Application of waste ashes to agricultural land--effect of incineration temperature on chemical characteristics.

Incineration is one of the most important methods of municipal waste disposal. During incineration, various reactions of composition and decomposition may occur; the physical and chemical properties of municipal wastes may change to a great extent. In the present study, 15 samples, including food scraps (FS), animal wastes (AW) and sewage sludges (SS) were collected from various places in Japan, incineration treatments at 500 degrees C, 850 degrees C and 1000 degrees C were conducted in laboratory, and pH, EC, P content, various P forms, anions and soluble metals were determined. The results indicated that average pH increased by 1.09, 1.84, 2.27 and EC decreased by 4.6, 4.6, 5.6 ds m(-1) at 500 degrees C, 850 degrees C, 1000 degrees C, respectively, pH increased in the sequence of AM > SS > FS, and the decrease rate of EC was in the order of FS > SS > AM. Compared with no treatment (NT), water-soluble P decreased greatly at all three temperatures; available P increased at 500 degrees C, but decreased to the original level at 850 degrees C and 1000 degrees C; the amount of Ca-P, Fe-P and Al-P decreased and residual insoluble P increased greatly at 850 degrees C and 1000 degrees C; no significant change of total P was found at all three temperatures. However, water-soluble HPO4(2-) and Cl- decreased greatly, the decrease ratio of Cl- was in the sequence of SS > FS > AM at 500 degrees C, and FS > SS > AM at 850 degrees C and 1000 degrees C; no significant difference was found for HPO4(2-) among all three treatment temperatures; water-soluble SO4(2-) decreased at 1000 degrees C, but there was no significant change at 500 degrees C and 850 degrees C. Moreover, water-soluble Na, Mg, K, Ti, Mn, Fe, Ga, Cd, Zn, Ba, Pb, Sr, W and 0.1 M HNO3 soluble Al, K, Cr, Mn, Fe, Zn, Sr, Ba, Pb, Be, Ga, Rb, Cd, Sn, Sb, Ta, Tl, Bi, Na, Co, Ni, Sc, Cs decreased, but water-soluble Ca, Cr, Co, Ni and 0.1 M HNO3 soluble Cu, Ca, V, Mo, W, Th, U, Hf increased at 500 degrees C, 850 degrees C or 1000 degrees C.