Activated sludge and clarifiers: wastewater treatment plants in Connecticut
34 plants · 63% of the state · 114 MGD combined
Klarifi identifies 34 publicly owned wastewater treatment plants with activated sludge and clarifiers in Connecticut, 63% of the 54 plants in the state (114 MGD combined). The largest is Westside Water Pollution Control Facility in Bridgeport at 16.7 MGD.
Activated sludge is the standard mechanical process for cities: aeration basins where bacteria consume organic matter, followed by clarifiers that settle the biomass out. These plants are identified by their circular or rectangular clarifiers and by the suspended-growth process code, and they are the main market for blowers, diffusers, clarifier mechanisms and instrumentation.
The largest activated sludge plants in Connecticut
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Westside Water Pollution Control Facility | Bridgeport | 16.7 | CT0100056 | Jun 2024 | 68 |
| 2 | Stamford Water Pollution Control Facility | Stamford | 12.5 | CT0101087 | Dec 2023 | 8 |
| 3 | Norwalk WPCF | East Norwalk | 9.4 | CT0101249 | Mar 2026 | 9 |
| 4 | Danbury Water Pollution Control Facility | Danbury | 7.8 | CT0100145 | Jun 2026 | 5 |
| 5 | Meriden Water Pollution Control Facility | Meriden | 6.49 | CT0100315 | Dec 2023 | 10 |
| 6 | Fairfield Water Pollution Control Facility | Fairfield | 5.9 | CT0101044 | Sep 2026 | 5 |
| 7 | Greenwich WPCF | Greenwich | 5.4 | CT0100234 | Jul 2024 | 5 |
| 8 | Stratford Water Pollution Control Facility | Stratford | 5.02 | CT0101036 | Sep 2025 | 36 |
| 9 | Hockanum River Water Pollution Control Facility | Manchester | 4.89 | CT0100293 | Nov 2028 | 12 |
| 10 | Piacenti Wastewater Treatment Plant | New London | 4.66 | CT0100382 | Apr 2027 | 8 |
| 11 | Milford - Housatonic WPCF | Milford | 4.5 | CT0101656 | Oct 2024 | 31 |
| 12 | Southington WPCF | Southington (plantsville) | 3.67 | CT0100536 | Sep 2023 | 3 |
| 13 | Enfield Water Pollution Control Facility | Enfield | 3.01 | CT0100200 | Jul 2024 | 0 |
| 14 | Torrington Water Pollution Control Facility | Torrington | 2.99 | CT0100579 | Oct 2025 | 0 |
| 15 | Branford Water Pollution Control Facility | Branford | 2.9 | CT0100048 | Jan 2025 | 0 |
| 16 | Glastonbury Water Pollution Control Facility | Glastonbury | 2.17 | CT0100226 | Apr 2026 | 9 |
| 17 | South Windsor Water Pollution Control Facility | South Windsor | 2.01 | CT0100510 | May 2030 | 5 |
| 18 | Chesire,water Pollution Control Facility | Cheshire | 1.85 | CT0100081 | Sep 2022 | 13 |
| 19 | Simsbury Water Pollution Control Facility | Simsbury | 1.58 | CT0100919 | Feb 2024 | 2 |
| 20 | University Of Ct Water Pollution Control Facility | Storrs | 1.5 | CT0101320 | May 2023 | 4 |
| 21 | Westport WPCF | Westport | 1.46 | CT0100684 | Jul 2024 | 0 |
| 22 | Willimantic WPCF | Willimantic | 1.31 | CT0101001 | Oct 2023 | 0 |
| 23 | Winsted WPCF | Winsted | 0.99 | CT0101222 | Oct 2021 | 2 |
| 24 | Seymour WPCF | Seymour | 0.89 | CT0100501 | Mar 2026 | 6 |
| 25 | Putnam W P C F | Putnam | 0.83 | CT0100960 | Aug 2022 | 1 |
Contacts and project signals for every plant on this list
Klarifi adds verified decision-maker contacts, permit limits, discharge monitoring data and the capital projects planned in each city, filterable by technology, size and compliance record.
Other technologies in Connecticut
Activated sludge and clarifiers in other states
Activated sludge and clarifiers in Connecticut: questions
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.