Wastewater Treatment Plant Odor Control Optimization

Multi-stage scrubber.

During start-up of a new sludge dewatering and lime stabilization facility, Arlington County received numerous odor complaints. Although a 40,000-cfm multi-stage scrubber system was installed with the new facility, efforts to reduce odor complaints were unsuccessful. PBS&J was retained to measure odor emissions from the solids facility, determine methods for reducing these emissions, and conduct a plant-wide odor emissions survey. The evaluations determined that the primary source of the off-site odors were organic sulfide emissions from the new multi-stage odor scrubbers. PBS&J developed improved chemical controls and tested a new gas phase chlorine monitoring system that greatly improved the performance of the existing scrubbers. In addition, PBS&J evaluated the effects of sludge conditioning processes on organic sulfide emissions. It was found that reduced sludge detention time in the clarifiers, and separate storage of primary and secondary sludges until they reached the dewatering processes, significantly reduced sulfur emissions.

PBS&J also developed a comprehensive odor management master plan for this 40-mgd urban wastewater treatment plant, resulting in the design of process improvements and new odor control facilities. One new odor control facility was required to treat odorous air from the influent and preliminary treatment facilities, and gravity thickeners. These facilities were adaptable to treating air from covered rectangular primary clarifiers. Major improvements designed to optimize the existing scrubber system installed for the solids dewatering and lime stabilization facilities. included increasing the ammonia scrubbing capacity and adding two-stage sulfide scrubbing for the full volume of foul air.