MARENGO STL Wastewater Treatment Plant, Iowa County, Iowa

MARENGO STL is a municipal wastewater treatment plant located in Washington Township, Iowa County, Iowa, United States. The facility serves a population of about 2,535 residents, reflecting a small community scale typical of rural Iowa. The plant provides secondary treatment, which is the standard biological treatment process required under the U.S. Clean Water Act for municipal wastewater. With a designed capacity of 2,081.97 thousand gallons per day and an average discharge volume of 832.79 thousand gallons per day, the plant operates well within its capacity, indicating effective management of local wastewater flows. The treated effluent is discharged into a local waterway that ultimately drains into the Mississippi River basin, contributing to the overall water quality of the region. The plant's inland location minimizes direct marine impact, but its discharge affects local streams and rivers that support aquatic life and agricultural water use.

The plant discharges into a tributary of the Iowa River, which flows into the Mississippi River and eventually reaches the Gulf of Mexico. This watershed supports diverse aquatic habitats and is part of the larger Mississippi River basin, a critical migratory corridor for birds and fish. The plant's secondary treatment helps reduce nutrient loads, which is important for mitigating hypoxia in the Gulf of Mexico.