MODULE 01: INTRODUCTION TO ENVIRONMENTAL SCIENCE AND ENGINEERING
OBJECTIVES
1. Explain the importance of environmental science,
2. Differentiate environmental science with environmental engineering, and
3. Identify the environmental concerns that need to be addressed.
1. THE SCIENCE OF ENVIRONMENT
● The science of the environment is a multi-disciplinary science.
● It comprises various branches of studies like chemistry, physics, medical
science, life science, agriculture, public health, sanitary engineering etc.
● It is the science of physical phenomena in the environment
● It studies the sources, reactions, transport, effect and fate of physical and
biological species in the air, water, and soil and the effect of human activity
upon these.
ENVIRONMENT
● Environment is the surrounding external conditions influencing development
or growth of people, animals or plants; living or working conditions etc.
● It is the interaction between biotic or living organisms (e.g., humans, animals,
plants) and abiotic or non-living organisms (e.g., Earth, wind, water, Sun).
● It can be concluded that the environment comprises various types of forces
such as physical, intellectual, economic, political, cultural, social, moral, and
emotional.
● Environment is the sum total of all the external forces, influences and
conditions, which affect the life, nature, behavior and the growth, development
and maturation of living organisms.
● The term environment is used to describe, in the aggregate, all the external
forces, influences and conditions, which affect life, nature, behavior and the
growth, development and maturity of living organisms.
1.1. Scopes of Environment
The scope of the environment includes:
1.1.1. The Atmosphere
● Etymology: Greek words: (1) “atmos” – vapor or air ; (2) “sphere” – ball,
globe
● The atmosphere implies the protective blanket of gases, surrounding the
earth:
● It sustains life on the earth.
● It saves it from the hostile environment of outer space.
● It absorbs most of the cosmic rays from outer space and a major portion of
the electromagnetic radiation from the sun.
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● It transmits only ultraviolet, visible, near infrared radiation (300 to 2500
nanometers) and radio waves. (0.14 to 40 meters) while filtering out
tissue-damaging ultraviolet waves below about 300 nanometers (nm).
● It comprises 78% nitrogen, 21% oxygen, and smaller amounts of argon,
carbon dioxide, helium, and neon.
● Contaminants in the air include smoke, toxic gasses, dust, ash from
volcanoes, and salt
1.1.1.1. Layers of the Atmosphere
1. Troposphere
▪ Reaches 12 km from the Earth’s surface
▪ The thinnest layer of the atmosphere
▪ Comprises roughly 80% of the weight of the atmosphere
2. Stratosphere
▪ Reaches 50 km from the Earth’s surface
▪ Where the Ozone Layer is located
▪ Ozone Layer – a protective layer of O3 compounds that prevent
ultraviolet radiation in directly entering the Earth’s surface
3. Mesosphere
▪ Extends between 50 km and 70 km from the Earth’s surface
▪ Coldest layer of the atmosphere
4. Thermosphere
▪ Contains only 0.001% of the gases in the atmosphere
▪ Hottest layer of the atmosphere
▪ Contains the Ionosphere, where aurora phenomena occur
5. Exosphere
▪ Outermost layer of the atmosphere
▪ Extends as far as 6000 miles out into the space
1.1.2. The Hydrosphere
● Etymology: Greek words: (1) “hydro” – water ; (2) “sphere” – ball, globe
● The Hydrosphere comprises all types of water resources: oceans, seas,
lakes, rivers, streams, reservoirs, polar ice caps, glaciers, and groundwater.
● In nature, 97% of the earth’s water supply is in the oceans,
● About 2% of the water resources are locked in the polar icecaps and
glaciers.
● Only about 1% is available as fresh surface water-rivers, lakes, streams,
and groundwater fit to be used for human consumption and other uses.
World’s Water Resources
● About 𝟕𝟏% of the Earth's surface is water-covered. Oceans: ~96.5% of all
Earth's water
● Water also exists: in the air as water vapor, in rivers and lakes, in icecaps
and glaciers, in the ground as soil moisture and in aquifers.
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● The vast majority of water on the Earth's surface is saline water in the
oceans.
● The freshwater resources, such as water falling from the skies and moving
into streams, rivers, lakes, and groundwater, provide people with the
water they need every day to live.
● Water sitting on the surface of the Earth is easy to visualize, and your view
of the water cycle might be that rainfall fills up the rivers and lakes. But,
the unseen water below our feet is critically important to life, also.
● If all of Earth's water (oceans, icecaps and glaciers, lakes, rivers,
groundwater, and water in the atmosphere was put into a sphere, then the
diameter of that water ball would be about 860 miles (about 1,385
kilometers). The volume of all water would be about
332.5 𝑚𝑖𝑙𝑙𝑖𝑜𝑛 𝑐𝑢𝑏𝑖𝑐 𝑚𝑖𝑙𝑒𝑠 (𝑚𝑖 3 ),
or
1,386 𝑚𝑖𝑙𝑙𝑖𝑜𝑛 𝑐𝑢𝑏𝑖𝑐 𝑘𝑖𝑙𝑜𝑚𝑒𝑡𝑒𝑟𝑠 (𝑘𝑚3 ). A cubic mile of water equals more
than 1.1 trillion gallons. A cubic kilometer of water equals about 264 billion
gallons (1 trillion liters).
● About 3,100 𝑚𝑖 3 (12,900 𝑘𝑚3 ) of water, mostly in the form of water vapor,
is in the atmosphere at any one time. If it all fell as precipitation at once,
the Earth would be covered with only about 1 inch of water.
● Each day, 280 𝑚𝑖 3 (1,170 𝑘𝑚3 ) of water evaporate or transpire into the
atmosphere.
● Of the freshwater on Earth, much more is stored in the ground than is
available in rivers and lakes. More than 2,000,000 𝑚𝑖 3 (8,400,000 𝑘𝑚3) of
freshwater is stored in the Earth, most within one-half mile of the surface.
● But, if you really want to find freshwater, most is stored in the
7, 000,000 𝑚𝑖 3 (29,200,000 𝑘𝑚3 ) of water found in glaciers and icecaps,
mainly in the Polar Regions and in Greenland.
Water Source
Water
(𝒎𝒊𝟑 )
Oceans, Seas, &
Bays
Ice caps, Glaciers, &
Snow
Groundwater
321,000,000
Fresh
Saline
Volume
Water
(𝒌𝒎𝟑 )
Volume
Percent
of
Freshwater
Percent
of
Total Water
1,338,000,000
--
96.5400
5,773,000
24,064,000
68.70
1.7400
5,614,000
23,400,000
10,530,000
12,870,000
-30.10
1.6900
2,526,000
3,088,000
3,959
71,970
--
0.7600
0.9300
16,500
300,000
0.050
0.860
0.0010
0.0220
42,320
176,400
--
0.0130
Fresh
Saline
21,830
20,490
91,000
85,400
0.260
0.0070
--
0.0060
Atmosphere
Swamp Water
Rivers
Biological Water
3,095
2,752
12,900
11,470
2,120
1,120
0.040
0.030
0.006
0.003
0.0010
0.0008
0.0002
0.0001
Soil Moisture
Ground
Ice
Permafrost
Lakes
&
509
269
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1.1.3. The Lithosphere
● Etymology: Greek words: (1) “lithos” – rock, solid rock ; (2) “sphere” – ball,
globe
● Lithosphere is the outer part of the solid earth.
● It consists of:
1. Crust – both oceanic and continental
2. Outermost layer of the mantle – about 60 miles (100 kilometers) in
thickness
● It consists of minerals occurring in the earth’s crusts and the soil e.g.
minerals, organic matter, air, and water.
1.1.4. The Biosphere
● Etymology: Greek words: (1) “bios” – life or living ; (2) “sphere” – ball,
globe
● Biosphere indicates the realm of living organisms and their interactions
with the environment, via atmosphere, hydrosphere, and lithosphere.
● *** Further discussion on “Ecology.”
1.2. Environmental Science
● Science is systematized knowledge derived from and tested by recognition
and formulation of a problem, collection of data through observation, and
experimentation.
● Social Science deals with the study of people and how they live together.
● Natural Science deals with the study of nature and the physical world. It
includes such diverse disciplines as biology, chemistry, geology, physics, and
environmental science.
● Environmental science in its broadest sense encompasses all the fields of
natural science.
● Environmental Science is defined as the branch of biology focused on the study
of the relationships of the natural world and the relationships between
organisms and their environment.
● It is an interdisciplinary academic field that integrates physical, biological, and
information sciences to the study of environment, and the solution of
environmental problems.
● It is the study of living organisms and how they interact with our environment.
1.3. Environmental Engineering
● Engineering is a profession that applies science and mathematics to make the
properties of matter and sources of energy useful in structures, machines,
products, systems, and processes.
● Environmental Engineering is the application of science and engineering
principles to improve the environment (air, water, and/or land resources), to
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provide healthful water, air, and land for human habitation and for other
organisms, and remediate polluted sites.
● It is the branch of engineering that is concerned with protecting people from
the effects of adverse environmental effects, such as pollution, as well as
improving environmental quality.
● Like many fields of engineering, environmental engineering involves the
planning, design, construction and operation of equipment, systems, and
structures for the benefit of society.
● Environmental engineering is manifested by sound engineering thought and
practice in the solution of problems of
▪ provision of safe, palatable, and ample public water supplies;
▪ the proper disposal of or recycle of wastewater and solid wastes;
▪ the adequate drainage of urban and rural areas for proper sanitation;
▪ the control of water, soil, and atmospheric pollution, and
▪ the social and environmental impacts of these solutions
1.4. Environmental Systems
● Ecosystem is the relationships and interactions of plants and animals with the
water, air, and soil that make up their environment.
● Focuses on
▪ the water resource management system,
▪ the air resource management system, and
▪ the solid waste management system.
● Sustainability - how is ecosystem be maintained in the light of major depletion of
natural resources.
Systems
● an assemblage of parts and their relationship forming a functioning
entirety or whole
● a typical system involves:
▪ Inputs – Ex. H2O, CO2, and sunlight
▪ Processes – Ex. Photosynthesis
▪ Outputs – Ex. O2, glucose
Environmental Systems
● Environmental system is a system (defined above) where life interacts
with the various abiotic components found in the atmosphere.
● Environmental systems also involve the capture, movement, storage,
and use of energy.
● Environmental Systems = Energy Systems
REFERENCES
1. Allaby, M. (2000). “Basics of Environmental Science 2nd Edition.” Taylor &
Francis e-Library
2. Singh, D. K. (2006). “Environmental Science 4th Edition.” New Age
International (P) Ltd., Publishers
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MODULE 02: ECOLOGY
OBJECTIVES
1. Understand the basic principles of ecology
2. Explain the Four Laws of Ecology by Commoner
2. ECOLOGY
• Ecology is the study of the interactions between organisms and their
environments
• It also provides the understanding of underlying environmental issues
• It emphasizes energy flow and chemical cycling among various biotic and
abiotic components
ENVIRONMENT
• It is the interaction between biotic or living organisms (e.g., humans, animals,
plants) and abiotic or non-living organisms (e.g., Earth, wind, water, Sun).
• The abiotic factors in the environment can be classified as:
1. Physical (energy, light, temperature, physical habitat)
2. Chemical (Gases: O2, N2, CO2, etc., Nutrients: NO3, PO4, Ca, K, etc., pH)
2.1. Life’s Different Levels of Organization
1. Organisms
2. Species
- group of organisms resembling one another in appearance, behavior, &
genetic make up
3. Population
- group of individuals belonging to the same species
4. Community
- populations of different species interacting in a given area
5. Ecosystem
- communities and their physical environments considered together
6. Biome
- A geographic area that has a particular climate and is home to a particular
group of plants and animals that have adapted to that specific
environment
7. Biosphere
- the global ecosystem, the sum of all the earth’s ecosystems
- comprises a thin layer of the earth’s surface where life can exist
Atoms → Molecules → Cells → Tissues → Organs → Organ Systems →
Multicellular Organisms
Organisms → Population → Community → Ecosystem → Biomes → Biosphere
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2.2. The Precautionary Principle
• If an action or policy has a suspected risk of causing harm to the environment,
in the absence of scientific consensus that the action or policy is harmful, the
burden of proof that it is not harmful falls on those taking the action.
• Humans need to be concerned with how our actions affect the environment
2.3. Four Laws of Ecology
• Barry Commoner
▪ “a leader among a generation of scientist-activists” (New York Times)
▪ “the greatest environmentalist of the 20th century” (Ralph Nader)
▪ He said that “no permanent environmental solutions are possible.”
▪ “When any environmental issue is pursued to its origin, it reveals an
inescapable truth—that the root cause of the crisis is not to be found in
how men interact with nature, but in how they interact with each other—
that, to solve the environmental crisis we must solve the problems of
poverty, racial injustice, and war.”
▪ Best known for his four “Laws of Ecology”
• Outlined by Commoner in the first chapter of “The Closing Circle”
1. Everything is connected to everything else
2. Everything must go somewhere
3. Nature knows best
4. There is no such thing as free lunch
2.4. Fields of Ecology
1. Organismal ecology
- Studies how an organism’s morphology, physiology and behavior meet the
challenges posed by the environment
2. Population ecology
- Studies the factors that affect how many individuals of a particular species
can live in an area
3. Community ecology
- Deals with the whole array of interacting species in a community
4. Ecosystem ecology
- Emphasizes energy flow and chemical cycling among the various biotic and
abiotic components
5. Landscape ecology
- Deals with arrays of ecosystems and how they are arranged in a geographic
region
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2.5. Climate
• Prevailing weather conditions in a particular area
• Climate is made of: (1) Temperature, (2) Water, (3) Sunlight, and (4) Wind
2.5.1. Factors that Determine Global Climatic Patterns
1. Amount of Sunlight Received
2. Movement of Earth in Space
Midnight Sun in Nordkapp, Norway
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3. Air Circulation
4. Wind Patterns
5. Local Geographic Features
Climate of adjacent terrestrial
environments is moderated by large
bodies of water
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Mountains affect the local temperature,
rainfall and the amount of sunlight
reaching an area
9
6. Seasonality
Thermocline - narrow vertical zone of rapid temperature change
2.6. Elements of Aquatic Ecology
• Plants and animals in their physical and chemical environment make up an
ecosystem. The study of ecosystems is termed ecology. Although we often
draw lines around a specific ecosystem to be able to study it more fully (e.g., a
farm pond) and thereby assume that the system is completely self-contained,
this is obviously not me. One of the tenets of ecology is that “everything is
connected with everything else.”
• Ecosystems exhibit a flow of both energy and nutrients. The original energy
source for nearly all ecosystems is the sun (the only notable exception is
oceanic hydrothermal vent communities, which derive energy from
geothermal activity). Energy flows in only one direction: from the sun and
through each trophic level. Nutrient flow, on the other hand, is cyclic: nutrients
are used by plants to make high-energy molecules that are eventually
decomposed to the original inorganic nutrients, ready to be used again.
• Most ecosystems are sufficiently complex that small changes in plant or animal
populations will not result in long-term damage to the ecosystem. Ecosystems
are constantly changing, even without human intervention, so ecosystem
stability is best defined by its ability to return to its original rate of change
following a disturbance. For example, it is unrealistic to expect to find the exact
same numbers and species of aquatic invertebrates in a “restored” stream
ecosystem as were present before any disturbance. Stream invertebrate
populations vary markedly from year to year, even in undisturbed streams.
Instead, we should look for the return of similar types of invertebrates, in
about the same relative proportion as would be found in undisturbed streams.
• The amount of perturbation that an ecosystem can absorb is called resistance.
Communities dominated by large, long-lived plants (e.g., old growth forests)
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tend to be fairly resistant to perturbation (unless the perturbation is a chain
saw!). Ecosystem resistance is partially based on which species are most
sensitive to the particular disturbance. Even relatively small changes in the
populations of “top of the food chain” predators (including humans) or critical
plant types (e.g., plants that provide irreplaceable habitat) can have a
substantial impact on the structure of the ecosystem. The ongoing attempt to
limit the logging of old-growth forests in the Pacific Northwest is an attempt
to preserve critical habitat for species that depend on old growth, such as the
spotted owl and the marbled murmlet.
• The rate at which the ecosystem recovers from perturbation is called
resilience. Resilient ecosystems are usually populated with species that have
rapid colonization and growth rates. Most aquatic ecosystems are very
resilient (but not particularly resistant). For example, during storm events, the
stream bottom is scoured, removing most of the attached algae that serve as
food for small invertebrates. The algae grow quickly after the storm flow
abates, so the invertebrates do not starve. In contrast, the deep oceanic
ecosystem is extraordinarily fragile, not resilient, and not resistant to
environmental disturbances. This must be considered before the oceans are
used as waste repositories.
• Although inland waters (streams, lakes, wetlands, etc.) tend to be fairly
resilient ecosystems, they are certainly not totally immune to destruction by
outside perturbations. In addition to the direct effect of toxic materials like
metals, pesticides, and synthetic organic compounds, one of the most serious
effects of pollutants on inland waters is depletion of dissolved oxygen. All
higher forms of aquatic life exist only in the presence of oxygen, and most
desirable microbiologic life also requires oxygen. Natural streams and lakes
are usually aerobic. If a watercourse becomes anaerobic, the entire ecology
changes and the water becomes unpleasant and unsafe. The dissolved oxygen
concentration in waterways and the effect of pollutants are closely related to
the concept of decomposition and biodegradation, part of the total energy
transfer system that sustains life.
