The formation and characteristics of aerobic granules in sequencing batch reactor (SBR) by seeding anaerobic granules

The cultivation of aerobic granules in SBR by seeding anaerobic granular sludge was investigated using acetate-based synthetic wastewater. Morphological variation of granular sludge in the reactor was observed and results revealed that the inoculated anaerobic granules experienced a process of disintegration-recombination-growing up. The disintegrated anaerobic sludge may play a role of nucleus for the granulation of aerobic sludge. The sludge concentration increased for the first 4 weeks, then decreased and reached a stable value of 5 g/l at 60 d with a SVI of 30-40 ml/g. Granular sludge dominated in the reactor and suspended sludge concentration was less than 0.5 g/l at the end of the process. In the inoculated anaerobic granular sludge, spherical bacteria were the main microorganisms, however, rod-shaped and filamentous microorganisms prevailed in the cultivated aerobic granules. This is ready way to cultivate aerobic granules by seeding anaerobic granular sludge.