Characterization of sewage sludge and toxicity evaluation with microalgae

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Pages (from-to)394-401
Journal / PublicationMarine Pollution Bulletin
Volume31
Issue number4-12
Publication statusPublished - Apr 1995

Abstract

Heavy metal contents (Cd, Cr, Cu, Pb, Ni and Zn) of digested sludge, collected from sewage treatment works (Shatin (ST), Shek Wu Hui (SWH), Tai Po (TP) and Yuen Long (YL)) in 1992, 1993 and 1994, were analysed by atomic absorption spectrophotometry after sequential extraction by 1 m KNO3, 0.5 m KF, 0.1 m Na4P2O7, 0.1 m EDTA and 6 m HNO3. It was found that the major forms of Cu, Pb, Ni and Zn were in the sulphide phase, organically-bound phase, adsorbed phase and carbonate phase, respectively. A dinoflagellate (Dunaliella tertiolecta) and a diatom (Thalassiosira sp.) were used as bioindicators to test the toxicity of digested sludge samples collected in 1994. Each of the algae were inoculated to elutriates of digested sludge at different concentrations. The toxicities of the four types of sludge, according to 96 h-IC50s, were ranked as follows: TP > ST > SWH > YL for D. tertiolecta and ST > SWH > TP > YL for Thalassiosira sp. For D. tertiolecta, a significant correlation was found between algal inhibition and ammonium-N, both in sludge (p