PARENT SESSION

WA1 Biorestoration Strategies for Contaminated Sediments
256 Portland Ballroom
8:00 AM - 12:00 PM, Wednesday

() Haldane Inhibition for Reductive Dechlorination at High PCE and TCE Concentrations.

Yu, S¹, Semprini, L¹, ¹ 1Dept. of Civil, Construction and Environmental Engineering, Oregon State University

ABSTRACT- Two biokinetic models for anaerobic reductive dechlorination were developed and compared with results from batch kinetic tests conducted over a wide range of tetrachloroethylene (PCE) and trichloroethylene (TCE) concentrations with two different dechlorinating cultures. One model applies Michaelis-Menten kinetics with competitive inhibition among chlorinated aliphatic hydrocarbons (CAHs), while the other model includes both competitive inhibition and Haldane inhibition at high CAH concentrations. At PCE concentrations lower than 300 M, both model simulations simulated the experimental results well. However, simulations with competitive inhibition deviated from the experimental observations for PCE or TCE concentrations greater than 300-400 M. The kinetic model that incorporated both competitive and Haldane inhibitions better simulated experimental data for PCE concentrations up to near the solubility limit (1000 M), and TCE concentrations at half its solubility limit (4000 M). Based on the modeling analysis of the experimental results, the PM culture (Point Mugu, CA) showed Haldane inhibition constants of 900, 6000, 7000 M for TCE, cis-1,2-dichlororethylene (c-DCE) and vinyl chloride (VC), indicating very weak Haldane inhibition for c-DCE and VC, while the EV culture (the Evanite site in Corvallis, OR) had lower Haldane inhibition constants for TCE, c-DCE, and VC of 900, 750, and 750 M, respectively. The PM and BM (a binary mixed culture of the PM and EV cultures) dechlorinating cultures showed better dechlorination abilities at high TCE concentrations (4073 M) than the EV culture. The EV and BM cultures more effectively transformed a wide range of PCE concentrations than the PM culture. Therefore, the BM culture had better transformation abilities than the individual cultures over a wide range of PCE and TCE concentrations. Modeling results indicated that a combination of competitive and Haldane inhibition kinetics is required to simulate dechlorination over a broad range of concentrations up to the solubility limits of PCE and TCE.

Key words: haldane inhibition, reductive dechlorination, competitive inhibition, pce tce