Effects of different types of municipal solid waste incineration slag on landfill stabilization and related microbiological mechanism

Municipal solid waste incineration slag has the potential to accelerate the stabilization of landfills, but the effects of key slag components (i.e., alkaline substances and ferromagnetic substances) on the landfilling process have not been systematically studied. Therefore, landfill bioreactors containing different types of incineration slag, including a control group (CK), raw slag (RS), iron-rich slag (FM), and alkali-rich slag (AL), mixed with refuse at 5% and 10% ratios, were established. The results showed that the addition of RS was superior than FM and AL in accelerating refuse degradation, and the degree of stabilization was significantly better at a high slag addition ratio (10%) than at a low ratio (5%). Addition of 10% RS was most effective in DOM removal in the leachate, which was mainly because the raw slag had a high content of alkaline substances (46.78%) and a relatively low content of ferromagnetic substances (7.01%). The addition of RS and AL increased the bacterial population in the early and middle stages of landfilling, but the addition of 10% FM resulted in a decrease in bacterial population. The dominant genus was Lactobacillus in the early stage of landfilling, while Clostridium and Petrimonas were the dominant genera in the late and final stages of landfilling in the slag addition systems, and alkaline substances played a vital role in the succession of bacterial community. The addition of slag promoted the abundance of amino acid metabolism and carbohydrate metabolism pathways involved in refuse degradation.