Wastewater Treatment Plant Waters that are 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 Environmental Protection Agency. Wastewater treatment plants of a medium or small scale require a simple equipment composition and easy maintenance.