Geotechnical Properties of Municipal Solid Waste Subjected to Leachate Recirculation

Abstract

This paper compares the geotechnical properties of fresh municipal solid waste (MSW) to landfilled MSW obtained from a bioreactor landfill. Fresh MSW samples were collected from the working face of Orchard Hills Landfill. Landfilled MSW (15-19 months old, subjected to intermittent very low flow leachate recirculation for a year) samples were recovered from a borehole located near a multi- level horizontal leachate recirculation system in the same landfill. Laboratory testing was performed on shredded samples to determine the variation in in-situ moisture content, organic content, biochemical methane potential (BMP), specific gravity, density, hydraulic conductivity, compressibility, and shear strength properties of fresh as well as landfilled MSW. In-situ dry gravimetric moisture content of fresh MSW was around 44% and landfilled MSW varied between 21-43%. Organic content of the fresh MSW was 76% whereas degradation and presence of other components in landfilled MSW resulted in organic content between 62-68%. Due to the presence of finer particles, reconstituted dry density of landfilled MSW was 601-712 kg/m 3 whereas fresh waste was 515 kg/m 3 . For confining pressure greater than 69 kPa, both fresh and landfilled waste possessed similar hydraulic conductivity. Compressibility test results showed higher strains for fresh MSW than for the landfilled, with compression index of 0.28 for fresh and 0.22 for landfilled MSW. Based on direct shear testing, shear strength properties for fresh MSW were: c�=47 kPa and ��=29 0