Removal of low concentrations of carbon tetrachloride in compost-based biofilters operated under methanogenic conditions

Research was performed to demonstrate the removal of carbon tetrachloride ( CT) using compost biofilters operated under methanogenic conditions. Biofil ters were operated at an empty-bed residence time of 2.8 minutes using nitr ogen as the atmosphere. Hydrogen and carbon dioxide were supplied as an ele ctron donor and carbon source, respectively, during acclimation of the bed medium microbes. Once methanogenesis was demonstrated, CT now to the biofil ter was established. Biofilters were operated over a CT concentration range from 20 to 700 ppbv for 6 months. Bed medium microbes were able to remove up to 75% of the inlet CT. At excessively high CT concentrations (>500 ppmv ), methane production and hydrogen utilization by the bed medium microbes a ppeared to be inhibited. CT removal by the biofilter decreased when the hyd rogen supply was removed from the biofilter inlet, indicating that hydrogen acted as the electron donor for reductive dechlorination. The removal effi ciency and relatively low empty bed residence times demonstrated by these l aboratory-scale biofilters indicate that anaerobic biofiltration of CT may be a feasible full-scale process.