Correlations between trans-membrane pressure (TMP) and sludge properties in submerged membrane electro-bioreactor (SMEBR) and conventional membrane bioreactor (MBR) Shadi W. Hasan a , Maria Elektorowicz a,⇑ , Jan A. Oleszkiewicz b a Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, Canada QC H3G 1M8 b Department of Civil Engineering, University of Manitoba, Winnipeg, Canada R3T 5V6 highlights " SMEBR is a novel, compact and complex treatment unit. " SMEBR combines biological, electrokinetics and membrane filtration processes. " Statistical analyses showed differences in sludge properties in SMEBR and MBR. article info Article history: Received 3 January 2012 Received in revised form 14 June 2012 Accepted 15 June 2012 Available online 21 June 2012 Keywords: Submerged membrane electro-bioreactor (SMEBR) Fouling Trans-membrane pressure Mean particle size diameter Statistical analysis abstract The influence of sludge properties in SMEBR and conventional MBR pilot systems on membrane fouling was investigated. Generated data were analyzed using statistical analysis Pearson’s product momentum correlation coefficient (r p ). Analysis showed that TMP had strong direct (r p = 0.9182) and inverse (r p = 0.9205) correlations to mean particle size diameter in MBR and SMEBR, respectively. TMP in SMEBR had a strong direct correlation to the sludge mixed liquor suspended solids concentration (MLSS) (r p = 0.7757) while a weak direct correlation (r p = 0.1940) was observed in MBR. SMEBR showed a mod- erate inverse correlation (r p = 0.6118) between TMP and soluble carbohydrates (EPS c ) and a very weak direct correlation (r p = 0.3448) to soluble proteins (EPS p ). Conversely, EPS p in MBR had more significant impact (r p = 0.4856) on membrane fouling than EPS c (r p = 0.3051). The results provide insight into opti- mization of operational conditions in SMEBR system to overcome membrane fouling. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Membrane bioreactors (MBRs) combine biological treatment with a direct solid/liquid separation by membrane filtration (Bai and Leow, 2002). Membrane fouling is still considered as the major problem hindering the wide applications of MBRs. Membrane foul- ing refers to the deposition of feed water components and other impurities produced in the bioreactor onto the internal and exter- nal features of membrane surface. The accumulation of those materials causes an increase in the overall resistance to the filtra- tion process, thus increasing the energy demand (Chang et al., 2002). Several factors contribute to membrane fouling such as membrane characteristics, operating conditions, and sludge prop- erties (Chang et al., 2002). The influence of the sludge mixed liquor suspended solids (MLSS) on the apparent viscosity, and hence membrane fouling, has been reported by some researchers (Huang et al., 2000). The impact of other parameters such as extracellular polymeric substances (EPS), i.e. soluble EPS and floc particle size (Bai and Leow, 2002) on fouling were also investigated (Chang et al., 2002). Membrane fouling leads to a decline in the permeate flux, an increase in the trans-membrane pressure (TMP), and final- ly, a reduction in the treatment process performance (Nagaoka et al., 1998). In this study, TMP was selected as the key indicator of membrane fouling. Submerged membrane electro-bioreactor (SMEBR) is a recently developed wastewater treatment solo unit that operates based on the interaction between biological processes, membrane filtration, and electrokinetic processes (Bani-Melhem and Elektorowicz, 2010). Previous bench-scale research investigated the processes of biological transformation of organics and ammonia (Bani-Melhem and Elektorowicz, 2011; Elektorowicz et al., 2009), electrocoagula- tion phenomena (Hirzallah et al., 2010), phosphorous removal (Wei et al., 2009, 2011, 2012), changing morphology of flocs (Ibeid 0960-8524/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2012.06.043 ⇑ Corresponding author. Tel.: +1 514 848 2424/7805; fax: +1 514 848 7965. E-mail address: mariae@encs.concordia.ca (M. Elektorowicz). Bioresource Technology 120 (2012) 199–205 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech