A novel mode of air recycling favored stable operation of the aerobic granular sludge process via calcium accumulation

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2019-09, Vol.371, p.600-608
• Main Authors: Zhang, Zhiming, Ji, Yatong, Cao, Runjuan, Yu, Zhuodong, Xu, Xiangyang, Zhu, Liang
• Format: Article
• Language: English
• Subjects: Aerobic granular sludge; Air recycling; Alginate-like exopolysaccharides (ALE); Calcium; Quorum sensing (QS)
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2019.04.083

•The novel operation promoted Ca accumulated in granules.•Ca combined with GG block in ALE to enhance AGS stability.•More EPS-secretion microbes were initially enriched in stable AGS.•Lot of PS, especially ALE with GG block was secreted under the novel operation mode.•ALE with GG block enhanced AGS stability via more functional bacteria enrichment. A novel operation mode of aerobic granular sludge (AGS) with air recycling was investigated to enhance the stability of AGS, and three reactors with varied recycling proportions of 0 (R1), 320% (R2) and 740% (R3) were used in this study. The results showed that more calcium accumulated inside aerobic granules in the R2 and R3 reactors with air recycling and compact granules formed with sludge concentration greater than 6.8 g/L and an integrity coefficient less than 0.1. The high-throughput sequencing results indicated that microbes such as Pseudomonas spp., which secreted extracellular polymeric substance (EPS), were obviously enriched in the reactors with air recycling. Principal component analysis (PCA) indicated that calcium was accumulated by higher proportion of CO2 with air recycling (especially at a recycling proportion of 320%), and bound to poly-guluronic-acid block (GG block) in alginate-like exopolysaccharide (ALE), which had a high binding energy with calcium. The main ALE secretion microbes, Pseudomonas spp., were enriched after the proportion of the GG block in ALE increased and were maintained at a high level. Stable AGS was finally maintained. The results demonstrate the advantage of a novel process including air recycling for aerobic sludge granulation.