Multi-Stage Gas Phase Odor Control for High Level Hydrogen Sulfide

High level hydrogen sulfide gas concentrations associated with turbulent flows in wastewater conveyance systems often result in nuisance odor impacts in surrounding neighborhoods. King County's Wastewater Treatment Division (WTD) has developed systems for controlling high levels of hydrogen sulfide and other odorous compounds based on many years of experience with full scale odor control systems and pilot testing of various odor control technologies. This paper will describe the evolution of an odor control system, based on these experiences, at a particularly turbulent location in King County's conveyance system where turbulent flow results in high concentrations of gas phase hydrogen sulfide with the potential for highly odorous neighborhood impacts.The evolution of the Sweyolocken force main discharge odor control system from a simple and undersized carbon scrubber into a bioscrubber with an activated carbon polishing stage will be described. Pilot testing of various bioscrubber technologies and how this led to the selection of a scrubbing system to completely solve odor control problems at the facility will also be explained. The reasoning behind the installation of each technology during the evolution of the system will be described in the context of the time period of their selection. Hydrogen sulfide control efficiency and overall odor control will be discussed.