r t:~ - ELSEVIER Desalination 118 (1998) 101-108 DESALINATION Characterization of clean and natural organic matter (NOM) fouled NF and UF membranes, and foulants characterization Jaeweon Cho*, Gary Amy, John Pellegrino, Yeomin Yoon Civil and Environmental Engineering, University of Colorado at Boulder, Boulder, CO 80309, USA Tel. +1 (303) 492-7650; Fax +1 (303) 492-7317 Received 16 June 1998 Abstract Contact angles, zeta potentials, and IR spectra of clean and NOM-fouled membranes were compared to demonstrate differences in hydrophobicity, surface charge, and functional groups, respectively. Contact angle increased and decreased for membranes fouled with hydrophobic and hydrophilic NOM, respectively. Zeta potential decreased negatively (less negative) for membranes fouled with both hydrophobic and hydrophilicNOM, suggestingthat ionizable functional groups were coated with non-ionizable NOM components (possibly neutrals). The IR spectra reduced in absorbance intensity for NOM-fouled membranes, suggesting that aromatic groups were coated with non-aromatic or less aromatic NOM components. The results of XAD-8/4 t~actionations of foulants (desorbed NOM with NaOH) showed that hydrophilic and hydrophobic NOM components were the major foulants for membranes fouled with hydrophilic and hydrophobic NOM-source waters, respectively. 1. Introduction Ultrafiltration (UF) and nanoflltration (NF) membranes can be fouled by natural organic matter (NOM), influencing both permeability and NOM rejection. It is desirable to determine which fractions of NOM are responsible for membrane *Corresponding author. fouling. Speth et al. [1] divided NOM fractions of membrane feed-waters and foulants into poly- saccharides, proteins, polyhydroxy-aromatics, and amino sugars using pyrolysis-GC/MS. It was found that thin-film-composite (TFC) NF membranes with conventionally treated feed-water were fouled by organic matter in the order of polyhydroxy aromatics, proteins, polysaccharides, and amino sugars, suggesting the importance of Presented at the Conference on Membranes in Drinking and Industrial Water Production, Amsterdam, September 21-24, 1998, International Water Services Association, European Desalination Society and American Water Works Association 0011-9164/98/$ - See front matter © 1998 Elsevier Science B.V. All rights reserved. PII S0011-9164(98)00100-3