Coenrichment characteristics of phosphorus and heavy metals in incinerated sewage sludge ash

The heavy metal problem during phosphorus recovery from sewage sludge cannot be ignored. Accordingly, this study investigates the effect of the form and content of phosphorus on the behavior of heavy metals (specifically, Cu, Zn, Pb, and Cd) in sewage sludge incineration to determine the optimum condition for heavy metal enrichment in ashes. The experiment is performed in a laboratory‐scale furnace with phosphate additives at 750–950°C to analyze the heavy metal content in sewage sludge ash (SSA). The crystalline phase is analyzed using X‐ray diffraction to explore the mechanism of phosphorus immobilized heavy metals. The morphology is analyzed by scanning electron microscopy to investigate the effect of surface structure difference caused by different temperatures on heavy metal volatilization. Phosphorus significantly affects Zn, Pb, and Cd but not Cu. P 2 O 5 and KH 2 PO 4 have more obvious effects than (NH 4 ) 3 PO 4 and Ca 3 (PO 4 ) 2 on heavy metal immobilization. The additive (e.g., Ca 3 (PO 4 ) 2 ) could increase SSA melting point and observably improve volatilization of Zn at 950°C. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1027–1034, 2016