BACTERIAL SYNERGY FOR ENHANCED TAILING SAND SOLIDIFICATION VIA MICP

Abstract

This study proposes a synergistic microbially induced carbonate precipitation (MICP) approach combining Sporosarcina pasteurii (SP) with indigenous urea-decomposing bacteria to solidify tailing sand and immobilize heavy metals. First, the bio-stimulation solution for indigenous bacteria was optimized using Plackett-Burman design and Central Composite Design. Subsequently, a comparative analysis was conducted among three treatment methods (bio-stimulation alone, SP alone, and the combined approach) over 4, 7, and 10 treatment cycles. Evaluation metrics included surface strength, toxicity characteristic leaching procedure (TCLP) tests, and scanning electron microscopy (SEM) analysis. Experimental results indicated that the optimized indigenous culture achieved a urease activity of 6.6 mmol/L urea/min. After 7 treatment cycles, the combined solidification method yielded a surface strength of 1188 kPa, which was 5.3 times that of bio-stimulation and 1.5 times that of the SP method. Regarding environmental safety, the combined method significantly reduced the leaching concentrations of Fe, Zn, and Cd by 89.2%, 72.5%, and 87.6%, respectively, compared to untreated samples. SEM analysis revealed that the combined approach generated larger, more numerous calcite crystals with a flaky arrangement that tightly filled inter-particle pores. Furthermore, the economic analysis demonstrated that the combined method reduced material costs to $23.79 per cycle/m², representing only 55.6% of the cost of the traditional SP method. This integrated strategy offers a mechanically robust, cost-effective, and environmentally sustainable solution for tailing sand remediation.