Abstract :
At TNO a feasibility study has been carried out into the possibilities of removing a number of easily leachable elements from MSWI fly ash. The aim of this study was to find a way to useful application of MSWI fly ash (after treatment) as a road base construction material. A combination of a slight washing step and a stabilization/solidification step with cement and other additives appeared to be convenient to meet the severe standards of the Dutch Building Materials Decree. The slight washing step removes more than 90% of the cadmium and chloride that were originally present. Over 50% of zinc and sulphate are removed. The remaining solid material (approximately 70% of the original quantity) could be easily processed into a bound road foundation layer, adding some 20% cement and other additives. The leaching characteristics of the stabilized material meet the most severe standards of the future Building Materials Decree in The Netherlands. This means that the material may be applied without any provisions. In contrast, stabilized but unwashed MSWI fly ash could not even meet the less severe standards. A global cost estimate shows that, at least for the Dutch situation, the processing costs of the combination (washing, processing of the washing liquor and stabilization) equal the costs for disposal of MSWI fly ash.
