Water is a unique substance, because it can naturally renew and cleanse itself, by allowing pollutants to settle out (through the process of sedimentation) or break down, or by diluting the pollutants to a point where they are not in harmful concentrations. However, this natural process takes time, and is difficult when excessive quantities of harmful contaminants are added to the water. And humans are using more and more materials that are polluting the water sources that we drink from. In nine of the last ten years, large blue-green algae blooms have appeared on the northern part of Lake Winnipeg. These are caused by excess phosphorus in the water. Fertilizer use is 15 times higher today than it was in 1945. Beach closures are becoming increasingly common. The list of pollutants is long and the signs of water pollution surround us, but the point is this: we are dumping contaminants into the small portion of water on the planet that is fit for drinking.
What is pollution?
Pollution can be defined in several ways. Water pollution occurs when energy and other materials are released, degrading the quality of the water for other users. Water pollution includes all of the waste materials that cannot be naturally broken down by water. In other words, anything that is added to the water, above and beyond its capacity to break it down, is pollution. Pollution, in certain circumstances, can be caused by nature itself, such as when water flows through soils with high acidities. But more often that not, human actions are responsible for the pollutants that enter the water.
INTRODUCTION
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. Often, however, a change that adversely affects one organism may be advantageous to another. Nutrients that stimulate growth of bacteria and other oxygen-consuming decomposers in a river or lake, for example, are good for the bacteria but can be lethal to game fish populations. Similarly, warming of waters by industrial discharges may be deadly for some species but may create optimal conditions for others. Whether the quality of the water has suffered depends on your perspective. There are natural sources of water contamination, such as arsenic springs, oil seeps, and sedimentation from desert erosion, but most environmental scientists restrict their focus on water pollution to factors caused by human actions and that detract from conditions and uses that humans consider desirable.
Water pollution control regulations usually distinguish between point and nonpoint pollution sources. Factories, power plants, sewage treatment facilities, underground mines and oil wells, for example, are classified as point sources because they release pollution from specific locations, such as drain pipes, ditches, or sewer outfalls. These individual, easily identifiable sources are relatively easy to monitor and regulate. Their unwanted contents can be diverted and treated before discharge. In contrast, nonpoint pollution sources are scattered or diffuse, having no specific location where they originate or discharge into water bodies. Some nonpoint sources include runoff from farm fields, feedlots, lawns, gardens, golf courses, construction sites, logging areas, roads, streets, and parking lots. Whereas point sources often are fairly uniform and predictable, nonpoint runoff often is highly irregular. The first heavy rainfall after a dry period, for example, may flush high concentrations of oil, gasoline, rubber, and trash off city streets, while subsequent runoff may have much lower levels of these contaminants. The irregular timing of these events, as well as their multiple sources, scattered location, and lack of specific ownership make them much more difficult to monitor, regulate, and treat than point sources.
Among the most important categories of water pollutants are sediment, infectious agents, toxins, oxygen demanding wastes, plant nutrients, and thermal changes. Sediment (dirt, soil, insoluble solids) and trash make up the largest volume and most visible type of water pollution in most rivers and lakes. Rivers have always carried silt, sand, and gravel down to the oceans but human-caused erosion now probably rivals the effects of geologic forces. Worldwide, erosion from croplands, forests, grazing lands, and construction sites is estimated to add some 75 billion tons of sediment each year to rivers and lakes. This sediment smothers gravel beds in which fish lay their eggs. It fills lakes and reservoirs, obstructs shipping channels, clogs hydroelectric turbines, and makes drinking water purification more costly. The most serious water pollutant in terms of human health worldwide is pathogenic (disease-causing) organisms. Among the most deadly waterborne diseases are cholera, dysentery, polio, infectious hepatitis, and schistosomiasis. Together, these diseases probably cause at least two billion new cases of disease each year and kill somewhere between six and eight million people. The largest source of infectious agents in water is untreated or insufficiently treated human and animal waste. The United Nations estimates that about half the world's population has inadequate sanitation and that at least one billion people lack access to clean drinking water.
Toxins are poisonous chemicals that interfere with basic cellular metabolism (the enzyme reactions that make life possible). Among some important toxins found in water are metals (lead, mercury, cadmium, nickel), inorganic elements (selenium, arsenic), acids, salts, and organic chemicals such as pesticides, solvents, and industrial wastes. Some of these materials are so toxic that exposure to extremely low levels (perhaps even parts per billion) can be dangerous. Others, while not usually found in toxic concentrations in most water bodies, can be taken up by living organisms, altered into more toxic forms, stored, and concentrated to dangerous levels through food chains. For example, fish in lakes and rivers in many parts of the United States have accumulated mercury (released mainly by power plants, waste disposal, and industrial processes) to levels that are considered a threat to human health for those who eat fish on a regular basis.
