Overcoming the instability of aerobic granular sludge under nitrogen deficiency through shortening settling time.

This study investigated the short settling time strategy to overcome the instability of aerobic granular sludge (AGS) under nitrogen deficiency. AGS variations in its physical and chemical characteristics and microbial community were investigated. Results showed that nitrogen deficiency led to the instability of AGS, while short settling time strategy could overcome the instability of AGS under nitrogen deficiency. Extracellular polymeric substances (EPS), especially, the increased secretion of polysaccharide and proteins with amide III groups at the short settling time enhanced the stability of the granules under nitrogen deficiency. Unclassified_f_Microbacteriaceae shifted to be the major bacteria group at short settling time, along with the decrease of Meganema and Rhodobacter and the increase of Lysobacter, which may play an important role in enhancing AGS stability. Therefore, shortening settling time supports an effective strategy for applications of AGS under nitrogen deficiency.