Chapter 20 -- Water Pollution After studying this chapter, you should be able to:       

define water pollution and describe the sources and effects of some major types. appreciate why access to sewage treatment and clean water are important to people in developing countries. discuss the status of water quality in developed and developing countries. delve into groundwater problems and suggest ways to protect this precious resource. fathom the causes and consequences of ocean pollution. weigh the advantages and disadvantages of different human waste disposal techniques. judge the impact of water pollution legislation and differentiate between best available and best practical technology, and total maximum daily pollution loads.

What is Water Pollution?   

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Any physical, biological, or chemical change in water quality that adversely affects living organisms or makes water unsuitable for desired uses can be considered pollution. There are natural sources of water contamination (e.g. poison springs and oil seeps). Pollution control standards and regulations usually distinguish between point and nonpoint pollution sources. o Point sources: discharge pollution from specific locations (e.g. drain pipes, ditches, or sewer outfalls). o Nonpoint sources: pollution is scattered or diffuse, having no specific location where they discharge into a particular body of water (e.g. runoff from farm fields and feedlots, golf courses, lawns, and gardens). The ultimate in diffuse, nonpoint pollution is atmospheric deposition of contaminants carried by air currents and precipitated into watersheds or directly onto surface waters as rain, snow, or dry particles.

Types and Effects of Water Pollution

Infectious Agents   

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The most serious water pollutants in terms of human health worldwide are pathogenic organisms. The main source of these pathogens is from untreated or improperly treated human wastes. In developed countries, sewage treatment plants and other pollution-control techniques have reduced or eliminated most of the worst sources of pathogens in inland surface waters. The situation is quite different in less-developed countries. The United Nations estimates that at least 2.5 billion people in these countries lack adequate sanitation, and that about half these people also lack access to clean drinking water. Water quality control personnel usually analyze water for the presence of coliform bacteria, any of the types that live in the colon or the intestines of humans and other animals (e.g. E. coli) Table 20.1 -- Major categories of water pollutants Category

Examples

Sources

A. Causes health problems 1. Infectious agents

Bacteria, viruses, parasites

Human and animal excreta

2. Organic chemicals

Pesticides, plastics, detergents, oil, and gasoline

Industrial, household, and farm use

3. Inorganic chemicals

Acids, caustics, salts, metals

Industrial effluents, household cleansers, surface runoff.

4. Radioactive materials

Uranium, thorium, cesium, iodine, radon

Mining and processing of ores, power plants, weapons production, natural sources

B. Causes ecosystem disruption 1. Sediment

Soil, silt

Land erosion

2. Plant nutrients

Nitrates, phosphates, ammonium

Agricultural and urban fertilizers, sewage, manure

3. Oxygendemanding wastes

Animal manure and plant residues

Sewage, agricultural runoff, paper mills, food processing

4. Thermal

Heat

Power plants, industrial cooling

Oxygen-Demanding Wastes  

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The amount of oxygen dissolved in water is a good indicator of water quality and of the kinds of life it will support. The addition of certain organic materials, such as sewage, paper pulp, or food-processing wastes, to water stimulates oxygen consumption by decomposers. Biochemical oxygen demand (BOD): a standard test of the amount of dissolved oxygen consumed by aquatic microorganisms over a five-day period. Dissolved oxygen content (DO): measure dissolved oxygen content directly using an oxygen electrode. The oxygen decline downstream from point source is called the oxygen sag. Immediately below the source of pollution, oxygen levels begin to fall as decomposers metabolize waste materials.

Plant Nutrients and Cultural Eutrophication 

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Water clarity is affected by sediments, chemicals, and the abundance of plankton organisms, and is a useful measure of water quality and water pollution. o Oligotrophic: describes rivers and lakes that have clear water and low biological productivity. o Eutrophic: describes waters that are rich in organisms and organic materials. Human activities can greatly accelerate eutrophication (cultural eutrophication). High biological productivity of eutrophic systems is often seen in "blooms" of algae or thick growth of aquatic plants stimulated by elevated phosphorous or nitrogen levels. Eutrophication also occurs in marine ecosystems, especially in near-shore waters and partially enclosed bays or estuaries.

