Water Quality &
General Types of
Water Pollution
Most of the Earth’s Freshwater
Is Not Available to Us
Water covers 71% of earth’s surface
 Freshwater availability – 0.024%



Groundwater, lakes, rivers, and streams
Hydrologic cycle
Movement of water in the seas, land, and air
 Driven by solar energy and gravity
 Distributed unevenly


Humans can alter the hydrologic cycle

Withdrawing water, polluting, climate change
Water Usage
 Irrigation
(70%)– watering crops
 Industry (20%)– coolant (power plant)
 Domestic and Municipal (10%)– drinking,
sewage, bathwater, dishwater & laundry

Virtual water
Not consumed;
used to
produce food
and other
products
Fig. 13-6, p. 322
Case Study: Freshwater
Resources in the United States
Freshwater supplies are not evenly
distributed, and one of every six people on
the planet does not have adequate access to
clean water
 We are using available freshwater
unsustainably by wasting it, polluting it, and
underpricing what is an irreplaceable natural
resource
 Effects our misuse are Floods, Drought, and
Pollution

TOO MUCH WATER
Problems include flooding, pollution of water
supply, and sewage seeping into ground.
 Heavy rainfall, rapid snowmelt, removal of
vegetation, and destruction of wetlands cause
flooding.
 Floodplains, which include wetlands, help
provide natural flood and erosion control,
maintain high water quality, and recharge
groundwater.
 To minimize floods, rivers have been narrowed
with levees and walls, and dammed to store
water.

TOO MUCH WATER
Tree plantation
Diverse
ecological
habitat
Evapotranspiration
Trees reduce soil
erosion from heavy
rain and wind
Roads
destabilize
hillsides
Agricultural
land
Tree roots
stabilize soil
Vegetation releases water
slowly and reduces flooding
Forested Hillside
Evapotranspiration decreases
Overgrazing accelerates soil
erosion by water and wind
Winds remove
fragile topsoil
Agricultural
land is flooded
and silted up
Gullies and
landslides
Heavy rain erodes topsoil
Silt from erosion fills
rivers and reservoirs
Rapid runoff
causes flooding
After Deforestation
Stepped Art
Fig. 13-29, p. 343
Too Little Water
Examples include drought and expanding deserts (desertification).
Groundwater / Aquifer Depletion

Most aquifers are renewable

Unless water is contaminated or removed
Aquifers provide drinking water for half
the world
 Water tables are falling in many parts of
the world, primarily from crop irrigation
 Groundwater used to supply cities and
grow food is being pumped from
aquifers in some areas faster than it is
renewed by precipitation

Groundwater &
Aquifers
Ogallala Aquifer

Groundwater or aquifers are water recharge areas that are
located beneath the ground surface in soil pore spaces and
fractures in the Earth’s formations. Natural discharge occurs
from springs and wetlands.
The water table measures the level of Earth’s land crust to which
the aquifer is filled or the division between saturated and
unsaturated rock.
Renewability rates of aquifers differ depending on the surrounding
conditions of the land and the water cycle. The circulation rate of
most aquifers is usually slow (300 to 4,600 years) compared to the
rate they are being depleted.
Ground Water Problems
Ground water problems
include pollution,
increase in salinity, and
draining too much.
 Sinkholes can form when
the roof of an
underground cavern
collapses from draining
too much water.
 Harms both humans and
endangers many species.

Case Study: Overpumping the
Ogallala

Ogallala aquifer – largest known aquifer
Extends from South Dakota to Texas
 Irrigates the Great Plains
 Very slow recharge
 Water table dropping


Water pumped 10-40 times faster than recharge
Government subsidies to continue farming deplete
the aquifer further
 Biodiversity threatened in some areas
 Northern states will still have ample supplies, but
for the south it’s getting thinner.

