"Imaging Microbial Biofilms in Opaque Porous Media: Method development and application"
Friday, April 19, 2013, 10 am
Large Conference Room, Building 703
Hosted by: Wah-Keat Lee
Biofilm growth in porous media can influence porosity, permeability, dispersion, diffusion, and mass transport of solutes. Even small scale changes in pore morphology have been shown to significantly influence the hydrodynamics of porous systems. However, the direct observation of biofilm formation and development in porous media is challenging. To date, porous media-associated biofilm research has focused predominantly on investigations of biomass formation in two-dimensional systems, due to (1) the opaque nature of common porous materials, and (2) the direct dependence of conventional biofilm imaging techniques on optically transparent systems. In order to further understand porous media-associated biofilm growth, techniques for quantitatively assessing the three-dimensional spatial distribution of biomass, non-destructively, within opaque porous materials is required for the development of improved reactive transport and biofilm growth models. Two methods for imaging biofilm within porous media using x-ray microtomography will be presented. The first method utilizes silver-coated glass microspheres as a surface attached contrast agent for delineating the biofilm-aqueous phase interface within porous media. The second method introduces a barium sulfate suspension to the aqueous phase which is excluded from the biofilm matrix, thereby allowing direct segmentation of the solid, biofilm and aqueous phases. Imaging results using both of these methods will be presented along with the respective advantages and limitations. Results will be presented where biofilm growth characteristics and changes in porous media hydrodynamics associated with bioclogging have been investigated across the Darcy flow regime and into the steady inertial flow regime (0.1 < Re <15). Quantified image data sets are compared to measured bulk changes in hydrodynamic properties associated with biofilm growth, or bio-clogging. In addition, pore scale imaging enables the analysis o