The 50 largest wastewater treatment plants in Connecticut
Ranked by average flow · 128 MGD combined · 100% of the state's reported flow
Westside Water Pollution Control Facility in Bridgeport is the largest publicly owned wastewater treatment plant in Connecticut by reported average flow, treating about 16.7 million gallons per day. The 50 plants below treat 128 MGD between them, 100% of the flow reported by all 54 plants in the state, and serve about 1,500,329 people. Every plant links to its profile with permit, technology and compliance data.
| # | Facility | City | Avg flow (MGD) | Population | NPDES permit | Expires | Technology | Violations (3y) |
|---|---|---|---|---|---|---|---|---|
| 1 | Westside Water Pollution Control Facility | Bridgeport | 16.7 | 139,728 | CT0100056 | Jun 2024 | Clarifiers | 68 |
| 2 | Stamford Water Pollution Control Facility | Stamford | 12.5 | 148,520 | CT0101087 | Dec 2023 | Clarifiers, Biogas silos | 8 |
| 3 | Norwalk WPCF | East Norwalk | 9.4 | 109,654 | CT0101249 | Mar 2026 | Clarifiers | 9 |
| 4 | Danbury Water Pollution Control Facility | Danbury | 7.8 | 54,876 | CT0100145 | Jun 2026 | Clarifiers, Biogas silos, Biogas balloons | 5 |
| 5 | Meriden Water Pollution Control Facility | Meriden | 6.49 | 61,647 | CT0100315 | Dec 2023 | Clarifiers, Biogas silos, Biogas balloons | 10 |
| 6 | Fairfield Water Pollution Control Facility | Fairfield | 5.9 | 61,949 | CT0101044 | Sep 2026 | Clarifiers | 5 |
| 7 | Greenwich WPCF | Greenwich | 5.4 | 63,514 | CT0100234 | Jul 2024 | Clarifiers, Biogas silos | 5 |
| 8 | Stratford Water Pollution Control Facility | Stratford | 5.02 | 48,887 | CT0101036 | Sep 2025 | Clarifiers | 36 |
| 9 | Hockanum River Water Pollution Control Facility | Manchester | 4.89 | 64,245 | CT0100293 | Nov 2028 | Clarifiers | 12 |
| 10 | Piacenti Wastewater Treatment Plant | New London | 4.66 | 64,095 | CT0100382 | Apr 2027 | Clarifiers, Aerated lagoons, Biogas silos | 8 |
| 11 | Milford - Housatonic WPCF | Milford | 4.5 | 42,914 | CT0101656 | Oct 2024 | Clarifiers, Biogas silos | 31 |
| 12 | Eastside Water Pollution Control Facility | Bridgeport | 4.1 | 45,555 | CT0101010 | Apr 2026 | Biogas silos | 37 |
| 13 | Southington WPCF | Southington (plantsville) | 3.67 | 43,500 | CT0100536 | Sep 2023 | Clarifiers, Biogas silos | 3 |
| 14 | Enfield Water Pollution Control Facility | Enfield | 3.01 | 42,031 | CT0100200 | Jul 2024 | Clarifiers, Biogas silos | 0 |
| 15 | Torrington Water Pollution Control Facility | Torrington | 2.99 | 40,865 | CT0100579 | Oct 2025 | Clarifiers, Uncovered lagoons | 0 |
| 16 | Killingly Water Pollution Control Fac. | Danielson | 2.95 | 21,011 | CT0101257 | Dec 2022 | Biogas balloons | 1 |
| 17 | Branford Water Pollution Control Facility | Branford | 2.9 | 28,176 | CT0100048 | Jan 2025 | Clarifiers, Carrousels / oxidation ditches, Biogas silos, Biogas balloons | 0 |
| 18 | Glastonbury Water Pollution Control Facility | Glastonbury | 2.17 | 35,054 | CT0100226 | Apr 2026 | Clarifiers, Carrousels / oxidation ditches | 9 |
| 19 | South Windsor Water Pollution Control Facility | South Windsor | 2.01 | 26,767 | CT0100510 | May 2030 | Clarifiers, Biogas silos | 5 |
| 20 | Chesire,water Pollution Control Facility | Cheshire | 1.85 | 7,997 | CT0100081 | Sep 2022 | Clarifiers, Biogas silos | 13 |
| 21 | Shelton Water Pollution Control Facility | Shelton | 1.6 | 41,474 | CT0100714 | Dec 2025 | Biogas silos | 125 |
