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Water Pollution & Cleanup
11 June 2010 Water-Pollution.ppt 1
Water pollution
• Classes of pollution, pollutants – Pathogens, parasites– Oxygen-demanding wastes– Inorganic chemicals– Inorganic plant nutrients– Organic chemicals– Sediments– Radioactive material– Heat (thermal pollution)
11 June 2010 Water-Pollution.ppt 2
Water pollution
• Pathogens, parasites – Usually from sewage, feedlots, slaughterhouses
– Viruses
– Bacteria (cholera, ...)• Coliform bacteria usually not pathogenic,
• Used as indicators of pollution
– Protozoan parasites (Giardia, Cryptosporidium)
11 June 2010 Water-Pollution.ppt 3
Water pollution
• Oxygen-demanding wastes– Organic materials from sewage,
slaughterhouses, etc.
– Decomposed by bacteria• Bacteria require, consume dissolved oxygen
– “Biological Oxygen Demand” (BOD)• Measure of water quality
• Low in pristine water
11 June 2010 Water-Pollution.ppt 4
Water pollution
• Inorganic chemicals–Mostly from industry– Heavy metals • Lead, arsenic, mercury, copper ions, etc.
– Ammonia– Acids• Sulfuric acid, nitric acid from acid deposition• Also from industry
– Bases (caustic alkalines)
11 June 2010 Water-Pollution.ppt 5
Water pollution
• Inorganic plant nutrients (fertilizers)– From agriculture, lawns & gardens• Leaching into groundwater
• Run-off into surface waters
– Stimulate growth of algae (algal blooms), eutrophication• Algae die, sink, become oxygen-demanding
waste
11 June 2010 Water-Pollution.ppt 6
Water pollution
• Inorganic plant nutrients (fertilizers)– From agriculture, lawns
& gardens
– Eutrophication • Natural process
• Accelerated by excess nutrient input
• Algae die, sink, become oxygen-demanding waste
11 June 2010 Water-Pollution.ppt 7
Water pollution
• Organic chemicals– from industry, restaurants, cars, households,
farms– Gasoline, oil– Engine coolant (ethylene glycol)– Solvents– Detergents– Pesticides • insecticides, herbicides, fungicides
– Polychlorinated Biphenyls (PCBs)
11 June 2010 Water-Pollution.ppt 8
Water pollution
• Sediments– Erosion from construction sites, streets &
roads, farms, sewage
– Dense sediments sink, accumulate• Sedimentation in reservoirs
– Less dense sediments may stay in water• Reduce clarity (increase turbidity)
• Reduce light penetration & photosynthesis
11 June 2010 Water-Pollution.ppt 9
Water pollution
• Radioactive material– From spills, waste from atomic weapons production
• Hanford, Washington
• Savannah River Plant, South Carolina
– From nuclear power plants (minor)• Closely regulated
• Heat (“thermal pollution”)– Heated water from cooling of electrical generating
equipment
– Alters ecosystem of river, lake
11 June 2010 Water-Pollution.ppt 10
Water pollution
• Non-point and Point sources
11 June 2010 Water-Pollution.ppt 11
Ground water pollution
• Pollution of aquifers• Non-point and Point sources– Pollutants slow to break down in cold & dark
11 June 2010 Water-Pollution.ppt 12
Water pollution
• In lakes, reservoirs– Low flow rate, long
residence time
– Deep, stratification
– Pollutants can accumulate, concentrate
11 June 2010 Water-Pollution.ppt 13
Water pollution
• In streams, rivers– Higher flow rate,
dilution effect– Turbulent
• Well mixed• Well oxygenated
– Long riverbanks, contact with land• Subject to non-point
source pollutants
– Often flow near cities
11 June 2010 Water-Pollution.ppt 14
Water pollution
• Prevention– Better to NOT pollute than to clean up later• Clean up is expensive• Clean up is never complete
11 June 2010 Water-Pollution.ppt 15
Sewage Treatment
• Primary– Screens and settling tanks remove grit &
suspended organic matter.• Secondary– Sewage aerated; aerobic bacteria consume organic
matter– Leave dissolved inorganics, NO3, PO4, etc.
• Tertiary– Filters most dissolved inorganics and remaining
dissolved organic compounds
11 June 2010 Water-Pollution.ppt 16
Sewage Treatment
• Primary– Screens and settling tanks remove grit &
suspended organic matter.
11 June 2010 Water-Pollution.ppt 17
Sewage Treatment
• Secondary– Sewage aerated; aerobic bacteria consume organic matter– Leave dissolved inorganics, NO3, PO4, etc.
11 June 2010 Water-Pollution.ppt 18
Sewage Treatment
• Tertiary– Filters most dissolved
inorganics and remaining dissolved organic compounds
– Can be done biologically in wetlands• Natural • Artificial
11 June 2010 Water-Pollution.ppt 19
Water Quality
• Improvement since 1970– Surface waters no longer regarded as open
sewers• More and better sewage treatment systems
• Less dumping of industrial waste
– Clean Water Act of 1972, 1977 • Make all U.S. surface waters “fishable and
swimmable,”– Goal not fully met
11 June 2010 Water-Pollution.ppt 20
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