Effects of activated sludge flocs and pellets seeds on aerobic granule properties

Aerobic granules seeded with activated sludge flocs and pellets (obtained from activated sludge flocs) were cultivated in twosequencing batch reactors and their characteristics were compared. Compared with granules seeded with activated sludge flocs,those seeded with pellets had shorter start-up time, larger diameter, better chemical oxygen demand removal e ciency, and higherhydrophobicity, suspended solid concentration, and Mg2+ content. The di erent inocula led the granule surface with di erent microbialmorphologies, but did not result in di erent distribution patterns of extracellular polymeric substances and cells. The anaerobicbacterium Anoxybacillus sp. was detected in the granules seeded with pellets. These results highlighted the advantage of pellet overactivated sludge floc as the seed for aerobic granulation and wastewater treatment.