Comparative Study on the Sand Bioconsolidation through Calcium Carbonate Precipitation by Sporosarcina pasteurii and Bacillus subtilis

To investigate potential implications of microbial activity on sand bioconsolidation and subsurface environments, two ureolytic strains, Sporosarcina pasteurii and Bacillus subtilis were tested for the production of calcium carbonate (CaCO3). Laboratory experiments with monoculture S. pasteurii (column 1) and coculture S. pasteurii-B. subtilis (column 2) were conducted to determine urea and calcium chloride reactivity and volumetric carbonate formation. Both columns were able to consolidate sand, whereas, column 1 induced greater CaCO3 precipitation. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed two columns with different mineralogy with calcite, and vaterite formation. Column 1 showed rhombohedral and trigonal crystals morphology, whereas column 2 developed the prismatic calcite and the spherulite vaterite crystals might be due to the differences of the micro-environment caused by the urease expression of these bacterial species. These results indicate the possibility of using those crystals to cement loose sand whereas, highlighted the importance of combining these techniques to understand the geomicrobiology found in the subsurface environments.