Time behaviour of metals in the leachate of a pretreated solid waste landfill

Two pilot landfills were activated at the Dept. of Hydraulics, Transportation and Roads of Rome (Italy): one was filled by organic fraction of solid urban waste and incineration residues and the other only by organic fraction of solid urban waste. They were periodically monitored and their leachate sampled for metal concentration analyses. Cr, Fe, Mn, Cu, Ni, Zn concentrations were measured by PIXE technique (at the National Lab. of Legnaro, Padua, Italy) in the leachate samples collected from the pilot landfills during their activity. The experimentation was carried on up to the landfills stabilization, up to 200 and 600 days respectively The metal concentration profiles versus time were compared with the pH and COD behaviour, monitored in the leachate over the same time interval. The acid phase and the methane fermentation were identified in the pilot landfill evolution. The metal concentrations follow substantially the trend expected for a generalized real landfill evolution, over more longer time. The presence of basic incineration waste affects the pH and the metal concentration behaviour in the leachate, even if the acide phase duration is reduced.