Dechlorination kinetics of TCE at toxic TCE concentrations: Assessment of different models.
The reductive dechlorination of trichloroethene (TCE) in a TCE source zone can be self-inhibited by TCE toxicity. A study was set up to examine the toxicity of TCE in terms of species specific degradation kinetics and microbial growth and to evaluate models that describe this self-inhibition. A batch experiment was performed using the TCE dechlorinating KB-1 culture at initial TCE concentrations ranging from 0.04mM to saturation (8.4mM). Biodegradation activity was highest at 0.3mM TCE and no activity was found at concentrations from 4 to 8mM. Species specific TCE and cis-DCE (cis-dichloroethene) degradation rates and Dehalococcoides numbers were modeled with Monod kinetics combined with either Haldane inhibition or a log-logistic dose-response inhibition on these rates. The log-logistic toxicity model appeared the most appropriate model and predicts that the species specific degradation activities are reduced by a factor 2 at about 1mM TCE, respectively cis-DCE. However, the model showed that the inhibitive effects on the time for TCE to ethene degradation are a complex function of degradation kinetics and the initial cell densities of the dechlorinating species. Our analysis suggests that the self-inhibition on biodegradation cannot be predicted by a single concentration threshold without information on the cell densities.
Haest
P J
PJ
Division Soil and Water Management, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium.
Springael
D
D
Smolders
E
E
D001673:Biodegradation, Environmental; D041862:Chloroflexi / Q000378:metabolism; D054879:Halogenation; D007700:Kinetics; D008962:Models, Theoretical; D014241:Trichloroethylene / Q000378:metabolism*
D014241:Trichloroethylene