Development and Sensitivity Analysis of a Fully Kinetic Model of Sequential Reductive Dechlorination in Groundwater

Abstract

A fully kinetic biogeochemical model of sequential reductive dechlorination (SERD) occurring in conjunction with lactate and propionate fermentation, iron reduction, sulfate reduction, and methanogenesis was developed. Production and consumption of molecular hydrogen (H(2)) by microorganisms have been modeled using modified Michaelis-Menten kinetics and has been implemented in the geochemical code PHREEQC. The model have been calibrated using a Shuffled Complex Evolution Metropolis algorithm to observations of chlorinated solvents, organic acids, and H(2) concentrations in laboratory batch experiments of complete trichloroethene (TCE) degradation in natural sediments. Global sensitivity analysis was performed using the Morris method and Sobol sensitivity indices to identify the most influential model parameters. Results show that the sulfate concentration and fermentation kinetics are the most important factors influencing SERD. The sensitivity analysis also suggests that it is not possible to simplify the model description if all system behaviors are to be well described.

Reductive Dechlorination of Trichloroethylene (TCE) in Competition with Fe and Mn Oxides—Observed Dynamics in H2-dependent Terminal Electron Accepting Processes

“…Electron flow up to 20-85% towards iron reduction was observed in other studies (Azizian et al, 2008;Azizian et al, 2010;Malaguerra et al, 2011;Paul et al, 2013). A previous study by Sleep et al (2005) also observed cis-DCE as the terminal end product of PCE dechlorination under electron donor limited conditions.…”

A modeling approach integrating microbial activity, mass transfer, and geochemical processes to interpret biological assays: An example for PCE degradation in a multi-phase batch setup

“…Modeling of multi-phase batch systems has previously been used to describe chlorinated ethene degradation and isotope fractionation, but these models do not include complex aquatic geochemistry (Aeppli et al, 2009;Buttet et al, 2018;Jin et al, 2013). Likewise, kinetic models to investigate batch or microcosm experiments of contaminant degradation and microbial communities account for neither mass transfer limitations nor the influence of sample removal on the determination of microbial kinetic parameters (Chambon et al, 2013;Jin and Rolle, 2016;Kouznetsova et al, 2010;Malaguerra et al, 2011;Wade et al, 2016).…”

Reductive dechlorination of 1,2-dichloroethane in the presence of chloroethenes and 1,2-dichloropropane as co-contaminants

“…The description of the reaction kinetics varies from first-order (Corapcioglu et al 2004; Da Silva and Alvarez 2008) to the more elaborate Michaelis-Menten equations (Garant and Lynd 1998; Haston and McCarty 1999) or Monod kinetics if the responsible OHRB can be sufficiently quantified (Yu and Semprini 2004). The latter two kinetic modeling approaches have been applied at lab and field scales to study competitive inhibition (Christ and Abriola 2007; Lai and Becker 2013; Yu et al 2005), self-inhibition (Haest et al 2010a), electron donor limitation (Cupples et al 2004), dechlorination in the presence of multiple bacterial species (Brovelli et al 2012; Duhamel and Edwards 2006; Haest et al 2010b), and dechlorination in conjunction with fermentation, sulfate reduction, or methanogenesis (Kouznetsova et al 2010; Malaguerra et al 2011). The Michaelis-Menten and Monod kinetic modeling approaches can also be used to study the dechlorination of chloroethanes or chloropropanes; however, examples in literature are rare.…”