Urease-driven CaCO3 production by Bacillus megaterium RB-05 for application in sand stabilization

In this study, growth and enzyme production of Bacillus megaterium RB-05 was achieved at varying parameters such as temperature, incubation time, pH, carbon source and nitrogen source. Naturally occurring sand with 97% quartz was utilized as the matrix for bacterial growth and CaCO₃ precipitation. The estimation of CaCO₃ precipitation was done through gravimetric analysis and CaCO₃ deposition was detected through EDX and SEM analysis. Furthermore, sand stabilization was determined through Drained triaxial tests. The results obtained showed maximum bacterial growth and urease activity at pH 7, 35⁰C temperature and 48 h incubation time. Bacteria showed maximum growth with glucose as carbon source however, significant urease activity was observed with both glucose and maltose. Optimum bacterial growth was observed with ammonium chloride as the nitrogen source however, maximum urease activity was observed with ammonium sulphate. CaCO₃ precipitation of treated sand showed a linear relation between CaCO₃ precipitation with urease production. The EDX and SEM analysis showed CaCO₃ deposition between sand particles and on the surface. Furthermore, the stress response of sand showed enhanced sand strength at maximum CaCO₃ precipitation. The obtained results show the link between urease production, CaCO₃ precipitation, and sand stabilization by MICP. High urease activity influences CaCO₃ precipitation in the soil followed by enhanced soil strength. However, the positive results were obtained in reactor environment, further studies are required to make the technique applicable.