Evolution and Prediction of the Saturated Hydraulic Conductivity of Municipal Solid Waste during Long-Term Biodegradation Experiments

This study presents a novel method for predicting the long-term evolution of saturated hydraulic conductivity (kS) in municipal solid waste (MSW) during biodegradation, based on our experimental studies and data from existing literature. Five large-scale laboratory simulators, filled with real MSW, were operated for 850–1,140 days until complete MSW biodegradation was achieved, enabling simultaneous monitoring of biodegradation and kS. The evolutions of the kS, dry unit weight (γd), total porosity (nt), and drainable porosity (nd) of MSW specimens were measured or calculated. The results showed that during biodegradation, the kS experienced up to 2- and 42-times reductions. Meanwhile, nd decreased considerably, whereas γd and nt remained relatively stable. The kS was further correlated with parameters related to solid skeleton and pore structure (i.e., γd, nt, and nd). Among these parameters, the nd is the best indicator for kS. Using these findings and integrating with data from existing research, a modified Kozeny-Carman model based on nd was developed to predict the kS evolution of individual MSW samples. To enhance its applicability, a straightforward method for estimating model parameters using easily obtained MSW properties was proposed and validated against independent datasets, demonstrating reliable predictions. This study contributes significantly to the design and modeling of MSW landfills and offers valuable insights for managing storage and disposal facilities of other soluble, degradable, and erodible geomaterials.