Role of initial bacterial community in the aerobic sludge granulation and performance

The structure of bacterial community was greatly varied from different seed sludge sources, which affected the sludge characteristics. To explore the role of different functional bacteria in AGS granulation and pollutant degradation, three different resources of seed sludge obtained from pharmaceutical wastewater (R1), livestock (R2), and municipal sludge (R3) were employed in this study. Results showed that the initial bacterial community had important significance for AGS formation and pollutants removal. Seed sludge taken from R3 granulated faster than those from R1 and R2. A large number of mature granules were formed after 20 days of operation in R3. In addition, the final mixed liquor suspended solids (MLSS) reached 6853 mg L^-1, with 48 mL g^-1 sludge volume index (SVI) in R3, indicating that it had better settling performance and granulation. In the stable stage of R3, the removal rates of COD, NH₄⁺-N, and TN reached 99.2%, 98.5%, and 97.6%, respectively. The α-diversity analysis showed that the bacterial community of seed sludge greatly determined the microbial composition of AGS. Firmicutes, Gracilibacteria, and Spirochaetes were abundant in R3, which maintained the structures and functions of aerobic granules. This study might provide approaches and insights for AGS culture from different sludge sources.