(76a) Kinetic Parameter Estimation from Experimental Laboratory Data for Modeling Reactions Occurring in a Groundwater Permeable Reactive Barrier

Permeable reactive barrier (PRB) technology is used to treat contaminated groundwater in situ in a groundwater aquifer. Groundwater contaminants passing through the PRB are treated by reactions occurring within the unit or immediately downgradient of it. A biowall is a type of PRB that contains bark mulch or other agricultural waste material, which serves as an electron donor to promote biodegradation processes such as reductive dechlorination for trichloroethylene degradation. The biodegradation of bark mulch, and the anaerobic conditions resulting from said biodegradation, can lead to the presence of organic carbon and sulfide, the latter arising from biological reduction of sulfate, in the groundwater downgradient of a PRB. The presence of these dissolved species can be deleterious to the environment if the treated groundwater discharges to a nearby surface water receptor.

The research work presented here focuses on the effluent concentrations of dissolved species from a laboratory column operated in a manner to mimic a groundwater biowall. The data from this laboratory column is used to estimate the kinetic parameters of a time-dependent one-dimensional fate and transport model of the biowall and downgradient groundwater. The model was developed by applying mass balance equations over a control volume of the aquifer between a biowall and a surface water body receptor. MATLAB was used to solve the family of partial differential equations for a timescale extending to approximately 4 years, using appropriate initial / boundary condition values. The species incorporated into the model include glucose (surrogate for carbon source upon degradation of solid carbonaceous material), lactic acid (surrogate for fatty acids), the electron donor sulfate and the product of sulfate reduction, namely sulfide. The agreement between model results and the laboratory column data is presented.