Influence Of Key Components Of Incineration Slag On Landfill Stabilization And CH₄ Production And Influencing Mechanism

Landfill and incineration are the main ways of municipal waste disposal.With the increasing proportion of waste incineration treatment in China,the amount of slag produced by the incineration process has also increased year by year.In order to regulate the safe disposal of incineration slag,"domestic waste landfill pollution control standards"（GB 16889-2008）provides that"domestic waste incineration slag can be directly into the domestic waste landfill disposal".In order to investigate the influence of key components of incinerator slag（alkaline substances,ferromagnetic substances）on the characteristics of leachate water quality changes,CH₄ production changes and the succession characteristics of microbial community structure during the mixed landfill process.In this study,by constructing different types of incineration slag mixed landfill bioreactors with domestic waste,the waste control group（CK）,the alkali-rich slag group（5%AL,10%AL）,the iron-rich slag group（5%FM,10%FM）and the virgin slag group（5%BA,10%BA）,respectively.Study the physicochemical properties and bacterial community structure succession pattern of leachate in the mixed landfill process of each system,the changing pattern of CH₄ production and the relationship between the physical and chemical characteristics of leachate and the pattern of CH₄ production.Analysis of the relationship between the community structure succession of methanogenic bacteria,methanogenic metabolic pathways and their abundance and CH₄ production patterns during the mixed landfill process.To elucidate the influence and microbiological mechanisms of key components（alkaline substances,ferromagnetic substances）in slag on landfill stabilization and CH₄ production patterns.The specific conclusions are as follows:（1）The degradation characteristics of leachate water in the process of virgin slag（BA）,alkali-rich slag（AL）and iron-rich slag（FM）with domestic waste in landfills were studied respectively.The results show that:BA,FM and AL all increase the alkalinity of the leachate,alleviating the accumulation of organic acids in the system and helping to accelerate the stabilization process of the waste.Fe²⁺,Ca²⁺,Mn²⁺and Ni²⁺in the leachate showed an overall decreasing trend.The addition of 5%FM was beneficial to the degradation of organic matter,but the addition of 10%FM did not significantly promote the degradation of organic matter.The best removal of complexine-like,tryptophan-like,protein-like and humic acid-like in leachate dissolved organic matter（DOM）was achieved with the addition of 10%BA,and it was better than 10%AL and 10%FM.The stabilization of the landfill system by BA and AL was significantly better at high addition rates than at low addition rates.（2）The change patterns of CH₄ production and its influencing factors in the process of virgin slag（BA）,alkali-rich slag（AL）and iron-rich slag（FM）with domestic waste in landfill were studied.The results showed that:The FM group was more favorable to CH₄gas production than the AL group under the low percentage addition（5%）,but the pro-CH₄ production effect of both was significantly lower than that of BA.The promotion effect of the AL group on CH₄ production was significantly higher than that of the FM group under high percentage addition（10%）,but still lower than that of the BA group.The addition of high percentage of BA was more favorable to the production of CH₄ gas,and the alkaline material in the slag played a key role in promoting it.The CH₄concentration showed a strong positive correlation with leachate p H and a strong negative correlation with VFA,EC,COD,etc.The CH₄ concentration was higher under 10%BA and 10%AL conditions and was more significantly affected by p H.（3）The relationships between the evolution of bacterial communities and their response to the degree of waste degradation in the mixed landfill process of virgin slag（BA）,alkali-rich slag（AL）and iron-rich slag（FM）with domestic waste were investigated.The results showed that:The bacterial community diversity in the CK,5%BA and 5%AL groups showed an increasing trend with landfill time,and the bacterial community diversity in the 10%BA,5%FM,10%FM and 10%AL groups showed an increasing trend with landfill time followed by a decreasing trend.Lactobacillus was the dominant genus in the early stage of landfill,Clostridium was the dominant genus in the middle,late and end stages of landfill.VFA,EC,ORP and COD were the main environmental factors affecting the landfill system,Lactobacillus had the greatest influence on the bacterial community composition in the early stage of landfill,while Clostridium and Clostridium sensu stricto were more associated with the middle,late and end of the landfill.Metabolism,genetic information processes and environmental information processes are the main metabolic pathways based on KEGG primary annotation,and amino acid metabolism and carbohydrate metabolism are the main metabolic pathways based on KEGG secondary annotation.virgin slag and alkali-rich slag enhanced the bacterial population within the landfill layer in the early and middle stages of landfilling.（4）The microbiological mechanisms affecting the change patterns of CH₄production during the mixing of virgin slag（BA）,alkali-rich slag（AL）and iron-rich slag（FM）with domestic waste in landfills were investigated.The results showed that:The diversity of archaea showed a trend of increasing and then decreasing with the time of landfill,and the abundance of archaea reached the maximum in the middle of landfill and the minimum in the late landfill.The dominant genera were Methanobrevibacter,Methanothrix and Methanomassiliicoccus.EC,COD,VFA,ORP and p H were the main environmental factors in the landfill system.The abundance of methanogenic metabolic pathways in the early and middle stages of landfill was much lower than that in the late and late stages of landfill,and the abundance of methanogenic metabolic pathways in the high percentage（10%）addition system was higher than that in the low percentage（5%）addition system,which was basically consistent with the variation pattern of CH₄concentration.The main methanogenic pathways in the early and middle stages of landfill are the H₂ reduction CO₂ methanogenic pathway and the H₂ reduction methyl compound methanogenic pathway.In the late and end stages of landfill,the H₂-reduction CO₂methanogenesis pathway was dominant except for the H₂-reduction CO₂ methanogenesis pathway and the acetic acid cracking methanogenesis pathway in the 10%BA system.