THOR LAGOON Wastewater Treatment Plant, Thor, Iowa

THOR LAGOON is a municipal wastewater treatment facility located in Thor, Humboldt County, Iowa, United States. The plant serves a small population of 174 residents, reflecting its role in a rural community. It operates as a lagoon system, a common treatment method for small agglomerations in the Midwest. The plant provides secondary treatment, which is the standard level required under the U.S. Clean Water Act for municipal wastewater. With a designed capacity of 113.56 m³/day and an average discharge volume of 75.71 m³/day, the facility operates below its design capacity, indicating adequate headroom for current demand. As a publicly owned treatment works (POTW), it is subject to National Pollutant Discharge Elimination System (NPDES) permitting, ensuring compliance with effluent limits. The treated effluent is discharged into local waterways that drain into the Des Moines River basin, ultimately reaching the Mississippi River. This connection to a major river system underscores the importance of effective treatment to protect downstream water quality and aquatic habitats in the Upper Mississippi River watershed.

The plant discharges into local streams that are part of the Des Moines River basin, which flows into the Mississippi River. This watershed supports diverse aquatic life and is an important migratory corridor for fish and birds. The region's agricultural landscape means that nutrient management is a key concern, as excess nitrogen and phosphorus can contribute to downstream hypoxia in the Gulf of Mexico.