Toxic Tides

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Red tide: bloom of deadly aquatic microorganisms called dinoflagellates. Red tides - and other colors, depending on the species involved-have become increasingly common in slow-moving rivers, brackish lagoons, estuaries, and bays. One of the most feared of these organisms is Pfiesteria piscicida, an extraordinarily poisonous dinoflagellate that has recently wiped out hundreds of thousands to millions of fish every year in polluted rivers and estuaries such as North Carolina's Palmico Sound. Under the right conditions, a population explosion can produce a dense bloom of these cells.

Inorganic Pollutants   

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Some toxic inorganic chemicals are released from rocks by weathering, are carried by runoff into lakes or rivers, or percolate into groundwater aquifers. Humans can accelerate the rate of release of these inorganic chemicals through the mining, processing, using, and discarding of minerals. Metals o Many metals such as mercury, lead, cadmium, and nickel are highly toxic. o A famous case of mercury poisoning occurred in Japan in the 1950s. o Heavy metals released as a result of human activities also are concentrated by hydrological and biological processes so that they become hazardous to both natural ecosystems and human health. o Mine drainage and leaching of mining wastes are serious sources of metal pollution in water. Nonmetallic salts o Desert soils often contain high concentrations of soluble salts, including toxic selenium and arsenic. o Salts such as sodium chloride that are nontoxic at low concentrations also can be mobilized by irrigation and concentrated by evaporation, reaching levels that are toxic for plants and animals. Acids and bases o Acids are released as by-products of industrial processes (e.g. leather tanning, metal smelting and planting) o Coal and oil combustion also leads to formation of atmospheric sulfuric and nitric acids, which are disseminated by long-range transport processes.

Organic Chemicals   

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Many chemicals used in the chemical industry to make pesticides, plastics, pharmaceuticals, pigments, and other products we use in everyday life are highly toxic. The two most important sources of toxic organic chemicals in water are improper disposal of industrial and household wastes and runoff of pesticides. Many of the toxic organic chemicals (e.g. DDT, Dioxins, and other chlorinated hydrocarbons) in water are passed through ecosystems and accumulated at high levels in certain nontarget organisms. Hundreds of millions of toxic hazardous organic wastes are thought to be stored in dumps, landfills, lagoons, and underground tanks in the United States.

Sediment

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Rivers have always carried sediment to the oceans, but erosion rates in many areas have been greatly accelerated by human activities. Sources of erosion include forests, grazing lands, and urban construction sites. Sediment fills lakes and reservoirs, obstructs shipping channels, clogs hydroelectric turbines, and makes purification of drinking water more costly. Excess sediment deposits can fill estuaries and smother aquatic life on coral reefs and shoals near shore. Sediment can also be beneficial. Mud carried by rivers nourishes floodplain farm fields.

Thermal Pollution and Thermal Shocks   

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Raising or lowering water temperatures from normal levels can adversely affect water quality and aquatic life. Humans cause thermal pollution by altering vegetation cover and runoff patterns, as well as by discharging heated water directly into rivers and lakes. The cheapest way to remove heat from an industrial facility is to draw cool water from an ocean, river, lake, or aquifer, run it through a heat-exchanger to extract excess heat, and dump the heated water back into the original source. In some circumstances, introducing heated water into a water body is beneficial. o Warming catfish-rearing ponds o Attract fish, birds, and marine mammals that find food and refuge there, especially during cold weather.

Water Quality Today

Surface Waters in the United States and Canada

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The United States and Canada have made encouraging progress in protecting and restoring water quality in rivers and lakes over the past 40 years. Areas of Progress o The 1972 Clean Water Act established a National Pollution Discharge Elimination System (NPDES), which requires an easily revoked permit for any industry, municipality or other entity dumping wastes in surface waters. o Since the Clean Water Act was passed, much of the effort has been aimed at point sources, especially to build or upgrade thousands of municipal sewage treatment plants. As a result, nearly everyone in urban areas is now served by municipal sewage systems and no major city discharges raw sewage into a river or lake except as overflow during rainstorms. o Campaign has led to significant improvements in surface water quality in many places. o In 1999, the EPA reported that 91.4 percent of all monitored river miles and 87.5 percent of all assessed lake acres are suitable for their designated uses. In 1998, a new regulatory approach to water quality assurance was instituted by the EPA. Rather than issue standards on a river by river approach or factory by factory permit discharge, the focus is being changed to watershed-level monitoring and protection.

