water pollution

(ecology) Contamination of water by materials such as sewage effluent, chemicals, detergents, and fertilizer runoff.

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A change in the chemical, physical, biological, and radiological quality of water that is injurious to its existing, intended, or potential uses (for example, boating, waterskiing, swimming, the consumption of fish, and the health of aquatic organisms and ecosystems). The term “water pollution” generally refers to human-induced (anthropogenic) changes to water quality. Thus, the discharge of toxic chemicals from a pipe or the release of livestock waste into a nearby water body is considered pollution. Conversely, nutrients that originate from animals in the wild or toxins that originate from natural processes are not considered pollution.

The contamination of ground water, rivers, lakes, wetlands, estuaries, and oceans can threaten the health of humans and aquatic life. Sources of water pollution are generally divided into two categories. The first is point-source pollution, in which contaminants are discharged from a discrete location. Sewage outfalls and oil spills are examples of point-source pollution. The second category is non-point-source or diffuse pollution, referring to all of the other discharges that deliver contaminants to water bodies. Acid rain and unconfined runoff from agricultural or urban areas are examples of non-point-source pollution. The principal contaminants of water include toxic chemicals, nutrients and biodegradable organics, and bacterial and viral pathogens.

Water pollution can threaten human health when pollutants enter the body via skin exposure or through the direct consumption of contaminated food or drinking water. Priority pollutants, including dichlorodiphenyl trichloroethane (DDT) and polychlorinated biphenyls (PCBs), persist in the natural environment and bioaccumulate in the tissues of aquatic organisms. These persistent organic pollutants are transferred up the food chain (in a process called biomagnification), and they can reach levels of concern in fish species that are eaten by humans. Finally, bacteria and viral pathogens can pose a public health risk for those who drink contaminated water or eat raw shellfish from polluted water bodies. See also Environmental toxicology; Food web.

Contaminants have a significant impact on aquatic ecosystems. for example, enrichment of water bodies with nutrients (principally nitrogen and phosphorus) can result in the growth of algae and other aquatic plants that shade or clog streams. If wastewater containing biodegradable organic matter is discharged into a stream with inadequate dissolved oxygen, the water downstream of the point of discharge will become anaerobic and will be turbid and dark. Settleable solids, if present, will be deposited on the streambed, and anaerobic decomposition will occur. Over the reach of stream where the dissolved-oxygen concentration is zero, a zone of putrefaction will occur with the production of hydrogen sulfide, ammonia, and other odorous gases. Because many fish species require a minimum of 4–5 mg of dissolved oxygen per liter of water, they will be unable to survive in this portion of the stream.

Direct exposures to toxic chemicals is also a health concern for individual aquatic plants and animals. Chemicals (e.g., pesticides) are frequently transported to lakes and rivers via runoff, and they can have unintended and harmful effects on aquatic life. Toxic chemicals have been shown to reduce the growth, survival, reproductive output, and disease resistance of exposed organisms. These effects can have important consequences for the viability of aquatic populations and communities. See also Insecticide.

Wastewater discharges are most commonly controlled through effluent standards and discharge permits. Under this system, discharge permits are issued with limits on the quantity and quality of effluents. Water-quality standards are sets of qualitative and quantitative criteria designed to maintain or enhance the quality of receiving waters. Receiving waters are divided into several classes depending on their uses, existing or intended, with different sets of criteria designed to protect uses such as drinking water supply, bathing, boating, fresh-water and shellfish harvesting, and outdoor sports for seawater. For toxic compounds, chemical-specific or whole-effluent toxicity studies are used to develop standards and criteria. In the chemical-specific approach, individual criteria are used for each toxic chemical detected in the wastewater. Criteria can be developed to protect aquatic life against acute and chronic effects and to safeguard humans against deleterious health effects, including cancer. In the whole-effluent approach, toxicity or bioassay tests are used to determine the concentration at which the wastewater induces acute or chronic toxicity effects. See also Hazardous waste; Sewage disposal; Sewage treatment.

The addition of harmful chemicals to natural water. Sources of water pollution in the United States include industrial waste, runoff from fields treated with chemical fertilizers, and runoff from areas that have been mined.

Extensive water pollution in the United States began in the nineteenth century as a result of urbanization, industrial development, and modern agricultural practices. Although lumbering and mining despoiled individual lakes and rivers, the nation's cities were the sites of the most severe pollution. Early industrial by-products joined human sewage and animal waste to foul drinking water supplies. By the early 1800s, even horses declined New York City's public water, and one quarter of Boston's wells produced undrinkable water. Severe epidemics of the waterborne diseases cholera and typhoid fever swept through major cities, most notably New York in 1832.

The early response to such pollution was not so much to clean the water but rather to build reservoirs and aqueducts to import fresh water for direct delivery to neighborhoods and even some individual homes. Cities built large sewer systems to flush these waters away, usually either out to sea or down a near by river. Sewers thus spread the previously more localized pollution, often fouling the water sources of other cities.

In the 1890s, scientists decisively linked many diseases, including typhoid and cholera, to the presence of human waste in water supplies. Cities began to filter their drinking water with remarkable results. The national urban death rate from typhoid, 36 per 100,000 in 1900, dropped to only 3 per 100,000 by 1935 and was virtually nonexistent by the twentieth century's end. The urban water projects that combined filtration, delivery, and disposal ranked among the largest public works projects in the nation's history. Chicago, for example, reversed the direction of the Chicago and Calumet Rivers, so by 1900 they no longer carried the city's waste into Lake Michigan, its primary source of fresh water. By the end of the twentieth century, New York City moved about 1.5 billion gallons of fresh water through more than 300 miles of aqueducts and 27 artificial lakes.