Groundwater Depletion:
A Growing Problem


Areas of
greatest aquifer
depletion from
groundwater
overdraft in the
continental U.S.
The Ogallala, the world’s largest aquifer, is
most of the red area in the center (Midwest).
Figure 13-5
Population Growth
 Problems
include over-drawing
fresh water, pollution, and overbuilding so that water can’t
seep into the ground.
Sharing Water Resources

There are water wars out west.
California bought the water from the
Colorado River, but Arizona wants it.
Who owns it? The same thing is
happening in Texas. More water rights
are sold than the actual amount of
water. How do you share water? This
is a problem all over the world.
U.S. Geological Survey projection, 2007: Water hotspots
Washington
Montana
Oregon
Idaho
Wyoming
By 2025,
areas around
world could
face intense
conflicts over
scarce water
Nevada
North
Dakota
South
Dakota
Nebraska
Utah
Colorado
California
Kansas
Oklahoma
Arizona
New
Mexico
Texas
Highly likely conflict potential
Substantial conflict potential
Moderate conflict potential
Unmet rural water needs
Fig. 13-8, p. 323
Overdrawing Surface Water
Case Study- Aral Sea


The Aral Sea has been greatly affected by water diversion
projects for irrigation and this has caused lake water levels to
drop. This has created a major ecological, economic, and
health disaster.(read pg. 332)
Effects of the dropping sea level :
Water has dropped 22 meters since 1961
The sea’s salinity has tripled
20 of the 24 native fish species have gone extinct.
About 85% of wetlands have been eliminated and 50% of
local bird and mammal species have disappeared.
1989
2008
2012
Stable Runoff

As water runs off from rain, it’s supposed to get
into rivers, and finally off to the sea. But when
we dam rivers, less goes to the ocean, meaning
the brackish water (where the river hits the
ocean) becomes more salty. This is the
breeding ground for many fish and
invertebrates. This harms the ecology of the
area.
Salinization of Irrigated Soil
 Water
is poured onto soil and
evaporates. Over time, as this is
repeated, nothing will grow there
anymore.
Impacts of Human Activities on
Freshwater Systems

Dams, cities, farmlands, and filled-in wetlands
alter and degrade freshwater habitats.
 Dams, diversions and canals have fragmented
about 40% of the world’s 237 large rivers.
 Flood control levees and dikes alter and
destroy aquatic habitats.
 Cities and farmlands add pollutants and excess
plant nutrients to streams and rivers.
 Many inland wetlands have been drained or
filled for agriculture or (sub)urban
development.
Water Management
Dams and Reservoirs
•Description: A dammed stream that can
capture & store water from rain & melted snow.
•Benefits: Hydroelectric power; provides water
to towns; recreation; controls floods downstream
• Problems: Reduces downstream flow;
prevents water from reaching the sea (Colorado
River) devastates fish life; reduces biodiversity.
USING DAMS AND RESERVOIRS
TO SUPPLY MORE WATER

Large dams and reservoirs can produce
cheap electricity, reduce downstream
flooding, and provide year-round water
for irrigating cropland, but they also
displace people and disrupt aquatic
systems.
Provides water
for year-round
irrigation of
cropland
Provides
water for
drinking
Reservoir is
useful for
recreation
and fishing
Can produce
cheap
electricity
(hydropower)
Downstream
flooding is
reduced
Flooded land
destroys forests
or cropland and
displaces people
Large losses of
water through
evaporation
Downstream
cropland and
estuaries are
deprived of
nutrient-rich silt
Risk of
failure and
devastating
downstream
flooding
Migration and
spawning of
some fish are
disrupted
Fig. 13-13a, p. 328
Powerlines
Reservoir
Dam
Intake
Powerhouse
Turbine
Fig. 13-13a, p. 328
Case Study:
Colorado River
Issues

The Colorado River has so many
dams and withdrawals that it often
does not reach the ocean.


Has 14 major dams , reservoirs, and
canals.
Flows through seven states and two
countries, with much of its course
through desert.

Large quantities of water removed
from it every year to reservoirs in
other parts of the country.

Many endangered species live in or
along the course of the river.
Lake Powell, is
the second largest
reservoir in the
U.S.
Colorado River
Issues
Glen Canyon Dam

Advantages of a river’s use are:
provides water for more than
24 million people
irrigates 2 million acres of land
provides major tourist
attractions
provides 4,000 MW of
electricity

Disadvantages of a river’s use are:
lowered water quality
river delta affected by low water
flows
loss of habitat for many animals
major construction and diversion
issues
Aswan High Dam

Two dams straddle the Nile River at Aswan, Egypt.
Completed in 1970 and formed Lake Nasser which is 550 km
long and capable of holding two years of the Nile's annual
flow.

