The Effect of Bacteria-to-Calcium Ratio on Microbial-Induced Carbonate Precipitation (MICP) under Different Sequences of Calcium-Source Introduction

Abstract

To explore the effects of the introduction order of calcium sources and the bacteria-to-calcium ratio on the microbially induced calcium carbonate precipitation (MICP) product CaCO3 and to achieve the regulation of CaCO3 crystal morphology, the mineralisation products of MICP were compared after combining bacteria and calcium at ratios of 1/9, 2/9, 3/9, 4/9, 5/9, and 6/9. A bacterial solution was combined with a urea solution in two calcium addition modes: calcium-first and calcium-later modes. Finally, under the calcium-first addition method, the output of high-purity vaterite-type CaCO3 was achieved at bacteria-to-calcium ratios of 2/9 and 3/9; under the calcium-later addition method, the output of calcite-type CaCO3 could be stabilised, and the change in the bacteria-to-calcium ratio did not have much effect on its crystalline shape.

Synergistic biocementation: harnessing Comamonas and Bacillus ureolytic bacteria for enhanced sand stabilization

“…We observed that “B2&B11” at 30 °C displayed a peak pattern at 29.3°, which was not observed for any other samples; this emphasizes the synergetic calcite precipitation and potentially a structural prominence within the sand. Previous studies also observed calcite in their sand experiments (Lv et al 2023 ; Sharma et al 2021 ; Zhao et al 2024 ; Ma et al 2022 ).…”

“…Cylindrical crystals are elongated with parallel sides and rounded ends. Several previous studies have observed these shapes in calcite crystals during MICP processes (Wang et al 2024a ; Li et al 2023b ; Zhao et al 2024 ). We found that a combination of B2 & B11 at 14 ± 0.6 °C produced cylindrical crystals (Fig.…”

“…This result underscores the importance of temperature and bacterial synergies in sand cementation. Notably, the size variance of these bacteria may contribute to this superior cementation, enabling them to infiltrate pores of different sizes and effectively reduce permeability, as suggested by (Bu et al 2022 ; Baek et al 2023 ; Zhao et al 2024 ). Nutrient sharing and cross-feeding interactions among bacterial species may enhance overall metabolic efficiency and substrate utilization.…”