Water that is used for drinking, manufacturing, farming and other purposes by residences (toilets, baths, showers, kitchens, sinks), institutions, hospitals, commercial and industrial establishments are degraded in quality as a result of the introduction of contaminating constituents. Organic wastes, suspended solids, bacteria, nitrates, and phosphates are pollutants that commonly must be removed. To make wastewater acceptable for reuse or for returning to the environment, the concentration of contaminants must be reduced to a non-harmful level, usually a standard prescribed by the Pollution Controlling & Monitoring Authorities.