CFD Modeling of Anaerobic-Aerobic Hybrid Bioreactor Landfills

Anaerobic-aerobic hybrid bioreactor landfills, operated in a specific way that combines the benefits afforded by both anaerobic and aerobic processes, can significantly enhance the degradation of municipal solid waste (MSW) and the recovery of energy. The present article describes an application of computational fluid dynamics (CFD) to the numerical simulation of subsurface leachate recirculation and aeration systems in hybrid bioreactor landfills. The objective of the study was to model and investigate the hydrodynamic and biochemical behavior within a hybrid bioreactor landfill. The results indicate that the suitable transition time that ensures that the most methane potential has been exploited and that the hybrid landfill changes to aerobic conditions to shorten the stabilization process effectively is when 70-80% of methane potential has been exploited. A relatively small injection pressure is suggested in the initial stage of aeration for MSW with small permeability, and the injection pressure can be raised after the pore pressure dissipates and leachate flows out of landfills smoothly. Results also show that a reasonable method of intermittent leachate recirculation during aeration is to start it when the water content decreases to the minimum value required for the hydrolysis reaction and stop it once the maximum hydrolysis rate is reached and that the configuration of the group-well system has an obvious effect on the leachate volume, whereas it appears to have a relatively small effect on the air volume. (C) 2018 American Society of Civil Engineers.