Enhanced Fouling Resistance and Antibacterial Properties of Novel Graphene Oxide-Arabic Gum Polyethersulfone Membranes  
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2 Qatar Environment and Energy Research Institute (QEERI) Hamad Bin Khalifa University (HBKU), P.O. Box 34110 Doha, Qatar 2 Qatar Environment and Energy Research Institute (QEERI) Hamad Bin Khalifa University (HBKU), P.O. often described as the \"Achilles heel\" of membrane technology, is by far and large the main problem, which arises in real applications that rely on membrane processes [4]. Fouling is caused by the settling of inorganic (usually metal salts), particulate or colloidal matter (silt and clay particles) and organic substances (such as proteins, lipids and polysaccharides) on membrane surfaces and membrane pores [5]. A fourth type of fouling, referred to as biofouling, is caused by microorganisms and the extracellular polymer substances (EPS) that they secrete [6]. Biofouling is ascribed to any form of membrane fouling that has originated from microorganisms and their associated secretions [7]. Membrane biofouling is an inherent problem that is encountered in a wide range of membrane-based water treatment processes, having a profound impact on determining the efficiency and applicability of the membrane. The process of biofouling is complex in nature, however it can be described in four basic stages. Initially, a conditioning film is formed on the membrane surface as a result of the adsorption of large organic molecules such as humic substances, lipoglycans and other products of microbial processing. This is shortly followed by the primary adhesion by rapidly adhering cells which exist as part of the microbial community in the feed water or solution. The third stage sees further colonization and growth by a wider spectrum of bacterial species. These late colonizers adhere to the membrane by exuding extracellular slime or EPS, which ultimately leads to the formation of a robust biofilm layer. The final stage in the biofouling process is the irreversible blocking of the membrane [8]. Unfortunately, the biofilm that is formed by the microorganisms acts as a protective shield from the conventional strategies that are used to combat biofouling such as chlorination or the addition of formaldehyde; this stabilizes the biofilm [9]. Other sanitizing agents including hydrochloric acid, caustic compounds and peroxides, amongst others, have been trialed with little or no success [10]. Membrane biofouling has a number of detrimental effects on membrane systems. Once the biofilm has been established on the membrane surface, the membrane flux declines [11]. This leads to increased feed pressure in order to maintain water filtration rates [12]. The increased pressure boosts operation costs and leads to a larger carbon footprint due to the additional electrical consumption [13]. The quality of the permeate may be compromised due to the increased passage of salts which is inevitable due to the buildup of aqueous ions that are embedded in the biofilm [14]. The high concentration at the membrane surface creates a strong concentration gradient. The prevention and control of biofouling has taken many forms and strategies, none of which have succeeded in tackling the problem with rigor [15]. Biocide treatment has notoriously failed to address the problems that are associated with biofouling due to a number of reasons. Apart from the emergence of resistant strains of bacteria either by variation or via genetic interchange between species, the use of most biocides, such as chlorine, has proven incompatible with most membrane types [4]. Furthermore, any use of biocidal agents requires high-pressure flushing and cleaning, both of which are costly processes [9].