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I <br /> 316 PETNIEl1M CONTAMINATED SOILS <br /> ESTIMATES FOR HYDROCARBON VAPOR EMISS?ONS 31, <br /> (ppin al ) 1// le Emisslons front Groundwater Pump & Treat Operabons ' <br /> too15 3 153 1ST a 15300 133(x}0 and Free Liquid Product Recavery <br /> Equations 3,4,and 21 predict conservative errussron rate estimates fair ground <br /> J water and free-liquid product pumping systems that use injector (air drsplaa <br /> ment)pumps Calculations were performed for three different cases (a)p. IT pui� <br /> gasoline saturated groundwater with a bervcnc oQncentratron of 1$ m urlrbr i <br /> urn value for groundwater to contact with gasoline containin 0 Opp e f <br /> 10 g i mole frartu+n <br /> benzene),(b)pumping gasoline-contaminated groundwater uilh a more realistic <br /> Ernisslon VPs' benzene level of i ppm,and(c)pumping free-liquid product gasoline contain <br /> N. stC�r g containing <br /> Rale ,t, , 1 mole percent benzene At sen�icc stations,groundwater pumping rates are gcner <br /> ft/d) 0'c ,,`���,f� all} on the aider of 76 Umin(20 gallmin).and average free-liquid product p+a+ip <br /> t � ,��`' ing rates might be 0 01 gal/nein(860 gal over a two-rn011111 period) The resulls <br /> ti��otc+sNN for these pumping rates, and a 6 m (20 ft)depth to the water table aie <br /> (a) gaso/'Me-saturated groundwater. -20 <br /> gi Spm <br /> r +�° gn,m,v=560 gid C, =3 2 x 10-1, g/cm3 <br /> (b) 1 pEmi benzene tit grourrdniater, Qf20 g/irn <br /> 32 gid C'= 1 S x 10-1 g/crri; <br /> 01 <br /> (c) fiee-trilwd gasoline pttinping, Qf=0 01 gpin <br /> {'; (berizeiie, x,=(}0 l,2{}'C`) Fi„,,,,i,=0 26 g/d V,=3 2x 10 h glcm, <br /> 001 ]1/ 1f EMISSIOnS etre to Aboveground Water Tteatrrlenr <br /> Aboveground water treatment systems may be composed of carbou beds, <br /> of I f t0 ICED hiotrealers,or air-sinppers Of these optigns, a carbon-bed t}stem ►til!produce <br /> Tl) Vapor Coucenlralton (rngll) the lowest vapor emissions,because discharge wafer must meet a rrunimuni Ovate+ <br /> quality standard, which is often =1 ppb benzene Even if all the benzene voldlt <br /> (PPMCH4 -conoentralran Ln rnediane eque"alent ppm(sol/vol)um is 117-cs from the water as It leaves the carbon beds,the emission rate for a 76 Limier <br /> Figure 1 I Sod venting emissions estimates <br /> (20 gallium) operation with effluent water containing 1 ppb henzene calculated <br /> fi o'll Equation 22 is <br /> i <br /> C�max <br /> 84 gid (if untreated vapors are emitted) �'mt.."=0 1 gid 1 8 x 10-10 glcm, <br /> 7 he maximum benzene vapor emission rate for the aboveground treat xiii sys- <br /> gns=4 7 gid (for a vapor treatment efficiency >l W 0 9S) fears comes from an air-stripper(with no subsequent vapor treatment) Equatititi <br /> Mote that these numbersare several orders of inagnnude less than the conserva- 22 predicts the emission rates for a 1009 efficient air-stripper E=missions <br /> live estimates predicted by Equation 17 predluions for a wide range of flowra(es and concentrations appear rn p+gurL <br /> 12a The I-elattonsbtp between air flowrale, water flowrate,and theefYiuent valior 1 <br />