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A Solution in Development - ORC Enhanced Bioremediation , - r About a year ago, Regenesis began to notice that in,wells containing ORC sacks MTBE was disappearing at an unusually high rate. Data was sparse as MTBE was y rarely measured and reported, however, an intriguing trend was emerging. In some " cases the removal rates for MTBE, resumed to be' a function of biological p g degradation, were extremely high. The literature reports aerobic degradation rate constants in a range of .0231 to .0038 (half-life of 30 to 182 days). In the Regenesis ' data from 11 wells across three diverse oil company sites (CA, MI and NJ), degradation rate constants were in a range of .1447 to .0112 (half-life of 5 to 61 days). The question then became - "What is the role of ORC in this process?" Figures 1 to 3 present examples of BTEX and MTBE degradation in a single representative well for each of the three sites referenced above. Each example also reflects a low, moderate and high background level of BTEX. We believe that the presence of background hydrocarbons can interfere with the metabolism of MTBE by competent microorganisms. Thus, the documented impact of ORC on BTEX is an important factor in MTBE bioremediation. This important hypothesis evolved as a result of sharing the data with other researchers' in the field. Regenesis has since gathered evidence that supports the concept that in a mixed contaminant system BTEX is consumed preferentially to MTBE. This is not,a competitive inhibition--in that different enzyme systems are responsible for the metabolism of each compound--but rather is a pattern of ` preferential consumption (BTEX> MTBE). It can be clearly seen in Figures 2 and 3 that there is a lag in degradation of MTBE relative to BTEX. .In Figure 1, where BTEX is almost non-existent, MTBE is readily degraded from the outset. Follow-up laboratory experiments further clarified the issue. Using microbial isolates that use MTBE as a sole carbon source, Regenesis has shown the metabolism of MTBE can be largely inhibited by the addition of BTEX - causing it to fall behind in the preferential sequence of degradation. Furthermore, MTBE metabolism can be predictably modulated by the BTEX, such that when BTEX is removed from the I culture MTBE degradation resumes. Regenesis is now in the process of funding more involved column bioreactor studies which will elucidate the inhibition of MTBE by background hydrocarbons. More importantly, this Work. will establish a mass balance for the process and identify other important co-factors that may be operating in the system. The first experiments.will correlate an increase in CO2 with a decrease in.MTBE to establish that bioremediation is the primary mechanism of removal. Subsequent experiments will employ radioactively labeled MTBE and follow the appearance of various intermediates. 418197 2 a