MICROCOSM AND IN-SITU FIELD STUDIES OF ENHANCED BIOTRANSFORMATION OF TRICHLOROETHYLENE BY PHENOL-UTILIZING MICROORGANISMS

The ability of different aerobic groundwater microorganisms to cometab olically degrade trichloroethylene (TCE), 1,2-cis-dichloroethylene (c- DCE), and 1,2-trans-dichloroethylene (t-DCE) was evaluated both in gro undwater-fed microcosms and in situ in a shallow aquifer. Microcosms a mended with phenol or toluene were equally effective in removing c-DCE (>90%) followed by TCE (60 to 70%), while the microcosm fed methane w as most effective in removing t-DCE (>90%). The microcosm fed ammonia was the least effective. None of the microcosms effectively degraded 1 ,1,1-trichloroethane. At the Moffett Field groundwater test site, in s itu removal of c-DCE and TCE coincided with biostimulation through phe nol and oxygen injection and utilization, with c-DCE removed more rapi dly than TCE. Greater TCE and c-DCE removal was observed when the phen ol concentration was increased. Over 90% removal of c-DCE and TCE was observed in the 2-m biostimulated zone. This compares with 40 to 50% r emoval of c-DCE and 15 to 25% removal of TCE achieved by methane-grown microorganisms previously evaluated in an adjacent in situ test zone. The in situ removal with phenol-grown microorganisms agrees qualitati vely with the microcosm studies, with the rates and extents of removal ranked as follows: c-DCE > TCE > t-DCE. These studies demonstrate the potential for in situ TCE bioremediation using microorganisms grown o n phenol.