2Chapter Overview Questions What pollutes water, where do these pollutants come from, and what effects do they have?What are the major water pollution problems in streams and lakes?What causes groundwater pollution, and how can it be prevented?
3Chapter Overview Questions (cont’d) What are the major water pollution problems affecting coastal waters & oceans?How can we prevent and reduce surface water pollution?How safe is drinking water, and how can it be made safer?
4Case Study: Using Nature to Purify Sewage Ecological wastewater purification by a living machine.Uses the sun and a series of tanks containing plants, snails, zooplankton, crayfish, and fish (that can be eaten or sold for bait).Water can be purified with UV or O3 and consumed!John Todd, Providence, RIFigure 21-1
5WATER POLLUTION: SOURCES, TYPES, AND EFFECTS Water pollution is any chemical, biological, or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses.Point source: specific location (drain pipes, ditches, sewer lines).Nonpoint source: cannot be traced to a single site of discharge (atmospheric deposition; agricultural / industrial / residential runoff)
6WATER POLLUTION: SOURCES Point source: specific location (drain pipes, ditches, sewer lines).
7WATER POLLUTION: SOURCES Nonpoint source: cannot be traced to a single site of discharge (atmospheric deposition; agricultural / industrial / residential runoff)
8Biological Pollution: Pathogens in Water Table 21-2, p. 495
9Major Water Pollutants and Their Effects A fecal coliform bacteria test is used to indicate the likely presence of disease-causing bacteria in water.The standard for drinking water is zero fecal coliform colonies per culture!Figure 21-2
10DO: Reduced by Degradeable Wastes, Heat, and Algae Growth from Excess Inorganic Nutrients 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 4 ppm at 20°C.Next
11Dissolved Oxygen For most solutes (sugar, salt, etc): solubility increases as temperature increasesFor DO:solubility decreases as temperature increasesNext
14DO (ppm) at 20°C Water Quality Good 8–9 Slightly polluted 6.7–8 Moderatelypolluted4.5–6.7HeavilypollutedFigure 21.3Natural capital degradation: water quality and dissolved oxygen (DO) content in parts per million (ppm) at 20°C (68°F). Only a few fish species can survive in water with less than 4 ppm of dissolved oxygen at this temperature. QUESTION: Would you expect the dissolved oxygen content of polluted water to increase or decrease if the water is heated? Explain.Below 4.5GravelypollutedBelow 4Fig. 21-3, p. 496
15Water Pollution Problems in Streams Dilution and decay of degradable, oxygen-demanding wastes and heat in a stream.Next
17POLLUTION OF FRESHWATER STREAMS Flowing streams can recover from a moderate level of degradable water pollutants if they are not overloaded and their flows are not reduced.In a flowing stream, the breakdown of degradable wastes by bacteria depletes DO and creates and oxygen sag curve.This reduces or eliminates populations of organisms with high oxygen requirements.
18POLLUTION 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.80-90% of raw sewage directly discharged into rivers in developing countries (!).
19Stream Pollution in Developing Countries Water in many of central China's rivers are greenish black from uncontrolled pollution by thousands of factories.
21Case Study: India’s Ganges River: Religion, Poverty, and Health Religious beliefs, cultural traditions, poverty, and a large population interact to cause severe pollution of the Ganges River in India.Very little of the sewage is treated.Hindu believe in cremating the dead to free the soul and throwing the ashes in the holy Ganges.Some are too poor to afford the wood to fully cremate.Decomposing bodies promote disease and depletes DO.
22Case Study: India’s Ganges River: Religion, Poverty, and Health Hindu funeral pyre
23Decorated Funeral Pyre Incompletely burned bodies cause pollution.
