HR: 11:35h
AN: B31F-06 INVITED     [PDF]
TI: Multi-Component Reactive Transport Modeling of Field-Scale Bioremediation: The Schoolcraft Site
AU: * Phanikumar, M
EM: phani@egr.msu.edu
AF: Michigan State University Department of Civil & Environmental Engineering, A127 Engineering Research Complex, East Lansing, MI 48824 United States
AU: * Phanikumar, M
EM: phani@egr.msu.edu
AF: Michigan State University Department of Geological Sciences, 206 Natural Science Building, East Lansing, MI 48824 United States
AU: Hyndman, D W
EM: hyndman@msu.edu
AF: Michigan State University Department of Geological Sciences, 206 Natural Science Building, East Lansing, MI 48824 United States
AU: Dybas, M J
EM: dybas@egr.msu.edu
AF: Michigan State University Department of Civil & Environmental Engineering, A127 Engineering Research Complex, East Lansing, MI 48824 United States
AB: This paper describes three-dimensional multi-component reactive transport modeling for bioremediation of a carbon tetrachloride (CT) contaminated plume at the Schoolcraft site in Western Michigan. The denitrifying bacterium Pseudomonas Stutzeri Strain KC is used to mediate cometabolic reactions that degrade CT to harmless end products. CT contamination at this site occurred due its use in the past as a fumigant in grain silos. The goal of the field bioremediation design was to inoculate a transect perpendicular to the natural gradient flow of a CT plume with microbes that could effectively remediate the CT contamination through a series of pulsed nutrient injections. The final design consisted of fifteen wells spaced one meter apart in which each well can operate either as an injection or an extraction well depending on the event. This design allowed us to operate in a semi-passive mode of operation with only 6 hours of pumping per week. Our modeling approach integrates information from laboratory-scale studies aimed at understanding the relevant rates and processes under controlled conditions with plume-scale modeling in the presence of a high degree of hydraulic control and significant heterogeneity to delineate the important differences in processes/rates as we proceed from the laboratory to the field. We describe the development of a seven component reactive transport model that includes the transport of aqueous and sorbed-phase CT, mobile and immobile bacteria, acetate (electron donor), nitrate (electron acceptor) and tracer (bromide) and show detailed comparisons of observed and simulated concentrations at a number of wells and at different depths. Processes simulated in the model include advection, dispersion, degradation, two-site sorption, microbial attachment, detachment, growth and decay. We describe the influence of several modeling decisions (e.g., effects of dynamic partitioning, bioavailability and sorption) on the predictions of the model. Most parameters in the reactive transport model were fixed based on earlier laboratory experiments and literature values and only a few parameters were changed due to the likelihood of differences between the laboratory and field. The computational model used a non-uniform grid with very fine cells placed around the delivery well gallery to better resolve the gradients. We present the spatial-temporal evoluation of the degradation front and the microbial concentration fields and demonstrate how high-resolution numerical models can be used to aid our understanding of complicated field-scale processes.
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Biogeosciences [B]
MN: 2003 Fall Meeting