REFERENCES
1. Allaby, M. (2000). “Basics of Environmental Science 2nd Edition.” Taylor &
Francis e-Library
2. Singh, D. K. (2006). “Environmental Science 4th Edition.” New Age
International (P) Ltd., Publishers
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MODULE 03: ECOSYSTEM
OBJECTIVES
1. Be familiar with the energy and mass flow between trophic levels in the
ecosystem,
2. List the major pathway in carbon, nitrogen, phosphorus, and sulfur cycles,
and
3. Enumerate and explain the influences of humans on the ecosystem.
3. ECOSYSTEM
• Ecology is the study of the interrelationships between plants and animals that
live in a particular physical environment.
• Ecosystem are communities of organisms that interact with one another and
with their physical environment.
• Habitats are the place where a population of organism lives.
• Fundamental Characteristics of the Ecosystem:
▪ Components: (1) Living (biotic) and (2) Nonliving (abiotic)
▪ Processes:
1. Energy Flow
-
transfer of energy from one component of the ecosystem to the
next (1-way flow)
2. Nutrient Cycling
▪
- nutrients and other matter passed on in a cycle
Changes: (1) Dynamic (not static) and (2) Succession, etc.
3.1. Energy and Mass Flow
3.1.1. Sustaining Life on Earth
• One way flow of high quality energy
• The cycling of matter (the earth is a closed system)
• Gravity – causes downward movement of matter
3.1.2. Related Laws of Thermodynamics
1. Law of Conservation of Energy
- energy can neither be created nor destroyed
2. Law of Entropy
- energy spontaneously disperses from being localized to becoming
spread out if it is not hindered from doing so
3.1.3. Trophic Structures
• Trophic structures pertains to feeding relationships within the boundaries
of ecosystems
• They determine the paths of energy flow and nutrient cycling
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•
•
•
One of the most important species interactions is who eats whom
Matter and energy move through the community
Trophic levels also refers to the rank in the feeding hierarchy in an
ecosystem
Biospher
Carbon
cycle
Phosphorus
cycle
Nitrogen
cycle
Water
cycle
Oxygen
cycle
Heat in the environment
Heat
Heat
Heat
Five Trophic Structures
1. Producers
- Autotrophs (“self-feeders”) = organisms that capture solar
energy for photosynthesis to produce sugars; mostly
photosynthetic
• Green Plants, cyanobacteria, algae
- Chemosynthetic bacteria use the geothermal energy in hot
springs or deep-sea vents to produce their food
2. Primary Consumers (Heterotrophs)
- Herbivores that consume the producers (plants)
• Deer, grasshoppers
3. Secondary Consumers (Heterotrophs)
- Organisms that prey on primary consumers or herbivores
- Carnivores consume meat
• Wolves, rodents
4. Tertiary Consumers (Heterotrophs)
- Predators at the highest trophic level
- Consume secondary consumers
- Are also carnivores
• Hawks, owls
- Omnivores – consumers that eat both plants and animals
5. Detritivores and Decomposers
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-
Organisms that consume nonliving organic matter
Enrich soils and/or recycle nutrients found in dead organisms
Detritivores - scavenge waste products or dead bodies
• Millipedes
Decomposers - break down leaf litter and other non-living
material
• Fungi, bacteria
• Enhance topsoil and recycle nutrients
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Abiotic chemicals
(carbon dioxide,
oxygen, nitrogen,
minerals)
Heat
Heat
Solar
energy
Heat
Producers
(plants)
Decomposers
(bacteria, fungus)
Consumers
(herbivores,
carnivores)
Heat
Heat
Decomposers
Detritus feeders
Longhorned
beetle
holes
Bark
beetle
engraving
Carpenter
ant
galleries
Termite and
carpenter
ant work
Dry rot
fungus
Mushroom
Wood reduced to powder
Time
progression
Powder broken down by decomposers into plant nutrients in soil
3.1.4. Food Chains and Food Webs
• Food chain = the relationship of how energy is transferred up the trophic
levels
• Food web = a visual map of feeding relationships and energy flow
• Includes many different organisms at all the various levels
• Greatly simplified; leaves out the majority of species
• KEY: There is little if no matter waste in natural ecosystems!
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First Trophic
Level
Producers
Second Trophic
Level
(plants)
Heat
Heat
Primary
consumers
(herbivores)
Heat
Fourth Trophic
Third
Level
Trophic
Secondary
Tertiary
consumers
consumers
(carnivores (top carnivores)
Heat
Solar
energy
Heat
•
•
•
Heat
Detritivores
(decomposers and detritus feeders)
Heat
Food chains/webs show how matter and energy move from one organism
to another through an ecosystem
Each trophic level contains a certain amount of biomass (dry weight of all
organic matter)
Ecological Efficiency: The % of usable energy transferred as biomass from
one trophic level to the next (ranges from 5-20% in most ecosystems, use
10% as a rule of thumb)
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3.1.5. Pyramids of Energy and Matter
• Pyramid of Energy Flow
• Pyramid of Biomass
Heat
Tertiary
consumers
(human)
Secondary
consumers
(perch)
100
10,000
Usable energy
Available at
Each tropic level
Decomposers
Heat
10
1,000
Heat
Primary
consumers
(zooplankton
Heat
Heat
Producers
(phytoplankton)
Examples:
A deer eats 25 kg of herbaceous material per day. The herbaceous matter is
approximately 20% dry matter (DM) and has an energy content of 10 MJ/kg
of DM. Of the total energy ingested per day, 25% is excreted as undigested
material. Of the 75% that is digested, 80% is lost to metabolic waste products
and heat. The remaining 20% is converted to body tissue. How many
megajoules are converted to body tissue on a daily basis? Calculate the
percentage of energy consumed that is converted to body tissue.
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3.2. Nutrient Cycle
• The basic elements of which all organisms are composed are: (1) Carbon, (2)
Nitrogen, (3) Phosphorus, (4) Sulfur, (5) Oxygen, and (6) Hydrogen.
3.2.1. Carbon Cycle
• Can be stored in five major areas:
1. Living and dead organisms
2. Atmosphere (carbon dioxide)
3. Organic matter in soil
4. Lithosphere as fossil fuels and rock deposits
5. Oceans as dissolved CO2 and shells
• Carbon is shuttled between organisms through photosynthesis and
respiration
• Consumers must acquire their carbon from producers in order to be utilized
for cellular respiration
Estimated Amounts in Major Storage of Carbon on the Earth
Sink
Amounts in Billions of Metric
Tons
Atmosphere
766
Soil Organic Matter
1500-1600
Ocean
38,000-40,000
Marine sediments and sedimentary
66,000,000 to 100,000,000
rocks
Terrestrial plants
540-610
Fossil Fuel Deposits
4000
•
•
•
Reservoirs: atmosphere (CO2), fossil fuels, organic matters
Assimilation: photosynthesis, animal consumption
Release: respiration; decomposition; combustion
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3.2.2. Nitrogen Cycle
• Atmosphere is about 78% nitrogen but not in a usable form
• Nitrogen is the most important element for all living organisms by the
synthesis of Amino acids, proteins, enzymes, etc.
• Nitrogen Cycle is the circulation or cyclic movement of Nitrogen from the
atmosphere (physical or abiotic component) to soil (Biotic component) and
back into the atmosphere.
• Nitrogen is a vital component of amino acids in proteins and nucleic acids
1. NITROGEN FIXATION
- reduction of atmospheric nitrogen (N2) to ammonia (NH3)
- N2 fixers – Rhizobium & Cyanobacteria (also by lightning)
- All organisms depend on this process for nitrogen
2. NITRIFICATION
- oxidation of ammonia (NH4+) to nitrite (NO2-) (e.g. Nitrosomonas)
and then to nitrate (NO3-) (e.g. Nitrobacter)
3. DENITRIFICATION
- converts nitrate (NO3-) to atmospheric nitrogen (N2) (e.g.
Pseudomonas)
4. AMMONIFICATION
- decomposition of organic nitrogen back into ammonium
- carried out by decomposers (e.g. bacteria and fungi)
- recycles large amounts of nitrogen to the soil
• Reservoirs: atmosphere; soil
• Assimilation: plant absorption; animal consumption
• Release: denitrification; detrivorous bacteria
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3.2.3. Phosphorus Cycle
• Phosphorus – a major
component of nucleic acids,
phospholipids and ATP
• Occurs only as inorganic
phosphate to soil
• Weathering of rocks adds
phosphate to soil
• Absorbed by plants into
molecules
• Transferred to consumers
• Added back to soil by
excretion
and
decomposition
• Also leaches into water
table over time
•
•
•
Reservoir: rocks
Assimilation: plants from soil; animals eating plants
Release: decomposition; excretion
3.2.4. Sulfur Cycle
3.2.5. Carbon Cycle
• Carbon is shuttled between organisms through photosynthesis and
respiration
• Consumers must acquire their carbon from producers in order to be utilized
for cellular respiration
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3.3. Human Influences in the Ecosystem
• Influences on Biodiversity
▪ Deforestation
- Deforestation is the permanent removal of trees to make room for
something besides forest. This can include clearing the land for
agriculture or grazing, or using the timber for fuel, construction or
manufacturing.
- Deforestation, clearance, clearcutting, or clearing is the removal of a
forest or stand of trees from land that is then converted to non-forest
use. Deforestation can involve conversion of forest land to farms,
ranches, or urban use. The most concentrated deforestation occurs in
tropical rainforests.
▪ Desertification
- Desertification is a type of land degradation in drylands in which
biological productivity is lost due to natural processes or induced by
human activities whereby fertile areas become increasingly arid.
▪ Global Warming
- Global warming is the long-term heating of Earth's climate system
observed since the pre-industrial period (between 1850 and 1900) due
to human activities, primarily fossil fuel burning, which increases heattrapping greenhouse gas levels in Earth's atmosphere.
- Climate change includes both global warming driven by human
emissions of greenhouse gases and the resulting large-scale shifts in
weather patterns.
▪ Invasive Species
- An invasive species can be any kind of living organism—an amphibian
(like the cane toad), plant, insect, fish, fungus, bacteria, or even an
organism's seeds or eggs—that is not native to an ecosystem and
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▪
•
causes harm. They can harm the environment, the economy, or even
human health.
- An invasive species is an introduced organism that negatively alters its
new environment. Although their spread can have beneficial aspects,
invasive species adversely affect the invaded habitats and bioregions,
causing ecological, environmental, and/or economic damage.
Overharvesting
- Overharvesting, also called overexploitation, refers to harvesting a
renewable resource to the point of diminishing returns. Ecologists use
the term to describe populations that are harvested at a rate that is
unsustainable, given their natural rates of mortality and capacities for
reproduction.
The ever-increasing human population has intruded into the dynamics of most
ecosystems through human activities or technology
1. Increased agricultural outputs may lead to BIOLOGICAL MAGNIFICATION
of certain toxic substances
• Effects of Agriculture on Nutrient Cycling
▪ Intrusions into cycling of nutrients
▪ Overharvesting of natural populations for human consumption
▪ Introduction of toxic compounds such as pesticides
▪ Can lead to Biological Magnification
BIOLOGICAL MAGNIFICATION
• Biological Magnification pertains to
the process where toxins are
concentrated at each successive
trophic level in the food chain
• Exemplified
by
DDT
(dichlorodiphenyltrichloroethane),
known nerve poison agent against
insect pests
• Makes egg shells of birds very weak
and brittle
• Affects the nervous system in
humans
2. Pollutants in lakes and rivers cause
CULTURAL EUTROPHICATION
• Increase of inorganic nutrient
levels in waters such as lakes due
to sewage, factory wastes, livestock runoff, and fertilizer leaching
• Results in explosive growth of photosynthetic organisms such as
ALGAL BLOOMS
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•
•
RED TIDE – a type of algal bloom caused by dinoflagellates
As these producers die, metabolism of detritivores consumes all the
oxygen in the water and many species die as a result
3. Greater carbon emissions lead to the GREENHOUSE EFFECT
• Carbon dioxide emissions have caused atmospheric CO2
concentrations to increase 14% since 1958
• Increase is due to combustion of fossil fuels and burning of wood
removed by deforestation
4. Proliferation of CFCs deplete the OZONE LAYER
• a protective layer made up of O3 in the stratosphere that absorbs
ultraviolet radiation
• O3 is reduced to atmospheric O2 by CFCs (chlorofluorocarbons)
Ozone Hole over Antartica
September 10, 2000
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MODULE 04: POPULATION DYNAMICS
OBJECTIVES
1. Understand and model the growth shown in bacterial, animal, and human
population.
4. POPULATION DYNAMICS
• Population dynamics is the study of the changes in the numbers and
composition of individuals in a population within a study unit and the factor
that affect these numbers. The study area can be biological, geographical,
political or an engineered area.
• As environmental scientists and engineers, evaluating population dynamics is
critical to
1) understanding how environmental perturbations affect population,
2) predicting human populations so as to determine water resource needs,
3) predicting bacterial population in engineered systems, and
4) using populations as indicators of environmental quality.
• Factors that cause populations to change may be related to or independent of
the number of organisms in the study area. These factors can be classified as
either density-dependent or density-independent.
• Population Density (or Density) refers the number of organisms per unit area
or volume.
• Density-dependent factors are, as implied, a function of density.
• Density-independent factors are those factors that act on a population
independent on the size of the population.
4.1. Law of Population Growth
• States that the rate at which a certain quantity increases or decreases is
proportional to the amount present at any time, 𝒕. This Law is called the
Compound Interest Law by Lord Kelvin.
𝒅𝑷
= 𝒌𝑷
𝒅𝒕
where:
𝒅𝑷
= rate of change of the population
𝒅𝒕
𝑷 = number of inhabitants at any time, 𝒕
𝒌 = constant of proportionality
4.1.1. Bacterial Growth Population
• The dynamics of bacterial population are relevant to environmental scientists
and engineers because of their importance in wastewater treatment and water
quality.
• The major groups of requirements necessary for bacterial growth are as
follows:
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▪
▪
•
A terminal electron acceptor
Macronutrients
- Carbon to build cells
- Nitrogen to build cells
- Phosphorus for ATP (energy carrier) and DNA
- Trace metals
- Vitamins are required by some bacteria
▪ Appropriate environment
- Moisture, Temperature, and pH
The population of bacteria (P) after the nth generation is given by the
following expression:
𝑷 = 𝑷𝑶 (𝟐)𝒏
where 𝑷𝑶 is the initial population at the end of the accelerated growth phase
and 𝒏 is the number of generations.
Problem 1:
If the initial density of bacteria is 104 cells per liter at the end of the accelerated
growth phase, what is the number of bacteria after 25 generations?
4.2. Population Dynamics
4.2.1. Basic Components of Population Dynamics
• Population dynamics involve five basic components to which all changes in
population can be related: (1) birth, (2) death, (3) gender ratio, (4) age
structure, and (5) dispersal.
1. Birth
• A number of components affect a population’s birth rate:
▪ the amount and quantity of food,
▪ age at first reproduction,
▪ the birth interval, and
▪ the average number of young born per pregnancy.
2. Death
• Death, or mortality, rate is defined as the number of animals that
die per unit time divided by the number of animals alive at the
beginning of that time period.
3. Gender Ratio
• Gender ratio is the proportion of males to females within
population. The mating system (monogamous vs. polygamous)
will greatly affect population)
4. Age Structure
• Age structure will affect population dynamics. This is because of
age-specific mortality and pregnancy rates.
5. Dispersal
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•
Dispersal is defined as the movement of animal from the location
of its birth to a new area where it lives and reproduces. Dispersal
usually does not occur until the animal is an adult, and males are
usually the gender to disperse.
4.2.2. Animal Population Dynamics
Resources necessary for population growth are unlimited:
𝑵(𝒕+𝟏)
= 𝝀 = 𝒆𝒓
𝑵(𝒕)
where
𝑵(𝒕+𝟏) and 𝑵(𝒕) = population after 𝒕 and 𝒕 + 𝟏 years, respectively
𝒓
= the specific growth rate (net new organism per unit time)
Resources are limited:
𝑲𝑵𝟎
𝑵𝟎 + (𝑲 − 𝑵𝟎 )𝒆−𝒓𝒕
𝑲 is the carrying capacity, the numbers of individuals an area can support.
𝑵𝟎 is the population at time 𝒕 = 𝟎 years
𝑵(𝒕) =
Problem 2:
Assume that the population of the greater roadrunner in the Guadelope Desert
was 𝟐𝟎𝟎 per hectare at the beginning of 1999. If the carrying capacity, 𝑲, is 𝟔𝟎𝟎
and 𝒓 = 𝟎. 𝟐𝟓/𝒚𝒆𝒂𝒓, what is the number of roadrunners one, five, and then ten
years later? What’ll happen when the number of roadrunner is equal to the
carrying capacity?
4.2.3. Human Population Dynamics
• Predicting the dynamics of human population is important to
environmental engineers because it is the basis for the determination of
design capacity for municipal and wastewater treatment systems and for
water reservoirs.
• Population predictions are also important in the development of resources
and pollutant management plans.
• Human population dynamics also depend on birth, death, gender ratio, age
structure, and dispersal.
• In human populations, dispersal is referred to as an immigration and
emigration.
