Combining submerged membrane technology with anaerobic and ...

Chapter 1that proteins are more generally hydrophobic than carbohydrates. Strong interactionbetween the hydrophilic membrane generally used in MBRs and hydrophilic organiccompounds may be the cause of the initial fouling observed in MBR systems. On the otherhand, correlation of MBR membrane fouling with SMP protein has not been widelyreported. Humic matter may not significantly contribute to fouling due to the generallylower MW of these materials (Drews et al., 2005).Recently, the terms biopolymers or biopolymeric clusters (BPC) have also come intouse (Sun et al., 2008; Wang et al., 2008). BPC are defined as a new pool of organicsubstances in the MBR sludge mixture that are a solute independent of the biomass andare much larger than SMP in the sludge suspension. The BPC content in the MBR wasestimated by calculating the difference in TOC concentration between the AS supernatantand the effluent. Therefore is a reliable easy to measure method compared with protein orcarbohydrate determination.Another group which until recently had only been studied in the formation of biofilmsin seawater environments (Pasow, 2002) are the so-called transparent exopolymerparticles (TEP), an acidic fraction of polysaccharides. These compounds consist mainly ofexopolysaccharides of a sticky nature, a characteristic which makes them a group ofinteresting substances in processes like sedimentation, flocculation and membrane fouling.TEP concentration is easy to measure and does not involve the use of sulfuric acid as inthe case of carbohydrate concentration (Dubois et al., 1956). TEP concentration has beenmonitored for the first time in sludge filtrate by de la Torre et al. (2008) highlighting thepotential of this parameter as a fouling indicator for MBR systems.By definition, all these groups of compounds are produced and excreted bymicroorganisms and depending on the applied assays, these groups are not distinct butoverlap (figure 1.8). Unfortunately, the location of the fouling relevant fraction is stillunknown, so are the conditions that shift it to different locations (Drews, 2010).44