Browsing by Author "Connolly, James Martin"

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Appendix C: Raw and thresholded images relating to Chapter 5 [dataset]
(2015-04) Connolly, James Martin
This dataset constitutes Appendix C: Raw and thresholded images relating to Chapter 5 of "Biofilm-induced carbonate precipitation at the pore-scale." To download the dataset using FTP, please use this link: ftp://scholarworks:scholarworks@dtn.rci.montana.edu/10.15788/
Biofilm-induced carbonate precipitation at the pore-scale
(Montana State University - Bozeman, College of Engineering, 2015) Connolly, James Martin; Chairperson, Graduate Committee: Robin Gerlach; Robin Gerlach was a co-author of the article, 'Microbially induced carbonate precipitation in the subsurface: fundamental reaction and transport processes' in the book 'Handbook of Porous Media, 3rd Ed.' which is contained within this thesis.; Megan Kaufman, Adam Rothman, Rashmi Gupta, George Redden, Martin Schuster, Frederick Colwell and Robin Gerlach were co-authors of the article, 'Construction of two ureolytic model organisms for the study of microbially induced calcium carbonate precipitation' in the journal 'Journal of microbiological methods' which is contained within this thesis.; Benjamin Jackson, Adam P. Rothman, Isaac Klapper and Robin Gerlach were co-authors of the article, 'Estimation of a biofilm-specific reaction rate: kinetics of bacterial urea hydrolysis in a biofilm' submitted to the journal 'NPJ biofilms and microbiomes' which is contained within this thesis.; Johannes Hommel and Robin Gerlach were co-authors of the article, 'Reactive transport and permeability reduction in a synthetic 2D porous medium with biofilm-induced carbonate precipitation' which is contained within this thesis.
There are many methods available to decrease permeability in the subsurface but one that has been the subject of much research over the last decade is microbially-induced carbonate precipitation (MICP). In this process, microbial activity is promoted that increases pore water alkalinity. When calcium or other divalent cations are supplied to the system, solid carbonate minerals can form which occupy pore space and can decrease permeability. Permeability reduction can also come from microbial biofilms forming in the pore space. The goal of the work presented in this dissertation is to understand how pore space is affected, both physically and chemically, by biofilms and the precipitates that they can form. Fundamental research presented here is intended to inform ongoing application-based research and development. Previously it has been a challenge to image MICP at high resolution without the use of destructive techniques. To overcome that obstacle, a fluorescently-tagged bacterium capable of urea hydrolysis-driven MICP was constructed. Biofilms were grown in two-dimensional microscale porous media reactors and allowed to precipitate calcium carbonate under varied conditions. These reactors were imaged noninvasively using confocal microscopy so that both biofilms and carbonate minerals could be resolved at micrometer resolution. Image analysis was utilized to quantify how much pore space was occupied by the biofilm and minerals in order to estimate porosity reduction. Finally, pore-scale reactive transport modeling was utilized in order to estimate local concentrations within the reactors. The results show that the extent to which the porosity and permeability of the porous medium was decreased depended on when the calcium was added to the system. Also, periods of low flow were found to decrease porosity and permeability to a greater extent. This result adds to the evidence that a pulsed flow injection strategy may be most effective for permeability reduction via MICP in the subsurface. Additionally, reactive transport modeling predicts a heterogeneous mineral saturation environment at the pore-scale which highlights the challenge of predicting precipitation behavior in Darcy-scale reactive transport models.