INNOVATIVE ODOR MAPPING AND MANAGEMENT METHOD SETS THE STAGE FOR TARGETTED FOUL AIR TREATMENT

The Orange County Sanitation District (OCSD) approached its Odor Control Master Plan from a different view point than usual. Cognizant that odors are caused by compounds besides hydrogen sulfide (H2S), it embarked on a wide sweep of sampling and analysis of all plant process areas to determine the top offenders at its Plant No.1 and Plant No.2 located in coastal Southern California, neighboring a densely populated sensitive residential and commercial community. As part of the characterization of the key odorants present in the various process areas of the two plants, field samples were analyzed using chemical and sensory analytical methods. Top odorants were identified based on their prevailing concentrations, sensory response, and relative intensities at each location. Once the top odorants were identified at each of the plant process areas, these were repetitively monitored to improve result precision. Results were also matched with continuous monitors and operational variables to ascertain worst-case scenario concentrations. Using the Weber-Fechner relationship between each odorant concentration and their perceived intensity, the maximum fenceline concentrations below nuisance were determined.Local worse-case air dispersion modeling using AERMOD and CALPUFF are being used in developing target odorant concentrations at each source at Plant 1 and Plant 2 for meeting maximum fenceline concentration goals. This innovative approach to odor characterization/mapping is also coupled with a thorough odorant treatment technologies assessment. A comprehensive literature search has been conducted to ascertain both practical and theoretical odorant removal efficiencies for all viable technologies. This will be followed by specific technology testing for determination of removal efficiencies and performance targets for selected technologies in their ability to reduce the identified top odorants identified at OCSD. The target source concentration for each of the top odorants identified considering both treatment performance testing and air dispersion modeling sets the design parameters for the proposed foul air treatment systems for implementation at OCSD plant processes.