Secondary treatment

Slovak term: Slovenský termín

1. Wastewater treatment step that follows primary treatment (WHO 2006).

Explanation

Involves the removal of biodegradable dissolved and colloidal organic matter using high-rate, engineered aerobic biological treatment processes (WHO 2006).

Secondary treatment is the second step in most publicly owned waste treatment systems in which bacteria consume the organic parts of the waste. It is accomplished by bringing together waste, bacteria, and oxygen in trickling filters or in the activated sludge process. This treatment removes floating and settlable solids and about 90 percent of the oxygen-demanding substances and suspended solids. Disinfection is the final stage of secondary treatment (US EPA 1989).

Example

Examples of secondary treatment include activated sludge, trickling filters, aerated lagoons and oxidation ditches (WHO 2006).

References

• US Environmental Protection Agency (1989) Glossary of Environmental Terms and Acronym List. Washington, D.C.
• WHO (2006) Guidelines for the safe use of wastewater, excreta and greywater

Links

• WHO — The Health and Environment Lexicon