AFTON STP Wastewater Treatment Plant, Afton, Minnesota

AFTON STP is a municipal wastewater treatment plant located in Afton, Washington County, Minnesota, serving a population of about 2,895. The facility is situated near the St. Croix River, a major tributary of the Mississippi River, and operates under the regulatory framework of the U.S. Clean Water Act. As a small-scale treatment plant, AFTON STP is subject to National Pollutant Discharge Elimination System (NPDES) permits issued by the Minnesota Pollution Control Agency. These permits set effluent limits to protect water quality, and the plant is expected to provide at least secondary treatment, which is the national standard for municipal wastewater facilities. The plant's treated effluent is discharged into the St. Croix River, which flows south to join the Mississippi River near Prescott, Wisconsin. The St. Croix River is a National Scenic Riverway and supports diverse aquatic life, including fish species such as walleye and smallmouth bass. Downstream, the Mississippi River carries the water to the Gulf of Mexico, making the plant's operations part of a larger watershed management effort.

AFTON STP discharges into the St. Croix River, a tributary of the Mississippi River, which ultimately drains into the Gulf of Mexico. The St. Croix River is ecologically sensitive, supporting diverse fish and wildlife habitats. The plant's location in a small community means its discharge volume is relatively low, but it still contributes to the overall nutrient load in the watershed, which can affect downstream water quality and aquatic ecosystems.