Experimental Investigation of Tailings Sand Solidification Using Indigenous Ureolytic Bacteria Combined with <i>Sporosarcina pasteurii</i>

ABSTRACT Microbially induced carbonate precipitation using Sporosarcina pasteurii is an effective technique for soil improvement. However, heavy metal contaminants in mine tailings inhibit microbial growth and metabolic activity, reducing treatment efficiency and increasing costs. To address this challenge, this study developed a combined biological approach for tailings sand solidification. A biostimulation solution was specifically tailored to activate and enrich indigenous ureolytic microorganisms with high heavy metal tolerance, and these isolates were subsequently coupled with S. pasteurii. The performance of the combined treatment was systematically evaluated against individual bacterial treatments. After seven treatment cycles, the combined approach increased the surface strength by 53.3 % relative to S. pasteurii alone and produced specimens that completely resisted erosion under simulated heavy rainfall, demonstrating a clear synergistic effect. The dual-bacterial system also achieved superior heavy metal stabilization across all treatment rounds. Although microbial community diversity declined following curing, the combined approach was highly cost-effective, requiring only 55.66 % of the cost of the S. pasteurii-only treatment. These results indicate that coupling indigenous ureolytic bacteria with S. pasteurii improves both the mechanical performance and environmental safety of tailings sand while substantially reducing remediation costs.