Interactions between Biofilm Growth and Fluid Flow in Porous Media
Abstract
Many engineered and natural systems are influenced by biofilms, which are surface attached communities of microorganisms embedded in a matrix composed of microbially produced extracellular polymeric substances. In porous media, biofilms can progressively accumulate within pore spaces, making it increasingly difficult for fluids to flow through the pore network. Therefore, biofilms are often considered to be detrimental in processes relying on fluid flow in porous media. Engineering biofilm development in porous structures, however, can maximize the beneficial aspects of biofilms while minimizing their detrimental effects. Due to an inadequate understanding of interactions between flow properties and biofilm development, field scale applications of biofilm based processes are still unpredictable.
This study was divided to two main parts. The first part focused on a theoretical investigation of biofilm growth in porous media. By treating biofilm as an evolving viscous fluid that shares void spaces with a separate aqueous phase in porous media, a novel macroscopic approach was developed to simulate biofilm growth in porous media. Modelling results revealed that relative permeability functions can be used to link flow of water to biofilm saturation. However, this modelling approach was complex, and certain model parameters needed to be experimentally determined.
Therefore, in the second part of the study, by using a bioluminescent bacterium, a noninvasive imaging method was developed to visualize biofilm evolution within porous media. Detected bioluminescence intensities were used to nondestructively quantify biofilm and porous media characteristics. The imaging technique was also used to study bacterial transport in porous media with different hydraulic properties. Results indicated that biofilm formation can significantly improve bacterial sticking efficiency in porous media by modifying hydrophobicity of solid surfaces. Finally, the developed imaging technique was used to monitor biofilm development under a constant pressure gradient in a two-dimensional flow field. Results revealed that in porous media with small pore sizes and low permeabilities, biofilm grows predominantly in upstream regions toward the nutrient source and against the fluid flow, whereas in porous media with coarse pore sizes and elevated permeabilities, biofilm primarily disperses in the downstream direction, in the same direction as the fluid flow, but away from the nutrient source. Observed differences in growth patterns could be explained by considering the pore size distribution in a given medium.
Description
Keywords
Engineering, Hydrology, Engineering--Chemical
Citation
Bozorg, A. (2013). Interactions between Biofilm Growth and Fluid Flow in Porous Media (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26598