Spring Green WWTP - Secondary Treatment Plant in Town of Spring Green, Wisconsin

Spring Green WWTP is a municipal wastewater treatment facility located on Riverside Drive in the Town of Spring Green, Sauk County, Wisconsin. The plant serves a population of approximately 3,263 residents and operates as a secondary treatment facility, meeting standard regulatory requirements for communities of this size in the United States. The plant has a designed capacity of 984.20 m³/day and currently treats an average daily flow of 810.08 m³/day, indicating operational headroom. As a US facility, it operates under the Clean Water Act's National Pollutant Discharge Elimination System (NPDES) permit program, which sets effluent limits to protect water quality. Secondary treatment typically involves biological processes to reduce organic matter and suspended solids. The treated effluent is discharged to a receiving water body within the Wisconsin River basin, which ultimately flows into the Mississippi River and then to the Gulf of Mexico. The plant plays a key role in protecting local streams and rivers from nutrient pollution, supporting aquatic life and downstream water quality in the Upper Mississippi River watershed.

The plant discharges into a tributary of the Wisconsin River, which flows southwest to join the Mississippi River near Prairie du Chien. The Mississippi River is a major ecological corridor supporting diverse fish, bird, and plant species. The region's karst topography and agricultural land use make groundwater and surface water particularly sensitive to nutrient loading, so the plant's secondary treatment helps reduce phosphorus and nitrogen inputs that could contribute to algal blooms in downstream waters.