What does the term "effluent" refer to in wastewater treatment?

The term "effluent" specifically refers to treated wastewater that is discharged from a wastewater treatment facility. This water has undergone various treatment processes to remove contaminants and is typically released into a river, lake, or ocean, or it may be reused for various purposes such as irrigation or industrial processes. The significance of effluent lies in its potential impact on the environment and public health; thus, it must meet certain regulatory standards to ensure that harmful pollutants are reduced to safe levels.

Raw wastewater entering a treatment facility, known as influent, is the unprocessed water that contains a combination of sewage, industrial discharges, and stormwater runoff. Sludge refers to the by-product created during the treatment process, which is a mixture of organic solids and microorganisms. Unprocessed chemicals added for disinfection are not considered effluent, as they are added to enhance the treatment process rather than being a result of it. Therefore, the definition of effluent is distinctly tied to the quality and condition of water after it has undergone treatment.