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Woodcock, Nicole
Sporosarcina pasteurii , Liquefaction , Microbially induced calcite precipitation , Mine tailings , Dust suppression
The mining industry in Canada is an essential driver of economic growth as societal demands for minerals increases with advances in technology. The waste generated through these mine operations is one of the biggest environmental and safety hazards in the world, with the long-term storage of this waste in tailings dams being a geotechnical and geochemical hazard. The biogeocementation of tailings, using calcite produced by microorganisms to create rock-like tailings deposits, is an attractive concept because a bio-cement can be formed that is durable enough to improve the mechanical behavior of the tailings. In this work, the microorganism Sporosarcina pasteurii was explored for its effectiveness at performing biogeocementation to physically stabilize gold and nickel mine tailings and prevent the wind erosion of gold mine tailings deposits. S. pasteurii was proven to be resilient when exposed to heavy metals at low concentrations, from temperatures of 4 to 31C, and pH values from 2 to 12, indicating S. pasteurii can survive in the potentially harsh conditions of tailings dams. S. pasteurii was then utilized to strengthen undrained gold and nickel tailings. Gold tailings from the Dominican Republic showed a 6.8% increase in shear strength with bacteria inoculation whereas nickel tailings from British Columbia showed an 18% decrease in shear strength. This indicates biogeocementation was successful for the gold tailings and unsuccessful for the nickel tailings which could be due to pore clogging. Finally, S. pasteurii was investigated for its ability to withstand wind speeds up to 15 km/h with the average percent mass lost reduced to 0.46  0.22% from 3.99  0.88%. The most effective application method for biogeocementation was found to be a single application of S. pasteurii followed by a continuous application of nutrient amendments, which has positive implications for field level scale-up. The promise of biogeocementation is demonstrated in this thesis, however, future proof-of-concept work needs to be performed to further characterize the robustness of S. pasteurii and determine its effectiveness in real-world environments, such as tailings dams.
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