..
1985).
The coliform group
is
com-
275
Applied Microbiology
Sec. 8.3
prised of Escherichia coli,
Enterobacter aerogenes, Citrobacter fruendii, and related
bacteria.
where no
In drinking water,
orms are used
perature test (44.5
cherichia coli
E. coli
is
0.5
In the case
total
conf-
of polluted streams, sewer
Differentiation between total and fecal coliforms
C).
inability
the
is
to
grow
±
44.5
at
0.5
C.
In
may
is
based
temperate climates, Es-
most frequent and predominant type of coliform found
Other members of the coliform group, usually found
intestine.
vegetation,
±
or
their ability
man
of any kind should be present,
and swimming areas, fecal coliforms are enumerated by using the elevated tem-
outfalls
on
coli tonus
as an indication of fecal pollution.
also be encountered in feces, but in low numbers.
in
in the
soil
hu-
and on
In tropical countries,
not the predominant intestinal coliform, so in that case the total rather than the
fecal coliform test
is
a
more
useful measure of pollution.
Fecal streptococci, another type of intestinal bacteria, which are more plentiful in
humans, are frequently enumerated
animals than
in
and the
of fecal coliforms to fecal streptococci (FC/FS ratio)
ratio
ate the source of pollution.
be from
human
With a
ratio
in
conjunction with fecal coliforms,
is
used to differenti-
of 4.0 or more, the pollution
considered to
is
wastes, whereas ratios below 0.7 indicate pollution from animal wastes.
The presence of C. perfringens indicates remote
The enumeration of the bacterial indicators
fecal pollution.
is
carried out by
two
alternative meth-
most probable
ods, namely, the multiple-tube fermentation technique, also called the
number or MPN procedure, and the membrane
two methods are available elsewhere (APHA et
filter
al..
or
MF
method.
Details of these
1985).
8.3.3 Atmospheric and Indoor Air Microbiology
Because of
its
ganisms can
lack of moisture, the atmosphere
and grow.
live
They can
is
not an environment where microor-
survive, however, in their vegetative state to var-
ying degrees, depending mainly on their resistance to drying and, to a lesser extent, on
Those bacteria and fungi
their resistance to ultraviolet radiation.
exist for a very long time in the atmosphere.
a few days in the
form spores can
Some
whereas spores may remain viable for years.
air.
that
Vegetative cells do not survive
more than
protozoa form
cysts,
which
When
conditions are favorable, the spores or cysts break apart and vegetative cells de-
like spores,
enable them to survive adverse conditions for long periods.
velop.
Air
is
important
microorganisms
that
in
is
microbiology because
much wider ranging
up a portion of the particulate matter
particles
and liquid aerosols, or
longer
will
it
tling out
remain airborne.
of the
air in a
in
cysts
provides a mechanism of transfer for
the atmosphere.
fine droplets.
The
it
than that of water.
Of
Microorganisms make
Other particles include dust
course, the smaller the particle, the
formed by protozoa are
matter of minutes.
On
relatively heavy, set-
the other hand, spores of bacteria and
fungi are very small and have been found miles above the earth's surface.
Particles in the
Examples of
atmosphere stem from both natural causes and human
natural sources are forest fires, volcanic eruptions, aerosols
spray and dust picked up by the wind from open fields and vegetation.
activities.
from ocean
Human
sources
276
Microbiology and Epidemiology
are mostly energy related, such as particles
from the combustion of
fuel for
transportation as well as dust created by industrial and agricultural processes.
of the particulate matter
in the
ciety's contribution range
Smoke
atmosphere
from 5
particles, industrial dust,
bulk of particulate matter in the
cles.
45%
to
of natural origin, although estimates of so-
of the
total (Perkins, 1974).
and dust from volcanic eruptions make up the
fields,
likely to carry spores throughout the
oceans, and forests, on the other hand, are
lower atmosphere. Figure 8-1
of the types and numbers of microorganisms found
tion of height.
Air samples taken
Ocean have contained spores of
at
all
in the
in the
1
gives an indication
urban environment as a func-
heights up to 3000
m
over the North Atlantic
Knowledge of
bacteria and fungi.
and distribution of microorganisms
clear that they are dispersed
power and
The bulk
but few microorganisms are attached to these parti-
air,
Wind-generated dusts from
is
Chapter 8
atmosphere
is
the concentration
fairly limited, but
it
is
quite
over the world.
The microbial content of indoor air is of more immediate significance. It is influrate and means of ventilation, by the degree of crowding, and by the types
of activities occurring in the building. Outdoors, the amount of air available per person
enced by the
is
essentially unlimited, and the particulate matter
is
constantly being diffused and dis-
100
50
20
Mold
Spores
10
c
3
o
Bacteria
(Excluding
O
Actinomycetes)
n
>
to
Yeasts
0.5
Actinomycetes
Figure 8-11
0.2
organisms
_L_L
70
air.
_L
500
170
at
Source:
and H.
J.
Types and numbers of
various elevations in urban
T.
J.
Wright, V. W. Greene
Paulus, Journal of the Air
Pollution Control Association 19 (1969):
Altitude
(ft)
337
277
Applied Microbiology
Sec. 8.3
by natural
tributed
air turbulence.
Indoors, the activities of the occupants generate air-
borne microorganisms which are distributed
in
a
is
a graph
Of
diseases.
showing the
bacterial content of a
systems.
filtration
The cough or sneeze or even
microorganisms
number of indoor environments.
the conversation of an infected person
atmosphere are discussed further
in the
in
may
I
L
2000
Bedmaking
Normal Morning
in
200 Average
Activity in
Activity
a Service Hospital
20 Beds-20,000
Military
3
ft
Canteen
a Civilian Hospital Ward
63 Peak
Lunchtime
in
Mess
of
Research
(up to 28 People-3500
31 Average
ft
Institute
3
)
20/65 Crowded Typists' Office
1
15/30 Poorly Ventilated Factory
Shop
Shop
5/25 Large Oily Engineering
0.25/6 Fresh Air on the Outskirts of a
I
I
I
I
200
Town
L
I
400
_L
600
800
Bacteria-Carrying Particles/
ft
3
1000
.
.
.
2000
Air
Key
Peak Value
Lowest Value
Figure 8-12
in
Typical bacterial content of indoor
Air Hygiene.
controller of H.
air.
Source:
Medical Research Council (GB) Spec. Rep.
M. Stationery
Office,
London.
F. P. Ellis
Ser.
in
a
Civilian Hospital
'
924 Peak
50/230 Crowded
re-
Health effects of
Section 8.4.4.
"7
J
Figure 8-12
particular concern are the pathogenic microorganisms that cause respiratory
lease pathogenic organisms into the air and spread the infection.
20/100 Normal
Their
confined space.
relatively
removal depends on the efficiency of the ventilation and
and U.
F.
Raymond, Studies
262, 1948; by permission of the
278
8.4
Microbiology and Epidemiology
Chapter 8
EPIDEMIOLOGY AND DISEASE
8.4.1 Sanitation and Health
The
history of society's concept of, and battle against, epidemic diseases
Winslow (1943).
trated in
Baker (1948) gives an account more
Feachem
with the history of the purification of public water supplies.
present a
ment.
more recent account of
Sartwell (1973)
is
illus-
concerned
(1983)
et al.
and wastewater manage-
a valuable reference on the epidemiology of disease.
this
One of the
asma means bad
earliest theories
or unhealthy
The
well
Subse-
chapter are derived in part from this source.
quent sections of
this concept.
the health aspects of excreta
is
specifically
of diseases was the miasma theory of disease.
air.
The term malaria,
literally,
"bad
air",
Micomes from
was considered to be generThe miasma theory was generally accepted as
cause of disease until the tentative establishment of the germ
etiological or causative agent for disease
ated and resident within the miasmas.
the explanation for the
theory of disease in the seventeenth century.
The Dark Ages, with
from which
tury,
scientists
bubonic plague
their disastrous epidemics,
could learn about disease.
in 1348,
and syphilis
in
A
provided numerous case studies
leprosy epidemic in the sixth cen-
1500 were the major misfortunes.
By
the
sixteenth century, Fracastoro, after careful observation, had developed a clear concept of
contagious disease, but gases rather than microorganisms were thought to be the means
of transfer.
Microorganisms were not seen
of Holland, devised the
first
until
Leeuwenhoek, a seventeenth-century
microscope with
native
sufficient magnification: the science of
microbiology began with his observation of protozoa and bacteria.
The belief in the spread of contagious disease by bad air and the observation that
was more abundant in the filthy, crowded areas of cities, together, led to the sanitary awakening of the early and middle nineteenth century. The cities of those times
contained public squares heaped with decomposing filth, and when these were cleaned
up, the incidences of typhoid, cholera, and typhus were markedly reduced. The conclusion that degree of sanitation had something to do with disease was based on empirical
disease
observation rather than on any theoretical understanding of contagion.
In 1849,
John Snow, a medical doctor, published a pamphlet entitled
On
the
Mode
of Communication of Cholera. Two cholera epidemics in London served to test his theories.
He explained how "minute quantities of the ejections and dejections of cholera
patients
pump
must be swallowed." He backed
epidemic.
He was
able to
show
this
up by
that of
his classic study of the
Broad
Street
77 cholera victims, 59 of them had used
There was a workhouse in the area almost surrounded
which cholera deaths had occurred which remained relatively free of the
water from the suspected pump.
by houses
in
own well. Removing the handle from the Broad Street pump
The source of pollution was identified as a drain that came from
the house of an infected patient and was located within 3 feet of the well.
In the latter half of the nineteenth century, Pasteur, Lister, and Koch finally established the germ theory of disease conclusively. They managed to isolate and grow culepidemic.
It
had
its
ended the epidemic.
tures of
279
Epidemiology and Disease
Sec. 8.4
microorganisms which they were able to show produced specific diseases.
who
role of the carrier (one
is
not clinically
role of the insect host in certain diseases
but
ill
still
were demonstrated
later
The
and the
carries the infection)
and explained how
disease could be transmitted with no apparent contact between infected patients.
The
potential of water to spread massive epidemics
is
early part of this century, attempts to control typhoid fever
well
known
today.
In the
and various enteric diseases
number of patents on the use of oxidizing agents and other water purification
The first large-scale application of chlorination was in 1908 at the Boonton
Reservoir of the Jersey City Water Works in the United States. Since 1920, enteric disresulted in a
techniques.
eases have been almost entirely eradicated in most parts of developed countries. However,
in the less
developed nations, half the population
75%
water supplies, and
still
does not have adequately protected
lack safe waste disposal systems (Eckholm, 1977; 1982).
Table 8-6 compares the death rate and average
the developed
and developing regions of the world.
death rates and higher
and medicine
in the
life
expectancies
at birth
The
table clearly
shows
between
the lower
expectancies attributable to better public health, sanitation,
life
developed countries.
The
statistics for
Africa and South Asia are
similar to those of developed countries over 100 years ago.
8-6 ESTIMATED CRUDE DEATH RATES AND
EXPECTANCIES FOR MAJOR AREAS AND REGIONS
OF THE WORLD, 1965-1970
TABLE
Crude death
rate
Major areas and
(deaths per 1000
regions
population)
World
total
Developing regions
More developed
regions
Africa
LIFE
Expectation of
life
at birth (years)
14
53
16
50
9
70
21
43
14
52
Asia (excluding the CIS)
East Asia
Japan
South Asia
Europe (excluding the CIS)
Latin
America
North America
Oceania
CIS" (former
Source:
USSR)
7
71
17
49
10
71
10
60
9
70
10
65
8
70
U.N. (1973).
"CIS Commonwealth of Independent
States.
8.4.2 Pathogens
A pathogen
is
an agent that causes infection
in
a living host.
It
acts as a parasite
within the host or host cells and disrupts normal physiological activities.
This disrup-
280
tion
Microbiology and Epidemiology
is
what causes the symptoms of disease, such
Chapter 8
as high temperature, an upset in the
digestive process, a change in blood chemistry, and other indications of infection.
means
Infection, by definition,
that a disease-producing agent
who may
multiplying within the host,
or
may
not have
symptoms of
growing and
is
the disease.
The
presence of the agent stimulates the host to produce antibodies to combat the agent.
Depending on
the effectiveness of the antibodies, the result can be sickness, recovery, or
may
death, or the antibodies
limit the
toms of infection are not apparent
growth of the agent
(i.e.,
the host
which symp-
to the point at
infected without appearing to be
is
sick).
The
Virulence
pathogen to
ability of the
is
a relative concept,
inflict
damage on
the host
comparing the attacking
is
termed
ability of the
its
virulence.
pathogen to the
Virulence can be influenced by factors inherent to the
defensive ability of the host.
pathogen and the host, as well as by environmental conditions.
An infection
is
a pathological condition due to the growth
of
microorganisms
a host.
in
A pathogen is an agent that causes infection in a living host.
A toxin is a poisonous substance from certain organisms (e.g.,
bacterial tox-
ins).
Virulence
is
the capacity of a microorganism to cause disease.
Pathogenic organisms that are virulent enough to infect humans under appropriate
conditions include
some
species of bacteria, viruses, algae, and fungi, as well as proto-
zoa and helminthic (parasitic worm) organisms.
groups of microorganisms, some
common
Table 8-7 indicates, for the various
diseases and the
means by which
the patho-
gens are transmitted.
Virulent pathogens cause epidemics which affect an abnormally high
The
number of
numbers of people affected need not be
large.
For example, a few cases of botulism or food poisoning occurring simultaneously
in the
people
in a localized area.
actual
same area could be considered an epidemic because
increase in head colds
As we
an epidemic.
parasitic
worm
among
learned, earlier, an
infection,
rural population in parts
the disease
schoolchildren in the
which
is
fall
endemic disease
prevalent
among
is
is
is
so rare.
Yet a sharp
normal and not regarded as
one
like schistosomiasis, a
a particular group, in this case the
of Africa.
For an epidemic to occur, three factors must be present: an infected host, a
number of noninfected
An
potential hosts,
and a mechanism of transfer between the two.
infected host implies the presence of a virulent pathogen.
brings about
its
own
duction of antibodies that destroy the pathogen.
there
must be
The pathogen eventually
destruction either by destroying the host or by stimulating the pro-
a continuous supply of
Therefore, for an epidemic to persist,
new nonimmune hosts for the pathogens to invade.
comes a time when the combined fac-
All epidemics are self-limiting in that there
tors of a shortage of
new
hosts, increased distance
between infected and uninfected
Sec. 8.4
TABLE
281
Epidemiology and Disease
PATHOGENIC ORGANISMS
8-7
Disease
Agents and vectors
Bacterial
Anthrax
Contaminated animal hair wool, hides; contaminated undercooked meat; inhalation of
Botulism
A
Brucellosis or
Contact with infected pigs,
airborne spores.
thermolabile toxin produced in nonacid food under anaerobic packaging; organisms
from
undulant fever
Cholera
soil
and
intestinal tract
of animals.
cattle, goats,
and horses; use of raw milk and milk products
are the cause of sporadic cases and outbreaks.
Feces of cases or carriers contaminate water, milk, food, and
demic cholera
Plague, bubonic
and sylvatic
Salmonellosis
is
wave of
flies; initial
epi-
waterborne.
Organism transmitted by
fleas
from
rats
and wild rodents; contaminated vomitus of
flea
enters skin during biting.
Feces of animals and infected persons contaminate foods; organisms multiply
in unre-
frigerated foods to deliver massive doses.
Shigellosis or bacillary
dysentery
Four groups of the dysentery bacillus. Shigella dysenteriae,
sonnei, leave via feces and return to the
mouth
S.
and
flexneri, S. boydii,
S.
directly or via water, flood, flies, or
fecally soiled objects.
Typhoid and para-
Feces and urine of cases and carriers contaminate water, milk, food, and
flies.
typhoid fever
Rickettsial
Endemic typhus and
epidemic typhus
Fleas transmit the rickettsiae from rat to rat and from rats to humans; organisms in
fleas' feces enter
through fresh bites and abrasions.
Viral
Infectious hepatitis
Outbreaks have been related
Yellow fever
Urban yellow fever from human cases by Aedes aegypti; jungle yellow fever from mon-
to
contaminated water, milk, and food, including
keys and marmosets by forest mosquitoes; presence of A. aegypti
shellfish.
in large areas
of
Africa and Southeast Asia requires vigilance despite absence of yellow fever.
Protozoan
Amebiasis or amebic dysentery
Hand-to-mouth
transfer,
contaminating raw vegetables,
Three Plasmodium types are transmitted from person
Malaria
flies,
soiled hands of food han-
dlers, water.
to
person by one of about 20
anopheline mosquito species, which are efficient vectors.
Giardiasis
Cysts of Giardia lambda
Cryptosporidiosis
Oocysts of Cryptosporidium parvum are shed
in
feces of
humans contaminate water and cause
in feces.
Outbreaks related
diarrhea.
to
contami-
nated water supplies.
Helminthic
Ascariasis or
roundworm
Hookworm
dis-
eases
Tapeworm
Soil contaminated with feces of infected persons contains
of such
soil
or raw foods after soil contact
is
embryonated eggs; ingestion
the infection route.
Penetration of skin by larvae developing in soil contaminated by feces of infested persons.
diseases
Caused by Taenia solium (swine) and Taenia saginata
common among meat consumers
(cattle).
Intestinal parasites,
in livestock areas (e.g. parts
of N.
America and
Mexico).
Schistosomiasis
Eggs of Schistosoma mansoni and
matobium with urine
japonicum pass with feces from humans and
S.
to cycle in
form which penetrates human skin; domestic animals and wild rodents host
Source: Adapted from Sartwell (1973),
Feachem
et al.
(1983).
S.
he-
water through specific snail types, to the cercaria
S.
japon-
282
Microbiology and Epidemiology
and perhaps a reduction
ease.
Unfortunately a tremendous loss of
evidenced by the loss of
new outbreaks of
virulence lead to very few
hosts,
in
life
Chapter 8
can occur before the limit
is
the dis-
reached, as
one-third of the population of medieval Europe in the
at least
fourteenth century from bubonic plague.
In
England, about one-third of the population
of A\ million perished in a 2\ -year period between 1347 and 1350 (Ziegler, 1969).
Why some
microorganisms are more virulent than others
croorganisms are not pathogenic and are saprophytes,
few organisms
that are facultative
not clear.
is
There
are,
of course, pathogens that are ob-
Most pathogens,
ligate parasites, such as viruses that cannot live outside a host cell.
though, can grow outside a host until a suitable portal of entry for infection
substances
teristics,
of the ways pathogens cause disease
known
but
it
is
in the virulence
Not
as toxins.
all
and
live
pathogens or opportunists. These may cause
disease under very special circumstances.
One
Most mi-
organisms that
is,
However, included among the saprophytes
feed on dead and decaying organic matter.
are a
that
found.
is
through the production of poisonous
is
pathogens have been shown
have these charac-
to
clear that the production of toxins and their potency are major factors
of
some microorganisms.
roundings are called exotoxins.
dotoxins and are not released
Those
until the
that
The toxins
remain
that are excreted into the sur-
in the
microorganism
microorganism are called en-
dies.
The amount of exotoxin
released at the death or breakup of the cell can also be significant.
Exotoxins are gen-
more potent than endotoxins.
In some cases, enzyme production by pathogens is thought to contribute
virulence. Enzymes may help spread the disease through the host by increasing
erally
to their
the per-
meability of cell walls, by destroying specific tissues and cells, or by enabling the path-
ogen
to resist attack
by antibodies.
The capsular material surrounding some pathogenic bacteria may affect their virulence. The capsules themselves are nontoxic, but they seem to protect pathogenic organisms from attack by antibodies.
can lose
that are
its
If this
pathogenicity or virulence.
capsular material
is
removed, the pathogen
However, there are many capsulated bacteria
nonpathogenic, and the virulence of some pathogens
is
unaffected by the pres-
ence or absence of a capsule.
Each pathogen has a
specific portal of entry into
its
host.
The
enteric pathogens
are those that cause disease in the alimentary tract or the digestive system.
Organisms
producing typhoid, dysentery, gastroenteritis, and cholera are examples of enteric pathogens.
They must be ingested
to cause infection.
be inhaled. Others must enter through abrasions
infections, or enter the circulatory
gens grow
bitten
in the
Organisms
in the skin,
that attack the lungs
where they can
system and spread through the body.
set
up
Many
must
local
patho-
bodies of animals or insects, and the only humans infected are those
by these creatures.
The
infective agent usually enters
and leaves the host by the same route.
ample, the enteric pathogens enter and exit via the digestive system.
They enter
mouth, continue through the alimentary canal, and
exit with the feces.
pathogens that are inhaled are released
from the nose or
in secretions
For exvia the
Respiratory
throat or
by aer-
osols of these secretions from sneezing and coughing, which carry the microorganisms
through the
air.
Pathogens
that
infect the
skin through cuts and abrasions are dis-
283
Epidemiology and Disease
Sec. 8.4
charged
drainage from skin lesions and abscesses.
in the
After the microorganism leaves
must survive
transfer
ter,
until
it
mechanisms.
reaches a
Most diseases
contaminated airborne
diate
hosts
(called
new
In
it
an unfavorable environment and
in
is
Figure 8-13
is
a representation of various
are spread indirectly, by tainted food, polluted
by
particles, or
vectors).
host,
its
host.
bites
remainder of
the
wa-
from infected insects or other intermesection
this
we examine
the
waterborne, airborne, and insect- and rodent-borne diseases, since these are of primarj
interest in the
environmental
field.
Person
lo
Person
~^^
Indirect
Contact
-—*
Microorganisms
Human
Host
Animal Host
Figure 8-13
Transmission
Transmission of disease.
of
Source:
Pelczar et
pathogenic microorganisms from person
from direct contact
to fomites
and by intermediate
to
vectors.
al.
(1977)
person occurs
in
a variety of ways, ranging
Animals may also transmit pathogens
to
humans
8.4.3 Waterborne Diseases and Water Quality
Diseases transmitted by water are almost
all
of intestinal origin.
fected hosts or carriers can get into a water supply or
swimming
Fecal matter from inarea in a
number of
284
Microbiology and Epidemiology
common
ways. The most
by
is
direct discharge of
Pit privies located too close to a well or
raw sewage
Chapter 8
into the receiving water.
stream can also be a source of contamination.
Specific outbreaks of disease have been traced to cross-connections between water and
sewer pipes, to breaks
in
water mains, and to contamination of water supplies during
flooding or temporary failure of a sewage treatment
Pathogenic organisms are unable to grow
several days.
host for a
in
facility.
water but
much
survive in water for
For example, the spores of Clostridium
longer time.
gen responsible for tetanus infection, can survive for years
Some
may
Those pathogens capable of forming spores or cysts can
common
of the
types of waterborne disease are salmonellosis, shigellosis
these diseases occur periodically in
America because
patho-
in nature.
cholera, infectious hepatitis, amebiasis, giardiasis, and schistosomiasis.
all
exist outside a
tetani, the
many
Epidemics of
parts of the world but are rare in North
virtually all of the population is served
by adequate water supply and
waste disposal systems.
Salmonellosis.
enteritis,
Three forms of salmonellosis occur
septicemia (blood poisoning), and enteric fevers.
in
humans: acute gastro-
These complications
in
hu-
The common symptoms in
gastroenteritis are diarrhea and abdominal cramps, followed by fever, which lasts 1 to 4
days. These may be severe, but fatality rates are low. The species most commonly iso-
mans
are caused
lated
from patients with salmonella
by a variety of species of Salmonella.
gastroenteritis
is
S.
typhimurium.
During
septi-
may
cemia, some bacteria spread to the spleen, kidneys, heart, and lungs, and lesions
develop on these organs.
only in humans.
Typhoid fever (an enteric fever) caused by
S. typhi,
develops
After being swallowed, the bacteria cause a generalized infection, and
following an incubation period of 10 to 14 days, a fever develops (40°C) that lasts several
Accompanying
weeks.
About
3%
the fever are
of typhoid patients eventually
abdominal pain and bowel disturbances.
become chronic
carriers of the disease.
recover from the symptoms but continue to harbor the microorganisms.
ally live less than
Chloramphenicol
1
week
in nature but last
much
S.
They
typhi gener-
longer in very cold water or
ice.
effective in the treatment of salmonellosis.
is
Shigellosis.
Shigellosis
is
also called bacillary dysentery or acute diarrhea.
is
a disease associated with poor sanitation, overcrowding, and un-
safe water supplies.
A
number of species of
mans. Shigellosis
characterized by abdominal cramps, diarrhea, and fever following
Like typhoid fever,
it
is
an incubation period of
1
to
4 days.
phenicol or ampicillin are effective
not been as
much
the genus Shigella are pathogenic for hu-
Antibiotics such as the tetracyclines and chloramin the
treatment of bacillary dysentery.
There has
success in preventing shigella infection as there has been in control-
ling typhoid fever.
Cholera.
cholerae (also
food.
V.
Humans
acquire cholera by the ingestion of bacteria
comma), which may be present
The ingested
in
known
as Vibrio
polluted water or contaminated
bacteria multiply in the small intestine and, after 2 to 5 days, cause
abdominal cramps, nausea, vomiting, and profuse diarrhea
that
may
lead to dehydration.
285
Epidemiology and Disease
Sec. 8.4
shock, and death.
Cholera
endemic
is
Bengal
in the
where several thousand cases are reported each
demic
state
of India and
Bangladesh,
in
Areas where cholera remains en-
year.
are typically low -lying farmlands subject to periodic flooding
ence a hot. humid climate and high population densities.
and which experi-
Since the turn of the century,
cholera has been confined mainly to Southeast Asia, with occasional incursions into
Recent outbreaks of cholera are not positively identifiable as water-
neighbouring areas.
many
borne, since there are
tion
Good
other direct and indirect contact mechanisms.
sanita-
Sulfonamides and
practices play an important role in the control of cholera.
antibiotics are useful in treatment of the disease.
A
Infectious hepatitis.
be transmitted by water
viral disease, infectious hepatitis
has been shown to
number of epidemics. Typical symptoms of
in a
the disease are
of appetite and energy, headache, and back pains. After a few days the fever
fever, loss
may
subside, and recognizable jaundice (a yellow
ease
is
and
rarely fatal,
it
tint in
suspected that there
is
may
the skin)
The
appear.
fected people
who do
the disease.
There was a large waterborne outbreak of infectious hepatitis
Delhi, India, in
sewage.
show
1955-1956
time provided
the viruses.
in the
symptoms
period.
but
who
can
from contamination of the
was no increase
same
this
clinical
resulting
Surprisingly, there
phoid fever, during
shown
not
still
in enteric bacterial infections,
Chapter
For these reasons
Many
11).
and culturing viruses make
it
is
most important
filters
and have been
to prevent
Other
contamination
viral diseases that
difficult
it
to
may
in isolating
determine conclusively the mechanism of
situation.
Amebiasis
is
also called
amebic dysentery.
stomach cramps and diarrhea. The causative organism
Its
such as ty-
viruses survive outside a host for
be waterborne are epidemic gastroenteritis and poliomyelitis. The problems
tolytica.
New
water treatment plant were sufficient to destroy the bacteria but not
long periods of time.
Amebiasis.
in
water supply by
This suggests that the chlorine dosage and contact
of water supplies rather than depend on later purification.
any given
in-
carry and pass on
city's
Viruses are small enough to pass through most sand
to resist chlorination (see
transfer in
dis-
probably a large proportion of
is
normal habitat
is
is
the colon or large intestine.
on bacteria and cellular debris, and produces cysts
Its
the protozoan
It
is
symptoms
Entamoeba
are
his-
relatively small, feeds
that pass in the feces to spread the
infection. Under conditions not yet understood, the protozoa penetrate the host tissue,
become pathogenic, grow much larger, and continue to reproduce. Other amoebae remain small after division and become encysted. When the cysts are exposed to an ex-
environment and then swallowed, they are capable of returning to a vegetative
ternal
(active) condition.
Although not as
resistant to adverse conditions as fungal
withstand the normal chlorination of drinking water.
and by
ultraviolet irradiation
from the sun.
spores, the cysts can
However, they are
In water, cysts survive
killed
longer
at
by drying
low tem-
They can survive for over
month in ice but for only
or 2 days at 34 C.
Although endemic in hot tropical areas, severe outbreaks of amebiasis have occurred in
peratures.
temperate areas as well.
I
I
286
Microbiology and Epidemiology
Giardiasis.
Giardiasis
is
Chapter 8
caused by Giardia lamblia, a flagellated protozoan of
symptoms are abdominal cramps, diarrhea, fatigue,
The mean duration of acute illness is often 2 to 3 months. An
person may excrete more than 10 6 cysts per gram of feces. The cysts are
the small intestine.
Characteristic
anorexia, and nausea.
infected
ovoid, refractile, and attain a size of 8 to 14 pirn by 6 to 10
may
the external environment, the cysts
Most waterborne outbreaks of
water.
pm. Passed
in the feces to
survive for months and contaminate food and
North America are associ-
giardiasis reported in
ated with smaller water supplies and recreational areas, where the only treatment
Giardia cysts are not destroyed by chlorination
chlorination.
commonly used
times
in
water treatment plants, nor are they effectively removed by
rapid sand infiltration unless
Cryptosporidiosis.
and animals,
toms of cryptosporidiosis
to
30 days.
it
is
preceded by coagulation and flocculation (Chapter
Cryptosporidiosis,
far
It is
—
more
diarrhea, abdominal pain, nausea
are shed in the feces of infected
Of
to 5
pm
mammals and
Cryptosporidium are widely distributed
1990).
gastrointestinal
serious than giardiasis and there
Cryptosporidium oocysts (eggs), 3
ease.
a
and vomiting
is
in size, spherical or
Cryptosporidium (Okun, 1993).
that
occurred
last
from 8
for the dis-
ovoid
in
shape,
transmitted via the fecal-oral route.
environment (Lechevallier
in the aquatic
the surface water supplies in the United States, about
tain
1).
in
—
no treatment
1
humans
The symp-
illness
caused by Cryptosporidium, an enteric protozoan parasite.
is
was
dosages and contact
at
80% was
et al.,
found to con-
Several confirmed outbreaks of cryptosporidiosis
North America and England were associated with water treatment
in
plants located on rivers receiving agricultural runoff, a
common
source of Cryptosporid-
Milwaukee Wisconsin, about 30,000
people were affected (Parmelee, 1993), 47 of whom died (Gooderham, 1993). Here,
In the 1993 outbreak of cryptosporidiosis in
ium.
too,
animal feces
in agricultural
runoff were thought to be the source of the contamina-
tion.
Because of
tion
their thick cell wall,
by the usual drinking water
stronger oxidizing agent, seems
Cryptosporidium oocysts are resistant
disinfectants, chlorine
more promising, but
at present,
Ozone, a
physical removal of the
oocysts by coagulation, flocculation, sedimentation, and filtration
means of
to inactiva-
and chlorine dioxide.
is
the
most suitable
control.
Schistosomiasis.
blood flukes; parasitic
ease,
endemic
ple.
Symptoms
Also known as bilharzia, schistosomiasis
worm members
to Africa,
of the genus Schistosoma.
It
is
is
caused by
a chronic dis-
South America, and parts of Asia, and affects millions of peo-
are enlargement of the liver, diarrhea, and anemia.
Schistosoma, are
not strictly microorganisms, and they are not necessarily transmitted by the fecal-oral
route.
The
life
cycle of Schistosoma
is
shown
parasite in the infected person's intestine
water into small motile miricidia.
they will die.
Figure 8-14.
These must find a
The eggs are laid by the
The eggs hatch in
in the feces.
snail host within a
few hours, or
After a period of incubation, infected snails excrete cercaria, which can
survive for 2 or 3 days in water.
bloodstream.
in
and passed
They mature
Cercaria attach to
in the liver into adults.
human
skin and penetrate to the
Although the
life
cycle and control
|
287
Epidemiology and Disease
Sec. 8.4
Masses
on
Worm
in
of
eggs
laid
intestinal wall
bloodstream
Eggs excreted
Eggs hatch
to
miricidia
Cercaria penetrate skin
Miricidia infect snails
Figure 8-14
Source:
Life cycle of Schistosoma.
R. D. Barnes. Invertebrate Zoology, 3rd ed.
methods are understood, the disease
is
Mitchell (1974).
W.
(Philadelphia:
actually
[Permission by
B. Saunders. 1974).
on the increase
in
endemic
areas.
Lack
main obstacle to its control. Unfortunately, the increase in
irrigation systems and water impoundments associated with hydroelectric projects that
provide energy necessary for the development of tropical countries also results in an in-
of adequate sanitation
is
the
crease in the numbers and spread of the snail vector.
with poison
is
only partially effective, because
it
is
mild form of schistosomiasis, referred to as swimmers
Canada and
Water
quality.
As explained
in
Section 8.3.2,
enumerate the pathogenic organisms
that
Therefore, to monitor water quality, water
that are present
mon
itch,
occurs
at
life.
A
times in parts of
the United States.
ferentiate, or
wastewater.
Control of the snail population
often lethal to other aquatic
bacterial
when
fecal contamination occurs.
is
it
is
may
impractical to detect, dif-
be present
in
water and
tested for indicator organisms
The coliform group
is
the
most com-
indicator of fecal contamination, and standards (legal requirements) or
guidelines (objectives or goals) have been established by most countries to limit the ge-
288
Microbiology and Epidemiology
ometric
mean
Chapter 8
density of total and/or fecal coliform bacteria in water used for different
Representative values are as follows:
purposes.
Maximum
Water use
mL
Fecal
Total
Drinking water
Raw
allowable coliforms per 100
1
5000
water supply
500
100
1000
Recreational
—
Treated wastewater
200
Water quality standards and guidelines for water supplies and effluent receiving
waters are considered in detail
in
Chapters
11
and
12.
8.4.4 Airborne Diseases
Respiratory diseases such as pulmonary tuberculosis (bacterial), influenza
pulmonary mycosis (fungal) are transmitted by
from the lungs, sinuses, and bronchioles leave the
Coughing, sneezing, and talking produce aerosols or
these organisms.
mediate objects
and
fine droplets
that
may
contain
Saliva and nasal discharges can also be transferred by hand to inter(e.g.,
The
bedclothing).
direct contact, the latter indirect contact.
not travel very far through the
have to be
(viral),
The pathogenic microorganisms
infected host via the mouth and nose.
air.
in close
air,
aerosol
method of
transfer
generally termed
is
Droplets expelled by coughing or sneezing do
so to be infected directly by such droplets, people
contact with an infected person.
diate objects dry out, leaving a dry nucleus to
The
droplets that
fall
on interme-
which pathogens may be attached.
Airborne infections are those transmitted by the pathogens carried on the very
small droplet nuclei, which
become resuspended,
circulated by the
the
body via the respiratory system (Figure 8-15).
sists
cally as a
passageway for
of the bronchioles
diameter
—and
—
which
in
each lung.
The lower
particles that can penetrate to the
the size range 0.1 to 1.0 |im,
which
is
m
:
of entry
is
cm
in
end of each bron-
(600
in
2
ft ).
in
from viruses through fungal spores
Larger particles are removed by the defense mechanisms of the
whose porThey could not peneairstream. Examples of
the alveoli or bronchioles are necessarily airborne.
trate that far into the
functions basi-
lower respiratory system are those
the size range
upper respiratory system, and most smaller particles are exhaled.
tal
a branching of
It
There are several hundred million alveoli
a healthy lung, providing an interior surface area of about 56
to single bacterial cells.
—
respiratory system con-
are clusters of small air sacs at the
chiole that are about the size of a pinhead.
dust,
respiratory system con-
the very small ends of the bronchial tubes about 0.05
the alveoli,
The only
by
The upper
and smaller tubes
air to get into the lungs.
carried
particles are taken into
of the nasal cavity, the trachea (or windpipe), and bronchial tree
the trachea into successively smaller
sists
air,
These
or recirculated through inadequate ventilation systems.
lung unless they were suspended
in the
Infections
289
Epidemiology and Disease
Sec. 8.4
Nasal
Terminal
Cavity
Bronchiole
Oral
Cavity
Larynx
Trachea
Respiratory
Bronchiole
Terminal
Bronchioles
Alveoli
Bronchial
Tree
Right Lung
Left
Lung
The
The major anatomical features
of
human
respiratory
system
terminal bronchial and
alveolar structure of the
human
Figure 8-15
Human
respiratory system.
Source:
Perkins
(
lung
1974).
lower respiratory infections are pulmonary tuberculosis, pulmonary mycosis, and pneu-
monic forms of plague.
As air is drawn into
the lungs,
must negotiate a number of sharp bends
it
in the
upper respiratory system. The larger particles cannot turn the corners and therefore impact against the lined walls of the sinuses, trachea, and bronchial tree, which are the
portal of entry for diseases of the
and the acute
and mumps.
upper respiratory system such as diphtheria, influenza,
and acute contagious diseases such as measles
viral respiratory diseases,
Larger particles can reach their portal of entry more easily than can parti-
system and therefore are harder
cles responsible for infections of the lower respiratory
to classify
would reach
as
For example, pathogens deposited
airborne infections.
the upper respiratory system.
in
The airborne mechanism, though,
the
is
mouth
certainly
important.
Pulmonary tuberculosis
one of the main causes of
million
new
is
most significant of the airborne diseases.
the
disability
and death throughout the world.
remains
1
The World Health Organization estimates that this
number of cases and that tuberculosis is responsible
cases reported annually.
represents only
10%
of the actual
for an estimated 2 to 3 million deaths per year.
most prevalent
bacillus
It
There are over
in areas
(Mycobacterium tuberculosis),
growth needs are relatively simple, but
is
it
many contagious diseases, it is
The causative agent, the tubercle
Like
with a low standard of living.
a non-spore-bearing rod-shaped bacterium.
Its
grows quite slowly, with a generation time of
290
Microbiology and Epidemiology
18 to 24
h.
infectants.
The
They
bacilli
are
can be destroyed by exposure to direct sunlight, heat, and dis-
more
resistant to
chemical agents and antibacterial agents such as
most pathogenic organisms.
penicillin than are
Chapter 8
The length of time they survive
environment depends on the nature of the secretions
in the
which they are contained.
in
The
bacteria are resistant to drying and therefore remain viable on droplet nuclei, as noted
Legionnaire's disease
earlier.
monic bacterium
that
Pulmonary mycosis
gal
another respiratory illness caused by a small pneu-
is
can be transmitted through contaminated ventilation systems
is
overtaxed and
sult in suffocation, but usually the heart is
stage
is
reached.
fails
re-
Other airborne infections of a specialized nature are those of surgical
laboratory personnel working with pathogenic organisms.
dous success
curbing infections by
infection during surgery
is
airborne.
been unsuccessful.
The tremen-
techniques in surgery indicates that
strictly aseptic
However, controlling airborne or suspected
borne diseases by limiting the number of bacteria or dust particles
ally
fun-
This can
before the suffocation
wounds and of
in
The
a fungal infection of the bronchioles and alveoli.
growth destroys these structures and thus reduces the lungs' capacity.
In hospital experiments, reductions of
50
in the air
to
75%
in the
of airborne bacteria did not result in any significant decrease in infection.
microorganisms
for effective control, access of the
to the
It
air-
has gener-
number
seems
that
atmosphere must be prevented.
Containing the disease, therefore, depends on early diagnosis followed by proper medical treatment
and complete isolation of the patient or source of infection.
8.4.5 Insect- and Rodent-borne Diseases
The bloodstream
facilitate
is
the portal of entry and exit for a
the entry of the
been incriminated include mosquitoes, sand
few of these pathogens are vector
particular pathogen to a
number of pathogens.
microorganisms through the host's
human
specific
flies,
(i.e.,
skin.
Insect bites
Insects that have
tsetse flies, ticks, fleas,
and
lice.
A
a specific species of insect transfers a
host).
in insect-borne diseases. The simplest
humans back to insects, as illustrated in Figure 8-16. The
insect must be one that feeds on humans preferentially, and it must have a high susceptibility and infectivity to the disease. The ability to meet all of these conditions is relatively rare, but when the conditions are met, outbreaks of disease can be explosive.
Examples are malaria and trypnosomiasis (sleeping sickness),* protozoan infections
There are two basic epidemiological cycles
one
is
a cycle
from insects
to
from the female Anopheles mosquito and the
One of
tsetse
fly,
respectively.
number of cases is maThe causative organism is one of four species of parasitic protozoa (of the genus
Plasmodium) that destroys the host's red blood cells. Humans are the primary reserthe worst infectious diseases in terms of the annual
laria.
voirs in areas of the world
lation has
where malaria
is
hyperendemic
(i.e.,
where the adult popu-
become immune through continuous transmission of
the disease and acts
merely as a reservoir for the protozoa).
A
viral disease (viral encephalitis)
common
in
Manitoba. Canada,
is
also called sleeping sickness.
291
Epidemiology and Disease
Sec. 8.4
Vertebrate
Insect
Humans
Figure 8-16
^
Humans
Insect-human cycle
Figure 8-17
insect-borne
in
Insect
Insect-lower vertebrate cycle
in
rodent-borne
diseases
diseases.
The most common epidemiological cycle
illustrated in Figure
is
volves a cycle of insect to lower vertebrate and back to insect, with
The
sional tangent infection.
infection of
yellow fever
and bubonic plague
(viral)
humans
(bacterial).
in-
as an occa-
usually a dead end in the cycle
is
Examples of diseases
(urban yellow fever being an exception).
8-17 and
humans
affecting
Mammals and
humans
are
birds act as reser-
voirs for the pathogens.
Yellow
many
fever, an insect-borne viral infection, has
countries
which
in
The basic
and parts of Africa.
and monkeys. There
erentially bites
been essentially eliminated from
was once endemic; however,
it
it
still
exists in the
reservoir cycle includes mosquitoes of the
one urban species, Aedes aegypti, which
is
humans).
is
West Indies
Aedes species
anthropophilic (pref-
one or more of these feed on an infected person, an epi-
If
demic of urban yellow fever may
start.
humans infected only tangentially. It is
was often noted (but the significance was not
understood) that immediately preceding the plague outbreak there would be an epidemic among the rat population. When a infected flea bites a human, bubonic plague
develops. Plague bacilli are often found in the sputum of infected persons and can be
Plague
is
actually a disease of rats, with
transmitted from
by
rat to rat
spread from person
crowded areas.
to
fleas.
person
It
by direct contact or through airborne infection
Plague epidemics had a profound effect on European society
century.
It
is
Plague
South Vietnam, where there
squirrels, gerbils,
is
uncommon
is still
Rickettsia
number of
cases.
as
as
marmots, and wild guinea pigs are also reservoirs of plague and could
is
lie
here because of
epidemiological importance
its
between those of bacteria and
the rickettsial diseases, the typhus
in
human
population.
a general term given to a small group of microorganisms
and characteristics
ness and misery
few areas, such
Wild rodents such
today, but persists in a
a significant
infect the rat population, thereby threatening the
Of
the fourteenth
estimated that one-third of the population died of the black death, a form
of bubonic plague.
eases.
in
in
the past.
in
viruses.
The group
whose
is
size
included
causing typhus and typhus-like dis-
group has been responsible for much sick-
There are two organisms responsible for typhus fevers:
Rickettsia prowazekii. which causes epidemic typhus and under natural conditions infects only
humans and
the
occasionally transmitted to
human body louse, and Rickettsia typhi, common
humans by rat fleas. The rickettsiae are obligate
in rats
and
intracellu-
292
Microbiology and Epidemiology
lar parasites in fleas, lice, mites,
and
Chapter 8
and are often pathogenic for humans. These
ticks
small, nonmotile microorganisms appear as spherical forms about 0.3 |im long.
