Electrodialytic remediation of air pollution control residues in bench scale

Air pollution control (APC) residue from municipal solid waste incineration (MSWI) is considered a hazardous waste due to its alkalinity and high content of salts and mobile heavy metals. Various solutions for the handling of APC-residue exist in different regions; however, most commercial solutions are concerned with deposition.

A demand for more environmentally friendly alternatives exists. Electrodialysis could be such an alternative, and the potential is being explored. This work presents a bench scale study of the feasibility of treating APC-residue from a dry system by electrodialysis. A system resembling conventional electrodialysis was designed and adjusted to fit the high solids content feed solution (10% APC residue, 90% water).

Experiments were made in bench scale with raw residue (natural pH > 12), water pre-residue (natural pH > 12), acid pre-washed residue (pH 10), and acid-treated residue (pH 2). Our results show that the soluble fraction of the toxic elements Pb, Cu, Cd and Zn was removed from the feed solution and concentrated in the concentrate solution.

Furthermore, the leaching (leaching test at L/S 2) of these elements was substantially reduced during treatment (fig. 1). Between 57 and 83% of the APC residue was dissolved during treatment. The highest dissolution was seen for acid treated residue and the lowest for water pre-washed residue.