The 50 largest wastewater treatment plants in the United States
Ranked by average flow · 5,703 MGD combined
GLWA Water Resource Recovery Facility in Detroit, Michigan is the largest publicly owned wastewater treatment plant in the United States by reported average flow, treating about 416.18 million gallons per day. The 50 plants below together treat 5,703 MGD. New York has 11, Texas has 6, California has 5, Ohio has 4 and Illinois has 2 of them.
Flow is the average discharge reported to the EPA over the most recent monitoring period, not the plant's design capacity, so wet-weather plants and combined-sewer systems rank by what they actually treat. Population served comes from the Clean Watersheds Needs Survey 2022. Plants whose reported flow fails a plausibility check against their design capacity or population (a unit error in the source data) are left out until the record is corrected; MWRD Chicago's Stickney plant, the largest in the country by capacity, is one of them. Every plant links to its profile with permit, compliance and capital-project data. Treatment technology is shown with a free Klarifi account.
The 50 largest publicly owned wastewater treatment plants in the United States by average flow, from EPA ICIS-NPDES discharge monitoring records and the Clean Watersheds Needs Survey, via Klarifi. Refreshed on every release.
By reported average flow, GLWA Water Resource Recovery Facility in Detroit, Michigan is the largest, treating about 416.18 MGD.
Joint Water Pollution Control Plant in Carson, California serves about 3,353,576 residents according to the Clean Watersheds Needs Survey 2022.
By average daily flow in million gallons per day (MGD) as reported to the EPA in discharge monitoring reports, ranked from the most recent reporting period. Design capacity, shown alongside, is the permitted maximum.
The underlying snapshot is refreshed from EPA data on every release of klarifi.io; the refresh date is shown at the bottom of the page.
Sources and methodology
Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.
