Pasco STP Wastewater Treatment Plant, Pasco, Washington

Pasco STP is a municipal wastewater treatment plant located in Pasco, Washington, along the Columbia River basin. It serves a population of approximately 61,193 people, placing it in the medium-to-large agglomeration category for U.S. facilities. The plant is situated in an inland, arid region of eastern Washington. As a U.S. facility serving over 50,000 people, Pasco STP is subject to the Clean Water Act and operates under a National Pollutant Discharge Elimination System (NPDES) permit issued by the Washington State Department of Ecology. These permits set effluent limits for conventional pollutants, nutrients, and other parameters to protect water quality. Treatment typically includes secondary treatment as a minimum standard for municipal plants of this scale. The plant discharges treated wastewater into the Columbia River system, which flows westward to the Pacific Ocean. The Columbia River is a major ecological and economic resource, supporting salmon runs, irrigation, and hydroelectric power. Downstream, the river enters the Columbia River estuary and eventually the Pacific Ocean near Astoria, Oregon.

Pasco STP discharges into the Columbia River basin, a major river system that drains the Pacific Northwest. The Columbia River supports critical salmon and steelhead runs, which are anadromous fish species that migrate between freshwater and the ocean. The river also provides habitat for other aquatic life and is a key water source for agriculture and communities. Downstream, the river flows through the Columbia River Gorge and into the Pacific Ocean, where nutrient and pollutant loads can affect coastal ecosystems.