• Assuming an exponential growth rate, the population can be predicted
using the equation:
𝑷(𝒕) = 𝑷𝟎 𝒆𝒓𝒕
where
𝑷(𝒕) = the population at time, 𝒕
𝑷𝑶 = population at time, 𝒕 = 𝟎
𝒓
= rate of growth
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•
𝒕
= time
The growth rate can be determined as a function of birth rate (𝒃), death
rate (𝒅), immigration rate (𝒊), and emigration rate (𝒎):
𝒓=𝒃−𝒅+𝒊−𝒎
where the rates are all expressed as some value per unit time.
Problem 3:
A population of humanoids on the island of Huroth on the Planet Szacak has a net
birth rate (𝒃) of 𝟏. 𝟎 individuals / (individual—year) and a net death rate (𝒅) of
𝟎. 𝟗 individuals / (individual—year). Assume that the net immigration rate is
equal to the net emigration rate. (a) How many years are required for the
population to double? (b) In year zero, the population on the island is 𝟖𝟓, what is
the population 𝟓𝟎 years later?
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MODULE 05: WATER POLLUTION
OBJECTIVES
1. Enumerate and differentiate the various sources and types of water
pollutants,
2. Be familiar on the different measures of the Biochemical Oxygen Demand
(BOD), and
3. Explain and model the effect of oxygen-demanding wastes on flowing water
such as rivers.
5. WATER POLLUTION
Although people intuitively relate filth to disease, the transmission of disease by
pathogenic organisms in polluted water was not recognized until the middle of
the nineteenth century. Until recently, water pollution was viewed primarily as a
threat to human health because of the transmission of bacterial and viral
waterborne diseases. In less developed countries, and in almost any country in
time of war, waterborne diseases remain a major public health threat.
5.1. Sources of Water Pollutants
There are two general sources of water pollutants:
5.1.1. Point Sources
• Point sources of pollution occur when harmful substances are emitted directly
into a body of water from a pipeline or sewer.
• Domestic sewage consists of wastes from homes, schools, office buildings, and
stores.
• Industrial wastewater means process and non-process wastewater from
manufacturing, commercial, mining, and silvicultural facilities, or activities,
including the runoff and leachate from areas that receive pollutants associated
with industrial or commercial storage, handling or processing, and all other
wastewater not otherwise defined as domestic wastewater.
• Municipal sewage includes domestic sewage along with any industrial wastes
that are permitted to be discharged into the sanitary sewers.
• In general, point source pollution can be reduced or eliminated through waste
minimization and proper wastewater treatment prior to discharge to a natural
water body.
5.1.2. Non-Point Sources
• Nonpoint source delivers pollutants indirectly by passing through the
continents.
• Much of nonpoint source occurs during rainstorms, resulting in large flow
rates that make treatment even more difficult.
▪ Agricultural runoff
▪ Urban runoff
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•
Urban storm water runoff (including that from streets, parking lots, golf
courses, and lawns) can transport pollutants such as nitrogen, phosphorus
from fertilizers, herbicides applied to lawns and golf courses, oil, greases,
ethylene glycol (used in antifreeze), and cut grass and other organic debris.
5.2. Types of Water Pollutants
5.2.1. Oxygen-Demanding Materials
Anything that can be oxidized in the receiving water resulting in the consumption
of dissolved molecular oxygen is termed oxygen-demanding material.
This material is usually biodegradable organic matter but also includes inorganic
compounds.
• The consumption of dissolved oxygen (DO) poses a threat to fish and other
higher forms of aquatic life that must have oxygen to live.
• Domestic sewage – human wastes and food residue
• Industrial sewage – food processing and paper industries
• Maximum amount in clean water is about 9 mg/L.
• DO varies with temperature, salinity, elevation, and turbulence (mixing).
• Oxygen demanding substances such as might be discharged from milk
processing plants, breweries, or paper mills, as well as municipal wastewater
treatment plants, compose one of the most important types of pollutants
because these materials decompose in the watercourse and can deplete the
water of dissolved oxygen.
5.2.2. Sediments
Sediments and suspended solids may also be classified as a pollutant.
Sediments consists of mostly inorganic material washed into a stream because of land
cultivation, construction, demolition, and mining operations. Sediments interfere
with fish spawning because they can cover gravel beds and block light penetration,
making food harder to find. Sediments can also damage gill structures directly,
smothering aquatic insects and fishes. Organic sediments can deplete the water of
oxygen, creating anaerobic (without oxygen) conditions, and may create unsightly
conditions and cause unpleasant odors.
5.2.3. Nutrients
Nutrients, mainly nitrogen and phosphorus, can promote accelerated
eutrophication, or the rapid biological “aging” of lakes, streams, and estuaries.
Phosphorus and nitrogen are common pollutants in residential and agricultural
runoff, and are usually associated with plant debris, animal wastes, or fertilizer.
Phosphorus and nitrogen are also common pollutants in municipal wastewater
discharges, even if the wastewater has received conventional treatment. Phosphorus
adheres to inorganic sediments and is transported with sediments in storm runoff.
Nitrogen tends to move with organic matter or is leached from soils and moves with
groundwater.
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5.2.4. Heat
Heat may be classified as a water pollutant when it is caused by heated
industrial effluents or from anthropogenic alterations of stream bank vegetation that
increase the stream temperatures due to solar radiation. Heated discharges may
drastically alter the ecology of a stream or lake. Although localized heating can have
beneficial effects like freeing harbors from ice, the ecological effects are generally
deleterious. Heated effluents lower the solubility of oxygen in the water because gas
solubility in water is inversely proportional to temperature, thereby reducing the
amount of dissolved oxygen available to aerobic (oxygen-dependent) species. Heat
also increases the metabolic rate of aquatic organisms (unless the water temperature
gets too high and kills the organism), which further reduces the amount of dissolved
oxygen because respiration increases.
5.2.5. Municipal Wastewater
Municipal wastewater often contains high concentrations of organic carbon,
phosphorus, and nitrogen, and may contain pesticides, toxic chemicals, salts,
inorganic solids (e.g., silt), and pathogenic bacteria and viruses. A century ago, most
discharges from municipalities received no treatment whatsoever. Since that time,
the population and the pollution contributed by municipal discharge have both
increased, but treatment has increased also.
We define a population equivalent of municipal discharge as equivalent of the
amount of untreated discharge contributed by a given number of people. For example,
if a community of 20,000 people has 50% effective sewage treatment, the population
equivalent is 0.5 x 20,000 or 10,000. Similarly, if an individual contributes 0.2 lb of
solids per day into wastewater, and an industry discharges 1,000 lb/day, the industry
has a population equivalent of 1,000/0.2, or 5,000. The current estimate of the
population equivalent of municipal discharges into U.S. surface water is about 100
million, for a population of nearly 300 million. The contribution of municipal
discharges to water pollution has not decreased significantly in the past several
decades, nor has it significantly increased; at least we are not falling behind.
5.2.6. Agricultural Wastes
Agricultural wastes that flow directly into surface waters have a collective
population equivalent of about two billion. Agricultural wastes are typically high in
nutrients (phosphorus and nitrogen), biodegradable organic carbon, pesticide
residues, and fecal coliform bacteria (bacteria that normally live in the intestinal tract
of warm-blooded animals and indicate contamination by animal wastes). Feedlots
where large numbers of animals are penned into relatively small spaces provide an
efficient way to raise animals for food. They are usually located near slaughterhouses,
and thus near cities. Feedlot drainage (and drainage from intensive poultry
cultivation) creates an extremely high potential for water pollution. Aquaculture has
a similar problem because wastes are concentrated in a relatively small space. Even
relatively low densities of animals can significantly degrade water quality if the
animals can trample the stream bank, or runoff from manure-holding ponds is
allowed to overflow into nearby waterways. Both surface and groundwater pollution
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are common in agricultural regions because of the extensiveness of fertilizer and
pesticide application.
5.2.7. Acids and Bases
Acids and buses from industrial and mining activities can alter the water
quality in a stream or lake to the extent that it kills the aquatic organisms living there
or prevents them from reproducing. Acid mine drainage has polluted surface waters
since the beginning of ore mining. Sulfur-laden water leached from mines, including
old and abandoned mines as well as active ones, contains compounds that oxidize to
sulfuric acid on contact with air. Deposition of atmospheric acids originating in
industrial regions has caused lake acidification throughout vast areas of Canada,
Europe, and Scandinavia.
5.2.8. Synthetic Organics and Pesticides
Synthetic organics and pesticides can adversely affect aquatic ecosystems as
well as making the water unusable for human contact or consumption. These
compounds may come from point source industrial effluents or from nonpoint source
agricultural and urban runoff. The effects of water pollution can be best understood
in the context of an aquatic ecosystem, by studying one or more specific interactions
of pollutants with that ecosystem.
5.3. Biochemical Oxygen Demand (BOD)
Surface water is obviously highly susceptible to contamination. It has
historically been the most convenient sewer for industry and municipalities alike,
while at the same time, it is the source of the majority of our water for all purposes.
One particular category of pollutants, oxygen-demanding wastes, has been such a
pervasive surface-water problem, affecting both moving water and still water, that it
will be given special attention.
When biodegradable organic matter is released into a body of water,
microorganisms, especially bacteria, feed on the wastes, breaking them down into
simpler organic and inorganic substances. When this decomposition takes place in an
aerobic environment—that is, in the presence of oxygen—the process produces nonobjectionable, stable end products such as carbon dioxide (𝐶𝑂2), sulfate (𝑆𝑂4),
orthophosphate (𝑃𝑂4), and nitrate (𝑁𝑂3 ). A simplified representation of aerobic
decomposition is given by the following:
𝑴𝒊𝒄𝒓𝒐𝒐𝒓𝒈𝒂𝒏𝒊𝒔𝒎𝒔
𝑶𝒓𝒈𝒂𝒏𝒊𝒄 𝒎𝒂𝒕𝒕𝒆𝒓 + 𝑶𝟐 →
𝑪𝑶𝟐 + 𝑯𝟐 𝑶 + 𝑵𝒆𝒘 𝒄𝒆𝒍𝒍𝒔
+ 𝑺𝒕𝒂𝒃𝒍𝒆 𝒑𝒓𝒐𝒅𝒖𝒄𝒕𝒔 (𝑵𝑶𝟑 , 𝑷𝑶𝟒 , 𝑺𝑶𝟒 , … )
When insufficient oxygen is available, the resulting anaerobic decomposition
is performed by completely different microorganisms. They produce end products
that can be highly objectionable, including hydrogen sulfide (𝐻2 𝑆), ammonia (𝑁𝐻3 ),
and methane (𝐶𝐻4 ). Anaerobic decomposition can be represented by the following:
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31
𝑴𝒊𝒄𝒓𝒐𝒐𝒓𝒈𝒂𝒏𝒊𝒔𝒎𝒔
𝑶𝒓𝒈𝒂𝒏𝒊𝒄 𝒎𝒂𝒕𝒕𝒆𝒓 →
𝑪𝑶𝟐 + 𝑯𝟐 𝑶 + 𝑵𝒆𝒘 𝒄𝒆𝒍𝒍𝒔
+ 𝑼𝒏𝒔𝒕𝒂𝒃𝒍𝒆 𝒑𝒓𝒐𝒅𝒖𝒄𝒕𝒔 (𝑯𝟐 𝑺, 𝑵𝑯𝟑 , 𝑪𝑯𝟒 , … )
The methane produced is physically stable, biologically degradable, and a
potent greenhouse gas. When emitted from bodies of water, it is often called
swamp gas. It is also generated in the anaerobic environment of landfills, where it
is sometimes collected and used as an energy source.
The amount of oxygen required by microorganisms to oxidize organic wastes
aerobically is called the biochemical oxygen demand (BOD). BOD is most often is
expressed in milligrams of oxygen required per liter of wastewater (mg/L). The
BOD is made up of two parts: the carbonaceous oxygen demand (CBOD) and the
nitrogenous oxygen demand (NBOD). This module will only cover CBOD.
5.3.1. Five Day BOD Test
The total amount of oxygen that will be required for biodegradation is an
important measure of the impact that a given waste will have on the receiving body
of water. While we could imagine a test in which the oxygen required to degrade
completely a sample of waste would be measured, for routine purposes, such a test
would take too long to be practical (at least several weeks would be required). As a
result, it has become standard practice simply to measure and report the oxygen
demand over a shorter, restricted period of five days, realizing that the ultimate
demand may be considerably higher.
The five-day BOD, or (𝐵𝑂𝐷5 ), is the total amount of oxygen consumed by
microorganisms during the first five days of biodegradation. In its simplest form, a
𝐵𝑂𝐷5 test would involve putting a sample of waste into a stoppered bottle and
measuring the concentration of dissolved oxygen (DO) in the sample at the beginning
of the test and again five days later. The difference in DO divided by the volume of
waste would be the five-day BOD. Light must be kept out of the bottle to keep algae
from adding oxygen by photosynthesis, and the bottle is sealed to keep air from
replenishing DO that has been removed by biodegradation. To standardize the
procedure, the test is run at a fixed temperature of 20°C. Since the oxygen demand of
typical waste is several hundred milligrams per liter, and the saturated value of DO
for water at 20°C is only 9.1 mg/L, it is usually necessary to dilute the sample to keep
the final DO above zero. If during the five days, the DO drops to zero, the test is invalid
because more oxygen would have been removed had more been available.
The five-day BOD of a diluted sample is given by:
𝑫𝑶𝒊 − 𝑫𝑶𝒇
𝑩𝑶𝑫𝟓 =
𝑷
where 𝑫𝑶𝒊 is the initial dissolved oxygen (DO) of the diluted wastewater,
𝑫𝑶𝒇 is the dissolved oxygen of the diluted wastewater, 5 days later, and
𝑷 is the dilution fraction.
𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑠𝑡𝑒𝑤𝑎𝑡𝑒𝑟
𝑃=
𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑠𝑡𝑒𝑤𝑎𝑡𝑒𝑟 + 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑑𝑖𝑙𝑢𝑡𝑖𝑜𝑛 𝑤𝑎𝑡𝑒𝑟
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A standard BOD bottle holds 300 mL, so 𝑃 is just the volume of wastewater
divided by 300 mL.
Problem 1:
A 10.0-mL sample of sewage mixed with enough water to fill a 300-mL bottle has
an initial DO of 9.0 mg/L. To help assure an accurate test, it is desirable to have at
least a 2.0-mg/L drop in DO during the five-day run, and the final DO should be at
least 2.0 mg/L. For what range of would this dilution produce the desired results?
5.3.2. Modeling BOD as a First-Order Reaction
Suppose we imagine a flask with some biodegradable organic waste in it. As
bacteria oxidize the waste, the amount of organic matter remaining in the flask will
decrease with time until eventually it all disappears. Another way to describe the
organic matter in the flask is to say as time goes on, the amount of organic matter
already oxidized goes up until finally all the original organic matter has been oxidized.
The figure below shows these two same ways to describe the organic matter.
Figure 6.1. Two equivalent ways to describe the time dependence of organic matter in a flask.
We can also describe oxygen demand from those same two perspectives. We
could say that the remaining demand for oxygen to decompose the wastes decreases
with time until there is no more demand, or we could say the amount of oxygen
demand already exerted, or utilized, starts at zero and rises until all of the original
oxygen demand has been satisfied.
Translating Figure 1 into a mathematical description is straightforward. To do
so, it is assumed that the rate of decomposition of organic wastes is proportional to
the amount of waste that is left in the flask. If we let represent the amount of oxygen
demand left after time 𝑡, then, assuming a first-order reaction, we can write:
𝑑𝐿𝑡
= −𝑘𝐿𝑡
𝑑𝑡
where 𝑘 is the BOD reaction constant (time-1). This differential equation has a
solution equal to
𝑳𝒕 = 𝑳𝟎 𝒆−𝒌𝒕
where is the ultimate carbonaceous oxygen demand. It is the total amount of
oxygen required by microorganisms to oxidize the carbonaceous portion of the waste
to simple carbon dioxide and water. The ultimate carbonaceous oxygen demand is
ENVIRONMENTAL SCIENCE AND ENGINEERING
33
the sum of the amount of oxygen already consumed by the waste in the first 𝑡 days
(𝐵𝑂𝐷𝑡 ), plus the amount of oxygen remaining to be consumed after time 𝑡. That is,
𝐿0 = 𝐵𝑂𝐷𝑡 + 𝐿𝑡
Combining the last two equations,
𝑩𝑶𝑫𝒕 = 𝑳𝟎 (𝟏 − 𝒆−𝒌𝒕 )
A graph of 𝑳𝒕 = 𝑳𝟎 𝒆−𝒌𝒕 and 𝑩𝑶𝑫𝒕 = 𝑳𝟎 (𝟏 − 𝒆−𝒌𝒕 ) is presented in Figure 2. If these
two figures are combined, the result would look exactly like Figure 1.
Figure 6.2. Idealized carbonaceous oxygen demand: (a) The BOD remaining as a function of time, and
(b) the oxygen already consumed as a function of time.
Notice that oxygen demand can be described by the BOD remaining (you might
want to think of as how much oxygen demand is left at time 𝑡), as in Figure 2a, or
equivalently as oxygen demand already satisfied (or utilized, or exerted), 𝑩𝑶𝑫𝒕 , as in
Figure 2b. Also notice how the five-day BOD is more easily described using the BOD
utilized curve.
Problem 2:
The dilution factor 𝑃 for an unseeded mixture of waste and water is 0.030. The DO of
the mixture is initially 9.0 mg/L, and after five days, it has dropped to 3.0 mg/L. The
reaction rate constant k has been found to be 0.22 day-1.
a) What is the five-day BOD of the waste?
b) What would be the ultimate carbonaceous BOD?
c) What would be the remaining oxygen demand after five days?