The main objectives of the project were:
energy generation in a renewable form.
flood control in downstream locations.
provision of water for agriculture and domestic use.

A serious detrimental effect is the loss of the annual floods
downstream. These used to replenish the nutrients of the
flood plain and flush out accumulated salts.
Wiki Commons
Aswan High Dam
‣ Without flooding, fertilizers must be applied to the land and
salts build up in the soils, causing crops to fail.
‣ Without annual deposition of river sediments because of buildup behind the dam, the land is eroding, allowing the sea to
encroach up the river delta.
‣ Damming has also caused 64% of commercially fished species
in the Nile to disappear.
‣ Time will tell if better management will help to reverse the
Photo: NASA
problems currently being experienced in the Nile Delta region.

Photo: Guuganji Creative Commons Attribution ShareAlike 3.0

Spans the Yangtze River
at Sandouping, China,
and is the largest
hydroelectric dam in the
world, capable of
producing 22,500MW of
electricity. (equal to 18
large coal burning plants
or nuclear power plants)
Major construction began
in 1994 and was
completed by 2012.
Debate over whether
advantages will out way
disadvantages.
Creative Commons Attribution ShareAlike 3.0

Photo: Christoph FlinkoBl
Three
Gorges Dam
Three Gorges Dam Issues

Advantages of construction:
reduction of coal use in coal fired
power stations
flood control downstream
drought relief
Photo: BS Thurner Hof Creative Commons Attribution ShareAlike 3.0
better navigation of the river by
ships

Disadvantages of construction:
submergence of wetlands and
agricultural lands
loss of endangered plant and
animal habitats
archaeological sites flooded
upstream
The critically endangered Siberian crane
uses wetlands for winter feeding that will be
flooded by the Three Gorges Dam.
towns and cities flooded and 1.2
million people displaced
Built over seismatic fault and
already has small cracks.
Dam Removal

Some dams are being removed for ecological
reasons and because they have outlived their
usefulness.
In 1998 the U.S. Army Corps of Engineers
announced that it would no longer build large dams
and diversion projects in the U.S.
 The Federal Energy Regulatory Commission has
approved the removal of nearly 500 dams.
 Removing dams can reestablish ecosystems, but
can also re-release toxicants into the environment.

Water Diversion
•Description: Damming a river to
control where the water flows
•Benefits: Keeps water where we
want it- cities!
•Problems: Drains wetlands, destroys
land
Desalinization
•Description: Removing salt from salt
water
•Benefits: Freshwater
•Problems: Uses lots of energy; costs
3-5X’s more money; what do we do
with the salt?
DESALTING SEAWATER

Removing salt from seawater by current
methods is expensive and produces large
amounts of salty wastewater that must be
disposed of safely.

Distillation: heating saltwater until it
evaporates, leaves behind water in solid form.
 Reverse osmosis: uses high pressure to force
saltwater through a membrane filter.
SEEDING CLOUDS, AND TOWING
ICEBERGS AND GIANT BAGGIES

Seeding clouds with tiny
particles of chemicals to
increase rainfall, towing
icebergs or huge bags
filled with freshwater to
dry coastal areas have all
been proposed but are
unlikely to provide
significant amounts of
freshwater.
Harvesting Icebergs
•Description: Towing massive icebergs to arid
coastal areas (S. California; Saudi Arabia)
•Benefits: freshwater
•Problems: Technology not available; costs
too high; raise temperatures around the earth.
INCREASING WATER SUPPLIES BY
WASTING LESS WATER
Sixty percent of world’s irrigation water is
currently wasted, but improved irrigation
techniques could cut this waste to 5-20%.
 Drip Method – delivers water directly to
root. 90-95% efficient.
 Center-pivot, low pressure sprinklers sprays
water directly onto crop.

80% of water reaches crop.
 Has reduced depletion of Ogallala aquifer in
Texas High Plains by 30%.

