Enhanced heavy metals removal without phosphorus loss from anaerobically digested sewage sludge

Ito, A.; Takahashi, K.; Aizawa, J.; Umita, T.

Water Science and Technology a Journal of the International Association on Water Pollution Research 58(1): 201-206

2008


ISSN/ISBN: 0273-1223
PMID: 18653955
DOI: 10.2166/wst.2008.642
Accession: 031250153

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Abstract
Heavy metals removal without phosphorus loss from anaerobically digested sewage sludge was investigated by conducting batch experiments using hydrogen peroxide and/or iron sulfate under acidified conditions at pH 3. The addition of hydrogen peroxide to the sludge improved the elution efficiencies of As, Cd, Cu and Zn with phosphorus loss from the sludge. The optimum initial concentrations of hydrogen peroxide were. Respectively. 0.1% for As, Cd, Mn and Zn and 0.5% for Cu and Ni. The combined process of 0.1% hydrogen peroxide and 1 g Fe/L ferric sulfate enhanced the initial elution rate of Cu and Cr compared to the addition of either ferric sulfate or hydrogen peroxide, indicating that oxidants stronger than hydrogen peroxide were produced in the sludge. Furthermore, the combined process immobilized phosphorus in the sludge due to co-precipitation with ferric hydroxide or precipitation as ferric phosphate. It was concluded that there is a possibility that the combined process could remove heavy metals effectively without phosphorus loss from anaerobically digested sewage sludge.