GRASSTON STP - Secondary Wastewater Treatment in Comfort Township, Minnesota

GRASSTON STP is a municipal wastewater treatment plant located in Comfort Township, Kanabec County, Minnesota, United States. The plant serves a small population of 169 residents in the rural community of Grasston. It operates under the regulatory framework of the US Clean Water Act, which requires secondary treatment for municipal wastewater discharges. The plant provides secondary treatment, a standard biological process that removes organic matter and suspended solids. With a designed capacity of 143.85 units and an average daily discharge of 102.21 units, the facility operates below its capacity. As a small agglomeration, it is subject to state-level NPDES permitting administered by the Minnesota Pollution Control Agency. The treated effluent is discharged into local waterways that drain into the St. Croix River watershed, ultimately reaching the Mississippi River. The plant plays a key role in protecting downstream water quality in this ecologically sensitive region, which supports diverse aquatic life and recreational uses.

The plant's discharge enters local streams within the St. Croix River basin, a tributary of the Mississippi River. The St. Croix River is a National Scenic Riverway known for its ecological significance, supporting diverse fish populations and migratory birds. Downstream, the Mississippi River carries the flow to the Gulf of Mexico, where nutrient loading from upstream sources contributes to seasonal hypoxia. The plant's secondary treatment helps reduce organic and nutrient pollution in this interconnected watershed.