Sister Bay WWTP - Municipal Wastewater Treatment in Sister Bay, Wisconsin

Sister Bay WWTP is a municipal wastewater treatment facility located in Sister Bay, Door County, Wisconsin, United States. It serves a population of approximately 4,543 people, placing it in the small-to-medium agglomeration category. The plant is situated near the Sister Bay Marina on State Highway 42, within the scenic Door Peninsula. As a US facility, the plant operates under the Clean Water Act, with National Pollutant Discharge Elimination System (NPDES) permits issued by the Wisconsin Department of Natural Resources. The designed capacity is 1.00 million gallons per day, indicating a facility scaled to handle the seasonal population fluctuations common in this tourist area. The plant's treated effluent is discharged into the waters of Door County, which ultimately flow into Lake Michigan, one of the largest freshwater lakes in the world. Lake Michigan supports diverse aquatic life and provides drinking water for millions. The plant plays a key role in protecting the lake's water quality, particularly in the ecologically sensitive Green Bay region, which is known for its fisheries and migratory bird habitats.

The plant discharges into local waters that drain into Lake Michigan via the Green Bay ecosystem. Lake Michigan is a critical freshwater resource supporting diverse fish species, including lake trout and whitefish, and serves as a major migratory corridor for birds. The Door County shoreline is ecologically sensitive, with coastal wetlands and limestone bluffs that require careful nutrient management to prevent algal blooms and maintain water clarity.