Effects of Design Mix and Porosity of Waste-Derived Paste as Landfill Daily Covers on Lead Retardation

Abstract

An innovative waste-derived paste of waste tire chips and paper sludge was proposed for daily cover applications in municipal solid waste landfills. In this study, retardation and transport behaviors of lead (Pb) by the proposed paste were investigated using column tests. Breakthrough curves of 16 specimens at various design mixes and porosities were presented. A one-dimensional equilibrium deterministic transport model was used to fit the transport parameters from the breakthrough curves and to verify the homogeneity of the specimens. Analysis of the effluent concentrations from the column tests displayed a retardation effect for Pb in all cases, with fitted retardation factors ranging from 19.9 to 59.0. Lead retardation by the proposed paste was found to be sensitive to the paste’s porosity and design mix. Early arrivals of solute were observed unexpectedly in columns with high paper sludge content under high packing densities and were attributed to the possible presence of preferential flow paths. The results also suggest that an optimal porosity and design mix for the paste existed with respect to Pb retardation.