Experimental investigations of water retention curves of fresh and decomposed municipal solid wastes under multiple drying and wetting cycles

Abstract

Municipal solid wastes (MSWs) disposed in landfills are generally exposed to drying and wetting cycles because of the variation in environmental conditions, decomposition of organics and leachate recirculation. This paper studies the water retention curves (WRCs) of fresh and degraded MSWs under various numbers of drying and wetting cycles with water and leachate exposure. The result indicates that the water retention capacities of MSWs decrease with drying and wetting cycles. The maximum hysteresis between the drying and wetting cycles is observed in the first cycles for all MSW samples. The WRCs of medium to highly decomposed MSWs under drying and wetting cycles are similar to those of soils. The WRCs of fresh MSWs can undergo substantial changes due to the discharge of intra-particle moisture caused by decomposition and compression. For both fresh and decomposed MSWs, the WRCs stabilize after 3 drying and wetting cycles. However, only the MSWs of one initial composition with similar void ratios were investigated. Further research should be conducted to investigate the water retention behavior of MSWs with diverse initial compositions (e.g., food contents) and void ratios.