Enhanced MICP for Soil Improvement and Heavy Metal Remediation: Insights from Landfill Leachate-Derived Ureolytic Bacterial Consortium.

Abstract

This study investigates the potential of microbial-induced calcium carbonate precipitation (MICP) for soil stabilization and heavy metal immobilization, utilizing landfill leachate-derived ureolytic consortium. Experimental conditions identified yeast extract-based media as most effective for bacterial growth, urease activity, and calcite formation compared to nutrient broth and brown sugar media. Optimal MICP conditions, at pH 8-9 and 30 °C, supported the most efficient biomineralization. The process facilitated the removal of Cd²⁺ (99.10%) and Ni²⁺ (78.33%) while producing stable calcite crystals that enhanced soil strength. Thermal analyses (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)) confirmed the successful production of CaCO₃ and its role in improving soil stability. DSC analysis revealed endothermic and exothermic peaks, including a significant exothermic peak at 444 °C, corresponding to the thermal decomposition of CaCO₃ into CO₂ and CaO, confirming calcite formation. TGA results showed steady weight loss, consistent with the breakdown of CaCO₃, supporting the formation of stable carbonates. The MICP treatment significantly increased soil strength, with the highest surface strength observed at 440 psi, correlating with the highest CaCO₃ content (18.83%). These findings underscore the effectiveness of MICP in soil stabilization, pollutant removal, and improving geotechnical properties.