Stabilization behavior of the three-phase and multi-component system of landfilled waste under aeration: Numerical modeling

Aeration is an effective technology for shortening the landfill stabilization phase. A comprehensive under-standing of waste stabilization under aeration is significant to the design and operation of the aeration system. To address it, a new 3D multi-field model is developed with considerations of nitrification and denitrification processes, transport of leachate solutes, and time-dependent deformations. Validated against a waste-column test and a field test, the proposed model is then used to investigate the stabilization behaviors of gas, liquid, and solid phases in waste, respectively. The results show that 95% of the total organic carbon is discharged via gas with only 1% via leachate, and most of the released nitrogen is dissolved in the leachate in the form of nitrate with approximately 1-7% discharged via gas and 4% via leachate. Based on five selected stabilization indicators, the stabilization process can be divided into (I) aerobic transformation stage, (II) semi-stable stage, and (III) post-stable stage. The demarcation points of stages II and III can be set as the criteria values for the termination of aeration. The characteristics of each indicator will facilitate the evaluation of the stabilization state of landfills in practice.