LIVING IN THE ENVIRONMENT, 18e
G. TYLER MILLER • SCOTT E. SPOOLMAN
20
Water Pollution
©©Cengage
CengageLearning
Learning2015
2015
Case Study: The Gulf of Mexico’s Annual
Dead Zone
• Spring and summer – huge inputs of
nutrients from the Mississippi River basin
• Depletion of dissolved oxygen in the Gulf
of Mexico’s bottom layer of water
– Contains little marine life
– Disrupts nitrogen cycle
© Cengage Learning 2015
Missouri River
Mississippi
River Basin
Ohio River
Mississippi River
© Cengage Learning 2015
Fig. 20-1a, p. 544
Mississippi River
GULF OF
MEXICO
© Cengage Learning 2015
Fig. 20-1b, p. 544
20-1 What Are the Causes and Effects of
Water Pollution?
• Water pollution causes illness and death in
humans and other species, and disrupts
ecosystems
• Sources:
– Primarily agricultural activities, industrial
facilities, and mining
– Growth of both the human population and our
rate of resource use makes it increasingly
worse
© Cengage Learning 2015
Water Pollution Comes from Point and
Nonpoint Sources
• Water pollution
– Change in water quality that can harm
organisms or make water unfit for human
uses
• Point sources
– Located at specific places
– Easy to identify, monitor, and regulate
© Cengage Learning 2015
Water Pollution Comes from Point and
Nonpoint Sources (cont’d.)
• Nonpoint sources
– Broad, diffuse areas
– Difficult to identify and control
– Expensive to clean up
© Cengage Learning 2015
Water Pollution Comes from Point and
Nonpoint Sources (cont’d.)
• Leading causes of water pollution
– Agriculture activities
• Sediment eroded from the lands
• Fertilizers and pesticides
– Industrial facilities
• Inorganic and organic chemicals
– Mining
• Erosion and toxic chemicals
© Cengage Learning 2015
Fig. 20-2, p. 545
© Cengage Learning 2015
Fig. 20-3, p. 546
Major Water Pollutants Have Harmful
Effects
• Infectious disease organisms
– Contaminated drinking water
– An estimated 1.6 million people die every
year, mostly under the age of five
© Cengage Learning 2015
© Cengage Learning 2015
Table 20-1, p. 547
20-2 What Are the Major Water Pollution
Problems in Streams and Lakes?
• Streams and rivers around the world are
extensively polluted
– However, they can cleanse themselves of
many pollutants if we do not overload them or
reduce their flows
– Adding excessive nutrients to lakes from
human activities can disrupt their ecosystems,
and prevention of such pollution is more
effective and less costly than cleaning it up
© Cengage Learning 2015
Streams Can Cleanse Themselves, If We
Do Not Overload Them
• Dilution
• Biodegradation of wastes by bacteria
takes time
• Oxygen sag curve
– Breakdown of biodegradable wastes by
bacteria depletes oxygen
© Cengage Learning 2015
Point source
© Cengage Learning 2015
Fig. 20-6, p. 549
Stream Pollution in More-Developed
Countries
• 1970s – water pollution control laws
• Successful water clean-up stories
– Ohio Cuyahoga River, U.S.
– Thames River, Great Britain
• Contamination of toxic inorganic and
organic chemicals by industries and mines
© Cengage Learning 2015
Stream Pollution in Less-Developed
Countries
• Half of the world’s 500 major rivers are
polluted
– Untreated sewage
– Industrial waste
• Water often used for human activities
© Cengage Learning 2015
© Cengage Learning 2015
Fig. 20-7, p. 550
Too Little Mixing and Low Water Flow
Makes Lakes Vulnerable to Water Pollution
• Less effective at diluting pollutants than
streams
– Stratified layers
• Little vertical mixing
– Little of no water flow
– Can take up to 100 years to change the water
in a lake
– Biological magnification of pollutants
© Cengage Learning 2015
Cultural Eutrophication Is Too Much
of a Good Thing
• Eutrophication
– Natural enrichment of a shallow lake, estuary,
or slow-moving stream
– Caused by runoff into lake that contains
nitrates and phosphates
• Oligotrophic lake
– Low nutrients; clear water
© Cengage Learning 2015
Cultural Eutrophication Is Too Much
of a Good Thing (cont’d.)