Antibiotics such as the tetracyclines and chloramphenicol are effective against
tion.
epidemic typhus
humans.
in
Control of insect-borne diseases
initiated
is
through control of the vector organ-
Spraying the rooms of infected households with pesticides isolates the host from
ism.
The draining of swamps can
the vector organism.
produce.
If the
epidemiological cycle
Unfortunately,
led.
the
in
is
ical climate,
which
vector organisms.
ing countries
is
mosquitoes to
affect the ability of
countries
lack
The problem
is
of
makes
by the trop-
congenial for effective incubation of microorganisms within the
Presently, the strategy of the
World Health Organization
slowly increase the general level of public health throughout a region by
8.5
funds
sufficient
further aggravated
control of these diseases rather than total eradication.
is
re-
effectively broken, the disease can be control-
developing
eradication of vector organisms difficult.
tion
Rick-
chemical disinfection and are destroyed by heat and dehydra-
ettsiae are susceptible to
for develop-
The goal
way
is
to
of educa-
and comprehensive planning as well as by control techniques.
NONINFECTIOUS DISEASES
developed countries, infectious parasitic diseases have been brought under control
In the
and
in
some
areas virtually eradicated.
This
is
due
the disinfection of water supplies, increased care
and the medical advances
infected people.
In these
in drugs, antibiotics,
same
to the sanitary disposal of wastes,
and cleanliness
in
food preparation,
immunization, and the early diagnosis of
countries, however, there has been an increase in the
proportion of deaths resulting from degenerative ailments or noninfectious diseases such
as cancer, diseases of the heart
and the circulatory system, bronchitis, and emphysema.
Part of the reason for the shift to the noninfectious diseases
portion of the population
creases with age.
is
is
that a greater pro-
older and the incidence of death due to these diseases in-
Table 8-8 gives the percentage distribution of deaths by cause
model populations from a U.N. study on world mortality
trends.
Model
A
is
in
populations in developing countries, with a young age structure (approximately
less than 15 years old)
of populations
in
and an average
expectancy of 50 years.
Model B
developed countries, with a relatively old age structure (only
than 15 years old) and an average
It is
life
life
expectancy
at birth
two
typical of
is
45%
typical
20%
less
of 70 years.
also believed, but difficult to prove, that over time the pollution of our air and
water with inorganic and organic chemicals contributes to these degenerative diseases.
air which
The Minimata Bay merpollution episodes in London in De-
There have been well-documented episodes of gross pollution of water and
have clearly resulted
cury poisoning
cember 1952
in
in
Japan
an increase
in the
in
noninfectious diseases.
1950s and the
air
are frightening reminders of the effects that pollution can have
In the former,
methyl mercury compounds
in industrial effluents
dumped
on humans.
into Japan's
Minamata Bay were concentrated in fish, which were, in turn, consumed by
Between 1953 and 1960, 111 cases of mercury poisoning were recorded. In
residents.
the latter
293
Noninfectious Diseases
Sec. 8.5
PERCENTAGE DISTRIBUTION OF DEATH BY CAUSE
TABLE 8-8
Model
Model A:
young age
life
Cause of death
expectancy
Heart and circulator) diseases
6.5
5.6
16.4
18.7
46.5
Violence
All others
Source: Adapted from U.N.
100.0
34.1
Cancer
4.3
5.2
37.3
25.4
(1973).
mass caused a buildup of
a temperature inversion and the resulting static air
smoke and SO :
in
mately 5 days.
This incidence
Generally,
London
among
deaths, primarily
to five times their
is
considered responsible for between 1500 and 4000
those already suffering from respiratory diseases.
ant in the water or the atmosphere.
The
health effects in animals resulting from admin-
istering large doses of a particular pollutant
environment, however, pollutants exist
with too
many
may
be determined
in the laboratory.
In the
very small concentrations and in combination
in
other factors for particular effects to be attributed to a single cause.
much more
be
difficult to
normal levels for a period of approxi-
impossible to attribute a particular health effect to any one pollut-
is
it
expectancy
70 years
100.0
Infectious, parasitic diseases
case,
life
50 years
All causes
B:
old age structure.
structure.
urban environments have a greater
who
It is
more polluted
incidence of noninfectious types of diseases than do
specific than to observe that those
live in
those living in cleaner rural environments.
Health effects as a result of exposure to certain inorganic and organic chemicals
known.
are not
This
is
particularly true in the case of long-term exposure to
centration of toxic and hazardous contaminants.
stricted to
in the
eral
more research
may
some value
be of
re-
high levels of specific pollutants
in setting
allowable limits of exposure.
will be required before the matter of "safe limits"
remainder of
In the
to relatively
Taking the results of these studies and extrapolating them to the gen-
workplace.
population
stood.
who have been exposed
workers
low con-
Epidemiological studies are usually
health are discussed.
organic or organic.
this chapter,
They are presented
Under each heading
15 of the
common
most
in alphabetical
marized from Kruss and Valerioto (1979).
is
However,
adequately under-
contaminants affecting
order and grouped as either in-
that follows, the available
knowledge
Tables 8-9 and 8-10 provide a
is
sum-
summary of
these contaminants, their sources, their occurrence in the environment, and their major
health effects.
8.5.1 Inorganic Contaminants
Arsenic
is
a by-product of
cobalt ores.
It
is
and accumulate
copper and lead smelting and the roasting of gold,
primarily an airborne pollutant, but
in
fish.
It
is
also a
it
silver,
and
can contaminate bodies of water
component of some
agricultural insecticides
and
294
Microbiology and Epidemiology
The main
fungicides.
health effect
is
symptom
arsenic poisoning of workers in the gold mining
who
industry and of agricultural workers
Chapter 8
One
handle materials containing arsenic.
paralysis of the lower limbs, although acute poisoning includes gastric and
is
intestinal upsets.
It
is
considered to be a potential carcinogen contributing to occupa-
tionally related lung cancer
Asbestos
used for the production of asbestos-cement floor
is
and gaskets and the manufacture of fireproof linings and
mining of the mineral and the manufacture of
in the
effects, but
consumers are also regularly exposed
asbestos products in daily use.
and inhalation of these
niosis, or asbestosis,
heart to
ities
work
form of
due
to the great variety of
an airborne pollutant,
to asbestos,
in asbestos
garded as a carcinogen.
result of cardiac failure.
Lung cancer among people exposed
Asbestos
concern over the presence of fibers
can also be present
in
in air
is
Fatal-
generally re-
This has led to public
from products made with the mineral. Asbes-
water supplies
asbestos products are manufactured
if
nearby, and in processed beverages (soft drinks, beer, and wine)
removing impurities. There
is
to asbestos "dust" occurs
with a frequency more than twice that of the general population.
are used, for
pneumoco-
In addition to forcing the
harder, scarring can complicate other existing respiratory diseases.
from asbestosis are often the
tos fibers
directly
fibers, asbestos is
a severe scarring of the lungs.
is
brake linings,
tiles,
Those working
products suffer the most adverse
over an extended period can result
fibers
which
In the
its
textile.
is
no evidence
when
asbestos
filters
that ingestion of asbestos fibers
harmful to humans.
Cadmium,
a metal toxic to most species,
released into the environment from
is
industries (electroplaters, battery producers, etc.) in sufficient quantities to warrant
classification as a pollutant.
found
in
values.
As
a result of these industrial effluents,
municipal sewage sludges
The most
at
it
is
its
commonly
concentrations higher than normal background
significant health effects are
found
in
workers subjected to cadmium
fumes. Exposure to the fumes, which are suspected to be carcinogenic, can result in degeneration of the joints.
croorganisms to humans.
Cadmium is taken up at all levels of the food chain, from miHuman consumption of leafy vegetables, fish, shellfish, and
method by which cadmium enters the body. Japan recorded
cadmium poisoning between 1962 and 1977 as a result of people eatfood contaminated with cadmium. The source of the metal was traced to runoff
drinking water
is
the usual
over 230 cases of
ing
from mine
tailings.
Lead may be
present in the food and water
we consume and
in the air
Until the advent of unleaded fuel the combustion of leaded gasoline
source of lead pollution in the atmosphere and
is
was
we
breathe.
the largest
discussed further in Chapter 13.
Raw
water supplies can be contaminated by lead from the discharge of sewage treatment
plants and
from agricultural
runoff.
Water distribution systems may also contain high
concentrations of lead due to the use of lead joints in water mains and lead pipes for
water lines inside buildings, which were
common
at
one time. The problem
is
more
se-
vere with soft water, which has a greater tendency to dissolve lead than hard water does.
Although most ingested lead
accumulates slowly
in the
excreted and
is
ache and physical weakness.
60%
of inhaled lead
is
exhaled, lead
still
The initial symptoms of lead poisoning are stomach
The final stages may lead to a collapse of the central
body.
295
Noninfectious Diseases
Sec. 8.5
Lead poisoning appears
nervous system.
to be
most prevalent
to their greater capacity to absorb lead and their tendency,
and
cribs
toys, that
may have been
due
in children,
at
partially
chew on
was prohib-
early ages, to
painted with a lead-base paint before
it
ited for this use.
in
Mercury poisoning was mentioned
Inorganic mercury compounds
earlier in regard to the
ponents such as switches, and
common
com-
Organic mercury compounds are used as slimicides and fungi-
and sodium hydroxide.
most
disaster
industry for the production of chlorine
in the chlor-alkali
Poisoning by methyl mercury
cides in the pulp and paper industry and in agriculture.
(the
Minimata Bay
are used in the production of electrical
Japan.
organic compound)
is
characterized by numbness, speech impair-
ment, and loss of motor coordination, progressing to paralysis, deformity, coma, and
Poisoning by inorganic mercury (particularly vapors) results
death.
central nervous system
Exposure
and possibly psychotic disorders.
either through the food chain or in the workplace.
A
is still
to the
mercury can be
steady diet of seafood from a mer-
Mercury released
cury-contaminated source poses a substantial risk to the consumer.
past decades
damage
in
to
in
present in bottom sediments of lakes and rivers and will continue to
be a source of pollution for the forseeable future.
Nitrates and nitrites derived from the excessive use of fertilizers can result
significant nitrate pollution of surface water
feed
lots,
and poultry operations also has a high
pable of reducing nitrates to nitrites
human
threats to
taining Fe +:
oxygen
),
in the
disease,
is
to
health from nitrites.
bloodstream.
This
tunately, a suitable
number of
in
New
nied by
known
can oxidize the hemoglobin (con-
as
Second,
is
Under
days),
1952 and
in
can combine with various amines
SO :
emitted primarily from the burning of coal and
.
can build up to deadly concentrations.
Belgium's Meuse Valley
be carci-
in
oil
having a high
masses
for
This happened in Lon-
Similar incidents have occurred
1930.
S0 2
High concentrations of
,
when accompaThose affected are
especially
particles, result in irritation of the respiratory system.
in
Unfor-
has not been found.
the right atmospheric conditions (resulting in static air
The contribution of S0 2
Chapter 5 and
is
described in detail
13.
Particulate matter with a specific size of about
particles) can penetrate deeply into the lungs
amount of foreign material
in
harder the heart has to work.
heart
to
growth and prevent botulism.
nitrites
mainly elderly people with chronic respiratory problems.
Chapter
incapable of transporting
the use of nitrites in cured meats (bacon,
etc.) to retard bacterial
York and Pennsylvania.
smoke
nitrites
emissions to the acid rain problem was discussed
in
is
methemoglobinemia or blue baby
form nitrosamines, many of which are known
chemical replacement for
Sulfur dioxide
sulfur content.
in
illness,
Concern has been expressed about
prepared meats, hot dogs,
don
First, nitrites
especially harmful to infants since they are particularly susceptible to asy-
in the gastrointestinal tract to
a
nitrate
the digestive
methemoglobin (containing Fe +3 ), which
phyxiation by methemoglobinemia.
nogenic.
in
in
Manure from livestock,
content. The human body is casystem. There are two distinct
and groundwater.
0.
1
urn (the
and be deposited
the lungs, the less efficient
is
This buildup of particulates
size of cigarette
there.
The
smoke
greater the
the respiration system and the
is
believed to lead to chronic
and respiratory ailments such as emphysema and bronchitis. To make matters worse,
296
TABLE
8-9
Microbiology and Epidemiology
COMMON
Chapter 8
INORGANIC CONTAMINANTS CAUSING NONINFECTIOUS DISEASES
Sphere most
Inorganic
Major source
contaminant
Ore smelting,
Arsenic
Primary health effects
affected
refining
Air,
water
Arsenic poisoning (gastrointestinal
Pesticides
Asbestos
disorders, lower-limb paralysis)
Heat-flame-resistant appli-
Air
Asbestosis (scarring of lungs)
Carcinogen
cations
Cadmium
Cadmium
Air, food.
Electroplaters, battery
manufacturers
fumes, joint pain, lung,
kidney disease
water
Possibly carcinogenic, teratogenic
Leaded gasoline,
Lead
batteries
Solder, radiation shielding
Impairs nervous system, red blood
Air, food.
water
cells synthesis
Depends on exposure
Mercury
Inorganic form
Electrical
Water, food
goods
Inorganic: disorders of central
nervous system, possible
psychoses
Chlor-alkali industry
Organic form
Organic: numbness, impaired speech,
Slimicides
paralysis, deformity, death
Fungicides
Nitrates
.
Food, water
Agricultural runoff
Nitrites
Meat preservatives
Sulfur
Combustion of
N0 reduced to N0 (in body)
N0 + amines —> nitrosamines
N0 + Fe +2 -> methemoglobinemia
3
2
2
2
dioxide
sulfur
Irritation
Aii-
of respiratory system
Precursor of acid rain, which
containing fuels
is
widely destructive
Particulates
Smoke from combustion
Can
Air
lead to cardiac, respiratory
aliments (emphysema, bronchitis)
Dust, pollens, etc.
Health effects more noticeable
if
particulates are in combination
with other pollutants
(e.g.,
S02
the synergistic effects of particles and gaseous pollutants, such as the combination of
and smoke
particles, are greater than the
sum
)
S0
2
of their individual effects.
8.5.2 Organic Contaminants
Numerous manufactured organic chemicals are considered to be a potential threat to the
many species, including humans. Of these, DDT, fenitrothion, and Mirex
health of
were developed
as pesticides.
Others, such as
PCBs
(polychlorinated biphenyls), were
developed for quite benign uses, such as cooling agents
through accidental release find their
way
in electrical
into the environment.
transformers, but
The epidemiological
ev-
idence against these chemicals varies, but considering that they are poisonous and have
Sec. 8.5
had some link
DDT
Anopheles mosquito freed
been used widely throughout the
has
U/ichloroc/iphenylrrichloroethane)
trolling the
(WHO)
estimates that
and persistent chemical
that
remains
in the
species, including
ranges from about
DDT
where
ppm
1
in
humans.
Symptoms
abnormal decreases
in
oils.
DDT,
It
bioaccumulates
It
DDT
little
a very stable
is
relatively insol-
is
in the fatty tissue
DDT
use to as high as 27
in
humans
ppm
in India,
Health risks exist as result of exposure either to
of
DDT
poisoning include nervous disorders and
white blood cell counts.
fatalities directly attributable to
DDT
The average concentration of
countries with
has been used extensively.
spraying or by ingestion.
risk of malaria in the
However,
environment for years.
uble in water but readily soluble in fats and
many
effectiveness in con-
its
from the
billion people
1
1950s and 1960s, thereby preventing millions of deaths.
of
being unwit-
at
not unfounded.
is
The World Health Organization
world.
alarm
to cancer or other degenerative diseases, public
exposed
tingly
297
Noninfectious Diseases
but there
There have been no reports of human
is
concern over the long-term effects of
low-level concentrations.
Dioxin, although
it
represents a family of chemicals,
one of the deadliest chemicals ever manufactured.
to
referred to as
impurity
TCDD,
or 2,
3, 7,
is
the
common name
(Technically,
it
is
applied
more properly
8-tetrachlorJibenzopara-Jioxin.) Dioxin occurs as an
manufacture of various chemicals and pesticides having a trichlorophe-
in the
Small amounts are also released to the atmosphere when plastics are burned;
nol base.
thus the concern
Among
the
when municipal solid wastes are incinerated.
more prominent of the contaminated products
are hexachlorophene, a
germicide used for acne control, cleansing of newborn infants, and disinfection
been banned as a nonprescription drug), and
herbicide,
now banned
50:50 ratio with
2,
in
4-D
2, 4, 5-T,
North America but used extensively
(creating the defoliant called
(it
has
or trichlorophenoxyacetic acid, a
in the
Agent Orange).
Vietnam war
Symptoms
in a
asso-
ciated with exposure include changes to most internal organs, chloracne, nervous disorders,
and death
if
exposed
Dioxin
to sufficiently high concentrations.
is
a confirmed
teratogen (causes birth defects) and a suspected carcinogen.
In Seveso, Italy, in 1976,
equipment
lb
failure resulted in the release of
The
chloracne.
the
between 2 and 10
permanent
ill
with
residents of the area are undergoing long-term monitoring to determine
effects, if any, of
In the past
short-term exposure to high concentrations of dioxin.
few years Niagara
leaking out of old chemical
dumps
Falls,
New
York, has
become infamous
for dioxin
into the Niagara River, creating potential pollution
of the water supply of 5 million North Americans.
is
of dioxin to the atmos-
Before evacuation of the town, many animals died and people became
phere.
Even
the spray
from Niagara Falls
a contributor to pollution, releasing volatile organics with small amounts of dioxins
atmosphere on a continuous basis (McLachlan. 19X7).
In 1983, Times Beach,
community of 2000. was declared by the U.S. Environmental Protection
Agency to be uninhabitable because of dioxin. The inhabitants were relocated at a cost
of more than $30 million. The source of the dioxin was traced to contaminated waste
into the
Missouri, a
oil
that
Mixed
had been used as a dust suppressant on local roads and private properties.
in
with the
hexachlorophene.
oil
were liquid wastes from a factory
that
had previously produced
298
Microbiology and Epidemiology
Chapter 8
Fenitrothion is an insecticide used in eastern Canada for the control of the spruce
budworm. It has a fairly rapid rate of decay in the environment and is of low toxicity
to mammals. It is the subject of much medical debate concerning its role in the initia-
syndrome, a disease causing convulsions, brain damage, and possibly
tion of Reye's
The cause of Reye's syndrome
death following recovery from a minor viral infection.
is
unknown, but
suspected by some researchers that the insecticide could be a con-
is
it
tributing factor.
Mirex, another manufactured chlorinated hydrocarbon, has been found
concentrations in bodies of water, various fish species, and aquatic birds.
developed as an insecticide
low
United States) and
(to control fire ants in the southern
also used as a fire retardant in plastics and for generating
at
Mirex was
smoke
is
in military exercises.
Although there have been no documented cases of Mirex poisoning
in
humans, there
is
concern regarding the health of persons whose diet includes large amounts of Mirex-
contaminated
fish
mammals, and
PCBs
broken down
its
Mirex
and other seafood.
algae to
(polychlorinated biphenyls) are chemically inert, soluble in water, and not
normal temperatures. As a
at
result,
PCBs have
a
number of
industrial uses
Their high stability makes them persistent
draulic and heat transfer applications).
environment. They are related to
and
to cause cancer in rats,
it is
DDT but
cancer in humans.
It is
An
viral disturbances.
fires,
but there
is
no evidence
epidemic of PCB-related effects was discovered
manufacturer. Although samples of the
the incident
tion is usually accidental,
and
was
its
oil
in
to link
PCBs
to
in
were found
to contain
use has been restricted
is
the
Kyushu, Japan,
the heating system of a rice-oil
2000
later traced to dioxins (Dennis, 1989).
Trihalomethanes, of which chloroform
in
in the
PCBs have been shown
stable.
the cause of skin disorders (such as chloracne), headaches, and
1968 and was originally attributed to a leak
PLB compound;
more
are even
feared that cancer could develop in workers exposed to
fumes from transformer
the liquid or to the
duced
many organisms, from
toxicity to nontarget species.
its
a dielectric fluid for industrial capacitors and transformers and as a fluid in hy-
(e.g., as
in
toxic to
is
use has been curtailed due to
in
many
most
3000 ppm of a
to
PCB
contamina-
countries.
common
example, are pro-
water and wastewater treatment plants when natural organic compounds com-
bine with chlorine added for disinfection purposes.
anaesthetic for
many
low concentrations
tions of chloroform
pend on the
now being
total
its
years, but
it
is
now
Chloroform has been used
carcinogenic effects have not been established.
found
in chlorinated
as an
suspected of being carcinogenic, although
at
The concentra-
water supplies are normally very low and de-
organic content of the water being treated.
Considerable research
is
carried out on the significance and control of trihalomethanes.
8.5.3 Safe Limits
Ideally,
we would
like to set "safe" limits
on the concentrations of
ganic contaminants that can cause noninfectious diseases.
thing as a safe level, only an acceptable level of risk.
cases impossible to determine.
be
it
in the air, soil, water,
Even
There
all
is,
inorganic and or-
of course, no such
this is difficult
and
in
some
Establishing guidelines for contaminant concentration,
or food,
is
a challenge for researchers, engineers,
and admin-
)
Chapter 8
299
Problems
COMMON ORGANIC CONTAMINANTS CAUSING
TABLE 8-10
NONINFECTIOUS DISEASES
Sphere most
Organic
Major
contaminant
DDT
Primary health effects
affected
source-
Application of pesticide throughout world
Water, food
Bioaccumulates
chain
Results in nervous disorders
in fatty tissues
Decreased white blood
Persists in
Impurity of manufacture of
Dioxin
trichlorophenols used in various
(specifically
TCDD)
Water, food
chain
Extremely toxic
in
concentrated
form, damage to kidney, liver
and nervous system
biocides
Powerful teratogen
Released by application or acci-
Possibly carcinogenic
dent
Insecticide spray on cultivated
Fenitrothum
count
cell
environment
Water, air
Only
toxic to
mammals
at
high
dosages
crops, forested land
May
be partly responsible for
tiating
Reye's syndrome
ini-
in
children
Mirex
Insecticides, fire retardant in plas-
Water, food
chain
tics
Biologically active, persistent
Toxicity varies with species
Bioaccumulates
PCB
Dielectric, heat transfer
and hy-
Food chain
in
food chain
Persistent in environment
Probably carcinogenic, exposure
draulic fluid
results in chloracne, headaches,
visual disturbances
Chloroform
Previously used as anaesthetic
Presently in
Food, water
consumer goods.
in
high concentra-
tions
pharmaceuticals, pesticides
May
Acutely toxic
Liver, heart
be produced during chlonna-
damage
Carcinogenic to rodents
tion of water supplies
Accidentally produced
Trihalomethanes
in
water as
(includes
a result of certain organics (hu-
chloroform
mic
Water
Possibly carcinogenic
acids, etc.) and chlorination
The epidemiology of many noninfectious diseases is extremely complex.
compounds discussed previously may be intensior diminished by the presence of other chemicals. Due to the complexity and the
istrators alike.
The
fied
health effects of the elements or
innumerable unanswered questions concerning the effects of these contaminants, regulators
must
err
minimize the
on the side of caution and
risk to
set limits as
low as
is
reasonably possible, to
which the general public and the environment
are exposed.
PROBLEMS
8.1.
Describe and compare the nutritional requirements of autotrophic and heterotrophic bacteria.
8.2.
Draw
a typical bacterial cell
and describe the major components and
their functions.
300
8.3.
Chapter 8
Microbiology and Epidemiology
Draw
(a)
the growth-death curve for a bacterial culture.
Label the axes and
all
phases of
the curve, and briefly explain the diagram.
What comparisons can be made between the growth-death curve of
ture and a graph showing world human population growth? Can we
(b)
from
8.4.
A
comparison?
this
batch culture of 100 unicellular bacteria has grown from a single bacterium in 2 h
Assuming continued exponential growth, how many
through exponential growth.
will the culture
8.5.
Why
8.6.
What
What
8.7.
the bacterial cul-
learn any lessons
have after
are viruses difficult to
bacteria
additional hour?
1
remove from a water supply?
between algae, fungi, and bacteria?
are the basic differences
the rationale for studying domestic water supply
is
and treatment concurrently with
wastewater treatment and disposal?
8.8. Cite
and describe another example of cooperative behavior between microorganisms similar
to the cases
8.9.
Why
is
noted
filtration
in
Section 8.3.2.
of water without chlorination partially effective
in controlling
pathogenic
bacteria?
8.10. Outline
two methods by which
the spread of schistosomiasis in rural Africa might be con-
trolled.
8.11.
Compare the relative contributions of a treated water supply and the collection and treatment of human wastes toward the control of epidemic diseases in developing countries. If
there are insufficient resources for both systems, should one be given priority over the
other? Explain.
8.12.
What
are the factors affecting the virulence of a particular disease?
8.13. During an epidemic of a contagious disease,
8.14.
Name
8.15.
Are you more
Name
8.17.
What
What
8.18.
Why
8.20.
What
doesn't everybody get infected?
details of
by drinking water from a polluted stream
in the
winter or
your reasoning.
three waterborne diseases, and note their
symptoms and
causative organisms.
are the requirements for an organism to be an indicator organism?
are coliforms?
the results
8.19.
likely to get sick
summer? Give
in the
8.16.
why
four of the mechanisms of transfer of disease between humans.
are
Why
Why
are
between airborne infectious diseases and diseases caused by
air
is
from the coliform
you
Escherichia coli considered an indicator of pollution?
test
considered to be presumptive?
less likely to contact
are the differences
an airborne infection outdoors than indoors?
pollution?
8.21.
Name two
8.22.
How
airborne infections, their symptoms, and their causative organisms.
does an outbreak of bubonic plague occur?
spread?
How
can
it
How
does the outbreak continue to
be controlled?
8.23. Describe the necessary conditions under
which an insect-borne disease becomes an
epi-
demic.
8.24.
What methods
are there for controlling insect-borne diseases?
8.25. Should the use of the insecticide
DDT
be stopped completely? Give reasons for your an-
swer.
8.26.
Why
is
there so
much concern and
controversy about the amounts of dioxin, Mirex, and
other synthetic organic chemicals found in water supplies?
8.27.
8.28.
How do you account for the increase
America over the past century?
A
in deaths
due
to noninfectious diseases in
North
resurgence of tuberculosis and other infectious diseases (cholera, malaria, etc.) once
thought to be under control,
is
occurring
in the
world.
Government complacency,
ineffec-
Chapter 8
301
References
tive antibiotics, deforestation,
factors have
been blamed.
all
new mutant microbial strains, unsanitary conditions and other
Examine one of these diseases in a location where an out-
break has occurred, noting the causative agent, the reason(s) for the epidemic, and your rec-
ommendations
as to
what might be done and by whom.
8.29. Cryptosporidiosis and other previously unheard of diseases [e.g.. hemolytic uremic syn-
drome (HUS) and acquired immune deficiency syndrome (AIDS)] are occurring in epidemic proportions. Select a location where one of the newer diseases is prevalent, note the
pathogen responsible, the symptoms of the disease, and the vectors involved, and suggest
possible solutions.
8.30.
Mercury
one of the most toxic heavy metals causing noninfectious disease; small doses
is
impair the nervous system and kidneys, large doses cause
been a major problem
coma and
supposedly pristine waters such as lakes
in
in
death.
Mercury has
northern Ontario, Can-
ada, the Everglades in Florida, the water supply for Boston. Massachusetts, and lakes in the
northeastern United States, where
the water to
tion
ppm
in fish
due
to
its
concentration can increase a million-fold, from ppt
bioaccumulation.
Select an area
in
where mercury contamina-
a problem and suggest what natural and/or industrial sources might be contributing
is
problem.
to this
REFERENCES
APHA. AWWA.
and
WPCF. Standard Methods
for the Examination of Water and Wastewater,
16th ed. Washington, D.C.: (American Public Health Association,
American Water Works
Association and Water Pollution Control Federation), 1985.
Baker, M. N. The Quest for Pure Water.
Vol.
New
1.
York: American Water
Works Association,
1948.
BUCKMAN, O.
and Brady. N. C. The Nature and Properties of Soils, 6th ed.
H..
New
York:
Mac-
millan. 1960.
Clark.
W.. Vii.ssman. W., and
J.
New
Commoner.
Dennis.
p.
Hammer, M.
J.
Water Supply and Pollution Control, 3rd ed.
York: IEP, 1977.
B.
The Closing
"How Dangerous
P.
Circle.
are
New
York: Alfred A. Knopf, 1971;
PCBs— Realh
?"
New
York: Bantam, 1972.
The Globe and Mail. Toronto, October
4,
1989.
W.W. Norton,
1982.
A7.
ECKHOLM.
E.
P.
Eckhoi.m. E.
P.
Down
to Earth:
Environment and
Human
Needs.
New
York:
The Picture of Health: Environmental Sauries of Disease.
New
York:
W.W. Nor-
ton. 1977.
Feachem,
R. G.,
Bradley, D.
J.,
GARELICK, H., and Mara, D. D. Sanitation and Disease: Health
Aspects of Excreta and Wastewater Management. Washington. D.C.: published for the
World Bank by Wiley, 1983.
Gaudy, A.
New
F.. Jr..
and Gaudy, E. T. Microbiology for Environmental Scientists ami Engineers.
York: McGraw-Hill. 1980.
Gooderham, M. "By Filter or Faucet We Aren't Safe from Water-Borne Bugs. The Globe and
Mad. Toronto. October 9. 1993. p. D8.
Kki
i
s.
P.,
1989
and VALERIOTO,
1.
M. Controversial Chemicals. Montreal: Multiscience Publication,
302
Microbiology and Epidemiology
Lechevallier, M. W., Trok,
fate
T.
M., Burns,
M.
O.,
Chapter 8
and Lee, R. G. "Comparison of the Zinc Sul-
and Immunofluorescence Techniques for Detecting Giardia and Cryptosporidium
in
Water." Journal of the American Water Works Association, 82 (1990): 75.
McLachlan, M.
S.
"A Model of
thesis, University
the Fate of Organic Chemicals in the Niagara River."
M.A.Sc.
of Toronto, 1987.
Mitchell, R. Introduction
to
Environmental Microbiology. Englewood
Cliffs, N.J.: Prentice Hall,
1974.
Okun, D. A. "More on Cryptosporidium:'
AWWA,
An
Opflow, 19(10), October (1993): 1-12.
Manual on the Identification, Significance
and Control of Algae in Water Supplies. Public Health Service Publication 657. Washington. D.C: U.S. Department of Health, Education and Welfare, 1959.
Palmer, C. M. Algae
in
Water Supplies:
Parmelee, M. A. "Milwaukee Takes Steps
(1993):
Pelczar, M.
to
Ensure Water Quality."
AWWA, Mam
Stream, 37(5)
1.
J., Jr.,
Reid, R. D., and
Chan,
E. C. S. Microbiology, 4th ed.
New
York:
McGraw-
1977.
Hill,
Perkins, H. C. Air Pollution.
Sartwell,
Illustrated
P. E.(ed.)
New
York: McGraw-Hill, 1974.
Maxy-Rosenau Preventive Medicine and Public Health,
10th ed.
New
York:
Appleton-Century-Crofts, 1973.
U.N. The Determinants and Consequences of Population Trends.
New
York: United Nations,
1973.
Winslow, C.
E.
The Conquest of Epidemic Disease. Princeton,
1943.
Ziegler,
P.
The Black Death. London: Penguin Books, 1969.
N.J.: Princeton University Press,
CHAPTER
9
Ecology
Thomas
9.1
C.
Hutchinson
INTRODUCTORY CONCEPTS
The term ecology is derived from the Greek oikos, meaning house, combined with logy,
meaning "the study of. Thus, literally, ecology is the study of the earth's households.
For our use, ecology can be defined as the study of the relationship between organisms
and
their
ical
environment of
environment.
Here, environment
air, soil,
range of ecological studies
is
taken to
mean both
and water, and also the biological environment
is
very broad.
is
the
restricted, a study of the re-
and the changes occurring
in a lake or river
when
untreated
added.
The abiotic
semblages of
(nonliving), physical-chemical environment and the biotic (living), as-
plants, animals,
tems or ecosystems.
of,
is
between the number of eggs a song bird lays and the amount of food availa-
ble for the chicks to eat,
sewage
chemThe
itself.
Examples include an investigation of
chemistry of the soils to which a particular plant species
lationship
the physical and
or a few, species.
and microbes together form interdependent ecological sys-
Ecosystems can be large or small, containing a very large number
They
are frequently defined
and have a certain recognizable unity of
their
own.
their dominant vegetation types
Examples of ecosystems that oc-
by
cupy
large parts of the earth's surface are the tropical rain forests, boreal coniferous for-
ests,
deciduous or hardwood
forests, tundra
and Alpine ecosystems,
prairie grasslands.
303
304
Chapter 9
Ecology
swamps and marshes, lakes, marine continental
The boundaries around a defined ecosystem are generally very
cactus deserts, salt marshes, coral reefs,
shelf,
and open ocean.
unclear,
and substantial heterogeneity can
ecosystems as those
exist in such large-scale
A
Small ecosystems can also exist within a much larger major type.
just listed.
small
pond on top of a mountain within a predominantly alpine terrain would be such an example. Within each ecosystem there is a dependence of one species on other species.
Ecosystems are also controlled by, and a consequence of, climate.
The two overriding factors that keep the ecosystem together and functioning as an interdependent whole are the need for nutrients and the need for energy. While the nutrients
within an ecosystem are continuously cycled and recycled through all of its components
with quite limited losses from and inputs into the system, the energy of the incoming solar
from the sun,
radiation derived
Ecology
is
passed through the system largely unidirectionally.
among
the study of the interrelationships
is
and animals and
plants
the interactions between living organisms and their physical environment.
An ecosystem
is
a group
of plants or animals,
together with that part of the
physical environment with which they interact.
be nearly self-contained, so
compared to the quantities that are
exchange of the essentials of life.
small
Biota are
9.2
all
ENERGY FLOW
An ecosystem
which flows
that the matter
defined to
is
and out
into
internally recycled in
of
it
is
a continuous
the living elements of an ecosystem or a given area.
IN
ECOSYSTEMS
This section draws heavily on the account given by E.
J.
Kormondy
in
Chapter 2 of his
book Concepts of Ecology (1969). All biological activity is dependent on green plants
successfully utilizing energy that comes originally from the sun. In this process the radiant energy of the sun
energy (heat)
is
in cellular
transformed
first
to
chemical energy and then to mechanical
metabolism.
The sun can be considered
to
be a continuously exploding hydrogen bomb, with a
temperature and composition such that hydrogen
itant
release of considerable energy
extend from shortwave
total
energy
is
x— and gamma
in the region
About
trum (0.38
and
such a small target
is
50%
and
it
in the solar
does so
at
rays to
is in
(i.e.,
99%
of the
the region from
the region of the visible spec-
Because the earth
system, only about one fifty-millionth of the sun's
the earth's outer atmosphere (190
a constant rate.
This constant rate
amount of
cross a unit area or surface per unit of time.
s,
While these
longwave radio waves, about
of this energy
flux or solar constant, defined as the
mately 1.4 kJ/m 2
transmuted to helium, with concom-
partially utilized in photosynthesis.
mendous energy output reaches
surface),
is
form of electromagnetic waves.
of wavelengths from 0.2 to 4.0 urn
ultraviolet to infrared).
to 0.77 u,m)
in the
for a total energy
is
km
income of
5.5
is
tre-
above the earth's
referred to as the solar
radiant energy of
This value
is
all
wavelengths that
estimated to be approxi-
x 10 21 kJ
(1.5
x 10
18
kWh)
(see
)
Energy Flow
Sec. 9.2
in
305
Ecosystems
45.000 -
5.000
Feb
Jan
Figure 9-1
Mar
Apr
May
Aug
July
Sept
Nov
Oct
Dec
Daily totals of solar radiation received on a horizontal surface for different geographical
latitudes at different times of the year
Source:
June
and based on a solar constant value of 81.2 kJ/m 2
•
min.
Gates (1962).
Note: Original figure
in
Conversion by author.
also Section 7.3).
cal/cm 2
units of g
(1
g
cal
=
4.1855
Because of the
yr
J;
based on solar constant value
1
=
J
1
W
elliptical orbit
any given location varies seasonally with
of 1.94 g
cal/cm 2
yr.
s.)
of the earth around the sun, the flux
latitude.
Because of the earth's
at
rotation, the
flux at a given place also varies diurnally (Figure 9-1).
The process by which chlorophyll-bearing
vert carbon dioxide
and water
to sugars
is
plants use energy
called photosynthesis.
from the sun
to con-
The generalized equa-
tion of photosynthesis is
chlorophyll
6CO + 12H 2
:
+
2800
>
kJ
C 6 H 12
6
+ 6C0 2 + 6H 2
(9.
1
Photosynthetic activity and rates of carbon dioxide fixation into plant carbohydrates can
be estimated
in a
number of ways, including
rates of
C0 2
removal and
rates of
2
pro-
duction as well as rates of accumulation of photosynthetic intermediate compounds.
Ecological terms used to explain these activities are defined on page 306.
9.2.1 Estimates of Primary Production
The term primary producer (engaging
any autotrophic organism
sun.
that
is
in
primary production)
is
used to designate
capable of directly utilizing the radiant energy of the
This includes organisms capable of photosynthesis.
Transeau (1926) calculated
306
Chapter 9
Ecology
An autotroph' is an organism that obtains its cell carbon from an inorganic
source (C0 2 HC0 3 and its energy from the sun (actually, a photoautotroph
)
,
as
distinct
from a chemoautotroph, which gets
of inorganic
energy from the oxidation
its
chemical compounds).
A heterotroph*
an organism that obtains both
is
its
cell
carbon and
its
en-
ergy from organic matter.
A chemotroph*
is
an organism
that obtains
its
energy from the oxidation
of
FeS and H2S, and its cell carbon from
Chemotrophs are relatively insignificant in
simple inorganic compounds, such as
inorganic and/or organic matter.
the energy relations of an ecosystem, but play a significant role
ment
of mineral nutrients in the
The food chain
tem.
ers,
is
the move-
an idealized pattern
of flow of
energy
in
a natural ecosys-
the classical food chain, plants are eaten only by primary consum-
In
primary consumers are eaten only by secondary consumers, and so on.
The food web is the actual pattern of food consumption in a
tem. A given organism may obtain nourishment from many
natural ecosysdifferent trophic
thus giving rise to a complex, interwoven series of energy transfers.
levels,
Productivity
is
in
ecosystem.
energy
is
the rate of fixation of energy into tissue.
by plants; secondary productivity
fixation
is
at
Primary productivity
higher trophic levels.
Trophic levels are levels of nourishment. A plant that obtains its energy directly from the sun occupies the first trophic level (autotroph). An organism
that consumes the tissue of an autotroph occupies the second trophic level
(herbivore), and an organism which eats the organism that had eaten autotrophs occupies the third trophic level (carnivore).
Transpiration
is
the controlled evaporation of water vapor from the surface of
leaf tissues.
'
In
ecology the energy source
whereas
isms,
is
the main basis for the differentiation of organ-
microbiology (see Section 8.2.3) the carbon source
in
is
usually
empha-
sized.
primary production
a
in
midwestern U.S. cornfield based on an estimated harvest of
10,000 plants per 0.405 ha, together weighing 6000 kg, and on chemical analysis of this
material.
He
calculated that the corn plants contained
had entered as
But
C0 2
in addition, the
maintain themselves.
through photosynthesis.
the plants
all
of which
in respiration to
to give a total or
Therefore,
in plants is that
this as
One kilogram
138.1
of glucose requires an energy input of
x 10 6 kJ has been
in
utilized in gross production, of
metabolic-respiratory activities.
Another energy
of transpiration, biologically controlled evaporation from
by which water and nutrients are taken up from
the plants to the leaves.
that
2674 kg of carbon,
equivalent to 6687 kg of glucose.
2045 kg of glucose,
Transeau estimated
which 32.2 x 10 6 kJ has been used
requirement
is
corn plants had to have used up some glucose
gross production of 8732 kg.
15.7 x 10 3 kJ.
This
The water
is
the soil
and moved through
then evaporated through small pores of the leaves
can be opened or closed so as to control water
loss.
It
is
perhaps surprising to
)
Energy Flow
Sec. 9.2
307
Ecosystems
in
TABLE 9-1 ENERGY BUDGET OF AN ACRE OF CORN
DURING ONE GROWING SEASON OF 100 DAYS
(0
405 HECTARE)
Glucose
Kilojoules
Solar energy
(kg)
(millions)
utilized
—
8550
6687
105.9
1.2
2045
32 2
0.4
8732
138.1
1.6
—
—
3808
44.5
4604
53.9
Incident solar radiation
(%)
1000
Biological utilization:
(W)
Net production
Respiration
(/?
Gross production (CP)
CP = (NP +
Energy
utilized in transpiration
Energy not
utilized
Transeau
Source:
R)
(
1926).
learn that the efficiency of energy utilization
that
is,
only 1.6% of the
total
is
only 1.6% (Table 9-1);
is
incorporated into carbohydrate through
Mathematically.
photosynthesis.
gross production
138 x 10* kJ
=
=
8.55 x 10 y kJ
solar radiation
Most
by the cornfield
energy available
natural ecosystems operate with an overall efficiency
between
0.1 to
2%
in
3%. Open
closer to the 0.1%
nature, while the very best agricultural system can achieve values as high as
ocean systems, which cover the majority of the earth's surface, are
conversion
rate,
although recent information suggests that ocean productivity
may have
been considerably underestimated.
Another interesting factor
energy conversion
in
autotrophs use the energy that they have incorporated.
is
the efficiency with
This utilization
is
which the
really the dif-
ference between gross production and net production expressed as a percentage.
Transeau's example,
it
energy of respiration
x ]QQ
=
words, although only 1.6% of the
32.2 x 10* kJ
138.1 x 10 6 kJ
energy of gross production
In other
For
is
total
x {QQ
energy was utilized
in
= 23A%
carbohydrate pro-
duction, the corn plants are quite efficient in converting the captured energy to biomass
utilizing 76.6 percent of
In aquatic systems,
systems.
it
(105.9/138.1 x
energy capture
is
100%).
considerably less efficient than
Data for two freshwater lakes are given
in
Table 9-2.
in terrestrial
Juday (1940) found
only 0.36% of the solar flux for Lake Mendota. Wisconsin, was incorporated
production
at the
autotroph level.
the phytoplankton, while less than
mud
at the
The
in
that
gross
Over 90% of this incorporated energy was used by
10% was used by the plants growing attached to the
bottom of the pond.
acidic
Cedar Bog Lake
in
Minnesota, with
only one-fourth as efficient as Lake Mendota, because
its
its
brown humic-stained waters, is
colored waters do not transmit
308
Ecology
Chapter 9
9-2 ANNUAL ENERGY BUDGET OF LAKE MENDOTA,
WISCONSIN, AND CEDAR BOG LAKE, MINNESOTA
TABLE
Solar energy
kJ/m 2
yr
utilized
4,975,390
100.0
•
(%)
Lake Mendota, Wisconsin
Incident solar radiation
Plant utilization
Phytoplankton
Net production (NP)
Respiration
12,515
4,185
(/?)
Gross production (GP)
16,700
Bottom-living plants
Net production (NP)
920
Respiration
290
(/?)
Gross production (GP)
1,210
Gross production by autotrophs
17,910
0.36
Cedar Bog Lake, Minnesota
4,975,390
Incident solar radiation
100.0
Plant utilization
Net production (NP)
Respiration
3,690
970
(/?)
