Variability in the Solid Particle Density and Its Influence on the Corresponding Void Ratio and Dry Density: A Case Study Conducted on the MBT Reject Waste Stream from the MBT Plant in Marišćina, Croatia

Abstract

In this study, a functional relationship between the solid particle density (ρs), void ratio e, and dry density (ρd) of mechanically and biologically treated (MBT) municipal solid waste (MSW) was examined. In total, 60 waste specimens were tested with an air pycnometer device and corresponding triplets (e, ρd,and ρs) of values were obtained. In addition, a long-term oedometer test with an allowed decomposition process was also conducted. Based on the obtained results, the variability in the solid particle density caused by heterogeneity and decomposition, as well as its influence on the corresponding void ratio and dry density values, were critically evaluated. The obtained results showed that the variability in the solid particle density caused by waste heterogeneity had a significant influence on the initial void ratio value. Furthermore, the obtained results also showed that the change in the solid particle density, caused by the degradation process, had a significant impact on the final void ratio and dry density values. In addition, an empirical relationship, ρd=fe, was proposed. The proposed function allows a landfill operator to establish the corresponding dry density at an arbitrary chosen void ratio, and vice versa, without having the exact knowledge of the corresponding solid particle density value.