Chemical Stabilization of Fly Ash from Medical Waste Incinerators

Abstract

Fly ash from Medical Waste (MW) incinerators contains many toxic materials and requires appropriate treatment. In this work, a procedure for the stabilization of a fly ash produced by a MW incinerator is proposed. Firstly, a detailed characterization of the fly ash as received is presented. The European standard leaching test EN 12457/2 (2002) was used for the fly ash classification, and according to the results, the leachate concentration of Pb, Total Dissolved Solids (TDS), chloride and fluoride ions, exceeded the legal limit values for non-hazardous waste landfilling. A treatment method involving two processes, i.e., phosphoric acid stabilization followed by water washing, was applied for the stabilization of the MW fly ash. This method has been successfully applied for the stabilization of Municipal Solid Waste Incineration (MSWI) fly ash, and was modified in this study in order to be used for Medical Waste Incineration (MWI) fly ash treatment. Two modifications of this method were examined in order to effectively stabilize the ash and produce process wastewater with low heavy metal content. The use of 10% w/w phosphoric acid (acid to ash ratio) followed by water washing with a Liquid to Solid (L/S) ratio equal to 3:1 L kg−1 was found to successfully stabilize the MWI fly ash and produce a waste that can be disposed of in a non-hazardous landfill. Additional use of phosphoric acid provides no significant improvement of the wastewater quality.