Corrective factors applied to reduced sulfur compounds in wastewater foul air

To determine accurately odorant concentrations at its worst-case condition for planning and odor treatment design purposes, corrective factors need to be factored into the foul air monitoring results of water resource recovery facilities. These corrective factors will adjust each odorant concentration for usual seasonal and daily odor variations. Typically, corrective factors are taken from hydrogen sulfide continuous readings and applied to all identified sulfur odorants. This paper demonstrates that it is incorrect to assume all reduced sulfur compounds mimic the daily fluctuations observed in hydrogen sulfide. Reduced sulfur odorant results from the foul air tested at two different water resource recovery facility process areas over a portion of the daily cycle have been found to behave independently from hydrogen sulfide. Tests have shown that the corrective factors for each reduced sulfur odorant vary notably from facility to facility and enormously from process area to process area. This discovery is important for the improvement of the science of odor control because accurately determining worst-case odor concentrations affects the modeling (the magnitude of odor nuisance) and the level of treatment (choosing a technology or combination of technologies) needed for odor abatement. PRACTITIONER POINTS: When conducting foul air assessments, corrective factors are recommended to adjust the results for daily and seasonal variations. H₂ S continuous monitors are readily available and of widespread use, therefore they are certainly useful to determine corrective factors. H₂ S continuous monitors, however useful for H₂ S, do not necessarily apply to the rest of the reduced sulfur compounds. Intermittent sampling and analysis for reduced sulfur compounds at each facility process location over a daily cycle should be conducted. Results will show the independence of each reduced sulfur compound and the importance of this testing to obtain corrective factors applicable to the facility being assessed.