An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

National Pollutant Discharge Elimination System (NPDES)

Status of Nutrient Requirements for NPDES-Permitted Facilities

Discharges from municipal wastewater treatment facilities with little to no treatment for nitrogen and phosphorus are a significant source of these nutrients to surface waters throughout the country. Setting permit limits and treating the wastewater to meet specific effluent limits can substantially reduce nitrogen and phosphorus loading from these facilities, protecting local and downstream water quality as a result. The data in this indicator represent major (≥1 million gallons/day (MGD)) and non-major ("minor," <1 MGD) municipal wastewater treatment facilities with individual National Pollutant Discharge Elimination System (NPDES) permits.

Presented by state or territory of the U.S. are the counts and percentages of such facilities that have permit limits1 or monitoring requirements only, for any nutrient pollution parameter. Please refer to the data protocol document, "Nutrient Data Compilation and Analysis Outline," for details on how the data were generated and produced.

The data tables are based on February 2016 data from EPA's Integrated Compliance Information System (ICIS) database.