Northfield STP Wastewater Treatment Plant, Northfield, Minnesota

Northfield STP is a municipal wastewater treatment facility located in Northfield, Minnesota, serving a population of around 27,579. The plant is situated in Dakota County and is part of the city's infrastructure managed by local authorities. As a US-based facility, Northfield STP operates under the Clean Water Act and is subject to National Pollutant Discharge Elimination System (NPDES) permits issued by the Minnesota Pollution Control Agency. For a population of this scale, secondary treatment is typically required, with additional nutrient removal standards in sensitive watersheds. The plant discharges treated effluent into the Cannon River, which flows into the Mississippi River near Red Wing, Minnesota. The Mississippi River is a major waterway supporting diverse aquatic life and providing drinking water for millions downstream. The plant's operations are critical for protecting water quality in this regional drainage basin.

The treated effluent from Northfield STP enters the Cannon River, a tributary of the Mississippi River. The Cannon River watershed supports diverse aquatic habitats and is used for recreation. Downstream, the Mississippi River carries water to the Gulf of Mexico, where nutrient loading can contribute to hypoxic zones. The plant's nutrient removal performance is therefore important for regional water quality.