5.3.3. The BOD Reaction Rate Constant 𝒌
The BOD reaction rate constant 𝑘 is a factor that indicates the rate of
biodegradation of wastes. As 𝑘 increases, the rate at which dissolved oxygen is used
increases, although the ultimate amount required, 𝐿0 , does not change. The reaction
rate will depend on a number of factors, including the nature of the waste itself (for
example, simple sugars and starches degrade easily while cellulose does not), the
ability of the available microorganisms to degrade the wastes in question (it may take
some time for a healthy population of organisms to be able to thrive on the particular
ENVIRONMENTAL SCIENCE AND ENGINEERING
34
waste in question), and the temperature (as temperatures increase, so does the rate
of biodegradation).
Some typical values of the BOD reaction rate constant, at 20°C, are given in the
table below.
Table 1. Typical Values for the BOD Rate Constant at 20°C
Sample
Raw Sewage
Well-treated Sewage
Polluted River Water
𝒌 (day-1)
0.35—0.70
0.12—0.23
0.12—0.23
Notice that raw sewage has a higher rate constant than either well-treated
sewage or polluted river water. This is because raw sewage contains a larger
proportion of easily degradable organics that exert their oxygen demand quite
quickly, leaving a remainder that decays more slowly.
Note that the rate of biodegradation of wastes increases with increasing
temperature.
5.3.4. Other Measures of Oxygen Demand
In addition to the CBOD and NBOD measures already presented, two other
indicators are sometimes used to describe the oxygen demand of wastes. These are
the:
(1) theoretical oxygen demand (ThOD) and
(2) chemical oxygen demand (COD).
The theoretical oxygen demand is the amount of oxygen required to oxidize
completely a particular organic substance, as calculated from simple stoichiometric
considerations. Stoichiometric analysis, however, for both the carbonaceous and
nitrogenous components, tends to overestimate the amount of oxygen actually
consumed during decomposition. The explanation for this discrepancy is based on a
more careful understanding of how microorganisms actually decompose waste.
Some organic matter, such as cellulose, phenols, benzene, and tannic acid,
resist biodegradation. Other types of organic matter, such as pesticides and various
industrial chemicals, are nonbiodegradable because they are toxic to
microorganisms. The chemical oxygen demand (COD) is a measured quantity that
does not depend either on the ability of microorganisms to degrade the waste or on
knowledge of the particular substances in question. In a COD test, a strong chemical
oxidizing agent is used to oxidize the organics rather than relying on microorganisms
to do the job.
The COD test is much quicker than a BOD test, taking only a matter of hours.
However, it does not distinguish between the oxygen demand that will actually be felt
in a natural environment due to biodegradation and the chemical oxidation of inert
organic matter. It also does not provide any information on the rate at which actual
biodegradation will take place. The measured value of COD is higher than BOD,
though for easily biodegradable matter, the two will be similar. In fact, the COD test
is sometimes used as a way to estimate the ultimate BOD.
ENVIRONMENTAL SCIENCE AND ENGINEERING
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5.4. The Effect of Oxygen-Demanding Wastes on Rivers
The amount of dissolved oxygen in water is one of the most commonly used
indicators of a river’s health. As DO drops below 4 or 5 mg/L, the forms of life that can
survive begin to be reduced. In the extreme case, when anaerobic conditions exist,
most higher forms of life are killed or driven off. Noxious conditions then prevail,
including floating sludges; bubbling, odorous gases; and slimy fungal growths.
5.4.1. Factors that Affect the Among of Dissolved Oxygen (DO) in a River
1) Oxygen demanding wastes remove dissolved oxygen (DO)
2) Photosynthesis adds DO during the day, but those plants remove oxygen
at night; and
3) The respiration of organisms living in the water as well as in sediments
removes oxygen.
4) In addition, tributaries bring their own oxygen supplies, which mix with
those of the main river.
5) In the summer, rising temperatures reduce the solubility of oxygen, while
lower flows reduce the rate at which oxygen enters the water from the
atmosphere.
6) In the winter, ice may form, blocking access to new atmospheric oxygen.
To model properly all of these effects and their interactions is a difficult task.
A simple analysis, however, can provide insight into the most important parameters
that affect DO. We should remember, however, that our results are only a first
approximation to reality.
The simplest model of the oxygen resources in a river focuses on two key
processes:
1) the removal of oxygen by microorganisms during biodegradation, and
2) the replenishment of oxygen through reaeration at the liquid surface.
In this simple model, it is assumed that there is a continuous discharge of
waste at a given location on the river. As the water and wastes flow downriver, it is
assumed that they are uniformly mixed at any given cross section of river, and it is
assumed that there is no dispersion of wastes in the direction of flow. These
assumptions are part of what is referred to as the point-source plug flow model,
illustrated in the figure below.
Figure 6.3. The point-source plug flow model for dissolved-oxygen calculations.
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5.4.2. Deoxygenation
The rate of deoxygenation at any point in the river is assumed to be
proportional to the BOD remaining at that point. That is,
𝑅𝑎𝑡𝑒 𝑜𝑓 𝐷𝑒𝑜𝑥𝑦𝑔𝑒𝑛𝑎𝑡𝑖𝑜𝑛 = 𝒌𝒅 𝑳𝒕
Where: 𝒌𝒅 is the deoxygenation rate constant (day-1)
𝑳𝒕 is the BOD remaining 𝑡 (days) after the wastes enter the river, (mg/L)
The deoxygenation rate constant is often assumed to be the same as the
(temperature adjusted) BOD rate constant 𝑘 obtained in a standard laboratory BOD
test.
For deep, slowly moving rivers, this seems to be a reasonable approximation,
but for turbulent, shallow, rapidly moving streams, the approximation is less valid.
Such streams have deoxygenation constants that can be significantly higher than the
values determined in the laboratory.
Expressing the rate of deoxygenation in terms of 𝐿0 ,
𝑅𝑎𝑡𝑒 𝑜𝑓 𝐷𝑒𝑜𝑥𝑦𝑔𝑒𝑛𝑎𝑡𝑖𝑜𝑛 = 𝒌𝒅 𝑳𝟎 𝒆−𝒌𝒅𝒕
where 𝑳𝟎 is the BOD of the mixture of streamwater and wastewater at the
point of discharge.
Assuming complete and instantaneous mixing,
𝑸𝒘 𝑳𝒘 + 𝑸𝒓 𝑳𝒓
𝑳𝟎 =
𝑸𝒘 + 𝑸𝒓
where 𝑳𝟎 is the ultimate BOD of the mixture of streamwater and wastewater
(mg/L)
𝑳𝒓 is the ultimate BOD of the river just upstream of the point of
discharge (mg/L)
𝑳𝒘 is the ultimate BOD of the wastewater (mg/L)
𝑸𝒓 is the volumetric flow rate of the river just upstream of the
discharge point (m3/s)
𝑸𝒘 is the volumetric flow rate of wastewater (m3/s)
Problem 3:
A wastewater treatment plant serving a city of 200,000 discharges 1.10 m3/s of
treated effluent having an ultimate BOD of 50.0 mg/L into a stream that has a
flow of 8.70 m3/s and a BOD of its own equal to 6.0 mg/L. The deoxygenation
constant, 𝑘𝑑 , is 0.20 day-1.
a. Assuming complete and instantaneous mixing, estimate the ultimate BOD
of the river just downstream from the outfall.
b. If the stream has a constant cross section, so that it flows at a fixed speed
equal to 0.30 m/s, estimate the BOD remaining in the stream at a distance
5.4.3. Reaeration
The rate at which oxygen is replenished is assumed to be proportional to the
difference between the actual DO in the river at any given location and the saturated
value of dissolved oxygen. This difference is called the oxygen deficit, 𝐷:
𝑅𝑎𝑡𝑒 𝑜𝑓 𝑅𝑒𝑎𝑒𝑟𝑎𝑡𝑖𝑜𝑛 = 𝒌𝒓 𝑫
ENVIRONMENTAL SCIENCE AND ENGINEERING
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where 𝒌𝒓 is the reaeration constant (time-1)
𝑫 is the dissolved oxygen deficit (𝑫𝑶𝒔 − 𝑫𝑶)
𝑫𝑶𝒔 is the saturated value of dissolved oxygen
𝑫𝑶 is the actual dissolved oxygen at any point downstream
The reaeration constant, 𝑘𝑡 , is very much dependent on the river conditions. A
fast-moving river will have a much higher reaeration constant than a sluggish stream
or a pond. The most commonly used formulation to empirically relate key stream
parameters to the reaeration constant is:
𝟏
𝟑. 𝟗𝒖 ⁄𝟐
𝒌𝒓 =
𝟑
𝑯 ⁄𝟐
where 𝒌𝒓 is the reaeration constant at 20°C (time-1)
𝒖 is the average stream velocity (m/s)
𝑯 is the average stream depth (m)
Typical values of the reaeration constant for various bodies of water are given below.
Table 2. Typical Reaeration Constants for Various Bodies of Water
Water Body
Small ponds and backwaters
Sluggish streams and large lakes
Large streams of low velocity
Large streams of normal velocity
Swift streams
Rapids and waterfalls
Range of 𝒌𝒓 at 20°C (day-1)
0.10—0.23
0.23—0.35
0.35—0.46
0.46—0.69
0.69—1.15
>1.15
The saturated value of dissolved oxygen varies with temperature, atmospheric
pressure, and salinity. The table below gives representative values of the solubility of
oxygen in water at various temperatures and chloride concentrations.
Table 3. Solubility of Oxygen in Water (mg/L) at 1 atm Pressure
Temperature
(°C)
0
5
10
15
20
25
30
Chloride Concentration in Water (mg/L)
0
5.000
10,000
15,000
14.62
13.73
12.89
12.10
12.77
12.02
11.32
10.66
11.29
10.66
10.06
9.49
10.08
9.54
9.03
8.54
9.09
8.62
8.17
7.75
8.26
7.85
7.46
7.08
7.56
7.19
6.85
6.51
Both the wastewater that is being discharged into a stream and the stream
itself are likely to have some oxygen deficit. If we assume complete mixing of the two,
we can calculate the initial deficit of the polluted river using a weighted average based
on their individual concentrations of dissolved oxygen:
ENVIRONMENTAL SCIENCE AND ENGINEERING
38
𝐷0 = 𝐷𝑂𝑠 − 𝐷𝑂
𝑸𝒘 𝑫𝑶𝒘 + 𝑸𝒓 𝑫𝑶𝒓
𝑫𝟎 = 𝑫𝑶𝒔 −
𝑸𝒘 + 𝑸𝒓
where 𝑫𝟎 is the initial oxygen deficit of the mixture of river and wastewater
𝑫𝑶𝒔 is the saturated value of DO in water at the temperature of the
river
𝑫𝑶𝒘 is the DO in the wastewater
𝑫𝑶𝒓 is the DO in the river just upstream of the wastewater discharge
point
Problem 4:
The waste water in Problem 3: has a dissolved oxygen concentration of 2.0 mg/L
and a discharge rate of 1.10 m3/s. The river that is receiving this waste has DO equal
to 8.3 mg/L, a flow rate of 8.70 m3/s, and a temperature of 20°C. Assuming complete
and instantaneous mixing, estimate the initial dissolved oxygen deficit of the mixture
of wastewater and river water just downstream from the discharge point.
5.5. The Oxygen Sag Curve
The deoxygenation caused by microbial decomposition of wastes and
oxygenation by reaeration are competing processes that are simultaneously
removing and adding oxygen to a stream. Subtracting the rate of reaeration from the
rate of deoxygenation (as shown)
𝑅𝑎𝑡𝑒 𝑜𝑓 𝑖𝑛𝑐𝑟𝑒𝑎𝑠𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑑𝑒𝑓𝑖𝑐𝑖𝑡
= 𝑅𝑎𝑡𝑒 𝑜𝑓 𝑑𝑒𝑜𝑥𝑦𝑔𝑒𝑛𝑎𝑡𝑖𝑜𝑛 − 𝑅𝑎𝑡𝑒 𝑜𝑓 𝑟𝑒𝑎𝑒𝑟𝑎𝑡𝑖𝑜𝑛
yields the following expression for the rate of increase of the oxygen deficit:
𝑑𝐷
= 𝑘𝑑 𝐿0 𝑒 −𝑘𝑑 𝑡 − 𝑘𝑟 𝐷
𝑑𝑡
which has the solution
𝑘𝑑 𝐿0
(𝑒 −𝑘𝑑 𝑡 − 𝑒 −𝑘𝑟 𝑡 ) + 𝐷0 𝑒 −𝑘𝑟 𝑡
𝐷=
𝑘𝑟 − 𝑘𝑑
Since the deficit 𝑫 is the difference between the saturation value of dissolved
oxygen and the actual value 𝑫𝑶, we can write the equation for the 𝑫𝑶 as
𝒌𝒅 𝑳𝟎
𝑫𝑶 = 𝑫𝑶𝒔 − [
(𝒆−𝒌𝒅 𝒕 − 𝒆−𝒌𝒓𝒕 ) + 𝑫𝟎 𝒆−𝒌𝒓𝒕 ]
𝒌𝒓 − 𝒌𝒅
This is the classic Streeter-Phelps oxygen sag equation first described in 1925.
A plot of DO following Streeter-Phelps behavior is given in the figure below.
ENVIRONMENTAL SCIENCE AND ENGINEERING
39
Figure 6.4. Streeter-Phelps Oxygen Sag Curve
As can be seen, there is a stretch of river immediately downstream of the
discharge point where the DO drops rapidly. At the critical point downstream,
dissolved oxygen reaches its minimum value and river conditions are at their worst.
Beyond the critical point, the remaining organic matter in the river has diminished to
the point where oxygen is being added to the river by reaeration faster than it is being
withdrawn by decomposition, and the river begins to recover.
The location of the critical point and the corresponding minimum value of DO
is of obvious importance. At this point stream conditions are at their worst. Setting
the derivative of the oxygen deficit equal to zero and solving for the critical time yields
𝟏
𝒌𝒓
𝑫𝟎 (𝒌𝒓 − 𝒌𝒅 )
𝒕𝒄 =
𝐥𝐧 { [𝟏 −
]}
𝒌𝒓 − 𝒌𝒅
𝒌𝒅
𝒌𝒅 𝑳𝟎
The maximum deficit can then be found by substituting the value obtained for
the critical time, 𝑡𝑐 , into the Streeter-Phelps oxygen sag equation.
Figure 6.5. When the rate of deoxygenation exceeds the rate of reaeration, the DO in the river drops.
At the critical point, those rates are equal. Beyond the critical point, reaeration exceeds decomposition,
the DO curve climbs toward saturation, and the river recovers.
ENVIRONMENTAL SCIENCE AND ENGINEERING
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The oxygen sag curve should make some intuitive sense, even without the
mathematical analysis. Near the outfall, there is so much organic matter being
degraded that the rate of removal of oxygen from the water is higher than the rate
that it can be returned by reaeration, so the dissolved oxygen drops. As we move
further downstream, less and less organic matter remains, so the rate of removal of
oxygen keeps dropping as well. At the critical point, the rate of removal of oxygen
equals the rate of addition of oxygen by reaeration. Beyond the critical point,
reaeration begins to dominate, returning oxygen to the river at a faster rate than the
bacteria remove it, so the dissolved oxygen begins to climb back to the saturation
value. The figure below shows the rate of deoxygenation, the rate of reaeration, and
the oxygen sag curve.
Problem 5:
Just below the point where a continuous discharge of pollution mixes with a
river, the BOD is 10.9 mg/L, and DO is 7.6 mg/L. The river and waste mixture has a
temperature of 20°C, a deoxygenation constant of 0.20/day, an average flow speed of
0.30 m/s, and an average depth of 3.0 m. (In other words, this is just a continuation
of the problem started in Problem 3: and
Problem 4:)
a. Find the time and distance downstream at which the oxygen deficit is at a
maximum.
b. Find the minimum value of DO.
REFERENCES
1. Allaby, M. (2000). “Basics of Environmental Science 2nd Edition.” Taylor &
Francis e-Library
2. Singh, D. K. (2006). “Environmental Science 4th Edition.” New Age
International (P) Ltd., Publishers
ENVIRONMENTAL SCIENCE AND ENGINEERING
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MODULE 06: WATER QUALITY MANAGEMENT
OBJECTIVES
1. Determine the different water quality standards under R.A. 9275,
2. Be familiar with the Philippine National Standard for Drinking Water
(PNSDW), and
3. Identify different sources of water supply.
6. WATER QUALITY STANDARDS
The Philippine Clean Water Act of 2004 (Republic Act 9275) aims to protect
the country’s water bodies from pollution from land-based sources. It provides for a
comprehensive and integrated strategy to prevent and minimize pollution through a
multi-sectoral and participatory approach involving all stakeholders.
The DENR is the lead agency that is mandated explicitly by the Clean Water Act
(CWA) to take the lead role in ensuring the implementation of the law. It has been
tasked to develop policies and guidelines in support to the implementation of the
CWA.
