Anaerobic biotrickling filter for trichloroethylene removal from contaminated sites
Aerobic biotreatment of trichloroethylene(TCE)-laden soil vapor extraction gases has not found practical application because of its recalcitrance. This study looks at removing TCE from contaminated sites by anaerobic gas-phase biotreatment. An anaerobic biotrickling filter, inoculated with a mixed culture containing Dehalococcoides sp. removed TCE by converting it predominantly to ethylene with some formation and degradation of cis-dichloroethene (cis-DCE) and vinyl chloride (VC). Microorganisms from the Dehalococcoides genus are known to reduce chlorinated solvents while oxidizing hydrogen. Sodium lactate, a fermentable substrate, was provided to the reactor through the recirculating liquid as a source of hydrogen. The reactor removed >90% TCE at loadings of up to 4 gTCE mbed-3 h-1. The distribution of the intermediates of TCE biodegradation was found to be affected by the pH of the recirculating liquid with better conversion to ethylene (>50%) observed at pH 6.85, compared to only 10% conversion to ethylene at pH 8.3. Kinetic investigations using a batch biotrickling filter confirmed the trend observed in the distribution of intermediates. Overall, the study shows that anaerobic biotreatment of TCE-laden waste gases is possible and provides an alternative for remediation of contaminated sites.
