New Lower Meramec Wastewater Treatment Plant, Saint Louis County, Missouri

The New Lower Meramec Wastewater Treatment Plant (WWTP) is a municipal facility located in Saint Louis County, Missouri, United States. It serves an estimated population of 63,992 residents, placing it in the medium-to-large agglomeration category under U.S. regulatory frameworks. As a U.S. wastewater facility, the plant operates under the Clean Water Act and is subject to National Pollutant Discharge Elimination System (NPDES) permits issued by the Missouri Department of Natural Resources. For a plant of this scale, secondary treatment is the minimum standard, with potential nutrient removal requirements depending on the receiving water body's sensitivity. The plant's treated effluent is discharged into the Meramec River, which flows approximately 150 miles to join the Mississippi River near St. Louis. The Meramec River supports diverse aquatic life and is a popular recreational waterway. The Mississippi River then carries the water to the Gulf of Mexico, contributing to the vast Mississippi River Basin ecosystem.

The New Lower Meramec WWTP discharges into the Meramec River, a major tributary of the Mississippi River. The Meramec River watershed supports diverse aquatic species and is an important recreational resource for the region. Downstream, the Mississippi River carries the effluent to the Gulf of Mexico, where nutrient loads can contribute to hypoxic zones. The plant's discharge quality is therefore critical for both local river health and downstream marine environments.