Stillman Valley STP and Coll System - Advanced Wastewater Treatment in Illinois

Stillman Valley STP and Coll System is a municipal wastewater treatment facility located at 215 North Walnut Street in Stillman Valley, Illinois, within Ogle County. The plant serves a population of approximately 1,217 residents, reflecting a small community scale typical of rural Midwestern towns. The facility provides advanced treatment, which goes beyond secondary standards to remove nutrients and other pollutants. With a designed capacity of 757.08 units and a current discharge volume of 416.40 units, the plant operates below its maximum capacity. Under the U.S. Clean Water Act, such plants must comply with National Pollutant Discharge Elimination System (NPDES) permits issued by the Illinois Environmental Protection Agency, ensuring effluent meets water quality standards. The treated effluent is discharged into a local receiving water body, which ultimately drains into the Rock River watershed and then the Mississippi River system. This downstream pathway supports diverse aquatic life and provides water for communities and agriculture. The plant's advanced treatment helps protect these waters from nutrient pollution and other contaminants.

The plant discharges into a local stream that flows into the Rock River, a major tributary of the Mississippi River. The Rock River watershed supports diverse fish populations and provides habitat for migratory birds. Downstream, the Mississippi River is a critical ecological corridor for North America. Advanced treatment at this plant reduces nutrient loads, helping to mitigate hypoxia in the Gulf of Mexico.