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10/12/1998 16:69 9165350207 APEX ENVIROTECH PAGE 36 microorganisms, ,normally slow to metabolize the substrate, do so at greater efficiency in higher oxygen concentrations. This theory will also be tested in the bioreactor experiments. There are examples in the;;literature, specifically with PCP degrading fungi, that establish a relationship between high oxygen concentrations and high rates of degradation. This is important because ORC, as a pure oxygen :source, is capable of generating dissolved oxygen levels in excess of those achieved by air saturation. Encouraging results were obtained from a recent data set showing MBE degradation outside an area that was source treated with ORC slurry injections. In Wisconsin, after about four months, the degradation rate in a well five feet downgradlent of the treated area was .0434 (half-life of 25 days). This is('presented In Figure 4. Note that these are not measurements from a well with ORC socks; the well is downgradlent from an ORC source injection zone and was exposed to oxygenated groundwater derived from the Injection array. Earlier we stated,L.that the biological degradation mechanisms were putative. Several other abiotic explanations planet ons must be considered and systematically :eliminated; the following dialogue is intended to anticipate the appropriate questions. ` Q.'-Is MTBE being absorbed by ORC? Does ORC chemically destroy WOE? A.;lVo. Experiments in the laboratory have shown that there is no Chemical or physical reaction between ORC and MCBE. This eliminates the passibility that any type of absorption by ORC or direct chemical oxidation Is occurring. ORC particles are insoluble and, when applied in filter socks, will not migrate from the application well. Groundwater samples were-collected by standard purge methods (three to five casing volumes). Any chemical reactions occurring on the surface of ORC particles in the source well would therefore be diluted out, particularly on the sites in question which''hav e low ground water velocity. Furthermore, the new data show posltive results at a distance from the ORC source wells. The fact that oxygen is slowly diffusing from ORC, wh"'.',In turn is stimulating bioremediation of MTBE and competing species such as BTEX, remains the most the likely .mechanism of action: Q. Is the MTBE being volatilized from-the well? A. This is highly unlikely, although experiments are being planned to account for this. For the moment, one must realize that MTBE does not readily;strip and that the release of oxygen from ORC is not forceful Gke air sparging. if MTBE were being stripped from a well volume, that strlpl� groundwater would experience the previously mentioned dilution in sampling. In addition, the results In Figure 4. which were derived from a downgradlent monitoring point, provide good initial evidence that that KME is not being stripped.