• Cultural eutrophication
– Nitrates and phosphates from human sources
– Farms, feedlots, streets, parking lots
– Fertilized lawns, mining sites, sewage plants
• During hot weather or droughts
– Algal blooms
– Increased bacteria; anaerobic bacteria
– More nutrients
© Cengage Learning 2015
Cultural Eutrophication Is Too Much
of a Good Thing (cont’d.)
• Prevent or reduce cultural eutrophication
– Remove nitrates and phosphates
– Diversion of lake water
• Clean up lakes
– Remove excess weeds
– Use herbicides and algaecides
– Pump in air
© Cengage Learning 2015
© Cengage Learning 2015
Fig. 20-8, p. 551
Revisiting The Gulf of Mexico: An Extreme
Case of Cultural Eutrophication
• Nitrates discharged from the Mississippi
have nearly tripled since 1950
– Nitrogen cycle disrupted
– Blue-green algae blooms
• Flood-control along the Mississippi
– Flow faster; increase sediment pollution
• Fish kills
© Cengage Learning 2015
Case Study: Pollution in the Great Lakes
• 1960s – many areas with cultural
eutrophication
• 1972 – Canada and the United States
Great Lakes pollution control program
– Decreased algal blooms
– Increased dissolved oxygen
– Increased fishing catches
– Better sewage treatment plants
© Cengage Learning 2015
Case Study: Pollution in the Great Lakes
(cont’d.)
• Pollution control program (cont’d.)
– Fewer industrial wastes
– Bans on phosphate-containing household
products
• Problems still exist
– Raw sewage and biological pollution
– Nonpoint runoff of pesticides and fertilizers
– Atmospheric deposition of pesticides and Hg
© Cengage Learning 2015
Case Study: Pollution in the Great Lakes
(cont’d.)
• Continuing problems
– Urban sprawl and runoff
– Biological pollution
• Zebra mussels
– Atmospheric deposition of pollutants
© Cengage Learning 2015
© Cengage Learning 2015
Fig. 20-11, p. 553
20-3 What Are the Major Pollution
Problems Affecting Groundwater?
• Chemicals used in agriculture, industry,
transportation, and homes can spill and
leak into groundwater and make it
undrinkable
– There are both simple ways and complex
ways to purify groundwater used as a source
of drinking water, but protecting it through
pollution prevention is the least expensive and
most effective strategy
© Cengage Learning 2015
Ground Water Cannot Cleanse Itself Very
Well
• Source of drinking water for about half of
the U.S. population
• Common pollutants
– Fertilizers and pesticides
– Gasoline
– Organic solvents
– Fracking
• Pollutants dispersed in a widening plume
© Cengage Learning 2015
Ground Water Cannot Cleanse Itself Very
Well (cont’d.)
• Slower chemical reactions in groundwater
due to:
– Slow flow – contaminants not diluted
– Less dissolved oxygen
– Fewer decomposing bacteria
– Low temperatures
© Cengage Learning 2015
Polluted air
Hazardous
waste
injection well
Pesticides
and fertilizers
Coal strip
mine runoff
Deicing
road salt
Pumping
well
Waste lagoon
Gasoline
station
Water
pumping well
Buried gasoline
and solvent
tanks
Cesspool,
septic
tank
Sewer
Landfill
Leakage
from
faulty
casing
Discharge
Accidental
spills
Freshwater
aquifer
Groundwater
flow
© Cengage Learning 2015
Fig. 20-12, p. 554
Groundwater Pollution Is a Serious Hidden
Threat in Some Areas
• China – 90% of urban aquifers are
contaminated or overexploited
• U.S. – FDA reports of toxins found in many
aquifers
• Nitrate ions
– Can turn into cancer causing chemicals
• Slowly degrading wastes
• Non-degradable wastes
© Cengage Learning 2015
Case Study: Arsenic in Drinking Water
• Rocks rich in arsenic can contaminate
wells
• Long-term exposure can lead to:
– Skin, lung, bladder cancer
• Treatment
– Nanoparticles of rust
© Cengage Learning 2015
There Are Many Ways to Purify
Drinking Water
• Reservoirs and purification plants
• Process sewer water to drinking water
• Expose clear plastic containers to sunlight
(UV)
• The LifeStraw
• PUR – chlorine and iron sulfate powder
© Cengage Learning 2015
Case Study: Is Bottled Water a Good
Option?