Drip irrigation
(efficiency 90–95%)
Gravity flow
(efficiency 60% and
80% with surge
valves)
Center pivot
(efficiency 80%–95%)
Water usually comes from
an aqueduct system or a
nearby river.
Above- or belowground pipes or tubes
deliver water to
individual plant roots.
Water usually pumped
from underground and
sprayed from mobile
boom with sprinklers.
Conservation
Using less water or saving the
water we have
 Industry

Recycle water
Irrigation
 Surge flow (gravity)
 Drip irrigation $$
 Municipal uses
 Incentives and regulations
limiting water use
 Gray water

Benefits: Saves
money and wildlife
 Problems:
bothersome to
people; lack of
caring; laziness

Pollution
WATER POLLUTION: SOURCES,
TYPES, AND EFFECTS

Water pollution is any chemical, biological,
or physical change in water quality that has a
harmful effect on living organisms or makes
water unsuitable for desired uses.

Point source: specific location such as a factory
or sewage treatment plant (drain pipes, ditches,
sewer lines).
 Nonpoint source: cannot be traced to a single
site of discharge (atmospheric deposition,
agricultural / industrial / residential runoff)
Point and Nonpoint Sources of Pollution
Sources of Pollution
Agriculture
 Fertilizers, pesticides,animal wastes, sediment
eroded from the land
 Municipal Waste
 Sewage, fertilizers, dumping into drainage ditches,
etc.
 Industrial Waste
 Chemicals left over from manufacturing, waste
products, etc.
 Mining
 Erosion and toxic chemicals

Types of Water Pollutants
Inorganic Wastes
 Organic Wastes
 Sediments
 Thermal
 Radioactive
 Pathogens

In the Ganges River in India the
people drink, wash clothes and
use the restroom all in the same
water.
Inorganic Compounds
Mineral, not biological, in origin.
 Contaminants that contain
elements other than carbon.
 Ex. include acids, salts, and
heavy metals like mercury and
lead.
 Many find their way into both
surface water and groundwater
from sources such as industries,
mines, irrigation runoff, oil drilling
and urban runoff from storm
sewers.

Inorganic Compounds
Causes
 Nitrates and phosphates come
from sources such as human
and animal wastes, plant
residues, atmospheric
deposition and residential land.
Environmental Effects
 Some of these inorganic
pollutants are toxic to aquatic
organisms.

Bioaccumulation, biomagnification
Health Effects
Lead and mercury are poisonous. Mercury
exposure to developing fetuses in pregnant
women has been linked to a variety of
conditions such as mental retardations, cerebral
palsy, and developing delays, causes kidney
disorders and several damage the nervous and
cardiovascular systems.
 Low levels of mercury in the brain cause
neurological problems such as headache,
depression, and quarrelsome behavior.

Plant and Algal Nutrients

Chemicals such as nitrogen and phosphorus
that stimulate the growth of plants and algae.
Known as eutrophication.
Eutrophication
Definition
 The enrichment of a lake or pond by
inorganic plant and algal nutrients
such as phosphorus.
 Because this gets into our water
supply from runoff, etc., and is
something that is not normally in the
water, it is considered pollution.
Eutrophication
Cause/Effect
 Fertilizers, erosion, sewage, etc. get into
water and the effect is high
photosynthetic productivity.
Environmental Effects
 Excess nutrients encourage excessive
growth of algal and aquatic plants. This
causes problems, including enrichment
and bad odor. (Dead Zone or hypoxia)

water is cloudy and has layer of algae and
cyanobacteria.
Area of ocean/sea in which the oxygen has been depleted to
the point that most animals and bacteria cannot survive.
Caused by runoff of chemicals and animal/human wastes

Low oxygen conditions
Hypoxia

No oxygen conditions
Anoxia
Natural Vs. Cultural Eutrophication

Eutrophication
natural aquatic succession of nutrient
enrichment, mostly from runoff of plant nutrients
from the surrounding land.
 occurs over several hundred years


Cultural eutrophication
drive by human activities
 occurs rapidly


85% of large lakes near major population centers in
the U.S. have some degree of cultural eutrophication.
Organic Compounds
Definition
 Chemicals that contain carbon. Most found
in water are synthetic chemicals.
Causes
 Produced by human activities; these
included pesticides, solvents, detergents,
gas, industrial chemicals and plastics, and
seepage from landfills.
Organic Compounds
Health Effects
 Hundreds of synthetic organic
compounds are toxic and some of
these have been shown to cause
cancer or birth defects.
Environmental Effects
 Seeps into ground/surface waters
from land fills
 Leaches into ground from runoff
Sediment Pollution
Definition
 Excessive amounts of suspended soil particles
that eventually settle out and accumulate on
the bottom of a body of water. (Turbidity)
Causes
 Erosion of agricultural lands, forest soils
exposed by logging, degraded stream banks,
overgrazed rangelands, strip mines, and
construction.
Environmental Effects

