Abstract:
The purpose of this study was to evaluate the efficiency of heavy metal
(Cu, Zn and Ni) immobilization in sewage sludge amended soils for agriculture by
using hydroxyapatite. Leachability tests were conducted in plastic columns. The
soil types used in the study were silty clay loam and sandy loam. A soil and
sewage sludge mixture ratio of 1:0.2, the addition of hydroxyapatite at 15% and
30% of sewage sludge and pH 7 and pH 4.5 leaching solution used as
representatives of neutral water or neutral precipitation and acid precipitation,
respectively, were applied.
The results of this research indicated that the characteristics of soil had an
influence on the immobilization of copper, zinc and nickel in the sewage sludge
amended soils; the immobilization in silty clay loam was more effective than in
sandy loam. When adding hydroxyapatite at 15% and 30% of sewage sludge into
the sewage sludge amended silty clay loam, it indicated that the efficiencies in
immobilizing copper, zinc and nickel were 43.90 and 48.78%, 57.78 and 62.22%,
and 38.82 and 52.94%, respectively, when using pH 7 leaching solution. When
adding hydroxyapatite at 15% and 30% of sewage sludge into the sewage sludge
amended sandy loam, it indicated that the efficiencies in immobilizing copper,
zinc and nickel were 31.31 and 67.77%, 23.08 and 62.64%, and 59.60 and
84.18%, respectively, when using pH 7 leaching solution. However, when using
pH 4.5 leaching solution (acid precipitation), the results were not significantly
different from those using pH 7 leaching solution (neutral precipitation).