Biosolids Handling Facilities

General work description: Construction of new biosolids management facilities at the City of Washougal wastewater treatment plant (WWTP) which will consist of a new biological selector, aerobic digester, biosolids handling building, and addition of odor control in the existing headworks building. This work will also include decommissioning, dredging, and removing solids and liquids from the existing lagoons as well as opening of one of the berms of the lagoon. The new solids handling building setup will include a rotary drum thickener, screw press dewatering, polymer activation and dosing, aeration blowers, electrical room for control panels and Motor Control Centers, and conveyor system to biosolids storage. Other processes in the plant will include odor control in the headwork and solids handling processes, biological selector, decommissioning of the existing lagoon storage system, addition of aerobic solids digestion, WAS pump replacement, and upgrade of the existing utility water system. Two new solids handling structures are proposed for the project: an aerobic digester and a solids handling building. The new structures are to be constructed in the location of Lagoon 1, which will be fully decommissioned and filled. One new treatment structure will be constructed between the headworks and the oxidation ditches: the biological selector.