Reduces light
penetration,
covering
aquatic
organisms,
bringing
insoluble toxic
pollutants into
the water,
and filling in
waterways.
Health Effects
Sediments adversely affect water
quality by carrying toxic chemicals.
 The sediment particles provide surface
area to which some insoluble, toxic
compounds adhere; when the
sediments enter the water, so do toxic
chemicals.
 Disease-causing agents can also be
transported into water via sediments.

Radioactive Substances
 Contains
atoms of unstable isotopes
that spontaneously emit radiation such
as uranium, plutonium and thorium
Radioactive Substances
Causes
 Get into water from mining and processing of
radioactive minerals, nuclear weapons
industry, or medical/scientific research.
Environmental Effects
 Pollutes air, water and soil.
Health Effects
 Mutations, birth defects, mental retardation,
genetic disease, leukemia, cancer (breast,
bone, thyroid, skin, lung), burns, cataracts,
male sterility.
Thermal Pollution
Definition
 Unnatural heating of water changing the ambient
temperature
Causes
 When heated water produced during certain
industrial processes is released into waterways.
Environmental Effects
 Decomposition of wastes occurs faster, depleting
the water of oxygen; this affects aquatic life.
Thermal Pollution / Dissolved Oxygen
Health Effects
 Typically affects animals, not humans.

Water quality and dissolved oxygen (DO) content in
parts per million (ppm) at 20°C.
 Only a few fish species can survive in water less
than 4ppm at 20°C.
Pollution of Freshwater Streams

Flowing streams can recover from a
moderate level of degradable water
pollutants if they are not overloaded and
their flows are not reduced.

In a flowing stream, the breakdown of
degradable wastes by bacteria depletes DO
and creates and oxygen sag curve.

This reduces or eliminates populations of organisms
with high oxygen requirements.
Water Pollution Problems: Streams

Dilution and decay of degradable, oxygendemanding wastes and heat in a stream.
Pollution of Freshwater Streams
Most developed countries have sharply
reduced point-source pollution but toxic
chemicals and pollution from nonpoint
sources are still a problem.
 Stream pollution from discharges of
untreated sewage and industrial wastes is
a major problem in developing countries.

Pollution of Freshwater Lakes

Dilution of pollutants in lakes is less effective
than in most streams because most lake
water is not mixed well and has little flow.
Lakes and reservoirs are often stratified and
undergo little mixing.
 Low flow makes them susceptible to runoff.


Various human activities can overload lakes
with plant nutrients, which decrease DO and
kill some aquatic species.
Ocean Pollution

North Pacific Garbage Patch
Two rotating gyres
 On or just beneath the water surface
 Tiny plastic pieces harmful to wildlife


Crude and refined petroleum


Highly disruptive pollutants
Largest source of ocean oil pollution

Urban and industrial runoff from land
Oil Spills
 When
a tanker accident happens, it gets lots
of publicity. EX. 1989 – Exxon Valdez, oil tanker
 But, more oil is released by normal operation
of offshore wells, washing tankers & from
pipeline or storage tank leaks. EX. 2010 – BP
Deepwater Horizon in the Gulf of Mexico
 Estimated
that oil companies spill, leak, or
waste per year an amount of oil equal to
that shipped by 1000 huge Exxon Valdez
tankers.
Floating Oil
 Oil
coats the feathers of birds (especially
diving birds) and the fur of marine
animals, destroying the animals’ natural
insulation and buoyancy
 Many drown or die of exposure from loss
of body heat.

Heavy oil components sink

Affect the bottom dwellers
Other Information
Oil is broken down by bacteria over time;
slower in cold waters.
 Heavy oil components can smother bottomdwelling organisms such as crabs, oysters,
mussels, and clams, or make them unfit to eat.
 Oil spills have killed coral reefs. A recent study
showed that diesel oil becomes more toxic to
marine life with the passage of time.