| 22 | Simsbury Water Pollution Control Facility | Simsbury | 1.58 | 27,536 | CT0100919 | Feb 2024 | Clarifiers, Carrousels / oxidation ditches, Biogas silos | 2 |
| 23 | University Of Ct Water Pollution Control Facility | Storrs | 1.5 | 2,012 | CT0101320 | May 2023 | Clarifiers, Carrousels / oxidation ditches, Biogas silos | 4 |
| 24 | Westport WPCF | Westport | 1.46 | 27,128 | CT0100684 | Jul 2024 | Clarifiers, Carrousels / oxidation ditches, Biogas silos | 0 |
| 25 | Willimantic WPCF | Willimantic | 1.31 | 24,966 | CT0101001 | Oct 2023 | Clarifiers, Biogas silos | 0 |
| 26 | Ansonia Water Pollution Control Facility | Ansonia | 1.3 | 18,815 | CT0100013 | Nov 2022 | — | 8 |
| 27 | East Hampton Water Pollution Control Facility | East Hampton | 1.04 | 26,210 | CT0024694 | Sep 2025 | Biogas silos | 13 |
| 28 | Winsted WPCF | Winsted | 0.99 | 10,226 | CT0101222 | Oct 2021 | Clarifiers | 2 |
| 29 | Seymour WPCF | Seymour | 0.89 | 19,233 | CT0100501 | Mar 2026 | Clarifiers | 6 |
| 30 | Putnam W P C F | Putnam | 0.83 | 9,529 | CT0100960 | Aug 2022 | Clarifiers | 1 |
| 31 | Montville Water Pollution Control Facility | Montville (uncasville) | 0.75 | 18,478 | CT0100935 | Oct 2024 | Clarifiers | 59 |
| 32 | Thomaston WPCF | Thomaston | 0.7 | 7,453 | CT0100781 | Jun 2022 | Biogas silos | 1 |
| 33 | New Canaan Wastewater Treatment Plant | New Canaan | 0.55 | 20,732 | CT0101273 | Jan 2026 | Clarifiers, Carrousels / oxidation ditches | 4 |
| 34 | Stafford / WPCF | Stafford Springs | 0.5 | 12,619 | CT0101214 | Sep 2022 | Clarifiers | 2 |
| 35 | Canton WPCF | Canton | 0.49 | 13,007 | CT0100072 | Apr 2027 | Clarifiers, Biogas balloons | 2 |
| 36 | Mystic WPCF | Mystic | 0.42 | 5,341 | CT0100544 | Aug 2022 | Biogas silos, Biogas balloons | 8 |
| 37 | Plainfield North Water Pollution Control Facility | Plainfield | 0.35 | 9,541 | CT0100447 | May 2022 | Clarifiers, Aerated lagoons | 23 |
| 38 | Newtown /wpcf | Newtown | 0.3 | 3,517 | CT0101788 | Aug 2021 | Clarifiers, Carrousels / oxidation ditches | 20 |
| 39 | Beacon Falls Water Pollution Control Fac | Beacon Falls | 0.28 | 6,033 | CT0101061 | Apr 2031 | — | 5 |
| 40 | Plainfield Village Sewage Treatment Plant | Plainfield | 0.27 | 5,918 | CT0100439 | Sep 2022 | Clarifiers, Uncovered lagoons | 4 |
| 41 | Litchfield WPCF | Bantam | 0.27 | 8,944 | CT0100803 | Jun 2021 | Biogas silos | 21 |
| 42 | Portland Water Pollution Control Facility | Portland | 0.24 | 9,462 | CT0101150 | Oct 2028 | Clarifiers | 6 |
| 43 | Stonington Borough WPCF | Stonington | 0.21 | 4,406 | CT0101281 | Aug 2025 | — | 18 |
| 44 | Town Of Salisbury WPCF | Salisbury | 0.21 | 4,112 | CT0100498 | Sep 2025 | — | 13 |
| 45 | Canaan Fire District | North Canaan | 0.19 | 1,078 | CT0100064 | Aug 2024 | Clarifiers | 5 |
| 46 | Deep River Water Pollution Control Facility | Deep River | 0.18 | 4,663 | CT0101745 | Nov 2028 | — | 20 |
| 47 | Town Of Norfolk WPCF | Norfolk | 0.11 | 1,587 | CT0101231 | Sep 2025 | Uncovered lagoons | 7 |
| 48 | Somers WPCF | Somers | 0.11 | 865 | CT0101605 | Sep 2025 | Uncovered lagoons | 62 |
| 49 | Ledyard Water Pollution Control Facility | Ledyard | 0.08 | 1,509 | CT0101681 | Jun 2025 | Uncovered lagoons | 4 |
| 50 | Sprague Wastewater Treatment Plant | Baltic | 0.07 | 2,950 | CT0100978 | Aug 2021 | — | 0 |
Largest plants 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.