Study on the removal of biodegradable NOM from seawater using biofiltration F. Xavier Simon a, ⁎, Elisabet Rudé a , Joan Llorens a , Sylvie Baig b a Department of Chemical Engineering, University of Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Spain b Degrémont SA, 183 avenue du 18 juin 1940, 92508 Rueil-Malmaison cedex, France HIGHLIGHTS ► NOM in seawater is essentially refractory but can cause biofouling problems in seawater facilities. ► Biofouling can be effectively reduced by depleting easy biodegradable matter. ► A biofilter operated at EBCT = 6–11 min can reduce DOC and BOD up to 15%. ► Biofiltration shifts organic matter from higher than 1 kDa to lower than 1 kDa which is less biodegradable. ► A biofilter is able to prevent biological activity and thus reduce the biofilm formation capacity downstream more than 90%. abstract article info Article history: Received 2 October 2012 Received in revised form 21 January 2013 Accepted 22 January 2013 Available online xxxx Keywords: Biofiltration Seawater Natural organic matter (NOM) Biofouling Biofilter Despite the low biodegradability of seawater NOM, problems associated with biofouling are common in facilities that handle seawater. In this work, a fixed-film aerobic biofilter is proposed as an effective unit for preventing biofouling in such facilities. A packed-bed biofilter with an EBCT=6–11 min was employed. The results demonstrated that the DOC is reduced by 6% and the BOD 7 is reduced up to 15%. The LC-OCD analysis revealed that biofiltration abates the LMW neutrals and biopolymer fractions by 33 and 17%, respectively. However, the fractionation with UF membrane showed that the biofiltration process is able to degrade the more biodegradable compounds that have molecular weights that are greater than 1 kDa and compounds with molecular weights of less than 1 kDa. After biofiltration, the biological activity measured in terms of ATP removal was reduced by 60%. Finally, a test to evaluate the biofilm formation capacity of a water sample revealed reductions of ~94% when comparing biofiltered and non-biofiltered seawater. Therefore, a fixed-film aerobic biofiltration process could be a useful treatment for the removal of biodegradable organic matter from seawater and for improving the water quality in terms of less biofilm formation capacity. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Seawater desalination by reverse osmosis (SWRO) has currently emerged as an effective solution to obtain water for human consump- tion and for industrial and agricultural uses [52]. In addition to being used for desalinated water, seawater is also used, e.g., as a coolant in thermal plants [6,46]. In seawater facilities and particularly in SWRO plants, the most common foulants obtained from SWRO membranes are a combination of both organic and microbial deposition [18,68]. Consequently, micro- organisms start growing at the expense of dissolved NOM and can develop a biofilm that can cause operational problems [24,25,28,34,43]. Even with the low and mostly non-biodegradable seawater NOM [48,64], marine microorganisms are metabolically active [21]. In SWRO plants the consequences of fouling include an increase of the membrane resistance coupled with a decrease in water production and water quality. All the above factors have an impact on the total cost of desalinated water [23,43]. Pre-treatments in SWRO processes are designed to improve the water quality for stable and sustainable operation [53]. A considerable number of reports can be found in the literature associated with conventional and membrane pre-treatments [9,10,29,39,42,47,49,50,53,62,63,65,68]. Nev- ertheless, dosages of biocides (often chlorinated substances) are the currently employed common strategy to prevent biofouling because biocides can kill nearly all microorganisms. However, debris are not removed from the aqueous phase and they can therefore serve as a substrate for the living microorganisms, which is why the use of biocides is only considered to be a short-term strategy [25,51]. Moreover, micro- organisms embedded in a biofilm are more resistant to biocides, which is most likely due to selection in favour of more biocide tolerant bacteria; this property confers a large inertia to the system [16,28]. Therefore, Desalination 316 (2013) 8–16 ⁎ Corresponding author. Tel.: +34 934020155; fax: +34 934021291. E-mail address: xsimon@ub.edu (F.X. Simon). 0011-9164/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.desal.2013.01.023 Contents lists available at SciVerse ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal