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ODOR CONTROL STUDY 2 . 3 Findings And Observations From Sampling Program Over 50 samples were taken at 10 selected wastewater and sludge treatment facility locations . Figures 2 through 5 graphically present the results of the sampling program . Provided below are the significant findings and observations , followed by relevant discussions . 2 . 3 . 1 Olfactory Measurements Olfactory measurements showed the existing RSF scrubber was by far the highest source of odor emissions . Odor emissions from this source were-more than 5 orders-of- magnitude higher than any other source . Figure 2 shows that the Anoxic Tank and the Sludge and Septage Storage Tanks are the next highest source of odorous emissions , as measured by olfactory methods . The Filtrate Sump was the fourth highest source . 2 . 3 .2 Sulfur Emissions Figures 3 through 5 show trends for emissions of sulfur compounds that are similar to trends for olfactory measurements . Mass sulfur flow rates were calculated for the scrubber inlets and the combined sludge storage duct. These flow rates do not represent emissions . The mass sulfur flow rates were developed in order to quantitatively , assess the sources of sulfur. flowing to the existing RSF scrubbers . The importance of the sulfur flow rate is discussed later. Odor concentrations were compared to sulfur concentrations to determine if there was correlation . This comparison is shown on Figure 6 . As can be seen , odor and sulfur emissions correlate well . Since sulfur appears to be the chemical basis of the odor emissions at the Central WWTF , all other analyses in this report will reference mass emissions of sulfur compounds . As indicated above , a Jerome H2S analyzer, colorimetric tubes , and GUMS were used to measure H2S and organic sulfur . compounds . The results of these three measurements are shown on Figures 2 through 5 . Generally, there is good correlation between the GUMS , Jerome , and colorimetric tube readings , as illustrated in Figure 7 . However, in all cases , the mass emission rate calculated from the GC/MS data is significantly lower than the Jerome or colorimetric tube data . The GC/MS measures only organic sulfur compounds , such as dimethyl sulfide , dimethyl disulfide , and various mercaptans . Because hydrogen sulfide has a low molecular weight, it is not measured by the GC/MS . The lower GC/MS readings indicate that the majority of odorous emissions from the Central WWTF are H2S . However, the importance of organic sulfur emissions cannot be underestimated . They are very odorous and require different treatment technologies than H2S . Figures 3 and 5 show that the RSF scrubber exhaust contains the highest sulfur emissions . It is not coincidental that this scrubber is also the highest odor source . Figures 3 and 5 also show that the scrubber only removes approximately 40 to 50 % of the sulfur that enters PM16 9 Indian River County, Central Wastewater Treatment Facility ' PBS&J #071230, February 2003