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Remaining Problems o Nonpoint discharges of pollutants are the greatest impediments to achieving national goals of water quality. o About three-fourths of the water pollution in the United States comes from soil erosion, fallout of air pollutants, and surface runoff from urban areas, farm fields, and feedlots. o Loading of both nitrates and phosphates in surface water have decreased from point sources but have increased about four-fold since 1972 from nonpoint sources. o Fossil fuel combustion has become a major source of nitrates, sulfates, arsenic, cadmium, mercury, and other toxic pollutants.

Surface Waters in Other Countries   

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Japan, Australia, and most of Western Europe also have improved surface water quality in recent years. Sewage treatment in the wealthier countries of Europe generally equals or surpasses that in the United States. The fall of the "iron curtain" in 1989 revealed appalling environmental conditions in much of the former Soviet Union and it's satellite states in eastern and central Europe.

The countries closest geographically and socially to western Europe, the Czech Republic, Hungry, East Germany, and Poland have made massive investments and encouraging progress towards cleaning environmental problems. There are some encouraging pollution control stories (e.g. Minimata Bay in Japan and the Rhine river). The less-developed countries of South America, Africa, and Asia have even worse water quality than do the poorer countries of Europe. o Sewage treatment is either totally lacking or woefully inadequate. o In urban areas 95 percent of all sewage is discharged untreated into rivers, lakes, or the ocean. o Low technological capabilities and little money for pollution control are made even worse by burgeoning populations, rapid urbanization, and the shift of much heavy industry from developed countries.

Groundwater and Drinking Water Supplies    

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About half the people in the United States, including 95 percent of those in rural areas, depend on underground aquifers for their drinking water. This vital resource is threatened in many areas by overuse and pollution and by a wide variety of industrial, agricultural, and domestic contaminants. The U.S. EPA estimates that every day some 4.5 trillion liters of contaminated water seep into the ground in the United States from a variety of sources. Deep underground aquifers often have residence times of thousands of years and many contaminants are extremely stable once underground; therefore, for very large aquifers, pollution may be essentially irreversible. In farm country, especially in the Midwest's Corn Belt, fertilizers and pesticides commonly contaminate aquifers and wells. A great deal of soil in American cities remains contaminated by previous careless storage and disposal of petroleum products. In addition to groundwater pollution problems, contaminated surface waters and inadequate treatment make drinking water unsafe in many areas. Every year epidemiologists estimate that around 1.5 million Americans fall ill from infections caused by fecal contamination.

Ocean Pollution 

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Near-shore zones around the world, especially bays, estuaries, shoals, and reefs near large cities or the mouths of major rivers often are overwhelmed by human-caused contamination. Poisonous blooms of algae regularly deplete ocean waters of oxygen and kill enormous numbers of fish and other marine life. Discarded plastic flotsam and jetsam are becoming an ubiquitous mark of human impact on the oceans. Few coastlines in the world remain uncontaminated by oil or oil products. Oceanographers estimate that somewhere between 3 million and 6 million metric tons of oil are discharged into the world's oceans each year from both land- and sea-based operations. The transport of huge quantities of oil creates opportunities for major pollution episodes through a combination of human and natural hazards.

Water Pollution Control Source Reduction   

The cheapest and most effective way to reduce pollution is to avoid producing it or releasing it to the environment in the first place. Industry can modify manufacturing processes so fewer wastes are created. Recycling or reclaiming materials that otherwise might be discarded in the waste stream also reduces pollution.

Nonpoint Sources and Land Management  

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Among the greatest remaining challenges in water pollution control are diffuse, nonpoint pollution sources. Nonpoint sources have many origins and numerous routes by which contaminants enter ground and surface waters; therefore, it is difficult to identify, monitor, and control all these sources and routes. Some main causes of nonpoint pollution include agriculture, urban runoff, construction sites, and land disposal. Generally soil conservation methods also help protect water quality. In urban areas, reducing materials carried away by storm runoff is helpful. A good example of watershed management is seen in the Chesapeake Bay, America's largest estuary. o Principal objectives of this plan include reducing nutrient loading, pollution prevention measures, replanting thousands of hectares of seagrasses, and restoring wetlands that filter out pollutants. o Although progress has been made, the goals of reducing both nitrogen and phosphate levels by 40 percent and restoring viable fish and shellfish populations are still decades away.

