Maturazione in cumulo all'aperto di scorie pesanti derivanti dall'incenerimento di RSU

Maturation test were carried out on heaps of MSWI bottom ash. The testing was carried out over a sixmonth period in autumn and winter. The aim was to verify, in a pilot plant, the feasibility of the maturation process in relation to a reduction of the release of lead in the aqueous phase within normative limits for landfill. The evolution of the maturation mechanism has been studied in function of time, characteristics of the ashes, and behaviour according to Italian conformity test UNI 10802. To estimate the influence of weather and preparation, heaps were prepared with different heights using both untreated ash and ash after sieving, in both exposed and covered heaps. During the testing period the release of lead, cooper, chlorides, conductivity, pH, alkalinity, calcium, sulphates, DOC were measure. Coupling this test with the meteorological data, it was possible to characterize the physical and chemical mechanisms involved in the maturation and to verify the role of hydroxide carbonatation and its controlling factors. The results have made possible to define outlines to optimise the treatment. We suggest a maturation period in heaps of untreated ash, then sieving and recovery of the iron and finally a second period of post maturation of the sieved ashes (< 30 mm).