WAUBAY STP - Secondary Wastewater Treatment Plant in Day County, South Dakota

WAUBAY STP is a municipal wastewater treatment facility located in Day County, South Dakota, serving a small population of 576 residents. The plant provides secondary treatment, a standard level for communities of this size under the US Clean Water Act. The plant has a designed capacity of 302.83 megaliters and currently discharges 151.42 megaliters annually, indicating it operates well within its capacity. As a US facility, it is regulated under the National Pollutant Discharge Elimination System (NPDES), which sets permit limits for effluent quality to protect receiving waters. The treated effluent is discharged into local waterways that drain into the James River basin, eventually reaching the Missouri River and the Gulf of Mexico. The plant plays a key role in protecting the region's surface water quality and supporting downstream aquatic ecosystems.

The plant discharges into local streams that flow into the James River, a tributary of the Missouri River. The Missouri River system supports diverse aquatic life and provides habitat for migratory fish species. The surrounding prairie watershed is sensitive to nutrient loading, making effective wastewater treatment critical for maintaining water quality in downstream lakes and rivers.