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h ODOR CONTROL STUDY Executive Summary Odor and sulfur emission inventories and evaluations performed in this study show that the existing Regional Sludge Facility ( RSF ) Scrubbers , Anoxic Tank , and Sludge and Septage Storage Tanks are , in order, the major sources of odorous emissions from the Central WWTF . Hydrogen sulfide ( 1-12S ) and organic sulfides are the major odorants emitted from these sources . Emission data show that the existing RSF scrubbers are not adequately removing H2S and organic sulfides . Evaluations also show that improvements to the RSF scrubbers will provide the most odorant removal . Although recent efforts to eliminate sludge dewatering filtrate and Aerobic Digester emissions have reduced total plant emissions by an estimated 25 to 33 % , air dispersion models shows that additional improvements are needed to further reduce emissions from the major sources . Air dispersion modeling also indicates that 90 % reduction of emissions from the major sources should help make the Central WWTF a Is community- friendly facility" . Several alternative improvements were evaluated for each of the major sources . Based on the advantages , disadvantages , effectiveness , and estimated costs associated with these alternatives , the following improvements ( in order of importance ) are recommended for the Central WWTF and RSF . RSF Scrubber Improvements Install automatic chlorine solution addition facilities to both scrubbers and operate the existing scrubbers in series , as a two-stage system . Install oxidation -reduction potential (ORP ) controls on both scrubbers . The ORP monitors will control the addition of chlorine solution . Add a gas phase chlorine monitor to the last scrubber to ensure adequate chlorine addition in the last stage . Operate the first scrubber with mostly caustic soda . Operate the second scrubber with mostly chlorine solution . Engineering start-up , testing , and training services should be used to help determine appropriate operating conditions . • Install a VFD on the existing blower and add a second smaller blower to the existing scrubber system . Install an automated damper on the exhaust duct from the Dewatering Building and operate the large blower at full speed during sludge dewatering . Operate the small blower at full speed or large blower at half speed when sludge is not being dewatered . The automated damper should partially close when sludge is not being dewatered so that much of the air is drawn from the Sludge and Septage Storage Tanks , I Indian River County, Central Wastewater Treatment Facility 1111 PBSU #071230, February 2003