Molecular size distribution of natural organic matter in raw and drinking waters

The purpose of this study was to compare the molecular size distribution (M SD) of natural organic matter (NOM) in raw waters (RW) and drinking waters (DW), and to find out the differences between MSD after different water tre atment processes. The MSD of NOM of 34 RW and DW of Finnish waterworks were determined with high-performance size-exclusion chromatography (HPSEC). Si x distinct fractions were generally separated from water samples with the T SK G3000SW column, using sodium acetate at pH 7 as an eluent. Large and int ermediate humic fractions were the most dominant fractions in surface water s (lakes and rivers), while in artificially recharged groundwaters and natu ral groundwaters intermediate and small fractions predominated. Water treat ment processes removed the two largest fractions almost completely shifting the MSD towards smaller molecular size in DW. Granular activated carbon (G AC) filtration, ozonation, and their combination reduced all humic fraction s compared to the conventional treatment. Humic fractions correlated with t otal organic carbon (TOC) content and chemical oxygen demand, this being es pecially true in RW. The results demonstrate that the HPSEC method can be a pplied for a qualitative and also for rough estimate quantitative analyzes of NOM directly from RW and DW samples without sample pretreatment. (C) 200 1 Elsevier Science Ltd. All rights reserved.