Activated sludge and clarifiers: wastewater treatment plants in Connecticut
35 plants · 64% of the state · 197 MGD combined
Klarifi identifies 35 publicly owned wastewater treatment plants with activated sludge and clarifiers in Connecticut, 64% of the 55 plants in the state (197 MGD combined). The largest is Hartford Water Pollution Control Facility in Hartford at 56.89 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 | Hartford Water Pollution Control Facility | Hartford | 56.89 | CTL000004 | Dec 2030 | 3 |
| 2 | Westside Water Pollution Control Facility | Bridgeport | 17.54 | CT0100056 | Jun 2024 | 65 |
| 3 | Stamford Water Pollution Control Facility | Stamford | 13.83 | CT0101087 | Dec 2023 | 11 |
| 4 | Norwalk WPCF | East Norwalk | 11.32 | CT0101249 | Mar 2026 | 13 |
| 5 | Meriden Water Pollution Control Facility | Meriden | 9.93 | CT0100315 | Dec 2023 | 10 |
| 6 | Danbury Water Pollution Control Facility | Danbury | 9.24 | CT0100145 | Jun 2026 | 5 |
| 7 | Fairfield Water Pollution Control Facility | Fairfield | 7.87 | CT0101044 | Sep 2026 | 4 |
| 8 | Stratford Water Pollution Control Facility | Stratford | 7.32 | CT0101036 | Sep 2025 | 37 |
| 9 | Piacenti Wastewater Treatment Plant | New London | 6.48 | CT0100382 | Apr 2027 | 8 |
| 10 | Greenwich WPCF | Greenwich | 6.44 | CT0100234 | Jul 2024 | 4 |
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 October 26, 2026.
Wastewater terms: Activated sludge · Biological nutrient removal · Equalization tank · Significant industrial user · WWTP · all terms