Methods of Clean
Mechanical



Floating booms contain the
oil spill or keep it from
reaching sensitive areas
Skimmer boats are used to
vacuum up some of the oil
into collection barges
Absorbent pads or large
feather-filled pillows are used
to soak up oil on beaches or
in waters that are too
shallow for skimmer boats
Chemical



Coagulating agents cause
floating oil to clump together
for easier pickup or sink to
the bottom, where it usually
does less harm.
Dispersing agents break up
oil slicks. However, these
can also damage some types
of organisms.
Fire can also burn off floating
oil, but crude oil is hard to
ignite.
Case Study: The BP Deepwater
Horizon Oil-Rig Spill

Spill from deep-sea oil drilling – 1 mile
deep
Released 4.9 million barrels of crude oil
 Contaminated vast areas of coastline
 Caused by equipment failure and poor
decisions


Government developed new standards
for offshore drilling procedures
Drinking Water
Problems
Sewage
Causes
 Release of waste water from drains or sewers
(toilets, washing machines, and showers) and
include human wastes, soaps and detergents
Environmental Effects
 Enrichment – the fertilization of a body of
water, caused by the presence of high levels of
plants and algal nutrients like nitrogen and
phosphorus
Sewage
Health Effects
 Oxygen
– dissolved oxygen is
needed by organisms, like fish, but
when sewage enters an aquatic
ecosystem, the micro-organisms
bloom, leaving less oxygen for the
fish, etc., and then they die
Sewage
carries diseasecausing agents.
Coliform Bacteria
The W.H.O. recommends there be zero
colonies of bacteria per 100ml of drinking water
and 200 colonies per 100ml of swimming
water.
 Average human excretes 2 billion organisms
per day.
 These are organic wastes that can be
decomposed by aerobic bacteria (causes lack
of oxygen). Fish die as a result of a lack of
oxygen

Disease-Causing Agents
Causes
 Comes from the wastes of infected
individuals.
Environmental Effects
 Municipal wastewater contains bacteria,
viruses, protozoa, parasitic worms, and
other infectious agents that cause human
or animal diseases.
Health Effects
Typhoid, cholera, bacterial
dysentery, polio and infectious
hepatitis are some of the
more common bacteria or
viruses that are transmitted
through contaminated food
and water.
 An estimated 1.6 million
people die every year, mostly
under the age of five

Table 21-2, p. 495
Global Outlook: Stream Pollution
in Developing Countries
Half of the world’s 500
major rivers are
polluted by untreated
sewage or industrial
waste.
 Many China's rivers are
greenish black from
uncontrolled pollution
by thousands of
factories.

Case Study: India’s Ganges River:
Religion, Poverty, and Health

Religious beliefs, cultural traditions, poverty,
and a large population interact to cause
severe pollution of the Ganges River in India.
Very little of the sewage is treated.
 Hindu believe in cremating the dead to free the
soul and throwing the ashes in the holy Ganges.

Some are too poor to afford the wood to fully
cremate.
 Decomposing bodies promote disease and depletes
DO.

Case Study: India’s Ganges River:
Religion, Poverty, and Health

Daily, more than 1
million Hindus in
India bathe, drink
from, or carry out
religious
ceremonies in the
highly polluted
Ganges River.
Figure 21-6
Pollution in Great Lakes and Mississippi

Mississippi and Great Lakes polluted
Raw sewage and biological pollution
 Nonpoint runoff of pesticides and fertilizers
 Atmospheric deposition of pesticides and Hg


1972 – Canada and the United States Great
Lakes pollution control program
Decreased industrial wastes and banned
phosphate containing household products.
 Decreased algal blooms
 Increased dissolved oxygen and fishing catches
 Better sewage treatment plants

How Can We Deal with Water
Pollution?

