Research article Fouling control in a lab-scale MBR system: Comparison of several commercially applied coagulants P.K. Gkotsis, E.L. Batsari, E.N. Peleka, A.K. Tolkou, A.I. Zouboulis * Chemical Technology and Industrial Chemistry Section, School of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece article info Article history: Received 11 October 2015 Received in revised form 25 February 2016 Accepted 1 March 2016 Available online xxx Keywords: Membrane bioreactors Fouling control Coagulant e flocculant agents Filterability tests Soluble microbial products abstract The Membrane bioreactors (MBRs) integrate the biological degradation of pollutants with membrane filtration-separation during wastewater treatment. Membrane fouling, which is considered as the main process drawback, stems from the interaction between the membrane material and the (organic or inorganic) foulants, leading to membrane's efficiency deterioration. It is widely recognized that the mixed liquor colloidal and Soluble Microbial Products (SMP) are in principal responsible for this unde- sirable situation. As a result, the appropriate pretreatment of wastewater feed is often considered as necessary procedure and the coagulation/flocculation (C/F) process is regarded as a relevant viable op- tion for wastewater treatment by MBRs in order to improve the effective removal of suspended solids (SS), of colloidal particles, of natural organic matter (NOM), as well as of other soluble materials. The objective of this study is the application of coagulation/flocculation for fouling control of MBR systems by using several commercially available chemical coagulant/flocculant agents. For this purpose, an appro- priate lab-scale continuous-flow, fully automatic MBR system has been assembled and various (inor- ganic) coagulants (i.e. FeCl 3 ∙6H 2 O, Fe 2 (SO 4 ) 3 $5H 2 O, FeClSO 4 , PFS 0.3 , PAC A9-M, PAC-A16, Al 2 (SO 4 ) 3 $18H 2 O, FO4350SSH, NaAlO 2 ) have been examined. Filterability tests and SMP concentration measurements were also conducted in order to investigate the reversible, as well as the irreversible fouling, respectively. Based upon the obtained results and after selecting the most efficient coagulants (FeCl 3 $6H 2 O, Fe 2 (SO 4 ) 3 $5H 2 O, FeClSO 4 , PAC-A9, PAC-A16), an attempt was subsequently performed to correlate the major fouling indices (i.e. TMP, TTF, SMP concentration) in order to improve the overall process operability by this fouling control method. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Membrane bioreactors (MBRs) have been widely used during the past few years for municipal or industrial wastewater treatment (Brindle and Stephenson, 1996; Trussell et al., 2000; Van Dijk and Roncken, 1997), as well as for water reclamation (Cicek et al., 1998). The first reported application of MBR technology, going back to 1969, included an ultrafiltration membrane, which was used to separate the activated sludge in a biological wastewater treatment system (Smith et al., 1969). Appropriate membrane used for the separation of biomass in (or with) a bioreactor is the most common type of MBR and usually combines a suspended growth activated sludge reactor with a membrane (micro- or ultra-) filtration unit in a single process (Stephenson et al., 2000). Membrane bioreactors are increasingly considered to be more effective for wastewater treatment, than the conventional activated sludge treatment systems (Le-Clech et al., 2006), offering several advantages, such as lower space requirements, better effluent quality, higher biomass concentration, hence improved degrada- tion kinetics of pollutants etc. However, membrane fouling still remains the major bottleneck for the widespread application of MBR technology (Chang et al., 2002; Liang et al., 2006; Meng et al., 2009). Several experimental studies indicate that the biocake layer, accumulated on the surface of membrane, is the main cause of membrane fouling in the MBR process (Zhang et al., 2011; Wu et al., 2012; Meng et al., 2007). The biocake layer generally consists of inorganic and organic precipitates, as well as of extracellular polymeric substances (EPS) (Stec and Field, 1995; Chang and Lee, 1998; Nagaoka et al.,1998, 1999; Banti et al., 2013), which can be classified into soluble EPS (sEPS or SMP, Soluble Microbial Products) and bound EPS (bEPS). These are constituting a matrix of high * Corresponding author. E-mail address: zoubouli@chem.auth.gr (A.I. Zouboulis). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman http://dx.doi.org/10.1016/j.jenvman.2016.03.003 0301-4797/© 2016 Elsevier Ltd. All rights reserved. Journal of Environmental Management xxx (2016) 1e9 Please cite this article inpress as: Gkotsis, P.K., et al., Fouling control in a lab-scale MBR system: Comparison of several commercially applied coagulants, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/j.jenvman.2016.03.003