Electrodialytic removal of heavy metals and chloride from municipal solid waste incineration fly ash and air pollution control residue in suspension – test of a new two compartment experimental cell

• Acidification of residue suspension is faster in the 2 compartment cell.
• pH in residue suspension is the determining factor for remediation success.
• Leaching limiting values can be met for fly ash after electrodialytic remediation.

Municipal solid waste incineration (MSWI) residues such as fly ash and air pollution control (APC) residues are classified as hazardous waste and disposed of, although they contain potential resources. The most problematic elements in MSWI residues are leachable heavy metals and salts. For reuse of MSWI residues in for instance concrete, the aim of remediation should be reduction of the heavy metal leaching, while at the same time keeping the alkaline pH, so the residue can replace cement. In this study a MSWI residues were subjected to electrodialytic remediation under various experimental conditions. Also a newly developed 2 compartment experimental cell was tested. The results show that the pH development in the MSWI residue suspension depended on the type of MSWI residue and the experimental cell type. The acidification of the suspension occurred earlier when using the 2 compartment setup and the acidification of the fly ash occurred earlier than for the APC residue but the highest removal was seen with the 3 compartment cell. The lowest final pH for the fly ash and APC residue was 6.4 and 10.9, respectively. The results showed that the leaching of Cd, Cu, Pb and Zn was reduced compared to the initial heavy metal leaching except when the pH was reduced to a level below 8 for the fly ash. On the other hand, Cr leaching increased by the electrodialytic treatment. Cl leaching from the MSWI residues was less dependent on experimental conditions and was reduced in all experiments compared to the initial levels.