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r ODOR CONTROL STUDY To achieve these objectives , PBS &J used olfactory and analytical approaches to measure emissions of odors and sulfur-based compounds from most of the treatment processes at the Central WWTF . Sulfur containing compounds , such as hydrogen sulfide ( H2S ) and organic sulfides (such as mercaptans ) , are most often associated with sewage and sludge odors . Measurements of these compounds were taken directly at the treatment processes , where emissions are at their highest level of detection . Taking samples at the treatment processes increases the accuracy of the emissions estimates . Emission rates were then used to prioritize the sources . This report summarizes the results of the mass odor emission inventory and the evaluation of potential approaches for reducing odorous emissions . 2 . 0 Mass Odor Emissions Inventory A mass odor emissions inventory was developed for suspected odorous facilities at the Central WWTF . The development of mass odor emissions for each facility provides the most objective method for quantifying odorous emissions from specific facilities and assessing the potential impact of these emissions on off-site communities . Mass odor emission rates are developed by multiplying the concentration of odorous compounds at the source by an airflow rate . For point sources , such as odor control scrubbers , the mass emission rate is estimated by multiplying the concentration of odorous compounds in the discharge stack by the flow rate of the blower. Scrubbers often have low concentrations of odorous compounds , but they typically have high air flow rates . Thus , scrubbers can have high mass emission rates and create far more odor problems than sources with high concentrations of odorous compounds and low air flow rates . Wastewater and sludge treatment facilities often contain odorous sources that have little or no air flow rates . These facilities are called area sources , which typically consist of tanks filled with liquids and/or solids . Flux chambers have been specifically designed to measure mass emission rates from area sources . Flux chambers convert area sources to point sources by using motive air to sweep across the surface of the area source and discharge the sweep air through an exit port . In general , the flux chamber is a continuous stirred reactor, wherein the gas phase compounds are in dynamic equilibrium with the liquid phase compounds . Thus , the flux camber captures 1-12S2S and other compounds as they are emitted from the liquid surface to the gas inside the flux chamber. Flux chambers were first developed for measuring emissions from hazardous materials landfills . As such , the United States Environmental Protection Agency ( USEPA) has validated the accuracy and adaptability of flux chambers . Since the sweep airflow rate is known and the concentration of the odorant is measured at the exit port, a flux rate (in terms of pounds/day/ft2) is calculated for the quiescent portion of a liquid process . In order to develop a mass odor emission inventory for the Central WWTF , odor emissions from numerous facilities were measured on October 9 and 10 , 2002 . Mal 2 Indian River County, Central Wastewater Treatment Facility PBS&J #071230, February 2003