Evaluation of the Hydraulic Conductivity of Compacted Laterite-Metakaolin Mixtures for Solid Waste Leachate Containment

Abstract

This paper presents the results of a study conducted to investigate the benefits of using metakaolin (MK) with laterite as liner material for containment of municipal solid waste (MSW). Laboratory tests were conducted on laterite specimens treated with MK at concentrations of 0 - 20 % by weight of the soil and compacted using four types of compaction energies. Hydraulic conductivity was determined based on permeation of the compacted laterite - MK mixtures with deionized water (DW) and municipal solid waste leachate (MSWL), respectively. Deionized water was the reference permeant fluid. The results showed that hydraulic conductivity generally decreased with increase in the percentage addition of MK to the soil. From an economic and sustainability point of view, it has been found from the results that 5 % MK can be added to soil and compacted at moulding water content of 14.1 % using the West African Standard (WAS) compaction energy to achieve the regulatory hydraulic conductivity of less than or equal to 1 x 10-9 m/s for compacted soil liner. The natural logarithm of the hydraulic conductivity experimental results were computed and used to develop regression equations for estimating hydraulic conductivity given MK contents and compaction energies. The results of the two-way analysis of variance (ANOVA) test carried out at 5 % level of significance showed that calculated F-statistics are statistically significant and the measured values of hydraulic conductivity compare well with the predicted values. The developed models can therefore be used to give good estimates of hydraulic conductivity of soils having similar properties with the laterite investigated in this study. Therefore, the developed models can be used to give good estimates of hydraulic conductivity of soils having similar properties with the laterite investigated in this study. Keywords ­_ Deionized water, Hydraulic conductivity, Leachate, Metakaolin, Municipal solid waste.