Tetrachloroethene dechlorination kinetics by Dehalospirillum multivorans immobilized in upflow anaerobic sludge blanket reactors

Tetrachloroethene (C2Cl4) dechlorination kinetics in upflow anaerobic sludg e blanket (UASB) reactors was determined after introducing c-le novo activi ties into the granular sludge. These activities were introduced by immobili zing Dehalospirillum multivorans in a test reactor containing unsterile gra nular sludge, and in a reference reactor, R1, containing sterile granular s ludge. A second reference reactor, R2, contained only unsterile granular sl udge and served as a control. The kinetic experiments were performed by pul sing the reactors with C2Cl4 in a recirculating batch mode. Formate and ace tate were added as electron donor and carbon source. Both reactors inoculat ed with D. multivorans dechlorinated C2Cl4 to an equimolar amount of C2H2Cl 2 With only traces of C2HCl3 in the effluent. In the control reactor, C2HCl 3 accumulated before C2H2Cl2 was produced. A computer simulation program (A QUASIM) was used to estimate the kinetic parameters. The half-saturation co nstants (K-s) for C2Cl4 and C2HCl3 were almost equal in the reactors contai ning D. multivorans (17 mu M and 18 mu M for C2Cl4; 26 mu M and 28 mu M for C2HCl3), indicating no influence of sludge bacteria on the affinity of D. multivorans for C2Cl4 and C2HCl3. The maximum dechlorination rates (k(m)X(B )) were about twice as high in the reactor containing D. multivorans immobi lized in sterile sludge (11 mmol C2Cl4 1 sludge(-1) day(-1) and 27 mmol C2H Cl3 1 sludge(-1) day(-1)) than in the test reactor (4.4 mmol C2Cl4 1 sludge (-1) day(-1) and 15 mmol C2HCl3 1 sludge(-1) day(-1)). Compared to other C2 Cl4-degrading systems, the dechlorination rates of the inoculated reactors and their affinities for C2Cl4 and C2HCl3 were high. Therefore, introductio n of de novo activity is promising for the use of anaerobic reactors to bio remediate C2Cl4-polluted water.