SELFRIDGE LAGOON Wastewater Treatment Plant, Selfridge, North Dakota

SELFRIDGE LAGOON is a municipal wastewater treatment facility located in Selfridge, North Dakota, serving a small population of 160 residents. The plant provides secondary treatment, a standard level for small communities in the United States, and discharges approximately 75.71 megaliters of treated effluent annually. Its designed capacity is 113.56 megaliters, indicating operational headroom. As a U.S. facility, SELFRIDGE LAGOON operates under the Clean Water Act, which mandates National Pollutant Discharge Elimination System (NPDES) permits for all point-source discharges. Secondary treatment is the minimum requirement for municipal plants, ensuring removal of biodegradable organics and suspended solids. The plant's small scale aligns with typical lagoon-based systems common in rural North Dakota. The treated effluent from SELFRIDGE LAGOON likely drains into local waterways within the Missouri River basin, which ultimately flows to the Mississippi River and the Gulf of Mexico. The plant's inland location, over 50 km from the coast, reduces direct marine impact but contributes to the overall nutrient load in the Mississippi River watershed, a region known for seasonal hypoxia in the Gulf.

SELFRIDGE LAGOON discharges into the Missouri River watershed, which flows through the Great Plains and joins the Mississippi River before reaching the Gulf of Mexico. This basin supports diverse aquatic life and is an important migratory corridor for birds. Downstream, nutrient inputs from numerous treatment plants contribute to the Gulf of Mexico's hypoxic zone, making effective secondary treatment critical for reducing nitrogen and phosphorus loads.