24Case Study: India’s Ganges River: Religion, Poverty, and Health Daily, more than 1 million Hindus in India bathe, drink from, or carry out religious ceremonies in the highly polluted Ganges River.Figure 21-6
25Case Study: India’s Ganges River: Religion, Poverty, and Health
26Case Study: India’s Ganges River: Religion, Poverty, and Health
27Case Study: India’s Ganges River: Religion, Poverty, and Health
33POLLUTION 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 DO in lower layers)Low flow makes them susceptible to runoff.Various human activities can overload lakes with plant nutrients, which decrease DO and kill some aquatic species.
34Cultural 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.
35Cultural Eutrophication Cultural Eutrophication of lakes causes sudden fish kills when DO drops due toOverpopulated algae respiring at night without producing any O2 via photosynthesis and/orBacteria respiring as they decompose dead overpopulated algae
37POLLUTION OF GROUNDWATER Groundwater can become contaminated with a variety of chemicals because it cannot effectively cleanse itself and dilute and disperse pollutants.The drinking water for about half of the U.S. population and 95% of those in rural areas comes from groundwater.
38Unconfined freshwater aquifer Polluted airPesticidesand fertilizersHazardouswasteinjectionwellDeicingroad saltCoal stripmine runoffBuried gasolineand solvent tanksPumpingwellGasoline stationCesspool,septic tankWaterpumping wellWaste lagoonSewerLandfillLeakagefromfaultycasingAccidentalspillsFigure 21.7Natural capital degradation: principal sources of groundwater contamination in the United States. Another source is saltwater intrusion from excessive groundwater withdrawal (Figure 14-12, p. 315) (Figure is not drawn to scale.)DischargeUnconfined freshwater aquiferConfinedaquiferConfined freshwater aquiferGroundwaterflowFig. 21-7, p. 501
39POLLUTION OF GROUNDWATER One way to think about waste: degradabilityDegradable wastes (urine & fecal matter, dead leaves, food waste)Nondegradable wastes (lead, mercury, arsenic, flouride) are there permanently.Slowly degradable wastes (such as DDT and PCBs) are there for decades.It can take hundreds to thousands of years for contaminated groundwater to cleanse itself of degradable wastes.
40Contaminant plume moves with the groundwater LeakingtankAquiferWatertableBedrockFigure 21.8Natural capital degradation: groundwater contamination from a leaking gasoline tank. As the contaminated water spreads from its source in a widening plume, it can be extracted by wells used to provide water for drinking and irrigation.GroundwaterflowFree gasolinedissolves ingroundwater(dissolvedphase)Gasolineleakage plume(liquid phase)Migratingvapor phaseWater wellContaminant plume moveswith the groundwaterFig. 21-8, p. 502
41POLLUTION OF GROUNDWATER Over the 21st century, scientists expect to find many millions of leaking underground storage tanks to become a major global health problem.
42POLLUTION OF GROUNDWATER Leaks from a number of sources have contaminated groundwater in parts of the world.According the the EPA, one or more organic chemicals contaminate about 45% of municipal groundwater supplies.By 2003, the EPA had completed the cleanup of 297,000 of 436,000 underground tanks leaking gasoline, diesel fuel, home heating oil, or toxic solvents.
43Case 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 times the 10 ppb standard.Mostly in Bangladesh, China, and West Bengal, India.
44Groundwater Pollution SolutionsGroundwater PollutionPreventionCleanupFind substitutes for toxic chemicalsPump to surface, clean, and returnto aquifer (very expensive)Keep toxic chemicals out of the environmentInject microorganismsto clean up contamination (less expensive but still costly)Install monitoring wells near landfills and underground tanksRequire leak detectors on underground tanksFigure 21.9Solutions: methods for preventing and cleaning up contamination of groundwater. QUESTION: Which two of these solutions do you think are the most important?Pumpnanoparticles of inorganic compounds to remove pollutants (may be the cheapest, easiest, and most effective method but is still being developed)Ban hazardous waste disposalin landfills and injection wellsStore harmful liquids in aboveground tanks with leak detection and collection systemsFig. 21-9, p. 504
45OCEAN POLLUTIONThe abyssal/benthic zones of open oceans, if they are not overloaded, can disperse and break down large quantities of degradable pollutants.
