SPECIATION OF TRACE ELEMENTS IN MUNICIPAL SEWAGE SLUDGE

The sewage sludge investigated in this study originated from the wastewater treatment plant of a municipal wastewater treatment plant located in Finland. Trace element speciation in this context is taken to mean the fractionation of the total element (metal) content into the acid soluble/exchangeable (carbonate bound), reducible (Fe/Mn bound oxides) and oxidizable (bound to organic matter and sulphides) fractions. For this we used the three-step sequential extraction procedure of the BCR (Community Bureau of Reference of the European Commission, now the Standards, Measuring and Testing Programme). The highest extractable concentration in the acid soluble/exchangeable fraction (BCR1 fraction) were observed for Fe (3220 mg kg-1; d.w.), followed by S (908 mg kg-1; d.w.) and Mn (153 mg kg-1; d.w.). The highest extractable concentration in the reducible fraction (Fe/Mn bound oxides; BCR2 fraction) were observed for Fe (37100 mg kg-1; d.w.) followed by Al (657 mg kg-1; d.w.), S (335.0 mg kg-1; d.w.), Ba (218 mg kg-1; d.w.), Cu (164 mg kg-1; d.w.) and Mn (103 mg kg-1; d.w.). The highest extractable concentration in the oxidizable (bound to organic matter and sulphides; BCR 3 fraction) was observed for Fe (17200 mg kg-1; d.w.) followed by S (3220 mg kg-1; d.w.), Al (629 mg kg-1; d.w.) and Cu (138 mg kg-1; d.w.).