Reducing water pollution requires that
we:
Prevent it
 Work with nature to treat sewage
 Use natural resources far more efficiently


Reduce flow of pollution from land
Land-use
 Air pollution
 Linked to energy and climate policy



Controlling Sources of Pollution
Point Sources
Ban phosphate detergents
 Sewage-treatment improvements

Nonpoint Sources

Difficult to address runoff
pollutants
Urban
 Agricultural fields
 Deforested woodlands
 Overgrazed pastures


Best Management Practices (BMP)
SEWAGE TREATMENT
Reducing Water Pollution through
Sewage Treatment

Septic tanks and various levels of
sewage treatment can reduce pointsource water pollution.
Figure 21-15
Sewage Treatment
Raw sewage reaching a municipal sewage
treatment plant typically undergoes:
 Primary sewage treatment: a physical process that
uses screens and a grit tank to remove large floating
objects and allows settling.
 Secondary sewage treatment: a biological process
in which aerobic bacteria remove as much as 90% of
dissolved and biodegradable, oxygen demanding
organic wastes.
 Tertiary sewage treatment: a mixture of processes
that includes chlorine disinfection
Water Treatment
Primary

Removes suspended and floating
particles, such as sand and silt, by
mechanical processes such as screening
and gravitational settling. The solid
material that is settled out is called
primary sludge.
Bar screens, grit
chambers,
primary
clarifiers,
digesters and
pre-aeration
Secondary

Uses microorganisms to decompose the
suspended organic material in
wastewater. Ex. trickling filters – where
wastewater trickles through aerated
rock beds that contain bacteria and
other microorganisms, which degrade
the organic material in the water.
Secondary (Cont.)
Or activated sludge process – wastewater is
aerated and circulated through bacteria-rich
particles; the bacteria degrade suspended
organic material. After several hours, the
particles and microorganisms are allowed to
settle out, forming secondary sludge.
 Use aeration basins, settling tanks and sand
filters

Tertiary Water Treatment

This includes a variety of biological, chemical and
physical processes

used to remove phosphorus and nitrogen, the nutrients most
commonly associated with enrichment.
Tertiary treatment can also be used to purify
wastewater so that it can be reused in communities
where water is scarce.
 Use chlorine as a disinfection and then chlorine is
removed by SO2 so it can be released into river.
 Ozone (O3) is also used but leaves no residual
disinfectant. UV light does the same.

Reducing Water Pollution through Sewage Treatment
Primary
Bar screen Grit chamber
Raw sewage
from sewers
Secondary
Settling tank
Aeration tank
Settling tank
Sludge
Activated sludge
Chlorine
disinfection tank
To river,
lake, or
ocean
(kills bacteria)
Air pump
Sludge digester
Sludge drying bed
Disposed of
in landfill or
ocean or
applied to
cropland,
pasture, or
rangeland
Fig. 20-24, p. 566
Reducing Water Pollution through
Sewage Treatment
Sewage sludge can be used as a soil
conditioner but this can cause health problems
if it contains infectious bacteria and toxic
chemicals.
 Preventing toxic chemicals from reaching
sewage treatment plants would eliminate such
chemicals from the sludge and water
discharged from such plants.
 However, most sewage treatment plants are
not designed to remove pharmaceuticals

Reducing Water Pollution through
Sewage Treatment

Natural and artificial wetlands and other
ecological systems can be used to treat
sewage.

California created a 65 hectare wetland
near Humboldt Bay that acts as a natural
wastewater treatment plant for the town of
16,000 people.

The project cost less than half of the estimated
price of a conventional treatment plant.
Core Case Study: Using Nature to
Purify Sewage

Ecological wastewater
purification by a
living machine.

Uses the sun and a
series of tanks
containing plants,
snails, zooplankton,
crayfish, and fish (that
can be eaten or sold
for bait).
Pollution Prevention
 Water monitoring
 Analytical technology
 Leak detection systems
 Contained storage systems
 Regulation
 Enforcement
Water Quality: United States

Groundwater contamination still occurs,
especially due to non-point source
pollution, but laws like the Safe
Drinking Water Act, Clean Water Act,
and Water Quality Act have helped in
the U.S.
Water Quality: Global Problems

