Web Release Date: December 3,
Kinetics and Inhibition of Reductive Dechlorination of Chlorinated Ethylenes by Two Different Mixed Cultures
Department of Civil, Construction, and Environmental Engineering, Oregon State University, Corvallis, Oregon 97331
Received for review March 1, 2004
Revised manuscript received October 4, 2004
Accepted October 11, 2004
Abstract:
Kinetic studies with two different anaerobic mixed
cultures (the PM and the EV cultures) were conducted to
evaluate inhibition between chlorinated ethylenes. The
more chlorinated ethylenes inhibited the reductive
dechlorination of the less chlorinated ethylenes, while the
less chlorinated ethylenes weakly inhibited the dechlorination of the more chlorinated ethylenes. Tetrachloroethylene
(PCE) inhibited reductive trichloroethylene (TCE) dechlorination but not cis-dichloroethylene (c-DCE) dechlorination,
while TCE strongly inhibited c-DCE and VC dechlorination.
c-DCE also inhibited vinyl chloride (VC) transformation
to ethylene (ETH). When a competitive inhibition model was
applied, the inhibition constant (KI) for the more chlorinated
ethylene was comparable to its respective Michaelis-Menten half-velocity coefficient, KS. Model simulations using
independently derived kinetic parameters matched the
experimental results well. kmax and KS values required for
model simulations of anaerobic dechlorination reactions
were obtained using a multiple equilibration method conducted
in a single reactor. The method provided precise kinetic
values for each step of the dechlorination process.
The greatest difference in kinetic parameters was for the
VC transformation step. VC was transformed more
slowly by the PM culture (kmax and KS values of 2.4 ± 0.4
mol/mg of protein/day and 602 ± 7 M, respectively)
compared to the EV culture (8.1 ± 0.9 mol/mg of
protein/day and 62.6 ± 2.4 M). Experimental results and
model simulations both illustrate how low KS values
corresponded to efficient reductive dechlorination for the
more highly chlorinated ethylenes but caused strong
inhibition of the transformation of the less chlorinated
products. Thus, obtaining accurate KS values is important
for modeling both transformation rates of parent compounds
and their inhibition on daughter product transformation.
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