Definition = physical, chemical, biological changes in
water quality that adversely affect living organisms.
Infectious Agents = pathogenic organisms. Water-borne diseases
from infectious agents include typhoid, cholera, bacterial and
amoebic dysentery, polio, infectious hepatitis, guinea worm
and schistosomiasis. Due to lack of sanitation.
bacteria (E. coli).
Presume if coliform
bacteria are present,
infectious pathogens are
Types, sources, and effects of water pollutants
Major pollution problems of surface water
Major pollution problems of groundwater
Reduction and prevention of water pollution
Drinking water quality
Types, Effects, and Sources of Water
• Water is polluted by infectious bacteria, inorganic
and organic chemicals, and excess heat.
• Water pollution is any chemical, biological, or
physical change in water quality that has a harmful
effect on living organisms.
• The WHO estimates that 3.4 million people die
prematurely each year from waterborne diseases.
• In the U.S., an estimated 1.5 million people a year
become ill from infectious agents.
• Scientists monitor water quality by using bacterial
counts, chemical analysis, and indicator organisms.
• One method of measuring water quality involves
measuring the number of colonies of fecal coliform
bacteria present in a water sample.
• Drinking water should not contain any colonies/100
• Chemical analysis includes checking inorganic and
organic chemicals present, sediment content, and
turbidity of water.
• Indicator species are living organisms that are
monitored to determine levels of pollution.
Sources of Water Pollution
Supply of Water Resources
Freshwater Readily accessible freshwater
Arsenic from mining or drainage of desert soils
Causes: - anemia
Sodium Chloride: Salinization
Sulfur and nitrogen compounds from coal.
Causes: - pH changes which affect species
- leaches aluminum
Evaporation and transpiration
Well requiring a pump
Fig. 15-3 p. 308
Use of Water Resources
Humans use about 54% of reliable runoff
Point and Nonpoint Sources
Sources of water pollution
The leading sources of water pollution are
agriculture, industries, and mining.
1. Agricultural activities are the leading cause of
water pollution from
erosion, overgrazing, fertilizers and
pesticides, and excess salt from irrigated soils.
2. Industrial facilities are another large source of
water pollution, and mining is a third source.
• One of every five people in the world lacks access
to safe drinking water.
• Ninety-five percent of people in developed
countries and 74% of people in developing
countries have access to clean drinking water.
• In a warmer world, too much rain and too little
rain can increase water pollution.
Pollution of Freshwater Streams
Streams can recover from moderate levels of
degradable water pollutants if the flows are not
1. A combination of dilution and biodegradation can
allow recovery of stream pollution
2. The breakdown of pollutants by bacteria creates
an oxygen sag curve. Organisms that have a high
oxygen demand can’t survive in the curve.
3. Volume of the stream, volume of wastes entering,
flow rate, temperature, and pH levels all affect
how great a sag curve is produced.
Water Pollution: Now
Most developed countries have reduced point source
pollution, but toxic chemicals and pollution from
non-point sources are still problems.
Stream pollution in most developing countries is a
serious and growing problem. Half of the world’s
500 major rivers are heavily polluted, and most of
them run through developing countries where
waste treatment is minimal or nonexistent.
For example: Religious beliefs, cultural
traditions, poverty, little economic
development, and a large population interact to
cause severe pollution of the Ganges River in India.
Groundwater Pollution: Causes
Low flow rates Few bacteria
Leakage from faulty
Hazardous waste injection well
and solvent tank
Pollution of Groundwater
Experts rate groundwater pollution as a low-risk
ecological problem; it is rated as a high-risk
The extent of groundwater contamination is
Prevention is the most effective and affordable way
to protect groundwater from pollutants.
Problems with Using Groundwater
Water lable lowering
Reduced stream flows
• >70,000 chemicals are used not; effects of
many are not known
• Each year another 700-800 new chemicals are
• 55 million tons of hazardous chemical wastes are
produced in the US each year
• The 20 most abundant compounds in
groundwater at industrial waste disposal sites
include TCE, benzene, vinyl chloride…all are
carcinogens, and also affect liver, brain, and
Kinds of Water Pollution
• Inorganic Pollutants
• Organic Pollutants
• Biologic Pollutants
• Pb in gasoline
• Phosphorus, nitrogen (Great Lakes)
• Other heavy metals
• 3 groups
• 1) Produce no health effects until a threshold
concentration is exceeded—e.g., NO3 at
, 50mg/liter; at higher levels:
• 2) No threshold—e.g.—genotoxic substances:
some natural and synthetic organic
compounds, microorganic compunds, some
• 3) Essential to diets: F, I, Se—absence causes
problems, but too much also causes problems
Inorganic Trace Contaminants
• Mercury—methyl Hg and dimethyl Hg in
fish—probably most significant path to
humans—Minamata Bay, Japan, 1950’s
• Rhine River drains 185,000 sq km—heavily
polluted by 1970’s
• Lead—toxicity has been known for a long
– 1859 book
– Tetraethyl lead—anti-knowck additive for
Sources: offshore wells,
tankers, pipelines and
Effects: death of organisms, loss
of animal insulation and
Significant economic impacts
Mechanical cleanup methods: skimmers and blotters
Chemical cleanup methods: coagulants and dispersing
Solutions: Preventing and Reducing
Surface Water Pollution
Nonpoint Sources Point Sources
Buffer zone vegetation
Reduce soil erosion
Clean Water Act
Water Quality Act
Reducing Water Pollution through
• Primary and Secondary sewage treatment.