St Mary SD 5 Wastewater Treatment Plant, Centerville, Louisiana

St Mary SD 5 is a municipal wastewater treatment facility located in Centerville, St. Mary Parish, Louisiana. The plant serves a population of approximately 2,400 residents and operates under the regulatory framework of the United States Clean Water Act, which requires National Pollutant Discharge Elimination System (NPDES) permits for all point source discharges. The plant provides advanced treatment, which goes beyond secondary treatment to remove additional nutrients and contaminants. With a designed capacity of 1,135.62 cubic meters per day and an actual discharge volume of 946.35 cubic meters per day, the facility operates below its maximum capacity, indicating room for future growth or seasonal variations. The treated effluent is discharged into local waterways that ultimately drain into the Gulf of Mexico via the Atchafalaya River or nearby bayous. This region is part of the Mississippi River Delta ecosystem, which supports diverse aquatic life and important fisheries. The plant's advanced treatment helps protect downstream water quality in this ecologically sensitive coastal zone.

The plant discharges into the Atchafalaya River basin, which flows into the Gulf of Mexico. This area is part of the Mississippi River Delta, a critical habitat for fish, shellfish, and migratory birds. Advanced treatment reduces nutrient loading, helping to mitigate hypoxia in the Gulf and protect local wetlands and estuaries.