South Prairie Area Wastewater Treatment Plant, South Prairie, Washington

The South Prairie Area wastewater treatment plant is located in South Prairie, Pierce County, Washington, serving a small population of 482 residents. The facility provides secondary treatment, a standard level for communities of this size in the United States. As a secondary treatment plant, it uses biological processes to remove organic matter and suspended solids. The plant has a designed capacity of 181.70 thousand gallons per day and currently treats an average daily flow of 143.85 thousand gallons per day, operating below its capacity. The treated effluent is discharged into the local watershed, which drains into the Puyallup River and ultimately reaches Puget Sound. This discharge supports the ecological health of the river system, which provides habitat for salmon and other aquatic species.

The plant discharges into the Puyallup River basin, a major watershed in western Washington that flows into Puget Sound. The river supports diverse aquatic life, including salmon runs, and the treatment plant helps protect water quality in this ecologically sensitive estuary. Downstream, the Puyallup River meets Commencement Bay, an important marine habitat.