While we have not yet met our national goal in the United States of making all surface waters "fishable and swimmable," investments in sewage treatment, regulation of toxic waste disposal and factory effluents, and other forms of pollution control have resulted in significant water quality increases many areas. Nearly 90% of all the river miles and lake acres that are assessed for water quality in the United States fully or partly support their designed uses. Lake Erie, for instance, which was widely described in the 1970s as being "dead," now has much cleaner water and more healthy fish populations than would ever have been thought possible 25 years ago. Unfortunately, surface waters in developing countries have not experienced similar progress in pollution control. In most developing countries, only a tiny fraction of human wastes are treated before being dumped into rivers, lakes, or the ocean. In consequence, water pollution levels often are appalling. In India, for example, two-thirds of all surface waters are considered dangerous to human health
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. Often, however, a change that adversely affects one organism may be advantageous to another. Nutrients that stimulate growth of bacteria and other oxygen-consuming decomposers in a river or lake, for example, are good for the bacteria but can be lethal to game fish populations. Similarly, warming of waters by industrial discharges may be deadly for some species but may create optimal conditions for others. Whether the quality of the water has suffered depends on your perspective. There are natural sources of water contamination, such as arsenic springs, oil seeps, and sedimentation from desert erosion, but most environmental scientists restrict their focus on water pollution to factors caused by human actions and that detract from conditions and uses that humans consider desirable.
Water pollution control regulations usually distinguish between point and nonpoint pollution sources. Factories, power plants, sewage treatment facilities, underground mines and oil wells, for example, are classified as point sources because they release pollution from specific locations, such as drain pipes, ditches, or sewer outfalls. These individual, easily identifiable sources are relatively easy to monitor and regulate. Their unwanted contents can be diverted and treated before discharge. In contrast, nonpoint pollution sources are scattered or diffuse, having no specific location where they originate or discharge into water bodies. Some nonpoint sources include runoff from farm fields, feedlots, lawns, gardens, golf courses, construction sites, logging areas, roads, streets, and parking lots. Whereas point sources often are fairly uniform and predictable, nonpoint runoff often is highly irregular. The first heavy rainfall after a dry period, for example, may flush high concentrations of oil, gasoline, rubber, and trash off city streets, while subsequent runoff may have much lower levels of these contaminants. The irregular timing of these events, as well as their multiple sources, scattered location, and lack of specific ownership make them much more difficult to monitor, regulate, and treat than point sources.
Among the most important categories of water pollutants are sediment, infectious agents, toxins, oxygen demanding wastes, plant nutrients, and thermal changes. Sediment (dirt, soil, insoluble solids) and trash make up the largest volume and most visible type of water pollution in most rivers and lakes. Rivers have always carried silt, sand, and gravel down to the oceans but human-caused erosion now probably rivals the effects of geologic forces. Worldwide, erosion from croplands, forests, grazing lands, and construction sites is estimated to add some 75 billion tons of sediment each year to rivers and lakes. This sediment smothers gravel beds in which fish lay their eggs. It fills lakes and reservoirs, obstructs shipping channels, clogs hydroelectric turbines, and makes drinking water purification more costly. The most serious water pollutant in terms of human health worldwide is pathogenic (disease-causing) organisms. Among the most deadly waterborne diseases are cholera, dysentery, polio, infectious hepatitis, and schistosomiasis. Together, these diseases probably cause at least two billion new cases of disease each year and kill somewhere between six and eight million people. The largest source of infectious agents in water is untreated or insufficiently treated human and animal waste. The United Nations estimates that about half the world's population has inadequate sanitation and that at least one billion people lack access to clean drinking water.
Toxins are poisonous chemicals that interfere with basic cellular metabolism (the enzyme reactions that make life possible). Among some important toxins found in water are metals (lead, mercury, cadmium, nickel), inorganic elements (selenium, arsenic), acids, salts, and organic chemicals such as pesticides, solvents, and industrial wastes. Some of these materials are so toxic that exposure to extremely low levels (perhaps even parts per billion) can be dangerous. Others, while not usually found in toxic concentrations in most water bodies, can be taken up by living organisms, altered into more toxic forms, stored, and concentrated to dangerous levels through food chains. For example, fish in lakes and rivers in many parts of the United States have accumulated mercury (released mainly by power plants, waste disposal, and industrial processes) to levels that are considered a threat to human health for those who eat fish on a regular basis.
While we have not yet met our national goal in the United States of making all surface waters "fishable and swimmable," investments in sewage treatment, regulation of toxic waste disposal and factory effluents, and other forms of pollution control have resulted in significant water quality increases many areas. Nearly 90% of all the river miles and lake acres that are assessed for water quality in the United States fully or partly support their designed uses. Lake Erie, for instance, which was widely described in the 1970s as being "dead," now has much cleaner water and more healthy fish populations than would ever have been thought possible 25 years ago. Unfortunately, surface waters in developing countries have not experienced similar progress in pollution control. In most developing countries, only a tiny fraction of human wastes are treated before being dumped into rivers, lakes, or the ocean. In consequence, water pollution levels often are appalling. In India, for example, two-thirds of all surface waters are considered dangerous to human health
Water pollution categories
Surface water and groundwater have often been studied and managed as separate resources, although they are interrelated.[7] Sources of surface water pollution are generally grouped into two categories based on their origin.
