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Ultrafiltration and nanofiltration membrane fouling by natural organic matter: Mechanisms and mitigation by pre-ozonation and pH

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Title: Ultrafiltration and nanofiltration membrane fouling by natural organic matter: Mechanisms and mitigation by pre-ozonation and pH
Authors: Yu, W
Liu, T
Crawshaw, J
Liu, T
Graham, NJD
Item Type: Journal Article
Abstract: The fouling of ultrafiltration (UF) and nanofiltration (NF) membranes during the treatment of surface waters continues to be of concern and the particular role of natural organic matter (NOM) requires further investigation. In this study the effect of pH and surface charge on membrane fouling during the treatment of samples of a representative surface water (Hyde Park recreational lake) were evaluated, together with the impact of pre-ozonation. While biopolymers in the surface water could be removed by the UF membrane, smaller molecular weight (MW) fractions of NOM were poorly removed, confirming the importance of membrane pore size. For NF membranes the removal of smaller MW fractions (800 Da–10 kDa) was less than expected from their pore size; however, nearly all of the hydrophobic, humic-type substances could be removed by the hydrophilic NF membranes for all MW distributions (greater than 90%). The results indicated the importance of the charge and hydrophilic nature of the NOM. Thus, the hydrophilic NF membrane could remove the hydrophobic organic matter, but not the hydrophilic substances. Increasing charge effects (more negative zeta potentials) with increasing solution pH were found to enhance organics removal and reduce fouling (flux decline), most likely through greater membrane surface repulsion. Pre-ozonation of the surface water increased the hydrophilic fraction and anionic charge of NOM and altered their size distributions. This resulted in a decreased fouling (less flux decline) for the UF and smaller pore NF, but a slight increase in fouling for the larger pore NF. The differences in the NF behavior are believed to relate to the relative sizes of ozonated organic fractions and the NF pores; a similar size of ozonated organic fractions and the NF pores causes significant membrane fouling.
Issue Date: 1-Aug-2018
Date of Acceptance: 10-Apr-2018
URI: http://hdl.handle.net/10044/1/58993
DOI: https://dx.doi.org/10.1016/j.watres.2018.04.025
ISSN: 0043-1354
Publisher: Elsevier
Start Page: 353
End Page: 362
Journal / Book Title: Water Research
Volume: 139
Copyright Statement: © 2018 The Authors. Published by Elsevier Ltd. This article is available under a CC-BY Attribution Licence 4.0 ( https://creativecommons.org/licenses/by/4.0/)
Sponsor/Funder: Engineering & Physical Science Research Council (E
Funder's Grant Number: 144356 (EP/N010124/1)
Keywords: Fouling
Humic acid
Nanofiltration
Ozonation
Surface water
Ultrafiltration
MD Multidisciplinary
Environmental Engineering
Publication Status: Published
Online Publication Date: 2018-04-11
Appears in Collections:Faculty of Engineering
Civil and Environmental Engineering
Chemical Engineering



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