Review
Fouling and cleaning of ultrafiltration membranes: A review

https://doi.org/10.1016/j.jwpe.2014.04.003Get rights and content

Abstract

Ultrafiltration (UF) is one of the best options for both one-stage and as part of multi-stage water and wastewater purification. This review summarises the known facts about the fouling processes and cleaning procedures and details of the most successful physical and chemical cleaning combinations. The optimum cleaning is closely linked to the nature of the fouling. Precise knowledge of both the fouling type (organic, inorganic, or biological) and the fouling mechanism (gel formation, adsorption, deposition, pore blockage, or cake formation) is the key to success in UF membrane cleaning.

Introduction

Modern ultrafiltration was originally developed as a fractionation technique in the late 1960s [1]. Since then, this technology has enjoyed continuous development, and its applications have spanned a wide variety of fields, from chemical recovery, water treatment, wastewater reclamation, juice concentration, dairy making, medical usage, to the harvesting of cells [1]. However, membrane fouling is still a severe problem limiting the potential of this technique. Fouling may result in an increase in operational costs, due to an increased energy demand, additional labour for maintenance, cleaning chemical costs, and shorter membrane life. It requires effective and efficient methods for its control and minimisation.

It may be possible to prevent fouling before its occurrence by methods such as pre-treatment of the feed streams, chemical modification to improve the anti-fouling properties of a membrane, and optimisation of the operational conditions. However, periodic membrane cleaning is still currently inevitable. It is indeed an integral part of most membrane processes in modern industries, and must be regularly carried out to remove the fouled materials and restore the productivity of the operation [2].

Study of membrane cleaning has always been a complement to developing deeper knowledge of fouling. However, the dedicated literature on membrane cleaning is notably less than that on fouling studies [3]. Many previous cleaning studies were actually subsidiary to that of relative fouling, and for which the study was far from comprehensive. However, owing to the greatly improved understanding of fouling in the last two decades, there have been an increasing number of dedicated studies on membrane cleaning. In particular, systematic studies have been made in many respects in recent years.

A quick scan of bibliographic databases shows that the number of research papers with respect to membrane cleaning has boomed in the last decade. This corresponds to the large, simultaneous expansion of UF processes in industries such as water, wastewater, food and biotechnology. The up-to-date information on membrane cleaning is constantly in demand because it is a vital part for the operation of most membrane systems.

There exist a few excellent summary works and pioneering early reviews regarding membrane cleaning. Many of them are parts of more general reviews of fouling and its control technology [4], [5], [6]. Full reviews on membrane cleaning were written about two decades ago [7], including one on reverse osmosis [8]. There are also works dedicated to specific areas in this realm such as conventional cleaning [9], ultrasonic cleaning [10], membrane cleaning in the food industry [2] and chemical cleaning in the water industry [3], [11]. However, the increasing number of UF applications and the rapid development in UF cleaning constantly brings out new ideas and results. An updated review is therefore timely and useful.

In our opinion, the comprehension of membrane cleaning involves gaining knowledge of many separate aspects and making the links between them. It should include the target (common fouling problems in these industries), removal (various cleaning methods), results (cleaning effectiveness and any side effects such as membrane damage) and optimisation (effect of operational parameters). Thence, the scope of this paper is to produce a review in a comprehensive manner about current cleaning processes and techniques for UF fouling in various industries. We have restricted the coverage to major UF applications in solid–liquid separation. We have also included some innovative cleaning techniques which are not yet in common practice.

A brief introduction is given on the understanding of UF fouling to know better what the problem is. A discussion of membrane cleaning, including physical, chemical, conventional and non-conventional methods, is followed by the cleaning processes, factors and optimisation. Finally, the side effects of cleaning are discussed.

