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PERFORMANCE OF AIR SPARGING AND SOIL VACUUM EXTRACTION FOR TREATMENT OF MTBE AND BENZENE AT UST SITES IN KANSAS
Citation:
Wilson*, J T., B. H. Wilson, AND G. Hattan. PERFORMANCE OF AIR SPARGING AND SOIL VACUUM EXTRACTION FOR TREATMENT OF MTBE AND BENZENE AT UST SITES IN KANSAS. Presented at National Ground Water Association Focus Conference on MTBE, Orange, CA, June 6-7, 2002.
Description:
The efficacy of soil vacuum extraction or air sparging and soil vacuum extraction for remediation of ground water contamination with MTBE was compared to remediation of contamination with benzene. There was no practical difference.
Sites were identified that met the following criteria. They used soil vacuum extraction or air sparging and soil vacuum extraction as the remedial technology, there were detectable concentrations of both MTBE and benzene in monitoring wells when remediation began, and data were reported from at least two time periods of ground water monitoring. As of December 2000, Kansas had 37 sites that met the criteria for evaluation. At 7 of the sites, active remediation was concluded and the sites were in a phase of monitoring. At the remaining 30 sites remediation is in progress. In general the concentration of benzene in these sites was higher than the concentration of MTBE. The maximum concentration of MTBE was 92,000 ~g/liter. The concentration of MTBE exceeded 970 ~g/liter at 25% sites, exceeded 355 ~g/liter at 50% of sites, exceeded 105 ~g/liter at 75% of sites, and the minimum concentration in the group of 37 sites was 15 ~g/liter. The maximum concentration of benzene was 108,000 ~g/liter. The concentration of benzene exceeded 8600 ~g/liter at 25% sites, exceeded 1470 ~g/liter at 50% of sites, exceeded 562 ~g/liter at 75% of sites, and the minimum concentration in the group of 37 sites was 78 ~g/liter.
The proportional reduction in concentration of the two contaminants at each site was calculated by dividing the maximum concentration of MTBE by the current concentration of MTBE and by dividing the maximum concentration of benzene by the current concentration of benzene. The reduction in concentration of contaminants in ground water was assigned to one of four categories: (1) 100 fold or greater, (2) from 100 fold to 10 fold, (3) from 10 fold to 1, and (4) concentrations increased instead of decreasing. At four sites the reduction of concentrations of MTBE was 100 fold or greater, compared to eight sites for benzene. At seventeen sites the reduction in concentration of MTBE was from 100 fold to 10 fold, compared to nine sites for benzene. At twelve sites the reduction in concentration of MTBE was 10 fold to 1 fold, compared to fifteen sites for benzene. At four sites the reduction in concentration of MTBE increased, compared to five sites for benzene. The geometric mean of the proportional removal of MTBE was a 10.7 fold reduction in concentration, while the geometric mean of the proportional removal of benzene was an 8.7 fold reduction.
The absolute removal of MTBE or benzene was calculated by subtracting the current concentration from the maximum concentration. The maximum removal of MTBE was 90,500 ~g/liter, while the maximum removal of benzene was 90,587 ~g/liter. Ten percent of sites removed more than 9,100 ~g/liter of MTBE or 16,500 ~g/liter of benzene. Twenty five percent of sites removed more than 625 ~g/liter of MTBE or 2,730 ~g/liter of benzene. Fifty percent of sites removed more than 244 ~g/liter of MTBE or 835 ~g/liter of benzene.