Water Pollution
Objectives
Describe the sources and effects of some major types of water pollution
Appreciate why access to sewage treatment and clean water are important
Explain ways to control water pollution, including technological and legal
solutions
Water pollution
 Any physical, biological, or chemical change in water quality that adversely
affects living organisms can be considered pollution
Point sources
Discharge pollution from specific locations
Factories, power plants
Easy to control through regulations
Non-point sources
Non-point sources - Scattered or diffuse, having no specific location of
discharge
Agricultural fields, feedlots
Very difficult to monitor and regulate
Atmospheric deposition
 Ultimate in non-point source pollution
 Contaminants carried by air currents and precipitated into watersheds or
directly onto surface waters
Agricultural (atrazine, toxaphene) and industrial (PCBs, dioxins)
contaminants in the Great Lakes that cannot be accounted for by local
sources alone
 Most thought to have been deposited from the atmosphere
 Several studies have indicated health problems among people who
regularly eat Great Lakes fish
Infectious agents
 Main source of waterborne pathogens is improperly treated human waste
 Animal wastes from feedlots and fields is also important source of pathogens
Infectious agents
Infectious agents
 In developed countries, sewage treatment plants and pollution-control devices
have greatly reduced pathogens
 Waters monitored for coliform bacteria - intestinal bacteria including
Escherichia coli (E. coli)
Estimated 1.5 million Americans fall ill from fecal contamination annually
 Drinking water generally disinfected via chlorination
Oxygen-demanding wastes
Certain organic materials added to water stimulates oxygen consumption by
decomposers
Sewage
Paper pulp
Food-processing wastes
Oxygen-demanding wastes
 Water with an oxygen content > 6 ppm will support “desirable” aquatic life
 Water with < 2 ppm oxygen will support mainly detritis feeders and
decomposers (e.g. worms, bacteria, fungi)
 Oxygen is added to water by diffusion from wind and waves, and by
photosynthesis from green plants and algae
 Oxygen is removed from water by respiration and oxygen-consuming
chemical processes
Oxygen-demanding wastes
Effects of oxygen-demanding wastes on rivers depend on volume, flow, and
temperature of river water
Faster flowing water has more oxygen
Lower temperature water has more oxygen
Oxygen sag - oxygen levels decline downstream from a pollution source as
decomposers metabolize waste materials
Oxygen sag
Oxygen sag
Plant nutrients and cultural eutrophication
 Oligotrophic - Bodies of water that have clear water and low biological
productivity
 Eutrophic - Bodies of water that are rich in organisms and organic material
 Eutrophication - Process of increasing nutrient levels and biological
productivity
Some amount of eutrophication is normal
 Cultural eutrophication - Increase in biological productivity and ecosystem
succession caused by human activities
Eutrophication
Eutrophication
Gulf of Mexico hypoxia
 In 1974, scientists found areas where oxygen had disappeared from bottom
sediments and the water column
 First thought to be a minor natural disturbance
 Hypoxic area in 1993 after Mississippi floods doubled in size
 Stays from May to September
 Influx of nitrogen from Midwest/Great Plains is cause
 Hypoxic area continues to grow
Harmful algal blooms (HABs)
 HABs have become increasingly common in slow-moving and shallow waters,
usually due to pollution
 Algal blooms produce toxins
 Red tides are blooms of deadly aquatic algae
 Cryptosporidium in 1993 entered the Milwaukee public water supply, making
400,000 people sick and killing at least 100 people
Pfiesteria piscicida
 First discovered in 1988 in open sores in fish in Chesapeake Bay
 Very complicated life cycle
 No fewer than 24 different life forms
 In 1997, fish kills led to the closing of Pocomoke River to all shellfish and fish
harvests
 Economic loss was $15-20 million in MD alone
 Causes skin rashes, neurological disorders and death in humans
Inorganic pollutants
Metals
Many metals such as mercury, lead, cadmium, and nickel are highly toxic
Highly persistent and tend to bioaccumulate in food chains
Lead pipes are a serious source of drinking water pollution
Mine drainage is serious source of metal pollution in water
Inorganic pollutants
 Nonmetallic salts
 Many salts that are non-toxic at low concentrations can be mobilized by
irrigation and concentrated by evaporation, reaching levels toxic to plants
and animals
Leaching of road salts has had detrimental effect on many ecosystems
 Acids and bases
 Often released as by-products of industrial processes
Coal mining
 Acid precipitation
Organic chemicals
 Thousands of natural and synthetic organic chemicals are used to make
pesticides, plastics, pharmaceuticals, pigments, etc.
