Journal of Membrane Science 411–412 (2012) 173–181 Contents lists available at SciVerse ScienceDirect Journal of Membrane Science jo u rn al hom epa ge: www.elsevier.com/locate/memsci Submerged membrane hybrid systems as pretreatment in seawater reverse osmosis (SWRO): Optimisation and fouling mechanism determination Sanghyun Jeong a , Yong Jun Choi b , Tien Vinh Nguyen a , Saravanamuthu Vigneswaran a,∗ , Tae Moon Hwang c a University of Technology Sydney (UTS), P.O. Box 123, Broadway, NSW 2007, Australia b University of Science and Technology, 113 Gwahangno, Yuseong-gu, Daejeon, Republic of Korea c Korea Institute of Construction Technology, Gyeonggi-Do 411-712, Republic of Korea a r t i c l e i n f o Article history: Received 25 January 2012 Received in revised form 23 March 2012 Accepted 20 April 2012 Available online 26 April 2012 Keywords: Adsorption Coagulation Membrane fouling Modelling Submerged membrane hybrid system a b s t r a c t Three different submerged membrane hybrid systems (SMHSs) namely submerged membrane coagula- tion hybrid system (SMCHS), submerged membrane adsorption hybrid system (SMAHS), and submerged membrane coagulation–adsorption hybrid system (SMCAHS) were studied as pretreatment systems to seawater reverse osmosis (SWRO). The performances of these SMHSs were compared with that of sub- merged membrane system (without any coagulation or adsorption) in terms of trans-membrane pressure (TMP) development, critical flux, ultrafilter modified fouling index (UF-MFI), dissolved organic carbon (DOC) removal efficiency, and the removal of detailed organic fractions. The experimental results show that pretreatment by SMCAHS led to the best results in terms of organic removal and critical flux. With the low doses of ferric chloride (FeCl 3 ) and powder activated carbon (PAC) of 0.5 mg of Fe 3+ /L and 0.5 g of PAC/L, respectively, this hybrid system could remove 72% of DOC and reduce the UF-MFI nearly five times. The initial DOC and UF-MFI of seawater used in this study were 2.53 mg/L and 14,165 s/L 2 , respectively. The application of three different membrane fouling models namely pore blockage, pore constriction, and cake formation models showed that cake formation was the predominant fouling mechanisms causing fouling in SMHSs. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The reverse osmosis (RO) membrane can produce drinking water from seawater by removing salinity, microbes, etc. How- ever, if RO is used as a single process in desalination, both colloidal and dissolved organic matter that lead to severe fouling will be retained by RO membrane. Since seawater reverse osmosis (SWRO) performance strongly depends on the raw seawater quality, a pre- treatment for raw seawater is generally required [1]. The main purpose of pretreatment is to remove undesirables from the water, Abbreviations: DOC, dissolved organic carbon; LC-OCD, liquid chromatography- organic carbon detector; MF, microfiltration; PAC, powder activated carbon; RMSE, root mean square error; RO, reverse osmosis; SMAHS, submerged membrane adsorption hybrid system; SMCAHS, submerged membrane coagulation–adsorption hybrid system; SMHS, submerged membrane hybrid system; SMCHS, submerged membrane coagulation hybrid system; SWRO, seawater reverse osmosis; TMP, trans membrane pressure; TSS, total suspended solids; UF-MFI, ultrafilter modified foul- ing index. ∗ Corresponding author. Tel.: +61 2 9514 2614; fax: +61 2 9514 2633. E-mail addresses: s.vigneswaran@uts.uts.au, vigid@eng.uts.edu.au (S. Vigneswaran). which otherwise could adversely affect the operation of reverse osmosis. Conventional pretreatment technologies such as coagu- lation, deep bed filtration, dissolved air flotation and low pressure membrane based pretreatment methods such as ultrafiltration and microfiltration can be chosen according to the raw seawater char- acteristics (suspended solids, turbidity, organic matters, etc.) [2]. Low pressure membrane systems such as microfiltration (MF) and ultrafiltration (UF) are considered as the most reliable, cost- effective and sustainable method in water treatment [3]. MF can be used to separate suspended solids, colloids and bacteria and control bacterial nutrition in feed water. The UF, on the other hand can com- pletely remove viruses and some of the macromolecules. A review comparing the past pretreatment practices (both conventional and membrane (MF and UF) based pretreatment methods) indicates that membrane based pretreatment provides consistent feed qual- ity to RO plant [4]. Thus, MF can be used as pretreatment to SWRO [5,6]. When MF membrane is used alone, the suspended solids car- rying organic materials and different types and sizes of particles and undisposed organic matters can deposit and accumulate on the MF surface. These small particles then cause the pore blocking of MF membrane during filtration, resulting in the permeate flux decline with time and the increase trans-membrane pressure (TMP). If the 0376-7388/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.memsci.2012.04.029