| Summary: | 碩士 === 國立臺灣大學 === 環境衛生研究所 === 96 === This study aimed to characterize heavy metal in leachate discharged from a municipal sanitary landfill for ash of incinerators in Taipei. Sanzhuku Sanitary Landfill Site was our study subject. Historical data during 2003-2007 were collected and analyzed on monthly and yearly basis.
The results showed that stabilized/solidified fly ash from Bei-Tou, Nei-Hu and Muzha incinerators predominated in the municipal sanitary landfill. Approximately 15000 tons of solidified fly ash were disposed annually to this landfill with a great portion of ash generated from Bei-Tou incinerator. The heavy metals contained in fly ash included Cr, Pb Cd, Hg, Cu, Zn and As. Zn and Pb accounted for more than 80% of total metals in solidified fly ash, and for 67% in leachate. The estimated cumulative leachated percentages of all metals were generally steady. The estimated cumulative leachated percentage indicated that Hg and As had higher leachability than other metals although only trace amount of Hg and As occurred in the leachate.
The cumulative leachated percentage of metals after bottom ash had been eliminated was lower in comparison with that when bottom ash accounted for 70% and greater of total landfill amount. The concentration of Pb and Cd in leachate significantly increased year by year, but the trend for As was opposite. In addition, the concentration of Cr and As positively correlated to BOD, COD, TOC, NH3- N. Seasonal and annual fluctuation of Cr and Hg concentration in leachate, that was irrelevant to rainfall, were also occured.
The results implicate that heavy metals in solidified ash tend to leach out steadily at low rate in a lon-term sanitary landfill at the stage of methanogenic phase.
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