J Water SRT - Aqua 54 (2005) 157-163
Characterization of dissolved organic matter (DOM) removed by iron coagulation using spectrofluorimetry and pyrolysis GC/MS analysis
Kazuhiro Komatsu, Fumiyuki Nakajima, Hiroaki Furumai and Osamu Miki
National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki, 305-8506, Japan, E-mail: kkomatsu@nies.go.jp
Urban and Environment Systems, Department of Information Systems, Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo, 153-8904, Japan
Department of Urban Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-8656, Japan
Nippon Steel Corporation, 20-1 Shintomi, Kimitsu, Chiba, 293-8511, Japan
ABSTRACT
In this study, coagulation experiments were conducted using three coagulants (ferric chloride (FC), poly ferric sulfate (PFS) and poly aluminum chloride (PAC)) to evaluate DOM (dissolved organic matter) removal performance in lake water. DOM removal was characterized not only by comprehensive indices such as dissolved organic carbon (DOC) and UV absorbance at 260 nm (UVA260) but also by spectrofluorimetry and pyrolysis gas chromatography/mass spectrometry (py-GC/MS) analysis, which are useful techniques to obtain information on the structure of organic matter. At a coagulant concentration of 0.3 mM, a higher percentage of DOC was removed by ferric coagulants than by the aluminum coagulant (FC: 53%, PFS: 41%, PAC: 36%). Similar trends were observed in the coagulation-induced decrease of UVA260 and trihalomethane formation potential (THMFP). Spectrofluorimetry showed that higher concentrations of coagulant increased the removal of DOM with fluorescence components. However, fluorescence intensity was not reduced by increased coagulant concentrations at emission wavelengths shorter than 350 nm. Treatments with ferric coagulants were more effective in removing fluorescent components than PAC. Comparison of pyrochromatograms before and after coagulation revealed that the peak area of propanoic acid decreased most significantly after coagulation by FC among 16 identified fragment compounds. Four fragment compounds differed greatly in their coagulation behaviour, depending on the coagulant used.
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