Water Pollution & Cleanup 11 June 2010Water-Pollution.ppt1.

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)


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)


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


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)


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


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


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)


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


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


Water pollution

• Non-point and Point sources


Ground water pollution

• Pollution of aquifers• Non-point and Point sources– Pollutants slow to break down in cold & dark


Water pollution

• In lakes, reservoirs– Low flow rate, long

residence time

– Deep, stratification

– Pollutants can accumulate, concentrate


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


Water pollution

• Prevention– Better to NOT pollute than to clean up later• Clean up is expensive• Clean up is never complete


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


Sewage Treatment

• Primary– Screens and settling tanks remove grit &

suspended organic matter.


Sewage Treatment

• Secondary– Sewage aerated; aerobic bacteria consume organic matter– Leave dissolved inorganics, NO3, PO4, etc.


Sewage Treatment

• Tertiary– Filters most dissolved

inorganics and remaining dissolved organic compounds

– Can be done biologically in wetlands• Natural • Artificial


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


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Water Pollution & Cleanup 11 June 2010Water-Pollution.ppt1.

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