Reducing ultrafiltration membrane fouling during potable water reuse using pre-ozonation

Wastewater reclamation has increasingly become popular to secure potable water supply. Low-pressure membrane processes such as microfiltration (MF) and ultrafiltration (UF) play imperative roles as a barrier of macromolecules for such purpose, but are often limited by membrane fouling. Effluent orga...

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Bibliographic Details
Published in:Water research (Oxford) 2017-11, Vol.125, p.42-51
Main Authors: Wang, Hui, Park, Minkyu, Liang, Heng, Wu, Shimin, Lopez, Israel J., Ji, Weikang, Li, Guibai, Snyder, Shane A.
Format: Article
Language:English
Subjects:
Carbon - chemistry
Drinking Water - chemistry
Effluent organic matter
Hydrophobic and Hydrophilic Interactions
Membrane fouling
Membranes, Artificial
Models, Theoretical
Ozonation
Ozone - chemistry
Polymers - chemistry
Polysaccharides - chemistry
Potable reuse
Proteins - chemistry
Recycling
Sulfones - chemistry
Ultrafiltration
Ultrafiltration - instrumentation
Ultrafiltration - methods
Waste Water
Water Purification - instrumentation
Water Purification - methods
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Summary:Wastewater reclamation has increasingly become popular to secure potable water supply. Low-pressure membrane processes such as microfiltration (MF) and ultrafiltration (UF) play imperative roles as a barrier of macromolecules for such purpose, but are often limited by membrane fouling. Effluent organic matter (EfOM), including biopolymers and particulates, in secondary wastewater effluents have been known to be major foulants in low-pressure membrane processes. Hence, the primary aim of this study was to investigate the effects of pre-ozonation as a pre-treatment for UF on the membrane fouling caused by EfOM in secondary wastewater effluents for hydrophilic regenerated cellulose (RC) and hydrophobic polyethersulfone (PES) UF membranes. It was found that greater fouling reduction was achieved by pre-ozonation for the hydrophilic RC membrane than the hydrophobic PES membrane at increasing ozone doses. In addition, the physicochemical property changes of EfOM, including biopolymer fractions, by pre-ozonation were systemically investigated. The classical pore blocking model and the extended Derjaguin−Landau−Verwey−Overbeek (XDLVO) theories were employed to scrutinize the fouling alleviation mechanism by pre-ozonation. As a result, the overarching mechanisms of fouling reduction were attributed to the following key reasons: (1) Ozone degraded macromolecules such as biopolymers like proteins and polysaccharides into smaller fractions, thereby increasing free energy of cohesion of EfOM and rendering them more hydrophilic and stable; (2) pre-ozonation augmented the interfacial free energy of adhesion between foulants and the RC/PES membranes, leading to the increase of repulsions and/or the decrease of attractions; and (3) pre-ozonation prolonged the transition from pore blocking to cake filtration that was a dominant fouling mechanism, thereby reducing fouling. [Display omitted] •Ozonation reduced membrane fouling for both hydrophilic and hydrophobic membranes.•Ozonation was more efficacious for hydrophilic membrane fouling reduction.•Transition from pore blocking to cake filtration was retarded by ozonation.•Polysaccharide was statistically related to such transition retardation.•XDLVO theory elucidated fouling mechanism by explaining adhesion/cohesion energies.
ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2017.08.030