Human Waste Disposal  

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Human and animal wastes usually create the most serious health-related water pollution problems. Natural Processes o In poorer countries of the world, most rural people simply go out into the fields and forests to relieve themselves as they have always done. o When population densities are low, natural processes eliminate wastes quickly. o Where intensive agriculture is practiced, it has long been customary to collect human and animal waste to be spread on the fields as fertilizer and become a source of disease-causing pathogens in the food supply. o Until about fifty years ago, most rural American families and quite a few residents of towns and small cities depended on a pit toilet or "outhouse" for waste disposal from which the untreated wastes would seep into the ground.  The development of septic tanks and properly constructed drain fields represented a considerable improvement in public health. Municipal Sewage Treatment o Over the past 100 years, sanitary engineers have developed effective municipal wastewater treatment systems to protect human health, ecosystem stability, and water quality. o How does a typical municipal sewage treatment facility work?

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Primary treatment is the first step in municipal waste treatment that physically separates large solids from the waste stream.  Secondary treatment consists of biological degradation of the dissolved organic compounds.  Tertiary treatment removes plant nutrients, especially nitrates and phosphates, from the secondary effluent. o In many American cities, sanitary sewers are connected to storm sewers, which carry runoff from streets and parking lots which generally contain a variety of refuse, fertilizers, pesticides, oils, rubber, tars, lead, and other undesirable chemicals. Low-Cost Waste Treatment o The municipal sewage systems used in developed countries are often too expensive to build and operate in the developing world where low-cost, low-tech alternatives for treating wastes are needed. o One option is effluent sewerage, a hybrid between a traditional septic tank and a full sewer system. o Another alternative is to use natural or artificial wetlands to dispose of wastes. o Wetland waste treatment systems are now operating in many developing countries.  Effluent from these operations can be used to irrigate crops or raise fish for human consumption if care is taken to first destroy pathogens.

Water Remediation  

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New developments in environmental engineering are providing promising solutions to many water pollution problems. Containment methods confine or restrain dirty water or liquid wastes in situ (in place) or cap the surface with an impermeable layer to divert surface water or groundwater away from the site and to prevent further pollution. Where pollutants are buried too deeply to be contained mechanically, materials sometimes can be injected to precipitate, immobilize, chelate, or solidify them. Extraction techniques pump out polluted water so it can be treated. Bioremediation: the use of living organisms can be used effectively and inexpensively to clean contaminated water (e.g. wetlands and reaction vessels containing organisms).

Water Legislation Table 20.2 -- Some important U.S. water quality legislation 1. Federal Water Pollution Control Act (1972). Established uniform nationwide controls for each category of major polluting industries. 2. Marine Protection Research and Sanctuaries Act (1972). Regulates ocean dumping and established sanctuaries for protection of endangered marine species. 3. Ports and Waterways Safety Act (1972). Regulates oil transport and the operation of oil handling facilities. 4. Safe Drinking Water Act (1974). Requires minimum safety standards for every community water supply. Among the contaminants regulated are bacteria, nitrates, arsenic, barium, cadmium, chromium, fluoride, lead, mercury, silver, pesticides; radioactivity and turbidity also regulated. This act also contains provisions to protect groundwater aquifers. 5. Resource Conservation and Recovery Act (RCRA)(1976). Regulates the storage, shipping, processing, and disposal of hazardous wastes and sets limits on the sewering of

toxic chemicals. 6. Toxic Substances Control Act (TOSCA) (1976). Categorizes toxic and hazardous substances, establishes a research program, and regulates the use and disposal of poisonous chemicals. 7. Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) (1980) and Superfund Amendments and Reauthorization Act (SARA) (1984). Provide for sealing, excavation, or remediation of toxic and hazardous waste dumps. 8. Clean Water Act (1985) (amending the 1972 Water Pollution Control Act). Sets as a national goal the attainment of "fishable and swimmable" quality for all surface waters in the United States. 9. London Dumping Convention (1990). Calls for an end to all ocean dumping of industrial wastes, tank washing effluents, and plastic trash. The United States is a signatory to this international convention.

The Clean Water Act 

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Passage of the Clean Water Act of 1972 was a bold, bipartisan step determined to "restore and maintain the chemical, physical, and biological integrity of the Nation's waters" that made clean water a national priority. For specific "point" sources of pollution, the act requires discharge permits and best practicable control technology (BPT). Sets national goals of best available, economically achievable technology (BAT), for toxic substances and zero discharge for 126 priority toxic pollutants. While not yet swimmable or fishable everywhere, surface water quality in the United States has significantly improved on average over the past quarter century. Not everyone is completely happy with the Clean Water Act. o Industries, state and local governments, farmers, land developers, and others who have been forced to change their operations or spend money on water protection feel imposed upon.

