A systemic evaluation of aerobic granular sludge among granulation, operation, storage, and reactivation processes in an SBR

As a biological promising wastewater treatment technology, aerobic granular sludge (AGS) technology had been widely studied in sequencing batch reactors (SBRs) for the decades. Presently, the whole processes of its granulation, long-term operation, storage, and reactivation have not been thoroughly evaluated, and also the relationships among microbial diversity, granular size, and characteristics were still not that clear. Hence, they were systematically evaluated in an AGS-SBR in this work. The results demonstrated that Proteobacteria and Bacteroidetes were the dominant phyla, Flavobacterium, Acinetobacter, Azoarcus, and Chryseobacterium were the core genera with discrepant abundances in diverse stages or granular size. Microbial immigration was significant in various stages due to microbial diversity had a line relationship with COD/MLVSS ratio (R2 = 0.367). However, microbial diversity had no line relationship with granular size (R2 = 0.001), indicating the microbial diversity in different-sized AGS was similar, although granular size had a line relationship with settleability (R2 = 0.978). Overall, compared to sludge traits (e.g., sludge size, settleability), COD/MLVSS played a key role on microbial evolution. This study revealed the relationships between granule characteristics and microbial community, and contributed to the future AGS-related studies.

Automated summary

This study systematically evaluated the granulation, long-term operation, storage, and reactivation processes of aerobic granular sludge (AGS) technology in sequencing batch reactors (SBRs). The relationships between microbial diversity, granular size, and characteristics were also investigated. The results showed that Proteobacteria and Bacteroidetes were the dominant phyla, and certain genera such as Flavobacterium, Acinetobacter, Azoarcus, and Chryseobacterium had varying abundances in different stages or granular sizes. Microbial immigration was found to be significant in various stages, and microbial diversity had a linear relationship with COD/MLVSS ratio. However, there was no linear relationship between microbial diversity and granular size, indicating similar microbial diversity in different-sized AGS. Overall, COD/MLVSS played a key role in microbial evolution compared to sludge traits. This study contributes to future research on AGS.