There are over 16,000 POTWs in the U.S., serving 75 percent of the total population.[4] The remainder of the population is served by decentralized or private septic systems. The POTWs treat 32 billion US gallons (120 gigalitres) of wastewater every day.[5] Most POTWs are required to meet national secondary treatment standards.[6][7]
^United States. Clean Water Act (CWA), Titles II and VI. 33 U.S.C. § 1281, 33 U.S.C. § 1381.
^"National Pretreatment Program". National Pollutant Discharge Elimination System (NPDES). Washington, D.C.: U.S. Environmental Protection Agency (EPA). 2019-11-05.
^Copeland, Claudia (2016-10-18). Clean Water Act: A Summary of the Law (PDF) (Report). Washington, D.C.: U.S. Congressional Research Service. pp. 4–5. RL30030.
^"Water and Wastewater Systems Sector". Critical Infrastructure Sectors. Washington, D.C.: U.S. Department of Homeland Security. 2016-01-08.
^"Basic Information about Water Security". Water Security. EPA. 2014-02-11. Archived from the original on 2015-09-06.
^CWA sec. 304(d)(1), 33 U.S.C. § 1314(d)(1) and "Secondary Treatment Regulation", Code of Federal Regulations, 40 CFR Part 133.
^"Secondary Treatment Standards". National Pollutant Discharge Elimination System. EPA. 2016-11-01.