Speaker
Description
Biofilms are nearly ubiquitous in both natural and engineered subsurface systems, with relevance to processes ranging from groundwater contamination to thief zone remediation. The interaction between biofilms and permeable media is well-understood to be bidirectional: just as biofilm accumulation is mediated by both mass transport considerations and the physical stresses associated with fluid flow, biofilms can also significantly impact mass transport and fluid flow. As such, understanding and predicting biofilm behavior in biofilm-rock systems requires us to capture both flow through the rock and the associated advective transport as well as diffusive transport within both the rock and, potentially, the biofilm. Microfluidic experiments and modeling studies have significantly advanced our understanding of such systems. At the same time, some attributes of natural systems, such as mineral surface properties and heterogeneity in pore structure, are challenging to capture with these tools.
Here, we illustrate how solute diffusion through natural rock matrices of different porosities can affect, and be affected by, biofilm growth. We also explore the impact of matrix porosity on the efficacy of fracture sealing via ureolytic microbially-induced carbonate precipitation (MICP). Building upon recent advances in real rock microfluidics, in which natural rock samples are incorporated into microfluidic devices, we position porous rock chips between two flow channels. This setup mimics two fractures separated by a porous rock matrix. Through the use of conservative tracers, we quantify the diffusive flux through the porous matrix before, during, and after biofilm cultivation in one channel. We combine this experimental setup with non-destructive X-ray computed tomography to qualitatively compare solute transport through different matrices and at different stages of biofilm growth. Biofilm morphology and resistance to shear stress are found to depend on both matrix porosity and heterogeneities inherent to the pore structure of natural rocks. When urea-hydrolyzing biofilms are used to carry out carbonate precipitation, these effects may be even more pronounced.
| Country | United States |
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