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Air Sparging and Groundwater.Recirculating Wells 31 <br /> verified independent decomposition. of sister compounds PCE, TCE, DCE, <br /> without conversion of one form to another (Kerfoot, 1997a, 1998). Field testing <br /> has also failed to find mono- or dichloroamines, epoxides, or formaldehyde <br /> compounds during treatment (Kerfoot,1997b). <br /> BATCH TESTING <br /> Five batch tests were conducted. During each test, 250 mL of a given <br /> "spiked" source water was placed into a 500 mL Erlenmeyer flask equipped with <br /> a magnetic stirring bar. Air and/or ozone were introduced into the solution <br /> through a sparger placed in the bottom of the flask. Treatment generally consistedy} <br /> of Sparging an air and ozone mixture (containing approximately 150 to 200 partsM <br /> per million-[ppm] into the flask at 5 pounds per square inch (psi) and at a rate of 5 . <br /> cubic centimeters per second (cc/sec). <br /> The effect of the contact medium, a coarse sand material (iron silicate) of <br /> differing size distribution, was evaluated during the testing. For consistency, . . <br /> glass beads were used as a control to bring the total weight of added solids to 10 <br /> grams (g) per test. <br /> Samples analyzed by a laboratory and an on-site gas chromatograph (GC) ::' <br /> were collected before treatment (time zero) and after 6 minutes of treatment. In <br /> addition, for most test runs, samples collected after 3 minutes of treatment were <br /> analyzed using the on-site GC. <br /> The results of the batch testing portion of the bench-scale stdies are shown <br /> in Table 1. In general, the 6-minute duration of the flask tests was not sufficient <br /> to reduce the spiked concentrations of the VOCs (as much as 100-400 µg/L each) <br /> to below the method detection limits. Based on the bench-scale results, the best <br /> percentage removals were achieved for PCE and the cis- and trans- 1,2-DCE, <br /> followed by TCE, and then 1,1,1-TCE. Methylene chloride, carbon tetrachloride, .. <br /> and chloroform had a si nifcand lower percent removal. � <br /> ,.. <br /> TABLE 1. Bench-scale testing for chlorinated volatile organic compound <br /> (HVOC) removal rate (volume 500 cc). <br /> Concentration (ppb) <br /> Compound 0 min. 6 min. % Removal12 <br /> Perchloroethene (PCE) 500 2 99.6 <br /> Trichloroethene (TCE) 470 50 89.4 <br /> Cis-1,2 dichloroethene 470 2 99.6 <br /> Trans-1,2 dichloroethene 480 7 98.5 <br /> 1,1,1-TCA 470 82 82.6 h <br /> Carbon tetrachloride 450 140 68.8 <br /> Methylene chloride 450 120 73.3 <br /> Chloroform 540 190 64.8 <br /> FIELD RESULTS <br /> The following results are from a site occupied by a commercial electronics <br /> supplier which had spills from circuitboard manufacture. The predominant soils <br /> are a silty fine sand. A single recirculation well was used to inject ozone into the <br />