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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. Introduction Water pollution is
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  Water pollution i s the contamination of water bodies (e.g. lakes, rivers, oceans andgroundwater). Water pollution occurs when pollutants are dischargeddirectly or indirectly into water bodies without adequate treatment toremove 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 andpopulations, but also to the natural biological communities. Introduction  Water pollution is a major global problem which requires ongoingevaluation and revision of water resource policy at all levels(international down to individual aquifers and wells). It has beensuggested that it is the leading worldwide cause of deaths and diseases,and that it accounts for the deaths of more than 14,000 people daily. Anestimated 700 million Indians have no access to a proper toilet, and1,000 Indian children die of diarrheal sickness every day.[3]Some 90% of China's cities suffer from some degree of water pollution, and nearly 500 million people lack access to safe drinking water. In addition to theacute problems of water pollution in developing countries, developedcountries continue to struggle with pollution problems as well. In themost recent national report on water quality in the United States, 45  percent of assessed stream miles, 47 percent of assessed lake acres, and32 percent of assessedbay and estuarine square miles were classified aspolluted. 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 tosupport its constituent biotic communities, such as fish. Naturalphenomena such as volcanoes, algae blooms, storms, and earthquakesalso cause major changes in water quality and the ecological status of  water. Types of Water Polution Surface water and groundwater have often been studied and managedas separate resources, although they are interrelated. Surface waterseeps 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 ontheir srcin.  Causes The specific contaminants leading to pollution in water include a widespectrum of chemicals, pathogens, and physical or sensory changes such aselevated temperature and discoloration. While many of the chemicals andsubstances 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. Highconcentrations of naturally-occurring substances can have negative impactson 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 andanthropogenic substances may causeturbidity (cloudiness) which blockslight 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'sphysical chemistry includes acidity (change in pH),electrical conductivity,temperature, and eutrophication. Eutrophication is an increase in theconcentration of chemical nutrients in an ecosystem to an extent thatincreases in the primary productivity of the ecosystem. Depending on thedegree of eutrophication, subsequent negative environmental effects such asanoxia (oxygen depletion) and severe reductions in water quality may occur,affecting fish and other animal populations.    Chemical and other contaminants 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-demandingsubstances, fats and grease    Insecticides and herbicides, a huge range of organohalides and otherchemical compounds    Petroleum hydrocarbons, including fuels (gasoline, diesel fuel, jetfuels, and fuel oil) and lubricants (motor oil), and fuel combustionbyproducts, fromstormwater runoff     Tree and bush debris from logging operations     Volatile organic compounds (VOCs), such as industrial solvents, fromimproper 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 cosmeticproducts Inorganic water pollutants include:     Acidity caused by industrial discharges (especially sulfur dioxide frompower plants)     Ammonia from food processing waste    Chemical waste as industrial by-products
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