The industrial pollution of bodies of water not used for drinking proved more difficult to control. In 1912, Congress charged the Public Health Service (PHS) with investigating water pollution. Two years later, the PHS established the first water quality standards. In the 1920s, the service investigated industrial pollution but with little effect. State governments retained the primary responsibility for water regulation. Following the lead of Pennsylvania, many states sought to balance environmental quality with the needs of industry by giving relatively high protection to waters used for drinking supplies while allowing others to be freely used for waste disposal. New Deal programs provided significant federal funds to water pollution control, and over the course of the 1930s the population served by sewage treatment nearly doubled. But those programs left pollution control in the hands of state governments.

After World War II, continued urban pollution and runoff from artificial fertilizers increasingly used in agriculture degraded the water quality of many lakes. Eutrophication occurs when plants and bacteria grow at abnormally high rates due to elevated quantities of nitrogen or phosphorus. The decomposition of this elevated biomass consumes much of the water's oxygen, often leading to a cascade of changes in aquatic ecosystems. Many species of fish grow scarce or die off altogether, and algae "blooms" can make water unsafe to swim in or to drink. Although small urban lakes suffered from eutrophication as early as the 1840s, after World War II, population growth, increasing nitrogen-rich agricultural runoff, and the addition of phosphates to detergents polluted even bodies of water as large as Lake Erie. By 1958, the bottom portion of a 2,600-square-mile portion of the lake was completely without oxygen, and algae grew in mats two feet thick over hundreds of square miles more. The nation's economic prosperity intensified problems, as pollution from heavy industry made some rivers and streams lifeless. In the 1960s, Cleveland authorities pronounced the Cuyahoga River a fire hazard, and at the end of the decade the river actually caught on fire. The more mobile and long-lasting industrial products polluted even waters remote from cities and industry. DDT, other pesticides and synthetic chemicals, mercury, and acid rain threatened numerous species and previously unaffected lakes and streams.

Such manifestations of a deepening pollution crisis prompted environmentalists and lawmakers to redouble pollution-control efforts. The major response, the 1972 Clean Water Act, shifted responsibility for the nation's waterways and water supply to the federal government. In the following decades, federal funds and regulations issued under the act's authority significantly raised standards for water purity. Repeatedly amended, the act halted the rate of water pollution, even in the face of decades of population and economic growth. Most industries and municipalities greatly reduced their pollution discharges, with the consequent reversal of the eutrophication of many bodies of water, including Lake Erie. Nevertheless, "non-point" pollution sources, such as agricultural runoff and vehicle exhaust, continued to degrade water quality. The act made virtually no progress in improving groundwater contamination. At the end of the twentieth century, regulating groundwater quality and grappling with nonpoint pollution remained the most formidable obstacles to those seeking to reverse water pollution.

Bibliography

Elkind, Sarah S. Bay Cities and Water Politics: The Battle for Resources in Boston and Oakland. Lawrence: University Press of Kansas, 1998.

Melosi, Martin V. The Sanitary City: Urban Infrastructure in America from Colonial Times to the Present. Baltimore: Johns Hopkins University Press, 2000.

Outwater, Alice. Water: A Natural History. New York: Basic Books, 1996.

Without healthy water for drinking, cooking, fishing, and farming, the human race would perish. Clean water is also necessary for recreational interests such as swimming, boating, and water skiing. Yet, when Congress began assessing national water quality during the early 1970s, it found that much of the country's groundwater and surface water was contaminated or severely compromised. Studies revealed that the nation's three primary sources of water pollution — industry, agriculture, and municipalities — had been regularly discharging harmful materials into water supplies throughout the country over a number of years.

These harmful materials included organic wastes, sediments, minerals, nutrients, thermal pollutants, toxic chemicals, and other hazardous substances. Organic wastes are produced by animals and humans, and include such things as fecal matter, crop debris, yard clippings, food wastes, rubber, plastic, wood, and disposable diapers. Such wastes require oxygen to decompose. When they are dumped into streams and lakes and begin to break down, they can deprive aquatic life of the oxygen it needs to survive.

Sediments may be deposited into lakes and streams through soil erosion caused by the clearing, excavating, grading, transporting, and filling of land. Minerals, such as iron, copper, chromium, platinum, nickel, zinc, and tin, can be discharged into streams and lakes as a result of various mining activities. Excessive levels of sediments and minerals in water can inhibit the penetration of sunlight, which reduces the production of photosynthetic organisms.

Nutrients, like phosphorus and nitrogen, support the growth of algae and other plants forming the lower levels of the food chain. However, excessive levels of nutrients from sources such as fertilizer can cause eutrophication, which is the overgrowth of aquatic vegetation. This overgrowth clouds the water and smothers some plants. Over time, excessive nutrient levels can accelerate the natural process by which bodies of water evolve into dry land.

Thermal pollution results from the release of heated water into lakes and streams. Most thermal pollution is generated by power plant cooling systems. Power plants use water to cool their reactors and turbines, and discharge it into lakes and tributaries after it has become heated. Higher water temperatures accelerate biological and chemical processes in rivers and streams, reducing the water's ability to retain dissolved oxygen. This can hasten the growth of algae and disrupt the reproduction of fish.

Toxic chemicals and other hazardous materials present the most imminent threat to water quality. The Environmental Protection Agency (EPA) has identified 403 highly toxic chemicals, which are produced by 577 U.S. companies, manufactured in twelve thousand plants, and stored in four-hundred thousand locations across the country. Some chemical plants incinerate toxic wastes, which produces dangerous by-products like furans and chlorinated dioxins, two of the most deadly carcinogens known to the human race. Other hazardous materials are produced or stored by households (motor oil, antifreeze, paints, and pesticides), dry cleaners (chlorinated solvents), farms (insecticides, fungicides, rodenticides, and herbicides), and gas stations and airports (fuel).

