pollution is the presence of any foreign substance (organic, inorganic,
radioactive or biological) in water which tends to degrade the quality so as to
constitute a hazard or impair the usefulness of water.
The common water pollutants are:
(i) Oxygen-demanding wastes
(ii) Disease causing agents
(iii) Synthetic organic compounds
(iv) Plant nutrients
(v) Inorganic chemicals and minerals
(vi) Suspended solids
(vii) Radioactive substances
(viii) Thermal discharges
Control of Water Pollution:
(i) Septic tanks should be used for each house. This will
reduce the flow of municipal sewage and human excreta towards river, lake or
(ii) Rivers, lakes, etc., should not be used for bathing and
washing purposes. In this way, water sources are not polluted with detergents
(iii) Too much use of pesticides which are not degradable
should be avoided. These are highly toxic substances.
(iv) Efforts should be made to increase the use of low grade
or polluted water. Treatment of domestic sewage for industrial cooling is a
good example of efficient use.
Water reuse has a special significance in mining and similar
industries where the water availability is less.
These efforts will save fresh water from being polluted.
(v) Waste water treatment techniques should be applied before
the polluted water enters a river, lake or pool.
Available waste water treatment processes can be physical,
chemical or biological. Physical processes comprise screening, sedimentation,
floatation and filtration. Commonly used chemical processes are precipitation,
coagulation and disinfection while biological processes are biological
filtration and the activated sludge process. In particular cases, the processes
such as carbon adsorption, oxidation and reduction, ion-exchange, reverse
osmosis, electrolysis, etc., are also used.
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