Reactor performance and membrane filtration in aerobic granular sludge membrane bioreactor

Integrated operation between submerged hollow fiber membrane filtration and a sequencing aerobic sludge blanket reactor (SASBR) led to a novel aerobic granular sludge membrane bioreactor (AGMBR). Throughout four months of operation granular sludge dominated in AGMBR and the mean diameter of biomass particle was as big as 0.70 mm. Reactor performance of AGMBR was compared with a traditional submerged membrane bioreactor (SMBR) that was dominated by bioflocs. AGMBR mixed liquor showed much better filtration characteristics. Constant pressure test indicated that when transmembrane pressure (TMP) increased by 8-fold, the membrane permeability loss was 34.5% with AGMBR mixed liquor, or 1.68-fold lower than that of SMBR. Constant flux test showed that when flux increased by 3-fold, the membrane permeability loss was 2.4% with AGMBR mixed liquor, or 21-fold lower than that of SMBR. During continuous reactor operation, membrane TMP increment in AGMBR was negligible whereas membrane module in SMBR required a regular physical maintenance. Dead end cell filtration based on typical mixed liquor samples from AGMBR and SMBR disclosed that the excellent membrane permeability in AGMBR was due to the low compressibility of granular sludge biomass.