Evaluation of compacted lateritic soil – bacillus coagulans induced calcite precipitate for landfill application using bacterial foraging optimization algorithm

Abstract

Evaluation of compacted lateritic soil – Bacillus coagulans (B.coagulans) induced calcite precipitate for landfill application was carried out using Bacterial Foraging Optimization Algorithm (BFOA). Experimental results were obtained through laboratory tests. Measured soil factors include; Coefficient of permeability (hydraulic conductivity) as a dependent factor and void ratio, bulk density, B. coagulans suspension, pH, Compactive effort, water content relative to optimum, plasticity index, viscosity of microbes and liquid limit as self-determining (independent) factors. GeneXproTools 5.0 software was used to develop the fitness (objective) function used for Bacterial Foraging Optimization (BFO) to predict hydraulic conductivity of treated lateritic soil with B. coagulans suspension density. The fitness function was then integrated using BFO codes in Matlab 2016 version to predict the minimum hydraulic conductivity for a given set of self-determining factors. The result shows a strong association between the predicted hydraulic conductivity values and the measured hydraulic conductivity values in the laboratory using a regressed line with coefficient of determination R=0.85. It is clear from the optimization results that the hydraulic conductivity values and the self-determining variables have strong correlation. The least hydraulic conductivity value of 2.38×10−11m/s which falls below the permissible regulatory value of 1.0×10−9 m/s for landfill application was achieved at 100 iterations. Based on all the optimization results, it is recommended that lateritic soil-B.coagulans mixtures be compacted with 1.20×10−9 - 2.40×10−9 cells/ml B.coagulans suspension density compacted using Britsh standard heavy (BSH) energy at 15.3 % moisture content for landfill application.