Point source pollution
D:\lpu assignment\physics term paper\Water_pollution_files\220px-Jacuecanga_Angra_dos_Reis_Rio_de_Janeiro_Brazil_Brasfe.JPG
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngPoint source pollution - Shipyard - Rio de Janeiro.
Point source pollution refers to contaminants that enter a waterway through a discrete conveyance, 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. The CWA definition of point source was amended in 1987 to include municipalstorm sewer systems, as well as industrial stormwater, such as from construction sites.
Non-point source pollution
Non-point source (NPS) 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. The leaching out of nitrogen compounds from agricultural land which has been fertilized is a typical example. 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
GROUND WATER POLLUTION
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. 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, a plume front, can be part of 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 of water pollution
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.
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.
Many of the chemical substances are toxic. Pathogens can produce waterborne diseases in either human or animal hosts. 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
D:\lpu assignment\physics term paper\Water_pollution_files\240px-Sewer_overflow_RI_EPA.jpg
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngA 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
D:\lpu assignment\physics term paper\Water_pollution_files\240px-Muddy_USGS.jpg
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngMuddy 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.
Various chemical compounds found in personal hygiene and cosmetic products
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-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 (e.g. paper, plastic, or food waste) discarded by people on the ground, and that are washed by rainfall into storm drains and eventually discharged into surface waters
Nurdles, small ubiquitous waterborne plastic pellets
Shipwrecks, large derelict ships.
D:\lpu assignment\physics term paper\Water_pollution_files\220px-Unit_3_-_Potrero_Power_Plant.jpg
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngPotrero Generating Station discharges heated water into San Francisco Bay.[18]
Thermal pollution
Thermal pollution is the rise or fall in the temperature of a natural body of water caused by human influence. 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
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.
D:\lpu assignment\physics term paper\Water_pollution_files\130px-AngleseyCopperStream.jpg
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngA 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
Control of water pollution
Domestic sewage
D:\lpu assignment\physics term paper\Water_pollution_files\220px-Deer_Island_MA.JPG
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngDeer Island Waste Water Treatment Plant serving Boston, Massachusetts and vicinity.
Domestic sewage is 99.9% pure water, the other 0.1% are pollutants. While found in low concentrations, these pollutants pose risk on a large scale.[20] 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.[21]
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[22]
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
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D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngDissolved 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.[23]
Agricultural wastewater
D:\lpu assignment\physics term paper\Water_pollution_files\150px-Riparian_buffer_on_Bear_Creek_in_Story_County_Iowa.JPG
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngRiparian 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.
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. Farmers can develop and implement nutrient management plans to reduce excess application of nutrients.
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.
D:\lpu assignment\physics term paper\Water_pollution_files\220px-Confined-animal-feeding-operation.jpg
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngConfined Animal Feeding Operation 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 confined animal feeding operations in the U.S. and are being subject to increasing government regulation.[27][28] Animal slurries are usually treated by containment in lagoons before disposal by spray or trickle application to grassland. Constructed wetlands are sometimes used to facilitate treatment of animal wastes, as are anaerobic lagoons. 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
D:\lpu assignment\physics term paper\Water_pollution_files\220px-Silt_fence_EPA.jpg
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngSilt 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.[29]
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.[30]
Urban runoff (stormwater)
D:\lpu assignment\physics term paper\Water_pollution_files\220px-Trounce_Pond.jpg
D:\lpu assignment\physics term paper\Water_pollution_files\magnify-clip.pngRetention 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.[31]
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).[32] Runoff mitigation systems include infiltration basins, bioretention systems, constructed wetlands, retention basins and similar devices.[33][34]
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.
How can I prevent water pollution?
When we throw something in the garbage, or flush the toilet, we tend to forget about it. Because individuals are responsible for many non-point sources of pollution, we do not always realize how much we are contributing to water pollution. It seems easier to point the finger at agricultural, industrial, and mining operations. However, here are a few tips:
ô€‚ƒï€ Conserve water; the less water you use, the less will be running down the drains and into gutters, carrying pollutants with it. For more information about water consumption, as well as some tips on how to conserve water, see the Water Consumption fact sheet.
ô€‚ƒï€ Keep pet litter and debris out of street gutters.
ô€‚ƒï€ Use pesticides sparingly; in general, people tend to use 10 to 50 times more fertilizer on their lawns and gardens than is necessary for good plant health.
ô€‚ƒï€ Or, use compost to fertilize your garden.
ô€‚ƒï€ Keep your vehicles running properly. If you have an oil leak, fix it immediately, and if you change your own oil, dispose of the used oil properly.
ô€‚ƒï€ Use natural cleaners, such as baking soda, vinegar and borax.
ô€‚ƒï€ Use detergents with less phosphate; sewage plants can only remove about 30 percent of the phosphates from waste. It is estimated that, in the United States, between 90.7 million and 226.8 million kilograms of phosphates are added into waterways each year.
The Safe Drinking Water Foundation has educational programs that can supplement the information found in this fact sheet. Operation Water Drop looks at the chemical contaminants that are found in water; it is designed for a science class. Operation Water Flow looks at how water is used, where it comes from and how much it costs; it has lessons that are designed for Social Studies, Math, Biology, Chemistry and Science classes.
