Water Pollution: Freshwater
Freshwater pollution is the contamination of inland water (not saline) with substances that make it unfit for its natural or intended use. Pollution may be caused by fecal waste, chemicals, pesticides, petroleum, sediment, or even heated discharges. Polluted rivers and lakes are unfit for swimming or fishing; polluted water is unsafe to drink.
For centuries, fecal waste and other pollutants were dumped in rivers, with "dilution the solution" to pollution. In the mid-twentieth century, many
The damning image of a river in flames is credited by many for passage of the Federal Water Pollution Control Act of 1972. The U.S. Environmental Protection Agency (EPA) set standards to regulate the discharge of industrial and municipal waste—so-called end-of-the-pipe pollution. With them came significant federal funding to help localities improve wastewater treatment.
Improvements in municipal wastewater treatment have been matched by progress in the private sector. Nationally, more than thirty thousand major industrial dischargers pretreat their wastewater before it enters local sewers. By 2000, some 75 percent of toxic discharges, including heavy metals and PCBs, were being prevented.
Surface Water Pollution
Freshwater makes up less than three percent of earth's water, but is the source of virtually all drinking water. In 2002, each U.S. household used an average of 94,000 gallons of water per year. Some 55 percent of that water comes from reservoirs, rivers, and lakes, and a 2000 survey published in EPA's National Water Quality Inventory found almost 40 percent of U.S. rivers and 45 percent of lakes are polluted. These sources, called surface water, are vulnerable to pollution discharged out of pipes and precipitating out of the air but the primary source of their pollution today is runoff, pollutants washing off the land.
These nonpoint or scattered sources are not easily traceable. Pesticides and fertilizers used in agriculture and on golf courses and suburban lawns account for a major portion of nonpoint source pollution. Runoff from parking lots and roads flush spilled oil and gasoline and road salt into lakes and streams. Runoff containing manure from livestock and poultry producers has
Air pollutants such as dioxin and mercury along with sulfur and nitrogen oxides precipitate into lakes and rivers by rainfall in the form of acid rain. More than 95 percent of rainwater tested at four sites in Indiana between 2001 and 2002 contained unsafe levels of mercury according to a National Wildlife Federation report.
Point sources, such as chemical and municipal wastewater treatment plants, were the leading source of contamination for about ten percent of river and lake water according to the 2000 National Water Quality Inventory. Toxic chemicals, although now regulated, can still be discharged directly into surface water. AK Steel Corporation in Pennsylvania discharged the largest amount of any industrial pollutant, about 28 million pounds of nitrate compounds, to surface water between 1998 and 2000, according to the Toxic Release Inventory.
Other sources of surface water pollution include silt washed into streams and lakes that smothers organisms on the lake floor, upsetting or destroying aquatic ecosystems. Thermal pollution such as an influx of warm water from cooling towers for power ecosystems. plants also has a detrimental effect on aquatic
The recent discovery of surface-water contamination by minute amounts of pharmaceuticals and personal-care products, including synthetic hormones
Water contained in the pores of soil or in aquifers is called groundwater. About 40 percent of U.S. municipal water comes from groundwater and an additional forty million people, including most of the rural population, draw drinking water from domestic wells. Groundwater, while protected by the filtering action of soil, can be contaminated by leaking municipal landfills, sewage lagoons, and chemicals from industrial activity. Centers for Disease Control data shows that 318 waterborne disease outbreaks associated with groundwater systems occurred between 1971 and 1996. Leaking underground oil tanks and spills at gas stations account for oil and other chemicals such as benzene and methyl-tertiary-butyl ether (MBTE) found in ground-water. More than 400,000 leaking underground storage tanks were reported in the United States in 2001. Pesticides and agricultural fertilizers drain into groundwater polluting it with carcinogenic chemicals and nitrates.
The Safe Drinking Water Act of 1974 (SWDA) regulates groundwater. More than eighty possible contaminants are monitored, including carcinogens such as tetrachloroethylene, discharged from dry cleaners. Health effects of these contaminants range from increased cancer risk, intestinal lesions, kidney damage, and reproductive difficulties, to gastrointestinal distress. Municipal and private water suppliers are responsible for seeing that contaminants do not exceed the limits set by the EPA.
Human and Environmental Health Effects
Fertilizer, animal manure, and waste-treatment plant effluent all contain nutrients that stimulate excessive plant and algal growth in freshwater bodies. When the plants die and decompose, dissolved oxygen is depleted, causing die-offs of fish and other species living in the water. Persistent organochlorine insecticides, such as DDT, deposited in lake sediments can bioaccumulate, harming the fish and birds that eat them. Pyrethroid insecticides, though derived from chrysanthemums, are extremely toxic to aquatic organisms. Estrogen-mimicking substances such as some pesticides and industrially produced chemicals have been shown to interfere with the reproductive system of fish.
