Washington – East Washington

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Project Description: Description of Facilities 8.5 MGD Trickling Filter Aerated Solids Contact (TF-ASC) WWTP with tertiary nitrification.

WWTP Phase I and II Improvements
KLH Engineers completed a comprehensive process alternatives analysis to address service area growth; peak wet weather flow rates and rehabilitation of the existing facility. The administrative approach to the analysis was the preparation of a series of technical documents that evaluated progressive service area growth, associated WWTP loadings and, effluent water quality criteria, and the development of a matrix of process alternatives. A series of team meetings that included WEWJA management and operational staff, the KLH technical team and an independent process consultant were held and served as a forum where data and concepts were challenged in order to develop a consensus as to the best approach.

KLH Engineers completed the design and managed the construction for the Phase I and Phase II WWTP improvements. The Phase I project increased the peak wet weather flow hydraulic capacity of the facility from 15.5 to 20.0 MGD. All flow reaching the plant is treated utilizing a unique blending concept and is mixed with pre-chlorinated final effluent to achieve NPDES limits while maximizing the capacity of the biological portion of the WWTP. The Phase II project replaced the existing RBC units with a TF-ASC biological treatment scheme, which features a trickling filter with a motorized distributor arm and gravity or power ventilation with a fine bubble aerated solids contact process.

The plant tertiary treatment unit consists of a biological nitrification tower that removes ammonia nitrogen consistently to 0.1 mg/l and which has a net reduction in the applied solids thorough endogenous biological treatment. Since its completion, the upgraded plant has met all NPDES permit effluent requirements in a service area experience rapid growth as the result of the natural gas industry.