HR: 16:45h
AN: H44D-04    [Abstracts]
TI: Influence of Chemotaxis on Bacterial Dispersion in Porous Media
AU: * Ford, R M
EM: rmf3f@virginia.edu
AF: University of Virginia, Department of Chemical Engineering, P.O.Box 400742, Charlottesville, VA 22903, United States
AU: Narayanaswamy, K
EM: kn5d@virginia.edu
AF: University of Virginia, Department of Civil Engineering, Charlottesville, VA 22903, United States
AU: Wood, B D
EM: brian.wood@oregonstate.edu
AF: Oregon State University, School of Chemical, Biological, and Environmental Engineering, Corvallis, OR 97330, United States
AB: Bioremediation of groundwater is limited by the degree to which microorganisms and pollutants are mixed together in the subsurface environment. Good mixing is difficult to achieve because of the structure of geological media and the unavailability of external mixing devices. Chemotaxis, which is the ability of motile bacteria to sense chemical concentration gradients in their local surroundings and swim toward higher concentrations of attractants, could potentially enhance the mixing and expedite the biodegradation process. The chemotactic migration on the pore-scale could eventually result in greater dispersion at the field-scale. In this study, the volume averaging method was used to derive an expression that accounts for chemotactic responses to local chemical gradients in the dispersion coefficient at larger scales. We will present results where the upscaling scheme was applied to problems with well defined hydraulic conditions such as a series of inline cylinders, and well-defined chemical gradients. In general, increasing the attractant gradients resulted in greater bacterial dispersion coefficients. Engineering correlations were developed to relate the enhanced dispersion to dimensionless groups such as the Peclet number and a dimensionless chemotactic driving force defined in this work. It was found that under certain constraints, the effect of chemotaxis was to increase the dispersion coefficient by an additional term that was a linear function of the chemotactic driving force, i.e. E=D_bulk+α v+ β σ, where D_bulk is the bulk diffusion coefficient, v is the fluid velocity, σ is the dimensionless chemotactic driving force we defined, and α and β are appropriate dispersivities. This study will improve our physical understanding of how chemotaxis impacts dispersion and allow us to quantify dispersion in terms of bacterial properties and structure of the geologic media. The engineering correlations that result are critical for improving our assessment and implementation of bioremediation strategies.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1847 Modeling
DE: 1849 Numerical approximations and analysis
SC: Hydrology [H]
MN: 2007 Fall Meeting