• Bottled water can be useful but expensive
• The U.S. has some of the world’s cleanest
drinking water
• Bottled water less regulated than tap water
• Use of bottled water can create
environmental problems
© Cengage Learning 2015
Using Laws to Protect Drinking Water
Quality
• 1974 – U.S. Safe Drinking Water Act
– Sets maximum contaminant levels for any
pollutants that affect human health
• Health scientists
– Strengthen the law
• Water-polluting companies
– Weaken the law
© Cengage Learning 2015
20-4 What Are the Major Water Pollution
Problems Affecting Oceans?
• Most ocean pollution originates on land
and includes:
– Oil and other toxic chemicals
– Solid waste, which threaten fish and wildlife
and disrupt marine ecosystems
• Key to protecting the oceans
– Reduce the flow of pollution from land and air
and from streams emptying into ocean waters
© Cengage Learning 2015
Ocean Pollution Is a Growing and Poorly
Understood Problem
• Municipal sewage from less-developed
countries are often dumped into oceans
without treatment
• Deeper ocean waters
– Dilution
– Dispersion
– Degradation
© Cengage Learning 2015
Ocean Pollution Is a Growing and Poorly
Understood Problem (cont’d.)
• U.S. coastal waters
– Raw sewage – viruses
– Sewage and agricultural runoff: NO3- and
PO43– Harmful algal blooms
– Oxygen-depleted zones
© Cengage Learning 2015
Industry
Nitrogen oxides
from autos and
smokestacks, toxic
chemicals, and
heavy metals in
effluents flow into
bays and estuaries.
Cities
Toxic metals and oil
from streets and
parking lots pollute
waters; sewage
adds nitrogen and
phosphorus.
Urban sprawl
Bacteria and viruses from
sewers and septic tanks
contaminate shellfish beds
and close beaches; runoff of
fertilizer from lawns adds
nitrogen and phosphorus.
Construction sites
Sediments are washed into
waterways, choking fish and
plants, clouding waters, and
blocking sunlight.
Farms
Runoff of pesticides,
manure, and fertilizers adds
toxins and excess nitrogen
and phosphorus.
Closed
shellfish beds
Closed
beach
Oxygen-depleted
zone
Red tides
Excess nitrogen
causes explosive
growth of toxic
microscopic
algae, poisoning fish
and marine mammals.
Toxic sediments
Chemicals and toxic metals
contaminate shellfish beds,
kill spawning fish, and
accumulate in the tissues
of bottom feeders.
Oxygen-depleted zone
Sedimentation and algae
overgrowth reduce sunlight,
kill beneficial sea grasses,
use up oxygen, and degrade
habitat.
Healthy zone
Clear, oxygen-rich waters
promote growth of
plankton and sea grasses,
and support fish.
Fig. 20-15, p. 559
Case Study: Ocean Garbage Patches:
There Is No Away
• North Pacific Garbage Patch
– Two rotating gyres
– On or just beneath the water surface
• Tiny plastic pieces harmful to wildlife
• No practical way to clean up
© Cengage Learning 2015
Canada
Russia
Alaska
United
States
China
Japan
Hawaii
PACIFIC OCEAN
© Cengage Learning 2015
Fig. 20-17, p. 560
Ocean Pollution from Oil
• Crude and refined petroleum
– Highly disruptive pollutants
• Largest source of ocean oil pollution
– Urban and industrial runoff from land
• 1989 – Exxon Valdez, oil tanker
• 2010 – BP Deepwater Horizon in the Gulf
of Mexico
© Cengage Learning 2015
Ocean Pollution from Oil (cont’d.)
• Volatile organic hydrocarbons
– Kill many aquatic organisms
• Tar-like globs on the ocean’s surface
– Coat animals
• Heavy oil components sink
– Affect the bottom dwellers
© Cengage Learning 2015
Ocean Pollution from Oil (cont’d.)
• Faster recovery in warm water with rapid
currents
– In cold, calm waters recovery can take
decades
• Methods of preventing oil spills
– Double hulls
© Cengage Learning 2015
© Cengage Learning 2015
Fig. 20-19, p. 561
Case Study: The BP Deepwater Horizon
Oil-Rig Spill
• Spill from deep-sea oil drilling – 1 mile
deep
– Released 4.9 million barrels of crude oil
– Contaminated vast areas of coastline
– Caused by equipment failure and poor
decisions
• Government developed new standards for
offshore drilling procedures
© Cengage Learning 2015
20-5 How Can We Deal with Water
Pollution?
