PAWNEE STP Wastewater Treatment Plant, Sangamon County, Illinois

PAWNEE STP is a municipal wastewater treatment plant located on Dickey Road in Sangamon County, Illinois, serving a population of 2,647. The facility is part of the region's wastewater infrastructure, handling domestic sewage from the surrounding community. As a US-based plant serving a small population, PAWNEE STP operates under the Clean Water Act's National Pollutant Discharge Elimination System (NPDES) permit program. The Illinois Environmental Protection Agency issues permits that set effluent limits and monitoring requirements. For plants of this scale, secondary treatment is typically required to meet federal standards for biochemical oxygen demand and total suspended solids. The plant's treated effluent discharges to a local waterway within the Mississippi River basin. The receiving water body ultimately drains to the Mississippi River and then to the Gulf of Mexico. This watershed supports diverse aquatic life and is an important ecological corridor in the Midwest.

PAWNEE STP discharges into a tributary of the Sangamon River, which flows into the Illinois River and then the Mississippi River. The Mississippi River basin is a major ecological system supporting fish, migratory birds, and other wildlife. The plant's location inland, more than 50 km from the coast, means its discharge affects freshwater ecosystems rather than marine environments. Proper treatment helps protect downstream water quality and aquatic habitats.