6.1. DENR Administrative Order No. 34 Series of 1990
ENACTED: 1990
SUBJECT: Revised Water Usage and Classification/Water Quality Criteria
Amending Section Nos. 68 and 69, Chapter III of the 1978 NPCC Rules
and Regulations
OVERVIEW: Water classification is the primary component in water quality
management for which goals/objectives of each of the water bodies are
met. Three activities are involved namely: establishments of water
bodies beneficial use, identification of water quality indicators (or
criteria pollutants) and water quality suitable for each use. In the
Philippines classification is an especially important component of
water quality management since the application of effluent standards
are dependent on this classification. This administrative order
classifies water bodies into five (5) classes, ie. AA, A, B, C, D for inland
fresh waters and four (4) classes for marine and coastal water, i.e. SA,
SB, SC and SD.
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6.1.1. Water Usage and Classifications
Table 4. Fresh Surface Water (river, lakes, reservoir, etc.)
Classification
Class AA
Class A
Class B
Class C
Class D
Classification
Class SA
Class SB
Class SC
Class SD
Beneficial Use
Public Water Supply Class I. This class is intended primarily
for waters having watersheds which are uninhabited and
otherwise protected and which require only approved
disinfection in order to meet the National Standards for
Drinking Water (NSDW) of the Philippines.
Public Water Supply Class II. For sources of water supply that
will require complete treatment (coagulation, sedimentation,
filtration, and disinfection) in order to meet the NSDW.
Recreational Water Class I. For primary contact recreation
such as bathing, swimming, skin diving, etc. (particularly
those designated for tourism purposes).
1) Fishery Water for the propagation and growth of fish and
other aquatic resources;
2) Recreational Water Class II. (Boating, etc.)
3) Industrial Water Supply Class I (For manufacturing
processes after treatment)
1) For agriculture, irrigation, livestock watering, etc.
2) Industrial Water Supply Class II (e.g. cooling, etc.)
3) Other inland waters, by their quality, belong to this
classification.
Beneficial Use
1. Waters suitable for the propagation, survival, and
harvesting of shellfish for commercial purposes;
2. Tourist zones and national marine parks and reserves
established under Presidential Proclamation No. 1801;
existing laws and/or declared as such by appropriate
government agency.
3. Coral reef parks and reserves designated by law and
concerned authorities.
1. Recreational Water Class I (Areas regularly used by the
public for bathing, swimming, skin diving, etc.);
2. Fishery Water Class I (Spawning areas for Chanos chanos
or “bangus” and similar species).
1. Recreational Water Class II (e.g. boating, etc.)
2. Fishery Water Class II (Commercial and sustenance
fishing);
3. Marshy and/or mangrove areas declared as fish and
wildlife sanctuaries;
1. Industrial Water Supply Class II (e.g. cooling, etc.)
2. Other coastal and marine waters, by their quality, belong
to this classification.
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6.2. Philippine National Standards of Drinking Water of 2007
Potable water – water that can be consumed in any measured amount without
concern for adverse health effects. Potable water does not necessarily taste good
Palatable water, which is pleasing to drink, is not necessarily safe.
6.2.1. Microbiological Quality
Microbiological agents are important to public health and may also be
significant in modifying the physical and chemical characteristics of water.
6.2.1.1. Public Health Implications
Drinking water supplies should be free from contamination by human and
animal excreta, which can contain a variety of microbial contaminants.
Microbiological parameters are indices of potential waterborne diseases and, in
general, are limited to bacteria, viruses, and pathogenic protozoa. The major interest
in classifying and issuing standards is the identification, quantification, and
evaluation of organisms associated with waterborne diseases. Practically, all
pathogenic organisms that can be carried by water originate from the intestinal tract
of warm-blooded animals.
6.2.1.2. Microbiological Indicators of Drinking Water Quality
• Frequent examinations for fecal indicator organisms remain as the most
sensitive and specific way of assessing the hygienic quality of water. Fecal
indicator bacteria should fulfill certain criteria to give meaningful results. The
tests required to detect specific pathogens are generally exceedingly difficult
and expensive, so it is impractical for water systems to routinely test for
specific types of organisms. A more practical approach is to examine the water
for indicator organisms specifically associated with fecal contamination.
• An indicator organism essentially provides evidence of fecal contamination
from human or warm-blooded animals. The criteria for an ideal organism are
as follows:
a. Always present when pathogenic organism of concern is present, and
absent in clean, uncontaminated water.
b. Present in large numbers in the feces of humans and warm-blooded
animals.
c. Respond to natural environmental conditions and to treatment process in
a manner similar to waterborne pathogens of interest.
d. Readily detectable by simple methods, easy to isolate, identify and
enumerate.
e. Ratio of indicator/pathogen should be high
f. Indicator and pathogen should come from the same source
(gastrointestinal tract),
• No organism fulfills all the criteria for an indicator organism, but the coliform
bacteria fulfill most. The coliform group of bacteria (also called total
coliforms) is defined as all the aerobic and facultative anaerobic, gramENVIRONMENTAL SCIENCE AND ENGINEERING
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negative, nonspore-forming, rod-shaped bacteria that ferment lactose with gas
formation within 48 hours at 35°C.
• This definition includes E. coli (Escherichia coli), the most numerous
facultative bacteria in the feces of warm-blooded animals, plus species
belonging to the genera: (1) Enterobacter, (2) Klebsiella, and (3) Citrobacter.
E. coli is the indicator organism for fecal contamination.
• Water intended for human consumption should contain no indicator
organisms. However, pathogens more resistant to conventional
environmental conditions or treatment technologies may be present in treated
drinking-water in the absence of E. coli or total coliforms. Protozoa and some
enteroviruses are more resistant to many disinfectants including chlorine and
may remain viable and pathogenic in drinking-water following disinfection
process.
• Generally, total coliform must be less than 1.1 most probable number (MPN)
per 100 mL sample.
6.2.2. Physical Properties
• Relate to the quality of water for domestic use and are usually associated with
appearance of water, its color or turbidity, temperature, and in particular,
taste and odor.
• Chemical characterization of drinking water includes the identification of its
components and their concentrations. Water treatment plants monitor for a
variety of inorganic and organic constituents, including chloride, fluorides,
sodium, sulfate, nitrates, iron, manganese, and more than 120 organic
chemicals.
6.2.2.1. Taste and Odor
• Pure water is always tasteless and odorless.
• If any type of taste and smell is present, it may indicate water pollution.
• Foreign matter such as organic compounds, inorganic salts, or dissolved gases
can cause taste and odor in water.
• Certain types of algae, especially the blue-green algae, can also impart foul
tastes and odor.
6.2.2.2. Temperature
• The temperature is not directly used to evaluate whether water is drinkable
or not. However, in natural water systems like lakes and rivers, the
temperature is a significant physical factor that determines water quality.
• The most desirable drinking waters are consistently cool and do not have
temperature fluctuations of more than a few degrees.
• Most individuals find that water having a temperature between 10 – 15°C is
most palatable.
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6.2.2.3. Color
• Pure water is colorless; colored water can indicate pollution.
• Color can also show organic substances.
• Color can also be caused by inorganic metals such as iron or manganese.
• Dissolved organic material from decaying vegetation and inorganic matter
may cause color.
• Excessive blooms of algae or growth of aquatic microorganisms may also
impart color.
• The maximum acceptable level for the color of drinking water is 15 TCU (True
color unit).
6.2.2.4. Turbidity
• Pure water is clear and does not absorb light.
• If turbidity appears in the water, it may indicate water pollution.
• Turbidity is caused by the presence of suspended material such as clay, silt,
finely divided organic materials, plankton, and other particulate material in
water.
• Particles may harbor microbiological contaminants that are harmful to human
health or that decrease the effectiveness of disinfection.
6.2.2.5. Solids
• Total solids (𝑇𝑆) pertains to the sum of total suspended solids (𝑇𝑆𝑆) and total
dissolved solids (𝑇𝐷𝑆) that can be found in water.
• Suspended solids are those that can be retained on a water filter and can settle
out of the water column onto the stream bottom when stream velocities are
low. They include silt, clay, plankton, organic wastes, and inorganic
precipitates such as those from acid mine drainage.
• Dissolved solids are those that pass through a water filter. They include some
organic materials, as well as salts, inorganic nutrients, and toxins.
• If water is filtered to remove suspended solids, the remaining solid in the
water indicates the total dissolved solids. If the dissolved solids in the water
exceed 300 mg/L, it adversely affects living organisms as well as industrial
products.
• The concentration of dissolved solids in stream water is important because it
determines the flow of water in and out of the cells of aquatic organisms. Also,
some dissolved inorganic elements such as nitrogen, phosphorus, and sulfur
are nutrients essential for life. Low concentrations of total solids can result in
limited growth of aquatic organisms due to nutrient deficiencies. Elevated
levels of total solids, however, can lead to eutrophication of the stream or
increased turbidity. Both eutrophication and increased turbidity result in a
decrease in stream water quality.
• Elevated concentrations of total solids may indicate the presence of
agricultural activities, dredging, or mining upstream from your sample site.
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6.3. Water Classification by Sources
➢ Although salt water is used as a drinking water supply, freshwater is the
preferred source.
➢ Potable water is conveniently classified as to its source: (1) groundwater; (2)
surface water.
6.3.1. Groundwater Sources
➢ Groundwater is pumped from well drilled into aquifers.
➢ Aquifer - a geologic formation that will yield water to a well in sufficient
quantities to make the production of water from this formation feasible for
beneficial use; permeable layers of underground rock or sand that hold or
transmit groundwater below the water table
➢ The quantity and quality of water available depends on the type of geological
formation forming the aquifer and the properties of the contaminant, itself.
➢ Drinking-water wells can be shallow (less than 50 ft) or deep (greater than
50 ft).
➢ In general, the deeper the well, the greater the level of protection from
contamination, deep wells only provide protection when the wells are
properly designed and operated so that surface contamination is prevented.
6.3.2. Surface Water Sources
➢ Surface water includes rivers, lakes, and reservoirs.
Groundwater Source
Surface Water Source
Constant composition
Varying composition
High mineral content
Low mineral content
Low turbidity
High turbidity
Low or no color
Color
May be bacteriologically safe Microorganisms present
No dissolved oxygen
Dissolved oxygen
High hardness
Low hardness
H2S, Fe, Mn
Tastes and odors
Possible chemical toxicity
Possible chemical toxicity
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MODULE 07: WATER TREATMENT SYSTEMS
OBJECTIVES
1. Identify the different stages within a water treatment system,
2. Determine the purposes of each stage within a water treatment plant (WTP),
and
3. Differentiate the components of WTP in treating surface and groundwater.
7. WATER TREATMENT SYSTEMS
The purpose of water treatment systems is to bring raw water up to drinking
water quality. The particular type of treatment equipment required to meet these
standards depends largely on the source of water. About half of the drinking water in
the United States comes from groundwater, and half comes from surface water. Most
large cities rely more heavily on surface water, whereas most small towns or
communities depend more on groundwater. Typically surface water treatment
focuses on particle removal, and groundwater treatment focuses on removal of
dissolved inorganic contaminants such as calcium and iron. Producing water free of
microbial pathogens is critical for any water source, but surface water has a much
greater chance of microbial contamination, so filtration is now a requirement for
surface water.
Figure 7.6. Schematic of a typical surface water treatment plant.
A typical treatment plant for surface water might include the following
sequence of steps:
1. Screening and grit removal take out relatively large floating and suspended
debris and the sand and grit that settles very rapidly which may damage
equipment.
2. Primary sedimentation (also called settling or clarification) removes the
particles that will settle out by gravity alone within a few hours.
3. Rapid mixing and coagulation use chemicals and agitation to encourage
suspended particles to collide and adhere into larger particles.
4. Flocculation, which is the process of gently mixing the water, encourages the
formation of large particles of floc that will more easily settle.
5. Secondary settling slows the flow enough so that gravity will cause the floc
to settle.
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6. Filtration removes particles and floc that are too small or light to settle by
gravity.
7. Sludge processing refers to the dewatering and disposing of solids and
liquids collected from the settling tanks.
8. Disinfection contact provides sufficient time for the added disinfectant to
inactivate any remaining pathogens before the water is distributed.
Figure 7.7. Schematic of a typical water treatment plant for groundwater,
including softening for calcium and magnesium removal.
Groundwater is much freer of particles and pathogens than surface water, and
in many places, it is delivered after disinfection alone. However, because
groundwater often moves through the soils and minerals of the subsurface for long
periods before withdrawal, it may contain high levels of dissolved minerals or
objectionable gases. The most common dissolved mineral contaminants are
calcium and magnesium, which are termed hardness. The calcium and magnesium
can be removed by precipitating them as particles, so some softening steps are
similar to the particle removal steps for surface water.
The figure above shows a typical groundwater treatment plant with the
following unit operations:
1. Aeration removes excess and objectionable gases.
2. Flocculation (and precipitation) follows chemical addition, which forces the
calcium and magnesium above their solubility limits.
3. Sedimentation removes the hardness particles that will now settle by gravity.
4. Recarbonation readjusts the water pH and alkalinity and may cause
additional precipitation of hardness-causing ions.
5. Filtration, disinfection, and solids processing serve the same purposes as for
surface water treatment.
7.1. Sedimentation
Sedimentation or gravitational settling of particles from water is one of the
oldest and simplest forms of water treatment. Simply allowing water to sit quietly in
anything from a jar to a reservoir, decanting the water, and then using the
undisturbed surface water often considerably improves the water’s quality. A
sedimentation basin or clarifier is a large circular or rectangular tank designed to hold
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49
the water for a long enough time to allow most of the suspended solids to settle out.
The longer the detention time, the bigger and more expensive the tank must be, but
correspondingly, the better will be the tank’s performance. Clarifiers are usually
equipped with a bottom scraper that removes collected sludge.
Sedimentation can remove particles that are contaminants themselves or may
harbor other contaminants, such as pathogens or adsorbed metals. Although
particles have very irregular shapes, their size may be described by an equivalent
diameter that is determined by comparing them with spheres having the same
settling velocity. The equivalent diameter is the hydrodynamic diameter when we
speak of particles settling in water, and aerodynamic diameter for particles settling
in air.
Figure 7.8. Schematic of a Sedimentation Basin
7.2. Coagulation and Flocculation
Raw water may contain suspended particles that are too small to settle by
gravity in a reasonable time period and cannot be removed by simple filtration. Many
of these particles are colloids (particles in the size range of about 0.001 to 1 𝜇𝑚). The
goal of coagulation is to alter the particle surfaces in such a way as to permit them to
adhere to each other. Thus, they can grow to a size that will allow removal by
sedimentation or filtration. Coagulation is considered to be a chemical treatment
process that destabilizes particles (makes them “sticky”), as opposed to a physical
treatment operation such as flocculation, sedimentation, or filtration.
Most colloids and nonsettleable particles of interest in water treatment
remain suspended in solution because they have a net negative surface charge that
causes the particles to repel each other. The coagulant’s purpose is to neutralize the
surface charge, thus allowing the particles to come together to form larger particles
that can be more easily removed. The usual coagulant is alum, 𝐴𝑙2 (𝑆𝑂4 )3 ∙ 18𝐻2 𝑂,
although 𝐹𝑒𝐶𝑙3, 𝐹𝑒𝑆𝑂4 , and other coagulants, such as polyelectrolytes, can be used.
Let us look at the reactions involving alum. Alum ionizes in water, producing 𝐴𝑙 3+
ions, some of which neutralize the negative charges on the colloids. Most of the
aluminum ions, however, react with alkalinity in the water (bicarbonate) to form
insoluble aluminum hydroxide, 𝐴𝑙(𝑂𝐻)3 . The overall reaction is
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50
If insufficient bicarbonate is available for this reaction to occur, the pH must
be raised, usually by adding lime 𝐶𝑎(𝑂𝐻)2 or sodium carbonate (soda ash),
𝑁𝑎2 𝐶𝑂3. The aluminum hydroxide precipitate forms a light, fluffy floc that adsorbs
destabilized particles on its surface as it settles. The destabilized particles may also
aggregate and grow by colliding with each other. The degree of particle
destabilization is quantified by the collision efficiency factor, 𝛼, which is defined as
the fraction of the number of collisions between particles that result in
aggregation. If the particles are completely destabilized, then every collision
results in aggregation, and 𝛼 = 1.0, whereas, for instance, if 𝛼 = 0.25, only one in
four collisions between particles results in the colliding particles sticking together.
Coagulants are added to the raw water in a rapid mix/coagulation tank that
has quickly rotating impellers to mix the chemicals. Detention times in the tank are
typically less than one-half minute. Flocculation follows in a tank that provides
gentle agitation for approximately one-half hour. During this time, the
precipitating aluminum hydroxide forms a plainly visible floc. The mixing in the
flocculation tank must be done very carefully. It must be sufficient to encourage
particles to make contact with each other and enable the floc to grow in size, but it
cannot be so vigorous that the fragile floc particles will break apart. Mixing also
helps keep the floc from settling in this tank, rather than in the sedimentation tank
that follows. The figure below shows a cross-section of a mixing tank followed by
a sedimentation tank.
Figure 7.9. Cross-section of flocculation and sedimentation tanks.
7.3. Filtration
Filtration is one of the most widely used and effective means of removing small
particles from water. This also includes pathogens, which are essentially small
particles. For drinking water filtration, the most common technique is called rapid
depth filtration. The rapid depth filter consists of a layer or layers of carefully sieved
filter media, such as sand, anthracite coal, or diatomaceous earth, on top of a bed of
graded gravels. The pore openings between the media grains are often greater than
the size of the particles that are to be removed; so much of the filtration is
accomplished by means other than simple straining. Adsorption, continued
flocculation, and sedimentation in the pore spaces are important removal
mechanisms. When the filter becomes clogged with particles, the filter is shut down
for a short period of time and cleaned by forcing water backwards through the media.
