Characterization of Physicochemical and Mechanical Properties of Dumped Municipal Solid Waste in Sri Lanka as Affected by the Climate Zone and Dumping Age

Abstract

Due to the rapid increase in population and urbanization, municipal solid waste (MSW) generation is increasing. Sri Lanka, in particular, faces serious difficulties in finding new sites for MSW disposal, due to the lack of available space; therefore, the rehabilitation of existing MSW dumping sites and the extension of their services are required to achieve sustainable urban development. To examine suitable rehabilitation techniques, it is essential to identify the physicochemical and mechanical properties of dumped MSW, fully considering climatic conditions, waste composition, and the time since the waste was dumped. In this study, therefore, the physicochemical and mechanical properties of dumped MSW were investigated; the dumped MSW was taken from existing MSW dumping sites in three climate zones in Sri Lanka, namely the Karadiyana site in the wet zone, Udapalatha in the intermediate zone, and Hambantota in the dry zone, and it was taken at different times after being dumped. The results showed that the waste composition and biodegradation of organic materials affected the physicochemical and mechanical properties of the dumped waste. The measured compaction parameters of the “old” sites at Udapalatha and Hambantota were higher compared to the “new” sites. Compaction parameters at the Karadiyana site, on the other hand, were low, at even >20 years since being dumped, probably due to the high amount of scarcely compacted materials. In direct shear tests, both strain hardening and softening of the waste samples were observed, depending on the difference in vertical stress. Based on the Pearson correlations among measured physicochemical and mechanical parameters, it was found that the loss on ignition (LOI) would be a good indicator to quickly assess the mechanical parameters of “new” and “old” waste materials, due to the small sensitivities to waste age and climate conditions in Sri Lanka. In particular, LOI correlated well to measured specific gravity and compaction properties, and the r2 values of correlations exceeded |0.80|.