Human and animal fecal waste contain disease-carrying organisms such as the bacterium Escherichia coli (E. coli) and pathogens that causes cholera, typhoid, and cryptosporidiosis. Cholera is rarely seen in the United States, but E. coli outbreaks are not rare, and in 1993, more than fifty people died, and an estimated 400,000 became ill from a massive outbreak of cryptosporidiosis in Milwaukee, Wisconsin. The outbreak was attributed to a failure in drinking water treatment, allowing the cyst form of the parasite, introduced by animal waste, to pass into tap water and be ingested. Ten outbreaks of cryptosporidiosis were reported in the United States between 1990 and 2000.
Mercury bioaccumulates in fish and can damage the nervous systems and brains of humans. It can interfere with normal behavior in birds, such as loons, causing them to spend less time looking for food or incubating eggs. About one-quarter of breeding adult loons have higher-than-normal (10 parts per million) levels of mercury. To protect people from eating contaminated fish, states and local governments post fish-consumption advisories when contaminant levels become unsafe. There were 2,800 advisories posted in the United States in 2002, alerting people to high levels of mercury, PCBs, chlordane, dioxins, and DDT in fish.
Prevention and Abatement
Once water is contaminated, it is difficult, expensive, and sometimes impossible to remove pollutants. Technologies to remove contaminants from groundwater are air stripping, granular activated carbon, and advanced oxidation. Air stripping involves pumping out the contaminated water, then heating it to evaporate the contaminant. The cleaned water is reinjected into the ground. Pumping out contaminated water and absorbing the pollutant on activated charcoal can remove less volatile compounds. Ninety percent of trichloroethylene was removed from NASA's launch complex thirty-four groundwater cleanup site on Cape Canaveral Air Force Station by thermal treatment. In this method an electric current heats soil and water, evaporating some water and the contaminant, which is carried out of the ground by the force of the steam and collected in recovery wells.
Preventing pollution is obviously important. Drinking water suppliers have discovered that watershed protection is cost-effective because it reduces pollution and cuts the cost of drinking water treatment. A watershed is the area that drains into surface or groundwater and keeping that area free from development and agricultural runoff are among the goals of watershed protection. The Barnes Aquifer in Massachusetts supplies water to sixty thousand residents and the aquifer's recharge area is under heavy development pressure from large-scale residential subdivisions. Municipal wells have been contaminated with traces of ethylene dibromide and trichloroethylene. After learning about watershed protection, citizens voted against proposed changes to zoning that would have increased the number of new homes and increased the potential for groundwater pollution. And by investing $1 billion in watershed protection, New York City, with an enormous reservoir system, has avoided having to build water-filtration facilities, saving construction costs of some $8 billion.
The United Nations (UN) theme for World Environment Day 2003 was "Water: Two Billion People are Dying for It!" It was not en exaggeration. The UN reports that one person in six lives without regular access to safe drinking water. Over twice that number—2.4 billion people—lack access to adequate sanitation. Water-related diseases kill a child every eight seconds, and are responsible for 80 percent of all illnesses and deaths in the developing world. Cholera outbreaks, due to water contaminated with raw sewage, occur regularly in India and Bangladesh and less frequently in many other countries. In Africa in 1997, 5,853 deaths due to cholera were reported to the World Health Organization. It is a situation, the UN said, "made all the more tragic by our long-standing knowledge that these diseases are easily preventable."
SEE ALSO : A CID R AIN ; A GRICULTURE ; C LEAN W ATER A CT ; C RYPTOSPORIDIOSIS ; DDT (D ICHLORODIPHENYL TRICHLOROETHANE) ; H EALTH, H UMAN ; N ONPOINT S OURCE P OLLUTION ; PCBs (P OLYCHLORINATED B IPHENYLS) ; P OINT S OURCE ; S NOW, J OHN ; W ASTEWATER T REATMENT ; W ATER T REATMENT .
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You can help prevent water pollution by simply not littering. Street trash that washes down storm drains is a major source of floatable debris. Properly dispose of used oil; oil poured down storm drains and sewers is a major source of petroleum pollution. Use nonphosphate detergents for dish and clothes washing. Don't overfertilize lawns and use integrated pest management practices to reduce pesticide use. Use hazardous waste collection programs to dispose of batteries, fluorescent lights that contain mercury, unused oil, paint remover, pesticides and old household chemicals.
The Great Lakes Basin includes areas of the eight Great Lakes states: New York, Pennsylvania, Ohio, Minnesota, Indiana, Illinois, Wisconsin, and Michigan. In 1995, the U.S. Environmental Protection Agency (EPA) and the Great Lakes states agreed to a plan called the Great Lakes Initiative, aimed at reducing pollution and restoring the health of the Great Lakes. The plan included setting water quality standards for twenty-nine pollutants. In 2000, the EPA initiated a ten-year phase-out of the use of mixing zones for bioaccumulative chemicals in the Great Lakes. The EPA says this ruling will reduce discharges of toxic chemicals by 700,000 pounds a year.