Secondary Treatment Standards
OVERVIEW
An important aspect of municipal wastewater is that it is amenable to biological treatment. The biological treatment component of a municipal treatment plant is termed secondary treatment and is usually preceded by simple settling (primary treatment). Secondary treatment standards are established by EPA for publicly owned treatment works (POTWs) and reflect the performance of secondary wastewater treatment plants. These technology-based regulations apply to all municipal wastewater treatment plants and represent the minimum level of effluent quality attainable by secondary treatment, as reflected in terms of 5-day biochemical oxygen demand (BOD5) and total suspended solids (TSS) removal.
The secondary treatment standards also provide for special considerations regarding combined sewers, industrial wastes, waste stabilization ponds, and less concentrated influent wastewater for combined and separate sewers. In addition, the secondary treatment standards also provide alternative standards established on a case-by-case basis for treatment facilities considered equivalent to secondary treatment (trickling filters and waste stabilization ponds).
WHAT CAN I FIND UNDER THIS TOPIC?
More detailed information related to secondary treatment standards can be found in the following publications:
U.S. EPA NPDES Permit Writer's Manual [PDF Format] - Chapter 5, Section 5.2, provides information related to application of secondary treatment standards for municipal discharges.
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