Core Case Study: Using Nature to Purify Sewage
• Ecological wastewater purification by a living machine.
Figure 21-1Figure 21-1
Table 21-2, p. 495
Major Water Pollutants and Their Effects
• A fecal coliform bacteria test is used to indicate the likely presence of disease-causing bacteria in water.
Figure 21-2Figure 21-2
Major Water Pollutants and Their Effects
• Water quality and dissolved oxygen (DO) content in parts per million (ppm) at 20°C.– Only a few fish species can survive in water
less than 4ppm at 20°C.Figure 21-3Figure 21-3
Water Pollution Problems in Streams
• Dilution and decay of degradable, oxygen-demanding wastes and heat in a stream.
Figure 21-4Figure 21-4
Fig. 21-4, p. 497
8 ppm
Biologicaloxygendemand
Dissolvedoxygen(ppm)
Types oforganisms
8 ppm
Recovery
ZoneSeptic ZoneDecomposition
ZoneClean Zone
Fish absent,fungi, sludgeworms,bacteria
(anaerobic)
Trash fish(carp, gar,leeches)
Clean Normal clean
water organisms
(Trout, perch, bass,
mayfly, stonefly)
Normal clean water
organisms
(Trout, perch, bass,
mayfly, stonefly)
Clean Zone
Trash fish(carp, gar,leeches)
Oxygen Sag Curve
POLLUTION OF FRESHWATER STREAMS
• Most developed countries have sharply reduced point-source pollution but toxic chemicals and pollution from nonpoint sources are still a problem.
• Stream pollution from discharges of untreated sewage and industrial wastes is a major problem in developing countries.
The World's Toilet Crisis: Vanguard Trailer // Current
Animation: Stream Pollution
PLAYANIMATION
POLLUTION OF FRESHWATER LAKES
• Dilution of pollutants in lakes is less effective than in most streams because most lake water is not mixed well and has little flow.– Lakes and reservoirs are often stratified and
undergo little mixing.– Low flow makes them susceptible to runoff.
• Various human activities can overload lakes with plant nutrients, which decrease DO and kill some aquatic species.
Cultural Eutrophication
• Eutrophication: the natural nutrient enrichment of a shallow lake, estuary or slow moving stream, mostly from runoff of plant nutrients from the surrounding land.
• Cultural eutrophication: human activities accelerate the input of plant nutrients (mostly nitrate- and phosphate-containing effluents) to a lake.– 85% of large lakes near major population centers
in the U.S. have some degree of cultural eutrophication.
Fig. 21-7, p. 501
Coal strip mine runoff
Polluted air
Deicing road salt
Pesticidesand fertilizers
Hazardous waste
injection well
Pumping well
Gasoline station
Water pumping well
LandfillSewer
Buried gasoline and solvent tanks
Cesspool, septic tank
Groundwater flow
Confined aquifer
Confined freshwater aquifer
Unconfined freshwater aquifer
Accidentalspills
Waste lagoonLeakage from faulty casing
Discharge
Video: MTBE Pollution
• From ABC News, Environmental Science in the Headlines, 2005 DVD.
PLAYVIDEO
POLLUTION OF GROUNDWATER
• It can take hundreds to thousand of years for contaminated groundwater to cleanse itself of degradable wastes.– Nondegradable wastes (toxic lead, arsenic,
flouride) are there permanently.– Slowly degradable wastes (such as DDT)
are there for decades.
Fig. 21-8, p. 502
Aquifer
Water well
Migrating vapor phase
Contaminant plume moveswith the groundwater
Free gasolinedissolves ingroundwater(dissolved phase)
Groundwaterflow
Watertable
Gasolineleakage plume(liquid phase)
Leakingtank
Bedrock
Case Study: Arsenic in Groundwater - a Natural Threat
• Toxic Arsenic (As) can naturally occur at high levels in soil and rocks.
• Drilling into aquifers can release As into drinking water supplies.
• According to WHO, more than 112 million people are drinking water with As levels 5-100 times the 10 ppb standard.– Mostly in Bangladesh, China, and West Bengal,
India.
Fig. 21-9, p. 504
Solutions
Groundwater Pollution
CleanupPrevention
Find substitutes for toxic chemicals
Install monitoring wells near landfills and underground tanksRequire leak detectors on underground tanks
Ban hazardous waste disposal in landfills and injection wells
Store harmful liquids in aboveground tanks with leak detection and collection systems
Pump to surface, clean, and return to aquifer (very expensive)Keep toxic
chemicals out of the environment
Inject microorganisms to clean up contamination (less expensive but still costly)
OCEAN POLLUTION
• Oceans, if they are not overloaded, can disperse and break down large quantities of degradable pollutants.
