GARRISON WWTP - Secondary Treatment Plant in Benton County, Iowa

GARRISON WWTP is a municipal wastewater treatment facility located in Benton County, Iowa, United States. The plant serves a small population of 371 residents, reflecting its role in a rural community. It operates under the regulatory framework of the US Clean Water Act, which requires secondary treatment for municipal discharges to protect water quality. The plant provides secondary treatment, a standard level that removes biodegradable organic matter and suspended solids. Its designed capacity is 189.27 megaliters, with an actual discharge volume of 113.56 megaliters, indicating operational headroom. As a US facility, it is subject to National Pollutant Discharge Elimination System (NPDES) permits issued by the Iowa Department of Natural Resources, which set effluent limits and monitoring requirements. The treated effluent is discharged into a local water body, likely a tributary of the Iowa River or the Cedar River, which ultimately flows to the Mississippi River. This drainage network supports diverse aquatic life and provides water for agricultural and recreational uses downstream. The plant's secondary treatment helps reduce nutrient and organic loads, contributing to the ecological health of the region's waterways.

The plant's discharge enters a local stream within the Mississippi River basin, which drains a vast agricultural and natural landscape. The receiving waters support fish populations and migratory birds, and the plant's secondary treatment helps mitigate nutrient enrichment that could otherwise contribute to hypoxia in the Gulf of Mexico. The region's watershed is part of the Upper Mississippi River system, an ecologically significant corridor.