Clean Water Act Reauthorization   

Opponents of federal regulation have tried repeatedly to weaken or eliminate the Clean Water Act. Those who support the Act in principle would like to see it changed and strengthened. Environmentalists also would like to see stricter enforcement of existing regulations, mandatory minimum penalties for violations, more effective community right-to-know provisions, and increased powers for citizen lawsuits against polluters.

Other Important Water Legislation 

In addition to the Clean Water Act, several other laws help to regulate water quality in the United States and abroad. o Safe Drinking Water Act. o "Superfund Program" -- Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) as amended by the Superfund Amendments and Reauthorization Act (SARA).

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Great Lakes Water Quality Agreement (U.S. and Canada)

Summary            

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Any physical, biological, or chemical change in water quality that adversely affects living organisms or makes water unsuitable for desired uses can be considered pollution. Worldwide, the most serious water pollutants, in terms of human health, are pathogenic organisms from human and animal wastes. In industrialized nations, toxic chemical wastes have become an increasing problem. Agricultural and industrial chemicals have been released or spilled into surface waters and are seeping into groundwater supplies. Major causes of ocean pollution are oil spills from tanker bilge pumping or accidents and oil well blowouts. Surface runoff and sewage outfalls discharge fertilizers, pesticides, organic nutrients, and toxic chemicals that have a variety of deleterious effects on marine ecosystems. The major water pollutants in terms of quantity are silt and sediments. Addition of salts and metals from highway and farm runoff and industrial activities also damage water quality. In some areas, drainage from mines and tailings piles deliver sediment and toxic materials to rivers and lakes. Water pollution is a major source of human health problems. Appropriate land-use practices and careful disposal of industrial, domestic, and agricultural wastes are essential for control of water pollution. Natural processes and living organisms have a high capacity to remove or destroy water pollutants, but these systems become overloaded and ineffective when pollution levels are too high. Municipal sewage treatment is effective in removing organic material from wastewater, but the sewage sludge is often contaminated with metals and other toxic industrial materials.

Questions for Review 1. Define water pollution. 2. List eight major categories of water pollutants and give an example for each category. 3. Describe eight major sources of water pollution in the United States. What pollution problems are associated with each source? 4. What is Pfiesteria and why is it dangerous? 5. What is eutrophication? What causes it? 6. What are the origins and effects of siltation? 7. Describe primary, secondary, and tertiary processes for sewage treatment. What is the quality of the effluent from each of these processes? 8. Why do combined storm and sanitary sewers cause water quality problems? Why does separating them also cause problems? 9. What pollutants are regulated by the Clean Water Act? What goals does this act set for abatement technology? 10. Describe remediation techniques and how they work.

Questions for Critical Thinking 1. How precise is the estimate that 2 billion people lack access to clean water? Would it make a difference if the estimate is off by 10 percent or 50 percent? 2. How would you define adequate sanitation? Think of some situations in which people might have different definitions for this term. 3. Do you think that water pollution is worse now than it was in the past? What considerations go into a judgment like this? How do your personal experiences influence your opinion? 4. What additional information would you need to make a judgment about whether conditions are getting better or worse? How would you weigh different sources, types, and effects of water pollution? 5. Imagine yourself in a developing country with a severe shortage of clean water. What would you miss most if your water supply were suddenly cut by 90 percent? 6. Why has EPA changed to total maximum daily pollution loads and watershed management? What are the major implications of this change? 7. Proponents of deep well injection of hazardous wastes argue that it will probably never be economically feasible to pump water out of aquifers more than 1 kilometer below the surface. Therefore, they say, we might as well use those aquifers for hazardous waste storage. Do you agree? Why or why not? 8. Under what conditions might sediment in water or cultural eutrophication be beneficial? How should we balance positive and negative effects? 9. Suppose that part of the silt in a river is natural and part is human-caused. Is one pollution but the other not? 10. Suppose that you own a lake but it is very polluted. An engineer offers options for various levels of cleanup. As you increase water quality, you also increase costs greatly. How clean would you want the water to be--fishable, swimmable, drinkable--and how much would you be willing to pay to achieve your goal? Make up your own numbers. The point is to examine your priorities and values.