Yukio Noma* and Akiko Kida*

* Hiroshima Prefectural Health and Environment Center

+ Correspondence should be addressed to Yukio Noma:
(1-6-29 Minami-machi, Minami-ku, Hiroshima 734-0007 Japan)

Abstract

Available amounts of calcium and major components in bottom ashes and fly ashes from municipal incinerators were examined to determine their influence on calcium scale formation in landfill sites. All of Ca (OH) 2 and CaSO4 contained in ash samples could not leach by the batch leaching test with low liquid/solid ratios (eg.10) because of their solubility restrictions. A liquid/solid ratio of 200 is recommended to obtain total soluble calcium. Free alkali could be determined by acid titration curve. Fly ashes with Ca (OH) 2 spray largely influence on calcium scale formation because of soluble calcium and free alkali. In addition, completely burned ashes are liable to leach two components. Calcium scale has been found at 5 out of 15 landfill sites. Three cases might be caused by highly alkaline fly ashes, and the other two by bottom ashes.

Key words: calcium scale, bottom ash, fly ash, leaching test, liquid/solid ratio