46OCEAN POLLUTIONBut pollution of coastal waters near heavily populated areas is a serious problem.About 40% of the world’s population lives within 160 miles of the coast.The EPA has classified 4 of 5 estuaries as threatened or impaired.
47and heavy metals in effluents flow into bays and estuaries. CITIES INDUSTRYNitrogen oxidesfrom autos andsmokestacks,toxic chemicals,and heavy metals in effluents flow into bays and estuaries.CITIESToxic metals and oil from streets and parking lots pollute waters;URBAN SPRAWLBacteria and viruses fromsewers and septic tanks contaminate shellfish bedsCONSTRUCTION SITESSediments are washed intowaterways, choking fish and plants, clouding waters, and blocking sunlight.FARMSRunoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus.RED TIDESExcess nitrogen causesexplosive growth oftoxicmicroscopic algae,poisoning fish andmarine mammals.Closedshellfish bedsClosedbeachOxygen-depletedzoneFigure 21.10Natural capital degradation: residential areas, factories, and farms all contribute to the pollution of coastal waters and bays. According to the UN Environment Programme, coastal water pollution costs the world $16 billion annually—$731,000 a minute—due to ill health and premature death.TOXIC SEDIMENTSChemicals and toxic metals contaminate shellfish beds, kill spawning fish, andaccumulate in the tissues of bottom feeders.O2 DEPLETION ZONESedimentation and algaeovergrowth reduce sunlight,kill beneficial sea grasses, useup oxygen, and degrade habitat.HEALTHY ZONESClear, oxygen-richwaters promote growthof plankton and sea grasses,and support fish.Fig , p. 505
48OCEAN POLLUTIONHarmful algal blooms (HAB) are caused by explosive growth of harmful algae from sewage and agricultural runoff.Figure 21-11
50Oxygen Depletion in the Northern Gulf of Mexico A large zone of oxygen-depleted water (“dead zone”) forms for half of the year in the Gulf of Mexico as a result of HAB.Next
51Missouri River Mississippi River Basin Ohio River Mississippi River MS Figure 21.ANatural capital degradation: a large zone of oxygen-depleted water (less than 2 ppm dissolved oxygen) forms for half of the year in the Gulf of Mexico as a result of oxygen-depleting algal blooms. Evidence indicates that it is created mostly by huge inputs of nitrate (NO3−) and phosphate (PO43−) ions from farms, cities, and factories in the vast Mississippi River basin. The satellite image (bottom left) shows the inputs of such nutrients into the Gulf of Mexico during the summer of In the image, reds and greens represent high concentrations of phytoplankton and river sediment. This problem is worsened by loss of wetlands, which help filter plant nutrients. (NASA)LALOUISIANAMississippi RiverTXDepleted oxygenGulf of MexicoGulf of MexicoFig. 21-A, p. 507
53Case 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 21-12
54OCEAN OIL POLLUTIONMost 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 years for marine life to recover.
