BIODEGRADATION OF MIXED-ORGANIC WASTES BY MICROBIAL CONSORTIA IN CONTINUOUS-RECYCLE EXPANDED-BED BIOREACTORS

Microbial consortia enriched from subsurface sediments contaminated with chlorinated hydrocarbons proved capable of degrading mixed-organic wastes. Methane and/or propane as foodstock enabled aerobic mineralization of greater than 20 mg L-1 trichloroethylene (TCE) plus 1 mg L-1 vinyl chloride, benzene, and toluene in cell suspension or bioreactor experiments. The microbial consortia degraded 80-95% of TCE at 20 mg L-1 within 5 days in continuous-recycle expanded-bed bioreactors requiring 50-100 mol of food stock/mol of TCE degraded. When the bioreactors were challenged with groundwaters contaminated with mixed-organic wastes, the microbial consortia degraded greater than 99% of the benzene, toluene, xylene, vinyl chloride, and nine chlorinated hydrocarbons, 85% of the TCE, and 60% of the tetrachloroethylene within 21 days, while requiring 80-mu-mol of methane plus propane per micromole of mixed-organic waste degraded. The potential for bioremediation of groundwater contaminated with mixed-organic wastes was demonstrated in laboratory reactors.