Evaluation of Hydraulic Conductivity of Lateritic Soil Treated with Bacillus Coagulans for Use in Waste Containment Applications

Abstract

AbstractMicrobial-induced calcite precipitation (MICP) is a green and sustainable soil improvement technique where chemical reaction network managed and controlled by microbes alter the engineering properties of the soil. This research focused on evaluating the potentials of Bacillus coagulans for improving the hydraulic property of lateritic soil intended for use in a waste containment facility. Soil samples were treated with Bacillus coagulans at one-third (1/3) pore volume in stepped suspension density of 0, 1.5E + 08, 6.0E + 08, 12.0E + 08, 18.0E + 08 and 24.0E + 08/ml, respectively. Soil samples were prepared at moulding water contents of –2, 0, +2 and +4% relative to optimum moisture content and compacted using the British Standard light (BSL) or standard Proctor energy. Cementation reagent was injected into the soil after compaction by gravity. Results show a marginal decrease in hydraulic conductivity values with increase in Bacillus coagulans suspension density, while it generally increased with increase in moulding water content with a slight decrease at optimum moisture content (OMC). The degree of saturation of the specimens initially increased and thereafter decreased with varying Bacillus coagulans suspension density. However, the degree of saturation increased with moulding water content from –2% to 0% relative to optimum moisture content (OMC) and thereafter decreased. The hydraulic conductivity values of the treated soil did not meet the maximum regulatory 1 × 109 m/s required for its use as liner and cover material in waste containment system. However, higher compaction energy is recommended to achieve the desired result. KeywordsBacillus coagulansDegree of saturationHydraulic conductivityLateritic soilMicrobial-induced calcite precipitation (MICP)