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ODOR CONTROL STUDY 6 . 0 Improvements To Minor And Transient Sources As indicated in a previous section , a few minor and transient odor sources were discovered during the air emission sampling program . The amounts of H2S were not quantified because representative samples could not be collected . Based on observed operations , the following improvements could be made to these minor and transient sources : • The garage doors in the bar screen dumpster area can be closed if ventilation in this area is improved . Improved ventilation could be accomplished when the Anoxic Tanks are covered and ventilated . The ventilated air could be added to Anoxic Tank controls at a construction cost of approximately $ 80 , 000 . • Openings exist at slide gates and bar screens on top of the Headworks Structure could be closed with rubber gaskets . The cost for these gaskets is estimated to be less than $ 1 , 000 , assuming County personnel install the gaskets . • The existing grit removal units , dumpsters , and mechanical sludge thickener are open to the atmosphere at the Sludge Storage Tanks . Emissions from these sources are the most difficult to control because these emissions are very transient, highly odorous , and difficult to collect. Ceasing operations or enclosing these sources are the only options for controlling these emissions . Construction costs for covering these sources are estimated to be approximately $450 , 000 . • Since these costs are very high and the amount of sulfur reduction is likely very low, no improvements are recommended for these sources at this time . The addition of a local meteorological station (wind speed and direction ) is recommended for the RSF . Data and information from the local meteorological station could then be used to make decisions when not to operate these facilities . 7 . 0 Other Issues During testing of the Sludge and Septage Storage Tanks , dichlorobenzene was measured by the GC/MS in the headspace of the tanks at concentrations up to 1 , 200 ppbv ( 1 . 2 ppmv) . Significantly lower concentrations (< 100 ppbv) were measured in the RSF Scrubber outlet. There are three different forms of dichlorobenzene : 1 , 2- , 1 , 3. , and 1 ,4-dichlorobenzene . The form emitted at the Central WWTF could not be distinguished by the GC/MS . 1 ,44chlorobenzene is commonly used as a portable toilet deodorant and in moth balls . It is believed that the dichlorobenzene originates in the septage received at the plant. OSHA exposure limits for dichlorobenzene are as follows : • 1 , 24chlorobenzene : STEL — 50 ppmv PEL — 50 ppmv 1 , 34chlorobenzene : STEL — N .A . PEL — N .A. .� 28 Indian River County, Central Wastewater Treatment Facility PBSU #071230, February 2003