Reviewing bottlenecks in aerobic granular sludge technology: Slow granulation and low granular stability

The long granulation time and instability of aerobic granular sludge (AGS) have restricted its large-scale application significantly. The objective of this review is to discuss the recent achievements and progress made in the field of rapid granulation and granule stability. To this end, we review more than one hundred studies in this field. In this review, four fast granulation methods, namely the addition of metal ions, the addition of a carrier, seeding with AGS, and inoculation using special strains are considered. Three stability enhancement strategies, namely, the improvement of the influent substrate, the selection of slow-growing microorganisms, and the addition of carrier particles, are also discussed. Finally, the potential of these strategies to accelerate granulation and increase the stability of granules in large-scale applications is discussed. In addition, combining a carrier with other strategies to promote granulation and improve stability is proposed. Furthermore, the prospect of enhancing the transmission of signal molecules in quorum sensing systems to promote sludge granulation and improve granule stability are discussed. (C) 2020 Elsevier Ltd. All rights reserved.