Combining submerged membrane technology with anaerobic and ...

SMP carbohydrates (mg·L -1 )Chapter 3Dissolved oxygen provides an oxygen source for the mineralisation of SMP, andnitrate also seems to influence SMP elimination. Elevated carbohydrate rejection and highcarbohydrate concentrations of up to 150 mg·L -1 were reported by Drews et al. (2008)during a period of low nitrification activity. However, fouling was simultaneously low, whichcould indicate that under these conditions, SMP were too large to cause internal foulingand formed a loose cake instead (Drews et al., 2007). In spite of being tertiary filtrationsystems EPS and SMP concentrations are more similar than those reported by MBRstudies. Other researchers (Tchobanoglous et al., 1998; Coté et al., 2004; Citulsky et al.,2009) have worked in tertiary filtration systems with low biomass concentrations (mg·L -1 ).In this work, biomass concentration at filtration chambers is usually above 2 g·L -1 , beingthis values more appropriated for MBR operation. Therefore, this TMF chambers behavedlike secondary MBRs.200II III IV V150100500115 140 165 190 215 240 265 290 315 340Time (d)Figure 3.11. Carbohydrate SMP concentration in the F-SBR () and G-SBR (•) filtrationchambers.Recent studies have introduced a more general approach to the biopolymersresponsible for membrane fouling by defining biopolymer cluster (BPC) as an importantfactor in the formation of the sludge fouling layer on the membrane surface and theincrease of fouling potential (Wang and Li, 2008; Sun et al., 2008). BPC have been definedas a special form of organic materials formed by the affinity clustering of free EPS or SMPin the sludge cake on the membrane surface (Wang and Li, 2008). Figure 3.12 shows theaverage permeability and standard deviation values versus the colloidal fraction of BPC102