Optimal cultivation and characteristics of aerobic granules with typical domestic sewage in an alternating anaerobic/aerobic sequencing batch reactor

The present work investigated some important factors for optimal aerobic granulation using typical domestic sewage as a substrate in a pilot-scale alternating anaerobic/aerobic sequencing batch reactor. High sludge concentration and low sludge loading, for the first time, were used for the reactor start-up. A vast number of small particles appeared on day 8. Subsequently, several measures for controlling sludge concentration and sludge loading within an appropriate range were applied to optimize the granulation process. On day 45, complete sludge granulation was achieved. After 60 days of operation, the aerobic granules always kept in stable state, with an average diameter of 750 mu m and the SVI30 of 20-35 ml/g. The COD, TN, and TP removal ratios were 92%, 81%, and 85%, respectively. The results demonstrated that it was feasible to form aerobic granules quickly using typical domestic sewage under optimal operation strategies, which was further proved by the results from denaturing gradient gel electrophoresis fingerprint. (C) 2012 Published by Elsevier Ltd.