Gross production (GP)
Source:
light as well as
due
to grazing
of 0.10%.
Lake Mendota: Juday (1940); Cedar Bog Lake: Lindeman (1942).
do the clearer Lake Mendota waters. Gross production, including losses
and decomposition, was found by Lindeman (1942) to be
Respiratory maintenance used
ergy capture
0.10
4,660
is in
large
measure due
21%
at
an efficiency
in
primary en-
to the decrease in light penetration in
water to the
of
this.
This difference
Since light is measured at the water surface,
at which the plants are growing.
0.10% (Cedar Bog Lake) is the overall photosynthetic energy conversion efficiency. If
measurement of radiation were taken at plant depths in the water, the efficiency would
rise to about
and 3%, respectively, for the two examples in the table. These are closer
depth
1
to the values of the terrestrial systems.
9.2.2 Comparison of Primary Productivity
in Different
World Ecosystems
Typical productivity values in different world ecosystems are given in Table 9-3.
production
is
controlled by a
number of
factors,
Gross
such as respiration and nutrient supply
(mainly nitrogen and phosphorus), and a number of key climatic variables, notably light
supply, length of growing season, temperature, and water supply.
constraints
emerge out of a consideration of Table 9-3.
It
is
Some
of these major
useful to have a rather
Energy Flow
Sec. 9.2
TABLE
309
Ecosystems
in
PRIMARY PRODUCTION OF THE EARTH
9-3
Net primary
Net primary productivity
normal range
Area
Ecosystem type
knri
10'
i
g/m :
(dry
•
production
Mean
yr|
(l()
9
dry tons/yr)
Tropical rain forest
24.5
1000-3500
2000
49.4
Temperate
12.0
600-2500
400-2000
1250
14.9
800
9.6
700
6.0
900
600
13.5
140
1.1
forest
12.0
Boreal forest
Desert and semidesert
42.0
250-1200
200-2000
200-1500
10-400
0-250
Cultivated land
14.0
100-3500
2.0
800-3500
100-1500
Woodland and shrub land
8.5
Savanna
15.0
Temperate grassland
9.0
Tundra and alpine
s.o
Swamp
and marsh
Lake and stream
2.0
Total continental
149.0
Open ocean
332.0
Algal beds, reefs, estuaries
40
1.7
650
2000
9.1
250
0.5
773
115.2
2-400
200-1000
500-4000
27.0
Continental shelf, upvvelling
2.0
5.4
4.0
125
41.5
360
9.8
1800
3.7
Total marine
361.0
152
55.0
World
510.0
333
170.2
total
Sonne: Westlake
(
l
lJ63).
as modified
and expanded from Whittaker (1961).
careful look at this table, as
it
tells
us a great deal about world food production potential
From
and the major differences among ecosystems.
system
in
terms of rate of annual production
the table, the
most productive eco-
the tropical rain forest.
is
Perhaps surpris-
swamps and marshes are equally productive on average, although the area they
occupy is much less. This high marsh productivity is due to their high nutrient status,
ingly,
while the high tropical rain forest productivity
growth (no seasonal dormancy), and high
is
nutrient
many
ing,
Clearing such forests
supply.
is
due
rainfalls.
is
to
high temperatures, continuous
The major
constraint in the tropics
fraught with dangers, as experienced in
parts of the world, since soil erosion in such high-rainfall areas can be devastat-
and much of the ecosystem's nutrient content
selves and
is
thus
removed with
Temperature
moving from
is
the
is,
in fact, in the forest trees
them-
the cut timber.
major constraint
in the
reduction in productivity per year in
tropical to temperate to arctic (tundra
and alpine) regions.
Light intensity
and length of growing season arc also involved. The effect of water supply can be seen
by comparing temperate grassland productivity (600 dry g/m 2
g/m 2
yr).
Higher productivity
tritional status
In
of these areas
looking
at
in
estuaries
(e.g., the deltas
(
1800 dry g/m 2
•
•
yr) with desert (40 dry
yr)
is
due
to the high nu-
of the Mississippi, Nile, and other rivers).
world net primary productivity, the key factors are the area of the
earth's surface occupied
by the different ecosystems and the net primary productivity
310
Chapter 9
Ecology
Enormous
per unit area.
Thus
productivity.
areas are occupied by deserts and semideserts, with their low
km 2
42 million
their
produce an annual
total
of only
1.7
x 10 9 dry
km of tropical rain forests yield approximately 49.4 x 10 9
World agriculture produces about 9.1 x 10 9 tons, much of this, of course, benonedible portions of crops and much of it being lost to diseases, to pests, in
2
tons, while the 24.5 million
dry tons.
ing in
The
storage, and in spoilage.
land yield
total
is
about 115 x 10 9 tons of dry matter per
year, while the oceans, with two-and-one-half times the surface, yield only
tons of dry matter per year.
huge untapped food supply for the world's predicted population growth.
unrestricted
krill,
most
In fact,
The Antarctic
is
an amazingly abundant crustacean, are being caught
in
and are
fisheries are already overexploited
presently an exception, but
55 x 10 9
thus unrealistic to consider the ocean as providing a
is
It
in
need of replenishment.
amounts by Japanese and Russian
trawlers, so the surplus there
may
not
last for long.
One
other point
is
worthy of note. Since oxygen
is
portions to carbon dioxide utilization in photosynthesis,
released in stoichiometric pro-
follows that the land, with
it
most twice the productivity of the oceans, produces about two times as much
the oceans.
A
high proportion of the oxygen from vegetation
Thus destruction of green
gions.
is
produced
as
2
al-
do
in tropical re-
plants in the oceans and in tropical land areas can be
expected to have long-term consequences on atmospheric oxygen
C0 2
levels, just as fossil
fuel burning
and forest destruction are causing a buildup of
Chapter
However, an as yet unknown amount of oxygen replenishment occurs as a
5).
result of iron oxide reduction
in the
atmosphere (see
by bacteria (Stumm and Morgan, 1981).
9.2.3 Energy Flow in Ecosystems
beyond Primary Producers
We
need to see how the
ducers in fact sustains
all
initial
conversion of incoming radiant energy by primary pro-
the organisms in the ecosystem, not just the green plants.
In
example of Cedar Bog Lake studied by Lindeman, gross production was 4660
kJ/m 2 yr, while 970 kJ/m 2 yr was consumed in the metabolic activities needed to
sustain the primary producers and to allow them to reproduce. Figure 9-2 indicates that
the
•
•
630 kJ/m 2 yr of the 4660 kJ/m 2 yr is consumed by the herbivores. This is 17% used
yr out of 440
by primary consumers of net autotroph production. Only 125 kJ/m 2
kJ/m 2
yr, or 28.4%, of this available herbivore energy is actually used by the carnivores. Although this is a more efficient utilization of resources than occurs at the au•
•
•
totroph-herbivore transfer level,
At the
level
it
still
leaves
of the carnivore, about
abolic activity, while the
60%
room
for greater exploitation.
of the energy intake
unconsumed remainder becomes
is
consumed
part of the sediment.
in
met-
Thus,
the percentage of available energy used for metabolic activity increases through the
trophic series, autotroph
28%
to
60%. This
herbivores have to
a
still
is
—»
herbivore -> carnivore,
typical of
move around
many food
in search
greater expenditure of energy
capture the herbivores.
is
chains.
at
One
Cedar Bog Lake from 17%
of the main reasons
is
to
that the
of the green plants on which they feed, while
needed by the carnivores as they search for and
311
Food Chain and Trophic Levels
Sec. 9.3
Incoming
Solar
Carnivore
Radiation
4.98 x 10
6
Autotroph
Herbivory
Herbivore
Carnivory
Gross
Gross Prod
4660
630
Gross Prod
630
125
Production
Figure 9-2
Fate of energy incorporated by carnivores in Cedar
per square meter per year.
Source:
9.3
4-
Bog Lake. Minnesota,
in kilojoules
Lindeman (1942).
cal/cm 2
Note: Conversion from original g
kJ/m 2
125
yr to
kj/m 2
yr by author,
(g
cal/cm 2
•
yr x
41.855
=
yr.)
FOOD CHAIN AND TROPHIC LEVELS
The sequence of consumption from the autotrophs through the carnivores represents the
sequence of the food chains, in which each link is dependent for its food (energy) supply on the immediately preceding link. These positions along food chains are called
trophic levels.
food that
To describe
levels.
tions, the
In
term food
and other characteristics
the network of various trophic levels,
web
is
movement
in
showing
their interconnec-
often used.
in the
ecosystem
is
one
gressively through the various trophic levels,
The
animals find
at several different trophic
considering the flow and utilization of energy in the food chain,
the energy
level.
Many
Often, the boundaries of the levels are not sharp.
suitable in size range
is
way, or unidirectional.
it
is
As
no longer available
it
it
is
clear that
moves
to the previous
relationships between the various trophic levels can be expressed as
Figure 9-3. These are
known
as productivity
pro-
shown
pyramids. Pyramids can also be used
to represent several of the other relationships in an
ecosystem
[e.g.,
biomass
(total or-
ganic matter) and numbers of organisms].
Because,
in general,
to maintain itself,
each carnivore has to consume large numbers of herbivores
and each of these herbivores has
omass per year of autotrophs
nature,
when
to
consume many times
to maintain itself, substances that are
they enter a food chain, are biomagnified
at
its
own
bi-
nonbiodegradable by
each succeeding trophic
level.
many of the well-known environmental problems of the past 20 to 30
years. The best known example is the biomagnification of organic pesticides such as
the chlorinated hydrocarbons, which include DDT (Table 9-4).
The concentration of
This has led to
312
Ecology
0.1
«
0.1
I
II
1.2
[
Second Carnivore
0.66
100
1.25
1.5 x 10
First
26.8
17.7
7.2 x 10 10
A
B
C
Herbivore
mg/m 2 .day)
Biomass
Numbers
(Individuals/m 2 )
Community pyramids
Figure 9-3
Producer
(Dry g/m 2 )
Productivity
[Dry
an experimental
for
Carnivore
4
I
280
Chapter 9
Trophic Levels
pond.
Whittaker
Source:
(1961).
Productivity
was estimated from the rate of phosphorus uptake in a shallow pond of low
The fourth trophic level was estimated as a fraction of carnivores feeding
second and third levels. The widths of the steps for numbers of organisms are
nutrient content.
on both the
on a logarithmic
scale.
TABLE 9-4 EXAMPLES OF CONCENTRATION FACTORS DUE TO FOOD CHAIN ACCUMULATION OF POLLUTANTS OF VARIOUS KINDS 3
Concentration factors in biota for various levels of
Cadmium
level in
water (mg/L) h
cadmium
water (based on dry weight)
0.0025
0.01
:
in
0.010
0.05
Floating fern
2
,000
25.000
.000
31,000
Duckweed
20,000
155,000
140,000
48,000
42,000
50.000
27.000
17,000
7,000
—
7,000
7.000
4.000
2.600
16.600
6,000
22,000
22.000
6.000
19,000
800
2,000
400
1.000
600
600
2.600
700
10
36
11
25
1
3
1
Water hyacinth
Roots
Leaves
Zooplankton
Snails
Tissue
Shell
Fish
Sediment
Food chain accumulation of
DDT
Food chain
in
0.00005
Plankton
0.04
minnow
Pickerel (predatory fish)
Tern (feeds on small
fish
and animals)
Herring gull (scavenger)
Merganser (fish-eating du ck)
'Numbers shown
The
leftmost
Source:
Hunt and Bishoff (I960).
is
at
Lake
Concentration factor (C.F)
1
800
0.094
18,800
1.33
26,600
3.91
78.200
6.00
120,000
22.8
are concentration factors (C.Fs.)
column (headed "0.01")
a California
(ppm)
Water
Silverside
b
DDT
460,000
various levels of concentration of pollutants.
from one study, the other three from a second study.
Sec. 9.4
DDT
313
Nutrient Cycles
can be increased many thousand-fold
in
the fatty tissues of carnivores such as
owls, peregrine falcons, ospreys, pike, muskie, and bass, as well as in fish-eating birds
such as brown pelicans, loons, and gannets.
from agricultural
land,
from
additions to such bodies to
of
many
DDT
can enter bodies of water by drainage
aerial drift during spraying,
kill
gnats and mosquitoes.
and from deliberate insecticidal
tion, since
one
effect of
DDT
with calcium metabolism.
are easily broken.
number
Drastic declines in the
birds of prey that survive on aquatic life have resulted
(and chlorinated hydrocarbons
from
this
bioaccumula-
in general) is interference
This leads to the production of thin-walled eggshells, which
Other examples of adverse effects of food chain biomagnification
have come from the use of mercury as a fungal-killing seed dressing, which
is
then
picked up by grain-feeding birds, such as pheasants and grouse, and in a number of
in-
stances has accumulated to lethal levels.
Being
at
the ends of food chains
on which they depend, humans can also be
cipients of accumulations of toxic chemicals in the food they eat.
quality control are essential to safeguard our health and to avoid such situations.
example of a safeguarding action was the banning of fishing
One
Great Lakes and
in the
other lakes in the area in the early 1970s because of excessive mercury in the
9.4
re-
Food processing and
fish.
NUTRIENT CYCLES
The supply of
soil,
nutrients other than
C0 2
,
but also to a smaller extent from the
ply of
many
nutrients
is
to an
ecosystem comes principally from the
air, in
rain
and snow, and as
dust.
The sup-
quite limited because they are in short supply in the soil and in
way that they are either incorporated into
made available for plant uptake by the decomposition of
dead plant and animal remains. The pathways from sources to sinks and back to
sources, are termed elemental cycles, and they differ among the various elements. We
other sources.
Nutrients are cycled in such a
plants and animals, or else are
consider briefly the three most important nutrient cycles, those of carbon, nitrogen, and
phosphorus.
9.4.1 Carbon Cycle
Carbon
is required in large amounts as a basic building block for all organic matter.
The ultimate source of carbon for organic matter is carbon dioxide, converted to organic
matter in photosynthesis. In nature, the movement of carbon is from the atmospheric
reservoir of carbon dioxide to green plants and on to consumers, and from both of these
groups on to the microbial decomposer organisms. Algae and autotrophic bacteria also
incorporate or fix carbon from atmospheric C0 2 producing carbohydrates and other
complex organic substances. These are distributed through the food chain and make up
,
Fossil fuels, carbonate rocks,
the tissues of living matter.
in the
are not naturally accessible to plants and animals.
come
and carbon dioxide dissolved
oceans are major additional reservoirs of carbon, although the
available
when
CO
:
is
first
two of these
These "bound" sources of carbon be-
released during the burning of fossil fuels and through the
314
Ecology
C0 2
action of
(from microbial decomposition)
in converting insoluble
Chapter 9
carbonate to sol-
uble bicarbonate.
The
return of carbon dioxide to the atmospheric reservoir
of ways.
Perhaps the best known
animals.
However, by
is
far the greatest quantities of
atmosphere through the
activities
number of
stages, with
Other sources returning
C0
They
C0 2
to the
2
thus oxidize the dead material, either directly
and
H2
fires
and the combustion of
The burning of dried-out
peat, coal, or oil is an
and other organic matter.
example of
utilizing an ancient photosynthetic
is
oxidized to carbon dioxide
The geological component of
end products, completing the cycle.
as
atmosphere are forest
fossil fuels
carbon
carbon dioxide are returned to the
of groups of bacteria and fungi, which use dead or-
ganic matter as their food source.
or in a
achieved in a number
is
through the respiratory processes of humans and
biomass for a source of heat energy. The
each case.
in
the carbon cycle involves (1) the accumulation, slow
decomposition, and compaction of plant material, forming peat, coaj, and
the accumulation and
compaction of animal
shells
oil,
and
(2)
and microscopic diatom skeletons,
Calcium carbonate can also be precipitated in fresh waters
remove C0 2 from the water, thus increasing its pH. When mixed with clay,
these deposits form calcareous marls, which in time become compacted as limestone.
Huge coal deposits and much of the limestone were laid down during the Carboniferous
forming carbonate rocks.
when
algae
period
when shallow water and warm
cussed
in
Chapter
climate predominated over the earth.
carbon dioxide also diffuses into and out of water,
6,
in
As
which
it
disdis-
solves to form carbonic acid (HtCO}).* This dissociates in a series of reactions to form
a hydrogen ion
ciates to
(H + and a bicarbonate ion
)
(HCO^
),
the latter of
form another hydrogen ion (H + ) and a carbonate ion
are reversible and
which
(CO^ 2
).
in turn disso-
All reactions
depend on diffusion gradients and pH.
The discharge of domestic sewage and organic industrial wastes can contribute
The need to reduce organic matter in
large quantities of carbon to receiving waters.
these wastewaters
12).
An
is
one of the principal reasons for wastewater treatment (see Chapter
overall picture of the carbon cycle
tant points to
bear
in
mind
are that (1)
all
is
shown
in
The most impor-
Figure 9—4.
green land plants obtain their carbon from
gaseous carbon dioxide, (2) water plants obtain their carbon from bicarbonate, and (3)
the carbon
complexes formed
in (1)
and
(2) are returned to their original
forms by mi-
crobial decomposition.
9.4.2 Nitrogen Cycle
Another important nutrient cycle
Nitrogen
of
is
is
that of nitrogen,
a critically important element for
living cells, contain an average of
all
shown schematically
all life.
16%
Proteins,
are nucleic acids and
life
continuous supply of nitrogen,
on earth would cease.
'
H CO,.
2
H 2 CO,
with the
has been defined by
CO
;
H:
life
Stumm and Morgan
being truly carbonic acid
(
1981
in its
)
to be
amino
H : C0 3 = CO
predominant form.
Figure 9-5.
which are constituents
nitrogen by weight.
trogenous substances important to
in
:
Other complex
H
:
+ CO
ni-
Without a
sugars.
:
(aq)
+
Sec. 9.4
315
Nutrient Cycles
Chemical
Combination
Peat, Coal and Oil,
and Carbonate Rocks
Figure
9—4
Carbon
cycle.
Source:
Kormondy
1969).
(
The nitrogen cycle is somewhat like the carbon cycle, but with a number of critiEven though 79% of the earth's atmosphere is composed of elemental
nitrogen (N 2 ), this inert gas is entirely unavailable for uptake by most plants and animals. This is in stark contrast to the small amount of C0 2 (0.03%, or 330 ppmv) in the
cal differences.
atmosphere, which
is
A
readily available for plant uptake.
relatively
few microbes are
capable of "fixing" atmospheric nitrogen from the inorganic to the organic form.
microbiological fixation averages 140 to 700
eas
it
can exceed 20,000
A number
trogen.
mg/m 2
•
mg/m 2
•
yr.
Such
In very fertile agricultural ar-
yr.
known
of bacteria, fungi, and blue-green algae are
to be able to fix ni-
Nitrogen fixation involves the direct incorporation of atmospheric nitrogen into
"body" of the fixing organism.
The nitrogen fixers constitute only a very
They can be divided into
symbiotic nitrogen fixers, which are largely bacteria and which are associated with the roots of legumes (members of the pea and bean family) and some other flowering plants, and (2)
free-living nitrogen fixers. The genus Rhizobium includes those bacteria which inhabit the nodules that develop on the roots of members of the pea and bean family.
They are present in soil and infect the fine roots as seedlings grow. The root produces
a special nodule that houses the rhizobia, in which the bacteria convert atmospheric nithe organic
small portion of these groups overall.
trogen (N 2
)
(
into the organic nitrogen constituents of their
cells die very rapidly, this nitrogen
becomes
tries
to find bacteria that
A
)
cells.
Since bacterial
available to the higher plants.
clover and beans actually add nitrogen to the soils
the need tor expensive fertilizers.
own
1
in
Crops of
which they grow and eliminate
large scientific effort
is
under way
in
many coun-
can form a similar association with the cereal grain crops.
316
Ecology
Chapter 9
Atmospheric
Nitrogen (N)
Nitrogen-
Denitrifying
Bacteria
(N0 3
^N0
2
Electrochemical
Fixing
and Photochemical
Organisms
)
Fixation
Nitrate
(NO
Denitrifying
Bacteria
(N0 3
^N
2
)
Nitrate Bacteria (Nitrobacter)"
(N0 2
^N0
3
Deep
Sediments
)
Denitrifying
Bacteria
(N0 3
— NH
3
)
Producers
/
Decay and
Wastes
Herbivory
Decay and
Decomposers
Consumers
•«
Wastes
Amino Acids
Urea, Uric Acid,
Organic Residues
Nitrite
(NH 3
Bacteria (Nitrosmonas)*
— N0
2
)
Ammonifying
Bacteria
(NH 2
— NH
3
)
Volcanic Action
*
Nitrifying Bacteria
Figure 9-5
Nitrogen cycle. Source:
Kormondy
(1969).
Sec. 9.4
317
Nutrient Cycles
The symbiotic
seem
nitrogen fixers
ecosystems and have
to be confined to terrestrial
worm
not been found in aquatic habitats, the one exception being a marine
that attacks
submerged wood.
Among
the nonsymbiotic nitrogen fixers are both aerobic
ing bacteria as well as cyanobacteria.
These occur
in soils
and
and anaerobic
in
free-liv-
both marine and fresh
An
waters and can add substantially to the nitrogen content of these environments.
ditional
which electrochemical nitrogen conversions take
lightning storms in
the soil solution either as nitrates
ammonia by
also be converted to
and fungi
in lakes.
ammonia
(NO^
)
denitrifying bacteria in the
nitrite
converted to nitrate
soil,
it
up from
Nitrate can
).
especially by bacteria
as a source of energy to synthesize their
N07
(
)
(NO7
(
protoplasm.
ammonia
is
by another genus, Nitrobacter (Figure 9-5).
This two-step
)
NOf
own
First the
nitrite is
Both bacterial groups obtain
called nitrification.
Finally, after nitrate
under acidic conditions.
if at all.
by the bacterial genus Nitrosomonas, and the
dation process and then utilize
)
some of
their
the energy to convert
energy from
C0
2
then
this oxi-
to cellular carbon.
has been taken up and converted by higher plants and mi-
metabolized and returned to the major part of
crobes into protein and nucleic acids,
it
the cycle as waste products of that
metabolism
is
(i.e.,
as inanimate organic nitrogen).
heterotrophic bacteria and fungi in both soil and water utilize this organic nitro-
gen-rich material, converting
called ammonification.
and
(NH^
ion
soils.
The process is
nitrogen (NH3)
converted to
Many
ammonium
or as the
Such conversion also occurs in low-oxygen conditions
called denitrification. The nitrifying bacteria, in turn, can use
waterlogged
in
This process occurs only slowly,
is
place.
producer-consumer food chain when plants take
Nitrogen enters the
process
ad-
but generally minor source of atmospheric nitrogen to soils and waters are
nitric
it
and releasing
it
as inorganic
ammonia
in
a process
Other parts of the cycle involve the release of gaseous nitrogen
oxides back into the atmosphere, although these are of limited significance
(Figure 9-5).
As noted
earlier, nitrogen is
introduced into the aquatic environment through the
discharge of domestic sewage and organic industrial wastes.
and ammonia are the main constituents.
and
oxidized to
nitrites
compounds
to rivers
Organic nitrogen (proteins)
process these
The discharge of excessive
nitrates.
and lakes can
macrophytic plants (see Section
In the treatment
may be
partially
quantities of nitrogenous
result in excessive nuisance
growth of algae and
9.6).
9.4.3 Phosphorus Cycle
The phosphorus
cycle, particularly in the aquatic system,
ronmental scientists and engineers.
frequently found to be
in
is
of special interest to envi-
Phosphorus, an essential element for growth,
is
very
limited supply in rivers and lakes, whereas carbon and nitro-
gen are more readily available. Therefore, excessive growth of algae and aquatic weeds
in rivers and lakes can often be reduced or prevented by limiting the supply of phosphorus alone.
'
Phosphorus
is
thus a limiting factor.
In a symbiotic relationship,
two dissimilar organisms
live
together with advantages
foi
each.
318
Chapter 9
Ecology
Phosphorus occurs
and rocks
in soils
[Ca^PO^^OH)].
hydroxyapatite
as
calcium phosphate [Ca3(P0 4 ) 2 ] and as
Since phosphate rock
is
only slightly soluble, quite
small amounts of phosphorus are leached into solution, resulting in concentrations as
low as
Since phosphorus
ppb.
1
natural waters
in plant
required for
is
processes,
all life
further reduced by the biological system.
is
its
concentration in
Because of seasonal changes
and animal production, and because of increased phosphorus input
waters from spring runoff, the concentration of phosphorus
in
to natural
water varies markedly
over the year.
The
input of phosphorus from
human
which phosphates are used
detergents, in
activity
can be far greater than that from
Domestic sewage contains phosphorus
natural sources.
many
bution has been greatly reduced in
ricultural areas that
have received
in feces
and from commercial
(as wetting agents), although the latter contri-
places, following legislation.
fertilizers
and potassium) can be another important source of phosphorus.
phosphorus can reach much higher concentrations
in
Runoff from ag-
(normally containing nitrogen, phosphorus,
in
many
Therefore, soluble
polluted waters, than
it
can
This readily available phosphorus can often lead to the growth
nonpolluted waters.
of nuisance organisms such as filamentous algae, which can cause taste and odor prob-
lems
in
water supplies and clog
of eutrophication of lakes
Phosphorus
is
filters in
water treatment plants.
It
has been noted that the ratio of phosphorus to other elements
organisms tends to be considerably greater than the
ments
in external
is critical
assimilate
plasm.
in the
it
growth
However,
in lakes,
sediment, which eliminates
flow,
is
to other ele-
For their nutrition, plants (and bacteria) require
in lakes.
directly, converting the
phorus cycle
phosphorus
phosphate (dissolved) form, generally as orthophosphate (P0 4
P0 4
to the organic (insoluble)
Decay of these organisms dissolves and
for reuse.
ratio of
sources such as soil or water, indicating that the supply of phosphorus
to biological
phosphorus
The general problem
discussed in Section 9.6.
a constituent of nucleic acids, phospholipids, and numerous phos-
phorylated compounds.
in
is
shown
in
it
much of
The
Particulate organic phosphorus
is
by excretion and decomposition.
( 1 )
removed from
circulation.
solid arrows represent
A
the water
by the
simplified phos-
major pathways of
less importance."
contained within dead and living
of the dissolved inorganic phosphorus in the water
change predominated:
is
from the seasonal water
Figure 9-6.
They
).
in their proto-
releases (mineralizes) the phosphorus
the phosphate
and the dashed arrows are flows of "much
form
is
cells,
and
part
derived from this organic material
Rigler (1964) found that two patterns of phosphorus
was low
inorganic phosphorus
for
most of the
year, but in-
creased from
December
ulate organic
phosphorus showed no consistent seasonal patterns, but a minor increase
occurred in winter.
phytoplankton
tration occurs.
to April (because of limited biological activity); and (2) partic-
The inorganic phosphorus
in the lake waters,
This
is
is
taken up very actively in the spring by
so that a rapid drop in dissolved phosphorus concen-
illustrated in Figure
9-7
for four of the lakes studied.
The
three
forms of phosphorus indicated are particulate (organic), dissolved (P0 4 ), and inorganic
(polyphosphates), which would eventually break
Phosphorus becomes bound
the fall during lake mixing)
and
to
is
down
(hydrolyze) in the water to
P0 4
sediments under oxidizing conditions (as occur
released into the water
.
in
column again under winter
;
Sec. 9.4
319
Nutrient Cycles
Biological
Organisms
(Particulate Organic
Phosphorus)
Decay
Assimilation
Phosphate Deposits
Dissolved
Inorganic
(Surface)
Phosphorus
Inorganic Phosphorus
4
1
j
Deep-Water
Phosphate
Phosphate
(Deep Oceans)
Deposits
Figure 9-6
Phosphorus cycle.
of Ecology, 3rd
ed..
Source:
Adapted from
Odum
(1971), Fundamentals
with permission of W.B. Saunders, Co.
B
10 4
CD
E 10 3 -
i
i
Turnover
i
i
Time
'
i-
i
i
10* -
m
>
o 10
.=>
i
i
|
i
•"^^
1
Teapot Lake ^
Ice
en
3
/:
40
d
c
o
/
'—- Particulate!
O
en
2
o
20-
.c
Cl
Xy
en
O
/
.Dissolved.
Inorganic
•
.c
0.
6
7 8 9 1011 12
1961
Figure 9-7
1
2
3 4 5 6 7
7 8 9
1962
Seasonal changes
in
of the three forms of phosphorus
101112
12
1961
3 4 5 6 7
1962
turnover time of inorganic phosphorus and amounts
in
two lakes
in
Ontario.
Source: Rigler (I964).
320
Chapter 9
Ecology
The summer
anoxic (low-oxygen) conditions of stagnation (see Section 9.5).
components appeared
tion of these
be
to
uously dying and being replaced by
static, yet plant
new
and animal
cells
distribu-
were contin-
Using the radioactive isotope of
ones.
phosphorus, phosphorus-32, Rigler was able to show that phosphorus-32 turned over, or
was reused, with remarkable speed and efficiency. During the summer average turnover
time ranged from 0.9 to 7.5 min. As the season advanced into fall and winter, there was
maximum
a striking lengthening of the turnover time until the
and snow cover was reached.
be 7 min
in
one lake
—only
3.5 times longer than in
days) in another, which was, in
this rapid
tions to
many waters means
more
that
it
summer
—and
grow
winter to
(i.e.,
typical of the rest of the lakes studied.
that enables
a limiting nutrient, additions of
is
under ice
in
10,000 min
It
7
is
phytoplankton popula-
the spring, although the actual scarcity of
in
similated by algae, which then
9.5
fact,
and continuous turnover of phosphorus
expand rapidly
that occurred
At the two extremes, Rigler found turnover
phosphorus
which can be rapidly
in
as-
profusely.
ELEMENTS OF LIMNOLOGY
The study of
(i.e.,
much
the physical, chemical,
fresh water)
is
larger oceans,
called limnology.
is
and biological characteristics of
Its
oceanography.
called
and lakes
rivers
counterpart, dealing with the geographically
important that those dealing with the
It is
use and protection of water resources, including such related activities as irrigation,
waste disposal, and shore erosion, understand
how
freshwater systems work.
information on these practical aspects of limnology
is
Excellent
available from Ruttner (1965) and
Wetzel (1975).
Some
important limnologically related definitions are as follows:
A benthic organism
a lake,
a plant or animal that lives at or near the bottom of
is
stream, or ocean.
river,
The epilimnion
is
the upper layer of water
The euphotic zone
is
that surface
volume
in
a lake.
of
water
in
the ocean or a
deep
lake that receives sufficient light to support photosynthesis.
The hypolimnion
main
at
is
the lower layer of water
a constant temperature during the
Limnology
is
tics of rivers
a lake or pond, which
in
will re-
summer months.
the study of the physical, chemical, and biological characteris-
and lakes
(i.e.,
Plankton are any small
fresh water).
free-floating
organisms
living
in
a body
of water;
phytoplankton refers to the plant species (algae), and zooplankton to the animal
species (crustaceans,
rotifers,
protozoa)
feeding
on other forms
of
plankton.
The metalimnion
cline
is
the middle layer of water
occurs (temperature and oxygen content
in
fall
a lake, where the thermooff rapidly
with depth).
Sec. 9.5
321
Elements of Limnology
9.5.1 Quantity and Quality of Water
As an ecosystem,
a lake or river
characteristics are determined
and by the drainage waters
by
itself is a rather artificial unit in that
by the nature,
that enter
it.
size,
many
of
its
and shape of the land surrounding
The ecological
it
unit, then, is the lake or river
The latter is also known as the catchment area or
The amount of water entering a lake or river is determined by the
amount of precipitation falling in the drainage basin both rain and snow (in the mountogether with
its
drainage basin.
the watershed.
—
fog and intercepted stratus clouds can be an important additional source of precip-
tains,
itation)
—by
the size of the drainage basin,
surround the body of water.
that
may
act like a
sponge, so that
and by the nature of the vegetation and
Deep organic
much
peat soils with
soil
bog vegetation on them
of the rainfall over a short period
retained in the
is
watershed, whereas a similar amount of rain on a hard, granitic rock basin, with sparse
vegetation and shallow soil cover, might mostly run off and enter the lake or river
within a few hours of the occurrence of the rainfall.
Surface water quality will be affected by the atmosphere through which the rain
falls,
by the nature of the
soil
and vegetation over which the surface water runs
by the extent of human activity
and lakes
may
Major bird mi-
grations can have a substantial effect on the quality of water in lakes that
paths; for example, waterfowl
from heavily forested areas
a
to
humic
silt
may
along their
Runoff
and brownish yellow
in color,
will be rich in organic matter
from
soil erosion.
also be of great significance.
Land-use
levels of nitrogen, phosphorus, organic matter
(through acid mine drainage).
may be
The
activities
by people
in the
watershed
Agricultural activities can substantially influence the
Mining increases the concentration of metals
water quality
lie
bring in salts and nutrients in their excreta.
Runoff from barren, deforested land may be very turbid because of
acids.
heavy load of
may
and
rivers
be changed by industrial gases drifting in from distant sources and dis-
solving in the rainwater falling on the catchment area (see Chapter 5).
due
off,
The composition of waters entering
in the basin.
effect of
and bacteria entering a body of water.
in water, as
sewage and
well as the acidity of water
industrial waste discharges
on
severe, particularly with regard to organic content.
9.5.2 Biotic Communities
Organisms
that live suspended in the water column are called plankton.
In swiftly
moving waters they do not have time to develop significant populations, but as the flow
rate slows on the lower, gentler slopes of the catchment, and as the volume and depth
of water increase, they begin to build up distinctive plant and animal planktonic populations,
termed phytoplankton and zooplankton, respectively. The phytoplankton are a
diverse group of microscopic green algae from a dozen different groups.
The predomiThe desmids and blue-green algae can
form enormous populations under favorable conditions, causing algal blooms, in which
they color the water and can produce distinctive odors and tastes difficult to remove in
water purification plants. Cell numbers can reach 8 x 10 6 mL"
Other groups include
nant groups are the single-celled green algae.
1
.
the beautiful sculptured cells of the diatoms with their silicon skeletons, the yellow-
322
Ecology
Chapter 9
green algae, the euglenoids, and the dinoflagellates (see Section 8.2.4).
In marine wabrown and red algae are of great importance, but in fresh waters they have very
few representatives. Examples of some of the freshwater phytoplankton are shown in
ters the
Figure 9-8.
zooplankton include mostly small crustaceans (the crab and
In fresh water, the
Many of these filter large volumes of water each day, from
which they extract phytoplankton and smaller zooplankton (protozoa) as well as bacteria
shrimp family) and
rotifers.
Others are more actively carnivorous, seeking out prey and
and dead organic matter.
grabbing, biting, and tearing them.
Some
(im.
Most of them
bladders.
Zooplankton vary
in size
or. in the
larger forms,
thus pursue their prey and also change position in the water
Some show remarkable
ing grounds or to avoid predators.
meters per day, feeding
Some
at night in the
insect larvae
and
fish fry
plankton and on zooplankton.
may
3000
to
droplets or air
oil
are quite mobile, possessing groups of cilia (hairlike structures)
or fiagella (small whiplike structures)
day.
from about 70
of them have specific buoyancy mechanisms, involving
swimming
legs.
column
maximize feed-
They can
diurnal migrations of several
upper waters and sinking
form
to
darker depths by
to the
part of this floating world, feeding
on phyto-
and
mammals
In turn, fish-eating fish, reptiles, birds,
join the ecosystem.
As
may
the flow rate of the water drops in the lower parts of the catchment area, sediment
deposit on the bottom,
(macrophytes) and a
providing a rooting
medium
for
plants
larger aquatic
habitat for mud-living benthic (bottom-living) invertebrates (Figure
The latter burrow in the rich deposit of silt, clay, and organic material, and feed on
new supply of food at the surface of the mud. The aquatic oligochaete worms (earth-
9-9).
the
worm
sels
family), chironomids (midge larvae), and bivalve mollusks such as freshwater
and clams
live in
mus-
such benthic muds. Reed beds emerge from the water and together
with the submerged macrophytes, provide a physical habitat for a great diversity of invertebrates
and
fish,
and a food supply for waterfowl, algae, and bacteria.
In the case of a river, as
creasingly
comes
to
accumulate, with the clays and
Dead
algal
it
increases in size and the flow rate drops further,
resemble a shallow lake
and zooplankton
silts,
in its biota.
Sand,
silt,
it
in-
and clay particles
especially, sinking very slowly through the water.
accumulate on a seasonal basis, together with
cells also
pollen from the spring pollen rain and the feces of the myriads of zooplankton and fish
of the upper waters.
terial.
Low oxygen
Precipitates of iron,
levels reduce rates of
breakdown of
this
organic ma-
manganese, and phosphates can occur under such anoxic
conditions and are incorporated into the sediments.
The
nutrients being
added
to the
upper layers of sediment can be released back into the water column and provide part
of the spring flush of available phosphorus, as discussed
trients are buried
tively lost to the
in
Section 9.4.
Once
the nu-
beneath a few millimeters of sediment, they are sealed off and effecwater column and
its
biota.
9.5.3 Light in Lakes
The amount of
is
light available at different
important to the ecology of the lake.
water depths
Visible light
is
in lakes (or in
very large rivers)
absorbed by the water
itself,
by
323
Elements of Limnology
Sec. 9.5
^m
25
Cyanophyta (blue-green algae) (d) Oscillatoria, (i) Microcystis;
Chrysophyta (yellow-green or golden algae) - (a) Dinobryon;
-
Chlorophyta (green algae)
desmids
strictly
-
now placed
Bacillariophyta (diatoms)
-
(e)
in
(f)
Pediastrum,
(b)
the Charophyta),
Cyclotella,
(I)
Staurastrum
(j)
(a
member
of
a group called the
Chlamydomonas;
Asterionella;
Euglenophyta (euglenoids) - Phacus;
Cryptophyta (cryptomonads) - (g) Rhodomonas;
Pyrrophyta (dinoflagellates)
Haptophyta
Microcystis
much as
(k)
-
(h)
Ceratium;
is a very large alga, of which a diagram of the entire colonly could occupy as
page. Only a few cells are shown.
(I)
this
Figure 9-8
jam).
-
Prymnesium;
Sonne:
Some
typical freshwater phytoplankton algae,
Moss
(I'MOi.
Sec also Table 8-2 for
drawn
to scale (1
cm =
a simplified classification
25
system.
324
Chapter 9
Ecology
Forested jk
Watershed
j&
#J|
Catchment
Area
Benthic.
Invertebrates
in
Figure 9-9
Diagram of
Sediment
a lake (or large river), with biota in the shallow waters, in the
benthic muds, and in the water column (not drawn to scale).
The highest and lowest wavelengths
dissolved substances, and by particulate matter.
(the reds
is
and blues) are absorbed
best, so that
below a few meters depth,
predominantly of the green and yellow wavelengths.
tively
absorb the red and blue
of a given wavelength
is
light.
In
each successive increment of water depth,
reduced by a fixed proportion (Figure 9-10).
lignt is
never totally extinguished, but before
falls to
about
1%
light quality
Organic materials very effec-
of the surface intensity.
light
Theoretically,
reaches visually undetectable levels
it
This has a conventional significance, since
it
it
approximately describes the level where algal photosynthesis
is
reduced to the point that
compensation point. Below it, algal
which phytoplankton cells can
thrive.
Sometimes the bottom of a lake is in the euphotic zone, in which case rooted
water weeds cover it. In very clear lakes this can be quite deep (20 to 50 m), with a
theoretical maximum of around 200 m. In most of the world's bodies of water, primary
productivity is confined to less than half of the mass of water, and in some deeper lakes
the euphotic zone may be only a thin surface skin, below which lies a huge dark world.
it
only just matches respiration.
growth cannot occur; above
This world
is
not devoid of
it
This
is
life,
is
called the
the euphotic zone, in
however, as zooplankton, bacteria, fungi,
fish,
and
in-
vertebrates can live there permanently or enter for short periods.
9.5.4 Temperature and Vertical Stratification of Lakes
In turbulently
flowing streams,
ature gradients develop in the
in
which the waters are continuously mixed, no temper-
summer months.
In slow-flowing
deep
rivers,
and espe-
325
Elements of Limnology
Sec. 9.5
Log
Intensity (°o of Surface)
Intensity
100
Figure 9-10
The
Absorption of
left-hand panel
reflection losses
the
shows
water
bottom, a
Heat radiation
develops.
upper warmer layer
of that
(1980).
found at the surface (after
with
tends to heat up more rapidly than the water
insufficient to
mix
from top
the lake waters
1
or 2
m
of water.
called the epiiimnion. and the lower denser cold layer
is
to
bodies of water, a steep gradient of temperature
very largely absorbed in the top
is
Moss
The right-hand panel shows the same data
The gradient is the extinction coefficient.
summer
in
When winds and currents are
common occurrence in deeper
it.
as a percentage
for)
as natural logarithms.
cially in lakes, the surface
below
light intensity
have been allowed
light intensities
uniform water column. Source:
light in a
This
down
to
hypolimnion (Figure 9-11). Between the two is a
transitional layer called the metalimnion.
In this transitional zone, the temperature
changes very rapidly over a short change in depth. The occurrence of this rapid vertical
change in temperature with development of stratification is called the thermocline.
The productivity of a lake is directly affected by thermal stratification and seathe
bottom of the lake
Lakes
sonal mixing.
(Figure
9-11) and
which
called the
in the
temperate zone thermally
circulate each spring and autumn.
the surface, while the
at
is
more dense water
the density of water
and reduced
light
surface waters
ter forms.
is
a
at
4
maximum)
C
stratify
during winter and
In the winter, ice
summer
C
covers
(more precisely, 3.94 C, the temperature
sinks to the bottom.
penetration inhibit biological productivity.
warm
near
The cold temperature
During summer, as the
rapidly and spring winds subside, a less dense surface layer of wa-
This epiiimnion mixes continuously during the
summer and
supports the
growth of phytoplankton.
Thermal
stratification
also
influences water quality.
The epiiimnion supports
326
Chapter 9
Ecology
Summer
Winter Stratification
Stratification
Sunlit Circulating
Warm Water
18-22 °C
°C, Ice
Cover
1 1 1 1 1 1 1 1 ) 1 1 1 1 1 1 1
m
CD
Q
Dark, Stagnant,
Cooler Water
4-10 °C
4°C
Temperature
Sediments
Figure 9-11
Thermal
stratification
abundant algal growth, while the hypolimnion
oxygen content.
Hydrogen
sulfide,
in
of a deep lake.
eutrophic lakes decreases in dissolved
odorous organic compounds, and reduced iron can
be released from bottom sediments as a result of anaerobiosis.
cation, water supply of highest quality
9.6
Temperature
is
During thermal
stratifi-
usually found just below the thermocline.
EUTROPHICATION
9.6.1 The Problem
The word eutrophication comes from two Greek words; eu, meaning "good" or "well,"
and trophos meaning "food"; thus eutrophic can be translated as "nutrient (food) rich."
A'l lakes undergo a natural enrichment over time.
Sediments are carried
surrounding watershed, and soluble nutrients are leached from them.
trophication
is
a slow process
periods of thousands of years.
in
from
the
This natural eu-
from a human point of view, frequently taking place over
The discharge of untreated sewage and
dustrial wastes into a lake hastens the process greatly.
times referred to as cultural eutrophication.
agricultural or in-
This accelerated process
Lakes
in
some-
is
which the nutrient
level is
which are characterized by abundant littoral (shore-dwelling) vegetafrequent summer stagnation with algal blooms, and absence of cold-water fish spe-
particularly high,
tion,
cies, are said to
be eutrophic; Lake Erie
are called oligotrophic (oligo
a lake.
such a lake.
