Impact of stepwisely reducing settling time on the formation and performance of aerobic granular sludge

The impact of gradually reducing the settling time strategy on the formation, performance, and microbial succession of aerobic granular sludge (AGS) was investigated in a sequencing batch reactor (SBR). The results showed that the short settling time accelerated the granulation of AGS and the granulation was completed within 35 d. When the settling time was 10 min, the granular sludge had good settling performance and significant biological activity, and the average particle size and integrity coefficient increased to 1.017 mm and 93.3 %. The shortening of settling time stimulated bacteria to secrete more extracellular polymeric substances (EPS). Three-dimensional fluorescence spectrum analysis showed that aromatic proteins had high fluorescence intensity. According to the analysis of high-throughput sequencing, Rhodanobacter and Klebsiella were the dominant bacteria, and carbohydrate metabolism and amino acid metabolism were significantly enhanced, which may play an important role in maintaining the stability of AGS.