Mackinaw Village of Wastewater Treatment Plant, Mackinaw, Illinois

The Mackinaw Village of wastewater treatment plant is located in Mackinaw, Illinois, a small community in Tazewell County. The facility serves a population of 1,621 and provides secondary treatment, a standard level for municipal plants in the United States. The plant's designed capacity is 548.88 thousand cubic meters, with an annual discharge volume of 548.89 thousand cubic meters, indicating near-full utilization. As a US facility, the plant operates under the Clean Water Act and is subject to National Pollutant Discharge Elimination System (NPDES) permits issued by the Illinois Environmental Protection Agency. Secondary treatment is the minimum requirement for municipal wastewater plants under federal regulations, ensuring removal of biodegradable organic matter and suspended solids. The plant's discharge volume aligns with its design capacity, suggesting consistent operation. The treated effluent is discharged into a local waterway, likely a tributary of the Illinois River, which flows into the Mississippi River and ultimately the Gulf of Mexico. The plant plays a key role in protecting downstream water quality in the Illinois River basin, supporting aquatic life and recreational uses. Its location inland reduces direct marine impact, but its discharge contributes to the broader watershed health.

The plant discharges into a local stream within the Illinois River basin, which drains into the Mississippi River and then the Gulf of Mexico. The Illinois River supports diverse aquatic ecosystems, including fish and migratory birds. The plant's secondary treatment helps reduce nutrient loading, which is critical for preventing hypoxia in the Gulf of Mexico.