After backwashing, the media settles back in place and operation resumes.
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7.4. Disinfection
The final, primary unit operation in most water treatment trains is
disinfection. Disinfection has to meet two objectives: primary disinfection, to kill any
pathogens in the water, and secondary (or residual) disinfection to prevent pathogen
regrowth in the water during the period before it is used. Although traditionally a
single disinfectant was added to the water to serve both purposes, it is becoming
more common to use one chemical as the primary disinfectant and another as the
residual disinfectant.
The most commonly used method of disinfection in the U.S. is free chlorine
disinfection because it is cheap, reliable, and easy to use. Free chlorine in water is
developed by dosing with either chlorine gas (𝐶𝑙2(𝑔) ), sodium hypochlorite (𝑁𝑎𝐶𝑙𝑂),
or calcium hypochlorite (𝐶𝑎(𝐶𝑙𝑂)2). The dosed chemical reacts in the water to
produce dissolved chlorine gas (𝐶𝑙2(𝑎𝑞) ), hypochlorous acid (𝐻𝐶𝑙𝑂), and hypochlorite
(𝐶𝑙𝑂− ), which all contribute to the free chlorine concentration.
Hypochlorous acid (𝐻𝐶𝑙𝑂) is a much stronger disinfectant than hypochlorite
(𝐶𝑙𝑂− ), so free chlorine disinfection is usually conducted in slightly acidic water.
Dissolved chlorine gas does not contribute significantly to the free chlorine
concentration unless the water pH is less than 3, which is too acidic (corrosive) for
practical use. Although free chlorine is very effective against bacteria, its effectiveness
is less with protozoan cysts, most notably those of Giardia lamblia and
Cryptosporidium, and with viruses.
A principal advantage of chlorination over other forms of disinfection is that a
chlorine residual is created that provides secondary disinfection of the treated water
after leaving the treatment plant. This residual of chlorine guards against possible
contamination that might occur in the water distribution system.
A disadvantage of free chlorine is the formation of halogenated disinfectant
byproducts (DBPs). DBPs include trihalomethanes (THMs), such as the carcinogen,
chloroform (𝐶𝐻𝐶𝑙3 ), and haloacetic acids (HAAs). THMs and HAAs are created when
free chlorine combines with natural organic substances, such as decaying vegetation,
which may be present in the water. One approach to reducing THMs is to remove
more of the organics before chlorination takes place.
Figure 7.10. Three-Dimensional Chlorine Contact Tank
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7.5. Hardness and Alkalinity
The presence of multivalent cations, most notably calcium and magnesium
ions, is referred to as water hardness. Groundwater is especially prone to excessive
hardness. Hardness causes two distinct problems. First, the reaction between
hardness and soap produces a sticky, gummy deposit called “soap curd” (the ring
around the bathtub). Essentially all home cleaning activities, from bathing and
grooming to dishwashing, are made more difficult with hard water.
Although the introduction of synthetic detergents has decreased but not
eliminated the impact of hardness on cleaning, the second problem, that of scaling,
remains significant. When hard water is heated, calcium carbonate (𝐶𝑎𝐶𝑂3) and
magnesium hydroxide (𝑀𝑔(𝑂𝐻)2 ) readily precipitate out of solution, forming a rocklike scale that clogs hot water pipes and reduces the efficiency of water heaters,
boilers, and heat exchangers. Pipes filled with scale must ultimately be replaced,
usually at great expense. Heating equipment that has scaled up not only transmits
heat less readily, thus increasing fuel costs, but also is prone to failure at a much
earlier time. For both of these reasons, if hardness is not controlled at the water
treatment plant itself, many individuals and industrial facilities find it worth the
expense to provide their own water softening.
Hardness is defined as the concentration of all multivalent metallic cations in
solution, including iron (𝐹𝑒 2+ ), manganese (𝑀𝑛2+ ), strontium (𝑆𝑟 2+ ), and aluminum
(𝐴𝑙 3+ ). However, the principal ions causing hardness in natural water are calcium
(𝐶𝑎2+ ) and magnesium (𝑀𝑔2+ ), so typically hardness can be operationally defined as
the sum of only 𝐶𝑎2+ and 𝑀𝑔2+ .
7.6. Softening
Hard water causes scaling of pipes and makes laundering more difficult, so
many water treatment plants provide water softening. Surface waters seldom have
hardness levels above 200 mg/L as 𝐶𝑎𝐶𝑂3 , so softening is not usually part of the
treatment process.
For groundwater, however, where hardness levels are sometimes over 1,000
mg/L, it is quite common. There are two popular approaches to softening water: the
lime-soda ash process and the ion-exchange process. Either may be used in a central
treatment plant prior to distribution, but individual home units only use the ionexchange process.
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MODULE 08: SOLID WASTE MANAGEMENT
OBJECTIVES
1. To describe the importance of Solid Waste Management
2. To explain and understand the different sources of solid wastes.
3. To explain the different treatments used for Solid Waste Management.
8. RA 9003 – ECOLOGICAL SOLID WASTE MANAGEMENT ACT OF 200
Solid Waste Management (SWM) implementation follows a hierarchy of
options as illustrated by an inverted triangle in Figure 8.1 below. The most preferred
option is waste avoidance and reduction where the ultimate goal is to reduce the
amount of materials entering the waste stream. Apart from avoidance, achieving this
goal involves product reuse, increased product durability, reduced material use in
production and decreased consumption. Behavioral change is deemed necessary in
the exercise of this option as lifestyle demands often favor convenience over
conservation with minimal regard for long-term environmental consequences.
Figure 8.1 Hierarchy of Options in SWM
There are now various initiatives towards waste reduction such as ‘green
procurement’. eco-labeling, identification of non-environmentally acceptable
products and implementation of 3Rs.
Executive Order (EO) No. 301 was issued in 2004 establishing a “Green
Procurement Program” (GPP) for the executive branch of government. The executive
order also provides for a systematic and comprehensive National Eco-Labeling
Program (NELP) necessary to support a “green procurement” policy in both
government and the general public. The GPP is an approach to procurement in which
environmental impacts are taken into account in purchasing decisions.
Environmentally responsible initiatives include switch to electronic submission of
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purchase requests, reduction of materials and energy usage, greening the supply
chain and patronage of eco-labeled products.
The National Solid Waste Management Commission (NSWMC) is mandated under
RA 9003 to prepare and update a list of non-environmentally acceptable products
(NEAP) to be prohibited and as long as NEAP alternatives cost no more than 10% of
the cost of disposable products. However, no product has yet been determined as
non-environmentally acceptable (NEA).
8.1. Functional Elements of Solid Waste Management (SWM)
(1) Source Generation, (2) Storage, (3) Transport/Transfer, (4) Treatment, and (5)
Disposal
8.1.1. Source Generation
Figure 8.2 Composition of Solid Wastes
⮚ Solid wastes are wastes that aren’t liquid or gaseous, such as durable goods,
nondurable goods, containers and packaging, food scraps, yard trimmings, and
miscellaneous inorganic wastes. This is more or less synonymous with the
term refuse, but solid waste is preferred.
⮚ Municipal solid waste (MSW) is solid waste from residential, commercial,
institutional, and industrial sources, but it does not include such things as
construction waste, automobile bodies, municipal sludges, combustion ash,
and industrial process wastes even though those wastes might also be
disposed of in municipal waste landfills or incinerators.
⮚ Garbage, or food waste, is the animal and vegetable residue resulting from the
preparation, cooking, and serving of food. This waste is largely putrescible
organic matter and moisture. Home kitchens, restaurants, and markets are
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⮚
⮚
⮚
⮚
⮚
sources of garbage, but the term usually does not include wastes from large
food-processing facilities such as canneries & slaughterhouses.
Rubbish consists of old tin cans, newspaper, tires, packaging materials, bottles,
yard trimmings, plastics, and so forth. Both combustible and noncombustible
solid wastes are included, but rubbish does not include garbage.
Trash is the combustible portion of rubbish.
Generation refers to the amounts of materials and products that enter the
waste stream. Activities that reduce the amount or toxicity of wastes before
they enter the municipal waste system, such as reusing refillable glass bottles
or reusing plastic bags, are not included.
Materials recovery is the term used to cover the removal of materials from the
wastestream for purposes of recycling or composting.
Discards are the solid waste remaining after materials are removed for
recycling or composting. These are materials that are burned of buried. In
other words,
𝑊𝑎𝑠𝑡𝑒 𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 = 𝑀𝑎𝑡𝑒𝑟𝑖𝑎𝑙𝑠 𝑅𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑 + 𝐷𝑖𝑠𝑐𝑎𝑟𝑑𝑠
8.1.1.1. Sources and Composition of Municipal Solid Waste (MSW)
The amount, composition and sources of solid wastes generated can be
statistically determined through the conduct of waste analysis and characterization
studies (WACS).
Sources of municipal solid waste
Information on the sources of MSW was provided by a number of EMB Regional
Offices in addition to data from submitted SWM plans. The available information from
2008 to 2013 was synthesized and summarized in the figure below.
Figure 8.3 Percentage contribution of the various sources of MSW
MSW comes from residential, commercial, institutional and industrial sources.
Residential waste constitutes the bulk (56.7%) of MSW and includes kitchen scraps,
yard waste, paper and cardboards, glass bottles, plastic containers and sando bags,
ENVIRONMENTAL SCIENCE AND ENGINEERING
56
foils, soiled tissues and diapers, and special wastes such as containers of household
cleaning agents, batteries and waste electrical and electronic equipment (WEEE).
Commercial sources which include commercial establishments and public or
private markets contribute 27.1% of which, in some regions, about two- thirds of
commercial wastes come from the latter. Institutional sources such as government
offices, educational and medical institutions account for about 12.1% while the
remaining 4.1% are waste coming from the industrial or manufacturing sector.
Composition of municipal solid waste
Based on available information from Regional State of the Brown Environment
reports and various WACS data, the typical composition of MSW in the Philippines is
shown below.
• Biodegradable wastes comprise about half (52.31%) of MSW although
primary data suggest that figures can range from 30% to as much as 78%.
Typical bio-waste consists of kitchen or food waste and yard or garden
waste. From the available information, it could be estimated that 86.2% of
compostable waste comes from food scraps while 13.8% are leaves and
twigs.
• Recyclable wastes account for almost a third (27.78%) of MSW with an
estimated range of 4.1% to 53.3%. Plastic packaging materials comprise
around 38% of this waste fraction and followed by paper and cardboard
waste, which contributes about 31%. The remaining 31% is made up of
metals, glass, textile, leather and rubber.
• Special wastes which consist of household healthcare waste, waste
electrical and electronic equipment (WEEE), bulky waste and other
hazardous materials contribute a measly 1.93% with values ranging from
negligible up to 9.2%.
• Finally, residuals have been found to make up 17.98% of generated MSW.
Most LGUs present this data as a combination of disposable wastes as well
as inert materials, which comprise about 12% of the residual waste.
Figure 8.4 Percentage by weight of MSW in the Philippines
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8.1.1.2. Waste Generation Rates
Waste generation rates have been estimated based on consolidated data
generated from waste analysis and characterization studies (WACS) presented in
EMB regional reports and selected local 10-year Solid Waste Management (SWM)
plans. Using 2010 as base year, the table below summarizes waste generation rates
in the Philippines, Metro Manila, highly urbanized cities (HUCs), municipalities and
other cities.
In 2010, waste generation rates vary from as low as 0.10 𝑘𝑔/𝑐𝑎𝑝𝑖𝑡𝑎/𝑑𝑎𝑦 in the
municipalities outside of Metro Manila to 0.79 𝑘𝑔/𝑐𝑎𝑝𝑖𝑡𝑎/𝑑𝑎𝑦 in Metro Manila and
HUCs. The rates are dependent on household income, local economic activity and
waste avoidance policies and incentives. The average per capita generation rate for
the Philippines is 0.40 𝑘𝑔.
Table 8.1 Waste Generation Rates in the Philippines
Scope / Coverage
Metro Manila (NCR)
Metro Manila and some
highly urbanized cities
(HUCs)
Other cities and
provincial capitals
(excluding NCR/HUCs)
Philippines (Nationwide)
All LGUs in the country
excluding Metro Manila
Municipalities (cities and
some capital towns
excluded)
Sample Size
(% or
demographic)
100%
Weighted
Average
(𝑘𝑔/𝑐𝑎𝑝𝑖𝑡𝑎/𝑑𝑎𝑦)
0.55 – 0.79
0.69
Range
N/A
0.53 – 0.79
0.69
N/A
0.29 – 0.64
0.50
79%
0.10 – 0.79
0.40
76%
0.10 – 0.71
0.34
N/A
0.10 – 0.64
0.31
Based on the per capita rate of 0.40 and annual projected population, the
amount of waste generated yearly in the entire Philippines and Metro Manila in terms
of tonnage can be seen in the chart below.
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Figure 8.5 Projected waste generation from 2008 to 2020
Figure 8.5 shows that the yearly amount of waste in the country is expected to
increase from 13.48 million tons in 2010 to 14.66 million tons in 2014 to 16.63
million tons in 2020. On the other hand, Metro Manila’s waste generation continues
to increase as it contributes 22.2%, 24.5%, and 26.7% to the country’s solid waste in
the years 2010, 2014, and 2020, respectively.
8.1.1.3. Characterization of Disposed Waste
Table 8,2 Characteristics of Disposed Wates
8.1.2. Storage
In cases where segregation at source and segregated storage are not practiced
by households, communities and businesses, most solid wastes end up as “ mixed
garbage”. This may be due to limited awareness, appreciation and discipline on the
part of the citizenry, lack of incentives and enforcement ordinances on the part of the
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government, or inadequate support facilities in place to receive pre-segregated
materials.
To address this problem, some LGUs provide segregated waste containers and
implement color codes to aid in the easy identification of segregated bins. In 2013,
the NSWMC had already approved Resolution No. 60 to provide recommendatory
measures for mandatory solid waste segregation at source, segregated collection and
recovery to guide waste generator on onsite separation and support the LGUs in
implementing ‘no-segregation, no-collection’ campaigns.
Some LGUs have strictly enforced segregation at source coupled with
segregated collection, through a “no segregation, no collection” ordinance and the
operation of MRFs. The DENR’s Environment and Natural Resources Management
Project (ENRMP) aimed at identifying and selecting LGUs with promising initiatives
and regularly monitoring its compliance and performance.
8.1.3. Transport / Transfer
Collection is the act of removing solid waste from the source or from a
communal storage point. It is regarded as potentially the most expensive of the
functional elements of SWM.
RA 9003 requires segregated collection by the LGUs. Waste segregation and
collection are to be conducted at the barangay level specifically for biodegradable and
recyclable wastes while disposal and collection of non-recyclable/residual and
special wastes are the responsibility of the city or municipality.
Waste collection techniques include 1) door-to door – where waste materials
are collected in every house within a target area to recover recyclables to be sold to
junkshops and biodegradables either for use as animal feeds or for composting and
2) block or communal – which utilizes MRFs in barangays that are within or near the
targeted collection area.
Figure 8.6 Transfer Stations
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Figure 8.7 500-Ton Capacity Barge
8.1.4. Treatment
8.1.4.1. Materials Recovery Facility (MRF)
RA 9003 mandates the establishment of a Materials Recovery Facility (MRF)
in every barangay or cluster of barangays in barangay-owned, leased land or any
suitable open space designated by the barangay. The MRF shall be designed to
receive, sort, process and store compostable and recyclable material efficiently and
in an environmentally sound manner. Any resulting residual waste shall be
transferred to a proper disposal facility.
MRFs are also being established in schools, malls, and other commercial
establishments. There are also mobile and gravity-driven, centralized MRFs. A
number of LGUs also engage local junkshops to serve as their MRFs. Through
Memorandum of Agreements (MOAs) and following the guidelines on MRF
establishment, junk dealers become part of the formal SWM system of the LGU.
8.1.4.2. Composting
Under RA 9003, composting is regarded as a means to meet the mandatory
waste diversion requirements. It is the biological decomposition of biodegradable
solid waste under controlled predominantly aerobic conditions to a state that is
sufficiently stable for nuisance-free storage and handling and is satisfactorily
matured for safe use in agriculture. It can either be a component of an MRF or
established as a standalone processing facility. The law also provides for an inventory
of markets for compost and guidelines for compost quality.
Typical small-scale composting in the Philippines is done in compost pits, tire
towers, coconut shell stack, bottomless bins, clay pots and plastic sacks. Meanwhile,
large-scale composting is done in windrows (by turning, passive aeration, active
aeration and static piles), in-vessel (e.g., agitated beds, composting silos and rotating
drum bioreactors), and through vermin or worm composting.
It is estimated that composting could reduce the weight of organic waste by 50%
or more and vermicomposting by 70-80%, the latter capable of turning
biodegradables into a high-quality vermicompost product.
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8.1.4.3. Recycling
The important role of recycling in achieving the mandatory waste diversion
requirements is recognized under RA 9003. This law offers guidelines on the
establishment and operation of buy-back centers and MRFs and provides for an
inventory of markets and eco-labelling of recyclables. Recycling may either be a
component of an MRF or established as a stand-alone processing facility.
