Changes of Cu, Zn, and Cd speciation in sewage sludge during connposting.
The potential toxicity risks from heavy metals depend on their chemical speciation. The four stages of the Tessier sequential extraction method were employed to investigate changes in heavy metal speciation (Cu, Zn, and Cd) of sewage sludge during forced aeration composting, and then to identify whether the composting process would reduce or enhance their toxicities. Throughout the composting process, the exchangeable, carbonate-bound, Fe-Mn oxide-bound, and organic matter-bound fractions of Cu were converted to the residual Cu fraction. The organic matter-bound Cu fraction greatly contributed to this transformation. Residual Zn fraction was transformed to the Fe-Mn oxide-bound and organic matter-bound fractions after composting. The residual Zn fraction was a major contributor to the organic matter-bound Zn fraction. The availability of Cu and Zn was reduced by composting such that the risk of heavy metal toxicity decreased with prolonged treatment times. Additionally, attention should be paid to the increased availability of Cd in sewage sludge after composting treatment.
Gao
Ding
D
Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Zheng
Guo-di
GD
Chen
Tong-bin
TB
Luo
Wei
W
Gao
Wei
W
Zhang
Yi-an
YA
Li
Yan-xia
YX
D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000378:metabolism* / Q000633:toxicity; D009930:Organic Chemicals / Q000032:analysis; D012722:Sewage / Q000382:microbiology*; D012987:Soil / Q000032:analysis*; D014865:Waste Disposal, Fluid / Q000379:methods*
D019216:Metals, Heavy; D009930:Organic Chemicals; D012722:Sewage; D012987:Soil