Water pollution regulation consists of a labyrinth of state and federal statutes, administrative rules, and common-law principles.

Statutory Law

Federal statutory regulation of water pollution has been governed primarily by three pieces of legislation: the Refuse Act, the Federal Water Pollution Control Act, and the Clean Water Act. The Rivers and Harbors Appropriations Act of 1899, 33 U.S.C.A. § 401 et seq., commonly known as the Refuse Act, was the first major piece of federal legislation regulating water pollution. The Refuse Act set effluent standards for the discharge of pollutants into bodies of water. An effluent standard limits the amount of pollutant that can be released from a specific point or source, such as a smokestack or sewage pipe. The Refuse Act flatly prohibited pollution discharged from ship and shore installations.

The Refuse Act was followed by the Federal Water Pollution Control Act of 1948 (FWPCA), 33 U.S.C.A. § 1251 et seq. Instead of focusing on sources of pollution through effluent standards, the FWPCA created water quality standards, which prescribed the levels of pollutants permitted in a given body of water. Where the Refuse Act concentrated on deterring specific types of polluters, the FWPCA concentrated on reducing specific types of pollution.

Since 1972, federal regulation of water pollution has been primarily governed by the Clean Water Act (CWA), which overhauled FWCPA. The CWA forbids any person to discharge pollutants into U.S. waters unless the discharge conforms with certain provisions of the act. Among those provisions are several that call upon the EPA to promulgate effluent standards for particular categories of water polluters.

To implement these standards, the CWA requires each polluter to obtain a discharge permit issued by the EPA through the National Pollutant Discharge Elimination System (NPDES). Although the EPA closely monitors water pollution dischargers through the NPDES, primary responsibility for enforcement of the CWA rests with the states. Most states have also drafted permit systems similar to the NPDES. These systems are designed to protect local supplies of groundwater, surface water, and drinking water. Persons who violate either the federal or state permit system face civil fines, criminal penalties, and suspension of their discharge privileges.

The CWA also relies on modern technology to curb water pollution. It requires many polluters to implement the best practicable control technology, the best available technology economically achievable, or the best practicable waste treatment technology. The development of such technology for nontoxic polluters is based on a cost-benefit analysis in which the feasibility and expense of the technology is balanced against the expected benefits to the environment.

The CWA was amended in 1977 to address the nation's increasing concern about toxic pollutants. Pursuant to the 1977 amendments, the EPA increased the number of pollutants it deemed toxic from nine to sixty-five, and set effluent limitations for the twenty-one industries that discharge them. These limitations are based on measures of the danger these pollutants pose to the public health rather than on cost-benefit analyses.

Many states have enacted their own water pollution legislation regulating the discharge of toxic and other pollutants into their streams and lakes.

The mining industry presents persistent water pollution problems for state and federal governments. It has polluted over a thousand miles of streams in Appalachia with acid drainage. In response, the affected state governments now require strip miners to obtain licenses before commencing activity. Many states also require miners to post bonds in an amount sufficient to repair potential damage to surrounding lakes and streams. Similarly, the federal government, under the Mineral Leasing Act, 30 U.S.C.A. § 201 et seq., requires each mining applicant to "submit a plan of construction, operation and rehabilitation" for the affected area, that takes into account the need for "restoration, revegetation and curtailment of erosion."

The commercial timber industry also presents persistent water pollution problems. Tree harvesting, yarding (the collection of felled trees), and road building can all deposit soil sediments into watercourses, thereby reducing the water quality for aquatic life. State governments have offered similar responses to these problems. For instance, clear-cutting (the removal of substantially all the trees from a given area) has been prohibited by most states. Other states have created buffer zones around particularly vulnerable watercourses, and banned unusually harmful activities in certain areas. Enforcement of these water pollution measures has been frustrated by vaguely worded legislation and a scarcity of inspectors in several states.

Common Law

State and federal water pollution statutes provide one avenue of legal recourse for those harmed by water pollution. The common-law doctrines of nuisance, trespass, negligence, strict liability, and riparian ownership provide alternative remedies.

Nuisances can be public or private. Private nuisances interfere with the rights and interests of private citizens, whereas public nuisances interfere with the common rights and interests of the people at large. Both types of nuisance must result from the "unreasonable" activities of a polluter, and inflict "substantial" harm on neighboring landowners. An injury that is minor or inconsequential will not result in liability under common-law nuisance. For example, dumping trace amounts of fertilizer into a stream abutting neighboring property will not amount to a public or private nuisance.

The oil and agricultural industries are frequently involved in state nuisance actions. Oil companies often run afoul of nuisance principles for improperly storing, transporting, and disposing of hazardous materials. Farmers represent a unique class of persons who fall prey to water pollution nuisances almost as often as they create them. Their abundant use of fungicides, herbicides, insecticides, and rodenticides makes them frequent creators of nuisances, and their use of streams, rivers, and groundwater for irrigation systems makes them frequent victims.

Nuisance actions deal primarily with continuing or repetitive injuries. Trespass actions provide relief even when an injury results from a single event. A polluter who spills oil, dumps chemicals, or otherwise contaminates a neighboring water supply on one occasion might avoid liability under nuisance law but not under the law of trespass. Trespass does not require proof of a substantial injury. However, only nominal damages will be awarded to a landowner whose water supply suffers little harm from the trespass of a polluter.

Trespass requires proof that a polluter intentionally or knowingly contaminated a particular course of water. Yet, water contamination often results from unintentional behavior, such as industrial accidents. In such instances, the polluter may be liable under common-law principles of negligence. Negligence occurs when a polluter fails to exercise the degree of care that would be reasonable under the circumstances. Thus, a landowner whose water supply was inadvertently contaminated might bring a successful lawsuit against the polluter for common-law negligence where a lawsuit for nuisance or trespass would fail.

