Download Water Pollution & Cleanup

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