• Reducing water pollution requires that we:
– Prevent it
– Work with nature to treat sewage
– Use natural resources far more efficiently
© Cengage Learning 2015
Reducing Ocean Water Pollution
• Reduce flow of pollution from land
– Land-use
– Air pollution
– Linked to energy and climate policy
© Cengage Learning 2015
Solutions
Coastal Water Pollution
Prevention
Separate sewage
Ban dumping of
and storm water
wastes and
lines
sewage by ships
in coastal waters
Require secondary
treatment of
coastal sewage
Strictly regulate
coastal
development,
oil drilling, and
oil shipping
Use wetlands and
other natural
methods to treat
sewage
Require
double hulls
for oil tankers
Cleanup
Improve oil-spill
cleanup
capabilities
Use nanoparticles
on sewage and oil
spills to dissolve
the oil or sewage
(still under
development)
© Cengage Learning 2015
Fig. 20-21, p. 563
Reducing Surface Water Pollution from
Nonpoint Sources
• Agriculture
– Reduce erosion
– Reduce the amount of fertilizers
– Plant buffer zones of vegetation
– Use organic farming techniques
– Use pesticides prudently
– Institute tougher pollution regulations for
livestock operations
© Cengage Learning 2015
Case Study: The U.S. Experience with
Reducing Point-Source Pollution
• 1972 – Clean Water Act
• 1987 – Water Quality Act
• Experimenting with a discharge trading
policy that uses market forces
• What are some achievements of the Clean
Water Act?
© Cengage Learning 2015
Sewage Treatment Reduces Water
Pollution
• How do septic tank systems work?
• Wastewater or sewage treatment plants
– Primary sewage treatment
• Physical process
– Secondary sewage treatment
• Biological process with bacteria
– Tertiary or advance sewage treatment
• Special filtering processes
• Bleaching, chlorination
© Cengage Learning 2015
Sewage Treatment Reduces Water
Pollution (cont’d.)
• Many cities violate federal standards for
sewage treatment plants
– Federal law requires primary and secondary
treatment
• Exemptions from secondary treatment
• There are health risks of swimming in
water with blended sewage wastes
© Cengage Learning 2015
Manhole cover
(for cleanout)
Septic tank
Gas
Distribution box
Scum
Wastewater
Sludge
Drain field
(gravel or
crushed stone)
Vent pipe
Perforated pipe
© Cengage Learning 2015
Fig. 20-23, p. 565
Primary
Bar screen Grit chamber
Raw sewage
from sewers
Secondary
Settling tank
Aeration tank
Settling tank
Sludge
Activated sludge
Chlorine
disinfection tank
To river,
lake, or
ocean
(kills bacteria)
Air pump
Sludge digester
Sludge drying bed
Disposed of
in landfill or
ocean or
applied to
cropland,
pasture, or
rangeland
© Cengage Learning 2015
Fig. 20-24, p. 566
We Can Improve Conventional Sewage
Treatment
• Remove toxic wastes before water goes to
the municipal sewage treatment plants
• Reduce or eliminate use and waste of
toxic chemicals
• Use composting toilet systems
• Wetland-based sewage treatment systems
– Work with nature
© Cengage Learning 2015
There Are Sustainable Ways to Reduce
and Prevent Water Pollution
• Developed countries
– Bottom-up political pressure to pass laws
• Developing countries
– Little has been done to reduce water pollution
– China
• Small sewage treatment plants
• How can we avoid producing water
pollutants in the first place?
© Cengage Learning 2015
© Cengage Learning 2015
Fig. 20-26, p. 568
© Cengage Learning 2015
Fig. 20-27, p. 570
Three Big Ideas
• There are a number of ways to purify
drinking water, but the most effective and
least costly strategy is pollution prevention
• The key to protecting the oceans is to
reduce the flow of pollution from:
– Land and air
– Streams emptying into ocean waters
© Cengage Learning 2015
Three Big Ideas
• Reducing water pollution requires that we:
– Prevent it
– Work with nature in treating sewage
– Use natural resources far more efficiently
© Cengage Learning 2015
Tying It All Together: Dead Zones and
Sustainability
• Dead zones disrupt ecological interactions
between species in river and coastal
systems
• We can use solar energy to purify water
and reduce waste
• We can use natural nutrient cycles to
purify water
© Cengage Learning 2015