Lakes with low nutrient levels
"deficient in");
Lake Superior
is
Lakes with intermediate nutrient levels are called mesotrophic.
Eutrophication
over time,
in
is
meaning "small" or
in
is
the natural process of nutrient enrichment that occurs,
a body of water.
The
resulting biological growth, mainly algae,
the epilimnion dies and settles to the hypolimnion, where
depletes the oxygen from the water.
it
decays and
such
Sec. 9.6
327
Eutrophication
Eutrophication
is
one of the most significant and worldwide water quality prob-
The most important problems created by excessive eutrophication
lems.
•
The detrimental
•
The
are:
effect on the commercial and sport-fishing industry due to
changes in the species of fish found in lakes, caused principally by the low levels
of oxygen found in the lower waters.
effect
on recreation and tourism through excessive growth of algae and other
aquatic plants, rendering the water and beaches unfit for recreational purposes.
The filamentous algae
ing, rotting piles
The abundant
•
washed onto
are
algal
blooms, which create an unpleasant
supplies and plug intakes and
filters in
Thus a biologically poor lake
is
water use and recreation.
sphere
we
taste
and odor
water
in
water treatment plants.
preferable to a fertile one from the standpoint of
This appears to be a paradox since
in
some
parts of the bio-
more
are doing everything possible to increase fertility in order to produce
we
food, whereas in other parts
are trying everything possible to prevent fertility.
case of land, more food from increased
fertility
does not harm the land.
In the
However, over-
of lakes and the resulting algae can, in the early stages, impair the quality
fertilization
of the fish
the beaches during storms, leaving stink-
of organic matter.
we
and eventually,
are trying to produce,
extreme, destroy
in the
all
aquatic
life.
9.6.2 Physical-Chemical and Biological Changes
The importance of phosphorus and nitrogen
ognized widely
formation
on
1960s.
until the early
lakes
available
for
in the
eutrophication process
Therefore, there
these
is
was not
rec-
relatively little long-term in-
two elements.
Changes
chemical
the
in
composition of lakes over a long period have been documented but not necessarily for
Figure 9-12 gives information on a
these most critical elements.
number of chemical
changes for Lake Erie over a 70-year period.
Pioneering work was done on several Wisconsin lakes to establish the levels of
phosphorus and nitrogen concentrations below which nuisance growth
Upper concentration
occur.
orthophosphate phosphorus
limits of 0.3
at
mg/L of
blooms when
all
the time of spring turnover of the lake
now been found
in
a lake
is
also low.
plants and animals.
change
in
be
As
in
nutrient enrichment occurs, the trend
turn benthic algae
composition from the
of desmids, which results
little
biomass.
Annual
At the same time, they have a great diversity of species of
higher rate of production, and less or changed species diversity.
production occur, and
to
to trigger
change the numbers and types of biota present
Oligotrophic lakes normally have clear water and contain
productivity
mg/L of
were thought
other nutrients are available (see Section 12.3.1).
Rising nutrient levels
there.
probably not
inorganic nitrogen and 0.02
suitable then, but values one-third to one-half of these have
algal
will
in
initially
decreased
is
to
more biomass, a
Large increases
and zooplankton increase.
in algal
Plankton
may
sparse numbers of diatoms to a dense growth
light penetration.
Finally, blue-green algae
come
328
Ecology
Chapter 9
40
35
Calcium
30
2
25
CD
Q.
(/)
20
c
CC
CL
15
10
Sodium + Potassium
5 -
J
L
1890
1900
Figure 9-12
to
1910
Chemical changes
dominate the water column.
10,000 to 100,000 cells per
As some of
1920
in
Lake
1930
Year
1940
1950
1890-1960. Source:
Erie,
During such algal blooms the
1960
Beeton
(
1970
1965).
cell density
may
reach
milliliter.
some essential nutrients or
become food for bacteria. Bacterial decomposition of the dead
then consumes the dissolved oxygen, leaving the water beneath the
the algae die, either through exhaustion of
for other reasons, they
algae and bacteria
slimy surface oxygen deficient and therefore unable to support the species that people
value most.
Trout and bass are replaced by coarse
The latter group
thus causing an economic loss.
yellow perch, and smelt.
sportfishing,
much
is
fish
such as suckers, carp, sunfish,
less valuable for
commercial and
9.6.3 Control of Eutrophication
It
has been demonstrated
be reversed
if
at
Lake Washington
the inflow of nutrients
is
in Seattle that cultural
substantially reduced.
eutrophication can
Before taking corrective
measures, a quantitative survey of nitrogen and phosphorus sources and limnological
studies of the lake are essential to establish
the majority of
its
nutrients are
its
trophic levels and to determine whether
from point or diffuse sources.
Point sources, such as
municipal wastewater discharges, can be controlled by alternative disposal on land,
di-
Sec. 9.6
329
Eutrophication
version around the lake, or removing the nutrients from the wastewater prior to dis-
Non-point-source loads, such as agricultural runoff, can be
charge to surface waters.
reduced through land management techniques that prevent
sive use of fertilizers.
20% and
than
30%, supplementary
nitrogen by about
approximately 8
Emphasis
is
erosion and avoid exces-
Since conventional treatment methods reduce phosphorus by less
mg
of phosphorus/L and 30
mg
of nitrogen/L (see Table 12-1).
normally placed on phosphorus removal, since phosphate
the controlling factor in the enrichment of
may
nutrient removal in the plant
Typical biologically treated wastewater con-
be required to protect the receiving waters.
tains
soil
most
is
believed to be
lakes.
Several temporary controls can be used to arrest or reduce nuisance effects in eu-
Chemical control through application of copper
trophic lakes and reservoirs.
algicide,
is
effective for a short time.
near-shore areas,
oxygen depletion
an
in
Trent Canal and Kawartha Lakes system in Ontario).
(e.g., the
is
sulfate,
Harvesting of aquatic weeds can be practiced
mechanical aeration and mixing
a serious concern,
Where
may
help.
These methods can only be considered stop-gap measures, since they do not control
put but merely ameliorate
its
in-
consequences.
9.6.4 Case Study: The Great Lakes
The Great Lakes system (Figure 9-13)
between the United States and Canada
and,
is
good example of
a
The
possible, reverse the trend of eutrophication.
if
very large lower Great Lakes
dustrialized population can
is
do
international cooperation
to prevent further deterioration of
water quality
serious deterioration of the
damage a
a sharp reminder of the inadvertent
to water quality in a short period
large in-
and the large and ex-
pensive effort needed to reverse this trend. The Great Lakes, with a shoreline of 10,500
km, an area of 248,000
km 2
,
and a volume of 25,000
water supply of the United States and almost
Over 10 million people
live in its
to a very substantial extent
size of the lake.
TABLE
9-5
Details of
Lake
(km 2
)
95%
of the surface
(WEF
The
relative effects
on the lakes are deter-
some of
the morphometric data are given in Table 9-5.
Maximum
Mean
depth
depth
(m)
(m)
ST.
LAWRENCE GREAT LAKES
Hydraulic-
Volume
(km 3 )
Shoreline
residence
(km)
time (yr)
Superior
83,300
397
145
2.000
3,000
190
Huron
59.510
223
76
4,600
2,700
40
Michigan
57,850
265
99
5,760
2,210
36.5
Erie
28,280
60
21
540
1,200
3
8.760
225
91
1.720
1,380
8
Ontario
Sonne:
1
1993).
by the human population along the shoreline and the
MORPHOMETRIC DATA FOR THE
Area
contain
of the world's supply
basin and catchments and discharge their wastes and
industrial by-products to the Great Lakes.
mined
20%
km 3
Data derived from Hutchinson (1957).
1
330
Ecology
The Great Lakes
Minnesota
Cleveland
Elev. 183.0
m
Elev. 176.4
m
Pennsylvania
i
Ohio
'
Elev. 173.9
m
Lakes
Michigan &
Lake
Huron
Ontario
10r-
\////k
Superior
Michigan
Huron
Erie
Ontario
Great Lakes Storage
Figure 9-13
The Great Lakes. Source:
U.S. Department of the Interior (1968).
Chapter 9
Sec. 9.6
331
Eutrophication
Lake Superior
by
is
190 years for the water
and
far the largest
the smallest population density in
in
it
of the Great Lakes and has
least polluted
watershed.
its
Also,
estimated to take more than
is
it
Lake
to be totally replaced.
Erie, in contrast,
smaller, shallower lake, with an estimated population of over 15 million in
Water replacement
basin.
is
much
a reduction in incoming pollution
ognize, however, that
if
itself,
much
drainage
from
faster than in the other Great Lakes, so benefits
would be evident much sooner.
the pollution
than with the water column
a
is
its
it
is
problem
is
important to rec-
is
associated with the sediments rather
much more permanent
a
It
feature.
In
Lakes
Erie.
Michigan, and Ontario, the occurrence of mercury, PCBs, and dioxins are substantially
related to sediments immediately
downstream of
particular industrial discharges.
Agricultural drainage into the lakes affects water quality in
and Ontario and has been a major factor
in the algal
Lakes Michigan, Erie
problems of Lakes Michigan and
where both phosphorus and nitrogen have been entering the lake waters from
Erie,
farms
in the
from road
watershed.
Problems of increased concentrations of such
salting in the winter (e.g., in
salts as chlorides
Lakes Erie and Ontario) and sulfates from major
growing concern.
Use of the lakes for swimming, boating, fishing, and other water sports as well as
Unfortunately, many
cottage development is of great importance to the public.
industries are of
for
around Cleveland and Detroit, are grossly polluted, and Toronto
beaches, especial 1\
beaches have been posted as unsafe for swimming since 1983, causing a considerable
public outcry.
orm
The closing of beaches is always associated with excessive fecal colifwhich indicate potentially dangerous levels of pathogenic bacteria.
bacterial counts,
The Great Lakes provide
vital
This has been a key factor
centers.
Great Lakes, and
navigational routes to and from the major trading
in
the
development of
cities
and towns around the
spurred development of the Welland Canal and later the
it
St.
Law-
rence Seaway system, both of which have stimulated international trade.
The Great Lakes and
the rivers draining into
them have often been used
grounds for waste from industry and from urban populations.
Power
domestic and industrial needs has increased greatly.
power
stations,
make huge demands
terials
dumped
in the past
fire in
have actually created
fire
range of elements
each of the
The decline of
quite dramatic in
all
the
Unwanted maIn fact, some
hazards. The Cuyahoga
fire
at least
three fires
five
asitic fish that attaches itself to the
body of lake
whitefish chub, blue pike, and suckers.
body
fluids,
and one
Huron,
it
that
wide
in a
commercial fishing industry over the past 30 years has been
of the lower Great Lakes.
When
the
Welland Canal opened up the
Falls,
path for the sea lamprey to enter the Great Lakes from the Atlantic.
ter,
to hydrocar-
Great Lakes since about 1900 (Beeton, 1965).
Great Lakes to shipping by providing a bypass around Niagara
their
due
Figure 9-14 shows the increases that have occurred
then.
in
stations, especially nuclear
and navigational hazards.
1969, and the Buffalo River has had
bon dumping since
dumping
as
for water for both
for a constant supply of cooling water.
of the rivers draining into Lake Erie are officially declared
River caught
Demand
It
eventually killing them.
trout
and
it
also
opened up
The lamprey
to other fish, including
is
a
a par-
salmon,
rasps holes in the unfortunate victims and sucks
Its
entry into the Great Lakes has been a disas-
no one really could have foreseen.
In
Lakes Superior, Michigan, and
has almost eliminated lake trout populations (Figure 9-15).
The alewife
is
a
332
Chapter 9
Ecology
40
20
Sodium + Potassium
Chloride
o15
§30
o510
Q.
§.20
Ontario
CO
c
Erie
Michigan
.V
6
h
to
*
^~
Superior
£10
Erie
Michigan
Superior Huron
1850 1870 1890 1910 1930 1950 1970
Year
40,
————
1850 1870 1890 1910 1930 1950 1970
Year
40
—
,
Ontario.
Calcium .....
Michigan
§30
Sulfate
o 30
Erie
Huron
o3
20
20 h
o>
Q.
Q.
Ontario
Superior
CO
£10
Superior
J_
1850 1870 1890 1910 1930 1950 1970
Year
Figure 9-14
Data
for
Lake
Changes
Erie,
in the
1850 1870 1890 1910 1930 1950 1970
Year
chemical characteristics of Great Lakes waters.
1958: Lake Huron, 1956; Lake Michigan, 1954, 1955, 1966: Lake
Ontario, 1961; Lake Superior, 1952, 1953, 1961, 1962 from the
Laboratory, U.S.
Bureau
of
Commercial
Fisheries.
All lakes,
Ann Arbor
Biological
Great Lakes Water Quality
Board (1982).
small fish that has also invaded through the canal and
young
other fishes' eggs and competes with their
lem
until the sea
lamprey eliminated the larger
ton (1965) gives a detailed account of the
become a problem.
The alewife was
It
fish that naturally
many
feeds on
not a prob-
for food.
preyed upon them. Bee-
associated changes in biota that have
taken place, especially the changes in the phytoplankton, the spread of nuisance algae
such as Cladophora, and the decline of
oxygenated waters for
their survival.
many
insect larvae that
depend upon clean, well-
Since the early 1990s the serious problems arising
from the invasion of the Great Lakes by zebra mussels, especially
restriction of, water intakes,
Although the emphasis
sources of nutrients,
it
is
their
attachment
to,
and
have become of increasing concern.
in
what has
just
been said has been on land and water as
important to realize that atmospheric deposition
contributor of both phosphorus and nitrogen to the Great Lakes.
is
a significant
Over 30% of
the phos-
phorus loading to Lake Michigan, for example, comes from the atmosphere.
Finally,
the Great
it
needs to be stressed that
it
was
largely because of the public outcry in
Lakes region about the polluted, eutrophic
state
of Lakes Erie, Michigan, and
Ontario that the phosphorus ban on detergents was introduced
in
Canada
in the early
333
Eutrophication
Sec. 9.6
Lake Superior
200
-
150
-
100
50
c
o
Q.
300
250
CD
o
c
CO
"O
c
H 200
c
o
o
150
oo
4,
<
100
Q.
50
_l
250
00
E
CO
CO
Oi
- 200
- 150
0>
CO
-
N/^dk ^u
±
1930
1935
1945
1940
1950
1955
1960
100
50
1965
Lake Trout
Sea Lamprey
Figure 9-15
Production of lake trout and abundance of the sea lamprey
Superior. Michigan, and Huron. Source:
of the
(E)
Journal
marks the
completion
oj the Fisheries
first
Smith
(
197
1
).
Reproduced with
Research Hoard of Canada 25
sea lamprey record, (S)
of the initial series of
is initiation
of
(4)
1
Lakes
in
the permission
1968): 667-693.
chemical control, and (C)
is
chemical treatment.
1970s.
This, together with mandatory treatment of wastewater, has brought about sig-
nificant
improvement
ticular, is
9.6.5
A New
Improvements
in
in the
water quality of the Lower Great Lakes.
Lake
Challenge: Coastal Estuaries
to the Great
Lakes have not been matched
in
coastal estuaries and bays
North America, most of which suffer from increasing nutrient overload.
ples
•
Erie, in par-
being restored to health.
among
the 127 estuaries in the United States have been described by
Some examCone
(1994).
Peconic Bay (on the eastern end of Long Island). Coffee-colored blooms that
have appeared every summer since 1980 have, indirectly, eliminated bay scallops.
New York City sewage plants are the suspected cause.
334
•
Florida Keys.
Coral beds are dying and the shrimp industry has collapsed as a re-
of excessive nutrients.
sult
•
Chesapeake Bay.
In the largest estuary in the
United States
of the eastern seaboard) the oyster industry has declined
trient buildup, overfishing,
•
Chapter 9
Ecology
90%
(it
drains one-fourth
since 1960 from nu-
and disease.
Waquoil Bay (near Cape Cod, Massachusetts).
The bay
is
covered with a thick
layer of green algae and the once abundant oysters and scallops are disappearing.
Sources of the nutrient pollution are varied and include:
•
Sewage
•
Agricultural runoff from land that has been overfertilized
•
Vehicle emissions that contribute nitrogen oxides to the atmosphere
plants that lack nutrient removal facilities
The need
United States to strengthen the Clean Water Act to correct the
in the
problem of nutrient overload
is
evident.
financial considerations will be the
"someone
But legislation
major obstacle
is
only part of the solution, and
to effective
cleanup measures unless
else" pays.
PROBLEMS
9.1. Cite three
examples of large diversified ecosystems and note the factors threatening
their
existence.
9.2.
Define the following terms, using examples where necessary
(a)
Autotroph and heterotroph
(b) Primary producer
(c)
9.3.
Trophic level
(d)
Food chain biomagnification
(e)
Denitrification
The
rates of productivity
Comment on
this
on an annual basis differ very widely among different ecosystems.
and speculate as
to the
major climatic factors controlling these
differ-
ences.
9.4.
The flow of energy within an ecosystem
input,
whereas the flow of nutrients
is
is
unidirectional and dependent
cyclical.
Comment on
this
upon constant
and explain how
it
solar
cre-
ates constraints.
9.5.
It
has been said that the relative efficiency of energy utilization
plants.
9.6.
Is this true,
Respiratory use of energy
deal.
in
animals
is
higher than
in
and what are the key factors underlying the situation?
at different
trophic levels in different ecosystems varies a great
Using data given for Cedar Bog Lake, as well as a cornfield and
salt
marsh, discuss
this statement.
9.7.
Describe the cycling of nitrogen
in
ecosystems and the role of atmospheric nitrogen
supply of nitrogen to higher plants.
9.8.
Draw
a simplified nutrient cycle schematic for:
in the
Chapter 9
335
References
Carbon: showing oxidation, decomposition, and photosynthesis as occurs
(a)
(b) Phosphorus: indicating the processes
occurs
in lakes
Nitrogen: showing nitrification, denitrification, assimilation, and deamination and the
(c)
nitrogen
9.9.
in foresl soil
between particulate and dissolved phosphorus as
What
compounds formed
meant by
is
at
each step as occurs
in agricultural lands
the following'.'
Drainage basin
(a)
(b)
Macrophytes
(c)
Zooplankton
(d) Algal
blooms
(e)
Benthic organisms
(f)
Euphoric zone
(g) Oligotrophic
(h)
Thermocline
(i)
Hypolimnion
9.10. Describe the
development of a thermocline
mocline varies
9.11. Explain
how
in lakes
how
of different latitude and
the ther-
in persistence.
thermal stratification and seasonal mixing occur,
water quality considerations, and
at
what
why
these are important for
water supply should be
level an intake for a
lo-
cated.
9.12.
Why
is
the temperature of 3.94
C
of great importance
in
understanding seasonal changes
in
lakes?
shown
9.13. Phosphorus has been
to
have a very rapid turnover
What
in lakes.
is
the relevance
of this to potential problems regarding eutrophication and algal blooms?
become
9.14. Eutrophication has
What
America.
9.15.
is
why
it,
problem
a very serious
is it
a problem, and
in
how can
many
it
lakes in Europe and North
be solved?
The lower Great Lakes have seen profound changes in their fisheries
What arc some of these changes, and why have they occurred?
in the past
60
years.
REFERENCES
Beeton, A. M. "Eutrophication of the
10 (1965): 240-254.
St.
Lawrence Great Lakes." Limnology and Oceanography
Cone, M. "Algae Blooms Bursting Out All Over." Los Angles Times,
Star,
May
as reported in the Toronto
28, 1994.
Gates. D. M. Energy Exchange
in the
port on Great Lakes
New
Biosphere.
Great Lakes Water Quality Board. Report
York: Harper
&
Row,
to the International Joint
1962.
Commission: 1982 Re-
Water Quality. Windsor, Ontario: International Joint Commissions,
1982.
Hi NT, E. G., and
Bismol
i.
A.
I..
"Inimical Effects on Wildlife of Periodic
Clear Lake." California Fish ami
Hutchinson. G.
E.
A
Came 46
DDT
Treatise on Limnology, Vol.
1.
New
York: Wiley, 1957.
JUDAY, C. "The Annual Energy Budget of an Inland Lake." Ecology 21 (1940):
Kormonoy,
E.
J.
Concepts
oj Ecology.
Application to
(1960): 91-106.
Hnglewood
Cliffs, N.J.: Prentice Hall,
438^50
1969.
336
Chapter 9
Ecology
Lindeman, R.
L.
"The Trophic-Dynamic Aspect of Ecology." Ecology 23 (1942): 399^18.
Moss, B. Ecology of Freshwaters. Oxford: Blackwell
Odum,
E.
Rigler,
P.
W. B. Saunders, 1971.
ed. Philadelphia:
Time of Inorganic Phosphorus
Types of Lakes." Limnology and Oceanography 9 (1964): 511-518.
H. "The Phosphorus Fractions and the Turnover
F.
ferent
Ruttner,
Fundamentals of Ecology, 3rd
Scientific Publications. 1980.
F.
Fundamentals of Limnology. 3rd
ed. Translated
by D. G. Frey and
F.
E.
J.
in Dif-
Fry To-
ronto: University of Toronto Press, 1965.
Smith,
S.
H. "Species Succession and Fishery Exploitation
on the Environment,
Stumm, W.. and Morgan,
Transeau,
E. N.
T. R.
J.
J.
Detwyler
(ed).
New
Aquatic Chemistry, 2nd ed.
"The Accumulation of Energy by
Great Lakes." In Man's Impact
in the
York: McGraw-Hill. 1971.
New
Plants."
York: Wiley-Interscience, 1981.
Ohio Journal of Science 26 (1926):
1-10.
U.S. Department of the Interior. Proceedings, Progress Evaluation Meeting, Pollution of Lake
Erie and Its Tributaries. Washington, D.C.: U.S. Department of the Interior, Federal Pollution Control Administration. 1968.
WEF
(Water Environment Federation). "The Great Lakes." Federation Highlights 30
(9).
Septem-
ber (1993)
Westlake, D.
F
"Comparisons of Plant Productivity." Biological Reviews 38 (1963): 385^425.
Wetzel. R. G. Limnology. Philadelphia: W.
B. Saunders. 1975.
Whittaker, R. H. "Experiments with Radiophosphorus Tracers
logical
Monographs
31
(
1
96
1
):
1
57-1 75.
in
Aquarium Microcosms." Eco-
PART
3
Technology and Control
CHAPTER
10
Water Resources
J.
10.1
Glynn Henry
INTRODUCTION
Water resources management
supplying water
proach
in
minimum
at
in
North America has evolved from
which a wide spectrum of objectives
trol to the aesthetic
its
original goal of
cost to promote development, to the contemporary apis
examined.
Benefits,
enjoyment of the environment, are now evaluated
in
from flood conterms of
human
The application of this broadened concept must be based on an
understanding of the many factors that influence decisions. These factors and their influence on water resources management are described in this chapter. Technical backneeds and
activities.
ground information on the overall quantities of water available and the requirements for
various uses precedes a discussion of
management
alternatives.
The need
for adequate
data and the role of systems analysis in assessing the environmental consequences of
these alternatives are explained.
Elements of successful planning, including
efits
(especially
noneconomic ones), and
The importance of
discussed.
In
flexibility,
methods
for
measuring ben-
utilization of public involvement, are outlined.
these requirements and suggestions for implementing
subsequent sections of the chapter
we
them
are also
deal with legislation affecting water
management, with emphasis on the agencies involved and their areas of
Economic and political considerations are other major concerns dealt with.
jurisdiction.
337
338
Water Resources
Chapter 10
improve the management of our water resources advanced greatly
The challenge today is to apply these new methods to practical situTwo case studies are used to illustrate this approach. The first example is the
Techniques
to
during the 1970s.
ations.
controversial Peripheral Canal in California.
In addition to
its
unusual engineering and
economic considerations, this project demonstrates, on a grand scale, the unavoidable
and often conflicting interrelationships among levels of government, business
The Occoquan watershed
the general public, and environmental protection.
is
the second case study.
It
illustrates the
importance of land-use planning and water
quality monitoring in controlling eutrophication in a large water
examples of problems
in
interests,
in Virginia
impoundment. Further
water resource management are provided
at the
end of the
chapter.
10.2
WATER RESOURCES MANAGEMENT
10.2.1 Importance of Water
Water resources have been
critical to
human
east to
Mesopotamia (modern-day
society since people discovered that food
The
could be produced by cultivating plants.
cities
and towns
that arose
from Egypt
3500
Iraq) following the agricultural revolution about
B.C. required a ready supply of water for domestic as well as agricultural needs.
Even-
tually,
running water drove machines that cut wood, milled grain, and provided motive
power
for
many
made it ideal as a universal
manner of waste from human activities. Unproviding water, for whatever purpose, was simple: either lo-
industrial processes.
solvent for cleaning and flushing
til
recently the approach to
cate close to water, as
was
required.
many
Water's abundance
all
cities did, or store
and transport the water
to
wherever
it
After use, water was generally discharged to the nearest body of water,
often the source from which
was one of
away
it
the foundations of
came.
modern
The low-cost supply of
large quantities of water
society.
Exponentially growing population and industrial expansion primed the need for
increased water supply and distribution.
polluted sources.
This need was met by constructing dams, res-
and aqueducts to bring water from more
ervoirs, river diversions, pipelines,
The widespread
application of
abundant water for unrestricted municipal,
modern technology
industrial,
distant, un-
to the supply of
and agricultural uses, with no
in-
centive for reuse or conservation, has greatly increased the competition for limited
sources of easily accessible water.
mining or agricultural purposes
—
Activities
—such
as
huge withdrawals of water for
that formerly did not affect other
sometimes impinge directly on municipal water supplies for
distant.
In addition to the technical
environmental concerns to be
cities
water users,
now
hundreds of miles
problems of meeting water needs, there are growing
satisfied.
Concerns about the long-term
effects of water
use and the loss of water for aesthetic and recreational purposes are often in conflict
with the objective of providing and maintaining a low-cost water supply.
339
Water Resources Management
Sec. 10.2
10.2.2 Need for Control
The obvious
have on each other
effect that various water users
The
water for themselves and for other users.
is
to create a shortage
less obvious, indirect effects of
of
water use
include those caused by pollution from waste disposal and surface runoff, changes in
aquatic
life,
and increasing stream
ticides,
and
fertilizers
For example, the runoff of herbicides, pes-
salinity.
from cultivated lands may affect the aquatic food chain
ciently to cause the loss of local sport fishing, or encourage the explosive
unsightly algae, which
The
ers.
changes
in
in
turn
may
foul water supplies for municipal and industrial us-
practices
needed
to
land-use practice that
may be
difficult
agricultural
or system of interactions
lems encountered
in
among water
halt
impact would require
negative
this
and costly
difficult
This network
to enforce.
users characterizes the complexity of the prob-
attempting to reconcile
many
uses for the
same supply of
With the diversity of needs and the interrelated effects of water use,
how
suffi-
growth of
is
it
water.
not hard to see
questions concerning the legal right to water of a certain quality can arise.
In the past,
riparian rights, that
is,
the rights of those "on the river bank," dealt
with the quantity of water that a person could rightfully claim because of private ownership of abutting land.
The emerging awareness of water
which others besides riparian owners have
resource to
Failure to resolve the difficult legal, economic, and so-
these laws regarding water use.
cial
common
as a
rights has highlighted the inadequacies of
issues raised by the interactions of multiple water use can lead to serious conse-
Those having
quences.
the rights to large
volumes of water
unreasonably low or
at
subsidized prices will tend to use excessive amounts, with no incentive to conserve wa-
This wastefulness penalizes those having to pay a
ter or to restore its quality after use.
higher price for possibly inferior-quality water, places an additional burden on taxpayers,
and
limits the availability of water for future
tions of watersheds often cross national
development.
The geographic
loca-
and jurisdictional boundaries, complicating the
application of policies that try to regulate water use.
Politicians
tive
and other policymakers must recognize the limitations posed by
human understanding of
volved
in
the
complex physical,
managing water resources.
and many other specialists are
all
biological,
intimately involved in researching and predicting
Each approaches the problem with a
mathematical description or model for understanding the various
A
in-
Engineers, biologists, sociologists, geographers,
aspects of water resource management.
viewpoint.
intui-
and social processes
ships of a water resource system on a quantitative basis
is
all
different
relation-
normally necessary, one
that
allows for the complexity of interaction between parts of the system without requiring
an impractical amount of precise data.
dams
accomplish
efits
Once
this is
done, proposed projects such as
or aqueducts can be judged on the basis of their predicted benefits and costs.
we need somehow
this,
to quantify the direct
derived from water use by various parts of society.
That
is,
such things as aesthetic enjoyment, recreational use, and quality of
at least
common
providing them,
aware
that the
quantifiable terms
in the
same way
in
that
To
and indirect noneconomic ben-
we need
life in
to express
economic or
order to compare these benefits with the cost of
we do
with economic benefits.
average price for water charged by public
utilities
We
is
should also be
probably
set
by
340
Water Resources
precedent from historically low charges and
may
not represent
its
Chapter 10
true market value.
True market value would recognize not just the cost of delivering the water, but also the
subsequent cost of recovering
it,
restoring
The various options possible
its
different groups of water users unequally.
voirs
— whether they
scheme
reation
—can
quality,
and returning
Major projects such
are part of a water supply, flood control,
many
serve
it
purposes, not
all
as
is
usually needed.
Sound
a political nature.
many
Consequently,
dams and
reser-
power generation, or
of which are compatible.
the large expenditures and long-term environmental impacts involved,
port
for reuse.
development of water resources may benefit
in the
rec-
Because of
government sup-
of the key decisions in such projects are of
policies for such water resource developments require the par-
ticipation not only of proponents of the
development and
specialists, but of
an informed
public as well.
10.2.3 Objectives
Water resources
Water Resources Management
in
seldom
in nature
exist
when and where
they are needed.
Erosion,
flooding, and drought also affect the availability and quality of water for use and result
of property each year and, in the case of flood and drought, loss of
in loss
tions,
human
life
Yet properly harnessed to correct these shortcomings and reduce these fluctua-
as well.
water resources can attract regional industry and provide recreational
gether with a myriad of direct and indirect benefits that result.
management
facilities, to-
Sound water resources
requires not only control of the flow of water, but also an understanding of
The
the need for coexistence of all types of water users within a particular watershed.
management
general objective of water resources
is
therefore to
obtained from the utilization and control of water resources.
objectives,
and the
maximize
Projects
the benefits
may have
several
importance of each must be established. This evaluation will
relative
be influenced by the amount of water to be supplied or controlled, the need for protection or
improvement of
its
quality,
and the cost of providing the potential benefits
to the
various users.
One of
agement
is
the earliest
examples of
this
the network of hydroelectric
Tennessee River valley
in the
that the entire country
was
comprehensive
dams and water
United States before World
in the
style of water resource
man-
control structures built in the
War
II.
In addition to the fact
midst of an economic depression, the people of
this
region had suffered greatly from floods that displaced thousands of residents and eroded
arable land that had been stripped of vegetation
ing practices.
velopment
in
Reformed land
practices and improved
vent the silting up of
couraged industry
in the
by uncontrolled logging and strip-min-
The Tennessee Valley Authority (TVA) was created to oversee
a fashion that would benefit public, as opposed to private,
dam
methods of
irrigation
were also
river deinterests.
initiated to pre-
The availability of inexpensive electric power enThe ensuing dramatic increase in the quality of life
structures.
to locate nearby.
region demonstrated the validity of the concept of unified river planning and re-
mains today a prime example of progressive water resource management.
Proper water resource planning techniques depend on adequate data.
tant is
Also impor-
an understanding of the agencies involved, their areas of jurisdiction, and the leg-
Sec. 10.3
Economic and
governs them.
islation that
engineering decisions
these factors
10.3
341
Technological Considerations
is
political considerations are as significant as
water resources management.
in successful
Accordingly, each of
a part of the decision-making process.
TECHNOLOGICAL CONSIDERATIONS
10.3.1 Properties of Water
Water
is
the
most abundant chemical component within the biosphere.
Almost
haps the most important.
medium
the basic
on
all life
earth, including
human
The removal and
of metabolic functioning.
also per-
is
It
life,
uses water as
dilution of
most natural
and human-made wastes are also accomplished almost entirely by water.
In addition,
water possesses several unique physical properties that are directly responsible for the
evolution of our environment and the
functions within
life that
(thermal conductivity) and store (heat capacity) heat
J (1
calorie) to raise the temperature of
raise the temperature of
evaporate
Its ability to
it.
unmatched by
that of
Water also has an extremely high heat of evaporation: while
substance.
0.239
is
1
pound of water
1
gram of
1
°F),
takes
it
540 times
Freezing of water releases 335 kJ/kg (144 Btu/lb).
it.
energy removes roughly 1230
km 3
as
age of energy
sible
in the
for driving
sun
moderates our climate (discussed
Example
Chapter
7).
joules and energy-equivalent barrels of
oil,
in detail in
Btu to
this
rivers,
The
water, and atmospheric water vapor
weather engine that redistributes
1
to
Every day the sun's
(300 mi 3 ) of water from the seas, lakes,
warms bodies of
the global
takes only
much energy
through evaporation and from plants by transpiration (Miller, 1992).
soil
it
1°C (or
liquid water
conduct
any other
and
vast storis
respon-
solar energy
and
10.1
Calculate
in
daily to evaporate water
from the surface of the
yields approximately 6.7 x
10 9
J
(6.4 x
earth.
the
One
10 6 Btu).
Solution
Amount
of water evaporated daily
=
1250
km 3
=
1250
km x
=
(300 mi')
10"
1
1250 x
l()
12
m
km
3
x
1000 L
3
L(3.3 x 10 l4
gal)
Solar energy used daily to evaporate water
=
=
1250 x 10 12 kg x 540 x ±£ZJ.
kg
1.61
x 10 20
J (1.52
x
l()
17
Btu)
amount of
solar energy used
barrel of oil (42 gal or 159 L)
342
Water Resources
Daily solar energy input in equivalent barrels of
Comment: Using
=
1.61
=
24
x 10
20
x 10
J/6.7
the information in Chapter 3,
the daily
world use of
Water
is
fact that
it
bottom up,
killing
J/barrel
we can show
that the solar
energy used to
over 4000 times greater than the energy
is
life
protected from sudden temperature
is
takes a great deal of heat to raise the temperature of water.
one of only two substances
liquid than as a solid.
evaporate water
oil.
The water environment of aquatic
changes by the
9
billion barrels of oil
evaporate water from the global water surface
consumed by
oil to
Chapter 10
If the
— mercury being
the other
—
most aquatic
life
is more dense as a
would freeze from the
that
reverse were true, lakes and rivers
within them.
Solar energy drives vast amounts of water through the ecosphere in a closed sys-
tem known
6-10)
in
as the hydrologic cycle.
This cycle was discussed in Chapter 6 (Figure
connection with mass balances and again
The
lates to global climate.
in
Chapter 7 (Figure 7-10) as
latter figure depicts, in a simplified
Rain falling on land
subsurface sources of water are derived.
how
way,
fills
soil
it
re-
surface and
pores in
much
same way that water saturates a sponge. If the rate of rainfall exceeds the speed at
which water can percolate downward through the soil, the water forms puddles and rivulets which eventually contribute to the surface runoff of streams and rivers, shaping our
topography by erosion. Figure 10-1 shows how water eventually starts flowing horizontally as soil pores and rock cracks are filled.
The boundary formed, called the water
table, may be found just below the ground surface in areas of heavier rainfall to hunthe
dreds of meters
down
in
Wells, drilled in these combinations of water,
dry areas.
and
rock structures, called aquifers,
and
rural areas
soil,
form a major source of water for municipalities
where surface supplies would be too costly
to develop.
10.3.2 Annual Precipitation
Although we
refer to rivers
and wells as sources of water, these,
replenishment on precipitation
cipitation
shows
form of
rain, sleet, or
the
mean annual
distribution of precipitation in
for their
The amount of
related.
Canada and
pre-
Figure 10-2
the conterminous
Locations of equal annual precipitation are joined by lines called isop-
Isopleths indicate lows of less than
250
mm
on the east coast of the continent
to
2500
(10
in.)
Canada
the arid southwestern United States and northern
in.)
depend
in fact,
snow.
and the quantity of water available are therefore closely
United States.
leths.
in the
mm
(100
of precipitation per year in
from 1500 mm (60
humid regions of the
to highs
in.) in
the
west coast.
Values for annual precipitation are of
ties,
little
direct use in estimating water quanti-
but they do indicate what regions are likely to be short of water and therefore arid,
and what areas probably have more abundant water supplies.
Table 10-1 provides
formation on annual precipitation for selected locations
world.
tribution of rainfall throughout the
world
is
in the
The uneven
evident from these figures.
in-
dis-
Arid locations
Sec. 10.3
343
Technological Considerations
Evaporation
30%
Transpiration
40%
Freshwater
Supply 30%
Aquifer
Figure 10-1
Hydrologic cycle. Source:
such as Los Angeles and Las Vegas
in the
McGauhey
(
1968).
in Egypt are at one
Colombia and Cherrapunji in India are
United States and Cairo
extreme, and wet areas such as Buena Vista
in
at the other.
10.3.3 Quantity of Water Available
As
indicated in Figure
1.36 x 10
IX
m
3
10-3, water in
all
forms constitutes a fixed supply of about
(360 billion billion gallons) (van der Leeden
nomical sum makes
it
hard to understand
why
et al.,
shortages exist.
consider the water actually available for use, the amount
is
1990).
This astro-
However, when we
reduced drastically. Approx-
344
Water Resources
Chapter 10
8
«af<^
o
1000
1250
Figure 10-2
Source:
Annual precipitation
Adapted
from
Environment Service
(1899-1938).
Canada,
(1941-1970);
in
millimeters for
Department
U.S.
of
Canada and
Fisheries
Department
and
the conterminous United States.
the
of Agriculture,
Environment.
Soil
Atmospheric
Conservation
Service
Sec. 10.3
345
Technological Considerations
TABLE
10-1
ANNUAL PRECIPITATION
IN THE WORLD
FOR SELECTED LOCATIONS
Country
Canada
Location
Vancouver. B.C.
in.
year
1,460
57.4
Calgary. Alta
425
16.7
Toronto, Ont.
820
32.2
Montreal.
P.Q.
Halifax, N.S.
United States
mm
year
Seattle.
WA
CA
NV
Los Angeles.
Las Vegas,
Chicago, IL
New
New
Orleans,
York,
LA
NY
Miami, FL
1,035
40/8
1,415
55.7
985
38.8
375
14.8
95
4.2
845
33.3
1,515
59.7
1,120
44.1
1,465
57.6
585
23.0
Mexico
Mexico City
Costa Rica
San Jose
1,800
70.8
Bahamas
Nassau
1,180
46.4
Argentina
Buenos Aires
Bra/il
Rio de Janeiro
Chile
Santiago
Columbia
Buena
Vista
950
37.4
1.080
42.6
360
14.2
8.690
342.0
Czechoslovakia
Prague
490
19.3
Denmark
Copenhagen
590
23.3
France
Paris
565
22.3
Germany
Berlin
585
23.1
Greece
Athens
400
15.8
Italy
Rome
750
29.5
22.0
Poland
Warsaw
560
Sweden
Stockholm
570
22.4
England
London
580
22.9
Russia
Moscow
Ethiopia
Addis Ababa
Kenya
Morocco
Nigeria
Lagos
South Africa
Sudan
Egypt
Cairo
China
Shanghai
1.145
45.0
Japan
Tokyo
1,565
61.6
Indonesia
Jakarta
1,800
70.8
Singapore
Singapore
2,415
95.0
10,800
425.1
640
25.2
630
24.8
1.235
48.7
Nairobi
960
37.7
Casablanca
405
15.9
1,835
72.3
Capetown
510
20.0
Khartoum
160
6.2
30
1.1
India
Cherrapunji
India
New
Saudi Arabia
Riyadh
80
3.2
Australia
Sidney
1.180
46.5
Source:
van der Leeden
Delhi
et al. (1990).
346
Total
Water Resources
Chapter 10
Water
1.36x10 ,8
m3
Fresh Water
3.8x10 16
Groundwater and
Surface Water
m3
8.4x10 15
All
m3
Accessible
Surface
0.6%
and Groundwater
22%
Accessible Water
=
5x10 13 m 3
(13 x 10
Figure 10-3
imately
is
Water sources as a percentage of
97.2% of
the global water supply
fresh water, but over
75%
of
this is
total supply.
is
found
Unfortunately, over
very accessible, and
we
rely
van der Leeden
Source:
in the oceans.
99%
of
25%
this surface
gal)
et al.
(1990).
The remaining 2.8%
locked up in the polar ice packs,
formations, and the atmosphere, leaving less than
groundwater.
19
soil
and rock
available as surface water and
water and groundwater
is
not
on the approximately 0.6% available (about 0.004% of the
Figure 10-3 shows these relationships diagraamount of water available for use, suppose that the
earth's total water supply is represented by a 4-L (about
-gal) container.
The total
amount of groundwater would be less than 40 mL (1^ oz). After removing that water
which is too deep underground, or too far away, or too polluted, we would have only
one drop left. This drop will still represent about 10 million liters (about 2.6 million
gallons) per person for a world population of 5 billion. The rate at which this seemingly abundant supply of fresh water can be used is limited by the rate at which water
moves through various portions of the hydrologic cycle. The time to replenish (i.e.,
completely replace) water varies from about 2 weeks in the atmosphere to 10 to 100
original quantity) for our water supplies.
matically.
To appreciate
the relative
1
years in lakes, depending on their depth (Miller, 1992).
much of
the total water budget
is
available
on
It
is difficult
a continuous basis.
If
to estimate
we
how
consider only
the water participating annually in the hydrologic cycle, this precipitation (and an equal
amount of evaporation) is estimated at 420,000 km-Vyr, of which 25% falls on the land
(van der Leeden et al., 1990). If 30% of this total amount (see Figure 10-1) were available to the world population of 5 billion, the supply of fresh water in liters per capita
per day would be
347
Technological Considerations
Sec. 10.3
*«*
25%
*w/
30%
x
of
420,000
km 3 /yr x
10 12
L/km3
171nftI/
17.300
L/capita
=
.,
.
day
•
365 days/yr x 5 x \(r people
Even
this
amount represents an
many
unrealistic figure for
areas because of une-
qual distribution oi accessible water, rapidlv rising demand, and the pollution of water
supplies close to urban areas.
These three
capita use to about 35 L/capita
amount comes
enough
many
In
areas
o\'
is
it
to limit present
Of
1).
I
world per
course, only part of this
pre\ iously used water, pure
going through the hydrologic cycle.
world today, more water
the
being withdrawn for use than
is
and relatively
rainfall
Several Middle Eastern nations, Australia, northern
Mexico, and the southwestern United States are
2000 many other
is
These are primarily regions with low
rainfall.
high densities of urban population.
the year
combine
from precipitation; much of
directly
for reuse without
being replaced by
factors
day (see Chapter
•
all
parts of the United States
experiencing water shortages.
By
and Mexico, Russia, China, Poland.
Africa, and parts of India will be suffering from chronic water shortages as well (Miller.
1992).
The seriousness of
this
problem, particularly
tion that
the
1980s would be the
in light
of present efforts by devel-
was indicated by the U.N. declara
International Water Supply and Sanitation Decade.
oping countries to improve their standard of
Although water shortages are a problem
in
living,
both developed and developing countries, the
reasons for these shortages are fundamentally different.
