Stabilized Fly Ash Co-disposed With MSW In Landfill:Leaching Characterastics Of Heavy Metals And Microbial Community Diversity

Municipal solid waste incineration?MSWI?fly ash is enriched in many hazardous substances,such as heavy metals,so it is considered as hazardous waste and must be solidified or stabilized before further disposal,and at some landfill sites,stabilized MSWI fly ash is co-landfilled with MSW.But the leaching behavior of heavy metals and microbial community diversity is not clear when stabilized MSWI fly ash is landfilled with MSW together.In this experiment,the field of anaerobic bioreactor landfill was simulated in order to study the the leaching behavior of heavy metals and microbial community diversity under different ratios?0%,5%,10%,20%?of fly ash stabilized with chelate or phoshate.The main conclusions are as follows:?1?The concentrations of heavy metals were bigger when co-landfilled with chelating stabilized fly ash than with phosphating stabilized fly ash.The leaching behavior of heavy metals can be influenced by the type of stabilized fly ash and the kind of heavy metals,and it will also be different indifferent landfill perids.Only the concentrations of Cr and Cu may meet the standard limit requirement except.?2?There are many factors affect the leaching behavior of heavy metals,such as pH,ORP and concentrations of organic matters of leachate.And the leaching behavior of heavy metals can be influenced more easily in the columns with phosaphate-stabilized flu ash.?3?The microbial community diversity was increased as landfilling time prolongs.On the 40th day,the more the stabilized fly ash was added,the lower the microbial diversity.On day 215,the more chelating-stabilized fly ash was added,the higher the microbial diversity,and the microbial diversity of L10?ratio of phosphating stabilized fly ash is 10%?was lower than L5 and L2 0?ratio of phosphating stabilized fly ash is 10%and 20%,respectively?.On day 40,the bacterial community are mainly composed of Firmicutes and Proteobacteria.On day 215,the dominant bacterial community are more diverse and there are more bacterial of unclassified.Halophilic bacteria and Alkali-resistant bacteria such as Halolactibacillus and Halomonas are increased significantly.Obviously,large number of heavy metals may leach out and exceeding the standard limit regardless of the landfill ratio or stabilization method,especially Pb and Zn.The bacterial community are affected by the ratio of stabilized fly ash,and increased as landfilling time prolongs,especially Halolactibacillus.During the whole process of refuse degradation,the characteristics of pH,COD and NH₄⁺-N leachate were also quite different due to the difference of microbial community structure in different simulated columns,which further led to the differences of leaching behavior of heavy metals from stabilized fly ash.