Masayuki Kokado

Public Cleansing Bureau Tokyo Metropolitan Government
(8-1, Nishi-Shinjuku, 2-chome, Shinjuku-ku, Tokyo 169-01 Japan)

Abstract

The treatment of flyash from municipal solid waste incinerators (MSWI) has been a serious problem due to its hazardous heavy metals and dioxins.

In Tokyo, more than 3 million tons of combustible wastes are incinerated, and nearly 0.5 million tons of incineration residue and 0.05 million tons of flyash are produced in a year. In 1991, according to the revision of the Waste Disposal and Public Cleansing Law, melting, cementation, chelating and dissolving processes were designated as special disposal methods for flyash. The results of a heavy metal leachate test, used with the products of these four processes, are nearly equivalent to each other and clear the Japanese regulation. However, the melting process is most effective to decrease final volume and toxicity of flyash. In this research, three types of melting methods are still being studied, to confirm exhaust gas cleaning, high efficiency of dioxin reduction and heavy metal capture. Furthermore, the increase of marketability of the products through the melting process, must be established.

Key words: flyash, melting process, dioxin, heavy metal