South Milwaukee STP - Wastewater Treatment in South Milwaukee, Wisconsin

South Milwaukee STP is a municipal wastewater treatment facility located in South Milwaukee, Wisconsin, serving a population of about 22,033. The plant is situated in Milwaukee County near the western shore of Lake Michigan, one of the largest freshwater lakes in the world. As a key component of the city's infrastructure, it manages wastewater from residential and commercial sources. The plant operates under the U.S. Clean Water Act, which requires National Pollutant Discharge Elimination System (NPDES) permits for all discharges. For a facility of this scale, secondary treatment is typically mandated, with additional nutrient removal requirements common in the Great Lakes region to address eutrophication concerns. The designed capacity is 1.00 million gallons per day, indicating a moderate-sized plant. Treated effluent from the plant ultimately reaches Lake Michigan, which drains via the Straits of Mackinac into Lake Huron and then the St. Lawrence River to the Atlantic Ocean. The plant plays a crucial role in protecting the lake's water quality, which supports diverse aquatic life, recreational activities, and municipal water supplies for millions of people.

The plant discharges into the Lake Michigan watershed, part of the Great Lakes system. Lake Michigan is a vital freshwater resource supporting fisheries, drinking water, and recreation. The plant's operations help control nutrient loading, particularly phosphorus and nitrogen, which can cause harmful algal blooms in the lake. Downstream, water flows through the Straits of Mackinac into Lake Huron and eventually the St. Lawrence River, impacting ecosystems across the region.