PAULLINA STL Wastewater Treatment Plant, O'Brien County, Iowa

PAULLINA STL is a municipal wastewater treatment facility located in O'Brien County, Iowa, United States. The plant serves a population of approximately 1,134 residents, reflecting its role as a small-scale community treatment system in the rural Midwest. The plant operates with secondary treatment, which is the standard level required under the U.S. Clean Water Act for municipal wastewater. With a designed capacity of 870.64 units and an average daily discharge of 416.40 units, the facility operates well within its capacity, indicating reliable treatment performance. As a U.S. plant, it is subject to National Pollutant Discharge Elimination System (NPDES) permitting, which sets effluent limits to protect water quality. The treated effluent from PAULLINA STL is discharged into local waterways that ultimately drain into the Missouri River basin. This region is part of the larger Mississippi River watershed, which supports diverse aquatic ecosystems and provides water for agriculture and communities downstream. Proper treatment at this plant helps maintain the ecological health of these receiving waters.

PAULLINA STL discharges into tributaries of the Little Sioux River, which flows into the Missouri River and eventually the Mississippi River. This watershed supports agricultural drainage and provides habitat for fish and migratory birds. The plant's secondary treatment helps reduce nutrient loads that could otherwise contribute to downstream algal blooms in the Gulf of Mexico.