Recyclables, particularly those with high commercial value such as paper, scrap
metals and plastics are typically sold to junk dealers, consolidators and recyclers. The
accumulated recyclables from MRFs are delivered to junkshops. In many cases, either
the semi-formal or informal waste collectors or even the generators themselves bring
the sellable materials to junkshops or at designated areas during recyclables
collection events.
The recovered materials that are sold to local junkshops pass through a business
chain of middlemen and wholesaler for use by the industry sector, mainly outside the
Philippines. However, there are local commercial recyclers that utilize such materials
to produce recycled products such as paper/cardboard and recycled aluminum – at a
larger scale.
8.1.5. Disposal
Waste disposal refers to the discharge, deposit, dumping, spilling, leaking or
placing of any solid waste into or in any land while disposal sites refer to areas where
solid waste is finally discharged and deposited. It is regarded as the least preferred
method of managing solid waste although it plays an important role in dealing with
residual waste.
Almost all solid wastes ended up at dumpsites before the passage of RA 9003.
Dumpsites are raw, open spaces designated as local disposal areas that lack
engineering measures and pollution control systems. These are often located close to
ravines, gullies, seashore, bodies of water and other open spaces and usually become
inaccessible during heavy rains.
The law mandates the closure and rehabilitation of all dumpsites and their
replacement with sanitary landfills (SLFs). SLFs are disposal facilities with
impermeable liners to prevent liquid discharges from polluting ground and surface
waters. It should also have a gas management system to reduce risks of burning or
explosion, a regular soil cover to minimize odor, and other environmental protection
features.
8.1.5.1. Open and Controlled Dumpsites
RA 9003 prohibits the establishment and operation of open dumps or any
practice or disposal involving the use of open dumps. Open dumps, however, were
allowed to be converted into controlled dumps only until 2006 as a temporary and
remedial measure. Nevertheless, controlled dumps which were required to meet
basic waste management guidelines should have been phased out in 2006 in favor of
sanitary landfills. The legally mandated transition was not fully realized as many open
and controlled dumps are still currently in operation.
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Figure 8.8 Dumpsite Locations
8.1.5.2. Sanitary Landfills
A sanitary landfill (SLF) refers to a waste disposal site designed, constructed,
operated and maintained in a manner that exerts engineering control over significant
potential environmental impacts arising from the development and operation of the
facility. Prior to 2004, the country had only four sanitary landfills - located in Capas,
Tarlac, Inayawan, Cebu City, San Mateo, Rizal and Carmona, Cavite.
Sections 40 to 42 of RA 9003 provides for the criteria in site selection,
establishment and operation of SLFs. Specifically, Section 41 stipulates the minimum
requirements for the establishment of SLFs: a landfill liner system, leachate collection
and treatment, gas control recovery system, groundwater monitoring wells, a daily
cover during operations and final cap over the completely filled landfill, and a closure
and post-closure maintenance procedure.
The traditional material used to render landfill cells impervious to water
seepage is high-density polyethylene (HDPE) plastic material. However, with the
pioneering efforts in Bais City, it was found that compacted bentonite clay or clayspiked host soil may be used as alternative liner material as long as it passes the
permeability requirements for a landfill liner.
In 2005, the NSWMC issued a Resolution No. 06 on the guidelines for
establishing categorized SLFs, which was later adopted at DAO 2006-10 and
supplemented by the ‘Technical guidebook on solid wastes disposal design, operation
and management’. The guidelines still mandate the use of the relatively expensive
HDPE for bigger SLFs but the minimum requirements of clay liners for smaller
landfills facilitated the compliance of smaller municipalities.
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MODULE 9: AIR POLLUTION
OBJECTIVES:
1. Enumerate and differentiate the different cases, sources and effects of air
pollution.
2. Identify and explain the different ways to mitigate air pollution.
9. AIR POLLUTION
Air pollution is the introduction of particulates, biological molecules, or other
harmful materials into Earth's atmosphere, causing disease, death to humans,
damage to other living organisms such as food crops, or the natural or built
environment. Air pollution may come from anthropogenic (man-made) or natural
sources.
Air pollution occurs when the air contains gases, dust, fumes, or odor in
harmful amounts. That’s amounts which could be harmful to the health or comfort of
humans and animals or which could cause damage to plants and materials.
9.1 SOURCES OF AIR POLLUTION
There are two main sources of air pollution.
9.1.1 Anthropogenic Sources (man-made) - includes impacts on biophysical
environments, biodiversity, and other resources.
• Mobile Sources
- refers to a source that is capable of moving under its own power.
In general, mobile sources imply "on-road" transportation, which includes
vehicles such as cars, sport utility vehicles, and buses. In addition, there is also a "nonroad" or "off-road" category that includes gas-powered lawn tools and mowers, farm
and construction equipment, recreational vehicles, boats, planes, and trains.
• Stationary Sources
Stationary source refers to an emission source that does not move, also known
as a point source. Stationary sources include factories, power plants, dry cleaners and
degreasing operations.
• Area Sources
- made up of lots of smaller pollution sources that aren't a big deal by
themselves but when considered as a group can be. The term area source is used to
describe many small sources of air pollution located together whose individual
emissions may be below thresholds of concern, but whose collective emissions can be
significant.
• Agricultural sources
Residential wood burners are a good example of a small source, but when
combined with many other small sources, they can contribute to local and regional
air pollution levels. Area sources can also be thought of as non-point sources, such as
construction of housing developments, dry lake beds, and landfills.
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Those that raise animals and grow crops, can generate emissions of gases and
particulate matter. For example, animals confined to a barn or restricted area (rather
than field grazing), produce large amounts of manure. Manure emits various gases,
particularly ammonia into the air.
This ammonia can be emitted from the animal houses, manure storage areas, or
from the land after the manure is applied. In crop production, the misapplication of
fertilizers, herbicides, and pesticides can potentially result in aerial drift of these
materials and harm may be caused.
9.1.2 Natural Sources
Although industrialization and the use of motor vehicles are overwhelmingly
the most significant contributors to air pollution, there are important natural
sources of "pollution" as well. Wildland fires, dust storms, and volcanic activity also
contribute gases and particulates to our atmosphere.
Unlike the above-mentioned sources of air pollution, natural "air pollution" is
not caused by people or their activities. An erupting volcano emits particulate matter
and gases; forest and prairie fires can emit large quantities of "pollutants"; plants and
trees naturally emit VOCs which are oxidized and form aerosols that can cause a
natural blue haze; and dust storms can create large amounts of particulate matter.
Wild animals in their natural habitat are also considered natural sources of
"pollution".
The National Park Service recognizes that each of these sources emits gases
and particulate matter into the atmosphere but we regard these as constituents
resulting from natural processes.
9.2 EFFECTS OF AIR POLLUTION
9.2.1 Ecological Effects
Smog hanging over cities is the most familiar and obvious form of air pollution.
But there are different kinds of pollution—some visible, some invisible—that
contribute to global warming. Generally, any substance that people introduce into the
atmosphere that has damaging effects on living things and the environment is
considered air pollution.
Carbon dioxide, a greenhouse gas, is the main pollutant that is warming Earth.
Though living things emit carbon dioxide when they breathe, carbon dioxide is widely
considered to be a pollutant when associated with cars, planes, power plants, and
other human activities that involve the burning of fossil fuels such as gasoline and
natural gas. In the past 150 years, such activities have pumped enough carbon dioxide
into the atmosphere to raise its levels higher than they have been for hundreds of
thousands of years.
Acidification
Chemical reactions involving air pollutants can create acidic compounds
which can cause harm to vegetation and buildings. Sometimes, when an air pollutant,
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such as sulfuric acid combines with the water droplets that make up clouds, the water
droplets become acidic, forming acid rain. When acid rain falls over an area, it can kill
trees and harm animals, fish, and other wildlife.
Acid rain destroys the leaves of plants. When acid rain infiltrates into soils, it
changes the chemistry of the soil making it unfit for many living things that rely on
soil as a habitat or for nutrition. Acid rain also changes the chemistry of the lakes and
streams that the rainwater flows into, harming fish and other aquatic life.
Eutrophication
Rain can carry and deposit the Nitrogen in some pollutants on rivers and soils.
This will adversely affect the nutrients in the soil and water bodies. This can result in
algae growth in lakes and water bodies, and make conditions for other living
organism harmful.
Ground-level ozone
Chemical reactions involving air pollutants create poisonous gas ozone (O3).
Gas Ozone can affect people’s health and can damage vegetation types and some
animal life too.
9.2.2 Health Effects
The effects of inhaling particulate matter that have been widely studied in
humans and animals include asthma, lung cancer, cardiovascular disease, respiratory
diseases, premature delivery, birth defects, and premature death.
Increased levels of fine particles in the air as a result
of anthropogenic particulate air pollution is consistently and independently related
to
the
most
serious
effects,
including lung
cancer and
other cardiopulmonary mortality.
Mortality
It is estimated that some 7 million premature deaths may be attributed to air
pollution. India has the highest death rate due to air pollution. India also has more
deaths from asthma than any other nation according to the World Health
Organization. In December 2013 air pollution was estimated to kill 500, 000 people
in China each year. There is a correlation between pneumonia-related deaths and air
pollution from motor vehicles. Air pollution is estimated to reduce life expectancy by
almost nine months across the European Union. Causes of deaths
include strokes, heart disease, COPD, lung cancer, and lung infections.
The US EPA estimates that a proposed set of changes in diesel
engine technology (Tier 2) could result in 12,000 fewer premature mortalities, 15
000 fewer heart attacks, 6 000 fewer emergency room visits by children with asthma,
and 8 900 fewer respiratory-related hospital admissions each year in the United
States.
The US EPA estimates allowing a ground-level ozone concentration of 65 parts
per billion would avert 1 700 to 5 100 premature deaths nationwide in 2020
compared with the current 75-ppb standard. The agency projects the stricter
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standard would also prevent an additional 26,000 cases of aggravated asthma and
more than a million cases of missed work or school.
A new economic study of the health impacts and associated costs of air
pollution in the Los Angeles Basin and San Joaquin Valley of Southern California
shows that more than 3 800 people die prematurely (approximately 14 years earlier
than normal) each year because air pollution levels violate federal standards. The
number of annual premature deaths is considerably higher than the fatalities related
to auto collisions in the same area, which average fewer than 2,000 per year.
Diseases Caused by Air Pollution
Asthma
- is a disease that may be caused by air pollution. According to the Natural Resources
Defense Council or NRDC a non-profit international environmental advocacy group
based in New York City, asthma is a chronic, occasionally debilitating inflammatory
disease of the airways that may be caused by air pollution from cars, factories or
power plants.
The NRDC states that the following air pollutants are common triggers of
asthma: ground level ozone, sulfur dioxide, fine particulate matter and nitrogen oxide.
The Centers for Disease Control and Prevention or CDC states that another important
trigger for asthma attacks is environmental or secondhand tobacco smoke. The CDC
suggests that parents, friends and relatives of children with asthma should attempt
to quit smoking and should never smoke in proximity to a child or person with
asthma, as this could cause an asthma attack.
COPD (Chronic Obstructed Pulmonary Disorder)
- is a disease that may be caused by air pollution. The U.S. National Library of
Medicine and the National Institutes of Health or NIH state that, with COPD, a person’s
airways and air sacs lose their shape and become distended or floppy, and that
chronic bronchitis and emphysema are common COPDs. According to the American
Lung Association or ALA, long-term exposure to air pollution, especially automobile
exhaust, boosts women’s risk for lower lung function and dying prematurely.
Truck drivers, dockworkers and railroad workers may be more susceptible to
lung cancer, heart and COPD related death due to chronic exposure to diesel
emissions while on the job. The ALA also notes that even low levels of ozone and fine
particulate matter increase a person’s risk of hospitalization for pneumonia and
COPD.
Lung Cancer
Lung cancer is a disease that may be caused by air pollution. According to Lung
Cancer Organization, lung cancer is characterized by the uncontrolled growth of
abnormal cells in one or both lungs. Over time, the abnormal cells can develop into
tumors and impair the lung’s primary function: to supply oxygen to the body through
the blood. It also states that there are two principal types of lung cancer: non-small
cell lung cancer or NSCLC and small cell lung cancer or SCLC.
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According to a 2002 study by C. Arden Pope III, Ph.D. and colleagues published
in "The Journal of the American Medical Association," long-term exposure to
combustion-generated fine particulate matter poses a significant risk for
cardiopulmonary and lung cancer mortality. A 2000 study by Fredrik Nyberg and
colleagues published in the journal "Epidemiology" concludes that urban air pollution
boosts lung cancer risk, and that motor vehicle emissions may be particularly
problematic.
9.2.3 Economic Effects
Humans and the environment have some ability to resist the effects of poor air
quality. But sometimes this resistance can be overwhelmed with higher levels and
prolonged exposure to air pollution. In particular, humans, wildlife and vegetation
that are old, young, and sick are often more susceptible to air pollution.
Asthma, lung cancer, cardiovascular disease, allergies and many other human
health problems have been linked to poor air quality. In the environment, decreased
species biodiversity and vegetation productivity have been found.
Air pollution can also have a significant impact on our economy. It can cost a
lot to change what we buy, what we use, and how it is produced in order to prevent
air pollution. Economic costs are also found in fixing the damage caused by poor air
pollution, including health and environmental problems.
On the other hand, the creation of new technology, knowledge and jobs to
address air quality concerns can produce economic opportunities.
What is important to remember is that these impacts on human health, the
environment and the economy do not exist in isolation, they are linked. For instance,
decreased forest productivity because acid rain has damaged the soil may lead to
increased stresses on the pulp and paper job market. Similarly, a focus on finding
better economic incentives for reducing air pollution can, in turn, improve human
health and environmental problems.
Drinking Water Cost
Nitrates and algal blooms in drinking water sources can drastically increase
treatment costs. Nitrate-removal systems in Minnesota caused supply costs to rise
from 5-10 cents per 1000 gallons to over $4 per 1000 gallons. It can also cost billions
of dollars to clean up polluted water bodies. Every dollar spent on protecting sources
of drinking water saves in water treatment costs.
Tourism losses
The tourism industry loses close to $1 billion each year, mostly through losses
in fishing and boating activities, as a result of water bodies that have been affected by
nutrient pollution and harmful algal blooms. Airborne nutrient pollution can also
affect visibility at popular outdoor destinations like national parks. This kind of
pollution can also damage buildings and other structures, especially those made of
marble and limestone.
Commercial fishing and shellfish losses
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Fishing and shellfish industries are hurt by harmful algal blooms that kill fish
and contaminate shell fish. Annual losses to these industries from nutrient pollution
are estimated to be in the tens of millions of dollars.
Real estate losses
Clean water can raise the value of a nearby home by up to 25 percent.
Waterfront property values can decline because of the unpleasant sight and odor of
algal blooms.
9.3 PARTICULAR POLLUTANTS
9.3.1 Atmospheric Particular Matter
– also known as particulate matter (PM) or particulates – is microscopic solid
or liquid matter suspended in the Earth's atmosphere. The term aerosol commonly
refers to the particulate/air mixture, as opposed to the particulate matter
alone. Sources of particulate matter can be man-made or natural. They have impacts
on climate and precipitation that adversely affect human health.
Subtypes of atmospheric particle matter include:
• Suspended particulate matter (SPM)
• Respirable suspended particle (RSP), which are [coarse] particles with
a diameter of 10 micrometers or less, also known as PM10
• Fine particles with a diameter of 2.5 micrometers or less, a.k.a. PM2.5
• Ultrafine particles, and
• Soot
The IARC and WHO designate airborne particulates a Group 1 carcinogen.
Particulates are the deadliest form of air pollution due to their ability to penetrate
deep
into
the
lungs
and
blood
streams
unfiltered,
causing
permanent DNA mutations, heart attacks, and premature death. In 2013, a study
involving 312 944 people in nine European countries revealed that there was no safe
level of particulates and that for every increase of 10 μg/m3 in PM10, the lung
cancer rate rose 22%. The smaller PM2.5 were particularly deadly, with a 36%
increase in lung cancer per 10 μg/m3 as it can penetrate deeper into the lungs.
9.3.2 Sources of Particular Matters
Some particulates occur naturally, originating from volcanoes, dust
storms, forest and grassland fires, living vegetation, and sea spray. Human activities,
such as the burning of fossil fuels in vehicles, power plants and various industrial
processes also generate significant amounts of particulates. Coal combustion in
developing countries is the primary method for heating homes and supplying energy.
Because salt spray over the oceans is the overwhelmingly most common form of
particulate in the atmosphere, anthropogenic aerosols—those made by human
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activities—currently account for about 10 percent of the total mass of aerosols in our
atmosphere.
Composition of Aerosols (particulates/air mixtures)
The composition of aerosols and particles depends on their source. Windblown mineral dust tends to be made of mineral oxides and other material blown
from the Earth's crust; this particulate is light-absorbing. Sea salt is considered the
second-largest contributor in the global aerosol budget, and consists mainly
of sodium chloride originated from sea spray; other constituents of atmospheric sea
salt
reflect
the
composition
of sea
water,
and
thus
include magnesium, sulfate, calcium, potassium, etc. In addition, sea spray aerosols
may contain organic compounds, which influence their chemistry.
