Wastewater Treatment Plants in Connecticut
54 facilities · 128 MGD combined flow
Klarifi tracks 54 publicly owned wastewater treatment plants in Connecticut with a combined average flow of 128 MGD, serving about 1,518,712 residents. 27 plants treat more than 1 MGD and 2 more than 10 MGD; 8 use lagoon systems and 23 have digesters or biogas infrastructure. The largest is Westside Water Pollution Control Facility in Bridgeport at 16.7 MGD. 7 NPDES permits expire this year and 2 next year.
Every plant below links to a profile with average and design flow, treatment technology, the NPDES permit and its expiry, a three-year compliance snapshot and the capital projects planned in its city.
54 plant locations in Connecticut; dot size follows average flow.
NPDES permits and renewals in Connecticut
Every plant discharges under an NPDES permit that is renewed every five years, usually with tighter limits. The renewal year is the year a plant budgets for upgrades.
Largest wastewater treatment plants in Connecticut
| Facility | City | Avg flow (MGD) | Design (MGD) | NPDES permit | Expires | Technology | Violations (3y) |
|---|---|---|---|---|---|---|---|
| Westside Water Pollution Control Facility | Bridgeport | 16.7 | 30 | CT0100056 | Jun 2024 | Clarifiers | 68 |
| Stamford Water Pollution Control Facility | Stamford | 12.5 | 24 | CT0101087 | Dec 2023 | Clarifiers, Biogas silos | 8 |
| Norwalk WPCF | East Norwalk | 9.4 | 18 | CT0101249 | Mar 2026 | Clarifiers | 9 |
| Danbury Water Pollution Control Facility | Danbury | 7.8 | 15.5 | CT0100145 | Jun 2026 | Clarifiers, Biogas silos, Biogas balloons | 5 |
| Meriden Water Pollution Control Facility | Meriden | 6.49 | 11.6 | CT0100315 | Dec 2023 | Clarifiers, Biogas silos, Biogas balloons | 10 |
| Fairfield Water Pollution Control Facility | Fairfield | 5.9 | 9 | CT0101044 | Sep 2026 | Clarifiers | 5 |
| Greenwich WPCF | Greenwich | 5.4 | 12.5 | CT0100234 | Jul 2024 | Clarifiers, Biogas silos | 5 |
| Stratford Water Pollution Control Facility | Stratford | 5.02 | 11.5 | CT0101036 | Sep 2025 | Clarifiers | 36 |
| Hockanum River Water Pollution Control Facility | Manchester | 4.89 | 8.2 | CT0100293 | Nov 2028 | Clarifiers | 12 |
| Piacenti Wastewater Treatment Plant | New London | 4.66 | 10 | CT0100382 | Apr 2027 | Clarifiers, Aerated lagoons, Biogas silos | 8 |
| Milford - Housatonic WPCF | Milford | 4.5 | 8 | CT0101656 | Oct 2024 | Clarifiers, Biogas silos | 31 |
| Eastside Water Pollution Control Facility | Bridgeport | 4.1 | 10 | CT0101010 | Apr 2026 | Biogas silos | 37 |
| Southington WPCF | Southington (plantsville) | 3.67 | 7.4 | CT0100536 | Sep 2023 | Clarifiers, Biogas silos | 3 |
| Enfield Water Pollution Control Facility | Enfield | 3.01 | 10 | CT0100200 | Jul 2024 | Clarifiers, Biogas silos | 0 |
| Torrington Water Pollution Control Facility | Torrington | 2.99 | 7 | CT0100579 | Oct 2025 | Clarifiers, Uncovered lagoons | 0 |
| Killingly Water Pollution Control Fac. | Danielson | 2.95 | 8 | CT0101257 | Dec 2022 | Biogas balloons | 1 |
| Branford Water Pollution Control Facility | Branford | 2.9 | 4.9 | CT0100048 | Jan 2025 | Clarifiers, Carrousels / oxidation ditches, Biogas silos, Biogas balloons | 0 |
| Glastonbury Water Pollution Control Facility | Glastonbury | 2.17 | 3.64 | CT0100226 | Apr 2026 | Clarifiers, Carrousels / oxidation ditches | 9 |
| South Windsor Water Pollution Control Facility | South Windsor | 2.01 | 3.75 | CT0100510 | May 2030 | Clarifiers, Biogas silos | 5 |
| Chesire,water Pollution Control Facility | Cheshire | 1.85 | 4 | CT0100081 | Sep 2022 | Clarifiers, Biogas silos | 13 |
| Shelton Water Pollution Control Facility | Shelton | 1.6 | 2.75 | CT0100714 | Dec 2025 | Biogas silos | 125 |
| Simsbury Water Pollution Control Facility | Simsbury | 1.58 | 3.8 | CT0100919 | Feb 2024 | Clarifiers, Carrousels / oxidation ditches, Biogas silos | 2 |
| University Of Ct Water Pollution Control Facility | Storrs | 1.5 | 3 | CT0101320 | May 2023 | Clarifiers, Carrousels / oxidation ditches, Biogas silos | 4 |
| Westport WPCF | Westport | 1.46 | 2.85 | CT0100684 | Jul 2024 | Clarifiers, Carrousels / oxidation ditches, Biogas silos | 0 |
| Willimantic WPCF | Willimantic | 1.31 | 5.5 | CT0101001 | Oct 2023 | Clarifiers, Biogas silos | 0 |
Connecticut plants by treatment technology
All 54 plants in Connecticut
Wastewater treatment 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.