Heavy metals chemical speciation and environmental risk of bottom slag during co-combustion of municipal solid waste and sewage sludge

Incineration of sewage sludge (SS) in waste incinerators is one of the main ways of SS disposal. In order to reuse the incineration bottom slag, chemical speciation and environmental risk of heavy metals of bottom slag during co-combustion of municipal solid waste (MSW) and SS should be evaluated. When co-combusted with SS, the proportion of mild acid-souble fraction of Cr, Cu and Zn in the bottom slag decreased, the proportion of reducible fraction and residual fraction increased. As for As, with the increase of sludge blending ratio, the proportion of mild acid-souble fraction increased, and the proportion of oxidizable fraction decreased rapidly. The degree of soil contamination by As and the ecological risk of As of MSW combustion bottom slag increased when co-combusted with SS, while that of Cr, Cu, and Zn decreased. Fitting formulas between environmental index of bottom slag and combustion condition were giving.