Role of transparent exopolymeric particles in membrane fouling: Chlorella vulgaris broth filtration V. Discart a , M.R. Bilad a , D. Vandamme b , I. Foubert b , K. Muylaert b , I.F.J. Vankelecom a,⇑ a Centre for Surface Chemistry and Catalysis, Faculty of Bioscience Engineering, KU Leuven, Kasteelpark Arenberg 23, Box 2461, 3001 Leuven, Belgium b Lab Aquatic Biology, Microbial and Molecular Systems, KU Leuven KULAK, E. Sabbelaan 53, B-8500 Kortrijk, Belgium highlights " The direct role of TEPs on membrane fouling was investigated. " Fresh and fractionated broths were filtered using 2 MF and 1 UF membrane. " Sample and filtration parameter correlations were assessed by Pearson coefficients. " No single dominant sample variable affects fouling. article info Article history: Received 21 August 2012 Received in revised form 5 November 2012 Accepted 6 November 2012 Available online 16 November 2012 Keywords: Algae harvesting Transparent exopolymer particles Dead-end membrane filtration Chlorella vulgaris Micro- and ultrafiltration abstract Recent reports show strong evidence for the involvement of transparent exopolymer particles (TEPs), mainly produced by microalgae in natural environments, in membrane fouling in a wide range of mem- brane filtration processes. The objective of this study is to fundamentally investigate the direct role of TEPs on membrane fouling by using different Chlorella vulgaris broth solutions and different fractions of such broth (the soluble and bound fractions, the cells separated from these fractions and the cells with their bound sugars, separated from the soluble fraction) as filtration feed. The relation between the feed properties and their filterability over three membranes was determined. Scanning electron microscopy and light microscopy showed that the foulant types differed for each broth fraction and confirmed the role of TEPs in the fouling of microfiltration membranes. In addition, this study contributes to the role of TEPs in the filtration of microalgae cultivated for commercial reasons. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Recent reports show strong evidence for the involvement of transparent exopolymer particles (TEPs) in membrane fouling in a wide range of membrane filtration processes (de la Torre et al., 2010; Villacorte et al., 2009a; Kennedy et al., 2009). Because of the transparent nature of these TEPs, their role in membrane foul- ing was in the past often overlooked. In addition, they often es- caped from standard pretreatments applied prior to membrane filtration because of their gel-like compressibility (Kennedy et al., 2009; Villacorte et al., 2009b). TEPs have natural properties of var- iable size (0.4–200 lm), a gel-like structure and a high negative charge. Early indications of the involvement of TEPs in membrane foul- ing, possibly by inducing colloidal fouling or biofilm formation, or a combination of both, led to a significant research interest in this area. The influence of TEPs was studied in a wide variety of set- ups, in reverse osmosis (Villacorte et al., 2009b) and ultrafiltration (Berman et al., 2011), as well as in membrane bioreactors (de la Torre et al., 2010). In all these systems, TEPs seemed to play at least a partial role in the fouling process. In natural environments and in membrane systems, TEPs and TEP precursors can originate from human debris, bacteria or multicellular organisms like macroalgae, oysters or sea snails 0960-8524/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2012.11.034 Abbreviations: TEPs, transparent exopolymer particles; SEM, scanning electron microscopy; Chla, chlorophyll a; SMP CH , carbohydrate fraction of soluble microbial products; SMP PR , protein fraction of soluble microbial products; EPS CH , carbohy- drate fraction of extracellular polymeric substances; EPS PR , protein fraction of extracellular polymeric substances; bTEP, bound transparent exopolymer particles; sTEP, soluble transparent exopolymer particles; Cells EPS , algae cells associated with their bound polymeric substances; PC 0.1 , polycarbonate filter with pore size of 0.1 lm; PC 0.4 , polycarbonate filter with pore size of 0.4 lm; PES 5kDa , polyethersulf- one filter with molecular weight cut-off of 5 kDa; spTEP, soluble particulate transparent exopolymer particles; scTEP, soluble colloidal exopolymer particles; Total CH , total carbohydrates; L, permeance; L CW , clean water permeance; SFV, specific filtration volume; TTF, time to filter. ⇑ Corresponding author. Tel.: +32 16 321594; fax: +32 16 321998. E-mail addresses: valerie.discart@biw.kuleuven.be, ivo.vankelecom@biw. kuleuven.be (I.F.J. Vankelecom). Bioresource Technology 129 (2013) 18–25 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech