WATER POLLUTION
Chapter 20
What is water pollution?
Any physical, biological or chemical change in water quality that adversely affects living organisms or
makes water unsuitable for desired uses.
There are ...
1. Point sources of pollution discharge pollutants from specific locations that can be pinpointed and
identified.

e.g. factories, mines, oil wells, sewage pipes.
2. Nonpoint sources are scattered and diffuse, having no specific location where they discharge into a
particular body of water.

e.g. runoff from gardens and construction sites, farmland, streets and parking lots.
Atmospheric deposition caused by air currents and precipitated on watersheds or directly on the surface of
bodies of water is a form of nonpoint, diffuse source of pollution.
TYPES AND EFFECTS OF WATER POLLUTION
Infectious agents.
The most serious pollutants in terms of health are pathogenic organisms.


Typhoid, cholera, bacterial, amoebic dysentery, polio, infectious hepatitis, schistosomiasis.
Malaria, yellow fever and filariasis are transmitted by insects that have aquatic larvae.
Untreated or improperly treated human wastewater is the main source of these pathogens.
Water from feedlots and food processing factories are also a source of pathogens.
Coliform bacteria is a sign of waste contamination.
Oxygen-demanding wastes
Oxygen dissolved in water is a good indicator of water quality.
Oxygen in concentration of 6 ppm (parts per million) or higher will support fish and other aquatic life.
Organic waste stimulates oxygen consumption by bacteria, rotifers and other microorganims.
The impact of this waste on water quality is expressed in terms of BOD, biochemical oxygen demand.
BOD or biochemical oxygen demand: the amount of oxygen consumed by aquatic microorganisms over a
five day period.
Plant nutrients and cultural eutrophication.
Eutrophic waters are rich in organisms and aquatic life.
Oligotrophic waters have low biological productivity.
Lakes go through a progressive change from an oligotrophic to eutrophic state.
Human activity accelerates the eutrophication of bodies of water: cultural eutrophication.
Toxic inorganic materials.
Human activity introduces many toxic chemicals.

Heavy metals like lead, mercury, cadmium and nickel are highly toxic.

Nonmetallic salts such sodium chloride can reach levels that are toxic to plants and animals.

Acids and bases are products of industrial processes that change the pH of water to a toxic level.
Organic chemicals.
Pesticides, fertilizers, oils, gasoline, dyes, etc. are organic pollutants when they are discharged into bodies
of water.
Chemicals used in the making of plastic, paints, pharmaceuticals and other products are also pollutants.
Sediments.
Sediments and suspended solids are the main source of water pollution in the United States and many
other parts of the world.
Rivers have always carried sediments.
Erosion rates increased by human activity increase the sediment load of rivers.
Thermal pollution and thermal shock.
Rising or lowering water temperature from normal levels can greatly affect aquatic life.
Water temperatures are more stable than air temperatures and aquatic organisms are in general poorly
adapted to sudden changes in temperature.
Altering the vegetation cover and runoff patterns can affect water temperature.
Discharging water used in industrial cooling changes the temperature drastically.
WATER QUALITY
Areas of progress.
In 1948, about 1/3 of Americans were served by municipal sewage system. Most depended on cesspool
and septic tanks.
In 1972 the Clean Water Act established the National Pollution Discharge Elimination System (NPDSE)
A permit would be revoked for any industry, municipality and other entity dumping waste in surface
water.
As a consequence, only about 10% of our water pollution comes from industrial or municipal point
sources.
Sewage treatment has been on of the main improvements.
Remaining problems.
Nonpoint discharge are the main problems of water pollution at present time.
The sources are harder to identify.
About 3/4 of water pollution in the U.S. come from ...
1. soil erosion,
2. fallout air pollutants
3. surface runoff from urban areas.
In the U.S. as much as 25% of the fertilizers used in farming are carried away by runoff.
Other countries.
Japan, Australia and Western Europe also have improved surface water quality in recent years.
Wastewater treatment in Western Europe equals or surpasses that of U.S.

Sweden serves 98% of the population with secondary treatment; U.S. serves 70%.
Groundwater and drinking water.
95% of the population in the U.S. depend on aquifers for drinking water.
This source is threatened in many areas by overuse and pollution.

The United States E.P.A. estimates that every day some 1.5 trillion gallons of contaminated
water seep into the ground from cesspools, septic tanks, municipal and industrial landfills,
waste disposal sites, agricultural fields, and other human-impacted areas.
Fertilizers and pesticides contaminate ground water in agricultural areas.
Aquifers are threatened in the U.S. by the injection into the ground of oil field brime, effluents from
chemical plants, and treated sewage as an alternative to incineration and other treatment.
E.P.A. estimates that 58% of all hazardous waste generated in the U.S. are pumped into deep wells.

No permits are required and there are no limits on where and how it is done.
Ocean pollution.
Agricultural and urban runoff is a massive source of ocean pollution. It is little understood.
Few coastlines in the world remain uncontaminated by oil or oil products.
Often we do not understand what pollutant is causing distressing biological effects.
WATER POLLUTION CONTROL
Nonpoint sources are...




Agriculture
Urban runoff.
Construction sites.
Land disposal for industry, sewage treatment, solid waste, etc.
CLEAN WATER ACT
The Clean Water Act was established in 1972 by Congress to restore and maintain water purity.
It is a complex piece of legislature that regulates urban runoff, industrial discharge, municipal sewage,
land use, and wetland drainage.
The purpose was to restore U.S. surface waters to "swimmable and fishable" conditions.
It was approved about the same time as the Endangered Species Act and the Clean Air Act.
Natural processes have the ability to remove and destroy pollutants.
These natural systems become overloaded and ineffective when pollution levels are too high.
Wastewater treatment is effective in removing organic material but the sludge is often contaminated with
heavy metals and other toxic industrial chemical wastes.
Reducing the source of these materials is often the best solution.