Microbially Induced Calcite Precipitation for Improving the Geoenvironmental Performance of Landfilled Mined Soils
摘要
The reuse of soil-like material (SLM) recovered from legacy municipal solid waste landfills presents significant challenges due to its poor geotechnical properties and elevated concentrations of heavy metals. This study investigates the potential of Microbially Induced Calcite Precipitation (MICP) using Bacillus Pasteurii to enhance the geotechnical strength and reduce the environmental risk associated with SLM. While MICP has been widely studied for synthetically contaminated soils, its application to heterogeneously contaminated landfill-mined soils remain largely unexplored. SLM was subjected to the MICP treatment for 5, 10, and 15 days. Comprehensive evaluations were conducted, including unconfined compressive strength tests, permeability, heavy metal analysis, leaching tests, and microstructural observations using scanning electron microscopy. Results showed a significant increase in soil cohesion from 87 kPa in the untreated sample to 158, 178, and 197 kPa after 5, 10, and 15 days of treatment, respectively. A marked reduction in hydraulic conductivity, from 1.6 × 10−5 to 3.5 × 10−⁷ cm/s, was also observed, attributed to calcium carbonate (CaCO3) precipitation that filled the pore spaces. Heavy metal concentrations were substantially reduced post-treatment, with maximum reductions of 51.95% (Cd), 61.36% (Cr), 58.10% (Cu), 50.79% (Ni), 35.81% (Pb), and 56% (Zn), demonstrating effective immobilization through the MICP. SEM analysis confirmed the development of a denser, calcite-bonded microstructure. Overall, the study highlights MICP as a promising sustainable technique for enhancing the reuse potential of landfill-derived SLM. The findings offer a pathway for the stabilization and valorisation of secondary raw materials, contributing to environmentally responsible landfill mining and resource recovery practices.