Section snippets

Membrane fouling

Optimisation of membrane cleaning protocols requires in-depth understanding of the complex interactions between the foulant and the membrane. Most cleaning studies reported are based on trial-and-error methods [7], [12]. A more systematic approach is required to study the various aspects of fouling control [13]. In addition, it is important to consider the economic impact of cleaning procedures, including the costs of the cleaning process itself along with the effect of the procedures on

Definition and principle

Cleaning can be defined as “a process whereby material is relieved of a substance that is not an integral part of the material [7]”. A membrane cleaning should result in a membrane that is physically, chemically and biologically clean, and thus can provide adequate flux and separation [73]. It should do so, while also meeting the following criteria: (1) restoration of the initial flow through a pristine membrane without adversely changing its surface; (2) keeping dislodged foulants in

Membrane properties

Membranes possess mechanical strength, thermal stability and chemical resistance, which depend on the material of construction. But it is not necessarily the case that a membrane that is stable against one of the factor can perform well against all of them. The mechanical, thermal and chemical factors regarding these materials are listed in Table 4.

CA membranes are naturally hydrophilic with low binding to proteins, but have a limited range of operational pH. A lower pH can degrade the

Conclusions

The current paper presents a comprehensive review of membrane fouling and cleaning in UF applications. Firstly, membrane fouling, the reason for cleaning in the first place, is addressed in terms of its cause, forms and the major types of foulants and effective parameters. Secondly, the goals, methods, mechanisms and processes of membrane cleaning are discussed in great detail:

  • Membrane cleaning is a vital step in maintaining the permeability and selectivity of the membrane. It is also necessary

Acknowledgements

Galit Tal and Xiafu Shi would like to thank their advisors Vitaly Gitis and Nicholas Hankins for their professional support and guidance. All authors express their thanks for financial support from the UK-Israeli Science Network Development Scheme, facilitating the collaboration which led to this review article.

References (203)

  • K. Kimura et al.

    Irreversible membrane fouling during ultrafiltration of surface water

    Water Res.

    (2004)
  • S.-C. Tu et al.

    A pore diffusion transport model for forecasting the performance of membrane processes

    J. Membr. Sci.

    (2005)
  • K.L. Jones et al.

    Protein and humic acid adsorption onto hydrophilic membrane surfaces: Effects of pH and ionic strength

    J. Membr. Sci.

    (2000)
  • A.E. Childress et al.

    Effect of solution chemistry on the surface charge of polymeric reverse osmosis and nanofiltration membranes

    J. Membr. Sci.

    (1996)
  • A.E. Childress et al.

    Effect of humic substances and anionic surfactants on the surface charge and performance of reverse osmosis membranes

    Desalination

    (1998)
  • R.W. Field et al.

    Modelling of permeability loss in membrane filtration: re-examination of fundamental fouling equations and their link to critical flux

    Desalination

    (2011)
  • C. Güell et al.

    Microfiltration of protein mixtures and the effects of yeast on membrane fouling

    J. Membr. Sci.

    (1999)
  • D. Hughes et al.

    Crossflow filtration of washed and unwashed yeast suspensions at constant shear under nominally sub-critical conditions

    J. Membr. Sci.

    (2006)
  • D. Jermann et al.

    Influence of interactions between NOM and particles on UF fouling mechanisms

    Water Res.

    (2008)
  • Q. Li et al.

    Synergistic effects in combined fouling of a loose nanofiltration membrane by colloidal materials and natural organic matter

    J. Membr. Sci.

    (2006)
  • G. Amy

    Fundamental understanding of organic matter fouling of membranes

    Desalination

    (2008)
  • W.-Y. Ahn et al.

    Effects of background cations on the fouling of polyethersulfone membranes by natural organic matter: experimental and molecular modelling study

    J. Membr. Sci.

    (2008)
  • G. Belfort et al.

    The behaviour of suspensions and macromolecular solutions in crossflow microfiltration

    J. Membr. Sci.

    (1994)
  • R.W. Field et al.

    Critical, sustainable and threshold fluxes for membrane filtration with water industry applications

    Adv. Colloid Interface Sci.

    (2011)
  • Z. Cui

    Protein separation using ultrafiltration – an example of multi-scale complex systems

    China Particol.

    (2005)
  • C. Jucker et al.

