Affiliations: Center for Environmental Remediation, Institute of
Geographic Sciences and Natural Resources Research, Chinese Academy of
Sciences, Beijing 100101, China
Abstract: 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.
Keywords: composting, distribution, heavy metal, sewage sludge, speciation
