Facing increased environmental regulations, the City of Cashmere selected RH2 to evaluate options for upgrading or replacing the City’s existing lagoon system WWTP and prepare a Facility Plan. A new WWTP was chosen as the preferred alternative and RH2 prepared preliminary and final designs. Additional services provided by RH2 include geological, permitting, bid process support, engineering support during construction, and control system integration and programming.
The treatment plant was designed for an average daily flow of 1.1 MGD and to meet the new total maximum daily limits for phosphorus discharged to the Wenatchee River. An activated sludge process configuration was utilized to achieve enhanced biological phosphorus removal. The activated sludge basin design was a modified form of the Bardenpho process and was selected with multiple anoxic and aerobic stages. The new WWTP also includes a headworks with screening and grit removal; 40-foot circular clarifiers; open channel UV disinfection; a dissolved air flotation unit for thickening; an aerobic digester; and a belt filter press for sludge handling. Construction of the WWTP was completed in the fall of 2014.
After construction, RH2 completed a preliminary design of a future tertiary treatment system at the WWTP to meet future requirements. RH2 and the City piloted the desired manufacturer’s cloth media filtration system and then our team summarized the successful results of the pilot study in the 2015 WWTP Facility Plan Amendment. We completed the final design of the proposed filtration system for direct purchase of the equipment by the City and portions of the improvements have been constructed.
Since start-up, RH2 has provided WWTP on-call services and operations support, including system process refinement, laboratory data analysis, SCADA system updates, operational troubleshooting, and permit document assistance.