55OCEAN OIL POLLUTIONTanker accidents and blowouts at offshore drilling rigs can be extremely devastating to marine life (especially diving birds, left).Figure 21-13
56Exxon Valdez oil spill: OCEAN OIL POLLUTIONExxon Valdez oil spill:March 24, 1989Prince William Sound, AlaskaSingle-wall oil tanker runs aground10.8 million gallons of crude oil spilledCaptain was drunkOne of the worst single environmental disasters in US history
59Exxon ValdezIn 1994, a jury awarded plaintiffs $287 million in compensatory damages and $5 billion in punitive damages.Exxon appealed and the Ninth Circuit court reduced the punitive damages to $2.5 billion. Exxon then appealed the punitive damages to the Supreme Court which capped the damages to $507.5 million in June, 2008.On August 27, 2008, Exxon Mobil agreed to pay 75% of the $507.5 million damages ruling to settle the 1989 Exxon Valdez oil spill off AlaskaIn June 2009, a federal ruling ordered Exxon to pay an additional $480 million in interest on their delayed punitive damage awards
60Most ocean oil pollution comes from human activities on land. But Remember…Most ocean oil pollution comes from human activities on land.Oceanic oil pollution has been considered a low-risk environmental problem…Until April of 2010…
62BP’s Deepwater Horizon Oil Spill April 20, 2010, explosion of Deepwater Horizon11 killed, 17 others injuredJuly 15, 2010, the leak was partially capped4.9 million barrels (780,000 m3) of crude oil released = million gallons of crude (almost 30x the Exxon Valdez)On September 19, 2010, the relief well process was successfully completed
67Coastal Water Pollution SolutionsCoastal Water PollutionPREVENTIONCLEANUPReduce input of toxic pollutantsImprove oil-spill cleanupcapabilitiesSeparate sewage and storm linesBan dumping of wastes and sewage by maritime and cruise ships in coastal watersSprinkle nanoparticles over an oil or sewage spill to dissolve the oil or sewage withoutcreating harmful by-products(still under development)Ban ocean dumping of sludge and hazardous dredged materialProtect sensitive areas from development, oil drilling, andoil shippingFigure 21.14Solutions: methods for preventing and cleaning up excessive pollution of coastal waters. QUESTION: Which two of these solutions do you think are the most important?Require at least secondarytreatment of coastal sewageRegulate coastal developmentUse wetlands, solar-aquatic,or other methods to treat sewageRecycle used oilRequire double hulls for oil tankersFig , p. 509
68USA: Successful on Point Sources, Working on Non-point Sources The key to reducing nonpoint pollution – most of it from agriculture – is to prevent it from reaching bodies of water. Farmers can reduce runoff byPlanting buffersUsing low-till & no-till techniquesKeeping cropland covered with vegetationUsing no fertilizer on steep landLocate feedlots well away from water
69PREVENTING 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 (1972) sets standards for allowed levels of key water pollutants and requires polluters to get permits.EPA is experimenting with a discharge trading policy similar to “cap & trade” for air pollution control.
70Reducing Water Pollution through Sewage Treatment Septic tanks and various levels of sewage treatment can reduce point-source water pollution.Figure 21-15
71Manhole cover (for cleanout) Septic tank Gas Distribution box Scum WastewaterSludgeDrain field(gravel orcrushed stone)Figure 21.15Solutions: septic tank system used for disposal of domestic sewage and wastewater in rural and suburban areas.Vent pipePerforated pipeFig , p. 510
72Reducing Water Pollution through Sewage Treatment Primary and Secondary sewage treatment.Figure 21-16
73Physical Processes Biological Processes Primary Treatment Secondary TreatmentChlorinedisinfection tankBar screenGrit chamberSettling tankAeration tankSettling tankTo river, lake,or oceanSludgeRaw sewagefrom sewersActivated sludge(kills bacteria)Air pumpSludge digesterFigure 21.16Solutions: primary and secondary sewage treatment.Disposed ofin landfill or ocean or applied to cropland,pasture, or rangelandSludge drying bedFig , p. 511
74Reducing 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 (sludge!)Secondary sewage treatment: a biological process in which aerobic bacteria remove as much as 90% of dissolved and biodegradable, oxygen demanding organic wastes.
75Reducing Water Pollution through Sewage Treatment Advanced or tertiary sewage treatment:Uses series of chemical and physical processes to remove specific pollutants left over (especially nitrates and phosphates).Water is chlorinated to remove coloration and to kill disease-carrying bacteria and some viruses (disinfect).Ozone or UV light may also be used to sanitize sewage treatment effluent
76Reducing 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/or toxic chemicals.Preventing toxic chemicals from reaching sewage treatment plants would eliminate such chemicals from the sludge and water discharged from such plants.
