Transferring characteristics of heavy metals
during co-incineration of municipal sewage sludge and solid waste

 Co-incineration tests of a synthetic house hold waste with sewage sludge were carried out in a lab-scale tubal incinerator and bottom ash and fly ash samples were collected. The sampled ashes were characterized for the concentration and leaching ability of Cu, Pb, Zn, Mn, and Ni. Furthermore, the calculation of thermodynamics equilibrium was conducted to identify the transfer of heavy metal elements into flue gas. The analyses show that the presence of sewage sludge greatly enriches the heavy metal element content in the bottom ash and fly ash in a decreasing order of Zn, Pb, Ni, Mn, and Cu. With the addition of organic Cl, the heavy metals in fly ash are increased, especially for Zn. Meanwhile, the fly ash from the tests with sewage sludge added presents toxicity due to the marked Zn and Pb leaching that exceeds the limit values legislated by National Environmental Law for Hazardous Solid Waste. Discrepancies between model predictions and experimental results are evident, which indicates that considering the kinetics，oxygen content in the incinerator and possible chemical reactions between these heavy metal elements and other elements in the formation of metal chloride gaseous species is needed.