According to the World Health
Organization, an estimated 1.4 billion
people still do not have access to
adequate sanitation systems.
Worldwide, at least 250 million cases of
water-related illnesses occur each year,
with 5 million or more of these resulting
in death.
Specific Water Quality Measures
Dissolved Oxygen
 The amount of oxygen gas dissolved in a given
volume of water at a particular temperature and
pressure.
Carbon Dioxide
 Enters aquatic systems from the atmosphere and from
respiration by animals.
 The concentration of CO2 varies at different depths
because of light/photosynthesis.
Water Quality Measures
Nitrate
 Contaminates shallow groundwater (100 feet or less)
and usually comes from fertilizers. A concern in rural
areas where 80-90% of the residents use shallow
groundwater for drinking. Harms humans because it
reduces the blood’s ability to transport oxygen.
Sulfate
 Problem because too much can kill fish. Gets in water
from industrial processes and mining.
Water Quality Measures
Iron
 Causes problems because it separates out of the
water and forms particulates (sediment), it tastes bad
if it gets in our water, and can coat fish’s gills.
Groundwater problems in wells, from natural minerals
in rocks.
Phosphate
 Plant nutrients that cause algae blooms. It comes
from detergents, human wastes and fertilizers.
Water Quality Measures
Coliform
 General group of bacteria from animal wastes. It uses
up available oxygen. Also causes e-coli disease.
Giardia
 Organism (protozoa) that can cause diarrhea if you
drink unchlorinated water. It is a natural organism
that lives in the guts of animals.
Turbidity
 Cloudiness/muddiness; blocks the light; coats fish
gills.
Water Quality Measures
Chloride
 Part of salts, but too many can cause too
much salt in the water. Too much is bad;
a little is okay. It is naturally found in
water, but can come from pollution.
pH
 Too high/too low can be bad; fish like 6.59.5; acid mine drainage can kill fish.
Water Quality Measures
Hardness
 Calcium and magnesium dissolved in the
water. A little is good (50-400 ppm for
fish is good), but very low or high is a
problem. Low is more of a problem.
Affects fish eggs, poor bone development.
 Can cause problems with cleaning clothes.
Soap doesn’t bubble as much.
Methods of Treating Water
Ion Exchange
 Substitute sodium for calcium and
magnesium. Water softeners usually do
this.
Reverse Osmosis
 Membrane system that allows water to go
through but calcium and magnesium
cannot.
Pollution of Groundwater

Leaks from a number of sources have
contaminated groundwater in parts of the
world.
According the the EPA, one or more organic
chemicals contaminate about 45% of municipal
groundwater supplies.
 By 2003, the EPA had completed the cleanup of
297,000 of 436,000 underground tanks leaking
gasoline, diesel fuel, home heating oil, or toxic
solvents.

Case Study: Arsenic in Groundwater
Toxic Arsenic (As) can naturally occur at high
levels in soil and rocks.
 Drilling into aquifers can release As into
drinking water supplies.
 According to WHO, more than 112 million
people are drinking water with As levels 5100 times the 10 ppb standard.


Mostly in Bangladesh, China, and West Bengal,
India.
Water Legislation
1974 Safe Drinking Water Act
 Required the EPA to determine the maximum
contaminant level, the max permissible amount
of any pollutant that might adversely affect
human health.
 Health scientists


Strengthen law
Water-polluting companies

Weaken law
Water Legislation

Most developed countries use laws to set
water pollution standards, but such laws
rarely exist in developing countries.
The U.S. Clean Water Act sets standards for
allowed levels of key water pollutants and
requires polluters to get permits.
 EPA is experimenting with a discharge
trading policy similar to that for air pollution
control.

Water Legislation
1972 Clean Water Act
 Has two basic goals:
 To eliminate the discharge of pollutants in
U.S. waterways especially in high amounts
 To attain water quality levels that make
these waterways safe for recreation like
fishing and swimming.
1987 Water Quality Act
(Amended Clean Water Act)
Controlling toxic pollutant discharges
 Control non-point sources of pollution
 Authorized $18 billion for wastewater
treatment
 Address problems such as coastal
estuaries, the Great Lakes, and the
Chesapeake Bay

Using Laws: Protect Drinking Water
The U.N. estimates that 5.6 million Americans
drink water that does not meet EPA standards.
 1 in 5 Americans drinks water from a treatment
plant that violated one or more safety standard.
 Industry pressures to weaken the Safe Drinking
Act:

Eliminate national tests and public notification of
violations.
 Allow rights to pollute if provider cannot afford to
comply.

Is Bottled Water the Answer?

Some bottled water is not as pure as
tap water and costs much more.
1.4 million metric tons of plastic bottles are
thrown away.
 Fossil fuels are used to make plastic
bottles.


The oil used to produce plastic bottles in the
U.S. each year would fuel 100,000 cars.