Somerset STP - Advanced Wastewater Treatment in Somerset, Wisconsin

Somerset STP is an advanced wastewater treatment facility located in Somerset, Saint Croix County, Wisconsin. The plant serves a population of approximately 2,250 residents, providing tertiary-level treatment to protect local water quality. The plant operates under the U.S. Clean Water Act, which requires NPDES permits for discharges. With a designed capacity of 2,271.24 megaliters and an annual discharge volume of 946.35 megaliters, the facility is operating well below its capacity. Advanced treatment typically includes nutrient removal to meet stringent effluent limits. The treated effluent is discharged into a local waterway that drains into the St. Croix River, a tributary of the Mississippi River. The St. Croix River is a National Scenic Riverway known for its ecological significance, supporting diverse aquatic life and recreational uses.

The plant discharges into a receiving water body that flows into the St. Croix River, which is part of the Mississippi River basin. The St. Croix River is ecologically sensitive, supporting diverse fish and mussel populations. Downstream, the Mississippi River carries the effluent toward the Gulf of Mexico, where nutrient loading can contribute to hypoxic zones. Advanced treatment helps reduce nutrient inputs.