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ODOR CONTROL STUDY the scrubbers . By contrast , the Headworks scrubber appears to be removing 95 % of H2S that enters the scrubber. The low sulfur removal rate for the RSF scrubber is not surprising because the scrubber lacks controls for the dynamic sulfur loads that are delivered to the scrubber. Blowdown rates are also uncontrolled . In addition , the scrubber uses caustic soda (sodium hydroxide ) for H2S removal . Caustic soda is not effective at removing organic sulfur compounds . Organic sulfur compounds must be oxidized by chlorine . Therefore , the chemistry in the scrubber and the controls will have to be changed in order to improve the effectiveness of the RSF scrubber. 2 . 3 . 3 Regional Sludge Facility Sulfur Mass Balance A sulfur mass balance was performed for the RSF in order to assess the effectiveness of existing odor control systems to capture and treat sulfur emissions . Figure 8 shows a sulfur mass balance using Jerome measurements . All concentrations and flow rates represent actual field measurements , except the concentration and flow rate for the Dewatering Building . A proper sampling point could not be located for this point because the new hoods and covers for belt filter presses were not connected at the time of sampling . Therefore , the Dewatering Building concentration and airflow rate were calculated by assuming a closed mass balance . As can be seen in Table 5 , the calculated concentration for the Dewatering Building is nearly equivalent to the measured H2S concentrations in the ambient air within the Dewatering Building . This provides a high degree of confidence in the field measurements and the accuracy of the mass odor emissions inventory. Using this mass balance , fugitive emission rates were computed for the Sludge and Septage Storage Tanks and the overall RSF . A comparison of colorimetric sulfur emissions from the surface of the Sludge and Septage Storage Tanks to the Jerome sulfur flow rate in the combined sludge storage duct shows that approximately 75 % of the emissions from the Sludge and Septage Storage Tanks were captured and delivered to the existing scrubber. This means that 25 % of the sulfur emissions were being emitted into the atmosphere as fugitive emissions . These emissions are escaping the collection system through openings in the top of the tank. Many dampers in the odor collection system were closed during the sampling program . Thus , fugitive emissions could be reduced if the dampers were opened and openings in the tanks were closed . This estimate of fugitive emissions must be considered somewhat soft (could be significantly higher or lower) because of the dynamic nature of the facility and the difficulty in measuring fugitive air emissions . 2 . 3 . 4 Impact of . Dewatering Operations on Emissions Operators at the Central WWTF indicated that odor emissions from the plant appeared to increase when the belt filter presses were dewatering sludge . Specifically, the operators could detect higher odors at the Filtrate Equalization Basin and the liquid treatment processes . Filtrate from the belt filter presses flowed to the Filtrate Equalization Basin , where it is stored and then pumped to the liquid treatment 10 Indian River County, Central Wastewater Treatment Facility PBSW #071230, February 2003