Enhancing nitrogen removal of aerobic granular sludge with optimization of dissolved oxygen spatial distribution

This study aims to investigate the impact of the aerator position on the dissolved oxygen spatial distribution and stability of aerobic granular sludge (AGS). Three SBRs with 2.5 mm mesh screen were established under condition of different aerator positions, the aerators of R1, R2 and R3 were set at the bottom, 1/6 and 1/3 height of reactors, respectively. The results revealed that R2 was more favorable to improve the sludge settling behavior and structural stability of AGS, resulting in 83.7 +/- 1.4 % of total nitrogen (TN) removal. However, R3 led to an anoxic environment at the bottom of reactor, which prevented the formation of AGS and made a large amount of sludge lost. DO distribution indicated that oxygen content at the bottom of R2 was at the optimum range of 18.9 %-20.1 %, being beneficial to realize the simultaneous nitrification-denitrification. Therefore, the functional microbes of Zoogloea spp. (17.4 %), Paracoccus spp. (12.5 %), Thaurea spp. (13.6 %) and Rhodobacter spp. (10.8 %) were highly enriched in R2. Overall, raising the aerator position to 1/6 height of reactor led to 7.4 % increase of TN removal efficiency and 15.4 % decrease of energy consumption, which favors the application of AGS technology.

Automated summary

This study investigates the impact of aerator position on the distribution and stability of dissolved oxygen in aerobic granular sludge (AGS). The results suggest that placing the aerator at 1/6 height of the reactor improves sludge settling behavior and structural stability, resulting in higher total nitrogen removal efficiency and lower energy consumption.