J Water SRT - Aqua 51 (2002) 109-123

Effects of molecular weight cutoff, f/k ratio (a hydrodynamic condition), and hydrophobic interactions on natural organic matter rejection and fouling in membranes

Jaewon Cho, Heechul Choi, In S.Kim, Jinsik Sohn and Gary Amy

Advanced Environmental Monitoring Research Center (ADEMRC), Kwangju Institute of Science and Technology, Gwangju 500-712, Korea Tel: 82-62-970-2443 E-mail: choj@kjist.ac.kr

Advanced Environmental Monitoring Research Center (ADEMRC), Kwangju Institute of Science and Technology, Gwangju 500-712, Korea Tel: 82-62-970-2443

Division of Water Supply & Drinking Water Management, Ministry of Environment, Kwacheon, Korea Tel: 82-2-507-2454

Department of Civil and Environmental Engineering, University of Colorado, Boulder, Colorado, USA

All the possible mechanisms and factors affecting flux decline, natural organic matter (NOM) rejection, and NOM transport were studied in this paper. Electrostatic exclusion (charge repulsion) was determined to be an influential factor in minimizing flux decline and membrane fouling, and in maximizing NOM rejection; the effective MWCO (membrane molecular weight cutoff) concept was used to support the notion of electrostatic interactions and to describe an apparent MWCO by a charged membrane. This allowed for a negatively-charged tight ultrafiltration (UF) membrane to be comparatively compared to a nanofiltration (NF) membrane in terms of NOM rejection. The f/k ratio, relating relative back-diffusional transport to convective transport, was identified as a major influential factor in terms of flux decline and NOM rejection. The effect of hydrophobicity on flux decline was not significant when the same f/k ratio was used for different NOM-membrane pairs. The convectional and diffusional transportation of NOM was also evaluated for NF and UF membranes using existing thermodynamic models.

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