Wastewater effluent

Wastewater treatment is a process used to convert wastewater – which is water no longer needed or suitable for its most recent use – into an effluent that can be either returned to the water cycle with minimal environmental issues or reused. The latter is called water reclamation: instead of disposing of treated wastewater it is reused for various purposes. During the treatment process, pollutants are removed or broken down. The infrastructure used for wastewater treatment is called a wastewater treatment plant (WWTP), or a sewage treatment plant in the case of municipal wastewater (households and small industries).

The treatment of wastewater belongs to the overarching field of sanitation, which also includes the management of human waste, solid waste and stormwater (drainage) management. By-products from wastewater treatment plants, such as screenings, grit and sewage sludge may also be treated in a wastewater treatment plant.

Although disposal or reuse occurs after treatment, it must be considered first. Since disposal or reuse are the objectives of wastewater treatment, disposal or reuse options are the basis for treatment decisions. Acceptable impurity concentrations may vary with the type of use or location of disposal. Transportation costs often make acceptable impurity concentrations dependent upon location of disposal, but expensive treatment requirements may encourage selection of a disposal location on the basis of impurity concentrations. Ocean disposal is subject to international treaty requirements. International treaties may also regulate disposal into rivers crossing international borders. Water bodies entirely within the jurisdiction of a single nation may be subject to regulations of multiple local governments. Acceptable impurity concentrations may vary widely among different jurisdictions for disposal of wastewater to evaporation ponds, infiltration basins, or injection wells.

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Wikipedia