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• • <br /> ESTIMATES FOR HYDROCARBON VAPOR EMISSIONS 30 <br /> 309 PETROLEUM CONTAMINATED SOILS <br /> uation 4 for free-liqutd entering at a flowrate, Q"P, Maximum emissions rates occur when the air <br /> I <br /> phases are rn equtland E In this case C,t is given by l q sirs in efficiencyas IDD%, and there is no vapor treatment system corineeleJI <br /> productpuinping,end Equation 2 for contaminated groundwater pumping Sold- to the air-,tripper In this case the emissions rate, C..,,r, and exit ral►cir C011CL1F' <br /> ble le>rels of hydrocatrbOns in gmundvrater are typically .in order of magnittidc tralion, C p are <br /> less than saturation,so more realistic levels (such as l ppin benzene) might also s��P, <br /> W used 1 C..16k (22 j <br /> If 2e Emissions Associated whit Aboveground Water Treatment C,Imp=Q, C,L01AI Q,i,y, <br /> Aboveground water treali mni system4 usually consiSi of carbon beds,air strip- it 2f Emissions from Burled Gasoline-Confaminaled Soils <br /> pers, or aerobic biotreaters If a carbon bed is used, emissions will be insignifi- <br /> cant because the effluent water must be cleaned to a discharge lunit (often 1 For comparison, we estimate the emissions emanating from gasoline <br /> ppb)and all coataminaut is transferred from the grodnduater to the carbon bed- contaminated soils that are left m place For the case pictured in Figure 6, wheic <br /> Biotreaters utilize air spargers to maintain high dissolved oxygen levels,and hence there is a nondinnnuhing vapor source located a distance H below ground i <br /> they produce emissions during operation Those emission levels are difficult to <br /> estimate, but at worst,they could be only as great as the emissions from an air <br /> stripper, which will be modeled in the following analysis Figure 5 presents a Wind <br /> basic air stripping operation Grouuduatei %rich a soluble hycirocaiboii level, <br /> enters the unit at a fiov:rale, Q,, and is then contacted with clean air <br /> Air Out Vapor Emissions <br /> Qstrip t,strip -- ��■ <br /> Qstrtp <br /> f *�1.soluble Air InH <br /> Groundwater In '� <br /> rf <br /> Groundwater Out , <br /> 'dap <br /> Groundwater Well Contaminfited Soil <br /> Figu-e 6 Emissions from burled contaminated soils <br /> Figure 5 Ali stripping operation <br />