Wastewater Treatment


The Wastewater Division operates within the Public Works Department and is responsible for managing all facets of wastewater treatment for the City of Pasco to meet and exceed state and federal requirements for the safe return of water to the Columbia River. The division consists of 10 staff members.

The Treatment Process

  1. Remove foreign materials in the wastewater.
  2. Primary treatment-settable solids are removed from the wastewater at the primary clarifiers.
  3. Secondary treatment includes biologically converting ammonia contained in the plant influent to nitrate.
  4. After secondary treatment the wastewater is disinfected with ultraviolet light prior to returning to the Columbia River.
  5. Solids are thickened in the primary clarifiers, transferred to the two primary and two secondary digesters.
  6. Digested biosolids are dewatered on drying beds and applied to agricultural land as a soil amendment.

Wastewater Treatment Plant Facility Plan

The City has developed a Wastewater Treatment Plant Facility Plan in conformance with current legislation and Washington Department of Ecology guidelines.  This Plan assesses the City's current and future needs for wastewater treatment and disposal to ensure compliance with effluent quality requirements.  A series of projects have been identified to address those near and long-term needs. Department of Ecology approval for this Plan was issued on August 26, 2019.

Tour the Wastewater Treatment Plant

Free tours are available of the city's Wastewater Treatment Plant. The tour is approximately two hours in length and includes a walk-through of the plant and a more detailed explanation of the plant's processes.

Advance reservations are required. Call (509) 545-3468 for more information.