Anaerobic digesters and biogas: wastewater treatment plants in Connecticut
23 plants · 43% of the state · 72 MGD combined
Klarifi identifies 23 publicly owned wastewater treatment plants with anaerobic digesters and biogas in Connecticut, 43% of the 54 plants in the state (72 MGD combined). The largest is Stamford Water Pollution Control Facility in Stamford at 12.5 MGD.
Anaerobic digesters stabilise sludge in sealed heated tanks and produce biogas, visible from the air as digester silos and gas holders. Plants with digesters are typically above 5 MGD and are the buyers of mixing, heating, gas handling, cogeneration and dewatering equipment.
The largest plants with anaerobic digesters in Connecticut
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Stamford Water Pollution Control Facility | Stamford | 12.5 | CT0101087 | Dec 2023 | 8 |
| 2 | Danbury Water Pollution Control Facility | Danbury | 7.8 | CT0100145 | Jun 2026 | 5 |
| 3 | Meriden Water Pollution Control Facility | Meriden | 6.49 | CT0100315 | Dec 2023 | 10 |
| 4 | Greenwich WPCF | Greenwich | 5.4 | CT0100234 | Jul 2024 | 5 |
| 5 | Piacenti Wastewater Treatment Plant | New London | 4.66 | CT0100382 | Apr 2027 | 8 |
| 6 | Milford - Housatonic WPCF | Milford | 4.5 | CT0101656 | Oct 2024 | 31 |
| 7 | Eastside Water Pollution Control Facility | Bridgeport | 4.1 | CT0101010 | Apr 2026 | 37 |
| 8 | Southington WPCF | Southington (plantsville) | 3.67 | CT0100536 | Sep 2023 | 3 |
| 9 | Enfield Water Pollution Control Facility | Enfield | 3.01 | CT0100200 | Jul 2024 | 0 |
| 10 | Killingly Water Pollution Control Fac. | Danielson | 2.95 | CT0101257 | Dec 2022 | 1 |
| 11 | Branford Water Pollution Control Facility | Branford | 2.9 | CT0100048 | Jan 2025 | 0 |
| 12 | South Windsor Water Pollution Control Facility | South Windsor | 2.01 | CT0100510 | May 2030 | 5 |
| 13 | Chesire,water Pollution Control Facility | Cheshire | 1.85 | CT0100081 | Sep 2022 | 13 |
| 14 | Shelton Water Pollution Control Facility | Shelton | 1.6 | CT0100714 | Dec 2025 | 125 |
| 15 | Simsbury Water Pollution Control Facility | Simsbury | 1.58 | CT0100919 | Feb 2024 | 2 |
| 16 | University Of Ct Water Pollution Control Facility | Storrs | 1.5 | CT0101320 | May 2023 | 4 |
| 17 | Westport WPCF | Westport | 1.46 | CT0100684 | Jul 2024 | 0 |
| 18 | Willimantic WPCF | Willimantic | 1.31 | CT0101001 | Oct 2023 | 0 |
| 19 | East Hampton Water Pollution Control Facility | East Hampton | 1.04 | CT0024694 | Sep 2025 | 13 |
| 20 | Thomaston WPCF | Thomaston | 0.7 | CT0100781 | Jun 2022 | 1 |
| 21 | Canton WPCF | Canton | 0.49 | CT0100072 | Apr 2027 | 2 |
| 22 | Mystic WPCF | Mystic | 0.42 | CT0100544 | Aug 2022 | 8 |
| 23 | Litchfield WPCF | Bantam | 0.27 | CT0100803 | Jun 2021 | 21 |
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
Anaerobic digesters and biogas in other states
Anaerobic digesters and biogas 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.