Microbially induced calcium carbonate precipitation (MICCP) is considered a novel eco-friendly technique to enhance the structural properties of cementitious-based material. Maximum studies have emphasized using ureolytic bacteria to improve the durability properties of building structures. In this study, the role of photoautotrophic bacteria Synechocystis pevalekii BDHKU 35101 has been investigated for calcium carbonate precipitation in sand consolidation, and enhancing mechanical and permeability properties of cement mortar. Both live and UV-treated S. pevalekii cells were used to treat the mortar specimens, and the results were compared with the control. The compressive strength of mortar specimens was significantly enhanced by 25.54% and 15.84% with live and UV-treated S. pevalekii cells at 28-day of curing. Water absorption levels were significantly reduced in bacterial-treated mortar specimens compared to control at 7 and 28-day curing. Calcium carbonate precipitation was higher in live-treated cells than in UV-treated S. pevalekii cells. Calcium carbonate precipitation by S. pevalekii cells was confirmed with SEM-EDS, XRD, and TGA analysis. These results suggest that S. pevalekii can serve as a low-cost and environment friendly MICCP technology to improve the durability properties of cementitious materials.
Due to anthropogenic activities, heavy metals such as cadmium (Cd) and arsenic (As) are one of the most toxic xenobiotics contaminating water, thus, affecting the human health and environment. The objective of the present investigation was to study the effect of ureolytic bacteria Bacillus paramycoides – MSR1 for the bioremediation of Cd, and As from contaminated water. The B. paramycoides showed high resistance to heavy metals of Cadmium and Arsenic with minimum inhibitory concentration of 12.84 µM and 48.54 µM, respectively. The urease activity and calcium carbonate (CaCO3) precipitation was evaluated by bacteria in the presence of different concentrations of Cd and As. High removal rates for cadmium (93.13%) and arsenic (94.25%) were observed after a period of 168 hours. Microstructural analysis revealed formation of calcium carbonate in the form of calcite by the bacteria and EDS further confirmed the presence of heavy metal ions in the calcium carbonate precipitates. The results demonstate removal of Cadmium and Arsenic by microbially induced calcium carbonate precipitation to be promising technique for decontamination of water.
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