Combination of Membrane Substrate Feeding Bioreactor and Zero-valent Metal Reduction Technology - Dechlorination of TCE by Immobilized Autotrophic Hydrogen-bacteria and Zero-valent Iron

Trichloroethylene (TCE) is the most ubiquitous chlorinated compound found in groundwater contamination. The objective of this study was to evaluate the dechlorination rate (from an initial concentration of 180 μmol per liter) and synergistic effect of combining commercial Fe0 and autotrophic hydrogen-bacteria in the presence of hydrogen during TCE degradation process. In the batch test, the treatment using Fe0 in the presence of hydrogen (Fe0/H2) showed more effective dechlorination and less iron consumption than Fe0 utilized only (Fe0/N2), meaning that catalytic degradation had promoted transformation of TCE and the iron was protected by cathodic hydrogen. The combined use of Fe0 and autotrophic hydrogen-bacteria was found to be more effective than did the individual exercise even though the hydrogen was insufficient during the batch test. By the analysis of XRPD, the crystal of FeS transformed by sulfate reducing bacteria (SRB) was detected on the surface of iron after the combined treatment. The synergistic impact was caused by FeS precipitates which enhanced TCE degradation through catalytic dechlorination. The dechlorination rate coefficient of the combined method in MFSB was 3.2-fold higher than that of iron particles individual used. Additionally, the continuous column study showed the combined method improved the TCE degradation efficiency and accumulation of cis-DCE in long-tern operation. Results from batch and continuous column experiment revealed that the proposed combined method has the potential to become a cost-effective remediation technology for the chlorinated-solvent contaminated site.