Formation characteristics of algal-bacteria granular sludge under low-light environment: From sludge characteristics, extracellular polymeric substances to microbial community

In this study, the formation characteristics of algal-bacteria granular sludge (ABGS) under low-light environment (80, 110, and 140 mu mol/m2/s) were investigated. The findings revealed that the stronger light intensity favored the improvement of sludge characteristics, nutrient removal performances, and extracellular polymeric substance (EPS) secretion at the growing stage, which were more preferential to facilitate the formation of ABGS. However, after the mature stage, the weaker light intensity ensured more stable operation of the system, as shown by contributing to sludge settlement performance, denitrification, and EPS secretion. According to the results of high-throughput sequencing, the dominant bacterial genus of the mature ABGS cultured under low light intensity were all Zoogloe, while the dominant algal genus was different. For the mature ABGS, the 140 and 80 mu mol/m2/s light intensity had the most significant activation effect to the functional genes related to carbohydrate meta-bolism and amino acid metabolism, respectively.

Automated summary

The formation characteristics of algal-bacteria granular sludge (ABGS) under different light intensities were investigated. It was found that stronger light favored the improvement of sludge characteristics and nutrient removal performances during the growing stage, while weaker light ensured stable operation of the system during the mature stage. The dominant bacterial genus in mature ABGS cultured under low light intensity was Zoogloe, and different algal genus were dominant.