Procédé optimisé de décontamination des cendres volantes d'incinérateur de déchets municipaux : enlèvement et récupération des métaux (Cd, Pb, Al, Zn) avec recirculation des lixiviats traités.

Fly ashes produced by the incineration of municipal solid wastes are usually considered as hazardous wastes. The objective of the present study was to demonstrate the feasibility of a closed circuit decontamination process. The latter includes the reuse of treated process effluents and leads to the production of treated ashes that respect the toxicity characteristic leaching procedure (TCLP). The process should also reduce the production of metallic hazardous wastes and the operating costs. The results show that the process removes 70 ± 3% Cd and 18 ± 4% Pb from fly ashes during the chemical leaching (alkaline and acid) steps. The optimized process generates two types of metallic wastes. The first, representing 13 kg/tct (tons of treated ashes), is a nonhazardous waste produced during the nucleation–precipitation step at pH = 5. The second is classified as hazardous waste and is produced subsequently by precipitation at pH = 7. The production of this metallic hazardous waste is estimated at 29 kg/tct. The treated fly ashes respect the three leaching tests performed in this study, including the TCLP. Significant decreases in the water consumption (91%) and of chemicals used (12%) have been realized, in comparison with a reference decontamination process. These improvements result in a 36% decrease of the operating costs. [ABSTRACT FROM AUTHOR]