Impact of Sewage Sludge Spreading on Heavy Metal Speciation in Ecosystem

M.A.El-Taher; E.M.Fawzey; M.E. Soltan; M. N. Rashed
Distribution, mobility and toxicity of heavy metals in the environment depend on the association form in the solid phase to which they are bound. Sequential extraction techniques used to obtain suitable information about heavy metals bounding form and eco- toxicity. In this work, the speciation of heavy metals (Cd, Co, Cu, and Pb), individual metal contamination factor (Cf) and mobility of metals from sewage sludge hills to surrounding ecosystem were conducted. An optimized two sequential extraction (Tessier and BCR) and single extraction procedures for sewage sludge were used. Sewage sludge samples were collected from sludge hills near a wastewater treatment plant at Kema region Aswan. The percentage of each metal as residual, oxidizable, reducible and exchangeable form was calculated. The results revealed that on the basis of heavy metals speciation, the individual contamination factor values of Cd and Co have the highest mobility (Cf: 27.38 and 36.36, respectively) and susceptibility to be released from the sludge, while Pb and Cu have the lowest mobility (Cf 2.25 and1.39, respectively). This study provides valuable information on the mobility of metals in sludge and helps in predicting their behaviour to the ecosystem.
Heavy metals; pollution; sewage sludge; contamination; metal speciation
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