Parish V STP Wastewater Treatment Plant, Town of Parish, New York

Parish V STP is a municipal wastewater treatment plant located in the Town of Parish, Oswego County, New York. The facility serves a small population of 480 residents and operates under secondary treatment standards, which is the minimum required by the US Clean Water Act for municipal plants of this scale. The plant's designed capacity is 529.96 million gallons per year, with an actual discharge volume of 196.84 million gallons per year, indicating operational headroom. As a US facility, it is regulated under the National Pollutant Discharge Elimination System (NPDES) permit program, administered by the New York State Department of Environmental Conservation, ensuring compliance with effluent limits. The plant discharges treated wastewater into a local water body that ultimately drains into Lake Ontario, part of the Great Lakes system. This watershed supports diverse aquatic life and provides drinking water for millions. The plant's secondary treatment helps protect downstream water quality by reducing organic pollutants and suspended solids.

The treated effluent from Parish V STP flows into a tributary of the Oswego River, which empties into Lake Ontario, the easternmost Great Lake. Lake Ontario is a critical freshwater resource supporting fisheries, recreation, and municipal water supplies. The plant's location within 50 km of the coast means its discharge can influence nearshore water quality, particularly during high-flow events. Secondary treatment reduces biochemical oxygen demand and total suspended solids, mitigating eutrophication risks in the lake.