Improvement of the Sand Quality by Applying Microorganism-induced Calcium Carbonate Precipitation to Reduce Cement Usage

This research determines the Microbially Induced Calcium Carbonate Precipitation (MICP) process utilized by the bacteria found in Thailand. Many researchers typically use the high-efficiency MICP bacteria to precipitate calcium carbonate. However, it is only available in some countries, leading to a high import expense. Therefore, the methodology for using the bacteria capable of producing calcium carbonate in Thailand was investigated. The five pure bacteria strains are obtained from the Thailand Institute of Scientific and Technological Research (TISTR), i.e., Proteus mirabilis TISTR 100, Bacillus thuringiensis TISTR 126, Staphylococcus aureus TISTR 118, Bacillus sp. TISTR 658 and Bacillus megaterium TISTR 067. To screen urease production, the bacteria were spread on Christensen's Urea Agar (UA) slant surface via a colorimetric method. All bacteria strains can produce urease enzymes by observing the color changes in the UA. Berthelot's method was used to determine the urease activity. The result shows the bacteria's urease activity: 2389, 1989, 1589, 789, and 589 U/ml, respectively. These directly lead to calcium carbonate production: 3.430, 3.080, 2.590, 1.985, and 1.615 mg/ml, respectively. Despite the bacteria in this research having a low precipitation efficiency compared to the strain used in many research studies, they can improve sand stabilization in 7 days. Proteus mirabilis TISTR 100 was the most stable and effective strain for the MICP process in Thailand. Hence, this research reveals the ability of the local bacteria to bond with the sand particle. Briefly, the improvement of the MICP process in sand stabilization can be improved to reduce imported expenses. In addition, the MICP process can reduce the use of cement in sand stabilization work.