FEASIBILITY TESTING FOR THE ON-SITE BIOREMEDIATION OF ORGANIC WASTES BY NATIVE MICROBIAL CONSORTIA

Microbial consortia capable of degrading chlorinated hydrocarbons and organic solvents may exist in many contaminated sediments. These nativ e microbial communities with the capability to bioremediate toxicants on-site may prove to be a resource during remediation efforts. For thi s study, microbial consortia capable of degrading trichloroethylene (T CE) and mixtures of chlorinated and aromatic toxicants were enriched f rom contaminated sediments and the feasibility of their participation in on-site bioremediation was examined. Batch studies were used to mon itor changes in the microbial community structure by monitoring signat ure fatty acid biomarker trends during TCE degradation. Experimental b ioreactors, which utilized sand as a support matrix for the microbial community, were constructed to study TCE and organic mixed waste degra dation. In continuously recycled expanded-bed bioreactors and a single -pass packed-bed reactor, mixtures of organic wastes were degraded inc luding: benzene, xylene, toluene, tetrachloroethylene, trichloroethyle ne, dichloroethylenes and vinyl chloride. Degradation proceeded to >99 % depletion for many contaminants. Bioreactors were stable over an 18- month period of operation while using propane or methane plus propane as energy sources and oxygen as the electron acceptor. Biodegradation was most efficient when the bioreactors were pulsed-fed, maintaining t he consortia in suboptimal conditions. For the single-pass packed-bed reactor, metabolic efficiencies of 20-70 mumol substrate per mumol TCE degraded were observed for pulse-feeding regimes while continuous sub strate availability experiments required > 180 mumol substrate per mum ol TCE. Continuous feeding experiments utilizing mixtures of organic w astes showed metabolic efficiencies of 83-240 mumol substrate utilizat ion per mumol total organic wastes degraded. These results demonstrate d efficient and simultaneous degradation of organic solvents and chlor inated hydrocarbons by environmentally derived microorganisms in labor atory reactors.