In this study, the formation characteristics of aerobic granular sludge in a continuous-flow reactor were investigated under several experimental conditions. Both surface loading rate (equal to liquid linear velocity at a sludge settling zone) and aeration rate strongly affected the selection of well-settling sludge in the same manner as sludge settling time in a sequencing batch reactor. By setting and controlling adequate surface loading and aeration rates, small particles were effectively washed out, and well-settling sludge selectively remained in the reactor. As a result, aerobic granular sludge was effectively formed. On the other hand, feeding pattern, i.e., continuous and intermittent feeding, did not affect the aerobic granulation when completely inorganic wastewater was fed. These findings will contribute to the dissemination of aerobic granular sludge technology because the information on the formation of aerobic granular sludge in a continuous-flow reactor is limited.

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