• Pollution of coastal waters near heavily populated areas is a serious problem.– About 40% of the world’s population lives
near on or near the coast.– The EPA has classified 4 of 5 estuaries as
threatened or impaired.
Fig. 21-10, p. 505
Healthy zoneClear, oxygen-richwaters promote growthof plankton and sea grasses,and support fish.
Oxygen-depleted zoneSedimentation and algaeovergrowth reduce sunlight,kill beneficial sea grasses, useup oxygen, and degrade habitat.
Red tidesExcess nitrogen causesexplosive growth of toxicmicroscopic algae,poisoning fish andmarine mammals.
FarmsRunoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus.
Toxic sedimentsChemicals and toxic metals contaminate shellfish beds, kill spawning fish, andaccumulate in the tissues of bottom feeders.
Construction sitesSediments are washed intowaterways, choking fish and plants, clouding waters, and blocking sunlight.
Urban sprawlBacteria and viruses fromsewers and septic tanks contaminate shellfish beds
Oxygen-depletedzone
Closedbeach
CitiesToxic metals and oil from streets and parking lots pollute waters;
IndustryNitrogen oxidesfrom autos andsmokestacks,toxic chemicals,and heavy metals in effluents flow into bays and estuaries.
Closedshellfish beds
OCEAN POLLUTION
• Harmful algal blooms (HAB) are caused by explosive growth of harmful algae from sewage and agricultural runoff.
Figure 21-11Figure 21-11
Video: Beach Pollution
• From ABC News, Environmental Science in the Headlines, 2005 DVD.
PLAYVIDEO
Oxygen Depletion in the Northern Gulf of Mexico
• A large zone of oxygen-depleted water forms for half of the year in the Gulf of Mexico as a result of HAB.
Figure 21-AFigure 21-A
Fig. 21-A, p. 507
Mississippi River
MississippiRiver Basin
Gulf of Mexico
Ohio River
Mississippi River
Missouri River
TX
MSLA
Depleted oxygen
LOUISIANA
Gulf of Mexico
Case Study: The Chesapeake Bay – An Estuary in Trouble
• Pollutants from six states contaminate the shallow estuary, but cooperative efforts have reduced some of the pollution inputs.
Figure 21-12Figure 21-12
OCEAN OIL POLLUTION
• Most ocean oil pollution comes from human activities on land.– Studies have shown it takes about 3 years for
many forms of marine life to recover from large amounts of crude oil (oil directly from ground).
– Recovery from exposure to refined oil (fuel oil, gasoline, etc…) can take 10-20 years for marine life to recover.
http://www.youtube.com/watch?v=_YXA2hp3D8k&feature=related
http://www.youtube.com/watch?v=AAiTywPmgD4
Booms and skimmer boats
http://www.cbsnews.com/video/watch/?id=3498979n
Oil eating bacteria!!!!!
Oil pipelines lead out to a dead forest at the Shell-owned Etelebuflow station in Etelebu, Nigeria, pictured here in March 2001
OCEAN OIL POLLUTION• Tanker accidents
and blowouts at offshore drilling rigs can be extremely devastating to marine life (especially diving birds, left).
Figure 21-13Figure 21-13
Fig. 21-14, p. 509
Reduce input of toxic pollutants
Solutions
Coastal Water Pollution
Prevention Cleanup
Use wetlands, solar-aquatic, or other methods to treat sewage
Require at least secondary treatment of coastal sewage
Improve oil-spill cleanup capabilities
Recycle used oil
Regulate coastal development
Protect sensitive areas from development, oil drilling, and oil shipping
Ban ocean dumping of sludge and hazardous dredged material
Ban dumping of wastes and sewage by maritime and cruise ships in coastal waters
Separate sewage and storm lines
Require double hulls for oil tankers
PREVENTING AND REDUCING SURFACE WATER POLLUTION
• The key to reducing nonpoint pollution – most of it from agriculture – is to prevent it from reaching bodies of water.– Farmers can reduce runoff by planting buffers
and locating feedlots away from steeply sloped land, flood zones, and surface water.
PREVENTING AND REDUCING SURFACE WATER POLLUTION
• Most developed countries use laws to set water pollution standards, but such laws rarely exist in developing countries.– The U.S. Clean Water Act sets standards for
allowed levels of key water pollutants and requires polluters to get permits.
Reducing Water Pollution through Sewage Treatment
• Septic tanks and various levels of sewage treatment can reduce point-source water pollution.
