Geotechnical properties of high organic content waste

Abstract

High organic content waste has a significant effect on the physical and hydrological properties of waste. Therefore, understanding the properties of waste is considered key for landfill designers, and operators. This study presents the results of laboratory tests with regard to the physical properties, settlement, compressibility and hydraulic conductivity of different high organic synthetic municipal solid waste (MSW) matters under different loads simulating burial in a landfill. Eight different test samples were tested under compression in saturated and unsaturated conditions using a Rowe cell reactor. The saturated tests were used to examine changes in terms of physical and hydrological properties of MSW in order to obtain an understanding of the effect of organic materials (food waste). The goal of the unsaturated test samples was to investigate leachate produced from waste itself. In this regard, food waste was classified into two different groups: loose bound water (LBW) and strong bound water (SBW).
The results show a significant correlation between organic content and the geotechnical and hydrological properties and compressibility of MSW as the organic fraction of MSW dropped by 20%, 40% and 60%. The results indicated that the amount of water released greatly varied according to moisture content, material structure and type of food waste (LBW and SBW). The relationship between settlement and leachate production has been highlighted in this study.
A conceptual model of the release of bound water in relation to the applied stress of mixed waste run under saturated conditions was developed in this study. The conceptual model spreadsheet consists of two variables, namely, input and calculated variables. The input variables comprise the results obtained from the experimental work using a Rowe cell. Meanwhile, the calculated variables are obtained using equations proposed for the conceptual model to determine the change in food trapped liquid occurring with increased vertical stress. In this regard, a numerical function of the volume fraction of trapped liquid was proposed; this function can be read by the LDAT model. The results obtained from the conceptual model spreadsheet and the LDAT model were compared. The findings showed that the trapped liquid of different high-organic-content waste types has a critical impact on the water released ratio gradient, which increases with the organic fraction in MSW.

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