Reductive Dechlorination of Tetrachloroethylene by a Chlorobenzoate-Enriched Biofilm Reactor

Article abstract of DOI:10.1021/es00053a031

This study evaluates the potential and technical feasibility of treating chloroaliphatics, common groundwater contaminants, using a specialized microbial consortium under fixed-film conditions. The reactor was developed using 3-chlorobenzoate (3-CB) as a substrate under anaerobic conditions and the enrichment that harbored an unusual dechlorinator, Desulfomonile tiedjei DCB-1. The dechlorination rate of both PCE and 3-CB increased with increasing flow rates up to 50 mL/h. The maximum observed dechlorination rates of PCE and 3-CB fed at 6.0 and 1000 μM were 2.0 and 414 μmol L h^-1, respectively. This corresponds to a PCE consumption rate of 3.7 nmol h^-1 (mg of protein)^-1 <88.9 μmol (g of protein)^-1 day^-1>. The rate of PCE dechlorination increased from 2.0 to 10.3 μmol L^-1 h^-1 when the influent PCE was increased from 6.0 to 120 μM, respectively; however, concentrations of 60 μM and above damaged reactor performance. PCE was mainly converted to TCE and cis- and trans-DCE at all the tested flow rates. Vinyl chloride (VC) was never detected, thus suggesting dechlorination of PCE to non-chlorinated products. Although the PCE dechlorination activity of the biofilm was dependent on 3-CB, the activity could be sustained for 4-5 days on cheaper substrates such as acetate or benzoate after a 1-day pulse feeding of 3-CB. In addition to PCE dechlorination, the biofilm also dechlorinated other compounds such as chloroform (CF) and 1,1,2-trichloroethane (1,1,2-TCA). The present study is important, since D. tiedjei was previousely shown to dechlorinate many other chloroaromatic and aliphatic compounds.