US wastewater treatment plant directory
12,584 publicly owned treatment works treating 19,834 MGD for about 143,113,630 residents, including 5,264 lagoon systems. Flow, NPDES permits, treatment technology and three-year compliance for each, built from public EPA data and enriched by Klarifi.
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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.
Data refreshed October 26, 2026.
Wastewater terms: WWTP · POTW · MGD · NPDES permit · Tertiary treatment · Significant industrial user · all terms