Developed countries have the
technology and water management organization to support a higher standard of living
based on an extremely high rate of water use.
becoming so high
are
even these
that
Their problem
facilities
developed countries, on the other hand, lack the
the water resources within their reach.
has led to severe water shortages in
Question:
Why
is
it
This
is
water withdrawals
that
cannot keep up with the demand.
facilities to
fact,
Less
properly treat and distribute
coupled with burgeoning population,
many developing
countries.
misleading to say: "By the year 2000
we
will run out of
water".'
10.3.4 Water Use
It
is
important to distinguish between consumptive and nonconsumptive water use.
Consumptive water use
that use
is
which renders water unavailable
for further use. ei-
ther because of evaporation, extreme pollution, or seepage underground, until the hydro-
cycle returns
logic
it
as
available (after treatment
cyclic.
tion
(Viessman and
The nonconsumptive use of water
rain.
it'
Hammer
1993).
On
this basis, agriculture,
and percolation of the water used on crops,
water unavailable lor reuse
various water uses
in the
leaves the
water
necessary) tor reuse without going through the hydrologic
in the
world.
United Slates.
and spread over large held areas
age before reaching crop roots.
is
is
because of evapora-
responsible for almost 909?
oi
the
Figure 10—4 shows the relative magnitudes of
Water conducted man) miles
in
open channels
very susceptible to losses bv evaporation and seep-
Water percolating through
reused a few times, because of the increasing load
ol
irrigated fields
dissolved
soil
may only be
salts
it
picks up
348
Water Resources
from
passage through the
its
soil.
Nonconsumptive water
uses,
Chapter 10
on the other hand, leave
water clean enough after purification, by natural or mechanical processes, to be used
again.
Industrial
drawals.
discharged
water
is
and thermoelectric power uses account for about
However,
is
97%
The
is
that about
Water for domestic use makes up about 10% of
70%
of
all
is
technically possible.
water withdrawn
not be
fit
it
is
industrial
or too contaminated by industrial
is
The end
total with-
0.5% of
its
mass,
our
result of
total
returned to the surface water por-
too disruptive of natural systems,
by natural processes. Water shown
partly rejuvenated
of water with-
The remaining volume of
pollutants in municipal wastewater account for less than
tion of the hydrologic cycle where, unless
may
55%
nonconsumptive, because the water before being
consumed by evaporative coolers
and therefore purification for reuse
water use
is
used only once to cool machinery.
either
chemicals to be restored.
drawals.
of this use
it
for direct reuse for recreation or municipal water supply
and
irrigation
without some form of treatment.
0.1%
Surface
Water
80%
Figure 10-4
Water use
Includes water lost
withdrawals
in
in
1990.
in the
United States
conveyances due
to
in
1990.
Source:
is
as being returned in Figure 10 —
Adapted from
USGS
evaporation and seepage, which accounted
for
(1992);
7%
of
all
water
Example
349
Technological Considerations
Sec. 10.3
10.2
California has approximately 8.7 million acres of land under irrigation; however, only
of the water supplied
To
seepage.
is
experimenting with a chemical that
alleviate this problem, researchers are
duces evaporation losses
38%
taken up by the crops, the balance being lost by evaporation and
in irrigation reservoirs
re-
and channels by forming a monomolecular
layer over open bodies of water.
(a)
Assuming
(
1
that
each acre of irrigated land requires 4 acre-
that
=
acre foot
1
acre covered to a depth of
would be saved
in
year
1
if
ft
foot), calculate the
1
of water per year
number of
acre- feet
these chemical methods reduced consumptive losses
by 1%.
(b)
If
maximum
an average family of four persons requires a
of
1
acre-ft/yr, calculate
the size of residential city that could be served with the water saved.
Solution
(a)
= 62%
Current consumptive loss
consumptive losses
8.7 x 10 6 acre
,_
1% x
Water saved by a
of water used.
1%
reduction in
is
x 4 acre
,_
ft
x 0.62
=
_
._,
2.16 x lfP acre-ft/yr
.
yr acre
•
(b)
Population that could be saved by reduction
2.16 x 10 5 acre-ft/yr
1
As
acre
•
ft I
=
in losses is
864,000 people
A people yr
intimated earlier, the reusable character of water resources
national or regional averages of water use misleading.
that individual rates of
flow figures.
is
makes estimates of
Averages erroneously suggest
water use can be added and compared to
total rainfall or river
Also, total water use can exceed the total water budget
returned and serves as a source of supply.
Thus,
in
when used water
estimating total water use in a
drainage basin or region, the water available for reuse and the extent of recycling must
be considered.
Problem:
and confusing.
cisely
Use of the word consumptive
describing water use can be vague
between the different types of water use.
10.3.5 Options for Meeting Water
The growing demand
States and Canada,
plies, to
in
for water has
Demands
caused many countries, including even the United
which together contain about
examine ways
plies for future use.
shown
in
Suggest one or more terms that could be used to distinguish more pre-
in
which
Two major
Figure 10-5.
The
first
30%
of the world's freshwater sup-
essential water can be provided while preserving sup-
approaches can be identified, examples of which are
consists of using large engineering projects to obtain
350
Water Resources
""!
*<r
/
2kP
QUE
Ill
!»
:H5!
Chapter 10
..I
[Bra^S
'
/
Figure 10-5
Options for meeting water demands.
[Photos courtesy of
(a)
Dams
(a
(a) B. J.
Adams and
(b) J.
supply option) that store water
for
G. Henry.]
various purposes, including water supply,
can create problems, such as the excessive algae growth shown here,
reclamation plants (a reuse option) such as the San Jose Creek Plant
County restore polluted water
courses.
for
(b)
in
Water
Los Angeles
such uses as groundwater recharge and watering
of golf
•
.*
351
Technological Considerations
Sec. 10.3
more water from various freshwater systems hefore they discharge to the ocean. This is
supply-type of solution. The second is based on increased water recycling, using
both constructed and natural purification systems before the water is lost by evaporation
a
or returned to the ocean reservoir.
The
10-1.
more
approach
latter
This
is
called a reuse-type of approach, which, in
water as a subcycle of the global hydrologic cycle shown in Figure
effect, recirculates
become more
will
essential as freshwater supplies
become
inaccessible.
Supply options
1.
efits are
control,
Dams and
means of controlling water flow. Their benof stream flow, power generation, flood and drought
reservoirs are the oldest
equalization and control
and recreation.
Problems, however, include
silting
up of reservoirs over time,
greater evaporation losses due to large reservoir areas, and lowering of river delta flows
which allows
in coastal areas,
2.
the intrusion of saltwater.
Large-scale water diversions from one area to another have
serve Los Angeles.
trial
The
come
into greater
major diversion of the Colorado River
in 1931 to
benefits of supplying abundant water for domestic
and indus-
use, notably in California, since the
development are obvious. The disadvantages of these major projects are
their cost,
evaporative losses, and the tendency to cause salt buildup and soil deterioration through
improper drainage of irrigation projects.
3.
Groundwater contains
97%
of
all
plies about 209f of the country's needs.
ter
and can be withdrawn for use
the freshwater in the United States and sup-
It is
usually of higher quality than surface wa-
in areas far
Groundwater withdrawal must be limited
from municipal distribution networks.
to the rate at
which the aquifer is recharged;
amount available and
otherwise, the groundwater table will drop in level, reducing the
increasing the cost of extracting
fairly easily, but
and are thus,
deep reservoirs
in practical
it.
in
Recharging relatively shallow aquifers can be done
dry areas
may
take hundreds of years to recharge
terms, not renewable.
4.
Desalination is receiving more attention as arid countries report success in
some applications. Reverse osmosis (RO), forcing water through a semipermeable
membrane that passes water but traps dissolved salts, is the most practical of several de-
salination methods, including conventional distillation.
atively energy intensive, but they will
RO
units are expensive
become more economical
and
rel-
for water purification as
their use grows.
5.
from time
The use of icebergs
to time.
ing transit, and
6.
as a water supply for dry coastal cities receives attention
Unresolved problems include the environmental
methods
for melting the ice
effects,
melting dur-
and moving the water ashore.
Relocation of the population away from areas that are short of water or are
ready supporting as
many water
users as possible
is
one obvious plan. This option
al-
will
receive greater attention as the cost for water increases and recycling and conservation
have been implemented.
352
Water Resources
Chapter 10
Reuse options
1.
be a
Better treatment to permit
vital
more reuse of waters
that
have become polluted will
When no new
element of future water resource policies.
sources can be tapped,
number of times that water can be reused before its return to the hydrologic
be the only way to meet water demand in the long term, since the total amount
increasing the
cycle will
of available water
2.
is fixed.
Reducing evaporation from water surfaces has the potential of
lowering water consumption
3.
in agriculture, the largest single user
Water conservation techniques could be immediately
freshwater resources.
and shower
fittings,
Even
Most
can save a great deal of water.
fore drastically reduce industrial water needs.
Changes
effective in extending
relatively simple measures, such as installing special faucet
water was designed with abundant water supplies
are technical.
significantly
of water resources.
in social
in
industrial
mind.
equipment
that uses
Efficient design could there-
However, not
all
conservation techniques
and economic attitudes regarding freshwater supply and
distribution can also play an important role in conserving water.
10.3.6 Quantifying Ecological and Social Effects
Water unites physical systems, such as the atmosphere,
tems.
to
It is
also an important factor in
each other by an
intricate
web
human
soil,
and rock, with living sys-
society and affects the
way people
of laws, rights, services, and activities.
relate
The use of
limited supplies of water by any party in society affects other people and other living
This relationship between water users
organisms.
is
sometimes obvious.
For example,
a fisherman's catch will depend on the degree to which proper wastewater treatment
methods are used
effluent.
flow,
may
in
a nearby pulp and paper mill that discharges huge quantities of
Other situations, such as the dependence of an estuarine environment on
not be as obvious.
The
delta area of
San Francisco Bay
its
river
in California has a
marine ecology that supports a large salmon population because of the character of the
food chain, resulting from the delicate balance between the flushing action of freshwater
from the Sacramento River and the landward flow of an underlying layer of seawater.
Reducing the seaward flow of fresh water by diversion projects upstream could upset
this natural
balance enough to endanger the 6-million-pound annual catch of delta area
salmon (Seckler, 1971).
Projects that alter river flow patterns in order to control and supply badly needed
water resources must be planned and executed with a view toward their ecological and
social consequences.
dertaken until
all
This
is
not to say that water resource projects should not be un-
such conflicts are eliminated, just that
before choosing a course of action.
all
factors should be considered
Before a water control structure, such as a dam, can
be designed, precise data must be collected and numerous decisions made.
water will the
capacity?
dam have
When
to retain?
At what
rate will settlement
of
silt
How much
reduce reservoir
should water be released for flood control, stream augmentation, or rec-
reational use? Will undesirable plant
growth be stimulated by the impounded water?
Sec. 10.3
What
is
353
Technological Considerations
the expected benefit of recreational facilities, and
merged by reservoirs affect
dom examined closely until
environment
to
local residents?
because
recently,
how
having land sub-
will
These and many other questions were
it
was assumed
that the capacity
sel-
of the
absorb these changes was sufficient for any projects of a scale that peo-
ple could execute.
Dam
However, from projects such as the Aswan
Egypt, which de-
in
stroyed the country's sardine industry, created downstream erosion, and promoted the
spread of disease,
ious studies in a
models
nomic
otherwise.
that will allow
There
more
is
a need to integrate data from var-
activities, are presently receiving
much
of
Computer
made.
rational decisions to be
that represent, if only approximately, the relationship
that these
sible
we now know
manner
many
natural and eco-
attention for three reasons.
The
first is
models, although they have limitations, can be run quickly to assess the pos-
cumulative effects that long-and short-term variations in river characteristics can
have on the anticipated benefits of any water control proposal.
Natural and social sub-
systems that affect and are affected by proposed projects can, to the extent that their
re-
The second reason
for
lationships are quantifiable, be
modeled
using modeling involves probability.
as a study tool as well.
Very often key data for design purposes can only
be estimated within certain bounds of probability.
River flow and rainfall records
may
not be adequate to determine the size of facility needed to lower the probability of
flooding to socially acceptable levels.
The complexities of balancing flooding
losses
against construction costs, while taking the probability of flooding occurrences into consideration,
is
a task requiring the use of
sive reason is that the
many
computer models. The
third
and perhaps deci-
diverse considerations and interactions involved in planning
long-term water resource projects are becoming so numerous, and the effects of poor
design so costly, that intuition, unaided by computing assistance in project evaluation,
Figure 10-6
Stewartville generating station,
Canada. Sonne Ontario Hydro.
dam and
reservoir on die
Madawaska River
in
Ontario,
is
354
Water Resources
Computer models, however,
too unreliable.
be beneficial
require careful scrutiny and interpretation to
decision-making process.
in the
Sound data
are the foundation of mathe-
matical models, and although collecting and interpreting this information
consuming,
it
done
essential that this be
is
The dam pictured
Question:
if
10.4
effects has
it
time
Figure 10-6 was built across a river to provide
in
Using a dam for which information
is
available as an example,
outline the beneficial changes (physical, social, and economic) that the
What harmful
may be
decisions supported by numerical results
and informed opponents.
are to withstand the criticism of concerned
hydroelectric power.
Chapter 10
dam
has created.
caused? In each case your answers should be quantified.
PLANNING REQUIREMENTS
10.4.1 Purpose of Planning
In planning, (the process preceding the implementation of a project), objectives are es-
tablished and critically
are evaluated.
Today,
consequences of
examined and
its
means and
the
primary purpose
is
to
results of
implementing the plan
inform those making a decision as to the
Until recently, most water resources planning
their actions.
was
ori-
ented toward providing hydroelectric power and water for industrial, urban, and agricultural
expansion because of the economic benefits involved.
become well aware,
and the
these benefits, are often
loss of water for recreational or aesthetic
enjoyment.
Conflicts between those competing for water have
to the
power of
the
media
However, as the public has
accompanied by environmental degradation
become more
visible, partly
due
inform and provoke response from concerned citizens, and
to
become a
The goals of many strong
inseparable from problems of
partly because water quality has
critical factor
water quantity.
special-interest groups, each with claims to
limited water supplies, are frequently in conflict.
ing "used" water without treatment
may
For example, manufacturers discharg-
impair water quality, which has to be maintained
for recreational uses that support a local tourist industry.
trol,
Pollution abatement, flood con-
land reclamation, and conservation should be considered simultaneously in water
management planning. The challenge
to the planner
is
between competing needs while using water resources
Confusion as
plication of
its
to the
should do
is
most
efficient
compromise
manner.
purpose of planning has caused some resistance to wider apPlanning
techniques.
ceived project, nor does
to find an acceptable
in the
it
imply
is
not the design and implementation of a precon-
state
control of
human
What planning
activities.
provide insights into the problems and alternatives so that
cerned, particularly elected representatives, can
make
all
intelligent decisions.
parties con-
Many
ple believe that planning can be applied as needed to resolve a specific problem.
presumed
that if
enough expertise
course of action will emerge.
This
is
is
employed and
sufficient
unlikely to happen.
an educated look into the future of a dynamic system.
money
peoIt
Water resources planning
Economic,
is
spent, the proper
political, social,
technological factors play a part in both the creation and solution of the problems.
is
and
Un-
certainty
try to
to
355
Planning Requirements
Sec. 10.4
unavoidable
is
in
determining such important parameters as the level of indus-
be served, the timing and magnitude of water flows, and the political commitment
cam
may
Planning studies
out the plan.
be carried out over several years, during
which lime the situation must be constantly reassessed
changing conditions are
10.4.2 Stages
to
the Planning Process
in
Although each planning situation
makes
enough
decisions,
the
unique
is
—depending on
process can be identified.
planning
is
—
there
are
successful plans that a general structure for the planning
Figure 10-7 shows the stages
gested by Environment Canada (1975), that are
common
in the
To
a social process.
Planning
is
it
in the
as an analytical ex-
in essence, a rational process lor
is,
determining the most appropriate course of action under a given
For the discussion following, the stages
situations.
important to realize that
between people
treat the interaction
ercise will produce no meaningful results.
planning process, sug-
many planning
to
following discussion of this planning model,
In the
who
the project, the region,
and the means and consequences of making them
among
similarities
appropriate responses to
if
be made.
of circumstances.
set
planning process have been grouped into
three categories: formulation, evaluation, and adoption.
10.4.3 Formulation of the Study
In
forming a plan, stages la through Id outlined
The need
for planning should be evident
for planning
larly
is
the
with natural
first
s\
in
step in the planning process.
stems such as
Figure 10-7. must be considered.
from Section
rivers, to appreciate
nents of a system can affect other components.
A
Awareness of the need
10.4.1.
frequently difficult, particu-
is
It
how changes
slight
drop
in the
content of the river water, a change in temperature, an alteration
tions of toxic material
less
such
may
set off a
interdependence
is
chain reaction affecting
recognized,
the
full
in
in flow,
many
some compo-
dissolved oxygen
or small addi-
cannot
of planning
benefits
Un-
aquatic species.
be
achieved.
The second
this point that
lect the
problem
step, establishment of a
team of experts who
is
planning group,
is
important because
key assumptions about the effect of the project are made
will
produce the report on the project.
perceived as requiring only engineering specialists when,
in
for
If,
in
fact,
agement, social behavior, and transportation patterns are influenced, these
will be neglected in the plan.
sity
The prime consultant must be able
of expertise necessary to deal with
all
those participating
in
to
it
is
at
order to se-
example, a
land
vital
man-
elements
provide the diver-
or affected by the plan,
including the approving authority, sponsoring agency, beneficiaries, landowners, other
consultants, and public-interest groups.
The objectives set for the study should be clearly understood by all parties so that
subsequent work is directed toward accomplishing only what the study sets out to do.
Setting objectives
is
not an easy task.
lated interests should be
examined
to
The programs of government agencies with
re-
ensure that problems of jurisdiction and duplica-
356
Water Resources
Chapter 10
<
1a
Need
for Planning
should be clearly established
i
b
Planning Group
defines the problem and
selects planning team
c
Objectives
i
to
be
and
clear, practical,
acceptable to those involved
1
Scope
d
defines the responsibilities
of the participants
1
Budgeting
2a
relates the timing of the plan
to the available funds
1
Analysis
b
of the collected data
of the issues
and review
i
c
Alternatives
for meeting the objectives
are considered
1
d
Benefit-cost Analysis
of the economic, physical,
and
social effects
1
3a
Selection
by political decision based
on information available
1
Demonstration
b
pilot or demonstration
project to verify choice
by a
i
c
Adoption
and evaluation of a program
with
revisions as necessary
*
Implementation
to transfer the project
planning to a
from a
management mode
Figure 10-7
process.
Outline of the planning
Source:
Adapted from
Environment Canada. (1975).
tion of effort
planning
sin
357
Planning Requirements
Sec. 10.4
— often
do not occur
One problem
later.
with comprehensive water resource
geographic and hydrologic unit of study
that the logical
is
crosses jurisdictional boundaries of
from the
types,
all
—
the drainage ba-
local to the interna-
Planners must also be aware of the tendency for conflicts between several
tional level.
Attempting to accommodate the wishes of
reasonable points of view.
can cause objectives
to
be
all
water users
high to be practical or too vague to be of use
set too
in eval-
The only method of ensuring that practical goals are
constantly review them in the light of public and private consultation
uating proposals at a later stage.
maintained
ning
curs
of
is
to
In many instances, negative public reaction to planmay be understood and overcome by recognizing the natural apprehension that ocwhen the views of those affected do not seem to be represented. The effectiveness
planning process advances.
as the
all
planning efforts will be improved dramatically
if
each party, whether public, ad-
ministrative, or technical, can identify with the goals of the project
and why these goals
were selected.
Establishing the scope of a planning study
outlines
what
is
expected of each participant.
planning process because
public,
to
it
requires extensive dialogue
it
clearly
also a key element in the
is
among
including the
all parties,
determine the depth of study required by each component discipline to
achieve the stated objectives.
upon
similar to a contract in that
is
This step
At
agencies and advisors
this time, various
may be
called
viewpoints that will set the overall scope of the endeavor.
to present specific
10.4.4 Evaluation of Alternatives and Their Effects
The evaluation of
and costing the planning
set earlier are
from budgeting to analysis, through
alternatives covers the four stages
alternative approaches, to benefit-cost analysis.
Budgeting, that
found to be prohibitively expensive.
This
data synthesis are usually required.
and be governed by the time needed
at certain
a detailed series of time slots
Scheduling
that
not unusual, because the
important because
is
it
ingenuity at
will also
even rudimentary held data.
to gather
govern
Some
data
times of the year, thus requiring a project schedule to be
in
which certain
delay other stages and thereby increase costs.
covered during scheduling
is
Compromise and
need for data almost always exceeds available funds.
can be obtained only
setting schedules
is,
can be a sobering experience when the idealistic goals
effort,
activities
It is
must take precedence or else
also likely that obstacles will be un-
cannot be overcome by
new proposals
or goals.
In this
case the proposal must be reviewed with respect to the time needed for each study, and
new
priorities
and schedules must be drawn up.
Realistic contracts for study can then
be awarded by the prime consultant as required by the planning mandate.
Analysis of the problems requires the collection of pertinent chemical, physical,
social, biological,
must be done
ified
and economic
to gather
and
data.
and discussed with those involved.
tually are will often
Early data will indicate where additional work
refine information so that the
occur even when data collection
not ignore, or appear to ignore,
am
is in its later
may be
been common, may
concerns
Disregarding earnest objections, as has
problems can be further
clar-
Varying perceptions as to what the issues ac-
that
stages.
Planners must
voiced by affected parties.
lead to such strong opposi-
358
tion,
Water Resources
with media support, that the objectives of the original plan are no longer politically
Many
palatable.
studies have failed to be
One Canadian example
ity.
is
implemented because of
the proposed transfer of water
Alberta to ease the shortage of irrigation water in the south.
implemented because of environmental concerns,
efits,
and negative
now been
this lack
from northern
The
of flexibilto southern
project has not been
financial limitations, questionable ben-
political reaction (Smith, 1981).
The generation of
have
Chapter 10
The
alternatives follows the analysis of the data.
issues that
defined are investigated, with a special emphasis on meeting the require-
ments of the participating regulatory agencies.
For example, river flow regulation and
waste discharge schedules would be related because of the pollution problems associated with
the
dumping waste
into rivers with
low flows.
human, physical, and biological systems
that
Alternatives
may
apply to any of
govern water use. The engineering ap-
proach, which looks at permutations of dams, diversions, or other works to effect a cer-
Water management options, for instance, may focus
only one possibility.
tain goal, is
on better control of flooding through regulation of floodplain lands.
natives
spond
that
may
to the abuse of water resources
is,
Institutional alter-
involve the creation or modification of agencies designed to monitor and re-
by one party
implementing a particular scheme
may
proach that
The main
merit study.
at the
expense of another.
small segments over time,
in
point
is
that all the present
proaches should be studied so that no one alternative
is
is
Phasing,
another ap-
and future ap-
favored for lack of information
or consideration of another.
Benefit-cost analysis,
1978),
was
first
used
United States
in the
in the
1930s (Phelps
quite successful in terms of quantifying the tangible
(i.e.,
the
et al.,
economic)
benefits and costs in dollar terms, and choosing, within budgetary limits, the best pro-
posal as the one with the highest benefit/cost ratio.
importance of evaluating competing proposals
sufficient
importance
However, planners now know the
terms of multiple objectives that attach
such as social betterment and natural environmental
to intangibles
quality as well as to tangible
in
economic
factors.
Benefit-cost analysis has been adapted
noneconomic) benefits by using a computer
to include intangible
(i.e.,
technical, biological,
and social relationships involved
(costs)
and output (benefits) can be compared to arrive
economic
benefit/cost ratio.
For
this
in
a project.
at
to simulate the
In this way, input
a ratio similar to the simple
procedure computer simulation has become an
in-
creasingly effective and essential tool for finding the optimal solution of a multiobjective
proposal under specified financial and physical constraints.
Digital
computers are ideally suited
to
modeling the dynamic nature of water
re-
source systems because of their ability to perform quickly the thousands of calculations
needed
to represent the state of the
model during each increment of time. The most
vere limitation of this evaluation method
is
that to permit comparisons, all inputs
outputs must be expressed in economic terms.
Economists and
se-
and
social scientists have
been seeking a means of measuring natural environmental quality and social betterment
ever since the advent of public concern for the inclusion of these intangibles in traditional evaluation procedures.
Monetary techniques have sought
on water-resource-related benefits
ing to pay for
them
in a
in
to place a dollar value
terms of the amount that consumers would be will-
hypothetical free-market economy.
The foremost problem here
359
Planning Requirements
Sec. 10.4
system
that
depends on individual ownership
many
the fact that in past projects
vided
no
at
community
assess these
has been the inability to objectivel)
to set
economic
benefits in an
market values.
Also troublesome
is
recreational and aesthetic facilities have been pro-
cost, thus depressing the
market "value" that can realistically be assigned to
these benefits.
Among
the various
a possible technique.
ways of estimating
In this
the value of intangible benetits. ranking
method, impartial observers are asked to
priate scale, their opinion of the values of different individual
much
the
same way
that students
rate,
and community
out course evaluations in college.
till
is
on an approassets, in
Based on the
relative ranking,
monetary values are assigned to intangible items by relating these to
the benetits with
known
costs.
Evaluation techniques
phisticated in the future.
now
become more
an early stage will undoubtedly
at
However,
if
we
of water resource management, greater citizen understanding and acceptance of
proaches and more public involvement
The following examples
alternatives
new
ap-
process will be necessary.
way how
illustrate in a simplified
the
comparison of two
depending on whether recreational ben-
differ,
included or not.
efits are
Example
A
in the
by cost-benefit analysis can
so-
are to cope effectively with the complexities
10.3
planning authority for a small river basin has proposed two alternatives for a flood-con-
trol
dam. each with an expected
life
of 40 years.
Calculate the benefit/cost ratio for each
alternative, using the following data:
Alternative
A
B
$10,487
$41,950
$18,000
$60,000
$ 2.500
$ 5.000
(with no recreational benefits)
Yearly payment on construction cost
Expected average yearly decrease
in
flood
di
image claims
Yearly maintenance costs
Solution
Altern
A
Total benefits From
[btal costs
of dams
Benefit/cost
Alternative A. which returns $1.37
alternative-
in
dams
$18.IH
itive
B
hi
$60,000
$12,987
$46,950
1.37
1.28
benefits for every dollar spent,
seems
to
be the bettei
360
Water Resources
Example
Chapter 10
10.4
Objections have been raised concerning the fact that recreation was not included
analysis of
this
70%
option
Example
10.3.
One way
to look at prices
is
in
the
of putting a dollar value on the benefits expected from
charged
at
a similar project
which operates for 100 days
at
capacity:
Altern ative
Additional annual budget
(for recreational facilities)
A
Additional yearly payment on construction cost
$3,200
$ 7,100
Additional annual maintenance cost
$6,000
$10,000
Estimated daily park fee/person
$
$
B
1.00
2.00
200
60
Park capacity (people) per day
Solution
Annual recreational
benefits for alternative
Annual recreational benefits
for alternative
A=
B
=
=
70 x 60 x $1.00
70 x 200 x $2.00
4,200
=
28,000
Alterna live
A
B
10.3)
$18,000
$60,000
(see above)
$ 4,200
$28,000
$22,200
$88,000
$12,987
$46,950
Capital
$ 3,200
$ 7.100
Maintenance
$ 6,000
$10,000
$22,187
$64,050
1.00
1.37
Total annual project benefits
From dams (see Example
From recreational facility
Total annual project costs
For dams (see Example 10.3)
For recreational
facility:
Benefit/cost
Alternative B, which returns $1.37 in benefits for every dollar spent,
now seems
to be the
better alternative.
Problem:
Benefit predictions like that
ple 10.4 are usually subject to
tions
wide
variation.
made for recreational facilities in ExamAs a result, most benefit-cost calcula-
include a "sensitivity" analysis to see what effect changes in such things as
interest rates, project costs, or predicted benefits
tio.
In
Example
would have on
the final benefit/cost ra-
10.4 suppose the project were delayed for 5 years and this increased
construction and maintenance costs by
10% and
interest rates
from 4
to
6 1/2% per an-
Sec. 10.5
What
num.
benefits?
361
Legislative Controls
assuming no changes
are the resulting benefit/cost ratios
Could
either project
still
in the
predicted
be justified?
10.4.5 Adoption of a Plan
Progress through the steps outlined in Figure 10-7 will require that
ions be reconciled before an acceptable solution
is
The
found.
many
diverse opin-
selection of the "best"
plan and eventual adoption of a program comprise a political decision in which
factors (e.g.,
economic conditions,
must be considered.
the level of
The planner should
unemployment, other
not choose an alternative;
it
many
priorities, etc.)
is
the prerogative
of the parties that commissioned the study to select from the choices that have been presented.
who perhaps better than anyone recognizes the risk of
dynamic system, must predict the consequences of what-
Nonetheless, the planner,
forecasting the response of a
ever decision
is
made.
Figure 10-7 clearly shows the need for iteration in the planning process.
planning retains the
uncovered,
needed
its
flexibility to
conclusions
examine and redefine
may become
invalid
Usually, one or
for the plan to succeed.
Unless
new information
those whose support
actions as
its
and alienate
more cycles of
is
is
the complete planning
process are required to provide planners and the public alike with the insights necessary
to
make sound
decisions.
Planning does not end with the selection of an alternative.
Rather, the choice
may
be tested by pilot studies leading to possible reevaluation of the program, or the planning process
may move
to the
implementation mode.
during the implementation
is
It
stage that any problems or consequences of changes brought about by the project itself
or any
new developments
Ongoing man-
within the drainage basin will be dealt with.
agement of water resources by constant monitoring and follow-up action
will
be neces-
sary to maintain public confidence in the plan.
10.5 LEGISLATIVE
The primary
CONTROLS
control of water resources
is
accomplished
in
North America and Europe
by institutions and agencies created by governments, both federal and
cial),
under
their
mandate
to serve the public interest.
state (or provin-
Federal institutions such as the
U.S. Power and Resources Service (formerly the Bureau of Reclamation) or the Canadian Inland Waters Directorate, and state or provincial bodies such as the Departments
of Water Resources or Natural Resources, are empowered by government to plan and
control water use.
In specific situations these
other agencies, such as water
tion authorities.
institutions often delegate authority to
management commissions, planning boards, and conserva-
The problem of
jurisdictional confusion, as
nature of water resources, has already been mentioned.
ural reluctance of
many water
authorities
over programs into which they
may have
To
it
this
and planning boards
relates to the pervasive
should be added the nat-
to relinquish their control
invested considerable time and effort.
tions like this are inevitable because legislative
mechanisms now
Situa-
exist for creating
new
362
Water Resources
Chapter 10
planning authorities which, while more closely representing hydrologic boundaries, often give rise to conflict with existing water
management
bodies.
Considerable diplomacy, especially when dealing with international waters,
prerequisite for a successful water planner.
There
is
is
no substitute for knowing how
a
to
frame the planning process within the context of the many agencies that will eventually
This requires a thorough understanding of the existing authorities, the leg-
be involved.
islative tools they use to fulfill their
To describe
ence.
purpose, and the historical reasons for their exist-
the various jurisdictional levels
is
beyond
the scope of this book;
however, a brief outline of the basic institutions and their relationship to one another
some perspective on
will give
their
importance
in
water resource management.
Figure
10-8 indicates the major elements of the North American systems.
In
Canada, the division of authority over water resources between the three levels
—
—
federal, provincial, and municipal
was specified by the British North
American Act (BNA), now incorporated into the Canadian Constitution of 1982. The
federal government has legislative rights over navigable waters, fisheries, waters in na-
of government
tional parks
and federal lands, and waters involving international boundaries.
It
also
shares jurisdiction over irrigation and any other water resource undertakings mutually
agreed upon with the provinces.
The provinces
are constitutionally designated as the
sole proprietors of water resources within their boundaries, with the exceptions just
This grants to the provinces the right to manage, develop, license, and regulate
noted.
water resources for any public purpose by using legislative powers also provided for
the constitution.
Municipalities
come under
in
provincial supervision and are generally
given responsibility for public water supply and wastewater treatment.
Ontario has had
success in organizing municipalities into regional conservation authorities for imple-
menting comprehensive water resource management plans.
The Canada Water Act of 1970 was passed to allow the federal government to work
more closely with provincial water resource authorities to facilitate a more flexible form
of planning and funding of interprovincial and long-term river basin water projects. Under this act, river basin planning boards may be formed when federal and provincial authorities agree that they are needed. These boards are empowered to engage planners to
advise on means for using water resources more efficiently. An extensive program of
monitoring and reporting is encouraged so as to keep all parties informed of work being
done.
In
most of these
projects, water use regulation
is
stated in terms of water quality
rather than quantity (Environment Canada, 1975).
The
ways.
situation in the United States differs
In the
from
that in
Canada
in a
number of
United States, federal powers cover a much broader range of water uses.
Defense, treaty negotiations, taxes, and any projects that advance the good of the
country are
all
legitimate federal activities in water resources.
The
federal govern-
ment, under the U.S. Water Resources Planning Act (1965), can claim three major
roles in water resource development within the country. First, it may, through the Water
Resources Council, formulate and enforce standards and procedures for use by
federal agencies in preparing
state
and
money
and evaluating water resource projects.
interstate river basin
water management programs.
are allocated annually for this purpose, the federal
Second,
it
all
funds
Because large sums of
government can exert con-
u
^
^ =r
n
ra
-JO a
(B
m t
of
g
<
m
rg m
_3
o
ra
u>
0)
c
a;
a E
id
i
r~
c
u
U
ag
CJ
3
en
<
G
•5
£
-J UJ
E
I
p
E <
363
364
Water Resources
siderable influence in determining
what projects
Chapter 10
proceed under what conditions.
will
Third, similar to the function of the Canadian federal government, the U.S federal
government provides for the creation of
commissions
river basin
to coordinate plan-
ning for water resource projects.
arrangements permitted under the Water Resources Plan-
In addition to these three
ning Act, another type of agreement, called a compact,
is
often used
ment
go
beyond
requirements
of
an
water
interstate
system
Under
jurisdictional limitations of individual states.
when
the
the
manage-
financial
and
the compact, in the event of over-
lapping federal and state interests in an area of water resource jurisdiction, the federal
The
needs take precedence.
activities of the state in
water resource management are
primarily arbitration of water rights and distribution of water resources, both surface
water and groundwater, through their power over individual proprietary rights.
ipalities,
dependent on the
states for their authority, generally
Munic-
manage water
supply,
wastewater treatment, and local public works.
Britain and France are both highly oriented toward comprehensive water
ment techniques. As a
result,
and implementation units
water resource policy.
each
is
on
that operate in a
manage-
river basin authorities to serve as planning
manner
that
consistent with government
is
In Britain, the river authorities regulate water
discharge, through the use of fees.
resources
relies
In France, the
management of
all
withdrawal and
aspects of water
aided by the extensive powers that river basin authorities are given.
User
charges are also a key aspect of their regulatory system (Environment Canada, 1975).
Internationally shared water resources have proven to be difficult to
the usual
framework of water resource
jurisdictions.
deal with this problem have had considerably
km
more success
(5530 mi) of border between Canada and the United
in this regard.
mission.
Including
members from both
coordinate and negotiate
tions.
all
Of
the
8900
3900 km (2420
work together. The
States, fully
mi) are over water. This fact led to early recognition of the need to
Boundary Waters Treaty of 1909 authorized
manage under
Institutions created especially to
the creation of the International Joint
countries, this advisory
Com-
body was empowered
to
water resource programs for waters shared by the two na-
Later ratification of the Canada-U.S. Great Lakes Water Quality Agreement of
1972 recognized the immediate importance
that both countries, with large populations
centered around the lower Great Lakes, attached to problems of boundary water pollution.
In the 1987
amendments
tion of persistent, toxic,
to the agreement,
emphasis was placed on the elimina-
and bioaccumulative chemicals by banning or gradually phasing
out (or sunsetting) their production, use, storage, and disposal.
10.6 POLITICAL INFLUENCES
10.6.1 Pressure Groups
Although thorough planning and comprehensive
legislation are essential ingredients for
orderly water resource development, other influences are often
mining what
will ultimately
be
built.
more important
in deter-
Figure 10-8 illustrates the extent to which plan-
Sec. 10.6
niiiLZ
is
365
Political Influences
Equalh important
controlled by other agencies and government bodies.
in the
decision-making process are the special-interest groups, such as environmentalists, taxpayers, business organizations, and public action groups.
These groups, organized
to at-
tract attention to their particular
concerns, solicit political support to oppose or promote
resource development projects.
Few water
lively
among
debate
changes help
The
those
whose often
resource developments
to clarify the issues, but not necessarily to
political process,
however
is
everyone's satisfaction.
based on more than public debate and enumera-
ment opportunities associated with water development
intense political lobbying and contributions to those
On
without
Such ex-
Large business interests are well aware of the increased develop-
tion of preferences.
presented.
now proceed
conflicting interests are involved.
Their views, backed by
projects.
who
support them, are forcefully
the other side, environmentalists pressure politicians to consider noneco-
nomic concerns that are often in conflict with public or private needs for low-cost water.
The public, too. can exert considerable pressure through elected representatives. Conflicts are generallv envisaged as being between big business and environmentalists or
between the public and big government. This notion is fostered by the tendency of the
media
lar
complex
to simplify
issues.
In fact,
it
groups find themselves on opposite sides
frequently happens that segments of simi-
divert water
into the
This project, designed to
southward from the Sacramento and San Joaquin
San Francisco Bay delta
area,
is
discussed
in
delays, which
may
The
last resort,
rivers before they flow
Section 10.8.
Proponents of water resource projects must explore
solv ing objections to proposals.
This was certainly
contentious issues.
in
the case in California in the debate over the Peripheral Canal.
all
possible avenues for re-
court action, leads to lengthy and costly
of course be precisely what those opposed are trying to accomplish.
10.6.2 Management Policies
Of
the factors determining the scope of the
significant.
The
benefits such as
forces are not
a!
work
fact that there is difficulty in
Hood control and environmental
work.
sufficient!) to predict the
is
subsidized.
Table
water will be available
that
and economic policy
is
that
to
economic
Table 10-2 gives some idea
seldom charged.
utilities
Subsidization of water resource facilities
government ensures
probably the most
mean
quality does not
of the prices charged for water delivered by public
North America.
is
It just means that economic relationships are not understood
economic effects of these projects. The true cost of providing,
and treating water
storing, controlling,
to be done, cost
applying traditional economic analysis
is
and water authorities
the chief
when and where
it
is
in
means by which
needed.
Social
therefore reflected by the degree to which water benefits are
10-3
illustrates
how
hydroelectric, municipal, and irrigation water
rates are related to actual project costs attributable to these uses in the Central Valley
Project in California.
The
benefit/cost ratios indicate that water for municipal
droelectric use. costs respectively, about three times and
producing the water.
less than 2592
The
effect of this cost allocation
of the average cost.
is
two times
and hy-
the average cost of
to subsidize farms,
which pay
366
Water Resources
TABLE 10-2 TYPICAL CHARGES FOR WATER
NORTH AMERICA, 1990
Chapter 10
IN
Typical charge (U.S. dollars)
Use
per acre
•
per 1000 gal
ft
per 1000
m
3
Domestic
$400.00-800.00
$1.20-2.40
$320.00-640.00
Industrial
200.00-400.00
0.60-1.20
160.00-320.00
Irrigation
20.00-40.00
0.06-0.12
16.00-32.00
Adapted from Environment Canada (1989);
Hundley (1992).
Source:
AWWA
(1987);
TABLE 10-3 ALLOCATION OF WATER RESOURCE BENEFITS AND COSTS:
CENTRAL VALLEY PROJECT, CALIFORNIA
Project
Unsubsidized
capacity
cost
(%
Participants
Residential, commercial, industrial
(%
use)
Project
costs
(%
share)
Benefit/cost
ratio a
3
10
8.7
Hydroelectric power
34
73
63.5
0.54
Irrigated farms
63
17
14.8
4.26
100
100
Federal government
Benefit/cost
Source:
= %
100
use of project capacity/% share of project costs.
Adapted from Taylor
Example
0.34
13.0
Total
J
share)
(
1
97
p.
1 ,
121).
10.5
Using average values for the typical water charges shown
in
of project capacity shown
what the average charge
would be
users paid the
if all
subsidy, in percent, that
Solution
Assume
Then we have
in
is
Table 10-3, determine
same
rate (neglect the
(a)
1
3%
Table 10-2 and the percent use
to users
government subsidy) and
(b) the
provided for irrigation water by the other users.
a convenient water-use quantity of, say,
100,000 units
(m3
or gal).
the following table:
Costs ($) for share
Unit costs ($)
of:
Water
per
per
Water
use
1000
1000
100,000
100,000
use
%
gal
m3
gal
m
3
3
$480.00
$1.80
1,440.00
$ 5.40
Hydroelectric
34
240.00
0.90
8,160.00
30.60
Irrigation
63
24.00
0.90
1,512.00
5.67
Total
100
11,112.00
41.67
Municipal
$
Sec. 10.6
(a)
367
Political Influences
The average
cost of the water to users
SI
(b)
1
The percent subsidy
1.12 per 1000
is
m =
3
for irrigation water
"
$1
12
$ 24
:1 ,
C
$111.12
-
$0.42 per 1000 gal
is
00
=
x 100
78.4%
1
Two problems
efficient
sources, and
it
program:
exist with California's subsidy
use of water necessary in a state that
has allowed those
who have
it
has not encouraged the
approaching
is
its
limit in
water
large holdings of marginal land to
re-
make
high profits from the use of subsidized irrigation water to raise land values and produce
This transformation of public resources into the private wealth of a few
valuable crops.
large agribusinesses was foreseen and restricted by the National Reclamation Act of
1902.
The
act limited the use of subsidized state
on 65 ha (160 acres) or
less
However,
of land.
who
water resources to owners
resided
1982, intense lobbying by agribusi-
in
ness convinced the California legislature to raise the size limitation to 390 ha (960
by large farming
acres), thereby increasing the subsidy realized
When
interests.
prop-
erty taxes are used to finance part of the cost of a water project, the subsidy to irrigation
water users
is
even greater. This
is
because areas with high assessment and a small pro-
portion of the total water use (urban regions) then pay a disproportionately large share
The
of the costs compared to farms with low property taxes and high water use.
lowing example
Example
illustrates the
fol-
sums of money involved.
10.6
In California, water
tricts" for
is
bought from the federal and
state
water projects by local water "dis-
subsequent distribution to individual water users.
60%
If
of project costs are
charged to general assessment and other sources, with the remainder collected directly from
the users, estimate the effective total public subsidy per acre of irrigated land
requires 4 acreas
shown
in
($24.00/1000
What
ft
Table
m3
Assume
(326,000 gal) per year.
10-3
and
that
the
district
increase in subsidy did an agribusiness with
The yearly charge per
ia«£jt
was
x
J30
acre
1
acre
irrigator
$30.00/acre-
$120.00
acre
960 acres gain when
raised
from 160 acres
the
to
ft
=$120()()
1
landown-
960 acres?
is
/
It
cost to the state to supply irrigation water
so the subsidy
the
acre to farmers for state water used in irrigation
acreyr
The yearly
charges
if
charges are proportioned
).
ership limit specified in the 1902 Reclamation Act
Solution
that the direct
1
x ,77^ x K7R
0.148
0.40
if
users pay 14.8% (Table 10-3)
«winn
= $2027.00
/
per acre/yr
is
$2027.00 - $120.00
=
$1907.00 per acre/yr
is
368
Water Resources
The
960 acres
increase in annual subsidy to an agribusiness with
-
(960
160 acres) x $1907.00/acre
=
in land
Chapter 10
holdings would be
$1,525,600.00 per year
Note: For simplicity, the estimated charges and subsidies to irrigators, as calculated, neglected property taxes.
