The Orange County Sanitation District Goes for High-Rate Biotowers in a Big Way

Abstract

The Orange County Sanitation District (District or OCSD) of Fountain Valley and Huntington Beach, California has experimented with pilot-scale and full-scale biotowers (also called biotrickling filters) for several years with the goal of reducing chemical consumption while providing superior odor control. Studies have evolved from the experimental stage to the design stage. Three separate major design projects are underway to treat headworks and primary odors at the District's two wastewater treatment plants, including odors from the headspaces of the influent trunklines. When operational, these odor control systems will treat in excess of 560,000 cubic feet per minute (cfm) of foul air on a continuous basis. In the proposed two-stage systems, high performance biotowers packed with polyurethane foam (PUF) media will perform the bulk of the hydrogen sulfide (H 2 S) removal allowing second-stage chemical scrubbers to be optimized to control the remaining reduced sulfur compounds (RSCs) prior to atmospheric discharge. When used in polishing modes, the chemical scrubbers will consume small fractions of the chemicals that they currently consume in single-stage applications. This treatment train was selected to support the District's long-term goal of reducing odors while minimizing chemical usage.