Evaluation of using municipal solid waste compost in landfill closure caps in arid areas

Covering systems of landfills involve partial or complete isolation of waste materials from the surrounding environment. Available materials and management practices in arid areas may not be adequate to fulfill the requirements of the current regulations. This study investigates the performance of a native soil available in arid areas blended with municipal solid waste compost as an infiltration barrier layer in landfill closure cap design. Tests to determine different physical properties of the produced mixture were conducted and the optimum blend of minimum hydraulic conductivity was selected. The effect of organic decomposition and thermal fluctuation prevailing in the arid environment upon the changes in hydraulic conductivity was evaluated experimentally. The developed mixture of 60% compost and 40% native soil was found to have a hydraulic conductivity 4.0 to 6.0×10−9 m/s. Other tests were conducted to examine the effect of organic decomposition and thermal fluctuations upon the hydraulic conductivity. From the hydraulic performance viewpoint, it was concluded that the developed mixture is an alternative. Some precautions are still needed in that case to eliminate the potential emission of gases from the cover material, anticipated settlement during the active stage of biological degradation, and the increased possibilities of deterioration related to burrowing animals.