Combining submerged membrane technology with anaerobic and ...

Chapter 3phases were varied (table 3.1) to promote the growth of either granular or flocculent sludgein each SBR reactor.Table 3.1. Lengths of the phases during a cycle.PhaseReactorG-SBR(min)F-SBR(min)Feeding Reaction Settling Withdrawal Dead Total3 (aerobic) 147 1 3 26 18060 (anoxic) 90 20 10 0 180The study lasted for 349 days that could be divided into five different experimentalperiods during which the applied OLR or the concentration of particulate COD wasmodified.Period I (from day 0 until day 114). The objective of this period was to develop eithergranular or flocculent sludge with good settling properties prior to coupling the filtrationmembrane modules to the SBRs. Both SBR were operated without tertiary filtrationmembranes in order to achieve a correct development of granular biomass. A SBR cycletime of 3 hours, an exchange volume ratio of 50 % and an OLR of 2 kgCOD·m -3·d -1 werefixed like operation parameters in both systems.Period II (from day 115 until day 231). During this period, both SBRs received asimilar OLR of approximately 2 kgCOD·m -3·d -1 . The objective was to investigate TMF, withsimilar operating conditions in both reactors. Later, during periods III, IV and V, the appliedOLR in the G-SBR was higher than that of the flocculent reactor, and the same averageHRT was maintained in both systems by diluting the wastewater fed to the F-SBR with tapwater.Period III (from day 232 until day 253). The OLR applied to the G-SBR wasmaintained at approximately 3 kgCOD·m -3·d -1 . This value was greater than the rate of 1.5kgCOD·m -3·d -1 applied to the F-SBR.Period IV (from day 254 until day 324). Wastewater free of suspended solids was fedto both systems. The wastewater was prepared by first removing particulate matter in acentrifugation step and then filtering the supernatant with 0.45-μm flat-sheet PVDF90