Electrodialytic upgrading of MSWI APC residue from hazardous waste to secondary resource

The aim of this project was to contribute to the development of electrodialytic treatment technology of air pollution control residues (APC) from municipal solid waste incineration (MSWI) to obtain maximal leaching reduction by optimization of treatment time and current density for different types of MSWI APC residues.

The concept idea was in a pilot scale unit to reduce the mobility of toxic elements and salts by electrodialytic treatment enough for the residual product to constitute an environmentally safe resource for substitution of virgin resources in construction material e.g. for substitution of cement or fillers in concrete.

In general leaching could not be reduced by optimizing current density and treatment time in the pilot scale stack treatment unit, as hypothesized, even though there was evidence of dependency on current density for e.g. zinc, this was not true for most elements, and it was clear that experimental conditions and pre-treatments affected different target elements differently.

Statistical analysis of the results revealed that the final pH was the major parameter determining leachability. The robustness of the stack setup proved to be very limited. At several occasions during the project, the diluate spacers clogged, and areas with high resistance and heat development evolved.

Membranes burned and had to be changed. Because the results of the pilot scale stack experiments did not give the anticipated results and tools for optimized up-scaling, instead laboratory investigations were made on the influence of different membrane brands and influence of different experimental setups.