The
would
cost of water to irrigators
therefore, be increased
by any
water payments based on assessment, and the subsidies shown would be reduced by a similar
amount.
The changes would be
Governments and
relatively small.
their agencies are the only participants in the
development of
water resources that can enforce a long-term outlook on water quality and quantity. The
concern of private water users
return.
Such a view
is
plement water-use policies. The
fact that
government regulatory agencies are
staffed by
servants rather than elected officials enables long-term policies to be established
civil
and decisions based on
10.7
limited to those expenditures that promise a quick
incompatible with the decades often needed to formulate and im-
is
political
expendiency for short-term gains
to be avoided.
FUTURE CHALLENGES
a limited renewable resource.
Fresh water
is
the public,
industry,
assumed an
infinite
ity
rising
demand
for clean, safe water
that
past practices,
supply of inexpensive water, can no longer continue.
Human
has affected the quantity and quality of every body of water on earth.
beneficial use of water will
cal,
The
and agriculture has made us aware
economic, and
political
depend on our determination
demand exceeds
now
management
skills is
that
is
we have
social, techni-
many
in many
The opportunity of
reached a point
the readily available supply.
contributing to the prosperity and well-being of
better
employ new
activ-
future
methods of dealing with water resource management. The
reason these techniques are so necessary
areas where water
to
The
by
which
millions of people by developing
an exciting challenge for those
in
water resource develop-
ment.
in the technical aspects of water resource management are
Our comprehension of the hydrologic cycle is limited to an understanding of the
major pathways of water movement, and we are still unable to predict with any accu-
Future challenges
many.
racy the quality and quantity of water
at different
points in the cycle.
Hydrologists are
only beginning to examine the complex relationship between rainfall and water runoff
patterns.
From
through porous
extensive field data, geologists are studying the
soil
and rock so
that this information about
be incorporated into water planning schemes.
and many other
that
relate
phenomena will lead
water demands grow,
will eventually
wastewaters.
Meteorologists, limnologists, biologists,
scientists are contributing to our
human beings
to
to
more
the fixed
compel greater
Conservation
is
their
environment.
knowledge about
A
intelligent decisions in
amount of
better
the natural systems
understanding of natural
water resource management.
As
fresh water available for the hydrologic cycle
efforts at recycling
another
movement of water
groundwater behavior can
way
and reuse of municipal and
to utilize limited
industrial
water resources more
effi-
369
Future Challenges
Sec. 10.7
For example, reductions
ciently.
excessive evaporative losses from reservoirs and
in the
aqueducts hy means of surface films and membrane covers are sometimes practical.
rigation by
The "drip"
ridge-and-furrow irrigation method which has been in use for 5000 years.
method developed
By
soil surface.
1950s uses perforated piping installed on or below the
in Israel in the
delivering water directly to the root zone, water losses are reduced
60%
by conventional methods
from the 50
to
estimated
million acres (about
1
Ir-
sprinkling systems reduces the large seepage losses associated with the
lost
1%
of the
to
perhaps 15 to 25%.
Urban water use can also be
tion in the United States.
By
1985, an
were under drip
total irrigated area)
irriga-
curtailed by various means, in-
cluding metering of water services, higher charges for water, increasing unit costs with
increasing quantity, mandatory use of water-saving fixtures, and public education.
means should be
servation by
all
possible
use of water
is
important.
Desalination
is
one of the technological options
is
becoming more and more an economic
water from seawater,
methods employed
steam
made
left
the salt
its
potential use
distillation,
in
is
management
part of water
its
oil-rich Persian
Con-
if efficient
water resources planning that
in
Originally developed to extract pure
reality.
now much
Traditional desalination
broader.
which boiling and subsequent condensation of the
and other impurities behind.
Large energy requirements for heating
the process extremely expensive (up to 10 times the cost of
and limited
policy
most municipal water)
application to countries with abundant energy supplies, particularly the
Gulf nations.
Recent developments
in reverse
osmosis (RO), a
less ex-
pensive process in which pressure forces pure water through a permeable membrane,
leaving organic and inorganic impurities behind, have reduced the costs by over
This has opened up the possibility of using
RO
to purify
many
50%.
types of polluted water,
such as groundwater supplies that have become brackish due to saltwater intrusion or
industrial wastewaters that are
RO
The world's largest
was built to reduce
needed
plant, 72.4
mgd
to
supplement inadequate freshwater supplies.
(million gallons per day), near
the salinity of drainage water
from 3000 mg/L
the water can be returned to the Colorado River for reuse in
By 1990
reverse osmosis accounted for
of about 3500
mgd
(Brandt
et al.,
31%
1993).
of the world's
Desalination
may
to
Yuma, Arizona,
285 mg/L so
Mexico (Applegate,
that
1986).
total desalination capacity,
help to rectify the imbal-
ance between the uneven geographical distribution of freshwater resources and the desire to
develop more land
in
water-scarce areas.
Controversy surrounding water-use developments has affected the planning process greatly.
manded
The exhaustive
investigation and seemingly endless consultations
for water resource projects
challenge to water resource planners
is
alternative proposals, considering the
many economic and noneconomic
projects
must now
fulfill.
planning that includes
vironmental quality.
joyment may,
for
all
The
were unheard of a generation ago.
to develop an acceptable
The methods must allow
method
now
de-
greatest
for evaluating
functions these
a broad interpretation of river basin
aspects of social betterment, economic growth, and natural en-
Balancing these multiple objectives to maximize overall social en-
example, require that one benefit not be optimized or else other
benefits will be lost.
tions of the project
Education of the public
is
essential
if
in specific
choices, trade-offs, and limita-
public preferences are to be
accommodated
in the
370
Water Resources
Planners themselves have been guilty of producing recommendations and
planning.
policies that are far too general to be applied
limited funds available.
failed
its
Planning that
However,
all
factors involved in a project to
and the fluctuating cost of money are making the
inflation
sessment of long-term projects
is
by municipalities and industries having
not implemented, for whatever reason, has
is
Benefit-cost analysis must reduce
purpose.
dollar terms.
tainty
Chapter 10
One way
difficult.
by careful phasing of the work
modifying the project in the future
is
maximum
stages so that
in
as-
planning can alleviate this uncer-
that
flexibility
for
maintained.
The procedures employed by various agencies for evaluating water resource
Whether a standardized approach will develop or is even destill evolving.
projects are
sirable
is
uncertain.
There
no doubt
is
that the
methods
will
become more complicated.
Legislative controls on water use have evolved
from constitutional and
These are sometimes inadequate
contemporary water resource problems
that involve
to deal with
legal precedent.
water diversions, control of water pollution, jurisdictional conflicts, and
The formation of
similar difficulties.
age basin has resolved some, but not
a single authority responsible for an entire drainall,
of the issues.
When
an agency's jurisdiction
crosses political boundaries, whether at the local, national, or international level, contro-
The success of
versy can be expected.
large water resource projects of the future will
depend on close cooperation between the sponsoring agency, elected representatives, the
media, the public, and other participants.
the planners,
who
will
which they must operate. Failure
tures in
Fostering this harmony
is
the responsibility of
have to be completely familiar with the legal and
cripple support for the project
—
may even
it
political struc-
to generate a cooperative attitude
generate strong opposition to
may
its
not just
implemen-
tation.
Economists have had
sources.
difficulty
in
determining equitable charges for water
Unlike most commodities, whose value
is
re-
based on what people are willing to
upon as a free commodity
Governments have reinforced this attitude
pay, water in developed countries at least, has been looked
and. because of
by
abundance, of
its
little
value.
water supply as a device for encouraging development.
their policy of subsidizing
southeast Asia the problem of financing water projects
the people's belief that water
is
a gift
from God and
cost about 10 cents to purify and deliver
homeowner was about
1
is
even more
free to
all.
In
250 gallons of Nile water;
Egypt
In
because of
in
1985,
it
the charge to the
cent.
Determining what people should or would pay for water and
fits
difficult,
based on what they have paid
in the past is not realistic.
its
associated bene-
Perhaps social scientists
involved in water resource problems will be able to suggest a logical basis for levying
Until then, rates will probably continue to be set in conformity with the previous
costs.
inadequate charges.
Better water
management techniques
to replace present inefficient
are urgently needed in developing countries
Why they should do this when
same environmentally damaging
needs of the two worlds are different. In
and hazardous practices.
the developed countries, until recently, pursued the
course
is
not hard to explain.
Certainly, the
developing countries, where an estimated
80%
of
all
quate water supply, the justification for proper water
illness is attributed to an inade-
management should be based
not
371
Case Studies
Sec. 10.8
on aesthetic enjoyment and recreational benefits but on necessary improvements
ter
supply and sanitation to reduce disease and protect public health, while
where possible, stimulating food production and
time,
same
at the
development.
industrial
wa-
in
Clearly,
because of their predicament, developing countries have a greater need for effective water
management than developed nations. Modifying the technological and
modern water resource management techniques to suit differing
aspects of
developing countries
is
necessary for these methods to be useful.
institutional
priorities in
Appropriate technol-
name given to this type of approach.
number of occurrences of contaminated water supplies, water shortages,
and flood damage multiply inexorably in the future, the need for water resource management will become more evident. Like energy, adequate supplies of clean water are
essential to the modern way of life. Our response in the coming years will, to a large
ogy
the
is
As
the
extent,
govern the quality of
not so
much on
economic
10.8
life
for future generations.
Success
in this area will
depend
technological advances as on improvements in our social, political, and
which have lagged
institutions,
behind
far
scientific progress.
CASE STUDIES
Problems
amples
water resource management are seldom as simple as those described
in
Most
to 10.4.
10.1
are
complex and
Two
groups with conflicting objectives.
some of
site specific,
case studies have been selected to illustrate
the difficulties in implementing water resource projects.
eral Canal, typifies the social conflicts that
to increase
Ex-
in
and involve special-interest
The
first,
the Periph-
can arise over water use as a result of trying
The information presented
supply by redirecting surface water flows.
based on reports by Seckler (1971), Phelps
et al.
is
(1978), Baker (1980), and Hundley
The second case study demonstrates how land-use planning was used to solve
in the Occoquan watershed and the importance of water quality
monitoring programs. The following references were used: AWWARF (1991), FCOCP
(1992).
water quality problems
(1982), and Randall et
al.
(1977).
10.8.1 The Peripheral Canal
California covers an area of 41 1,000
km 2
(
100 million acres), stretching about 1500
(900 miles) northward along the Pacific coast from Mexico to Oregon.
exceeds
that
of
United States
in
in
all
but three nations in the world (Hundley, 1992).
agriculture, manufacturing,
every 10 Americans lives
tropolises of
east
in
Its
California leads the
and population (29,760,000
in
One
1990).
California, largely in cities surrounding the coastal
Los Angeles, San Diego, and San Francisco.
The
km
gross product
state is
me-
bordered on the
by the Sierra Nevada mountain range and on the west by the Pacific Ocean and
Most
Coastal Mountains.
winter and spring.
rainfall
However,
the
summer and
the
hub of California's
fall.
One
75%
occurs north of the latitude of San Francisco
of water use
of the major reasons
industrial activity
is in
why
in the
the lower two-thirds of the state in
the
Los Angeles region has become
and one of the
largest metropolitan areas of
372
Water Resources
the nation
is
because of the supply of water
it
receives from the statewide network of
reservoirs and aqueducts that store and transport water
Of
south.
mm
500
the
(2
ft)
Chapter 10
from the humid north
of annual precipitation that
to the arid
on California, approxi-
falls
feet, is used by the state (USGS, 1992). About 68% of
comes from surface supplies, with 32% obtained from groundwater.
Agriculture, which accounts for 81% of fresh water use, has always been an important industry in California. Early settlers found that the soil was very fertile, capable
of growing all types of fruits and vegetables when irrigated. Because of the importance
mately 25%, or 50 million acre
this
of water, institutions and laws governing
use have often been the subject of public
its
During the 1920s and 1930s, farmers
debate.
in the
San Joaquin
valley, following the
lead of San Francisco and Los Angeles, decided that waters from the Sacramento and
San Joaquin
pumping
could be stored and
rivers
stations.
Although the
moved southward by
state legislature
a series of canals and
approved the financing, the Great De-
pression intervened and forced the federal government to take over the Central Valley
The Shasta dam on
Project (CVP).
the
Sacramento River, the Friant dam on the San
Joaquin River, and several aqueducts were then
These works served delta-area
built.
water users as well as Central Valley farmers (see Figure 10-9).
The U.S. Bureau of Reclamation (now the U.S. Water and Power Resources Servwas responsible for administering the CVP, including the enforcement of the 1902
federal Reclamation Act, which limited the size of farms receiving subsidized water to
160 acres (raised to 960 acres in 1982). The demand for more water by the burgeoning
postwar population of Los Angeles and by large agribusinesses seeking to avoid the
1902 act prompted the state to offer to buy the CVP from the federal government. After
ice)
rejecting the price asked
by the federal
authorities, California
proposed damming the
Feather River as a major storage facility for another series of aqueducts stretching
southward.
This scheme, called the State Water Project (SWP), was approved by a nar-
row margin
in
1960 over the objections of people
in the north,
who were becoming
un-
easy about the large reservoirs being constructed for the benefit of southern farmers and
cities.
The California Department of Water Resources (DWR) was created
nonprofit
down
SWP
operation.
to plan the
Today, water releases from the Oroville Reservoir travel
Sacramento-San Joaquin
the Feather River to the
delta,
wash through
the delta,
pumped south
than the delta. In all, 23 dams and
power plants make up the $23 bil-
serving the city of San Francisco and delta-area farmers, and are then
over 400 miles to an elevation
reservoirs, 9 aqueducts,
lion project.
1
km
22 pumping
(3280
Ninety percent of water rights
appropriative, means.
higher
ft)
and 8
stations,
in California are
Appropriative water use
is
gained through legal, or
governed by legislation requiring
such use be "reasonable and beneficial." Riparian uses, although comprising only
of
all
water use
profit regional
in the state, generally take
precedence over appropriative uses.
that
10%
Non-
water distribution agencies known as water districts, of which there are
approximately 1000 scattered throughout the
state,
rights
by contracting for water delivery with the
come
for this water
is
typically
55%
from other sources, although some
by water
districts
exercise their appropriative water
SWP
tolls,
or the federal
25%
CVP.
District in-
by property taxation, and
20%
finance water projects wholly by water
charges, whereas others use only property tax (Phelps et
al.,
1978).
373
Case Studies
Sec. 10.8
^Shasta
Dam
(Federal)'
ta=Redding
^Sacramento
River
Tehama Colusa
Canal (Federal)
(Oroville
Dam (State)
/I Lake Tahoe
^# Sacramento
Hood
Mono
Peripheral Canal
(Proposed)
Lake
Co?
Delta-Mendota Canal
(Federal)
California
c
V
San Joaquin River
Aqueduc.
(State)
Millerton
Friant
Lake
Tinemoha
Dam
Reservoir
ederal)
Fresno^
riant-Kern Cknal
(Federal)
_Los Angeles
Aqueduct
Kern River
/
t-
Bakersfield
Los Angeles
County
-Colorado
River
— Federal Central Valley Project
** State Water Project
H| San
Figure 10-9
The purpose of
the
low water from the north
rate
in
the
Political careers
in
California.
proposed 400-ft-wide, 43-mi-long Peripheral Canal was
to
mid-1960s,
to al-
bypass the delta on the east and south, thus increasing the
of water available tor pumping into the federal
proposed
side,
Major water projects
Diego _
this project
were made and
and lobbying v\as intense.
lost
CVP
and the California SWP.
First
has generated heated controversy ever since.
over the project, alliances were formed on either
374
Water Resources
DWR,
Proponents of the scheme included the California
(MWD)
farmers, the Metropolitan Water district
the
Chapter 10
San Joaquin valley
of southern California (known as the
The DWR insisted that for the SWP to meet
must increase water deliveries from 2.9 million acre
ft to 4.2 million acre ft, 700,000 acre ft of which were expected to be contributed by
the Peripheral Canal. Although 31 water districts have claim to this state water, two of
"Met"), and southern corporate interests.
its
future contract obligations,
them
—
it
•
the Met, serving 12 million people in 131
and a water
ifornia,
Agency
—make
up
district in the
75%
of the demand.
ported the canal project also.
communities throughout southern Cal-
San Joaquin valley known as the Kern County Water
Both of these organizations vigorously sup-
They contended, with
economic and engineerlife were dependent on
the aid of
way
ing studies, that California's continued development and
of
increased water flows from the wilderness area of the northern part of the state.
Water use
Critics of the plan disagreed.
efficient
in California, they argued,
was very
in-
under the present system, which automatically linked water rights to land use.
There was no incentive for a farmer
to use less
water under a state water policy that set
new water by averaging in the cost of earlier, less expensive projects. They
recommended a more realistic pricing schedule, called marginal pricing, to reflect the
actual cost of providing more water by the construction of facilities much costlier than
prices for
Efficient water use
earlier projects (Phelps et al.,1978).
having water
tolls
would also be encouraged by
increased so that property taxes, paid by
all
used water or not, would not be used to subsidize water use.
allow holders of water rights to
sell
landowners whether they
Another proposal was
water to other users willing to pay more for
which would automatically benefit the most
creating a water "market"
to
thus
water
efficient
Other people, not necessarily advocates of the Peripheral Canal, rejected
user.
it,
this idea,
saying that the huge amount of private capital generated by this use of low-cost public
water would result
in
an unacceptable redistribution of wealth within society that would
The efficiency of unregulated groundwaLandowners have traditionally viewed groundwaown unrestricted use. However, depletion of readily available
outweigh the benefits of increased
ter
efficiency.
use also became a topic of debate.
ter as a
resource for their
groundwater has necessitated recharge of aquifers from state-owned surface water supplies.
The
cost of this
borne by
is
ter
taxpayers, who, in effect, subsidize excessive
use and recharge has mounted steadily.
Regional differences created unusual alliances between various water users.
Some
San Joaquin area joined forces with delta area farmers
in op-
large agribusinesses in the
posing the canal.
They were
fall
when
river flows
fearful
that
the canal
would lower freshwater flows
in the
summer
were lower. These lower flows might also be unable
to dilute
through the delta, allowing
and
many
Consequently, pressure for better management of groundwa-
groundwater withdrawals.
salt
water to intrude farther up the channels
municipal wastewaters and salt-laden irrigation runoff enough to avoid environmental
problems.
who in the
SWP, saying
Delta-area farmers,
brought into the delta by the
past refused to pay for high-quality water
that they did not request the project,
now
sought water contracts and water quality legislation to minimize the effect of the Peripheral Canal.
The U.S. Fish and Wildlife Service and
They claimed that
ecologists in opposing the plan.
the
Marine Fisheries Service joined
the sensitive estuarine environment
375
Case Studies
Sec. 10.8
Goldman
of the delta, described by
(1971), would be
harmed by lowered flows of
A
water that presently dilute pollution and carry wastes farther out to sea.
trophication, similar to
Francisco Bay.
among many
more northern
(AWWA,
and federal participation
it
was feared
San
for the delta and
life that
supported,
reduce
to
avoiding water restrictions and en-
The statewide controversy caused
its initial
the U.S.
high estimate of project bene-
once assured, seemed uncertain.
in the project,
turned out, the referendum to build the Peripheral Canal was soundly de-
feated (Proposition 9, June 1982), as
that
rivers, thus
1982).
Water and Power Resources Service
As
Erie,
north of the state were concerned that the Peripheral Canal would
in the
possible diversion of
couraging further waste
fits,
Lake
in
Ecologists predicted a reduction in the variety of
other activities, a valuable fishing industry.
Residents
make
what happened
fresh
degree of eu-
would have required water
was a
districts to
November 1982)
later vote (Proposition 13,
develop a conservation program by 1985.
In
Sacramento-San Joaquin Delta to the farms and
continue to be proposed (and vigorously opposed) in
further attempts to get water around the
cities in the south,
new water
bills
the state legislature.
Because of the prohibitive costs of new, massive water projects, future water
sources planning in California
and economically
state's
A
10%
cutback of
In 1992, the agriculture industry con-
in agricultural
2.5%
to the state's
water use would meet the
urban needs for the next 20 years (Vaux and Howitt, 1984).
Unfortunately, water
conservation programs have not been widely adopted by farms (or cities) except
mandated by water
districts
during the 1987-1991 drought.
water, while for the
Furthermore,
rice
same
much of
In 1991,
growers paid between $22 and $47 per acre
is
used for crops that are
The acreage
ft
for
$233 per acre -ft.
in surplus,
and cotton, yet are eligible for additional government subsidies
price-support programs.
agri-
funded water projects
water, the Metropolitan Water District paid
the subsidized water
when
Massive subsidies for
cultural water that unequally distribute the benefits of publicly
continue to draw criticism.
re-
toward achieving a more equitable
California's water but contributed only about
economy.
billion
to be geared
justifiable distribution of water.
sumed over 80% of
$735
may have
in the
such as
form of
limitation for farms receiving subsidized water
has been effectively ignored by agribusiness (by creating loopholes in the rules), resulting in the concentration of the farming industry.
in
holdings of 1,000 acres or more, and
tion
and income (Hundley, 1992).
10%
About 80% of California farmland
of the farms account for
75%
is
of produc-
Clearly, the circumvention of the acreage limitation
has invalidated two major goals of the Reclamation Act: to promote the family farm and
to prevent large
landowners and speculators from profiting
Water planners, however, are reluctant
a redistribution of water resources to
water are constantly being sought.
example,
supply.
is
to rely solely
at
government expense.
on conservation measures and
meet future demands. Additional sources of fresh
The California Department of Water Resources,
for
considering using "water banking" programs to increase the state's water
Water banking consists of diverting excess Delta flows during high flow periods
(primarily winter runoff) into storage facilities south of the Delta.
Surplus delta flows
average about 3 million acre
ft
but can reach up to 25 million acre
and Barnes, 1991).
in
California have a usable capacity estimated
Aquifers
ft
per year (Arora
at
140 mil-
376
lion acre
age
Chapter 10
Water Resources
(four times the capacity of surface reservoirs), and their use for water stor-
-ft
Unlike surface reservoirs, they do not
increasing.
is
fill
with
or lose large
silt
amounts of water by evaporation. Another source of water that could play a key role in
the future is recycled or reclaimed wastewater, which by the year 2000 could supply up
to
800,000 acre
•
ft
of additional water per year.
Costs for wastewater reclamation aver-
age $500-700/acre-ft (Hundley, 1992). Following the drought of 1989-1991,
seawater desalination was renewed, and despite
its
interest in
($1600 per acre -foot
cost
in 1992),
San Nicolas Island, and Santa
several coastal communities, including Santa Barbara,
Catalina Island, have adopted this approach.
It
evident that the controversy over water resources in California
is
Water laws and institutions are not likely to remain unaffected.
over.
nomic and
social implications raised
doubt be part of
all
by the debate on
future water resource planning
is
from
far
The broad econo
the Peripheral Canal will
in California.
10.8.2 The Occoquan Watershed
About 75% of the 580-mi 2 Occoquan watershed in northern Virginia is undeveloped.
However, the basin is situated near the southern periphery of the Washington, D.C.,
metropolitan area and some areas are experiencing very rapid urban development. The
two
largest subwatersheds,
50% and 29%,
comprise
majority of land use in the
subwatershed
is
Occoquan Creek
Occoquan Creek
largely urban
Fairfax and Prince William.
fore
area
agricultural,
is
Run
to the north,
The
whereas the Bull Run
and contains portions of the rapidly growing counties of
1957 a large
In
dam was
empties into the Potomac River, creating an
it
south and Bull
in the
respectively, of the total basin area (see Figure 10-10).
constructed on the creek just be-
-billion-gallon (4.2
1
1
x 10 7
m
3
)
im-
poundment. The Occoquan reservoir provides roughly half of the water supplied by the
County Water Authority, which serves about 700,000 people, most of whom live
County. The Water Authority's other source, an intake on the Potomac River,
not available during drought years because the Potomac has no large storage im-
Fairfax
in Fairfax
is
poundments.
Occoquan
In the late 1960s, water quality in the
to increasing eutrophication.
reservoir began to deteriorate due
Nuisance algal blooms, deoxygenation of the hypolim-
nion, fish kills, and taste and odor problems
were
becoming common. The excessive
all
loading of algal nutrients into the watershed was seriously affecting the ecosystem as
well as creating higher water treatment costs because of
problems.
In a consultant's report
rus in the reservoir
the
Bull
(SWCB)
was
effluent
Run subwatershed.
in
it
was concluded
from the
Based on
1 1
filter
clogging and disinfection
primary source of phospho-
that the
small sewage treatment plants (STPs) in
that
study,
the
State
Water Control Board
1971 ordered the four counties and the two cities (Fairfax and Manassas) in
the watershed to replace the
signed to remove
99%
1 1
small
STPs with a
The
of influent phosphorus.
quan Watershed Monitoring Laboratory
(OWML)
single regional
SWCB
to
The
Occo-
monitor long-term water quality
trends throughout the basin and to assess the effectiveness of the
reducing the phosphorus input to the reservoir.
advanced STP, de-
also established the
OWML
is
new advanced STP
jointly
in
funded by two
377
Case Studies
Sec. 10.8
/
/
X.
y
FAUQUIER
;'-
COUNTY
,
\\WARRENTON\
^—N
">
i
\
SCALE
IN
KILOMETERS
Watershed Boundary
County Boundary
FAIRFAX
Figure 10-10
Location of the Occoquan, Virginia, watershed.
378
water authorities and the watershed counties and
tered
by a
and therefore,
local university
From
independent third party.
each of the major
tributaries,
cities.
Water Resources
Chapter 10
However, the lab
is
adminis-
in theory, is able to function objectively as
an
a network of automated sampling stations located on
contaminant loadings from various sources are monitored.
Twenty-five water quality parameters are analyzed for each sample; sampling frequency
most parameters
for
either daily or weekly.
is
OWML
Annual reports from the
was
small STPs
regional plant
the
1
1
built,
improve
to
indicated that during the 1970s, before the
new
water quality continued to worsen, despite measures taken
their
phosphorus removal
at
The concentration of
rates.
chlorophyll a, a widely used indicator of eutrophication, frequently exceeded the critical
level of
25
|i
Phosphorus
g/L.
levels
were often observed
be greater than 0.01 mg/L,
to
and the Northern Virginia Planning District Commission began
to
designed to quantify previously unrecorded sources of nutrients
(i.e.,
nonpoint sources).
Those studies revealed
that
in
In
that
urban land uses
one study,
total
runoff pollutant load was used,
stormwater runoff accounted for
90%
and
Not
load, respectively.
85%
of the
total
surprisingly, the level of water quality
ervoir following startup of the advanced
STP
in
field studies
stormwater runoff
measure
special sampling regime to
that
phosphorus loadings.
for a majority of future
conduct
nonpoint sources of phosphorus
and nitrogen were much more significant than once thought and
would account
OWML
Prompted by these observations, the
a level sufficient to induce algal blooms.
1978 was
it
which a
was found
in
phosphorus and nitrogen
improvement
in the res-
less than anticipated.
Realizing that more appropriate watershed protection measures were needed, Fairfax
County began
urban runoff.
to evaluate land-use controls as a
In 1982, the
means of reducing
effectiveness of different combinations of land uses and other best
tices
(BMPs).
BMPs
to prevent or
management prac-
are loosely defined as any structure (such as detention
infiltration trenches) or activity
used
pollution from
county authorized the Occoquan Basin Study to evaluate the
ponds or
(such as street sweeping or public education programs)
reduce nonpoint source pollution.
The county's goal was
to prevent
any further deterioration of Occoquan water quality caused by urban and agricultural
activities within Fairfax
County.
Hydrologic models were used to simulate the level of
phosphorus runoff, delivery of phosphorus
response to the phosphorus loadings.
and reservoir water quality
to the reservoir,
Predictions were then
made of
the water quality
impacts arising from combinations of five different land-use scenarios and three
options.
Based on
made and
1.
later
results
implemented:
Approximately two-thirds of the 100-mi 2 study area
shed
in Fairfax
of 5 acres.
(i.e.,
lot sizes
Allowable non-urban uses include residential, green space, parks, and
that pollutant loading rates are
The
the portion of the water-
County) should be zoned for non-urban use with minimum
possibly agriculture, provided that sufficient agricultural
2.
BMP
from these simulations, two major recommendations were
existing
program of
no greater than those
BMPs
BMPs
are used to ensure
for 5-acre-lot residential use.
should be strengthened to substantially reduce
projected rates of runoff pollution from urban areas.
Results of the water quality
Chapter 10
379
Problems
that the study area contributed only
modeling also indicated
phosphorus load. Therefore,
total
elsewhere
trols
would be
the
in
crucial
it
watershed, particularly
Occoquan water
if
was concluded
The zoning changes and
BMP
in
Although the reservoir
impacts.
the existing
con-
Prince William County,
rural
quality were to be preserved.
requirements implemented by Fairfax County have
been successful in controlling urban development and reducing
ity
17% of
that application of runoff
is still
attendant water qual-
its
considered eutrophic, levels of
all critical
pa-
rameters, including phosphorus, nitrogen, chlorophyll a, and turbidity, have stabilized
The advanced STP, with
and some concentrations have declined.
removal efficiency, has significantly improved water quality
in
Bull
flow conditions, the reason being that prior to construction of the
high phosphorus
its
Run during
base-
advanced STP, waste-
water discharges represented the largest dry weather source of phosphorus loading
the Bull
In 1985. the large-lot
the local
zoning and
BMP
requirements were challenged
in court
by
Homebuilders Association but were upheld (no subsequent appeals have been
Large-lot zoning
filed).
tial
in
Run subwatershed.
is
a serious obstacle to developers because low-density residen-
development cannot economically, support the construction of sanitary sewers.
Fairfax County, the situation
even more
is
poorly suited to septic systems.
The
ings in developments that average
1
restrictive
solution in
many
unit per 5 acres.
because most of the
In
are
soils
cases has been to cluster build-
Clustering units
away from
envi-
ronmentally sensitive areas such as streams and floodplains also helps to create large
buffer zones.
The
BMPs
required for
all
new developments
in Fairfax
clude ponds or detention basins that retain a permanent water surface.
County now
More
in-
innovative
stormwater management such as constructed wetlands are also under conThe long-term success of watershed protection in the Occoquan will depend
willingness and ability of all jurisdictions in the basin to implement similar pol-
approaches
to
sideration.
on the
Actions taken by counties or
lution control programs.
part of the problem.
cities in isolation will solve
only
should also be emphasized that Fairfax County's solution to wa-
It
would not have been possible without a basinwide monitoring
The data provided by the sampling program clarified the relative importance
of nonpoint-source and point-source loadings of phosphorus. As well, by using those
data in water quality models, the planning department was able to predict the impact of
ter quality deterioration
program.
the existing land-use plan
and thereby
justify large-lot
zoning and
stricter
BMP
require-
ments.
PROBLEMS
10.1.
Water has unique properties
versal solvent
and has
difference between
how
its
that are different
from those of any other
liquid.
It
a high heat capacity, high heat of vaporization, a large
boiling and freezing points, and a
these five characteristics are important
in
maximum
our environment.
density
at
is
the uni-
temperature
4 C.
Explain
380
10.2.
Water Resources
Overpumping of freshwater wells
(density
groundwater
this
10.3.
coastal areas can cause the intrusion of salt water
in
According
1.025) into these wells.
to
can
40
rise
1
-ft
drop
Use a sketch
ft.
in the
to explain
phenomenon.
Approximately 100,000 gal of water are used
production of one automobile.
in the
the cost of water for this purpose have to increase to produce a
the $10,000 manufactures's cost of producing a
needed
industrial water rates
to
new
car?
Compare
produce the same increase
Assume
of producing a newspaper.
is
$1.00 per 1000
How
1% change
in
this to the increase in
20-cent publication cost
in the
that the production of a
water and that the cost of industrial water
newspaper requires 200/gal of
gal.
Desalination seems to be the key to unlocking the vast supply of ocean water for our use.
Explain
why
it
unlikely that desalination
is
those of most municipal water supplies
most
10.5.
Masters (1974), for each
table, the saltwater/freshwater interface
much would
10.4.
Chapter 10
common
use of water.
Note
—
—even
if
the costs can be brought
will ever be widely
used
down
that seawater contains 18,000 to
to
world's
in irrigation, the
35,000 mg/L of
salt.
Despite the billions of dollars that have been spent on improvements in flood control
(dams, reservoirs
etc.)
What
decreasing.
over the past 40 years, annual flood damage costs do not seem to be
reasons can you suggest for this anomaly?
Assume
that meterological
conditions have remained constant(see also Section 4.5).
10.6.
Recycling of municipal wastewater
Why
most municipalities.
10.7.
There
is little
doubt
that
think that that will only
is it
not
technically, and sometimes economically,
more commonly used?
is
we will need to increase the efficiency of water use. Some people
come about when a "free market," as opposed to a government-
subsidized, approach to water supply and distribution
and against
this
feasible for
"water market" concept
in
is
which the
adopted.
List the
rights to use water
major points for
would be sold
to
the highest bidder just as mineral or logging rights are sold.
10.8.
In
most cases, individuals withdrawing water from aquifers pay no water charges except
However, high
the expenses involved in pumping.
rates of water extraction
can lower the
water table enough to significantly increase pumping costs for other groundwater users
in
the area. For example, suppose that a farmer with 65 hectares estimates that increasing his
pumping by enough
table to drop
to raise
30 cm/yr.
meter of additional
greater than unity.
annual gross revenues by $200 per hectare will cause the water
If the cost
of
calculate for
lift,
How
this
how
higher rate of pumping for his farm
is
$30 per
long his pumping benefit/cost ratio will remain
long will pumping be profitable
if
he also has to pay a surcharge
covering half of the extra pumping costs, which are increasing
at
a rate of $2.75 per year
per hectare in 20 neighboring farms, each 65 ha in size?
10.9.
What would be
the charges to the three major water users in California
equalized and the
13%
federal subsidy
were removed? Translate
crease or decrease from the present water charges.
Use average
if
the charges were
this into a
figures
percentage
in-
from Table 10-2
for present water costs in each category.
10.10.
Suppose
that the authority for the
water
district in
Example
10.6 decides that the irrigators
100% rather than 40% of the cost of water from federal projects.
(a) How much more would a 65-ha (160-acre) farm have to pay for water yearly?
(b) What would the extra cost be if the total cost of the project were charged to users at
the same rate and the federal subsidy of 13% was not available?
Northern California has an abundance of water during spring snowmelt. Some of this runoff is stored, some causes flooding, but most goes directly to the ocean unused. Southern
should pay
10.11.
California,
which has limited water resources (but the most
shortages throughout
its
history, with the droughts in
voters), has experienced water
1976-1977 and 1989-1991 being two
Chapter 10
381
References
most severe. The Peripheral Canal was one solution (see Section 10.8) for providing
nt the
water to the dry areas
in the
south hut was shelved after rejection by the voters.
Now
businesses are pressing the Governor to reconsider the canal or other alternatives.
environmental advisor
governor, your opinion on
the
to
agri-
As
the
whether the Peripheral Canal
should be reconsidered and your recommendations for a state water policy (short and long
Your memorandum
term) have been requested.
to the
governor should not exceed three
typed pages and should:
•
Consider the needs of the citizens and the continued prosperity of the
•
Outline the assumptions on which your proposal
is
state.
based.
Indicate your views regarding controls (legislative, economic), public involvement, and
•
protection of the rights of water users.
REFERENCES
APPLEGATE,
"World's
R.
RO
Largest
Desalting
Waterworld News
Facility."
2(3),
May-June
(1986): 17-19.
Arora,
S. K..
and BARNES, G. W. "Analysis of Water Banking Projects as Additions to the Cali-
fornia State
Water Project."
ter Resources.
AWWA
In
Water Resources, Planning and Management and Urban Wa-
York: American Society of Civil Engineers, 1991.
(American Water Works Association). "42 Mile Canal
May
stream 16(5),
AWWA
Splits California Electorate."
Main-
(1982): 3-5.
(American Water Works Association). "U.S. Water Rates." Mainstream, September
(1987):
AWWARF
5.
(American Water Works Association Research Foundation). "Effective Watershed Man-
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Baker,
New
jor Surface Water Supplies". Denver.
L. B. "U.S.
Brandt. D. C. Leitner. G. F. and Leitner, W.
Art." In Reverse
tions.
/..
American Water Works Association, 1991.
Aides Tread Water on Peripheral Canal." Sacramento Bee, March
Amjad,
E.
16, 1980.
"Reverse Osmosis Membranes State of the
Osmosis: Membrane Technology Water Chemistry and Industrial Applica(ed.i.
New
York. Van Nostrand Reinhold. 1993.
ENV1RONMEN1 CANADA. Monograph on Comprehensive River Basin Planning. Ottawa: Information
Environmi
Canada. 1975.
m
FCOCP
Canada. Municipal Water Rates
(Fairfax Count)
Canada. Ottawa: Ministry of Supply and Serv-
Office ol Comprehensive Planning).
Fairfax County, Va: Office of
Goldman,
m
1989.
ices.
C. R. "Ecological Implications of
1971. p
Press.
i
v.
ol
V.
Jr.
l
u K2.
Reduced Freshwater flows on
Bay-Delta System." California Water, D. Seckler
Hi ndi
Occoquan Basin Study Summary.
Comprehensive Planning, March
(ed.).
the
San Francisco
Berkeley: University of California
121.
The Curat Hurst: California/is and Winer, I77(>\ 1990s. Berkeley: University
California IVss. 1992.
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Mc(i\i iim.
P.
t<>
If Engineering
Environmental
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o] Watei
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(Junius.
New
Yi.rk,
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Miller, G.
T.
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Living in the Environment. Belmont, Calif.: Wadsworth, 1975; 2nd ed., 1979; 3rd
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Phelps, C. E., Graubard,
Wetzel, B.
Rand Corporation,
Randall,
L. W.,
M.
H., Jaquette, D. L., Lipson, A.
Effective Water
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in California:
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Moore, N.
Y.,
Shisko, R., and
Executive Summary. Santa Monica, Calif.:
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Grizzard,
T.
J.,
and Hoen, R.
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P. S.
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Dream That Won't
"The 160 Acre Law."
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Water Supply and Pollution Control, 5th ed.
New
York:
CHAPTER
11
Water Supply
Gary W. Heinke
11.1
INTRODUCTION
In this chapter
we
deal with issues related to providing the quantity and quality of water
required for society's various needs: the selection of alternative sources of water; the
means of upgrading
the quality of
raw water through treatment methods; and the
trans-
portation and distribution of water, with particular emphasis on public water supplies.
Water
for irrigation, public water supplies,
the source.
Uses of water
that
do not
portation, recreation, and fishing.
and industrial uses must be withdrawn from
withdrawal from the source include transEach of these uses places different constraints on the
entail
quality of water.
Irrigation, by far the largest withdrawal use of water,
in
many
makes
Public water supply refers to safe, clean water for use
tals
in
homes, schools, hospi-
workplaces, commercial and some industrial activities, street cleaning, and
tection.
Water
importance
for drinking, personal hygiene,
to the health
Industry
uct
agriculture possible
areas that could not otherwise support crops.
in the
in
is
fire
pro-
of paramount
and well-being of the society.
relies heavily
component, as
and sanitary purposes
on adequate supplies of water
beverages, or indirectly
to
be used either as a prod-
in controlling the
process of production, as
cooling of heat-generating machines.
383
384
Water Supply
Chapter
1
Transportation by boat has been a practical and convenient means of moving
Water transport remains the most economical
people and products since ancient times.
form of transportation even
age of airplanes, railroads, and automobiles.
in this
Surface
water pollution caused by shipping has become a significant problem, and regulations
have been introduced for
prevention.
its
Recreation occupies a high
priority in terms of the benefits that society realizes
from an unpolluted water source. Swimming and bathing
clean water.
Propagation of
and other aquatic
fish
flora
dependent on
in particular are
and fauna
is
directly affected
by
the pollution of surface waters.
11.2
WATER QUANTITY REQUIREMENTS
Demand
11.2.1 Water
Total water
demand on
demands (from
toilet flushing,
during a stated period.
—from
particular
is
sum of
lawn watering, industrial cooling,
Demand
the individual
all
street
washing,
etc.)
not constant but varies during the day and with the
is
hourly, to daily, to monthly, to yearly.
community
the
is
we measure
Variations decrease as the period over which
season.
creases
system
a municipal water supply
normally specified
in
the
demand
in-
Consequently, water demand in a
terms of average daily
demand,
defined
as follows:
average daily demand
(in
m-Vd
Units are
_
total
community)
or million
water use in
year (volume)
1
365 days (time)
mVd,
or gallons per day (gpd), or million gallons per day
(mgd).
It
is
often convenient to express the rate of
average daily
_
demand
average daily
units here
(capita) per
may be
liters
per person:
demand
midyear population
(per person)
The
demand
community
community
in
in
(11.2)
per person (capita) per day (Lpcd) or gallons per person
day (gped).
Table 11-1 provides information on average daily per capita water consumption
for various uses in North
American
ter-use rates in several cities
cities.
The data represent an average of actual waWide variations from these
and from different references.
average figures occur, depending mainly on the extent of industrial and commercial ac-
and on the climate of the
tivity
'
to
1%
per year
in
the past
such uses as firefighting,
city.
Water consumption has increased
two decades.
street
flushing,
Under
at a rate
of about
the category of "Other" are included
and water
lost
through leakage from pipe
joints.
Within the home,
ter,
toilet flushing
accounting for almost
80%
of
and bathing are the two single
total
domestic use.
largest uses of
wa-
Drinking water and kitchen use
Sec. 11.2
385
Water Quantity Requirements
TABLE
WATER USE
11-1
IN
NORTH AMERICAN
CITIES
Average daily
consumption per person '
Percentage
Lpcd
Use
gpcd
of total use
45
Domestic
300
79
Commercial
[00
26
15
Industrial
[60
44
25
Other
1
TOTAL
Consumption
00
660
1
Source:
15
75
100
small residential communities and large
in
-50%
industrialized cities can vary from
from these
26
+50%,
to
respectively,
quantities.
Adapted from
Steel
McGhee
and
10%
account for about 10%, and the remaining
(1991).
is
for clothes washing, house
and car
cleaning, and garden watering.
Water consumption
America.
In
in other
amount of water used depends on
bility
ried;
developed countries
is
on climate; and on
if
any, of
social
plumbing
in the
results of a survey
ticularly in the business
be
much
by the World Bank
1
is
1-2.
in
The
industrial users;
in general.
1976 on water use
in rural
areas of
In cities of the developing world, par-
and wealthier residential areas, complete water systems are usu-
and water consumption
in
these areas
would be closer
to
figures.
TABLE 11-2 WATER USE
OF THE DEVELOPING
IN
RURAL AREAS
WORD
Average daily water consumption
per person (Lpcd)
Region
Minimum
Maximum
Africa
15
35
Southeast Asia
30
70
Western Pacific
30
95
Eastern Mediterranean
40
85
70
190
35
90
Latin America and
the Caribbean
Normal range
Sonne:
lower.
on the capa-
piped, trucked, or hand car-
home; on the existence of
and economic conditions
the developing world are provided in Table
ally installed,
may
the existence of a public water system;
of that system to deliver water, whether the water
on the extent,
The
generally lower than in North
underdeveloped countries water consumption
World Bank. Village Water Supply, Sector Policy Paper
(Washington. D.C.: World Bank. 1976)
North American
386
Water Supply
Table
1
Chapter 11
1-3 provides water consumption figures for a few selected industries.
dustries requiring large quantities of water often develop their
own
In-
water supply and do
not use process water from the public system.
