Plymouth SD 1 STP - Secondary Wastewater Treatment in Town of Plymouth, Wisconsin

Plymouth SD 1 STP is a municipal wastewater treatment facility located in the Town of Plymouth, Rock County, Wisconsin. The plant serves a small population of 303 residents, providing secondary treatment to meet local water quality standards. The plant operates under the U.S. Clean Water Act, which requires secondary treatment for municipal wastewater. With a designed capacity of 113.56 megaliters per year and an annual discharge volume of 75.71 megaliters, the facility is operating below its full capacity. As a small-scale plant, it is subject to National Pollutant Discharge Elimination System (NPDES) permitting, ensuring compliance with effluent limits. The treated effluent is discharged into a local water body, contributing to the Rock River watershed, which flows southward into the Mississippi River. The plant's operations help protect downstream aquatic ecosystems and maintain water quality in the region.

The plant discharges into a tributary of the Rock River, which flows through southern Wisconsin and northern Illinois before joining the Mississippi River. The Rock River watershed supports diverse aquatic life and is an important migratory corridor for fish. The plant's secondary treatment helps reduce nutrient and organic pollutant loads, protecting downstream water quality in the Mississippi River basin.