Point source example the sewage also contains many

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POINT SOURCE EXAMPLEThe sewage also contains many diseases causing bacterias called pathogens, which are most serious water pollutants. Pathogens include bacteria and other organisms which enter water from domestic sewage and animal excreta. Human excreta contains bacteria such as Escherichia coli which cause diseases. 224
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SIRJEE CLASSES POINT SOURCE EXAMPLE2. Industrial wastesSome common types of industrial wastes polluting water are: (i)Heavy metals: These are metals such as cadmium, lead and mercury which are present in industrial or mining wastes. These metals are poisonous and can be dangerous to humans. For example, cadmium and mercury can cause kidney damage, whereas lead poisoning can cause damage to liver, intestines, brain, kidney and central nervous system. All of these metals are cumulative poisons because the body does not excrete them and their concentration builds up. 225
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SIRJEE CLASSES POINT SOURCE EXAMPLE(ii) Detergents and fertilizers: These may contain phosphates as additives. It may be noted that these do not pose any threat to the aquatic life but serve as Nutrients for plants leading to their excessive growth in ponds, Lakes and rivers. These encourage the formation of algae, which reduce the dissolved oxygen concentration of water. This process is known as eutrophication. This impedes the development of higher life forms such as fish. 226
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SIRJEE CLASSES POINT SOURCE EXAMPLE(iii) Petroleum products: Petroleum products also pollute many sources of water, e.g., major oil spills in ocean. This is because of wreckage of oil tankers in open sea or accidents of ships carrying oil in the sea. The spreading of oil in the sea is called oil spill and the thick layer of oil on the surface of sea water is called oil slick. In India, an oil spill occurred in Bombay on March 17, 1993, due to the rupture of a pipeline which damaged the ecosystem and marine life. (iv) Acid polluted water:The acid polluted water having pH less than 3 is deadly to most forms of aquatic life. 227
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SIRJEE CLASSES 2. NON-POINT SOURCE EXAMPLEWhen a source of pollution cannot be readily identified i.e, sources are scattered or diffuse they are called Non Point source of pollution. Example: run off from farm lands, construction sites, parking lots, agriculture logging, animalwaste. Non point source water pollution is difficult to regulate because it comes from the everyday activities of many different people such as applying pesticides, road constructions or building construction. 228
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SIRJEE CLASSES Causes of Water PollutionThere are several classes of common water pollutants:- 1.Disease-causing agents (pathogens):-It include bacteria, viruses, protozoa and parasitic worms that enter water from domestic sewage and untreated human and animal wastes.
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