Wastewater treatment plants by technology
11,783 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.
5,827 plants in 48 states · 4,269 MGD · 12 planning upgrades
3,818 plants in 50 states · 11,371 MGD · 2 planning upgrades
1,496 plants in 48 states · 1,926 MGD
1,571 plants in 49 states · 8,410 MGD · 2 planning upgrades
417 plants in 17 states · 441 MGD · 89 planning upgrades
333 plants in 18 states · 845 MGD · 5 planning upgrades
102 plants in 11 states · 180 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 September 11, 2026.