INDUSTRIAL WATER USE
TABLE 11-3
Water use
Industry/product
18,000/tonne
770/bbl
Paper
160,000/tonne
39,000/ton
Steel
150,000/tonne
35,000/ton
Oil refining
300/kWh
80/kWh
580,000/tonne
140,000/ton
Thermoelectricity
Woolens
Linsley and Franzini (1992); SI conversion by authors.
Source:
Water consumption
in a particular
community
For example, climatic conditions influence
air
conditioning.
status
Gallons/unit
Liters/unit
activities
because of several factors.
will vary
such as lawn watering, bathing, and
Also, water use tends to increase in direct proportion to the economic
and the standard of living of the people served. The extent and type of
industrial
may
also be a
activity
can significantly increase water requirements as well, and price
where water supply
factor in water consumption, particularly
pensive.
Many
is
scarce and therefore ex-
other factors, such as the presence or absence of sewers, water quality,
the pressure in the mains, and control of leakage, also affect water use.
11.2.2
Fluctuations in Water Use
The demands on
son, but also
a water
from day
system vary not only from year
to
day and hour
to hour.
to
year and from season to sea-
An example
of short-term variation
in
demand during summer and winter is shown in Figure 11-1. Note that
during the early hours of summer evenings, a substantial increase in water consumption
may result due to lawn watering. It is common practice to express demand fluctuations as
a fraction of the average daily demand. Records of water demand in similar areas can then
residential water
be analyzed
statistically to yield ratios
TABLE 11-4
Average daily
such as those given
rate
l.O
Summer
1.25
Winter
Source:
Table
DEMAND VARIATIONS
Yearly
Maximum
Maximum
in
0.80
1.2-2.0)
daily rate
1.5 (range.
hourly rate
2.5 (range. 1.5-3.5)
Adapted from Viessman and
Hammer
(
1993).
1
1—4.
387
Water Quantity Requirements
Sec. 11.2
2400
c
=>
Summer Day
Typical
2000
—
1600
c
a3
Q
<5
Q.
1200
oQ.
<D
</)
D
S3
800 -
J
400
-1
rAA
J_
4
12
l_
~>~__\
Winter Day
8
4
12
12
8
Noon
Time
Figure 11-1
and
Hammer
Most community
Residential
water-use
of
Day
Source:
fluctuations.
fire
departments obtain water for
fire
fighting
drant connected to the local water distribution system.
tank trucks or portable
source.
hourly
A
pumps and hoses must
water distribution system
demand
or the
drants in the system.
ing pipe sizes,
maximum
This
pumping
The flow required
Adapted from Viessman
(1993).
fire
is
daily
designed
is
from the nearest
there are
no
fire
fire
hy-
hydrants,
bring water from the nearest water
to
demand, plus
demand
If
provide the larger of the
the fire
demand
to
maximum
any group of hy-
often the governing requirement in establish-
capacity, and reservoir capacity for cities under
to put out or at least contain a fire in an individual
2()(),()()()
people.
group of buildings
can be estimated from an empirical formula recommended by the Insurance Services
Office (1974):
F = 224 CjA
(11.3)
388
Water Supply
F=
C=
where
required
Chapter
1
flow (L/min)
fire
a coefficient that takes into account the type of construction, existence of
automatic sprinklers, and building separation
value
(its
is
for
1.5
wood-
frame construction, 1.0 for ordinary construction, 0.8 for noncombustible
construction, and 0.6 for fire-resistive construction)
A =
building area or floor space
total
The equivalent formula
in the
American Engineering System (AES)
F=
F
where
gpm and A
is in
(m 2 )
is in ft
is
CjA
18
2
.
For residential areas with single- or double-family housing, required
vary from a
minimum
tween buildings
over 30
is
ft),
m
(about 100
ft)
to
gpm) when
the required
fire
flows
the separation distance be-
9600 L/min (about 2500 gpm)
For the normal case of separation distances of 3 to 9
tiguous buildings.
30
of 1800 L/min (about 500
m
for con-
(about 10 to
flow would be between 3600 and 5700 L/min (about 950 to
fire
1500 gpm).
When
quired
fire
a fire occurs, the public water supply system must be able to deliver the re-
flow for 2 to 10
h.
Therefore, sufficient water has to be stored in a reservoir
and additional pumping capacity has
power
be available to accomplish
to
this,
even during
The nature of the buildings to be protected will determine the rate and duration of the required flow. The recommended duration varies from a minimum of 2 h for
fire flows of 9600 L/min (2500 gpm) or less to a maximum of 10 h for major fires.
failure.
Example
11.1
Calculate the water consumption (average daily rate,
rate,
and
flow) of a North
fire
The
100.000 people.
25,000
mine
m
2
(269,100
total floor area
ft
2
Assume
).
daily rate,
maximum
of the largest office building complex
that the coefficient
C
downtown
1.0 for this building,
is
hourly
city of
From Table 11-1, assume
Then
average daily rate
(a)
From Table
1
1
-4,
assume
maximum
=
that the average daily
660 x 100,000
=
consumption of water
is
660
66.0 x 10 6 L/day
that
daily rate
=
hourly rate
=
maximum
1
.5
2.5
x average daily
rate
x average hourly
rate
then
(b)
(c)
is
and deter-
the required capacity of the pipe distribution system.
Solution
Lpcd.
maximum
American mixed industrial-commercial-residential
daily rate
=
1.5
hourly rate
=
2.5 x
maximum
maximum
(d) required
fire
flow
is
x 66 x 10 6
=
99.0 x 10 6 L/day
66 x 10 6
=
165 x 10 6 L/day
=
6.87 x 10 6 L/day
determined using equation (11.3):
F = llACjA = 224(1.0)725.000 =
35.4 x 10 3 L/min
)
(e)
389
Water Quality Requirements
Sec. 11.3
design flow for the pipe distribution network
mum
(
dail)
demand and
—
99.0 x 10 6
1
x
'
day
From
(2)
tire
da>
mm
1.440
maximum
(c),
the
+
A
1
maximum
35.4 x 10' L/min
hourlj rate
=
6.87 x 10
Therefore, the pipe capacity must be 6.87 x
Kxample
the greater of
is
Bow, or (2) the
h
(
I
)
hourly
sum
the
=
68,800
=
104.200 L/min
+
of the maxi-
We
rate.
have
35.400
=
6.25 X 10"
I./h
L/h.
10'' I./h.
1.2
steel
1000 tons of
mill produeing
100.000 people, discussed
from which the
in
city also obtains
per day
steel
Example
The
11.1.
going
to be
built
near the
city
ol
located adjacent to a large river,
Calculate the amount of process water
water supply.
its
is
site is
required by the steel mill daily, and compare this to the city's requirement.
From Table 11-3.
ton of steel requires 35.000 gal of water.
Therefore, the
demand of the steel mill will be 35,000 x 1000 = 35 mgd. Since the average
daily demand of the city was calculated to be 66 x 10" L/day, or 17.4 mgd, the steel mill
will require about twice as much process water as the entire city.
It will obviously construct its own water system.
Solution
daily
11.3
I
water
WATER QUALITY REQUIREMENTS
11.3.1 Water Quality Standards
Water contains
a
\
ariety
dissolved or suspended
chemical, physical, and biological substances that are either
ol
in
chemical components of
From
it.
its
moment
the
surroundings as
ground surfaces, and percolates through the
that react with its physical
be treated before
scopic organisms
is
it
suitable for use.
to
in
(i.e..
Quality
is
Knowing
many
tests
set
by the
needed
the water quality requirements
o\'
termine whether treatment of the raw water
be used to achieve the desired quality.
monitoring treatment processes.
in
water can render
it
Groundwater from limestone areas may be very
may
in
user.
require softening before use.
accordance with the intended use of
usually judged as the degree to
quantity because of the
organisms
industrial processes while being perfectly ad-
hardness) and
chemical, and biological standards
living
For these reasons, water must often
Disease-causing (pathogenic) microorganisms
calcium bicarbonate
water dissolves the
Water also contains
soil.
Water quality requirements are established
the water.
rain,
through the atmosphere, runs over
Water containing certain chemicals or micro-
some
dangerous for human consumption.
high
condenses as
and chemical elements.
may be harmful
equate for others.
it
falls
it
It
which water conforms
is
not as easy to
to physical,
measure as water
to verify that these standards are
each water use
is
required and.
is
if
important
so,
in
being met.
order to de-
what processes arc
Water quality standards are also essential
to
in
390
Water Supply
Water
is
cal properties.
evaluated for quality in terms of
It is
necessary that the
its
Chapter
1
physical, chemical, and microbiologi-
used to analyze the water as regards each of
tests,
these properties, produce consistent results and have universal acceptance, so that
mean-
comparison with water quality standards can be made. Standard Methods for the
Examination of Water and Wastewater (APHA et al. 1992) is a compendium of analytical
ingful
methods followed
lists
United States and Canada to assess water quality.
in the
Table
zation for various contaminants in drinking water.
Chemicals
listed
under the 'Aesthet-
ics" heading are so limited because they cause undesirable taste, odor, or color,
The
(unless in excess) are seldom a threat to health.
in
1-5
1
the allowable limits set by the United States, Canada, and the World Health Organi-
some
areas where treatment
limits suggested
may
and water users have become used to a
is difficult
ular taste or odor. Characteristics under the "health" category are
known
and
be exceeded
to affect
partic-
humans
adversely; exceeding their specified limits can constitute grounds for rejection of the water supply.
U.S.
EPA
for inorganic
standards.
eters
standards for drinking water are continuously being revised and ex-
As of January
panded.
1994, there were 84 primary standards (6 microbiological, 17
chemicals, and 61
Table 15-1
lists all
organic chemicals) and 15 secondary
for synthetic
of the
EPA
primary standards for microbiological param-
and inorganic chemicals and a selection of chemicals from the organic category, as
well as
ments
of the secondary standards (as of January 1994).
all
to the Safe
Drinking Water Act, the
25 new contaminants every three years.
tion control
EPA
is
Under
the 1986
amend-
required to promulgate standards for
Reflecting the current emphasis in water pollu-
on toxic substances, new standards
for drinking water will probably focus
on synthetic organic chemicals and radionuclides.
11.3.2 Physical Characteristics
Tastes, odors, color,
they
and turbidity are controlled
make drinking water
food processing, and
observation.
Color
in
needed
water
is
material, and colored wastes
tures
to reduce
Measurements
as
is
industries.
Color
in
involved could harbor pathogens.
turbidity.
that
is
is
on
by human
found
may
set
in water.
stain fix-
of concentraTurbidity, as
a health concern because the particles
Water with enough suspended clay
bidity units) will be visually turbid.
it
domestic water
done by comparison with a standard
being aesthetically objectionable,
10 to 1,000 units; however,
for these are conducted
to a level barely detectable
caused by minerals such as iron and manganese, organic
from
and dull clothes. Testing
them
tions of a chemical that produces a color similar to that
well
water supplies partly because
Tastes and odors are caused by the presence of volatile
textiles.
chemicals and decomposing organic matter.
the basis of the dilution
in public
unpalatable, but also because of the use of water in beverages,
Surface water sources
may
range
particles (10 turin turbidity
from
possible for very turbid rivers to have 10,000 units of
Turbidity measurements are based on the optical properties of the suspension
cause light to be scattered or absorbed rather than transmitted
through the sample.
in
straight
lines
Results are then compared to those from a standard suspension.
DRINKING WATER STANDARDS
TABLE 11-5
Canada
United States
Contaminant
PRIMARY STANDARDS'
<5
Total coliforms
%
(NHW,
EPA. 1993)
(U.S.
(Health)
0/100
TT b
0.5-1.0
Inorganic chemicals (ng/L)
Antimony
NTU
Asbestos (fibers > 10 urn
7 x
10 6 /L
4
Beryllium
Cadmium
Chromium
5
5
5
100
50
TT b
—
50
4000 c
1500
1500
TT b
10
50
(total)
Copper
Fluoride
Lead
Mercury
2 (inorganic)
Nickel
+
N)
NTU
—
50
—
—
—
25 c
2000
Barium
—
.0
1
—
—
1000
—
6
in length)
NTU
1.0
50 l
Arsenic
1984)
mL
—
TT(SW) b
Legionella, standard plate count, viruses
Turbidity (Nephelometric Turbidity Units)
International
(WHO,
MCL
positive samples
Giardia lamblia
1993)
1
1
100
—
—
10,000
10.000
10.000
Selenium
50
10
Thallium
2
—
—
—
Nitrate
nitrite (as
Selected organic chemicals' (ng/L)
10
1
2
—
Lindane
0.2
4
3
Methoxychlor
40
900
30
Endrin
Toxaphene
—
—
3
70
100 c
50
100(1995)
350(1995)
80 c
100 c
2,4-D
2,4,5-TP
Trihalomethanes
(total)
SECONDARY STANDARDS'Aluminum
0.5-0.20
Chloride
Color
Copper
(Aesthetics)
—
mg/L
250 mg/L
15 color units
15 color units
15 color units
mg/L
1.0
mg/L^
Fluoride
2.0
Foaming agents
mg/L
mg/L
0.05 mg/L
0.5
0.3
Manganese
Odor (Threshold Odor Number)
3
pH
0.3
TON
0.1
Sulfate
250 mg/L
Total dissolved solids
500 mg/L
Zinc
5.0
Maximum Contaminant
1.0
mg/L
mg/L
0.3
0.1
Inoffensive
mg/L
mg/L
—
—
—
mg/L
mg/L
—
—
6.5-8.5
6.5-8.5
500 mg/L
500 mg/L
1000 mg/L
—
mg/L
Silver
mg/L
—
—
—
0.05
6.5-8.5
'U.S. primary standards, called
mg/L
250 mg/L
Noncorrosive
Iron
0.2
250mg/L
1.0
Corrosivity
—
—
—
100
5.0
mg/L
400 mg/L
5.0
mg/L
Levels (MCLs), are enforceable by law.
Standards based on minimum Treatment Technique (TT) requirements or
TT (SW)
for surface waters.
^Under review (U.S.) or interim guideline (Canada).
^Partial
e
list.
MCLs
for 61 synthetic organic chemicals,
U.S. secondary standard, called Secondary
MCLs,
promulgated and 16 "proposed" (U.S. EPA, 1993).
are not enforceable
by the federal government.
391
392
Water Supply
Chapter
1
11.3.3 Chemical Characteristics
The many chemical compounds dissolved
may
be of natural or industrial origin
their
composition and concentration.
water
in
and may be beneficial or harmful depending on
may
For example, small amounts of iron and manganese
mains and
not just cause color; they can
form deposits of ferric hydroxide and manganese oxide in water
equipment. These deposits reduce the capacity of pipes and are
also be oxidized to
industrial
expensive to remove.
Hard waters
amounts of soap
are generally considered to be those waters that require considerable
to
produce a foam or lather and that also produce scale
pipes, heaters, boilers,
Water hardness
materially.
is
in
when carbon dioxide
is
expressed as equivalent milligrams per
driven off by boiling.
carbonate hardness, should be limited where
industrial
not
equipment.
removed by
Sulfates, chlorides,
boiling.
These
salts
in hot
which the temperature of water
The bicarbonates of calcium and magnesium
carbonate.
ates
and other units
and
it
is
liter
water
increased
of calcium
precipitate as insoluble carbon-
This "temporary" hardness, called
causes scale formation
nitrates of
in boilers
and
calcium and magnesium are
cause noncarbonate hardness, sometimes called
"permanent" hardness.
compounds that are products or by-products of chemicals used
(e.g., DDT), can build up to toxic levels in water and living
organisms. Measurement techniques have advanced much further than our ability to establish the relationship between synthetic organic compounds now in use and human
health.
Most governments have set arbitrary limits on the more dangerous of these
chemicals until more complete knowledge in this area is available. The microbiological
Synthetic organic
in agriculture
and industry
characteristics of water are discussed in detail in Chapter 8.
11.4
SOURCES OF WATER
The
quality
and quantity of water from surface water and groundwater, the two main
sources, are influenced by geography, climate, and
normally be used with
little
or no treatment.
needs extensive treatment, particularly
if
lack of groundwater or surface water
may make
it
is
reclamation of treated wastewater necessary.
human
activities.
Groundwater can
Surface water, on the other hand, often
In arid regions of the world, the
polluted.
the desalination of seawater and the
Such treatment
is
costly, but
water of ad-
equate quality for any purpose can be produced.
11.4.1 Groundwater
Groundwater
the soil pores.
known
as
is
water that has percolated downward from the ground surface through
Formations of
soil
and rock
that
have become saturated with water are
groundwater reservoirs, or aquifers. Water
reservoirs by wells.
the speed at
Soil pore size, water viscosity,
which water can move through
soil to
is
normally withdrawn from these
and other factors combine
replenish the well.
to limit
This flux (veloc-
may
ity)
ter
393
Sources of Water
Sec. 11.4
vary from
m/day
1
to
A
m/yr.
1
withdrawal rate as high as
is
groundwater reservoir can only support a wa-
Once
continually supplied by infiltration.
this
flow
exceeded, the water table will begin to drop, causing existing wells to run dry and
quiring expensive deep drilling to locate
may
stretches of productive farms
shows how each category of water use
water
in the
United States.
Note
new
There
wells.
is
growing concern
go
lose irrigation water as wells
is
that vast
Table
dry.
is
re-
1
1-6
apportioned between groundwater and surface
that public
and
water supplies make up only a
rural
small fraction of total water withdrawals, with irrigation and industrial water use each
being one order of magnitude
cause
Most
larger.
rural
water users rely on groundwater be-
can be tapped and used directly right where
it
and
for expensive pipelines
purification.
Figure
1
is
it
needed, eliminating the need
1-2 shows the
total
water use by
source.
TABLE 11-6 WATER WITHDRAWALS
IN
THE UNITED STATES, 1990
Total 3
Source
Ground
United States water use.
1
990
Public supplies
gpd
Surface
km'/yr
water
water
(billions)
20.9
32.3
53.2
38.5
Domestic and commercial
5.8
1.4
5.2
3.7
—
7.2
Rural and livestock
70.5
118.5
Private supplies
Irrigation
3.7
2.7
189.0
136.8
Industry
General
5.5
35.8
41.3
29.9
Other b
3.5
—
169.5
173.0
125.3
(96.0)
(96.0)
(69.5)
109.9
357.5
467.4
338.4
Saline Water
Total withdrawals
(Excluding saline water)
a
l
b
kmVyr
=
0.724 billion gallons per day.
Mining and thermal
Groundwater
its
power generation
electric
Adapted from Gleik (1993).
Source:
restoration,
even
is
not as susceptible to pollution as surface water, but once polluted,
if
possible,
is
difficult
and long term.
and many undesirable substances are removed by the
This
is
why
Much
less treatment
to drinking water standards.
table.
source
and therefore expense
is
may
essential to prevent contamination of the well water
to be avoided.
is
needed
require softening.
monitor when large numbers of wells are
Siting of septic tanks in relation to wells
is
soil particles.
to bring
Well waters though of limited quantity, are
usually of uniform quality and free of turbidity, but
ter quality is difficult to
construction
of
municipalities even those located close to surface waters, prefer wells for a
municipal water supply.
groundwater
Most pathogenic organisms
filtering action
is
critical
if
in use.
GroundwaProper well
and hence the water
pollution of the water
394
Water Supply
Chapter 11
400
500
360 320
>,
400
280 -
"*--.
"*
Total^
.»»•
CO
Q
240
300
Surface Water
Q.
200
c
o
,
———
CD
Q.
*-•
160
g
200 "
£
CD
c 120
o
m
100
80
Ground V teiter
^^
40 -
1950
1955
1960
1965
1970
1975
1985
1980
1990
Year
Figure 11-2
1950-1990
Total water use in the United States by source.
included (100 billion gpd
=
138 km-Vyr.) Source:
Adapted from Solley
Rainwater trickling through industrial and sanitary
(saline water withdrawals not
et al.
can dissolve sub-
landfill sites
stances that pose a serious hazard to local groundwater quality.
with a proper leachate management system as discussed
(1983); Gleik (1993).
This can be prevented
Chapter
in
14.
11.4.2 Surface Water
Si rface waters from rivers and lakes are important sources of public water supplies be-
cause of the high withdrawal rates they can normally sustain.
ing
surface
water
is
that
it
is
open
to
pollution
of
all
One disadvantage
of us-
Contaminants are
kinds.
contributed to lakes and rivers from diverse and intermittent sources, such as industrial
and municipal wastes, runoff from urban and agricultural
Water with variable turbidity and a variety of substances
areas,
and erosion of
soil.
that contribute to the taste,
odor, and color of the water can necessitate extensive treatment.
The problems with algae
as related to water treatment
These problems, together with the additional costs
(
1
)
were mentioned
to control algae at the
source with copper sulfate, (2) for more frequent backwashing of the
extra chlorine or other disinfectant
eutrophication of lakes
that the
is
consumed by
of concern from a water treatment standpoint.
phosphorus
in detergents,
Direct use of rainfall
is
is
9.
and
(3) for the
why
should be evident
our wastewater treatment plants,
economic motivations
in agricultural run-
as well.
a limited but important water source in a few areas that
from fresh water but
ample, rainwater
in
It
and the restrictions on nutrients
off are not just for aesthetic reasons but have their
are remote
Chapter
water supply
the algal organic matter are the reasons
removal of phosphorus and occasionally nitrogen
the limiting of
filters,
in
that receive regular precipitation.
In
Bermuda,
collected on roofs and stored in cisterns for later use.
for ex-
Sec. 11.5
395
Water Treatment Processes
11.4.3 Seawater
Seawater. available in almost unlimited quantities, can be converted into fresh water by
a
number of
However, conversion costs (not including the costs for disposal
processes.
of the masses of
salt
residue generated) are perhaps two to five times higher than those
Desalination
of treating fresh water.
solved salts from water.
is
the general term used for the removal of dis-
Distillation, the oldest desalination technique,
The process
evaporation and condensation of water.
energy to evaporate water
may make
it
is
practical in countries with plentiful sunshine.
Another method, freezing, lowers the water temperature
can be separated from the brine.
ions through cation-permeable or anion-permeable
permeable only
to water;
until ice crystals free
of
salt
Electrodialysis involves forced migration of charged
potential across a cell containing mineralized water.
that are
depends on the
energy intensive, but using solar
membranes by applying an electric
Reverse osmosis uses membranes
however, the driving force
in this
case
is
pressure pro-
This process seems promising because energy costs are well below
vided by pumps.
those for other technologies.
have found wide use
in the
Currently, desalination plants for municipal water supply
Middle East.
Future use will occur
in areas
of extreme
freshwater shortage, particularly for industrial water uses.
11.4.4 Reclaimed Wastewater
Reclaimed wastewater
is
water that has been treated sufficiently for direct reuse
dustry and agriculture and for limited municipal applications.
loop operations
may
Suspended
water.
offer the only alternative in areas that cannot obtain
solids,
biodegradable organics, and bacteria can
sodium,
and calcium,
synthetic
organics
like
enough
fresh
be removed or de-
all
graded by normal wastewater treatment processes, but color, the inorganic
nesium,
in in-
Such recycling or closed-
salts
of mag-
and other toxic
pesticides,
substances must be removed by advanced techniques similar to those used for desalinaActivated carbon
tion.
is
Allowing water
removing many organic pollutants because of
effective in
extremely large surface area (^1000
to cleanse itself
m
2
/g) that
by percolating through
moves impurities from water and has wide application
plies.
in
11.5
the
soil is
in
another technique that re-
recharging groundwater sup-
Currently, the use of reclaimed wastewater as a water source
Middle
East.
its
can trap and adsorb water impurities.
is
practiced mainly
South Africa, and arid parts of the United States.
WATER TREATMENT PROCESSES
11.5.1 Water Treatment Plants
One
of the great achievements of modern technology has been to drastically reduce the
incidence of waterborne diseases such as cholera and typhoid fever.
no longer the great
was
risks to public health that they
once were.
These diseases are
The key
the recognition that contamination of public water supplies by
to this
advance
human wastes was
396
Water Supply
main source of infection and
the
that
treatment and better waste disposal.
1802
United States,
filtration
Poughkeepsie,
New
could be eliminated by more effective water
it
of drinking water was
By
York.
nology of making water
was used
Filtration of drinking water
and by water vendors
in Paisley, Scotland,
Chapter 11
in
London, England,
first
practiced in
In the
1872 by the
city of
improvements
the beginning of this century,
as early as
in 1828.
in the tech-
had become widespread throughout Europe
safe for public use
and North America.
Today's water treatment plants are designed to provide water continuously
meets drinking water standards
in
accomplishing
to be used,
this:
at the tap.
that
There are four main considerations involved
source selection, protection of water quality, treatment methods
Common
and prevention of recontamination.
precautions to prevent ground-
water and surface water pollution include prohibiting the discharge of sanitary and
storm sewers close to the water reservoir, installing fences to prevent pollution from rec-
and
reational uses of water,
restrictions
areas that drain to the reservoir.
on the application of
Instituting regulations that
fertilizers
and pesticides
in
comprehensively deal with
protection of the source can be difficult because several jurisdications, from local to federal,
may be
involved in one project.
Considerable political cooperation
prerequisite to the safe development of
many
main
erations
therefore a
filtration,
and disinfection are
unit operations involved in the treatment of surface water.
Water treatment op-
Screening, coagulation/flocculation. sedimentation,
the
is
large-scale water supplies.
fulfill
one or more of three key
tasks:
removal of particulate substances such
as sand and clay, organic matter, bacteria, and algae; removal of dissolved substances
such as those causing color and hardness; and removal or destruction of pathogenic
bacteria and viruses.
The
actual selection of treatment processes
of
(a) a typical surface
depends on the type
Figure 11-3 shows a schematic outline
of water source and the desired water quality.
water treatment plant, and (b) a groundwater treatment plant.
In
by gravity through an intake structure and pipe, screens remove
the former, water flows
larger items, such as fish, sticks,
and leaves, and
From
the level of the treatment plant.
low-lift
this point on,
pumps
raise
incoming water
to
water moves through the plant by
gravity.
Occasionally, raw water with low turbidity can be treated by plain sedimentation (no
chemicals) to remove larger particles and then
moved
remedy
in a
filtration to
remove
the few particles that
Usually, however, particles in the raw water are too small to be re-
failed to settle out.
reasonably short time through sedimentation and simple
this,
a chemical
loids, into larger ones,
directly in filters.
is
added
which can then be
settled out in sedimentation tanks or
Where sedimentation precedes
filtration, filters
periods, or at higher rates, before they have to be backwashed.
the top of the sedimentation tanks
particles are
removed by
To
filtration alone.
to coagulate/flocculate the small particles, called col-
is
conveyed
straining, settling,
to the filters.
removed
can operate for longer
Clarified water
drawn
off
Any remaining suspended
and adhering to the sand or other
material as the water flows through the small pore openings of the
filter
filtering
bed. Filtration of
chemically coagulated/flocculated water with no prior sedimentation (called direct filtration)
is
effective for waters with
fact the practice in
many of
low
the
to
moderate turbidity
newer water
(5 to
20
treatment plants.
and
is in
filtration
and
turbidity units)
Following
Sec. 11.5
397
Water Treatment Processes
Addition of
Disinfection
Coagulant
(Chlorine)
Through Water
System
to the Customer
Distribution
Intake
Screens I
Structure
*
Sedimentation
1
Lake, River
Low
Pumps
-
or Reservoir
Rapid
Coagulation/
Mixing
Flocculation
lift
Filtration
©
Storage High
-
lift
Pumps
(a)
Disinfection
(Chlorine)
Well
*
Through Water Distribution
System to the Customer
Softening
(and Pumps).
1
o—*!
Storage High
Aeration/
-
lift
Pumps
Sedimentation
for Iron
-
Manganese
Removal
'
When
*
required
(b)
Figure 11-3
Schematic of water treatment plant
using
a
la)
water source,
surface
and
(b)
a
groundwater source.
before
flows into the storage reservoir, the water
it
is
disinfected, usually with chlorine.
may also be added because of its ability to retard tooth decay. Treated water is
pumped by the high-lift pumps into the distribution system to serve customers and to
Fluoride
then
maintain water levels
processed
in
in
storage reservoirs
a water treatment plant
rather than the average daily
is
if
required.
The
rate at
usually based on the
demand, thus reducing
the
which water can be
maximum
daily
demand,
need for large storage capacity and
allowing for shutdown of parts of the plant for maintenance during off-peak hours.
is
It
despite
important to recognize that water treatment
many
There
involved.
made on
scientific
advances
a need
is
for
limited water resources.
in
still
remains somewhat of an
art,
understanding the physical and chemical principles
more research
In the
to
meet the increasing demands being
remainder of
this section
we examine each
unit
operation grouped under the main functions of a water treatment plant.
11.5.2 Removal of Particulate Matter
The
unit operations
employed
for the
removal of particulate matter from water include
screening, sedimentation, coagulation/flocculation. and nitration.
Screening
first
stage
in the
to
remove
large solids such as logs, branches, rags,
treatment of water.
damage pumps and clog
and small
fish is the
Allowing such debris into the treatment plant could
pipes and channels.
For the same reasons, water intakes are
lo-
cated below the surface of the lake or river to exclude floating objects and minimize phys-
398
Water Supply
damage from
ical
ice.
In a lake this intake
is
enough offshore
located far
pollution effects of shore vegetation or waste discharges; in rivers
tected area.
more
or
in.)
pumping
(6-mm
or
1
-in.
These
fine screens are also
wells to exclude larger soil particles which
(1
station at a velocity suf-
Mechanically cleaned bar screens and
pumps
spacing) are placed just ahead of the low-lift
the water to the plant level.
mm
Water then
apart are placed at the intake point to exclude larger objects.
prevent settling of particles in the pipe.
fine screens
minimize the
Coarse screens consisting of vertical bars spaced approximately 25
flows by gravity through the intake pipe to the low-lift
ficient to
to
located in a pro-
is
it
Chapter 11
used
at the
may damage pumps and
that raise
base of groundwater
clog piping.
Sedimentation, the oldest and most widely used form of water and wastewater
remove
treatment, uses gravity settling to
atively simple
particles
from water (see Chapter
and inexpensive and can be implemented
or rectangular.
As noted
earlier,
sedimentation
may
in
6).
rel-
It is
basins that are round, square,
follow coagulation and flocculation
be omitted entirely (with moderately turbid water). Particsurface water can range in size from 10 _l to 1~ 7
in diameter,
(for highly turbid water) or
suspended
ulates
mm
in
the size of fine sand and small clay particles, respectively.
water
is
caused by those particles larger than 10~ 4
mm
10~ 4
contribute to the water's color and taste.
mm,
Turbidity or cloudiness in
while particles smaller than
Such very small
particles
may
be
considered, for treatment purposes, to be dissolved rather than particulate.
Water containing particulate matter flows slowly through a sedimentation tank and
is
thus detained long
clarified
enough
for the larger particles to settle to the
water leaves the tank over a weir
bottom of the tank are removed manually or by mechanical scrapers
to the
charged to a sewer, returned to the water source
ing their treatment and/or removal.
detention time
ticles
is
if
to be dis-
permitted, or stored on the site pend-
Progressively smaller particles are settled out as the
increased by making the tanks larger.
The removal of very small
par-
using plain sedimentation would be impractical because of the high cost of mak-
ing a sedimentation tank large
time
bottom before the
Particles that have settled
at the outlet end.
is
enough
typically 3 h in tanks 3 to 5
tled out in this time
m
to provide the
(10 to 15
must be removed by
Coagulation/flocculation
is
ft)
needed
Detention
settling time.
Particles too small to be set-
deep.
filtration or other
methods.
a chemical-physical procedure
whereby
particles too
small for practical removal by plain sedimentation are destabilized and clustered together for faster settling.
A
suspended
significant percentage of particulates
in
water are
so small that settling to the bottom of a tank would take days or weeks. These colloidal
particles
would never
Coagulation
act
mechanism
is
is
settle
by plain sedimentation.
a chemical process used to destabilize colloidal particles.
not well understood, but the general idea
is
to
The ex-
add a chemical
provides positively charged ions to water containing negatively charged colloids.
resulting reactions reduce the tendency for the colloids to repel each other.
ing for about 30 seconds
is
required to disperse the coagulant.
flocculation, of the suspension
is
that
The
Rapid mix-
Gentle mixing, called
then undertaken to promote particle contact.
This
is
achieved by mechanical mixing through the use of slowly rotating paddles inside the coagulation/flocculation tank, or by hydraulic mixing, which occurs
over and around baffles in the tank.
Detention time
in the
when
flow
is
directed
coagulation/flocculation tank
1
399
Water Treatment Processes
Sec. 11.5
usually between 20 and 40 minutes in tanks 3 to 4 m 10 to 13 ft) deep. Through the
combined chemical-physical process of coagulation/flocculation, the colloidal particles
that would not settle out by plain sedimentation are agglomerated to form larger solids
is
(
These appear
called floe.
as Huffy
small noncoagulated particles
most
common
tion with the
when
growths of irregular shape that are able to entrap
settling
alum
to
may
A
removed.
sulfate (alum)
is
the
also be used alone or in combina-
The Hoc suspension
improve flocculation.
from the coagulation/flocculation tanks
floes are
downward. Aluminum
coagulant but organic polymers
is
gently transferred
to settling tanks or directly to Alters,
where the
cross section of a coagulation/flocculation and settling tank
is
shown in Figure 1-4.
The chemistry of coagulation is complex, but simplified equations can illustrate
the process.
The positively charged cations needed for coagulation of the negatively
charged colloids can be provided by metallic salts, aluminum and iron salts being the
most common.
The coagulation process using filter alum. A1 2 (S0 4 )3 14.3H 2 0, the standard coag1
ulant in water treatment,
1.
The alum
thought to proceed
is
in the
following three stages:
ionizes in the water, producing Al 3+ and
SO^ions. Some of
the Al
,+
ions neutralize the negative charge on the colloids, but
2.
Most of
the Al +3 ions
combine with
OH
ions (from the water) to form colloidal
AI(OH),. which adsorbs positive ions from
A1 2 (S04 ) 3
3.
The
+ 6H 2 0^ 2AI(OHh| + 6H+ + 3S0 4
positively charged
and the excess
is
solution:
AI(OH) 3
2
(11.4)
sol then helps to neutralize the negative colloids,
SOj : to
neutralized by the
produce a precipitate of Al(OH) 3 and
adsorbed sulfates.
Note
that the excess
would stop
cess
H^
H+
ions formed in step 2 tend to depress the pH, which
the formation of the
removed by
ions are
Al(OH),
since
the alkalinity
it
pH
is
(HCO^
dependent.
Normally, the ex-
present in the water according to
)
the equation
6H +
The
\l
-I-
3S0 4
overall reaction,
S0 4
:
+ 3Ca(HC0 3
combining equations
-»
which reveals
ol
thai
CaC03
,
CO
:
.
II
3CaS0 4 + 6CO : t + 6H :
(1 1.4)
and
(
1
1.5)
(
1.5). is
600
2AKOH), + 3CaS0 4 + 6C0 2 +
parts of filter
alum have used up 300
14.3H 2
(
I
1.6)
parts of alkalinity (ex-
as noted in Section 6.3.3).
The overall chemical
some calcium hardness
tion ol
-+
+ 3Ca(HC0 3 ) 2
I4.3H 2
pressed as
)2
effect will be a decrease in the
|( 'ai
I
ICO j
insufficient alkalinity
,
|
is
pH
of the water, a conversion
(CaS0 4
and the produc-
to sulfate
hardness
present
the water lor this reaction to occur.
in
),
o
U
* o
u
V
<s>
f/1
n
Gft
>*
(/)
&0
U —
3
ii
E S
400
be raised by adding lime [Ca(OH) 2 ], soda ash (Na 2 C0 3 ), or lye (NaOH).
pH must
the
The optimum pH
much
401
Water Treatment Processes
Sec. 11.5
additional
for coagulation with
pH
alum
is
about
Coagulation does not require
6.
control, because the introduction of
alum lowers
pH
the
of nor-
mally neutral surface waters to an acceptable value.
not normally possible to achieve adequate clarity of surface water with either
is
It
sedimentation or the combination of coagulant/flocculation and sedimentation.
plain
Filtration therefore follows these unit processes in virtually
Filtration
plants.
inally of fine
sand over a layer of supporting gravel. Other
tems are now common.
Mechanisms involved
in
particles larger than the pore openings; flocculation,
brought into closer contact within the
pores of the
Two
basic types of
Slow sand
water
is
were
filters
at a rate
pumped
the filter
filter
tion of water
(2 to 4
in Britain in the
•
m2
(less than 0.
still
in
The
rapid sand
filters.
filters at
the turn of the century in
means of water
if
means of
other
filters
filtration for
filter
medium
cross section of a sand
1
1-6
is
became
filters
is still
smaller municipalities and com-
Compared
is
at
is
more favorable than
sand
to rapid
they are
filters,
a rate of 80 to 160 L/min
These
filters
•
m
2
(2 to
4
a layer of fine sand or anthracite and other materials
1
Figure
1
1—5a shows a
1— 5b shows a sand-anthracite
a cross section of a typical rapid sand
and appurtenances.
—an im-
about 40 times faster than that of slow sand
bed, and Figure
filter
out-
Europe and North America,
supported over a layer of gravel or other supporting structure.
Figure
fil-
disinfection are unreliable.
can process water
(Rich, 1961) or higher, which
The
When
necessary to stop the applica-
simpler to operate, and do a better job of removing bacteria
Rapid sand
)
is
developing countries, particularly where the climate
portant consideration
gpm/ft
it
of land and are labor intensive because of the frequent cleaning
offer a practical
in
approximately
is
and remove the upper layers of sand manually for cleaning. Slow sand
to build,
2
bed thickness
filter
become too clogged,
the northern United States and Canada.
cheaper
River or lake water
produce sufficient quantities of water. Although slow sand
moded by
munities
gpm/ft 2 ).
1
filter.
They can process
nineteenth century.
with water drains to carry the filtered water to storage.
ft),
ters require large areas
they
particularly those at the sur-
into large open-air slow sand filters, with or without plain sedimentation pre-
m
to
particles are
particles in the
must be cleaned by backwashing.
of about 3 to 4 L/min
the pore openings in the filter
needed
which occurs when the
filter,
sys-
include straining of the
and sedimentation of the
filter;
ceding, depending on the raw water quality.
0.6 to 1.2
media and support
are used: the slow sand filter and the rapid sand
used
first
bed made up orig-
filter
filter
filtration
In time, the pore openings in the
filter.
become clogged, and
face,
surface water treatment
all
a process in which water passes through a
is
filter
showing the
filter
filter
bed.
box, bed,
are usually housed in a building to protect the water
from the weather and from possible sources of pollution.
tling tanks or flocculation tanks flows into the filter
Clarified water
from the
set-
box and moves by gravity through
bed to the underdrains, which lead to storage reservoirs for treated water. The
which water passes through a filter slowly decreases as particulates build up on
the filter grains and the pore openings become smaller. To provide a uniform flowrate,
the
filter
rate at
an external rate controller
to
keep the
total
loss of
—
a
form of adjustable
head through a
filter,
restriction in the outlet pipe
—
is
used
and hence the flow, approximately con-
402
Water Supply
Specific
Grain Size
Grain Size
= 2.65
Anthracite
mm
0.45-0.55
600-760
Specific
Gravity
Sand
0.70
Gravity
mm
Sand
mm
0.45-0.55
=2.6
Gravel
300-450
Chapter 11
mm iSSS!
ka
!«&<
^nO-^O.
i
Filter
The
Note:
(coal),
Gravel
5-60
—
Underdrains
mm
1
(a) Traditional
Figure 11-5
mm
m
5-60
mm
Rapid Sand
(b)
Bed
Filter
Construction of a
sand
difficulty with
Dual Media Anthracite-Sand
filter
Bed
bed.
filters is that
clogging occurs on the top layers of fine sand.
Anthracite
having a greater particle diameter and being lighter than sand, remains on top of the sand and
makes more
of the filter
bed
removal of suspended
effective in the
solids.
To Head Loss
Indicator
,
-r
Water Surface
When
Filtering
Raw Water
£
Inlet
Water Surface
When Backwashing
Wash Water
Inlet
Wash Water Troughs
Backwash
Filter
Outlet
3m = (10ft)
S'.
Sand 76 cm
oe£Grave(ftq'45
(30
in.)
cm UirsVo^'-^
Underdrain Pipes
Variable Cross-
Section Flow Rate
Constant
Output
Figure 11-6
stant.
The
Cross section of rapid sand
2.5 to 3.0
m
force water through the
is
(8 to 10
filter
cleaned by an operation
ft)
bed.
known
filter.
Source:
depth of the
When
Adapted from Linsley and Franzini (1992).
filter
box
filter
bed by up
to
50%
limits the
the limit for head loss
as backwashing.
and allows the
is
head available
exceeded, the
Water under pressure
through the pipes and underdrains and upward through the
pands the
Controller
filter.
is
to
filter
pumped
This reverse flow ex-
lighter dirt particles to
be removed
with the washwater that overflows into the washwater troughs and out to the sewer.
Where no sewer
rate
available, the
is
away
solids are hauled
The
403
Water Treatment Processes
Sec. 11.5
washwater
if
necessary, the
tor disposal.
Backwashing takes about 10 to 15 min
if required. The water re-
once a day, or more frequently
traditionally carried out
is
and
site,
of backwash must be controlled to ensure that the sand or anthracite
grains are not swept out with the washwater.
and
on the
treated
is
quired for backwashing
washing operation
is
generally about
stopped, the
is
4%
of the water produced.
medium
filter
When
will settle in place as
backwashing. since according to Stokes law [see equation
it
the back-
was before
(6.7)], the larger (or denser)
particles will settle faster than will the smaller (or lighter) particles.
swimming pool
sys-
These are closed, usually cylindrical vessels
that
For small municipal installations, industrial applications, and
tems, pressure filters are often used.
contain
material through which water
filter
ity as in
the case of rapid sand or dual-media
The
filters.
relative effectiveness of the treatment operations
Turbid lake water
as follows.
mately
forced under pressure rather than by grav-
is
TU
10
at
up
100
to
TU
covered thus
(turbidity units)
by coagulation/flocculation and sedimentation.
creases turbidity to less than
A
TU.
1
general rule of
thumb
is
Filtration
that turbidity
On
quire presedimentation before undergoing the processes described.
Example
11.3
Figure
1
Example
m
is
3.7
m
deep.
1
1.2.
1-7
is
a plan of a
The detention time
deep.
The
proposed water treatment plant for the
The detention time
11.1.
rate
The
through the
re-
the other hand,
for coagulation/flocculation
is
for the sedimentation tank (B)
(C)
filters
is
m2
10 L/min
I
city of
100,000 people
in
25 min, and the tank (A)
is
2
h,
and the tank
is
5.0
Select appropriate dimensions
.
three parallel sets of tanks provide flexibility of operation.
The required processing rate is the maximum daily rate for the city in Example
10'' L/day.
