CHEMISTRY - Water Pollution

Water is one of the basic needs of household, agriculture and industry. For most of the purposes, e.g. drinking, washing etc. We need pure and clean water. However, the natural water gets contaiminated or polluted in the following two ways :-

1. By natural processes
2. By human activity

Qater pollution is defined as the contamination of water by foreign substances which make it harmful for health of animals or plants or aquatic life and make it unfit for domestic, industrial and agricultural use.
Polluted water has any one or more of the following signs :-
* It has a bad taste to drink.
* It has an offensive odour.
* It has unpleasant colour.
* It has unchecked growth of weeds.
* It may have oil or grease floating on the surface.

Types of Water Pollution :-  Based on the sources and storage of water, water pollution may be classified into five main categories as follows :-

1. Ground Water Pollution :- Water below the surface of the earth is called ground water. Most of the water is present as ground water. The remaining presents in lakes, river, streams etc. Only about 2% is present as soil moisture above the water table which is needed for the growth of plants. Ground water collects below the surface of the earth afterpassing throughthe pores of the earthly material which act as a filter for it and is pure. It is for this reason that well water or spring water is used for domestic purposes in rural areas. However, due to disposal of domastic wastes and industrial effluent and use of fertilizers and pesticides in agriculture, a number of harmful soluble substance dissolve into the rain water and pass through tbe soil and enter into ground water and result in pollution, especially where the water table is high.

2. Surface Water Pollution :- Water present on the surface of the earth in any form is called surface water. As it is an in direct contact with the atmospheric gases, a number of gases like corbon dioxide, sulphur dioxide etc. Present in the air as pollutants dissolve into it , thereby polluting it. In addition to these atmospheric gases, the surface water also gets polluted by industrial and municipal wastes, agriculture wastes including decomposed plant and animal matter and by radioactive materials.

3. Lake Water Pollution :- Lakes cover a large part of the water area . The water in them gets contaminated in a number of way as followings :-
* Organic wastes from hills and toxic effluent from urban areas flow into them.
* Industrial effluents are thrown into them.
* Sewage treatments plants discharge toxic organic matter into them.
* Dumping of huge amounts of sediments i.e. siltation of lakes.
* Inorganic nutrients from agricultural land due to surface run-off.

4. River Water Pollution :- There are 13 major rivers in India flowing through differents states. These include Ganga, Yamuna, Narmada, Brahamputra, Krishna, Cauvery, Damodar, Godavri, Hooghly, Tapti, Gomti, Sona and Chambal besides many others. There was time when the water in these rivers was very pure and clean. Ganga jal was considered to be so pure that it could be