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Since 1972, the EPA has published AP-42 Compilation of Air Emission Factors (AP-42), which is a collection of EFs and process information for more than 200 air pollution source categories from a wide range of industry sectors (Technology Transfer Network, Clearinghouse for Inventories and Emission Factors; EPA). In this study, the pollutant of concern is H 2 S from various WWTP headworks, and the parameters to describe the "unit of measure" for normalization are: 1.) flow of wastewater processed by the WWTP, 2.) population served by a particular WWTP, and 3.) service area associated with the WWTP. EF is an average value obtained from a long-term observations study performed during normal operations of the polluting unit. AP-42 indicates that EF formulae, which include variable parameters such as temperature, wind velocity, and pollutant unit dimensions produce a more realistic estimate. In line with the EF guidelines established by AP-42, this study based its EF calculation methodology on variables such as: • H 2 S emissions using continuous H 2 S concentrations within the headworks' influent chamber (sampling every 5 minutes for six months); • wastewater flow received at the WWTP; • service area; and • population served. This research attempted to determine H 2 S EFs for headworks at four WWTPs based on field measurements of H 2 S emissions and other parameters. These EFs are expressed as a function of (a) wastewater flow (EF-Flow), (b) population (EF-Population), and (c) area served (EF-Area). Four Jefferson Parish WWTP headworks — East Bank (shown in Figure 2), Marrero, Harvey, and Bridge City — were chosen as the sites for this evaluation study/pilot project as all flows pass through these units, and it also has one of the highest potentials to generate H 2 S. Based on the findings of this evaluation study, researchers could modify their methodology for any future research in this area. Figure 2. East Bank WWTP headworks and air sampling location on top of the headworks unit Results Comparison Of EF Ranges Among Various WWTP Headworks: Figures 3 to 5 at right show the comparison of EF-Flow, EF-Population, and EF-Area among all four WWTPs in terms of maximum, minimum, and average EF values. It was observed that the weekly average EF-Flows calculated for Marrero and Bridge City WWTPs are 5 percent apart, whereas the average EF-Flows for Harvey and East Bank WWTP are 3 percent apart. Similarly, the weekly average EF-Populations for Marrero and Bridge City WWTP were calculated to be 32 percent apart, while the weekly average EF-Populations for Harvey and East Bank WWTP were calculated to be 72 percent apart. Finally, the weekly average EF-Areas for Marrero and Bridge City WWTP were calculated to be 22 percent apart, while Harvey and East Bank WWTP's weekly average EF-Areas were 48 percent apart. Figure 3: Comparison Of EF-Flow Among WWTPs Figure 4: Comparison Of EF-Population Among WWTPs Figure 5: Comparison Of EF-Area Among WWTPs wateronline.com ■ Water Innovations HEADWORKSANDSCREENING 19