Water pollution has been defined as any man made alteration of physical, chemical or biological quality of water which result in unacceptable depreciation of the utility of the environmental value of water.
The water pollution is an undesirable change in the state of water contaminated with harmful substances.
Water pollution affect all the major water bodies of the world such as lake, pond, sea, reservoirs,river and grand water bodies.
SOURCES OF WATER POLLUTION
Sources of water pollution are :
Domestic sewage is waste water generated from the house hold activities and these are allowed to discharge into nearby river and pond. Domestic sewage contain organic substance(Phosphate, Nitrate, etc.) and inorganic substances(soap, detergent, etc). High organic load and inorganic substance cause hypoxia. The high amount of sewage pollution in our river water is also reflected in the river Ganga in which more than 70%of the total pollution is contributed by the sewage.
SOIL EROSION & SEDIMENTASION
Land erosion is one of the major source of pollution in the water. The source of all sediment are soil erosion, which is due to overgrazing, deforestation, intensive agricultural practices, high rainfall etc. In india nearly 5334 million tones of soil are being eroded annually from the cultivable land and forests.
Industrial discharges generally contain organic substance, solid and mineral acids. Pulp paper, dairy and textile industries generate organic waste while industries manufacturing organic chemicals, pesticides, fertilizer, dyes and pigment, non ferrous metal, steel and toxic inorganic waste.
The important pollutants from agricultural drainage include the poisonous pesticides resedues and mineral fertilizer. Unlike industrial fluent is very difficult to contains the transport of nutrient chemical and pesticide through agriculture drainage. It is fertilizer used in the agriculture are major contributor of residual phosphate and nitrates in surface water.
OIL & DISPERSANTS
Sources of oil pollutants are accidental oil, spills, refinery operation, normal operation of oil carrying tankers, merchant and naval vessels, the disposal of oil waste materials, natural seepage of oil from under water oil reservoir, oil precipitation on the sea surface.
RADIO ACTIVE WASTE
Sources of contamination of the aquatic environment by radio active materials are :
The atmospheric testing of nuclear weapons, nuclear reactor and plant nuclear powered ship and submarine and laboratory experiment.
Waste heat is a by product of many industrial process, especially from the production of electrical energy. Water is used to cool these power station become quite hot and is charged into river and streams, whose water temperature in Rihand lake is observed after construction of thermal plant by NTPC in UP.
Mixture of commercial and house hold rubbishes such as paper, bottles, cans, old automobile, sludges produced in sewage treatment plant, spoil from the dreding of harbours are major sources of solid wastes. The disposal of there solid wastes is a difficult problem and sea disposal of this waste material is being used increasingly.
Normal rainfall is slightly acidic (Ph 5.6) due to the presence of CO2 in air which dissolve in water forming a weak carbonic acid. Burning of fuel (coal) produces SO2 and NO2 Which react with water vapour and forming acid.