Abstract
The leaching tests, KSLT(Korea Standard Leaching Test), TCLP(Toxicity Characteristics Leaching Procedure), and European NEN 7341(Maximum Available Leaching Test ; MALT) methods were carried out for bottom and fly ashes from nine MSW(municipal solid waste) incinerators, which consisted of different types of furnaces and air pollution control devices in Korea, to investigate the relationships between heavy metal contents and leachate concentrations for each ash. In the course of leaching studies, numerous characteristic data in physical and chemical properties of ashes from MSW incinerators were obtained and some metals leaching exceeded the regulatory limit by KSLT even. Heavy metal contents in bottom ashes were higher in following order; Cu > Pb > Cr > Cd > As > Hg, and those in fly ashes were in following order; Pb > Cu > Cd > Cr > Hg > As. These results showed that the boiling and melting points of each heavy metals affected to the heavy metal contents in ashes. For some metals in fly ashes, it could be found the proportional relationships between heavy metal contents and leachate concentrations, but for most of heavy metals in bottom ashes could not showed any correlations between them. In the case of fly ashes, heavy metals were easily leached out because the vaporized metals were condensed and coagulated on the ashes under unstable conditions. However, the heavy metals in the bottom ashes, which were remained in the combustion environment i.e., well balanced state, could be more difficult to leach out than once vaporized metals in fly ashes. From the results, the most influence leaching factors of heavy metals from ashes were pH of leaching solution and pH of ashes. Additionally, KSLT method may estimate the concentrations relatively lower than the other leaching tests in heavy metals because leaching solution of KSLT were affected by sample pH.