Due to occasional complaints of odors from residential and commercial neighbors, and the projected development of adjacent vacant land, an investigation was conducted at a county wastewater treatment plant (WWTP) Utilizing a physical survey of possible odor sources, an emissions measurement study, and dispersion modeling, the site was assessed for current and future odor impacts. The main compound contributing to odors was concluded to be hydrogen sulfide (H2S). Using the EPA dispersion model Industrial Source Complex Short Term (ISCST3) and ten years of meteorological data, the H2S emissions results were analyzed to estimate potential maximum H2S concentrations, as well as the annual frequency of occurrences of H2S above certain concentrations. The chief source of odor impacts was identified as fugitive emissions from the top of the grit chamber/flow splitter building, through openings for valve stems, flow gates, and the grit removal conveyor apparatus. Another ventilation fan was added, and the H2S‐laden air from the building was routed through new biofiltration units, which were being evaluated to replace an older caustic/chlorine scrubber. Since these units operated at an extremely high H2S removal efficiency, it was concluded that biofilters would replace caustic/chlorine scrubbing on a permanent basis.

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