Secondary particles derive from the oxidation of primary gases such
as sulfur and nitrogen oxides into sulfuric acid (liquid) and nitric acid (gaseous). The
precursors for these aerosols—i.e., the gases from which they originate—may have
an anthropogenic origin (from fossil fuel or coal combustion) and a
natural biogenic origin. In the presence of ammonia, secondary aerosols often take
the form of ammonium salts; i.e., ammonium sulfate and ammonium nitrate (both
can be dry or in aqueous solution); in the absence of ammonia, secondary compounds
take an acidic form as sulfuric acid (liquid aerosol droplets) and nitric acid
(atmospheric gas), all of which may contribute to the health effects of particulates.
Secondary sulfate and nitrate aerosols are strong light-scatterers. This is
mainly because the presence of sulfate and nitrate causes the aerosols to increase to
a size that scatters light effectively.
Organic matter (OM) can be either primary or secondary, the latter part
deriving from the oxidation of VOCs; organic material in the atmosphere may either
be
biogenic
or
anthropogenic.
Organic
matter
influences
the
atmospheric radiation field by both scattering and absorption. Another important
aerosol type is elemental carbon (EC, also known as black carbon, BC): this aerosol
type includes strongly light-absorbing material and is thought to yield large
positive radiative forcing. Organic matter and elemental carbon together constitute
the carbonaceous fraction of aerosols. Secondary organic aerosols, tiny "tar balls"
resulting from combustion products of internal combustion engines, have been
identified as a danger to health.
The chemical composition of the aerosol directly affects how it interacts with
solar radiation. The chemical constituents within the aerosol change the
overall refractive index. The refractive index will determine how much light is
scattered and absorbed.
The composition of particulate matter that generally causes visual effects such
as smog consists of sulfur dioxide, nitrogen oxides, carbon monoxide, mineral dust,
organic matter, and elemental carbon also known as black carbon or soot. The
particles are hygroscopic due to the presence of sulfur, and SO2 is converted to sulfate
when high humidity and low temperatures are present. This causes the reduced
visibility and yellow color.
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Deposition Process
In general, the smaller and lighter a particle is, the longer it will stay in the air.
Larger particles (greater than 10 micrometers in diameter) tend to settle to the
ground by gravity in a matter of hours whereas the smallest particles (less than 1
micrometer) can stay in the atmosphere for weeks and are mostly removed
by precipitation. Diesel particulate matter is highest near the source of emission. Any
info regarding DPM and the atmosphere, flora, height, and distance from major
sources would be useful to determine health effects.
Major primary pollutants produced by human activity include:
• Sulfur oxides (SOx)
- particularly sulfur dioxide, a chemical compound with the formula SO2. SO2
is produced by volcanoes and in various industrial processes. Coal and petroleum
often contain sulfur compounds, and their combustion generates sulfur dioxide.
Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms
H2SO4, and thus acid rain. This is one of the causes for concern over the environmental
impact of the use of these fuels as power sources.
•
Nitrogen oxides (NOx)
Nitrogen oxides, particularly nitrogen dioxide, are expelled from high
temperature combustion, and are also produced during thunderstorms by electric
discharge. They can be seen as a brown haze dome above or a plume downwind of
cities. Nitrogen dioxide is a chemical compound with the formula NO2. It is one of
several nitrogen oxides. One of the most prominent air pollutants, this reddish-brown
toxic gas has a characteristic sharp, biting odor.
•
Carbon monoxide (CO)
CO is a colorless, odorless, toxic yet non-irritating gas. It is a product by
incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is
a major source of carbon.
•
Volatile organic compounds (VOC)
VOCs are a well-known outdoor air pollutant. They are categorized as either
methane (CH4) or non-methane (NMVOCs). Methane is an extremely efficient
greenhouse gas which contributes to enhance global warming. Other hydrocarbon
VOCs are also significant greenhouse gases because of their role in creating ozone and
prolonging the life of methane in the atmosphere. This effect varies depending on
local air quality. The aromatic NMVOCs benzene, toluene and xylene are suspected
carcinogens and may lead to leukemia with prolonged exposure. 1.3-butadiene is
another dangerous compound often associated with industrial use.
•
Particulates
Alternatively referred to as particulate matter (PM), atmospheric particulate
matter, or fine particles, are tiny particles of solid or liquid suspended in a gas. In
contrast, aerosol refers to combined particles and gas. Some particulates occur
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71
naturally, originating from volcanoes, dust storms, forest and grassland fires, living
vegetation, and sea spray. Human activities, such as the burning of fossil fuels in
vehicles, power plants and various industrial processes also generate significant
amounts of aerosols. Averaged worldwide, anthropogenic aerosols—those made by
human activities—currently account for approximately 10 percent of our
atmosphere. Increased levels of fine particles in the air are linked to health hazards
such as heart disease, altered lung function and lung cancer.
Persistent free radicals connected to airborne fine particles are linked to
cardiopulmonary disease.
•
Toxic metals
such as lead and mercury, especially their compounds.
•
Chlorofluorocarbons (CFCs)
- harmful to the ozone layer; emitted from products are currently banned from
use. These are gases which are released from air conditioners, refrigerators, aerosol
sprays, etc. CFC's on being released into the air rises to stratosphere. Here they come
in contact with other gases and damage the ozone layer. This allows harmful
ultraviolet rays to reach the earth's surface. This can lead to skin cancer, disease to
eye and can even cause damage to plants.
•
Ammonia (NH3)
- emitted from agricultural processes. Ammonia is a compound with the
formula NH3. It is normally encountered as a gas with a characteristic pungent odor.
Ammonia contributes significantly to the nutritional needs of terrestrial organisms
by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or
indirectly, is also a building block for the synthesis of many pharmaceuticals.
Although in wide use, ammonia is both caustic and hazardous. In the atmosphere,
ammonia reacts with oxides of nitrogen and sulfur to form secondary particles.
•
Odors
— such as from garbage, sewage, and industrial processes
•
Radioactive pollutants
- produced by nuclear explosions, nuclear events, war explosives, and natural
processes such as the radioactive decay of radon.
Secondary pollutants include:
Particulates created from gaseous primary pollutants and compounds in
photochemical smog. Smog is a kind of air pollution. Classic smog results from large
amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide.
Modern smog does not usually come from coal but from vehicular and industrial
emissions that are acted on in the atmosphere by ultraviolet light from the sun to
form secondary pollutants that also combine with the primary emissions to form
photochemical smog.
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Ground level ozone (O3) formed from NOx and VOCs. Ozone (O3) is a key
constituent of the troposphere. It is also an important constituent of certain regions
of the stratosphere commonly known as the Ozone layer. Photochemical and chemical
reactions involving it drive many of the chemical processes that occur in the
atmosphere by day and by night.
9.3.3 Devise and Methods to Determine Particular Pollutants
Measuring Air Pollution
Air pollution can be directly measured as it is emitted by a source in
mass/volume of emission (e.g., grams/m3) or mass/process parameter (e.g.,
grams/Kg fuel consumed or grams/second). Air pollution can also be measured in the
atmosphere as a concentration (e.g., micrograms/m3). Ambient air monitoring data
is used to determine air quality, establish the extent of air pollution problems, assess
whether established standards are being met, and characterize the potential human
health risk in an area. Alternatively, air pollution concentrations can be simulated
using computer models, and then validated using data collected from direct
measurements at selected monitors or sources. Air pollution data and models are
used together to examine the impacts of control strategies on the ambient air.
Air Quality Modeling
As an alternative to or in conjunction with direct monitoring, computer
models are often used to predict the levels of pollutants emitted from various types
of sources, and how these emissions eventually impact ambient air quality over time.
The models themselves vary in terms of sophistication, accuracy and precision of
their outputs. Different models are used to estimate emission rates, source activity
levels, and ambient air quality impacts.
For example, models are available for estimating emissions from mobile and
stationary sources, predicting meteorological factors, locating potential emission
point sources, and the likely photochemical and dispersion characteristics of air
pollution, as well as predicting traffic patterns and congestion. In addition, emissions
models and preprocessors can be used to provide input data for air quality models
that need emissions based on chemical species, and broken down into very fine
temporal (e.g., grams/second) and spatial (1 km x 1 km grid) resolution.
Monitoring
Air pollution monitoring activities are typically separated into two
classifications: source monitoring and ambient air monitoring. Monitoring can be
made directly using continuous measurement instrumentation or manual methods,
or remotely using optical sensing systems. Source monitoring involves the
measurement of emissions directly from a fixed or mobile emission source, typically
in a contained duct, vent, stack or chimney.
Stationary source data is used to determine control technology performance,
confirm established permit limits are being met, and as input to ozone and/or health
risk prediction models. Major stationary sources may have continuous emissions
monitors (CEMs) installed to report real-time emissions based on pre-established
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reporting cycles. Ambient air monitoring involves the measurement of specific
pollutants present in an immediate surrounding atmosphere. Most Major urban areas
often operate several ambient air monitoring instruments, each dedicated to
measuring specific target pollutants.
High-Volume Air Sampling
The so-called high-volume (hi-vol) sampler for total suspended particulate
matter (TSP) was previously the most widely used sampler since it was the Federal
Reference Method (FRM) for measuring compliance with the TSP particulate matter
standard. Approximately 20,000 hi-vols were operating at federal, state, and local air
pollution control agencies, industries, and research organizations for either routine
or intermittent use in the 1970’s. As TSP levels decreased, the number of TSP
samplers in operation greatly diminished.
With the promulgation of the PM10 standard in 1987, the number of TSP
samplers operated by state and local agencies was down to approximately 2800 and
the number of PM10 samplers was 636. By 1997 the number of TSP samplers
operated by state and local control agencies was reduced to approximately 450.
Although there is no TSP standard, the TSP FRM remains as the official sampling
method for obtaining samples to determine compliance with the national ambient air
quality standard for lead.
Sampler-Shelter Combination
The sampler and its shelter should be considered as a single, functioning unit.
The shelter must provide protection for the sampler, and at the same time allow
unrestricted access of ambient air from all directions without direct impingement of
particles on the filter. A high-volume sampler with a 7- by 9-inch exposed filter area
operated in a standard shelter at a sampling flow rate of 1.1 to 1.7 cubic meters per
minute (39 to 60 cubic feet per minute) collects particles of up to 25 to 50 m in
aerodynamic diameter, depending on wind speed and direction, and uniformly
distributes the sample over the filter surface. The standard peak roof of the shelter,
which acts as a plenum above the filter, is placed to provide a total opening area of
slightly more than the 63-square-inch exposed filter area, thereby permitting free
flow of air into the plenum space.
The size of the opening to the filter and the volume of air filtered per unit time
will affect the particle size range collected. Distribution of particles on the filter may
also be affected. Therefore, any high-volume sampler purchased after February 3,
1983, and used for federally mandated air monitoring, must have uniform sample air
inlets that are sized to provide an effective particle capture air velocity of between 20
and 35 cm/sec at their recommended sampling flow rates. The particle capture air
velocity is determined by dividing the sample air flow rate by the inlet area measured
in a horizontal plane at the lower edge of the sampler’s roof. Ideally, the inlet area and
sampling flow rate of these samplers should be selected to obtain a capture air
velocity of 25 ± 2 cm/sec.
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9.4 METHODS TO CONTROL AIR POLLUTION
Some of the effective methods to Control Air Pollution are as follows:
9.4.1 Source Correction Methods:
Industries make a major contribution towards causing air pollution.
Formation of pollutants can be prevented and their emission can be minimized at the
source itself.
By carefully investigating the early stages of design and development in
industrial processes e.g., those methods which have minimum air pollution po-tential
can be selected to accomplish air-pollution control at source itself.
These source correction methods are:
✓ Substitution of raw materials:
If the use of a particular raw material results in air pollution, then it should be
substituted by another purer grade raw material which reduces the formation of
pollutants. Thus,
Low sulfur fuel which has less pollution potential can be used as an alter-native to
high Sulfur fuels, and,
Comparatively more refined liquid petroleum gas (LPG) or liquefied natu-ral gas
(LNG) can
be used instead of traditional high contaminant fuels such as coal.
✓ Process Modification:
The existing process may be changed by using modified techniques to control
emission at source. For example,
If coal is washed before pulverization, then fly- ash emissions are consider-ably
reduced.
If air intake of boiler furnace is adjusted, then
excess Fly-ash emissions at power
plants can
be reduced.
✓ Modification of Existing Equipment:
Air pollution can be considerably minimized by making suitable modifications
in the existing equipment:
• For example, smoke, carbon-monoxide and fumes can be reduced if open
hearth furnaces are replaced with controlled basic oxygen furnaces or
elec-tric furnaces.
• In petroleum refineries, loss of hydrocarbon vapours from storage tanks due
to evaporation,
temperature changes or displacement during filling etc.
can be reduced by designing the storage tanks with floating roof covers.
• the storage tanks in the above case can also give similar re-sults.
✓ Maintenance of Equipment:
An appreciable amount of pollution is caused due to poor maintenance of the
equipment which includes the leakage around ducts, pipes, valves and pumps etc.
Emission of pollutants due to negligence can be minimized by a routine checkup of
the seals and gaskets
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9.4.2 Pollution Control Equipment
Sometimes pollution control at source is not possible by preventing the
emis-sion of pollutants. Then it becomes necessary to install pollution control
equip-ment to remove the gaseous pollutants from the main gas stream.
The pollutants are present in high concentration at the source and as their
distance from the source increases, they become diluted by diffusing with
environmental air.
9.4.3 Diffusion of Pollutants in Air
Dilution of the contaminants in the atmosphere is another approach to the
con-trol of air pollution. If the pollution source releases only a small quantity of the
contaminants, then pollution is not noticeable as these pollutants easily diffuse into
the atmos-phere but if the quantity of air contaminants is beyond the limited
capacity of the environment to absorb the contaminants then pollution is caused.
However, dilution of the contaminants in the atmosphere can be accomplished
through the use of tall stacks which penetrate the upper atmospheric layers and
disperse the contaminants so that the ground level pollution is greatly re-duced. The
height of the stacks is usually kept 2 to 21/2 times the height of nearby structures.
Dilutions of pollutants in air depend on atmospheric temperature, speed and
direction of the wind. The disadvantage of the method is that it is a short-term contact
measure which in reality brings about highly undesirable long-range effects.
This is so because dilution only dilutes the contaminants to levels at which their
harmful effects are less noticeable near their original source whereas at a
considerable distance from the source these very contaminants eventually come
down in some form or another.
9.4.4 Vegetation
Plants contribute towards controlling air-pollution by utilizing carbon dioxide
and releasing oxygen in the process of photosynthesis. This purifies the air (re-moval
of gaseous pollutant—CO2) for the respiration of men and animals.
Gas-eous pollutants like carbon monoxide are fixed by some plants, namely, Coleus
Blumeri, Ficus variegata and Phascolus Vulgaris. Species of Pinus, Quercus, Pyrus,
Juniperus and Vitis depollute the air by metabolising nitrogen oxides. Plenty of trees
should be planted especially around those areas which are de-clared as high-risk
areas of pollution.
9.5.5 Zoning
This method of controlling air pollution can be adopted at the planning stages
of the city. Zoning advocates setting aside of separate areas for industries so that they
are far removed from the residential areas. The heavy industries should not be
located too close to each other.
New industries, as far as possible, should be established away from larger
cities (this will also keep a check on increasing concentration of urban population in
a few larger cities only) and the locational decisions of large industries should be
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guided by regional planning. The industrial estate of Bangalore is divided into three
zones namely light, medium and large industries. In Bangalore and Delhi very large
industries are not permitted.
9.5 AIR QUALITY MANAGEMENT
Republic Act No. 8749, otherwise known as the Philippine Clean Air Act of
1999, provides the policy framework for the country’s air quality management
program. It seeks to uphold the right of every Filipino to breathe clean air by
addressing
air
pollution
from
mobile
and
stationary
sources.
The law adheres to the Constitutional right of people to “a balanced and
healthful ecology in accord with the rhythm and harmony of nature.” It also believes
in the principle that “polluters must pay,” because a clean and healthy environment
is for the good of all and should, therefore be the concern of all.
RA 8749 focuses primarily on pollution prevention rather than control by
encouraging cooperation and self-regulation among citizens and industries. It also
enforces a system of accountability for adverse environmental impacts to heighten
compliance to government environmental regulations.
Some of the programs or activities implemented to achieve this objective are:
Linis/Ligtas Hangin Program with the Bantay Tambutso, Bantay Tsimnea and Bantay
Sunog; industrial enforcement program for stationary sources; designation of
attainment and non-attainment area sources; promotion of clean fuel; and strong
collaboration between government and stakeholders on measures to address
pollution.
The Environmental Management Bureau (EMB) is responsible for the
implementation and enforcement of R.A 8749, otherwise known as the “Philippine
Clean Air Act of 1999″, Its primary goal is to come out with a comprehensive national
program to achieve and maintain Air Quality that meets the National Air Quality
Guidelines for Criteria Pollutants and their Emissions Standards. while minimizing
the possible associated negative impacts on the country’s economy. its implementing
rules and regulation contain specific requirement that prohibit the vehicular and
industrial sources from emitting pollutants in amounts that cause significant
deterioration of air quality.
In support of these regulations, the EMB has drawn up the following
measures:
✓ Guidelines and Standards for dioxin and furans;
✓ Guidelines for the Accreditation by the Department of Trade and Industry
of
Emission Testing Centers for
smoke-belchers;
✓ Conduct of an Industrial Emission Project which would provide concessional
loans to
industries for air
pollution control equipment acquisition;
and,
✓ Establishment of an Air Emission Inventory Database
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