Combining submerged membrane technology with anaerobic and ...

Permeability (L·m -2·h -1·bar -1 )cBPC concentration (mg·L -1 )Chapter 6400I II III IV V VI80300602004010020000 50 100 150 200 250Time (d)Figure 6.6. Evolution of permeability (•) and colloidal BPC concentration () in theMBR.It is widely accepted that stress conditions induces the production and release ofpolymeric substances. Therefore, the change in the conditions at the beginning of periodsII and IV would explain the increase on cBPC concentration. The desorption of dissolvedmethane on period VI might impact indirectly on cBPC concentration through the loss ofdenitrification activity (section 6.4.2). In fact, althoug membrane fouling in denitrificationMBRs has not been extensively characterized, the results obtained in period VI were inaccordance with those reported by Paetkau and Cicek (2011), who studied nitrogenremoval in an MBR and reported that the highest TEP concentrations took place during anunstable denitrification period.Despite the flux limitations, the application of membrane technology was of coreimportance in the studied system. Membrane cut-off could be the solution to problemsrelated with the wash-out of extremely slow-growing bacteria, such as denitrifyingmethanotrophs (Kampman et al., 2012), and avoid the loss of methanogenic bacteria thatreaches the MBR from the UASB reactor.6.5. Conclusions Denitrification using methane as a carbon source was proved to be feasible in asystem with a UASB pre-treatment followed by an aerobic MBR with a previous anoxic168