Wastewater treatment plants by technology
12,584 publicly owned plants · 7 technology families
Treatment technology is identified from two sources: the structures visible in aerial imagery (lagoons, clarifiers, oxidation ditches, digester silos and gas holders), which Klarifi reviews for every plant, and the unit processes each plant reports to the EPA Clean Watersheds Needs Survey. Each family links to a national page with counts by state and to a page per state listing every plant.
5,488 plants in 48 states · 4,639 MGD · 13 planning upgrades
4,183 plants in 50 states · 15,110 MGD · 3 planning upgrades
1,508 plants in 48 states · 2,454 MGD
1,583 plants in 49 states · 10,561 MGD · 1 planning upgrades
441 plants in 18 states · 615 MGD · 106 planning upgrades
446 plants in 18 states · 1,208 MGD · 7 planning upgrades
178 plants in 11 states · 348 MGD · 18 planning upgrades
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 · Biological nutrient removal · Tertiary treatment · all terms