Evaluation of aerobic granulation performance bioaugmented with the auto-aggregating bacterium Pseudomonas stutzeri strain XL-2 with heterotrophic nitrification-aerobic denitrification capacity

In this study, the possibility of an auto -aggregating bacterium Pseudomonas strain XL -2 with heterotrophic nitrification -aerobic denitrification capacity for improving granulation and nitrogen removal was evaluated. The results showed that the supplementation of strain XL -2 promoted granulation, making R1 (experimental group with strain XL -2) dominated by granules at 14 d, which was 12 days earlier than R2 (control group without strain XL -2). This was attributed to the promotion of extracellular polymeric substances (EPS) secretion, particularly proteins by adding strain XL -2, thereby improving the hydrophobicity of sludge and altering the proteins secondary structures to facilitate aggregation. Meanwhile, adding strain XL -2 improved simultaneous nitrification and denitrification efficiency of R1. Microbial community analysis indicated that strain XL -2 successfully proliferated in aerobic granule sludge and might induce the enrichment of genera such as Flavobacterium and Paracoccus that were favorable for EPS secretion and denitrification, jointly promoting granulation and enhancing nitrogen removal efficiency.