Facilities Plan and Design Services for the Regional Water Reclamation Facility
City of Medford, Oregon

West Yost completed the Facilities Plan for the Regional Water Reclamation Facility (RWRF) in 2000 and recently updated the plan to address newly adopted Total Daily Maximum Loads (TMDLs) for temperature. The RWRF serves the urban areas of the Rogue Valley including Medford, Central Point, Phoenix, Jacksonville, Eagle Point, Talent and White City. The plan includes an assessment of the existing facility capacity, flow and load projections, and will incorporate a comprehensive energy management plan with the goal of energy self-sufficiency.

Based on the initial plan, West Yost designed numerous improvements to the RWRF, including new headworks rated for a peak flow of 120 mgd; a fine-bubble aeration system; a new secondary clarifier and return sludge pump station; a 500-horsepower high-efficiency single-stage centrifugal blower with automatic dissolved oxygen control; a replacement boiler; improvements to the disinfection system and a new outfall diffuser. All of these facilities are currently in operation. 

West Yost is now implementing an upgrade of the aeration system to provide more flexible operation including anoxic zones to control filamentous bacteria in the process. In addition, the secondary clarifiers are being rehabilitated to allow new equipment to replace the existing mechanisms, some of which are 40 years old, and to increase the return sludge pumping capacity.

TMDLs established by the DEQ, limit the thermal load that can be discharged to the Rogue River during late summer and early fall for the protection of salmon spawning. Alternatives considered included thermal load trading, storage, cooling ponds and discharge into the hyporheic zone near the river.

The secondary treatment system uses a trickling filter combined with activated sludge. The entire secondary treatment system was modeled to determine how best to meet more stringent treatment requirements. It is anticipated that the ammonia limits will be more stringent, requiring more nitrification. Alternatives considered included a second trickling filter and additional aeration capacity. The need to increase the capacity of secondary clarifier was also addressed.

Digester gas is used for cogeneration and for boiler operation. Under normal operations, the cogeneration system generates electricity and produces hot water for all plant heating requirements. West Yost completed an assessment on how to increase gas production. A subconsultant on the facilities plan team completed a comprehensive energy assessment for the plant including increasing the cogeneration capacity. The facilities plan incorporated the energy management plan.