Lagoon systems: wastewater treatment plants in Connecticut
8 plants · 15% of the state · 9 MGD combined
Klarifi identifies 8 publicly owned wastewater treatment plants with lagoon systems in Connecticut, 15% of the 54 plants in the state (9 MGD combined). The largest is Piacenti Wastewater Treatment Plant in New London at 4.66 MGD.
Lagoon systems treat wastewater in large earthen ponds over weeks of retention time, with or without mechanical aeration. They serve thousands of small towns because they are cheap to run, but they struggle with ammonia and nutrient limits, fill with sludge over decades and are the plants most often converted or upgraded when a permit is renewed.
The largest lagoons in Connecticut
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Piacenti Wastewater Treatment Plant | New London | 4.66 | CT0100382 | Apr 2027 | 8 |
| 2 | Torrington Water Pollution Control Facility | Torrington | 2.99 | CT0100579 | Oct 2025 | 0 |
| 3 | Plainfield North Water Pollution Control Facility | Plainfield | 0.35 | CT0100447 | May 2022 | 23 |
| 4 | Plainfield Village Sewage Treatment Plant | Plainfield | 0.27 | CT0100439 | Sep 2022 | 4 |
| 5 | Town Of Norfolk WPCF | Norfolk | 0.11 | CT0101231 | Sep 2025 | 7 |
| 6 | Somers WPCF | Somers | 0.11 | CT0101605 | Sep 2025 | 62 |
| 7 | Ledyard Water Pollution Control Facility | Ledyard | 0.08 | CT0101681 | Jun 2025 | 4 |
| 8 | Sharon Water Pollution Control Facility | Sharon | 0.03 | CT0101052 | Jan 2022 | 5 |
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
Lagoon systems in other states
Lagoon systems 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.