Integrated anaerobic degradation of tetrachloroethylene by vitamin-B_(12) and zero-valent iron

摘要

In this laboratory study, vitamin B_(12) and zero-valent iron was added to enhance the process of anaerobic dechlorination of PCE by a mixed culture of Methanosaeta concilii and Methanosaeta sp.. Experimental results showed that the initial PCE removal rate increased with the addition of vitamin B_(12). When the concentration of vitamin B_(12) increased from 0 nM to 240 nM, the initial PCE removal rate increased from 4.8 #mu#g/L-d to 20.1 #mu#g/L-d. However, the rate increase insignificantly when the concentration of vitamin B_(12) was higher than 240 nM. The addition of iron powder also resulted in decreasing the formation of chlorinated intermediates, ethene was the major end-product, vinyl chloride was under the detection limit. The presence of microbial cells and iron powder (5.0g-Fe~0/L) presented a PCE pseudo-first-order degradation reaction constant of 0.43 day~(-1). The PCE removal rate was further enhanced to 0.49 day~(-1) when integrated with 240nM of vitamin B_(12). The effluents were examined by anaerobic toxicity assay (ATA) and found the maximum rate ratio (MRR) were greater than 0.95. Therefore, using anaerobic microbes with addition of zero-valent iron and vitamin B_(12) is a feasible method to treat PCE-contaminated groundwater.