Stabilization of waste bottom ash generated from hazardous waste incinerators

Stabilization of bottom ash generated from hazardous waste incineration by the means of solidification was assessed by applying three different amounts of cement admixture (10%, 20% and 30%) and four distinct solidification periods (1 day, 4 days, 7 days and 28 days) in order to decrease the amount of harmful elements or compounds in the waste. Complex assessment of all the observed parameters was performed both according to the EU standard 2003/33/EC for waste acceptable at landfills for hazardous waste and by using ecotoxicological test on the freshwater algae Desmodesmus subspicatus. Whilst unmodified bottom ash exceeded the permit limit concentrations, after the solidification, most of the elements was immobilized in the admixture. The growth inhibition of D. subspicatus was, however, found out to be increasing during the process, possibly because the increase of molybdenum in the leachate with the increased cement addition and prolonged solidification period. From all the combinations tested, 30% cement addition and the standard 28 days solidification period appears to be the ideal one.