Even when a polluter exercises the utmost diligence to prevent water contamination, an injured landowner may still have recourse under the doctrine of strict liability. Under this doctrine, polluters who engage in "abnormally dangerous" activities are held responsible for any water contamination that results. Courts consider six factors when determining whether a particular activity is abnormally dangerous: the probability that the activity will cause harm to another, the likelihood that the harm will be great, the ability to eliminate the risk by exercising reasonable care, the extent to which the activity is uncommon or unusual, the activity's appropriateness for a particular location, and the activity's value or danger to the community.

The doctrine of strict liability arose out of a national conflict between competing values during the industrial revolution. This conflict pitted those who believed it was necessary to create an environment that promoted commerce against those who believed it was necessary to preserve a healthy and clean environment. For many years, courts were reluctant to impose strict liability on U.S. businesses, out of concern over retarding industrial growth.

Since the early 1970s, courts have placed greater emphasis on preserving a healthy and clean environment. In Cities Service Co. v. State, 312 So. 2d 799 (Fla. App. 1975), the court explained that "though many hazardous activities … are socially desirable, it now seems reasonable that they pay their own way." Cities Service involved a situation in which a dam burst during a phosphate mining operation, releasing a billion gallons of phosphate slime into adjacent waterways, where fish and other aquatic life were killed. The court concluded that this mining activity was abnormally dangerous.

Some activities inherently create abnormally dangerous risks to abutting waterways. In such cases, courts do not employ a balancing test to determine whether an activity is abnormally dangerous. Instead, they consider these activities to be dangerous in and of themselves. The transportation and storage of high explosives and the operation of oil and gas wells are activities courts have held to create inherent risks of abnormally dangerous proportions.

The doctrine of riparian ownership forms the final prong of common-law recovery. A riparian proprietor is the owner of land abutting a stream of water, and has the right to divert the water for any useful purpose. Some courts define the term useful purpose broadly to include almost any purpose whatsoever, whereas other courts define it more narrowly to include only purposes that are reasonable or profitable.

In any event, downstream riparian proprietors are often placed at a disadvantage because the law protects upstream owners' initial use of the water. For example, an upstream proprietor may construct a dam to appropriate a reasonable amount of water without compensating a downstream proprietor. However, cases involving thermal pollution provide an exception to this rule. For example, downstream owners who use river water to make ice can seek injunctive relief to prevent upstream owners from engaging in any activities that raise the water temperature by even one degree Fahrenheit.

See: Environmental Law; Fish and Fishing; Law of the Sea; Mine and Mineral Law; Pollution; Riparian Rights; Solid Wastes, Hazardous Substances, and Toxic Pollutants; Tort Law; Water Rights.

The addition of harmful chemicals to natural water. Sources of water pollution in the United States include industrial waste, run-off from fields treated with chemical fertilizers, and run-off from areas that have been mined.

Raw sewage and industrial waste flows across international borders—New River passes from Mexicali to Calexico, California.

Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans and groundwater). Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds.

Water pollution affects plants and organisms living in these bodies of water. In almost all cases the effect is damaging not only to individual species and populations, but also to the natural biological communities.

Contents 1 Introduction 2 Categories 2.1 Point sources 2.2 Non–point sources 3 Groundwater pollution 4 Causes 4.1 Pathogens 4.2 Chemical and other contaminants 4.3 Thermal pollution 5 Transport and chemical reactions of water pollutants 6 Measurement 6.1 Sampling 6.2 Physical testing 6.3 Chemical testing 6.4 Biological testing 7 Control of pollution 7.1 Domestic sewage 7.2 Industrial wastewater 7.3 Agricultural wastewater 7.4 Construction site stormwater 7.5 Urban runoff (stormwater) 8 See also 9 References 10 External links

Introduction

Millions depend on the polluted Ganges river

Water pollution is a major global problem which requires ongoing evaluation and revision of water resource policy at all levels (international down to individual aquifers and wells). It has been suggested that it is the leading worldwide cause of deaths and diseases,^[1][2] and that it accounts for the deaths of more than 14,000 people daily.^[2] An estimated 700 million Indians have no access to a proper toilet, and 1,000 Indian children die of diarrheal sickness every day.^[3] Some 90% of China's cities suffer from some degree of water pollution,^[4] and nearly 500 million people lack access to safe drinking water.^[5] In addition to the acute problems of water pollution in developing countries, developed countries continue to struggle with pollution problems as well. In the most recent national report on water quality in the United States, 45 percent of assessed stream miles, 47 percent of assessed lake acres, and 32 percent of assessed bay and estuarine square miles were classified as polluted.^[6]

Water is typically referred to as polluted when it is impaired by anthropogenic contaminants and either does not support a human use, such as drinking water, and/or undergoes a marked shift in its ability to support its constituent biotic communities, such as fish. Natural phenomena such as volcanoes, algae blooms, storms, and earthquakes also cause major changes in water quality and the ecological status of water.

Categories

Surface water and groundwater have often been studied and managed as separate resources, although they are interrelated.^[7] Surface water seeps through the soil and becomes groundwater. Conversely, groundwater can also feed surface water sources. Sources of surface water pollution are generally grouped into two categories based on their origin.

Point sources

Point source pollution – Shipyard – Rio de Janeiro.

