ABSTRACT
Landfill disposal or reutilization of untreated municipal solid waste incineration (MSWI) ash residues namely incineration bottom ash (IBA) and incineration fly ash (IFA) could pose detrimental environmental effects including groundwater pollution due to leaching of toxic heavy metals. This chapter critically analyzes the recent developments in literature on physicochemical, thermal and biological methods for removal and immobilization of heavy metals from MSWI ash. The physicochemical techniques, namely screening and magnetic separation, water washing, weathering/aging, chemical leaching and solidification/stabilization, and thermal treatments including vitrification, melting and sintering have been applied for metal removal/ash stabilization. In biological leaching, fungus (Aspergillus niger) and iron- and sulfur-oxidizing bacteria are widely used for metal mobilization. The major pathways for metal mobilization include acidolysis, redoxolysis and complexolysis, whereas biosorption, redox reaction and complex formation facilitate heavy metal immobilization. Environmental factors namely ash properties and leaching conditions considerably influence heavy metal leaching characteristics. Reutilization of MSWI ash for construction and geotechnical/geo-environmental applications is highly encouraged which would help to increase lifespan of landfill site and reduce consumption of natural resources. Overall, physicochemical and/or biological methods can be employed for treatment of MSWI ash prior landfill disposal or reutilization to protect public health and environmental ecosystems including groundwater.
