Sand bioconsolidation/biosolidification by microbially induced carbonate precipitation using ureolytic bacteria

This work studies the efficiency of the microbially induced calcite precipitation (MICP) process to consolidate and therefore, improve the strength and stiffness of sand using ureolytic bacteria isolated from different sources in Iraq including alkaline soil, horses barn soil, cows barn soil, wastewater sludge, concrete and agricultural field soil. The results revealed that all isolates formed calcite and were able to bioconsolidate sand efficiently. However, bacteria isolated from cow barn soil (Bacillus sphaericus) induced higher calcium carbonate production compared to other isolated strains. Furthermore, have relatively low penetration distance and higher retention time as a result of the formation of calcium carbonate (calcite) crystals in a sand matrix allowing the sand column to be filled with plugging materials. The results also establish a relationship between strength/stiffness gained from biosolidification sand with an increased amount of CaCO3 precipitations in all isolates and this promotes sustainable soil improvement in geotechnical applications. The presence of calcium carbonate through sand matrix biosolidification was analyzed under SEM-EDX and XRD analysis.