Point source water pollution refers to contaminants that enter a waterway from a single, identifiable sourcesm, such as a pipe or ditch. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain. The U.S. Clean Water Act (CWA) defines point source for regulatory enforcement purposes.^[8] The CWA definition of point source was amended in 1987 to include municipal storm sewer systems, as well as industrial stormwater, such as from construction sites.^[9]

Non–point sources

Non–point source pollution refers to diffuse contamination that does not originate from a single discrete source. NPS pollution is often the cumulative effect of small amounts of contaminants gathered from a large area. A common example is the leaching out of nitrogen compounds from fertilized agricultural lands. Nutrient runoff in stormwater from "sheet flow" over an agricultural field or a forest are also cited as examples of NPS pollution.

Contaminated storm water washed off of parking lots, roads and highways, called urban runoff, is sometimes included under the category of NPS pollution. However, this runoff is typically channeled into storm drain systems and discharged through pipes to local surface waters, and is a point source. However where such water is not channeled and drains directly to ground it is a non-point source.

Groundwater pollution

See also: Hydrogeology

Interactions between groundwater and surface water are complex. Consequently, groundwater pollution, sometimes referred to as groundwater contamination, is not as easily classified as surface water pollution.^[7] By its very nature, groundwater aquifers are susceptible to contamination from sources that may not directly affect surface water bodies, and the distinction of point vs. non-point source may be irrelevant. A spill or ongoing releases of chemical or radionuclide contaminants into soil (located away from a surface water body) may not create point source or non-point source pollution, but can contaminate the aquifer below, defined as a toxin plume. The movement of the plume, called a plume front, may be analyzed through a hydrological transport model or groundwater model. Analysis of groundwater contamination may focus on the soil characteristics and site geology, hydrogeology, hydrology, and the nature of the contaminants.

Causes

The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical or sensory changes such as elevated temperature and discoloration. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration is often the key in determining what is a natural component of water, and what is a contaminant. High concentrations of naturally-occurring substances can have negative impacts on aquatic flora and fauna.

Oxygen-depleting substances may be natural materials, such as plant matter (e.g. leaves and grass) as well as man-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.^[10]

Many of the chemical substances are toxic. Pathogens can produce waterborne diseases in either human or animal hosts.^[11] Alteration of water's physical chemistry includes acidity (change in pH), electrical conductivity, temperature, and eutrophication. Eutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases in the primary productivity of the ecosystem. Depending on the degree of eutrophication, subsequent negative environmental effects such as anoxia (oxygen depletion) and severe reductions in water quality may occur, affecting fish and other animal populations.

Pathogens

A manhole cover unable to contain a sanitary sewer overflow.

Coliform bacteria are a commonly used bacterial indicator of water pollution, although not an actual cause of disease. Other microorganisms sometimes found in surface waters which have caused human health problems include:

• Burkholderia pseudomallei
• Cryptosporidium parvum
• Giardia lamblia
• Salmonella
• Novovirus and other viruses
• Parasitic worms (helminths).^[12][13]

High levels of pathogens may result from inadequately treated sewage discharges.^[14] This can be caused by a sewage plant designed with less than secondary treatment (more typical in less-developed countries). In developed countries, older cities with aging infrastructure may have leaky sewage collection systems (pipes, pumps, valves), which can cause sanitary sewer overflows. Some cities also have combined sewers, which may discharge untreated sewage during rain storms.^[15]

Pathogen discharges may also be caused by poorly managed livestock operations.

Chemical and other contaminants

Muddy river polluted by sediment. Photo courtesy of United States Geological Survey.

Contaminants may include organic and inorganic substances.

Organic water pollutants include:

• Detergents
• Disinfection by-products found in chemically disinfected drinking water, such as chloroform
• Food processing waste, which can include oxygen-demanding substances, fats and grease
• Insecticides and herbicides, a huge range of organohalides and other chemical compounds
• Petroleum hydrocarbons, including fuels (gasoline, diesel fuel, jet fuels, and fuel oil) and lubricants (motor oil), and fuel combustion byproducts, from stormwater runoff^[16]
• Tree and bush debris from logging operations
• Volatile organic compounds (VOCs), such as industrial solvents, from improper storage.
• Chlorinated solvents, which are dense non-aqueous phase liquids (DNAPLs), may fall to the bottom of reservoirs, since they don't mix well with water and are denser.
  • Polychlorinated biphenyl (PCBs)
  • Trichloroethylene
• Perchlorate
• Various chemical compounds found in personal hygiene and cosmetic products

A garbage collection boom in an urban-area stream in Auckland, New Zealand.

Inorganic water pollutants include:

• Acidity caused by industrial discharges (especially sulfur dioxide from power plants)
• Ammonia from food processing waste
• Chemical waste as industrial by-products
• Fertilizers containing nutrients--nitrates and phosphates—which are found in stormwater runoff from agriculture, as well as commercial and residential use^[16]
• Heavy metals from motor vehicles (via urban stormwater runoff)^[16][17] and acid mine drainage
• Silt (sediment) in runoff from construction sites, logging, slash and burn practices or land clearing sites

Macroscopic Pollution in Parks Milwaukee, WI

Macroscopic pollution—large visible items polluting the water—may be termed "floatables" in an urban stormwater context, or marine debris when found on the open seas, and can include such items as:

• Trash or garbage (e.g. paper, plastic, or food waste) discarded by people on the ground, along with accidental or intentional dumping of rubbish, that are washed by rainfall into storm drains and eventually discharged into surface waters
• Nurdles, small ubiquitous waterborne plastic pellets
• Shipwrecks, large derelict ships

Thermal pollution

Main article: Thermal pollution

Potrero Generating Station discharges heated water into San Francisco Bay.^[18]

Thermal pollution is the rise or fall in the temperature of a natural body of water caused by human influence. Thermal pollution, unlike chemical pollution, results in a change in the physical properties of water. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. Elevated water temperatures decreases oxygen levels (which can kill fish) and affects ecosystem composition, such as invasion by new thermophilic species. Urban runoff may also elevate temperature in surface waters.

Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers.

Transport and chemical reactions of water pollutants

See also: Marine pollution

Most water pollutants are eventually carried by rivers into the oceans. In some areas of the world the influence can be traced hundred miles from the mouth by studies using hydrology transport models. Advanced computer models such as SWMM or the DSSAM Model have been used in many locations worldwide to examine the fate of pollutants in aquatic systems. Indicator filter feeding species such as copepods have also been used to study pollutant fates in the New York Bight, for example. The highest toxin loads are not directly at the mouth of the Hudson River, but 100 kilometers south, since several days are required for incorporation into planktonic tissue. The Hudson discharge flows south along the coast due to coriolis force. Further south then are areas of oxygen depletion, caused by chemicals using up oxygen and by algae blooms, caused by excess nutrients from algal cell death and decomposition. Fish and shellfish kills have been reported, because toxins climb the food chain after small fish consume copepods, then large fish eat smaller fish, etc. Each successive step up the food chain causes a stepwise concentration of pollutants such as heavy metals (e.g. mercury) and persistent organic pollutants such as DDT. This is known as biomagnification, which is occasionally used interchangeably with bioaccumulation.

A polluted river draining an abandoned copper mine on Anglesey

Large gyres (vortexes) in the oceans trap floating plastic debris. The North Pacific Gyre for example has collected the so-called "Great Pacific Garbage Patch" that is now estimated at 100 times the size of Texas. Many of these long-lasting pieces wind up in the stomachs of marine birds and animals. This results in obstruction of digestive pathways which leads to reduced appetite or even starvation.

Many chemicals undergo reactive decay or chemically change especially over long periods of time in groundwater reservoirs. A noteworthy class of such chemicals is the chlorinated hydrocarbons such as trichloroethylene (used in industrial metal degreasing and electronics manufacturing) and tetrachloroethylene used in the dry cleaning industry (note latest advances in liquid carbon dioxide in dry cleaning that avoids all use of chemicals). Both of these chemicals, which are carcinogens themselves, undergo partial decomposition reactions, leading to new hazardous chemicals (including dichloroethylene and vinyl chloride).

Groundwater pollution is much more difficult to abate than surface pollution because groundwater can move great distances through unseen aquifers. Non-porous aquifers such as clays partially purify water of bacteria by simple filtration (adsorption and absorption), dilution, and, in some cases, chemical reactions and biological activity: however, in some cases, the pollutants merely transform to soil contaminants. Groundwater that moves through cracks and caverns is not filtered and can be transported as easily as surface water. In fact, this can be aggravated by the human tendency to use natural sinkholes as dumps in areas of Karst topography.

There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. An example is silt-bearing surface runoff, which can inhibit the penetration of sunlight through the water column, hampering photosynthesis in aquatic plants.

Measurement

Environmental Scientists preparing water autosamplers.

Water pollution may be analyzed through several broad categories of methods: physical, chemical and biological. Most involve collection of samples, followed by specialized analytical tests. Some methods may be conducted in situ, without sampling, such as temperature. Government agencies and research organizations have published standardized, validated analytical test methods to facilitate the comparability of results from disparate testing events.^[19]

Sampling

Sampling of water for physical or chemical testing can be done by several methods, depending on the accuracy needed and the characteristics of the contaminant. Many contamination events are sharply restricted in time, most commonly in association with rain events. For this reason "grab" samples are often inadequate for fully quantifying contaminant levels. Scientists gathering this type of data often employ auto-sampler devices that pump increments of water at either time or discharge intervals.

Sampling for biological testing involves collection of plants and/or animals from the surface water body. Depending on the type of assessment, the organisms may be identified for biosurveys (population counts) and returned to the water body, or they may be dissected for bioassays to determine toxicity.

Further information: Water quality#Sampling and Measurement

Physical testing

Common physical tests of water include temperature, solids concentrations (e.g., total suspended solids (TSS)) and turbidity.

Chemical testing

See also: water chemistry analysis and environmental chemistry

Water samples may be examined using the principles of analytical chemistry. Many published test methods are available for both organic and inorganic compounds. Frequently used methods include pH, biochemical oxygen demand (BOD),^[20] chemical oxygen demand (COD),^[21] nutrients (nitrate and phosphorus compounds), metals (including copper, zinc, cadmium, lead and mercury), oil and grease, total petroleum hydrocarbons (TPH), and pesticides.

Biological testing

Main article: Bioindicator

Biological testing involves the use of plant, animal, and/or microbial indicators to monitor the health of an aquatic ecosystem.

For microbial testing of drinking water, see Bacteriological water analysis.

Control of pollution

Domestic sewage

Main article: Sewage treatment

Deer Island Waste Water Treatment Plant serving Boston, Massachusetts and vicinity.

Domestic sewage is 99.9 percent pure water, while the other 0.1 percent are pollutants. Although found in low concentrations, these pollutants pose risk on a large scale.^[22] In urban areas, domestic sewage is typically treated by centralized sewage treatment plants. In the U.S., most of these plants are operated by local government agencies, frequently referred to as publicly owned treatment works (POTW). Municipal treatment plants are designed to control conventional pollutants: BOD and suspended solids. Well-designed and operated systems (i.e., secondary treatment or better) can remove 90 percent or more of these pollutants. Some plants have additional sub-systems to treat nutrients and pathogens. Most municipal plants are not designed to treat toxic pollutants found in industrial wastewater.^[23]

Cities with sanitary sewer overflows or combined sewer overflows employ one or more engineering approaches to reduce discharges of untreated sewage, including:

• utilizing a green infrastructure approach to improve stormwater management capacity throughout the system, and reduce the hydraulic overloading of the treatment plant^[24]
• repair and replacement of leaking and malfunctioning equipment^[15]
• increasing overall hydraulic capacity of the sewage collection system (often a very expensive option).

