Reductive dechlorination of perchloroethene (PCE) and bacterial community changes in a continuous-flow, two-stage anaerobic column

Abstract

This study is aimed at investigating the performance of the continuous-flow, two-stage anaerobic column for the reductive dechlorination of perchloroethene (PCE) in a trichloroethene (TCE)-contaminated aquifer without bioaugmentation. Results indicated that complete dechlorination of PCE to cis-dichloroethene (DCE) was observed within the first 12 days after the addition of lactate and PCE (620:1 mg mg−1 mass ratio). The PCE conversion to ethene was initially observed in the 2nd column after 70 days (during phase II) upon the increase of lactate to PCE mass ratio to 5000:1 (mg mg−1). However, the degradation of PCE to ethene occurred in the 1st column after 30 days operation of phase IV (217–310 d) under the high PCE feed conditions (33.65 ± 2.86 μM). 16S rDNA clone library sequence analysis confirmed that Dehalobacter sp., Desulfuromonas sp., Desulfovibrio sp. Geobacter sp., Methanosaeta sp., Methanobacterium paludism, and M. spelaei were the dominant species in the original aquifer, and their relative abundance were further changed following lactate addition. Dehalococcoides mccartyi sequences were retrieved after lactate stimulation. Overall, the continuous-flow, two-stage anaerobic column process exhibited the maximum dechlorination (6.23 μmol L−1 hr−1) of PCE without bioaugmentation, indicating its potential up-scaling application in PCE dechlorination.