Physical and chemical characterization of ashes from a municipal solid waste incinerator in China

In this study we analyzed the characteristics of bottom and fly ashes from a municipal solid waste incinerator in China. The physical properties of particle size distribution and morphology were evaluated. At the chemical level, the chemical composition, heavy metal leaching behavior and BCR sequential extraction procedure (the Community Bureau of Reference, now the European Union 'Measurement and Testing Programme') were determined. The main mineralogical crystalline phases in raw and leached bottom and fly ashes were also identified. For the bottom ashes, the concentration of heavy metals showed a slight decrease with an increase in particle size, and most of the heavy metal concentrations in fly ashes were higher than those in bottom ashes. The results of the toxicity characteristic leaching procedure indicated that, among the metals, the concentrations of lead (Pb) and copper (Cu) in fly ash leachate exceeded thresholds, while the concentrations of studied heavy metals in bottom ash leachate were all below the regulatory limit. The BCR results indicated that more easily mobilized forms (acid exchangeable) were predominant for cadmium and zinc; in contrast, the largest amount of Pb, Cu and manganese were associated with iron/manganese oxide, organic matter/sulfide fractions, or were residual.