A household or business not served by a municipal treatment plant may have an individual septic tank, which treats the wastewater on site and discharges into the soil. Alternatively, domestic wastewater may be sent to a nearby privately owned treatment system (e.g. in a rural community).

Industrial wastewater

Main article: Industrial wastewater treatment

Dissolved air flotation system for treating industrial wastewater.

Some industrial facilities generate ordinary domestic sewage that can be treated by municipal facilities. Industries that generate wastewater with high concentrations of conventional pollutants (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile organic compounds) or other nonconventional pollutants such as ammonia, need specialized treatment systems. Some of these facilities can install a pre-treatment system to remove the toxic components, and then send the partially-treated wastewater to the municipal system. Industries generating large volumes of wastewater typically operate their own complete on-site treatment systems.

Some industries have been successful at redesigning their manufacturing processes to reduce or eliminate pollutants, through a process called pollution prevention.

Heated water generated by power plants or manufacturing plants may be controlled with:

• cooling ponds, man-made bodies of water designed for cooling by evaporation, convection, and radiation
• cooling towers, which transfer waste heat to the atmosphere through evaporation and/or heat transfer
• cogeneration, a process where waste heat is recycled for domestic and/or industrial heating purposes.^[25]

Agricultural wastewater

Main article: Agricultural wastewater treatment

Riparian buffer lining a creek in Iowa

Nonpoint source controls
Sediment (loose soil) washed off fields is the largest source of agricultural pollution in the United States.^[10] Farmers may utilize erosion controls to reduce runoff flows and retain soil on their fields. Common techniques include contour plowing, crop mulching, crop rotation, planting perennial crops and installing riparian buffers.^{[26][27]:pp. 4-95–4-96}

Nutrients (nitrogen and phosphorus) are typically applied to farmland as commercial fertilizer; animal manure; or spraying of municipal or industrial wastewater (effluent) or sludge. Nutrients may also enter runoff from crop residues, irrigation water, wildlife, and atmospheric deposition.^{[27]:p. 2-9} Farmers can develop and implement nutrient management plans to reduce excess application of nutrients.^{[26][27]:pp. 4-37–4-38}

To minimize pesticide impacts, farmers may use Integrated Pest Management (IPM) techniques (which can include biological pest control) to maintain control over pests, reduce reliance on chemical pesticides, and protect water quality.^[28]

Feedlot in the United States

Point source wastewater treatment
Farms with large livestock and poultry operations, such as factory farms, are called concentrated animal feeding operations or feedlots in the US and are being subject to increasing government regulation.^[29][30] Animal slurries are usually treated by containment in anaerobic lagoons before disposal by spray or trickle application to grassland. Constructed wetlands are sometimes used to facilitate treatment of animal wastes. Some animal slurries are treated by mixing with straw and composted at high temperature to produce a bacteriologically sterile and friable manure for soil improvement.

Construction site stormwater

Silt fence installed on a construction site.

Sediment from construction sites is managed by installation of:

• erosion controls, such as mulching and hydroseeding, and
• sediment controls, such as sediment basins and silt fences.^[31]

Discharge of toxic chemicals such as motor fuels and concrete washout is prevented by use of:

• spill prevention and control plans, and
• specially designed containers (e.g. for concrete washout) and structures such as overflow controls and diversion berms.^[32]

Urban runoff (stormwater)

Main article: Urban runoff

See also: Green infrastructure

Retention basin for controlling urban runoff

Effective control of urban runoff involves reducing the velocity and flow of stormwater, as well as reducing pollutant discharges. Local governments use a variety of stormwater management techniques to reduce the effects of urban runoff. These techniques, called best management practices (BMPs) in the U.S., may focus on water quantity control, while others focus on improving water quality, and some perform both functions.^[33]

Pollution prevention practices include low-impact development techniques, installation of green roofs and improved chemical handling (e.g. management of motor fuels & oil, fertilizers and pesticides).^[34] Runoff mitigation systems include infiltration basins, bioretention systems, constructed wetlands, retention basins and similar devices.^[35][36]

Thermal pollution from runoff can be controlled by stormwater management facilities that absorb the runoff or direct it into groundwater, such as bioretention systems and infiltration basins. Retention basins tend to be less effective at reducing temperature, as the water may be heated by the sun before being discharged to a receiving stream.^{[33]:p. 5-58}

See also

	Water portal
	Sustainable development portal
	Environment portal

	Book: Pollution
Wikipedia books are collections of articles that can be downloaded or ordered in print.

• Aquatic toxicology
• Cultural eutrophication
• Interprovincial Cooperatives v. The Queen (Supreme Court of Canada)
• Oil spill
• Paper pollution
• Peak water (water resources planning concept)
• Trophic state index (water quality indicator for lakes)
• Watershed Central

