ENRICHMENT OF HIGH-RATE PCE DECHLORINATION AND COMPARATIVE-STUDY OF LACTATE, METHANOL, AND HYDROGEN AS ELECTRON DOPERS TO SUSTAIN ACTIVITY

The influence of three electron donors on the ability to sustain rapid tetrachloroethene (PCE) dechlorination in mixed cultures was investig ated. Experiments were performed in recycle columns containing either a high-rate PCE dechlorinating culture developed from granular sludge or a (1:1) mixture of this culture with an enrichment culture derived from soil cores taken from a chlorinated ethene contaminated site. Col umns were fed PCE (aqueous concentration of 5 mg/L) and either lactate , methanol, or H-2 as their electron donor. Comparisons between electr on donors were formulated using the observed rates of PCE disappearanc e and the extent of dechlorination achieved in each column. Over a per iod exceeding 1 year, the observed PCE half-life in each column was fo und to decrease from approximately 13 h to slightly less than 2 h, reg ardless of electron donor fed. Although initial mass balance studies d emonstrated that the extent of dechlorination varied between inoculum and electron donor, overtime, the recycle columns behaved similarly, a nd PCE was recovered as approximately 80% vinyl chloride and 20% ethen e in ail systems. Rates and extents of PCE dechlorination were improve d over time in systems containing high H-2 partial pressures (0.8 atm) in the presence of an active methanogenic community.