Performance Assessment of Gravel–Tire Chips Mixes as Drainage Layer Materials Using Real Active MSW Landfill Leachate

Abstract

Potential of clogging for rubber tire chips, gravel and their relative performance for transmitting high strength leachate when arranged in proportionate layers of relative thickness and in random state mixes of various percentage compared to the case of used alone were studied through column experiments. Comparative hydraulic performance of gravel and tire chips in their different combinations with percentage change (reduction) in COD, TSS, Ca-hardness and TDS concentration levels for the real active high strength MSW landfill leachate with time were investigated. Experiments were performed to simulate conditions occurring at the base of all active MSW landfills, in an attempt to replicate reasonably worst case conditions. Results clearly showed that the combinations ds (scrap tire chips layer thickness)/dg (gravel layer thickness) = 0.25, 0.50 (arranged by relative thickness) and Ws:Wg = 1:3 (25 % tire chips:75 % gravel; mixed by weight friction of each component) were good in term of obtaining initially relatively free drainage. Minor reduction in hydraulic conductivity for fairly longer duration, due to lesser clogging and small reduction in COD, TSS and Ca-hardness concentration levels were observed for these combinations. These experimental findings may prove to be very useful for the proper design, long term performance and service life of all tire chips–gravel made drainage layers of all the active MSW landfill leachate collection and removal systems.