Industries use water that is obtained from the water treatment system for a variety of purpose such as for manufacturing goods, for heating, for cooling, as carrier of raw material, as carrier of waste matter, as a solvent etc.

The resulting water is then classified as waste water.

The indiscriminate discharge of these waste water streams into the environment can render soils sick, pollute the receiving bodies of water, and cause air pollution by generating obnoxious gases.

Discharge untreated waste water into the domestic sewer system makes the tasks of treating domestic sewage a very difficult and costly exercise.

To prevent any health hazards caused by discharging waste water into the environment and protect domestic sewage, the waste water must be treated before discharge.

Important contaminants of concern in waste water treatment are: suspended solids, nutrients, priority pollutants, refractory organics, heavy metals, dissolved inorganic etc.