The dechlorination of TCE by a perchlorate reducing consortium

Abstract We enriched a trichloroethene (TCE)-dechlorinating consortium from a perchlorate-reducing bacterial culture (PRB) with a very low initial abundance of Dehalococcoides by feeding the culture lactate and TCE; named the novel culture perchlorate-reducing dechlorinating bacteria (PRTB). Short batch tests showed that the PRTB consortium reduced up to 0.45 mmol/L of TCE to non-toxic ethene in eight days after two additions of TCE and simultaneously reduced up to 0.15 mmol/L of ClO 4 − to Cl − . TCE reduction by PRTB was sensitive to oxygen: 0.2 mg/L of oxygen delayed reduction of TCE to ethene from 5 to 15 days, while ⩾0.5 mg/L of oxygen significantly inhibited TCE reduction, causing vinyl chloride accumulation. After the consortium was enriched twice with TCE, the Dhc gene (reflecting the abundance of Dehalococcoides ) increased from 1.14 × 10 4 to 3.25 × 10 8 copies/mL. The original PRB culture was dominated by Proteobacteria (78.4%), but the enriched PRTB culture was dominated by Chloroflexi (57.7%). The relative abundance of Dehalococcoides increased from 0.02% to 57.4%. Other presumptive dechlorinators Desulfuromonas and Geobacter were enriched as well. Possible acetogens ( Spirochaetes ) and putative fermenters ( Bacteroidetes and Desulfovibrio ) were also present in the culture, providing Dehalococcoides with acetate as the carbon source, hydrogen gas as the electron donor, and Vitamin B 12 as a growth factor.