Chemistry and mineralogy of municipal solid waste incinerator bottom ash

Abstract: A petrographic study was conducted on a suite of bottom ash samples from 28 municipal solid waste incinerators in Switzerland. Chemical and mineralogical nalyses of bottom ash from waste combustors with comparable t chnology show similar major oxide composition. A significant decrease of SiO2 was observed in comparison tothe chemi-cal composition ofbottom ash from 10 years ago. Incontrast to major oxide contents, heavy metal concentrations vary significantly in the bottom ash samples, but without any corre-lation to the type of input waste or plant operating conditions. Similar types and contents of crystalline phases were observed in all samples. The content of newly formed melilite increases with decreasing bulk Si/Ca ratio, indicating that he type of Ca-Mg-Al-silicates crystallizing during incineration and cooling follow petrogenetic rules. A considerable recy-cling potential for ferrous and non-ferrous metals was identified in the bottom ash. Opti-mized mechanical metal separation technologies could reduce the waste volume, heavy metal content, H2 production, and exothermic reactions of the bottom ash in landfills and might be economically viable. The objectives of municipal solid waste (MSW