    Adsorption of aquatic humic substances on hydrophobic ultrafiltration membranes

    J. Membr. Sci.

    (1994)
  • M. Kulovaara et al.

    Effects of aquatic humic substances on a hydrophobic ultrafiltration membrane

    Chemosphere

    (1999)
  • W. Yuan et al.

    Humic acid fouling during microfiltration

    J. Membr. Sci.

    (1999)
  • I. Sutzkover-Gutman et al.

    Humic substances fouling in ultrafiltration processes

    Desalination

    (2010)
  • E. Aoustin et al.

    Ultrafiltration of natural organic matter

    Sep. Purif. Technol.

    (2001)
  • A. Zularisam et al.

    Behaviours of natural organic matter in membrane filtration for surface water treatment – a review

    Desalination

    (2006)
  • L. Fan et al.

    Influence of the characteristics of natural organic matter on the fouling of microfiltration membranes

    Water Res.

    (2001)
  • A.I. Schäfer et al.

    Nanofiltration of natural organic matter: removal, fouling and the influence of multivalent ions

    Desalination

    (1998)
  • J. Hanemaaijer et al.

    Fouling of ultrafiltration membranes: the role of protein adsorption and salt precipitation

    J. Membr. Sci.

    (1989)
  • D. Jermann et al.

    Interplay of different NOM fouling mechanisms during ultrafiltration for drinking water production

    Water Res.

    (2007)
  • E. Tombácz et al.

    The role of reactive surface sites and complexation by humic acids in the interaction of clay mineral and iron oxide particles

    Org. Geochem.

    (2004)
  • E. Tombácz et al.

    Surface charge heterogeneity of kaolinite in aqueous suspension in comparison with montmorillonite

    Appl. Clay Sci.

    (2006)
  • K.L. Chen et al.

    Influence of humic acid on the aggregation kinetics of fullerene (C60) nanoparticles in monovalent and divalent electrolyte solutions

    J. Colloid Interface Sci.

    (2007)
  • A.E. Contreras et al.

    Combined fouling of nanofiltration membranes: mechanisms and effect of organic matter

    J. Membr. Sci.

    (2009)
  • R.S. Faibish et al.

    Effect of interparticle electrostatic double layer interactions on permeate flux decline in crossflow membrane filtration of colloidal suspensions: an experimental investigation

    J. Colloid Interface Sci.

    (1998)
  • A.I. Schäfer et al.

    Microfiltration of colloids and natural organic matter

    J. Membr. Sci.

    (2000)
  • K. Katsoufidou et al.

    An experimental study of UF membrane fouling by humic acid and sodium alginate solutions: the effect of backwashing on flux recovery

    Desalination

    (2008)
  • E. Arkhangelsky et al.

    Impact of chemical cleaning on properties and functioning of polyethersulfone membranes

    J. Membr. Sci.

    (2007)
  • P. Blanpain-Avet et al.

    Chemical cleaning of a tubular ceramic microfiltration membrane fouled with a whey protein concentrate suspension – characterization of hydraulic and chemical cleanliness

    J. Membr. Sci.

    (2009)
  • C. Shorrock et al.

    Membrane cleaning: chemically enhanced removal of deposits formed during yeast cell harvesting

    Food Bioproducts Process.

    (1998)
  • S. Hong et al.

    Fouling control in activated sludge submerged hollow fiber membrane bioreactors

    Desalination

    (2002)
  • S. Hong et al.

    Kinetics of permeate flux decline in crossflow membrane filtration of colloidal suspensions

    J. Colloid Interface Sci.

    (1997)
  • H. Chua et al.

    Controlling fouling in membrane bioreactors operated with a variable throughput

    Desalination

    (2002)
  • H. Liang et al.

    Cleaning of fouled ultrafiltration (UF) membrane by algae during reservoir water treatment

    Desalination

    (2008)
  • S. Li et al.

    Impact of backwash water composition on ultrafiltration fouling control

    J. Membr. Sci.

    (2009)
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