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ODOR CONTROL STUDY treat the air from this source . The advantages and disadvantages of modular and custom biofilters were previously discussed . Because emissions from the Sludge and Septage Storage Tanks are likely to contain high concentrations of organic sulfides and biofilters have had problems removing organic sulfides , it is recommended that an independent biofilter not be used to treat emissions from this source . Instead , the emissions from this source should be directed to the existing RSF scrubbers and treated on a 24 hours per day, 7 days per week basis . The dampers on the existing duct system should be opened to improve ventilation and the hatches and covers should remain closed . For the scrubber option , modifications would still be required for the existing RSF scrubber to increase odor removal efficiency when operating during belt filter press operation . Total construction costs and engineering costs for these improvements are estimated to be approximately $600 , 000 . Operating costs for this mode of operation are estimated at $ 75 , 000 per year, which is about $25 , 000 more than current operating costs . 3 . 2 . 3 Consideration of Alternative Technologies Odors from sludge processing facilities contain a complex mixture of hydrogen sulfide , organic sulfides , and other organic compounds . Many technologies that may work well for removal of hydrogen sulfide , such as carbon filters , are -not appropriate for the removal of organic sulfides . Other technologies , such as ozonation , are also ineffective for removal of organic sulfides and are generally cost prohibitive to implement. Packed tower odor control scrubbers operating with a chemical oxidant, such as sodium hypochlorite , are generally recognized in the industry as best available control technology for the removal of organic sulfides . Based on the results of the odor study described herein , PBSU would recommend installation of a two-stage packed tower scrubber for the RSF even if there were currently no odor control on -site . 3 . 2 .4 Recommended Improvements Total construction and operating costs for the various RSF options are shown in Table 6 . Based on the advantages and disadvantages discussed above and the costs shown in Table 6 , the following improvements to the RSF are recommended : • Add a permanent drain for the mechanical thickener so the all hatches and covers can remain closed . • Open the dampers in the ducts on the Sludge and Septage Storage Tanks so that the headspace in the tanks can be ventilated more effectively. • Add chlorine solution and controls to the existing RSF scrubbers as described above and operate both scrubbers in series . •9 22 Indian River County, Central Wastewater Treatment Facility 11 PBS&J #071230, February 2003