Midway Sewer District WWTP - Des Moines, Washington Wastewater Treatment

Midway Sewer District WWTP is a municipal wastewater treatment facility located in Des Moines, Washington, within King County. It serves a population of roughly 43,616 people, classifying it as a medium-sized agglomeration under U.S. regulatory frameworks. The plant is situated near the Puget Sound, a major estuarine system connected to the Pacific Ocean. As a U.S. facility, the plant operates under the Clean Water Act and is subject to National Pollutant Discharge Elimination System (NPDES) permits issued by the Washington State Department of Ecology. For a plant of this scale, secondary treatment is typically required, and the designed capacity is 1.00 million gallons per day. The regulatory framework ensures that effluent meets water quality standards to protect the receiving environment. The plant's treated effluent is discharged into the Puget Sound watershed, which ultimately drains into the Pacific Ocean. The Puget Sound is an ecologically sensitive estuary that supports diverse marine life, including salmon, orcas, and shellfish. Proper wastewater treatment is critical to maintaining water quality and ecosystem health in this region.

The plant discharges into the Puget Sound, a large estuarine system connected to the Pacific Ocean via the Strait of Juan de Fuca. The Puget Sound watershed supports critical habitats for salmon, orcas, and shellfish, making nutrient and pollutant control essential. The plant's location within 50 km of the coast underscores the importance of advanced treatment to protect marine ecosystems from eutrophication and toxic contaminants.