Each tank will handle one-third of this flow, or 33 x 10 6 L/day
Accordingly, the required capacity of the coagulation/flocculation tank
25 min x
2 2 '9
1
ft
mm
I
=
572.9 x I0 3
=
572.9
572.9
The required capacity
ol the
120 min x
'
916L =
is
=8 6m
-
sedimentation tank (Bi
"2
L
m3
the width of the coagulation/flocculation tank (A)
T8TT7
is
2749.9 x 1(P L
nun
So
lowered
or 99 x
(22,916 L/min).
So
is
not be necessary.
for the units.
Solution
further de-
below 10 TU, and coagulation/floc-
lake water withdrawn in winter can have turbidity
may
roughly
Very turbid river waters (1000 TU) will
by an order of magnitude by each process.
culation
far is
reduced to approxi-
is
the length of the sedimentation lank (B)
is
=
2749.9
m3
is
404
Water Supply
A
^
C
B
w*
w •*
1
C
^^
Chapter 11
|
'I
Sedimentation
Tanks at 5.0
Depth
3 at
1
8
m
12
Filter
Boxes
m
Coagulation/Flocculation at
3.7
m
Depth
Figure 11-7
2749.9
=
30.6
18 x 5.0
Each
filter will
of each
handle one-twelfth of the
total flow,
m
or 5729 L/min.
Thus
the required area
filter is
5729
=
52.1
m
2
110.0
and the length of each
box (C)
filter
is
52.1
= 5.9m
9.0
Comment:
In practice
any single unit out of service.
built.
is
customary to provide for
maximum
In this case a fourth set of parallel tanks
daily
demand with
would probably be
accommomade compact
Alternatively, each of the three sets of tanks could have been designed to
50%
date
it
of the
maximum
daily
demand.
The arrangement of
the units
is
and symmetrical for several reasons:
•
To ensure uniform flow with
as
few changes
in direction
and thus as
little
turbulence
as possible
•
To permit economical common-wall construction and simplify enclosing
a building
the plant in
405
Water Treatment Processes
Sec. 11.5
To permit
•
To
•
shutdown of one
easy
units supplj
the
parallel
stream for maintenance while the other
demand
facilitate future
expansion of the plant
11.5.3 Disinfection
To ensure
ation
that
the
is
water
most
pathogenic bacteria.
method
infection
is
it
necessary to disinfect
Chlorination
is
cially as
Sufficient
to treated
Other disinfectants include chloramines, chlorine dioxide,
to use.
France,
in
is
now
gaining acceptance
Ozonation, which has
North America, espe-
in
an alternative to prechlorination where natural organics are present.
ozone does not leave a
effective,
water to
a reliable, relatively inexpensive, and easy dis-
other halogens, ozone, ultraviolet light, and high temperature.
been used extensively
Chlorin-
it.
of disinfecting public water supplies.
from chlorine gas or hypochlorites are added
quantities of chlorine
kill
harmful bacteria
free of
is
common method
Although
The 2000
lasting residual for long-term disinfection.
x 10 6 L/day (600 mgd) Los Angeles filtration plant contains one of the largest municipal ozone disinfection systems in the world, but the water is still chlorinated prior to
distribution.
Chlorine gas hydrolyzes
Cl 2
The hypochlorous
(OC1
)
in
+ H2
HOC1,
acid,
water almost completely to form hypochlorous acid:
=
HOC1 + H+ +
C1
dissociates into hydrogen
(11.7)
(H+) ions and hypochlorite
ions in the reversible reaction
HOCL=H+ +
pH
Chlorine lowers the
the water
is
quite important in determining
hypochlorous acid can dissociate to produce hypochlorite
prime disinfecting agent,
is
(11.8)
of the water because of the hydrogen ions released
The pH of
preceding reactions.
OCL-
dominant
at a
pH
ions.
how
Hypochlorous
of less than 7.5 and
times as effective as the hypochlorite ion that dominates above
is
in the
far the
acid, the
approximately 80
pH
7.5.
HOG
and
OCI
together are called free available chlorine, meaning available for disinfection.
The
disinfecting qualities of hypochlorous acid are greatly increased at lower levels of
pH because of the
When added
greater proportion of
inorganic matter alike.
Therefore, not
production of free available chlorine.
ics
(Fe +2
demand
,
Mn +2
.
HOC1
present.
and
to water, chlorine, a very reactive element, will oxidize organic
N0
and must be
2
.
and
all
of the chlorine added to water results
The amount of chlorine
NH,) and
organic
impurities
satisfied before free available chlorine
is
that reacts
in
the
with inorgan-
known as chlorine
The application
is
formed.
of chlorine to water to the point where free residual chlorine
is
available
is
called
break-point chlorination
The
reaction of chlorine with nitrogenous impurities such as
special interest because chloramines are produced.
ammonia (NH,)
Chloramines are effective for
fection, but to a lesser degree than free available chlorine.
However, they
is
of
disin-
persist longer
406
Water Supply
water than free available chlorine does and are useful
in the treated
Chapter 11
guarding against
in
possible contamination in the distribution system, caused by improper construction and
ammonia to chlorinated water to produce chloramines is
Combined available chlorine is that residual existing in chemicombination with ammonia (chloramines) or organic nitrogen compounds. In some
The
maintenance.
addition of
called chloramination.
cal
cases
is
it
necessary to use chlorine to remove tastes and odors
much
the addition of
To
get rid of the excess chlorine,
sulfite,
isms
or sodium metabisulfite.
in
water
This requires
necessary to dechlorinate with sulfur dioxide,
is
it
The exact mechanism by which chlorine
unknown, but what
is
in water.
larger quantities of chlorine in a process called superchlorination.
known
is
that the
is
attacks organ-
water must be relatively free of
Consequently, chlorination cannot be
organic matter for disinfection to be complete.
used as a substitute for poor water treatment practices.
The two basic parameters
The
for effective chlorination are
dosage and contact time.
dosage does not follow a
rate of bacterial kill for a particular
first-order reaction,
so empirical equations are used to relate dosage and contact time for the desired percent
Sufficient chlorine
destruction.
of contact
1
.5
mg/L
at
must be added
water to both satisfy the chlorine
to the
mg/L after 10 min
The equivalent minimum combined available chlorine residual is
60 min of contact time at pH 7. Exceeding proper dosage levels is un-
demand and produce
pH
after
a concentration of free available chlorine of 0.2
7.
Tests must be car-
desirable because this causes an unpalatable chlorine taste in water.
ried out frequently to determine the proper
dosage of chlorine. To ensure sufficient time
for chlorine to kill the bacteria under varying
Many
vide at least 30 min of contact time.
If
chlorination
groundwater source,
is
it
the only
is
pH and
temperature,
form of treatment required, as
applied at the distribution system
treatment plants chlorination
is
is
it
necessary to pro-
authorities stipulate 2 h at design flow.
normally performed as the
often the case with a
is
pump
well.
In surface water
last stage
of treatment just
before the water flows into the storage reservoir.
Chlorine, a gas under normal pressure and temperature, can be compressed to a
Because chlorine gas
uid and stored in cylinders or containers.
solved in water under vacuum, and this concentrated solution
treated.
For small plants, cylinders of about 70 kg (150
plants, ton containers are
way
Chlorine
tank cars.
pochlorite
One
Ca(OCl) 2 or
common; and
is
form
is
as
it
liq-
is dis-
applied to the water being
lb) are used; for
for very large plants, chlorine
also available in granular or
in liquid
is
poisonous,
is
medium
to large
delivered by
powdered form
rail-
as calcium hy-
sodium hypochlorite, NaOCl: (bleach).
is that it combines with natural organic sub-
of the problems with chlorine
stances that
may
be present
in
water (from decaying vegetation) to form trihalomethanes
(THM), including chloroform, which
is
a carcinogen.
Since
THM
are not
removed by
conventional treatment methods, water to be chlorinated should be free of natural organics,
or an alternative disinfectant should be used.
Example
11.4
Calculate (a) the
number of kilograms of chlorine needed per day and
the contact tank in a water treatment plant supplying the city of
Example
1
I
.
I
The chlorine demand
is
1
mg/L.
1
(b) the capacity of
()(),()()()
people given
in
407
Water Treatment Processes
Sec. 11.5
Solution
We know
(a)
that at least
demand
the chlorine
I
mg
of chlorine must be added to every
mg/L and produce
liter to
we can make
daily flow rate
overcome
a tree available chlorine concentration
Since the treatment plant must be capable of operating
of 0.2 mg/L.
mum
1.2
of
maxi-
at the
the following calculation to determine the
amount
of chlorine needed:
—
kg
-s chlorine
day
.
= L=
=
(b)
II
we assume
a
,_
tor
1
maximum
99.0 x 10 6 L/day x
1
18.8
minimum
mg
.2
x
day
J
d
x
L
1.2
(at
mg
kg/mg
maximum
production)
contact time of 30 min. then
=
flowrate x contact time
=
99.0 x 10 6 -=- x
=
2.063 x 10 6 L
=
2063
ay
'
,
^
,
1440 min
day
in
x 10 6
1
-L
mg/L x
kg chlorine added daily
required capacity of contact tank
The contact time
kg
£-
chlorine
—,
30 min
m3
is usually provided by a large storage chamber
The primary function of the clear well is to isolate
of municipal water demand, but it also serves the pur-
water treatment plants
called a clear well or storage reservoir.
the plant from the hourly fluctuation
pose of allowing sufficient contact time so that the concentration of free available chlorine
will stabilize at the proper value before being
Ozonation
is
pumped
the disinfection of water by adding
oxidizer of inorganic and organic impurities.
no
effective against Cryptosporidium, leaves
Its
use
it
is
widely used
in
tastes or odors,
Europe, particularly
to disinfect public drinking water.
In
in the future.
combined
(3)
is still
a powerful
it
is
and unlike chlorine, appar-
compounds hazardous to humans.
many municipalities
North America, except for the
is
cities
of
limited to a few smaller plants.
The disadvantages of ozone
not be transported easily and therefore must be generated on
a
is
France, where
in
Montreal and Los Angeles, disinfection with ozone
This will probably change
ozone (CM. which
advantages over chlorine are that
ently does not react with natural organics to form
Ozonation
to users.
are that
site. (2)
it
(
1
)
can-
does not provide
residual like chloramines to guard against distribution system infection, and
quite costly.
11.5.4 Removal of Dissolved Substances
Several of the unit operations discussed so far are partially effective in removing objectionable dissolved substances.
solved matter
is
in
water caused by colloidal or dis-
reduced by coagulation/llocculation.
Generally, though, conventional
For example, color
408
Water Supply
processes are not intended to remove dissolved substances or gases.
Chapter
If these are a
1
prob-
lem, several other unit operations are available.
Aeration
ing, stain
used to remove excessive amounts of iron and manganese from
is
These substances cause
groundwater.
plumbing
By bubbling
Mn
manganese (Fe +2
,
Mn+ 2
)
is
oxidized to
which precipitates out and can be removed
),
removes odors caused by hydrogen
also
and color problems, interfere with launder-
through water, or by creating contact between
air
ing, dissolved iron or
+4
taste
and promote the growth of iron bacteria
fixtures,
Softening of water
tank or
in a settling
divalent metallic ions, principally
Mg+ 2
Hardness
.
in
1
Softening
is
unusual), but
1500 mg/L
may
is
CaC0 3
is
the result of
is
C0 2
As noted
.
in
concentrations of both carbonate and noncarbonate hardness in water
1.3.2, the
are expressed as
Aeration
the presence of
water
contact with soil and rock, particularly limestone, in the presence of
Section
filter.
(H 2 S) gas.
removes hardness, caused by
sulfide
a process that
Ca +2 and
is
water mains.
in
and water by spraya less soluble form (Fe + \
air
.
seldom necessary
is
it
uncommon).
not
above 200 mg/L
for surface waters (where hardness
occasionally desirable for groundwaters (where hardness above
Hard water
human consumption
acceptable for
is
be unsuitable for industrial use because of the scaling problems
it
but
causes in boilers.
Lime-soda softening and ion exchange are two of the methods available for softening
hard water. In lime-soda softening, lime (CaO) added to water hydrates to Ca(OH) 2
CaHC0 to insoluble
CaC0 and soluble MgC0 This soluMg(OH) 2 and CaC0 3 with the addition of more
which removes carbonate hardness by converting the soluble
CaC0
ble
3
,
and the soluble
MgC0
3
MgHC0
3
then precipitated as
is
Noncarbonate hardness
lime.
to insoluble
(e.g.
(NA 2 C0 3
soluble
3
3
3
CaS0 4
and
MgS0 4
)
is
.
precipitated as
forced through an
CaC0 3
+2
removes
and Mg +2 ions
zeolite,
which
preferentially
Ca
ion-exchange resin such as
using soda ash
from the water and releases Na +
Activated carbon is
remove organic contaminants.
With ion exchange, hard water
).
ions,
which form soluble
is
salts.
an extremely adsorbent material used in water treatment to
First, a suitable
Activated carbon
ized by heating the material in the absence of
tivated
by heating
to increase
its
it
pore
presence of
in the
ganics being removed.
pumps
Powdered
presence of toxic organics
In
brane
air,
C0 2
pH
a two-stage process.
air.
Then
carbon-
the carbonized material
or steam to burn off any tars
,
is
it
is
ac-
has and
in
is
of the water as well as the complexity of the or-
activated carbon can be added to water just after the
or at any point ahead of the
moval of organics which cause
(made from
in
Adsorption of gases, liquids, and solids by activated carbon
size.
influenced by the temperature and
low-lift
produced
is
base material such as wood, peat, vegetable matter, or bone
tastes
filters.
and odors.
It
has been used mainly for the
re-
However, as concern grows over the
our water supplies, the role of granular activated carbon
anthracite) will increase.
reverse osmosis (RO), fresh water
in the direction
is
forced through a semipermeable
opposite to that occurring in natural osmosis.
brane removes dissolved
salts, the
main application
However, the process also removes organic materials,
plication in water treatment
is
growing.
for
RO
Because the
memmem-
has been in desalination.
bacteria,
and viruses, and
its
ap-
409
Transmission. Distribution, and Storage of Water
Sec. 11.6
11.6 TRANSMISSION, DISTRIBUTION,
AND STORAGE OF WATER
In this section
water that
is
we
consider only distribution and storage of municipal, potable, water;
satisfactory for
most purposes.
be appropriate for specific uses,
not involve the municipality.
is
Water of higher or lower quality
that
may
normally provided by a private arrangement that does
Examples of such
may
special needs
include;
required by laundries and textile mills
• softened water:
•
carbon-filtered water:
necessary for certain beverage manufacturers
•
reclaimed wastewater:
useful for industrial cooling, cleanup, maintain-
•
untreated water (dual system):
acceptable for agriculture, golf courses, parks,
ing wetlands
fire fighting,
These water quality problems are not a concern
and
in this
street
washing
book and,
in this discussion
municipal engineering that follows, water quantity rather than water quality
is
of
the cen-
tral issue.
11.6.1 Transmission
The conveyance of
large quantities of water for a relatively long distance
points of supply and distribution
in
called transmission.
is
mVday
North America typically requires about 15,000
The transmission
amount
maximum
to allow for the
daily
time.
When
possible, gravity flow
Water
quantities.
at
in
is
between the
small city of 30,000 people
(4
mgd) of water (almost
would be sized for at least twice this
flowrate at the end of the design period plus al-
15,000 tonnes daily).
lowances necessary for increases
A
line
population and per capita water use during that
the preferred
an elevation above that of
its
method
for transporting these large
destination has potential energy that
can be converted to the kinetic energy of moving water by the slope of an aqueduct.
The
steeper the slope, the faster the water velocity (within limits) and the smaller the
aqueduct can be.
Since frictional losses are directly proportional to the square of the
water velocity, there
is
an
optimum aqueduct slope to move water at a desired flow rate
The most economical route for gravity flow, in
while minimizing losses due to friction.
which the
sidered,
effects of
aqueduct size and slope on excavation (or tunneling) costs are con-
must be compared on an annual cost basis with a pressurized system where the
energy costs for pumping
may
be offset by a smaller, shallower conduit.
There are three basic types of aqueducts.
pressure and are called flumes
if
Open channels
they are supported
at
usually chosen
if
of excavation.
Lining open channels with impervious materials
local soil
is
operate
at
atmospheric
or above ground level.
topographic conditions are favorable for gravity flow with a
too porous and significant seepage losses occur.
concerns may also necessitate covering the channel.
may
They
are
minimum
be required
if
the
Evaporation and pollution
Materials such as concrete, butyl
410
Water Supply
may be used
rubber, and synthetic fabrics
when topographic
to line
open channels.
conditions rule out the use of open channels.
Chapter 11
Pipelines are built
Placed above or below
ground, these conduits often work under high operating pressures, so they are built of
reinforced concrete, steel, cement-lined steel, or cast iron pipe.
Reliable operation re-
quires the installation of a system of check valves, surge control equipment, expansion
pumps, and many other appurtenances.
joints, inspection ports,
pressure caused by sudden changes
Massive increases
imized and controlled to prevent costly damage to the pipelines.
when open
trenching for a pipeline
in
flow are called hydraulic surges and must be min-
in
is
Tunnels
are used
impractical.
11.6.2 Distribution
A water distribution
maximum
daily
system must be able to deliver either the
demand
plus the
fire
maximum
requirements (whichever
is
hourly flow or the
greater) to any point in
Mains at least 150 mm (6 in.) in diameter are needed to do this in resiThe pattern of distribution mains, street layout, topography, and pipe sizes
cost and reliability of the system. Figure 1 1-8 is an example of a grid distri-
the municipality.
dential areas.
all
affect the
bution system that will continue to serve most water users by at least one other route in the
event of pipe failure.
Shutoff valves
at grid
junctions can isolate any pipe segment for
maintenance or repair without interrupting service
important feature for system
to other parts of the grid.
reliability, particularly in
ance rates are based largely on the availability of a
hydrants while the system
Water pressures
is
fire.
minimum
This
is
an
fire insur-
pressure and flow at
network range from 130
with buildings not over four stories
in
Branch
Distribution
Municipal
fire
meeting the needs of regular users.
in the distribution
psi) in residential areas
case of
Mains
Flow
Looped Feeder
Main
•Grid Pattern
Branch
Figure 11-8
Distribution system configuration.
to
260 kPa (20 to 40
400 to
height and from
Sec. 11.6
500 kPa (60
to
75
psi) in areas with taller
practical to install costly additional
commercial or
pumps
this
that serve the
problem, booster pumps
in the
pump
For temperate climates
north and east sides of the street (the
be both safe from
traffic
in the
warmer
is
im-
water to rooftop reservoirs
firefighting.
Watermains are located within municipal road allowances so as
for maintenance.
It
buildings with adequate water.
tall
buildings
upper floors and provide water for
residential buildings.
plant or reservoir to increase system
at the
pressures enough to supply the upper floors of very
To solve
411
Transmission. Distribution, and Storage of Water
to be accessible
northern hemisphere, installation on the
sides)
is
preferred, at sufficient depth to
loads and below frost level
(1
to 3 m).
Figure 11-9 shows a
arrangement for water (and sewer) services.
typical
Property Line
Property Line
Manholes (Every 100 m±)
(Placed as Required)
Fire
Hydrant (Every 100 m±)
Curb
Sidewalk
Storm Sewer
—
j-
(+)
- - Sanitary
<
5ft )
(5
5.0
m
(16
ft)
Sewer
ft)
Standard Municipal Road Allowance
20 m (66 ft)
4
Figure 11-9
Topography
is
"
Typical arrangement of water and sewer services on a residential street.
another factor
in distribution
system design.
Extreme ranges
in el-
evation over an area can cause excessive pressure on water mains in low-lying areas and
insufficient pressure at higher elevations.
age and
may damage
The high pipe pressure
hot water tanks; the low pressure
contamination of the mains and inadequate
result in
is
fire
increases water leak-
not just inconvenient but can
protection.
The solution is to
pumping station
divide the distribution system into separate zones, with a reservoir and
in
each zone fed directly by high-pressure feeder mains from the water plant or main
Designing a pipe network involves selecting a system of pipes that vary
reservoir.
size
and
that will
demands
tion of
in
provide the desired flows and pressures for any reasonable combina-
at different locations.
11.6.3 Storage
Storage
mand,
to
is
necessary
provide
fire
in
any municipal water supply system to meet variable water de-
protection, and for
emergency needs. Three types of reservoirs
used: surface reservoirs, standpipes, and elevated tanks
(Hammer,
1986).
are
Surface reser-
412
Water Supply
where they
voirs are located
vation on a
contamination.
will provide sufficient water pressure, either
Standpipes are basically
stitutes the useful storage to
uneconomical, and above
changes
system
demand
pumps at the
in
demand.
Reservoirs that operate this
this rate or to receive
way
their regulating function
may be
the
is
to
pump
in height are
water into the distribution
are
water
known
if
demand
is less
by hydrostatic pressure alone.
of a reservoir affects
its
than the
as floating reservoirs; that
located in the center of several distribution areas.
location
ft)
the preferred choice.
given period and allow a reservoir either to supply extra wa-
demand exceeds
voirs
(50
varies according to reasonably predictable patterns over
rate.
how
m
become
treatment plant are not normally designed to meet these
ter if
complish
Standpipes over about 15
Instead, the usual practice
at a fixed rate for a
ability
to
is,
Figure 11-10 illustrates
Poorly Located Tank
Pumping
Station
(b)
Well Located Tank
Pressure during
Periods of Low Demand
Pressure during
Periods of High Demand
Figure 11-10
Effect
of water storage
reservoir
Adapted from Linsley and Franzini (1992).
location
they ac-
equalize operating pressures
Station
(a)
pumping
In large cities, reser-
Pumping
Source:
ele-
whose upper portion con-
cylindrical tanks
this height elevated storage tanks
Residential water
High-lift
tall
by natural
are usually covered to avoid
produce the necessary pressure head and whose lower por-
tion serves to support the structure.
the day.
They
or through the use of pumps.
hill
Chapter 11
on pressure
distribution.
Figure 11-11
Elevated water storage tanks. (Photos courtesy of R. V. Anderson Associates Limited.)
Elevated water tanks, either steel or concrete, are
The
distribution
systems,
demand
part of the city with a
in
(a)
city of
adjustable legs that provide for
in
Saudi Arabia stores 800
The
413
Transmission. Distribution, and Storage of Water
Sec. 11.6
m3
5700-m 3
initial
(2.1
x
commonly used
Welland (population 50,000)
to provide equalizing
Canada handles
in
(1.5 x 10 6 gal) steel tank
differential settlement,
10 6 gal)
of well
water
(b)
in
The
39
m
city of
(129
A
ft)
storage
for
high,
supported on 12
Kharji (population 100,000)
a concrete tank, 116
m
(380
ft)
high overall.
structure includes a 400-seat revolving restaurant.
Note how high water use and the accompanying
throughout a distribution system.
tion losses increase the slope of the pressure profile so that water starts to flow
Once
reservoir to the surrounding area.
lic
water
the variable water
profile
pump
from the
and replenish the storage.
demand
decreases, the slope of the hydrau-
to the tank also decreases,
In
allowing water to enter the tank
recent years elevated tanks have
partly because of their increased cost
inexpensive variable-speed
the
become
less popular,
and partly because of the availability of relatively
pumps and
demand. Figure
fric-
from the
controls that
make
it
possible to adjust
pumping
shows examples of elevated water storage tanks.
In addition to selecting the type and location of storage, storage size must be determined. This requirement depends on the population (water demand) and the purpose
of the storage. Volumes for the three purposes
flow equalization, fire protection, and
rates to varying
emergency needs
they
may
—
I
I
-I
l
—
are calculated separately according to the time period over
be needed.
which
414
Water Supply
Equalizing storage, also called operating storage,
Chapter 11
used to meet variable water
is
demands while maintaining adequate pressure on the system. Where information on
water demand is available, storage volume can be calculated or found graphically (from
a mass diagram, for example). When no information is available, operating storage is
taken to be 15 to
25%
Fire storage
is
of
maximum
daily consumption.
calculated by taking the product of
fire
flow and
duration.
fire
Fireflow duration times suggested by the National Fire Protection Association
are given in Table
reliability
1
1-7.
of the water supply source.
storage capacity
if
may be
Fire-flow capacity
For example, a municipality
a water source such as a single well
TABLE 11-7
FIRE FLOW
(NFPA)
raised or lowered depending on the
is
may
increase
its fire
used.
DURATION OF REQUIRED
Required Fire Flow
Million gallons
Liters per
Duration
per day
second
(h)
3.60 or less
160 or less
2
4.32
190
3
5.04
220
3
5.76
250
4
6.48
280
4
7.20
320
5
7.92
350
5
8.64
380
6
10.08
440
7
11.52
500
8
12.96
570
9
14.40 or
more
630 or more
10
Adapted from National Fire Protection
Source:
Association. Fire Protection Handbook, 17th ed.
(Boston, 1991).
Emergency storage
the Insurance
SI units by authors.
of up to five times the
Advisory Organization,
or repair to the system. This
is
to provide
seldom done
estimated to be one-fourth to one-third the
maximum
daily
demand
is
suggested by
water during shutdowns for maintenance
in practice,
sum of
and emergency storage
the operating
and
fire
is
usually
capacity require-
ments.
The sum of
the three
volumes for equalization,
fire,
capacity provided in a municipal water supply system.
and emergency
It
will
is
the storage
normally be about
1
day's average consumption.
Example
11.5
Calculate the required storage capacity for the mixed industrial-commercial-residential city
of 100,000 people used in Example 11.1.
From Example
Solution
Mow
is
35.40(1
duration
is
9
fire
h.
11.1, the
L/min i5n
We
i
>
maximum
daily consumption
Us), and therefore, from Table
operating storage
=
99 x 10 6 L x 0.20
fire-flow storage
=
35,400
total storage
is
99.0
I0 6 L/day.
•
recommended
1-6, the
1
The
flow
thus have
emergencj storage
11.7
415
Future Needs and Development
Sec. 11.7
required
=
—
x
mm
=
T" n
6()
10 6
19.8 x
=
x 9 h
,'
L
x
19.1
10'
L
h
(operating storage plus fire-flow storage)
"
=
1(19.8 x 10 6
=
(19.8
+
19.1
+I9.I x 10")=
+
13.0) x
10 6
13.0 x
=
L
10"
51.900
m
L
3
FUTURE NEEDS AND DEVELOPMENT
Despite the man) achievements of water supply engineering
health and welfare, there
a balance
s\
stems.
still
between our need
First, at least
of clean water.
We
for clean
contributing to
in
remain three formidable obstacles
to the
human
establishment of
water and the proper functioning of ecological
one-half of the world's people do not enjoy an adequate supply
developed nations have grown up with the financial and tech-
in the
nical infrastructures of water suppl)
systems and institutions firmly
veloped countries often do not have
this
and increased water needs make
it
both rural and urban populations
in the
advantage
at
The demand
most imperative.
less
Less de-
in place.
the very time population growth
water for
for clean
developed countries was identified by the
United Nations as the single most pressing challenge of the 1980s, which were designated as the International Drinking Water Supply and Sanitation Decade.
b\
1990.
less
than half of the original objective was reached.
Unfortunately,
Second, the spread
through the biosphere of an increasing number of chemical compounds used by industry
has created
some doubt
as to the effectiveness of present water treatment
presenting potential long-term health hazards associated with their presence
Third, the general quality of freshwater sources
water.
the increasingly intensive use of such sources
difficulties in
An
is
now
by our growing
adequate suppl) of clean water
financial
and
countries evolved slowly
lation
in
drinking
deteriorating because of
industrial societies.
is
The
an absolute prerequisite to the provision of
The reasons
technology of water treatment and supply have not been applied
are both
in
meeting these three challenges are formidable.
proper health care, nutrition, and industrialization.
tries
methods
in
and upkeep were not
institutional.
that
in less
advances
in
the
developed coun-
Present water supply systems
in
developed
an environment where the capital resources for their instala
major problem.
This approach
is
not possible in poorer
countries that must quickly install capital-intensive water treatment and distribution svs
terns to
meet the demand
tor clean
though the methods covered
in
water by an exponentially growing population.
this
bonk
are applicable to
developed countries, other appropriate technologies
for
many urban
areas
in
Alless
water suppl) must be developed
416
for
Water Supply
remote
now
Simple solutions tailored
more
receiving
The
obvious,
Appropriate technology
rural areas.
a crucial factor.
more
insidious.
modern water supply
scale
a concept that recognizes low cost as
needs
developing countries are
in the
attention.
institutional barrier to
is far
is
to local
Chapter 11
implementing water supply technology, although not as
Adequate funding does not guarantee success.
facilities
Lowry (1980)
personnel to maintain them.
Large-
have often gone unused because of a lack of skilled
notes that methods must be used which can
be quickly taught to local technicians, implemented properly by unskilled and semiskilled labor,
and accepted culturally by the inhabitants.
The second challenge
for water supply engineers
is
the control of
many new
Over
chemicals for which conventional water treatment plants have not been designed.
1000 new chemicals a year are being added
to the large inventory of
Synthetic organic chemicals
pear as products or by-products of industrial processes.
PCBs
down in
chemicals that ap-
such as
(polychlorinated biphenyls), trihalomethanes, Mirex, and dioxin do not
break
natural ecosystems.
tion
needed
is
The
ties to
if
The biggest problem facing
iden-
is
meaningful drinking water standards are to be developed.
problem, the decreasing quality of water sources,
third
One
consider alternatives.
is
is
forcing municipali-
to look farther afield for unexploited water supplies.
Large water transmission projects such as those described
if
health scientists
between various chemicals and human ailments. This informa-
tifying the relationships
in
Chapter 10 are undertaken
population growth simply makes other alternatives too expensive.
Environmentalists
have voiced their concern over the effect that massive withdrawals of water from remote
The
wilderness reservoirs might have on wildlife.
water for urban centers
is
fear of not having sufficient fresh
demonstrated by the vast sums that governments spend
to
construct these water transmission projects.
Another alternative
certain water needs.
cal reaction of
methods.
It
is
greater reuse of extensively treated municipal wastewaters for
has been
much more
difficult to
overcome
the negative psychologi-
people to the reuse of municipal wastewaters than to develop the treatment
Perhaps public objection will moderate as water recycling systems begin
prove themselves
in areas that
have very
little
to
choice but to apply these techniques.
PROBLEMS
11.1.
Why
maximum
11.2. Calculate the water
rate,
a
and tire-flow
wool and
daily
A
small
demand
plus hie flow? (See
consumption (average daily
rate) for a
textile mill
New
rate,
England town of
I
hourly
Example
maximum
(),()()()
make your own assumptions and
community of population 1000
hotel,
plus hie flow
maximum
The only industry
its
own water
hourly
in
town,
supply.
If
give your reasons for them.
located in the Canadian arctic has a trucked water
supply system, drawing from a nearby lake (3
There are 200 houses, one
demand
11.1).
daily rate,
people.
with a production of 100 tons/month, has
there are any data missing,
11.3.
maximum
are distribution pipes not sized according to
instead of
km from
the village) as a water source.
one hospital, one school, one nursing
station,
and two
417
Problems
Chapter 11
The
general stores in the community.
is
total
road system
town
in
is
km
2
long.
equipped with a water storage tank of 1000 L capacity, with bigger tanks
The average water consumption
tablishments.
40 Lpcd.
is
quite
is
It
common
storms to prevent the trucks from traveling to the lake for up to 3 days.
viding
if
The trucks
each truck has a 4000-L tank.
Make any assumptions you
protection.
fire
other es-
for winter
Based on
formation, determine (a) the size of the storage reservoir in the village; (b) the
trucks required,
Each house
in the
this in-
number of
also serve the purpose of pro-
necessary to complete the as-
feel are
signment, giving reasons for each assumption.
11.4.
A
well will be used to supply a village of
analysis on a water sample
is
5000 people with
mg/L
Constituent
(S0 4 )
Sulfates
50
CaCO,
220
Chlorides (CI)
200
Iron (Fe)
1.8
Lead (Pb)
0.01
Manganese (Mn)
Nitrate nitrogen (as
Recommend
11.5.
0.1
N)
4.0
a treatment process for the well supply, and
the lines of Figure
1
The following chemical
water.
available:
draw a schematic diagram along
1— 3b.
Presedimentation can reduce the suspended solids concentration of raw river water from
500 mg/L
gallons 9
to
200 mg/L.
How many
pounds of dry
gravity of these solids
If the specific
is
solids does this represent per million
2.60 and the sludge removed has a solids
week
concentration of 29c, what volume of sludge must be removed every
of 4
11.6.
What
turbidity,
is
how
is it
what processes are used
11.7.
at a
design flow
mgd?
The water treatment
river intake.
to
measured, what problems does
remove
plant for the city of 100,000 studied in
Normally, the turbidity of the water
rains cause the turbidity to increase to
nearby upstream town
is
known
500 TU.
is
its
in a
water supply, and
Example
1
1.3 is
supplied by a
50 TU. Three or four times a year heavy
In addition, the
to release partially treated
the high rate of stormwater runoff flowing through the
feeding the plant. In
cause
it
it?
sewage treatment plant of a
sewage
at
these times because of
combined stormwater and sewage
lines
present configuration the plant cannot provide the required quality of
drinking water during these periods, and several prominent citizens have begun to complain.
Discuss the strategies open to you as the waterworks engineer for the town.
11.8.
Fluoride
is
Too much
often added to municipal drinking water as an aid in preventing tooth decay.
fluoride in drinking water can cause fluorosis (a mottling of the teeth).
proper dosage
weekly
11.9.
in
the
for the city in
community
Example
is
0.8 mg/L, calculate the
amount of
fluoride
If
the
needed
11.1
Define coagulation and flocculation and explain
how
these processes
remove colloids from
water.
11.10. Figure
1
l-5a shows the construction of a rapid sand
layer of larger gravel particles
is
filter
not placed on top to
bed.
filter
One might wonder why
a
the larger suspended particles
418
Water Supply
before the finer sand particles are used to
first,
words, a
more
filter
like the
one
Figure
in
1
filter
Chapter 11
small suspended particles.
1— 3b might be used.
Explain
why
In other
this is not
done.
11.11. Figure
1—5b shows an anthracite-sand
1
How
the sand particles.
after
11.12.
is
it
filter
possible for the
The
bed.
filter to
anthracite particles are larger than
return to the proper grading
scheme
backwashing?
Why
is
of water without chlorination partially effective
filtration
pathogenic
in controlling
bacteria but not pathogenic viruses?
11.13.
The nominal detention time of the sedimentation tanks in Example 11.3 is 2 h. Effluent
from the middle tank is more turbid than that from each of the other two tanks. You are
asked to investigate what the problem may be and suggest a remedy if you can. How will
you proceed?
11.14. Chlorination
method
the usual
is
for disinfecting water in
North America.
(a)
Name
(b)
Why
Why
does the presence of ammonia
rine?
Why,
Why
does coagulation with alum ahead of chlorination increase the efficiency of disin-
(c)
(d)
the
is
it
two parameters
that control the extent
of disinfection.
necessary to guard against an overdose of chlorine?
in
water reduce the bactericidal efficiency of chlo-
do some plants add ammonia
then,
to chlorinated
water?
fection of water by chlorine?
(e)
Assume
that disinfection with chlorine follows a first-order reaction.
water sample containing 1.0 mg/L chlorine, the
is
1
00,000/ mL.
initial
In a chlorinated
concentration of viable bacteria
At the end of a 5-min contact time the number of viable bacteria has
decreased to 10/ mL.
What
would a contact time of 10 min have on
effect
the bacterial
count?
11.15.
A new
residential
community
midwestern United
in the
to reach a
If
the population
is
is
expected
of 5000 determine the following (make necessary assumptions and
your reasoning).
state
(a)
maximum
by private wells,
States, served
considering a groundwater source of supply (Figure 11-12).
What
is
to the
town
the
minimum capacity of
gpm and L/min)?
the well that
is
required to adequately supply water
(in
(b) Fire insurance regulations require that there be sufficient storage for firefighting pur-
poses.
location
Calculate the
A
or
B
(in
total
volume necessary
gallons and
for a ground-level fire reservoir at either
liters).
i
Elevated Tank
1
1
Fire
Reservoir
Location B
Trunk Watermain
Well and Pumping Station
Fire
Reservoir
Location
A
Distribution
System
Figure 11-12
419
Problems
Chapter 11
What should be
(c)
ervoir
in
is
Assuming
(d)
that the
ing the night
(
gpm and
the capacity in
location
A?
If
town
10 p.m.
is
it
L/min, of (he trunk watermain
if
the tire res-
B?
location
will use an elevated tank to provide all the
water required dur-
6 A.M.), what should be the capacity of the elevated tank
to
Assume
gallons and liters)?
in
that
during
this
period the hourly water consumption
(in
is
one-third of the average hourly consumption.
11.16.
You have been lucky and obtained
assignment
to act as
is
a
summer job
with the World Health Organization.
Your
an engineering student advisor to the mayor of a small village
Central America, located
in the tropical
coastal flatland.
The
village has
200
in
families, or
The majority of the families carry their water in buckets from a nearby
The average carry is 500 m. About 259c of the families purchase their water from
about 1500 people.
stream.
Five of the wealthier families have private wells on their
a local vendor at 4 cents/gal.
you
The mayor informs
Toilet facilities throughout the village are outdoor privies.
premises.
that there
have been incidents of various kinds of sicknesses, which have been caused
situation.
He asks you for suggestions to improve
M. McLellon, Florida Technological University.)
by the local sanitation
(Courtesy of W.
(a)
the situation.
evaluating the costs and benefits, what factors must you consider to determine
In
whether a community water supply project should be undertaken?
two
(b) Suggest
What
(c)
A
more) systems of different levels of sophistication (and
maximum
water supply, providing a
of 1000
mVday
to a
a
ganics are extremely soluble
in liquid
Zorbitol
=
(SG
of Zorbitai, determine the concentration of toxic organics
achieved
Fortunately, these or-
1.5), resulting in a
concentration of toxic organics in Zorbitol compared to water.
in the
in (a) a
single-stage mixer-settler (Figure
mixer-settler system (Figure
L
1
in the
100-fold differ-
Using 5
town water
that
1000
m 3 /day
Zorbitol
m
3
/
1— 13a; (b) a two-stage countercurrent
1— 13b), assuming complete mixing
in all cases.
Water
to
Town
Mixer
Settler
Zorbitol to
Recovery
day
(a)
Water Supply
1000
m 3 /day
Zorbitol
to
Water
Mixer
Mixer
Settler
Settler
1
2
Recovery
Fig ure 11- -13
to
Town
Zorbitol
5
(b)
mVday
would be
Water Supply
5
commu-
town contains 100 Ug of toxic
organics/L which conventional treatment processes cannot remove.
ence
cost).
make
water supply a successful venture?
nity
11.17.
(or
resources and services must the village mobilize and sustain to
m3
/
day
420
Water Supply
Chapter 11
REFERENCES
apha,
awwa, and wpcf. Standard Methods
for the Examination of Water and Wastewater. 18th ed.
Washington, D.C.: American Public Health Association, American Water Works Association,
Gleick,
and Water Pollution Control Federation, 1992.
D.
P.
Hammer, M.
(ed.).
Water
in Crisis.
New
York: Oxford University Press, 1993.
New
Water and Waste Water Technology, 2nd ed.
J.
York: Wiley, 1986.
Insurance Services Office. Guide for Determination of Required Fire Flow.
New
York: Insur-
ance Services Office, 1974.
Linsley, R. K, and Franzini,
Hill,
Lowry,
J.
B. Water Resources Engineering, 4th ed.
New
McGraw-
York:
1992.
E. F.
"Breaking the Cost Barrier to Household Water Service." Journal of the American
Water Works Association, December (1980): 672-677.
National Fire Protection Association, Fire Protection Handbook,
17th ed. Quincy,
MA: Na-
tional Fire Protection Association, 1991.
nhw
(Minister of National Health and Welfare Canada). Guidelines for Canadian Drinking Water
Canada Communication Group, 1993.
Quality. 5th ed. Ottawa:
Rich, L. G. Unit Operations of Sanitary Engineering.
Solley,.W.
in
Chase, E.
B..
1980".
U.S.
B.,
and Mann, W. B.
iv.
New
York: Wiley, 1961.
"Estimated Use of Water
in the
United States
Geological Survey Circular 1001. Washington, D.C.: U.S. Government
Printing Office, 1983.
Steel, E. W., and
McGhee,
T.
J.
Water Supply and Sewerage, 6th
ed.
New
York: McGraw-Hill,
1991.
U.S. EPA. Drinking Water Regulations and Health Advisories. Washington, D.C.: Office of Water,
U.S. Environmental Protection Agency, 1993.
Viessman, W.,
Harper
WHO.
jr.,
&
and Hammer, M.
J.
Water Supply and Pollution Control, 5th ed.
New
Row, 1993.
Guidelines for Drinking Water Quality. Geneva: World Health Organization, 1984.
York:
CHAPTER
12
Water Pollution
Glynn Henry
J.
12.1
INTRODUCTION
As noted
in
Chapter
the relationship
8.
between polluted water and disease was firmly
established with the cholera epidemic of 1854 in London, England.
Protection of public
health, the original purpose of pollution control, continues to be the primary objective
in
many
areas.
However, preservation of water resources, protection of fishing areas.
and maintenance of recreational waters are additional concerns today.
problems intensified following Word War
II,
when dramatic
increases
Water pollution
in
urban density
and industrialization occurred. Concern over water pollution reached a peak
1970s.
In the
ment. Public
ada,
United States, where national control
Law 92-500 (1972) was
where pollution control
Resources Act (1970),
tion.
The
countries,
situation
is
v\as the
was similar
is
in the
the official recognition of this concern.
In
a provincial responsibility, Ontario, through the
most active province
in
in
mid-
exercised by the federal govern-
CanWater
prodding municipalities into ac-
Great Britain, Europe, Japan, and other industrialized
where increasing urbanization and industrialization were accompanied by seIn less developed regions, wastes from burgeoning pop-
rious water pollution problems.
ulations are a threat to public health and endanger the continued use of often scarce
water supplies.
Water pollution
polluting material or
is
its
an imprecise term that reveals nothing about either the type of
source.
The way we
deal with the waste problem depends
o\)
421
422
Water Pollution
Chapter 12
whether the contaminants are oxygen demanding, algae promoting, infectious,
simply unsightly.
toxic, or
Pollution of our water resources can occur directly from sewer out-
or industrial discharges (point sources) or indirectly from air pollution or agricul-
falls
tural or
urban runoff (nonpoint sources).
This chapter deals primarily with point sources.
origins, quantities,
It
provides information on the
and characteristics of wastewater and the effects of pollutants on the
The use of stream standards and water quality objectives to control
combined and separate sewers evaluated. The
water environment.
pollution are reviewed and the features of
methods available
principles of wastewater treatment and the
for both large
Systems covered range from large municipal
installations are explained.
and small
facilities
em-
ploying combinations of physical, biological, and chemical methods to units suitable for
single-family needs.
Legal and economic controls are other measures used to control water pollution.
Fines, surcharges, financial incentives, subdivision agreements, and sewer-use bylaws
are
some of
described.
12.2
These and current trends
the tools available.
in
pollution control are
Principles covered in the chapter are illustrated by examples.
WASTEWATER
Municipal wastewater, also called sewage,
ally
over
99%)
The concentration of
dissolved.
pressed in mg/L, that
weight/volume
ratio
industrial wastes,
lu t e
solutions
is
is.
a
complex mixture containing water (usu-
these contaminants
normally very low and
is
milligrams of contaminant per
liter
of the mixture.
used to indicate concentrations of constituents
and other
dilute solutions.
in water,
is
This
exis
a
wastewater,
Since the specific gravity (SG) of these di-
similar to that of water, the concentrat