ARLINGTON STP Wastewater Treatment Plant, Arlington, Oregon

ARLINGTON STP is a municipal wastewater treatment facility located in Arlington, Oregon, a small community in Gilliam County. The plant serves a population of approximately 610 residents, reflecting the rural character of the area. It is situated near the Columbia River, which is the primary water body in the region. The plant provides secondary treatment, a standard level of purification that removes biodegradable organic matter and suspended solids. With a designed capacity of 567.81 megaliters and an annual discharge volume of 189.27 megaliters, the facility operates well below its capacity. Under the U.S. Clean Water Act, such plants are regulated through National Pollutant Discharge Elimination System (NPDES) permits, which set effluent limits to protect water quality. The treated effluent is discharged into the local watershed, which ultimately drains into the Columbia River. The Columbia River is a major ecological and economic artery, supporting diverse aquatic life, including salmon runs, and providing water for irrigation and recreation. The plant's operations are critical to maintaining the health of this downstream environment.

The plant discharges into the Columbia River basin, which flows into the Pacific Ocean. The Columbia River supports a rich ecosystem, including migratory fish species such as salmon and steelhead. The river's water quality is vital for both ecological health and human uses, including drinking water and agriculture. The plant's secondary treatment helps reduce nutrient and pollutant loads, protecting downstream habitats.