Continuous dechlorination of tetrachloroethene in an upflow anaerobic sludge blanket reactor

Influences of hydraulic retention time (HRT) on dechlorination of tetrachloroethene (PCE) were investigated in an upflow anaerobic sludge blanket (UASB) reactor inoculated with anaerobic granular sludge non-pre-exposed to chlorinated compounds. PCE was introduced into the reactor at a loading rate of 3 mg/l d. PCE removal increased from 51 ± 5% to 87 ± 3% when HRT increased from 1 to 4 d, corresponding to an increase in the PCE biotransformation rate from 10.5 ± 2.3 to 21.3 ± 3.7 μmol/d. A higher ethene production rate, 0.9 ± 0.2 μmol/d, was attained without accumulation of dichloroethenes at the HRT of 4 d. Dehalococcoides-like species were detected in sludge granules by fluorescence in situ hybridization, with signal strength in proportion to the extent of PCE dechlorination.