OHLMAN STP Wastewater Treatment Plant, Ohlman, Illinois

OHLMAN STP is a municipal wastewater treatment facility located in Ohlman, a small community in Montgomery County, Illinois. The plant serves a population of 135 residents, reflecting its role in a rural setting. It operates under the regulatory framework of the United States Clean Water Act, which governs wastewater discharges through the National Pollutant Discharge Elimination System (NPDES) permit program. The plant provides secondary treatment, a standard level that removes biodegradable organic matter and suspended solids. With a designed capacity of 94.64 megaliters and an annual discharge volume of 68.14 megaliters, the facility operates below its capacity. This scale aligns with typical treatment expectations for small communities in Illinois, where state environmental agencies oversee compliance. The treated effluent is discharged into a local waterway that ultimately drains into the Mississippi River basin. The plant's operations help protect downstream water quality in the region's rivers and streams, which support diverse aquatic life and are used for recreation and agriculture. By maintaining secondary treatment, OHLMAN STP contributes to the ecological health of the broader watershed.

The plant discharges into a tributary of the Kaskaskia River, which flows into the Mississippi River and eventually the Gulf of Mexico. This watershed supports a mix of agricultural and natural habitats, including wetlands and forests. The plant's secondary treatment helps reduce nutrient and organic pollution, mitigating impacts on downstream ecosystems and maintaining water quality for aquatic species and human use.