SPILLVILLE WWTP - Secondary Treatment Plant in Winneshiek County, Iowa

SPILLVILLE WWTP is a municipal wastewater treatment facility located in Winneshiek County, Iowa, United States. The plant serves a small population of 387 residents in the rural community of Spillville, providing essential sanitation services to the area. The facility employs secondary treatment, which is the standard biological treatment process required by the U.S. Clean Water Act for municipal wastewater. The plant has a designed capacity of 189.27 megaliters per year and currently treats approximately 151.42 megaliters annually, indicating operational headroom. As a small-scale plant, it is subject to state-level NPDES permitting under the Clean Water Act, which sets effluent limits to protect water quality. The treated effluent from SPILLVILLE WWTP is discharged into local waterways that ultimately drain into the Upper Mississippi River basin. The plant's location in northeastern Iowa places it within the Driftless Area, a region known for its spring-fed streams and coldwater fisheries. The receiving waters support diverse aquatic life and are important for recreational fishing and local ecosystems.

The plant discharges into tributaries of the Upper Iowa River, which flows into the Mississippi River. The Driftless Area's karst topography makes groundwater and surface waters particularly sensitive to nutrient pollution. The secondary treatment process helps reduce biochemical oxygen demand and suspended solids, protecting downstream aquatic habitats and the Mississippi River's ecological health.