Monmouth City of Wastewater Treatment Plant - Monmouth, Illinois

The Monmouth City of wastewater treatment plant is located in Monmouth, Illinois, a city in Warren County. Serving a population of about 9,444 people, the facility is part of the municipal infrastructure that manages wastewater for this Midwestern community. As an inland plant, it discharges treated effluent into local waterways that ultimately drain toward the Mississippi River system. Under the U.S. Clean Water Act, wastewater treatment plants of this scale are typically required to meet secondary treatment standards through National Pollutant Discharge Elimination System (NPDES) permits issued by the Illinois Environmental Protection Agency. These permits set limits on pollutants such as biochemical oxygen demand and total suspended solids to protect water quality. The plant's treatment processes are designed to comply with these federal and state regulations. The treated effluent from the Monmouth plant flows into receiving waters within the Mississippi River basin, which supports diverse aquatic life and provides drinking water for downstream communities. The plant plays a key role in maintaining water quality in the region, preventing untreated sewage from entering local streams and rivers that are part of the larger Mississippi watershed.

The Monmouth plant discharges into the Mississippi River basin, a major watershed that drains much of the central United States. The receiving waters support a variety of fish and wildlife, including species that rely on clean water for spawning and migration. Downstream, the Mississippi River flows into the Gulf of Mexico, where nutrient pollution from upstream sources can contribute to hypoxic zones. The plant's treatment helps reduce the local nutrient load, protecting both regional aquatic ecosystems and the broader Gulf environment.