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Y ODOR CONTROL STUDY • 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 . • Total construction and engineering costs for the above improvements are estimated to be approximately $270 , 000 . Additional operating costs are estimated to be between $ 30 , 000 and $45 , 000 per year. • Since the RSF dewaters about 13 , 000 wet tons of septage and sludge per year, these conservatively estimated costs equate to approximately $4 . 50 to $ 5 . 75 per wet ton of sludge . Based on our experience , these costs probably represent less than a 10 % increase in sludge dewatering and disposal costs ; and are relatively minor compared to costs to relocate the RSF or employ an alternative sludge disposal technology. • Construct and operate and new sodium hypochlorite storage and feed system if the existing chlorine generation facility is found to be inadequate upon further review, or if the new system is desired by the County. Construction and engineering costs for a new sodium hypochlorite system are estimated to be approximately $ 130, 000 . 8 .2 Anoxic Tank Improvements • Construct and operate an activated sludge internal recycle system to allow improved biological oxidation of odorous compounds in the Anoxic Tank . • Construct aluminum or fiberglass covers over the Anoxic Tank and collect odorous air from the headspace under the covers . • Construct and operate a modular biofilter for controlling the odorous emissions from the Anoxic Tank. • Total construction and engineering costs for the above improvements are estimated to be approximately $ 520 , 000 . 8 . 3 Sludge and Septage Storage Tanks Improvements • Add a permanent drain for the mechanical thickener so that all hatches and covers can remain closed . • Open the dampers on the Sludge and Septage Storage Tanks so that the headspace in the tanks can be ventilated more effectively. M'' 30 Indian River County, Central Wastewater Treatment Facility PBSW #071230, February 2003