 Many are highly toxic and bioaccumulate
Organic chemicals
Two most important sources of toxic organic chemicals in water are:
Improper disposal of industrial and household wastes
Runoff of pesticides from high-use areas
Fields, roadsides, golf courses
Pesticide runoff
Sediment
Human activities have accelerated erosion rates in many areas
Human-induced erosion and runoff contribute about 75 billion metric tons of
suspended solids to world surfaces each year
Fills lakes, obstructs shipping channels, makes drinking water purification
more costly
Thermal pollution
Raising or lowering water temperatures from normal levels can adversely
affect water quality and aquatic life
Oxygen solubility in water decreases as temperatures increase
Species requiring high oxygen levels are adversely affected by warming
water
Thermal pollution
Caused by altering vegetation cover and runoff patterns
Industrial cooling processes often use heat-exchangers to extract excess heat,
and then discharge heated water back into original source
Ocean pollution
 Estimated 6 million metric tons of plastic bottles, packaging material, and other
litter tossed from ships into the ocean annually
Oil pollution
Few coastlines in the world remain uncontaminated by oil or oil products
Estimated 3-6 million metric tons of oil are discharged into the world’s
oceans
Transport creates opportunities for major spills
Oil pollution
Groundwater and drinking water
About half the U.S. population, and 95% of rural residents, depend on
underground aquifers for drinking water
For decades, groundwater was assumed impervious to pollution and was
considered the gold standard for water quality
Groundwater and drinking water
EPA estimates 4.5 trillion liters of contaminated water seep into the ground in
the U.S. every day
MTBE - Gasoline additive, and suspected carcinogen, is present in many
urban aquifers
In agricultural areas, fertilizers and pesticides commonly contaminate
aquifers and wells
Groundwater pollution
Water pollution control
Source reduction
Cheapest and most effective way to reduce pollution is avoid producing it
or releasing it into the environment
Studies show as much as 90% less road salt can be used without
significantly affecting winter road safety
Soil conservation
Non-point sources and land management
 Some main causes of non-point pollution:
 Agriculture
 Urban runoff
 Construction sites
 Land disposal
 Preserving wetlands
 In urban areas, reducing materials carried away by storm runoff is helpful
Watershed protection in the Catskills
 Water supply for New York City
 Worked with local farmers to reduce non-point pollution and preserve land
 Saved billions of dollars by performing watershed protection rather than
building a treatment plant
Human waste disposal
More than 500 pathogenic bacteria, viruses, and parasites can travel from
human or animal excrement through water
Natural processes
In many areas, outdoor urination and defecation is the norm
When population densities are low, natural processes can quickly
eliminate waste
Municipal sewage treatment
Primary Treatment - Physical separation of large solids from the waste stream
Secondary Treatment - Biological degradation of dissolved organic
compounds
Effluent from primary treatment transferred into trickling bed, or aeration
tank
Effluent from secondary treatment is usually disinfected (chlorinated)
before release into nearby waterway
Municipal sewage treatment
Tertiary treatment - Removal of plant nutrients (nitrates and phosphates) from
secondary effluent.
Chemicals, or natural wetlands
In many U.S. cities, sanitary sewers are connected to storm sewers
Heavy storms can overload the system, causing by-pass dumping of raw
sewage and toxic runoff directly into watercourses
Low-cost waste treatment
Living systems such as wetlands
Effluent flows through wetlands where it is filtered and cleaned by aquatic
plants and microscopic organisms
Water legislation
Clean Water Act (1972)
Goal was to return all U.S. surface waters to “fishable and swimmable”
conditions
For Point Sources, Discharge Permits and Best Practicable Control
Technology (BPT) are required
Clean Water Act (1972)
Areas of contention
Draining or filling of wetlands
Many consider this taking of private land
Un-funded mandates
State or local governments must spend monies not repaid by Congress
Other important water legislation
Safe Drinking Water Act (1974)
Regulates water quality
CERCLA (1980) (aka Superfund)
Cleans up abandoned or inactive sites
Great Lakes Water Quality Agreement (1972)
London Dumping Convention (1990)
Other important water legislation
Laws are only as good as:
To the degree they are not weakened
To the degree they are funded
Water quality today in US
Areas of Progress
In 1999, EPA reported 91.4% of all monitored river miles and 87.5% of all
accessed lake acres are suitable for their designated uses
Most progress due to municipal sewage treatment facilities
Remaining problems
 Greatest impediments to achieving national goals in water quality are
sediment, nutrients, and pathogens, especially from non-point discharges
 About three-quarters of water pollution in the U.S. comes from soil erosion,
air pollution fallout, and agricultural and urban runoff
Surface waters in other countries
 At least 2.5 billion people in less developed countries lack adequate sanitation,
and about half of these lack access to clean drinking water
 Sewage treatment in wealthier countries of Europe generally equal or surpass
the U.S.
 In Russia, only about half of the tap water supply is safe to drink
Surface waters in other countries
 In urban areas of South America, Africa, and Asia, 95% of all sewage is
discharged untreated into rivers
 Two-thirds of India’s surface waters are contaminated sufficiently to be
considered dangerous to human health