Prosser - WWTP Improvements

The City of Prosser Wastewater Treatment Plant (WWTP) provides treatment of municipal and industrial wastewater for the residences, businesses, public facilities, and industries within the City’s service area with an average day design capacity of 1.8 MGD. The existing WWTP consists of an influent headworks with flow metering, fine screening, and aerated grit removal systems; primary and secondary sedimentation tanks (clarifiers), trickling filter and pump station; two sequencing batch reactors (SBRs); chlorination/dechlorination tank; aerated sludge holding tank; primary and secondary anaerobic digesters; sludge dewatering (belt filter press) facility; sludge drying beds; and related process control, laboratory, maintenance, and office facilities.

This improvement project, completed in October 2016, included design and construction of a third 610,000-gallon SBR tank, including replacement of the existing SBR blowers in the existing control building; replacement of the existing 150-foot diameter trickling filter rotary distributor mechanism; construction of a sludge control building that will house a new rotary drum sludge thickener, sludge feed pumps, and digester control equipment (boiler and heat exchanger); construction of a new 260,000-gallon fixed-roof primary anaerobic digester and pipe gallery; conversion of the existing primary anaerobic digester to a secondary anaerobic digester; relocation of the existing waste gas burner; and miscellaneous site improvements. These improvements increased the plant’s average day design capacity to 2.43 MGD.

HLA provided funding acquisition assistance, design plans, specifications, estimates, bidding assistance, and construction observation and administration. 

Sources of Project Funding:

Total Project Cost:


HLA Engineering and Land Surveying

2803 River Road
Yakima, WA 98902

(509) 966-7000
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