References

1. ^ Pink, Daniel H. (April 19, 2006). "Investing in Tomorrow's Liquid Gold". Yahoo. http://finance.yahoo.com/columnist/article/trenddesk/3748. 
2. ^ ^{a b} West, Larry (March 26, 2006). "World Water Day: A Billion People Worldwide Lack Safe Drinking Water". About. http://environment.about.com/od/environmentalevents/a/waterdayqa.htm. 
3. ^ "A special report on India: Creaking, groaning: Infrastructure is India’s biggest handicap". The Economist. December 11, 2008. http://www.economist.com/specialreports/displaystory.cfm?story_id=12749787. 
4. ^ "China says water pollution so severe that cities could lack safe supplies". Chinadaily.com.cn. June 7, 2005.
5. ^ "As China Roars, Pollution Reaches Deadly Extremes". The New York Times. August 26, 2007.
6. ^ United States Environmental Protection Agency (EPA). Washington, DC. "The National Water Quality Inventory: Report to Congress for the 2002 Reporting Cycle – A Profile." October 2007. Fact Sheet No. EPA 841-F-07-003.
7. ^ ^{a b} United States Geological Survey (USGS). Denver, CO. "Ground Water and Surface Water: A Single Resource." USGS Circular 1139. 1998.
8. ^ Clean Water Act, section 502(14), 33 U.S.C. § 1362 (14).
9. ^ CWA section 402(p), 33 U.S.C. § 1342(p)
10. ^ ^{a b} EPA. "Protecting Water Quality from Agricultural Runoff." Fact Sheet No. EPA-841-F-05-001. March 2005.
11. ^ C. Michael Hogan (2010). "Water pollution.". Encyclopedia of Earth. Topic ed. Mark McGinley; ed. in chief C. Cleveland. National Council on Science and the Environment, Washington, DC.
12. ^ USGS. Reston, VA. "A Primer on Water Quality." FS-027-01. March 2001.
13. ^ Schueler, Thomas R. "Microbes and Urban Watersheds: Concentrations, Sources, & Pathways." Reprinted in The Practice of Watershed Protection. 2000. Center for Watershed Protection. Ellicott City, MD.
14. ^ EPA. “Illness Related to Sewage in Water.” Accessed February 20, 2009.
15. ^ ^{a b} EPA. "Report to Congress: Impacts and Control of CSOs and SSOs." August 2004. Document No. EPA-833-R-04-001.
16. ^ ^{a b c} G. Allen Burton, Jr., Robert Pitt (2001). Stormwater Effects Handbook: A Toolbox for Watershed Managers, Scientists, and Engineers. New York: CRC/Lewis Publishers. ISBN 0-87371-924-7. http://unix.eng.ua.edu/~rpitt/Publications/BooksandReports/Stormwater%20Effects%20Handbook%20by%20%20Burton%20and%20Pitt%20book/MainEDFS_Book.html.  Chapter 2.
17. ^ Schueler, Thomas R. "Cars Are Leading Source of Metal Loads in California." Reprinted in The Practice of Watershed Protection. 2000. Center for Watershed Protection. Ellicott City, MD.
18. ^ Selna, Robert (2009). "Power plant has no plans to stop killing fish." San Francisco Chronicle, January 2, 2009.
19. ^ For example, see Clescerl, Leonore S.(Editor), Greenberg, Arnold E.(Editor), Eaton, Andrew D. (Editor). Standard Methods for the Examination of Water and Wastewater (20th ed.) American Public Health Association, Washington, DC. ISBN 0-87553-235-7. This publication is also available on CD-ROM and online by subscription.
20. ^ Newton, David (2008). Chemistry of the Environment. Checkmark Books. pp. 102. ISBN 0816077479. 
21. ^ Newton, David (2008). Chemistry of the Environment. Checkmark Books. pp. 104. ISBN 0816077479. 
22. ^ "Environmental works: types of sewage.Encyclopaedia Britannica Online. N.p., 2009. Web. October 9, 2009. <http://www.search.eb.com/eb/article-72342>
23. ^ EPA (2004)."Primer for Municipal Wastewater Treatment Systems." Document No. EPA 832-R-04-001.
24. ^ EPA. "Green Infrastructure Case Studies: Philadelphia." December 9, 2008.
25. ^ EPA (1997). Profile of the Fossil Fuel Electric Power Generation Industry (Report). http://www.epa.gov/compliance/resources/publications/assistance/sectors/notebooks/fossil.html.  Document No. EPA/310-R-97-007. p. 24
26. ^ ^{a b} U.S. Natural Resources Conservation Service (NRCS). Washington, DC. "National Conservation Practice Standards." National Handbook of Conservation Practices. Accessed March 28, 2009.
27. ^ ^{a b c} EPA. "National Management Measures to Control Nonpoint Source Pollution from Agriculture." July 2003. Document No. EPA-841-B-03-004.
28. ^ EPA. "Integrated Pest Management Principles." March 13, 2008.
29. ^ EPA. "Animal Feeding Operations." December 15, 2008.
30. ^ Iowa Department of Natural Resources. Des Moines, IA. "Animal Feeding Operations in Iowa." Accessed March 5, 2009.
31. ^ Tennessee Department of Environment and Conservation. Nashville, TN."Tennessee Erosion and Sediment Control Handbook." 2002.
32. ^ EPA (2006). "Construction Site Stormwater Runoff Control." National Menu of Stormwater Best Management Practices.
33. ^ ^{a b} EPA (1999)."Preliminary Data Summary of Urban Storm Water Best Management Practices." Chapter 5. Document No. EPA-821-R-99-012.
34. ^ EPA. "Fact Sheet: Low Impact Development and Other Green Design Strategies." October 9, 2008.
35. ^ California Stormwater Quality Association. Menlo Park, CA. "Stormwater Best Management Practice (BMP) Handbooks." 2003.
36. ^ New Jersey Department of Environmental Protection. Trenton, NJ. "New Jersey Stormwater Best Management Practices Manual." April 2004.

External links

Wikimedia Commons has media related to: Water pollution

Overview Information

• "Troubled Waters"-video from "Strange Days on Planet Earth" by National Geographic & PBS
• "Issues: Water" – Guides, news and reports from US Natural Resources Defense Council

Analytical Tools and Other Specialized Resources

• Water pollution advice for businesses on NetRegs.gov.uk
• Bibliography on Water Resources and International Law – Peace Palace Library (Netherlands)
• EUGRIS – place for Soil and Water Management in Europe
• Causal Analysis/Diagnosis Decision Information System (CADDIS)-EPA guide for identifying pollution problems -stressor identification

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