COLESBURG NW STL Wastewater Treatment Plant, Earlville, Iowa

COLESBURG NW STL is a municipal wastewater treatment plant located at 157 South Thomas Street in Earlville, Delaware County, Iowa. The plant serves a small population of 167 residents, reflecting the rural character of the surrounding area in the northeastern part of the state. The facility provides secondary treatment, which is the standard level required by the US Clean Water Act for municipal plants of this scale. With a designed capacity of 37.85 thousand cubic meters per year and an equal discharge volume, the plant operates within its capacity. As a US facility, it is subject to National Pollutant Discharge Elimination System (NPDES) permitting, administered by the Iowa Department of Natural Resources. The plant's treated effluent is discharged into a local water body that ultimately drains into the Mississippi River basin. The receiving waters support aquatic life and are part of the Upper Mississippi River watershed, which is ecologically significant for its diverse fish and bird populations. The plant's operations help protect downstream water quality in this agriculturally intensive region.

The plant discharges into a tributary of the Maquoketa River, which flows into the Mississippi River near Dubuque. The Mississippi River in this reach supports diverse aquatic life, including freshwater mussels and migratory fish. The watershed is predominantly agricultural, so the plant's nutrient removal helps mitigate eutrophication risks in downstream waters.