77Odors may cause illness or indicate presence of harmful gases. Dust ParticlesParticles of dried sludge carry viruses and harmful bacteria that can be inhaled, infect cuts or enter homes.BUFFERZONEExposureChildren may walk orplay in fertilized fields.Livestock PoisoningCows may die after grazingon sludge-treated fields.SludgeGroundwaterContaminationHarmful chemicalsand pathogens may leach into groundwaterand shallow wells.Surface RunoffHarmful chemicalsand pathogens maypollute nearbystreams,lakes, ponds,and wetlands.Figure 21.17Natural capital degradation: some potential problems with using sludge from sewage treatment plants as a fertilizer on croplands. The EPA says that sludge is safe to use if applied following its guidelines. Scientists and people who have gotten sick from exposure to sludge fertilizer claim that the guidelines are inadequate and not well enforced.Fig , p. 513
78Humboldt County, California decided to treat wastewater as a resource rather than a problem, and built the Arcata Marsh and Wildlife Sanctuary. The marsh relies on natural systems to filter the city’s sewage.
79Reducing 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.
80Reducing Water Pollution through Sewage Treatment Water pollution laws have significantly improved water quality in many U.S. streams and lakes but there is a long way to go.Some want to strengthen the U.S. Clean Water Act (CWA) to prevent rather than focusing on end-of-the-pipe removal.Many farmers and developers see the CWA as limiting their rights as property owners to fill in wetlands.
81DRINKING WATER QUALITY Centralized water treatment plants and…watershed protection can provide safe drinking water for city dwellers in developed countries.
82Watering the Big Apple (NYC) 90% of NYC water comes from the Catskill Mountains in upstate New York
84Water for NYC1997- NYC faced a $6 billion upgrade to build water purification facilitiesInstead, NYC negotiated a $1.5 billion, 10 yr agreement with towns, farmers, & NY state to protect & restore forests, wetlands, & streams in the Catskills watershed.Savings realized by relying on natural purification: $4.5 billion, PLUS $300 million per year saved in filtration costs
85DRINKING WATER QUALITY Simpler and cheaper ways can be used to purify drinking water for developing countries.Exposing water to heat and the sun’s UV rays in a plastic bottle for 3 hours can kill infectious microbes.30%-40% reduction in dangerous childhood diarrhea.“Lifestraws”Inexpensive UV exposure facilities (per FLOW video)In the works: handheld carbon nanotube filters
87LifeStraw Personal filters a minimum of 700 litres of water, enough for one person for one year. LifeStraw Family filters a minimum of 18,000 litres of water, providing safe drinking water for a family for more than two years.It removes % of waterborne bacteria, 99.99% of viruses, and 99.9% of parasites.
88Using Laws to Protect Drinking Water While most developed countries have drinking water quality standards and laws, most developing countries do not.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.
89Using Laws to Protect Drinking Water The U.N. estimates that 5.6 million Americans drink water that does not meet EPA standards.1 in 5 Americans drinks water from a treatment plant that violated one or more safety standard.Industry pressures to weaken the Safe Drinking Act:Eliminate national tests and public notification of violations.Allow rights to pollute if provider cannot afford to comply.
90Is Bottled Water the Answer? Some bottled water is often not as pure as tap water and costs much more.40% of bottled water is contaminated with bacteria and/or fungi1.4 million metric tons of plastic bottles are thrown away per year.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.
91• Prevent groundwater contamination SolutionsWater Pollution• Prevent groundwater contamination• Reduce nonpoint runoff• Reuse treated wastewater for irrigation (“purple pipe”)• Find substitutes for toxic pollutants• Work with nature to treat sewage• Practice 5 R's of resource use (refuse,reduce, recycle, reuse, repurpose)Figure 21.18Solutions: methods for preventing and reducing water pollution. QUESTION: Which two of these solutions do you think are the most important?• Reduce air pollution• Reduce poverty• Reduce birth ratesFig , p. 517
92• Minimize your use of pesticides. 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 or stainless steel bottles with tap water.Figure 21.19Individuals matter: ways to help reduce water pollution. QUESTION: Which three of these actions do you think are the most important?• 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.Fig , p. 517