Oxidation ditches: wastewater treatment plants in New York
28 plants · 6% of the state · 22 MGD combined
Klarifi identifies 28 publicly owned wastewater treatment plants with oxidation ditches in New York, 6% of the 467 plants in the state (22 MGD combined). The largest is Ocsd#1 - Harriman Sewage Treatment Plant in Harriman at 5.6 MGD.
Oxidation ditches are ring-shaped activated sludge reactors with long retention times, common at plants between 0.5 and 10 MGD. They are recognisable from the air by their looped channels and rely on surface aerators or brush rotors, which are frequent replacement and energy-efficiency projects.
The largest oxidation ditch plants in New York
| # | Facility | City | Avg flow (MGD) | NPDES permit | Expires | Violations (3y) |
|---|---|---|---|---|---|---|
| 1 | Ocsd#1 - Harriman Sewage Treatment Plant | Harriman | 5.6 | NYR00A935 | Mar 2028 | 48 |
| 2 | Middletown City Of Sewage Treatment Plt | Middletown | 4.84 | NY0026328 | May 2017 | 1 |
| 3 | Village Of Great Neck STP | Great Neck | 2.54 | NY0026999 | Jan 2027 | 1 |
| 4 | Suffolk Co Sd#21 Suny | Stony Brook | 1.7 | NY0206644 | Nov 2028 | 4 |
| 5 | Village Of Walden STP | Montgomery | 1.26 | NY0030490 | Jul 2031 | 133 |
| 6 | Liberty (v) WWTF | Liberty | 0.83 | NY0030074 | Aug 2030 | 4 |
| 7 | Rouses Point (v) WWTP | Rouses Point | 0.7 | NY0021831 | Jun 2021 | 2 |
| 8 | Cazenovia WWTP | Cazenovia | 0.59 | NY0028525 | Apr 2029 | 0 |
| 9 | Washingtonville (v) WWTP | Washingtonville | 0.5 | NY0023671 | Jan 2031 | 24 |
| 10 | Canajoharie (v) WWTP | Canajoharie | 0.38 | NY0023485 | Jun 2023 | 0 |
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 New York
Oxidation ditches in other states
Oxidation ditches in New York: 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: Oxidation ditch · Activated sludge · Biological nutrient removal · Ozonation · Anaerobic digester · all terms