Water is a vital natural resource which is essential for a multiplicity of purposes. Its many uses include drinking and other domestic uses, industrial cooling, power generation, agriculture, transportation and waste disposal. In the chemical process industry water is used as a reaction medium, a solvent, a scrubbing medium, and a heat transfer agent. Wastewaters can be classified by their origin as domestic wastewater and industrial wastewater. Wastewater is conducted to treatment plants for removing undesirable components which includes both organic and inorganic matters as well as soluble and insoluble material. The pollutants discharged directly or with improper treatment, can interfere with the self-cleaning mechanisms of water bodies. The capacity for self- cleaning is due to the presence of relatively small numbers of different types of micro- organismsin the water bodies. These micro- organisms used food much of the organic pollutants and break them down into simple compounds and the micro-organisms produce new cells also. Various constituents of wastewater are potentially harmful to the environment and to human health.

Pollutants, Micro-organisms, Cleaning Mechanisms