A comparative study on leaching characteristics of heavy metals from municipal solid waste incineration bottom ashes in Korea and Japan

摘要

In Korea there are serious problems as it is impossible to landfill municipal solid waste incineration bottom ash (MSWIBA) because the leaching concentration of lead (Pb) from MSWIBA frequently does not meet the regulatory limit. This study was conducted not only in order to find out the factors which make the leaching concentration of Pb high and propose measures to make the landfilling of MSWIBA possible in Korea but also in order to investigate whether the same phenomena associated with Pb high concentration leaching have been taking place in Japan. Samples were taken from MSWIBA piled at an outside stock yard of Korean MSWI plant. Korean samples and an additional sample taken from a Japanese plant were analyzed to measure elemental contents and leaching concentrations of metals by Japanese Leaching Test No.13 (JLT- 13) and pH dependent leaching test (pH-stat). Results on the leachability of heavy metals from MSWIBA samples were compared with statistical data based on previous reports. The comparative study suggested that the high leaching concentration of Pb was due to hydroxides generated by dissolution of oxidized alkali and alkali earth metals such as calcium (Ca), sodium (Na) and potassium (K) which are contained at high concentrations in MSWIBA. It is therefore necessary that the aging techniques, including carbonation against heavy metals and neutralization by carbon dioxide in air, be applied prior to landfill to meet the Korean regulatory limit. As phenomenon like this high-concentration leaching of Pb in Korea have taken place in Japan, it is necessary to take appropriate landfill disposal and direct utilization of MSWIBA into consideration from aspects of Pb leaching as soon as possible.