Figure 21-15Figure 21-15
Fig. 21-15, p. 510
Distribution box
Manhole cover(for cleanout)
Vent pipePerforated pipe
Drain field(gravel orcrushed stone)
Septic tank
Sludge
Wastewater
Gas
Scum
Reducing Water Pollution through Sewage Treatment
• Raw sewage reaching a municipal sewage treatment plant typically undergoes:– Primary sewage treatment: a physical process
that uses screens and a grit tank to remove large floating objects and allows settling.
– Secondary sewage treatment: a biological process in which aerobic bacteria remove as much as 90% of dissolved and biodegradable, oxygen demanding organic wastes.
Reducing Water Pollution through Sewage Treatment
• Primary and Secondary sewage treatment.Figure 21-16Figure 21-16
Fig. 21-16, p. 511
Raw sewagefrom sewers
Activated sludge
Disposed of in landfill or ocean or applied to cropland,pasture, or rangeland
Primary Secondary
Grit chamberBar screen Settling tank Aeration tank Settling tankChlorinedisinfection tank
Sludge drying bed
Sludge digester
Air pump
To river, lake,or ocean
(kills bacteria)
Sludge
Reducing Water Pollution through Sewage Treatment
• Advanced or tertiary sewage treatment:– Uses series of chemical and physical
processes to remove specific pollutants left (especially nitrates and phosphates).
• Water is chlorinated to remove coloration and to kill disease-carrying bacteria and some viruses (disinfect).
Reducing Water Pollution through Sewage Treatment
• Sewage sludge can be used as a soil conditioner but this can cause health problems if it contains infectious bacteria and toxic chemicals.
• Preventing toxic chemicals from reaching sewage treatment plants would eliminate such chemicals from the sludge and water discharged from such plants.
Fig. 21-17, p. 513
Sludge
Groundwater ContaminationHarmful chemicals and pathogens may leach into groundwater and shallow wells.
OdorsOdors may cause illness or indicate presence of harmful gases.
Livestock PoisoningCows may die after grazing on sludge-treated fields.
Dust ParticlesParticles of dried sludge carry viruses and harmful bacteria that can be inhaled, infect cuts or enter homes.
Surface RunoffHarmful chemicals and pathogens may pollute nearby streams,lakes, ponds, and wetlands.
ExposureChildren may walk or play in fertilized fields.
BUFFER ZONE
Reducing Water Pollution through Sewage Treatment
• Natural and artificial wetlands and other ecological systems can be used to treat sewage.– California created a 65 hectare wetland near
Humboldt Bay that acts as a natural wastewater treatment plant for the town of 16,000 people.
• The project cost less than half of the estimated price of a conventional treatment plant.
DRINKING WATER QUALITY
• Centralized water treatment plants and watershed protection can provide safe drinking water for city dwellers in developed countries.
• Simpler and cheaper ways can be used to purify drinking water for developing countries.– Exposing water to heat and the sun’s UV rays
for 3 hours can kill infectious microbes.
Using Laws to Protect Drinking Water
• The U.S Safe Drinking Water Act requires the EPA to establish national drinking water standards (maximum contaminant levels) for any pollutant that may have adverse effects on human health.
Is Bottled Water the Answer?
• Some bottled water is not as pure as tap water and costs much more.– 1.4 million metric tons of plastic bottles are
thrown away.– Fossil fuels are used to make plastic bottles.
• The oil used to produce plastic bottles in the U.S. each year would fuel 100,000 cars.
Fig. 21-18, p. 517
• Prevent groundwater contamination
Solutions
Water Pollution
• Reduce birth rates
• Reduce poverty
• Reduce air pollution
• Practice four R's of resource use (refuse, reduce, recycle, reuse)
• Work with nature to treat sewage
• Find substitutes for toxic pollutants
• Reuse treated wastewater for irrigation
• Reduce nonpoint runoff
Fig. 21-19, p. 517
What Can You Do?
Water Pollution
• Fertilize garden and yard plants with manure or compost instead of commercial inorganic fertilizer.
• Minimize your use of pesticides.
• Do not apply fertilizer or pesticides near a body of water.
• Grow or buy organic foods.
• Do not drink bottled water unless tests show that your tap water is contaminated. Merely refill and reuse plastic bottles with tap water.
• Compost your food wastes.
• Do not use water fresheners in toilets.
• Do not flush unwanted medicines down the toilet.
• Do not pour pesticides, paints, solvents, oil, antifreeze, or other products containing harmful chemicals down the drain or onto the ground.
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