Biochemical-thermal-hydro-mechanical coupling model for aerobic degradation of landfilled municipal solid waste

Ventilating solid waste landfills with an oxygen supply can effectively accelerate the degradation of waste, achieve rapid stabilization, and realize the sustainable utilization of landfills. Aiming to understand and verify the aerobic degradation process in landfills, this paper proposed a biochemical-thermal-hydro-mechanical coupling model. The model considers aerobic biochemical reactions, dissolved solute migration, heat transport, two-phase flow, and skeleton deformation. The model was verified by comparison with an in-situ experiment at Jinkou landfill. The results showed the model could accurately represent the observed degradation phenomena during the experiment. The modelling results indicated that the rate of temperature increase and peak temperature of the upper layer, which were lower than those of the middle layer, were affected by heat exchange at the landfill surface. The lowest temperatures occurred near the bottom because of high water content and low oxygen concentrations. The high temperature zone migrated out from the injection well during degradation, reflecting the degradation of degradable organic matter associated with oxygen diffusion rates and aerobic degradation reactions. The initial accumulated settlement value was fast, but slowed and finally stabilized. The surface subsidence also developed from the center around the injection well to the surrounding area, and 70% of the total subsidence occurred within 150 days. This newly developed model provides a theoretical framework for analyzing the multi-field coupling of aerobic degradation of landfilled municipal solid waste (MSW).

Automated summary

This article proposes a biochemical-thermal-hydro-mechanical coupling model to understand and verify the aerobic degradation process in landfills. The model is validated by comparison with an in-situ experiment at Jinkou landfill. The results show that the model accurately represents the observed degradation phenomena. The temperature increase rate and peak temperature in the upper layer are influenced by heat exchange at the landfill surface. The lowest temperatures occur near the bottom due to high water content and low oxygen concentrations. The high temperature zone migrates out from the injection well during degradation, indicating the degradation of degradable organic matter. The initial settlement value is fast, but slows and eventually stabilizes. Surface subsidence develops from the center around the injection well to the surrounding area, with 70% occurring within 150 days.