Central City STP - Centralia, Illinois Wastewater Treatment Plant

Central City STP is a municipal wastewater treatment plant located in Centralia, Marion County, Illinois, serving a population of about 2,529. The plant is part of the region's infrastructure managed under the US Clean Water Act and state-level permits issued by the Illinois Environmental Protection Agency. As a small-scale facility, Central City STP is subject to secondary treatment standards under the National Pollutant Discharge Elimination System (NPDES). Plants of this size typically employ biological treatment followed by disinfection to meet effluent limits. The plant discharges treated wastewater into local waterways that drain into the Mississippi River basin, ultimately reaching the Gulf of Mexico. Its operations contribute to protecting downstream water quality in the Kaskaskia River watershed, which supports diverse aquatic life and recreational uses.

Central City STP discharges into the Kaskaskia River watershed, a tributary of the Mississippi River. The Kaskaskia River flows through southern Illinois and supports a variety of fish and wildlife, including migratory birds. The plant's effluent contributes to the overall water quality of the basin, which is important for downstream ecosystems and the Mississippi River Delta.