Hidehiro Kaneko

Department of Civil and Environmental Engineering, Yamanashi University
(4-3-11, Takeda, Kofu, Yamanashi 400-8511 Japan)

Abstract

The effect of leaching conditions (S/L and pH) on the toxicity of municipal waste incinerator fly ash leachate was evaluated with an algal toxicity test. The leachate prepared with pH = 7 and S/L = 10w/v% was 5 times more toxic than that prepared with same pH and S/L = 1w/v%. But the latter released twice as much toxicity per fly ash than the former. The major toxic constituents in both of the leachates, however, were the same, i.e., zinc. 61% and 44% of the toxicity were estimated to be due to zinc for the leachate prepared with S/L = 10w/v% and 1w/v%, respectively. The toxicity of leaches prepared with the same S/L ratio (1w/v%) and varied pH levels 4, 7 and 12 was also compared. Among these three leachates, the leachate of pH = 4 was most toxic. Its major toxic constituent was also zinc, causing 44% of its toxicity. Lead, on the other hand, was expected as the major toxic constituent of the leachate prepared with pH = 12. This implied that zinc and lead must be specifically targeted in MWI fly ash treatment and disposal.

Key words: algal assay, leachate toxicity, MWI fly ash, heavy metal, leaching condition