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Bacterial Activity and Precipitation Heterogeneity during Biomediated Calcite Precipitation for Soil Improvement.

Akimana, Rosa Mystica
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1513381445346889

Abstract Details

2017, Master of Science, University of Toledo, Civil Engineering.
Microbially induced calcite precipitation (MICP) has recently emerged as a potential ground improvement technique, where microorganisms play an active role in catalyzing urea hydrolysis and inducing chemical precipitation of calcite, leading to the reduction of porosity and improvement of strength and stiffness. This ground improvement technique has a great potential in a variety of engineering applications, including bearing capacity boost, geo-hazard mitigation, geological CO2 sequestration, ground remediation and unconventional oil/gas recovery. Despite successful implementations achieved on laboratory scales, there remain many critically unanswered questions as to the predictability and controllability of altered/engineered soil properties, demanding improved understanding of the fundamental mechanisms across multiple scales. The present study focuses on a number of challenges in achieving successful and efficient calcite precipitation. Explored in this thesis are several phenomena related to this aspect: the short effective precipitation distance, clogging of the sand near the injection point, the flushing of bacterial cells out of the system (generally columns), inability to monitor in situ reactions and uneven distribution of biological activity and precipitated calcite. The primary objectives of the present study are: 1) to explore and recommend an injection method that helps reduce/prevent the clogging near injection point 2) to analyze in-situ bacterial survival in the soil throughout the treatment period 3) to monitor calcite precipitation evolution during treatment, and finally 4) to analyze calcite distribution along treated samples. The first part of the experimental study is focused on a series of batch experiments where the bacteria activity and chemical concentrations were monitored during urea hydrolysis and calcite precipitation. It was found that when mixed together, unhindered in the absence of a porous medium, urea hydrolysis and calcite precipitation progressed rapidly, typically taking less than a few hours for most calcite to precipitate. The second part of the experimental study is extended to the MICP in sand. A modified procedure was developed to minimize the possibilities of pre-mature calcite precipitation and clogging near the injection point; this is achieved by delaying the mixing of CaCl2 with the biological medium and resuspending the bacterial cells in a urea and difco nutrient solution. This led to significant improvement; very little to no clogging occurred in the process, allowing the pathways for the continuous fluid flow injected into the sand. As a consequence, it also led to considerable improvement of uniformity of calcite precipitation and a very high chemical efficiency of calcite production.
Liangbo Hu, Ph.D. (Advisor)
71 p.
Engineering
Microbially Induced Calcite Precipitation, Urease Activity, Ground Improvement, Calcite Distribution

Recommended Citations

Citations

  • Akimana, R. M. (2017). Bacterial Activity and Precipitation Heterogeneity during Biomediated Calcite Precipitation for Soil Improvement. [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1513381445346889

    APA Style (7th edition)

  • Akimana, Rosa Mystica. Bacterial Activity and Precipitation Heterogeneity during Biomediated Calcite Precipitation for Soil Improvement. 2017. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1513381445346889.

    MLA Style (8th edition)

  • Akimana, Rosa Mystica. "Bacterial Activity and Precipitation Heterogeneity during Biomediated Calcite Precipitation for Soil Improvement." Master's thesis, University of Toledo, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1513381445346889

    Chicago Manual of Style (17th edition)

toledo1513381445346889
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This open access ETD is published by University of Toledo and OhioLINK.