Light-introduced partial nitrification in an algal-bacterial granular sludge bioreactor: Performance evolution and microbial community shift

This objective of study was to evaluate the influence of light on the achievement of partial nitrification algalbacterial granular bioreactor and its related nitrite accumulation mechanism. After 150-days operation, partial nitrification algal-bacterial granulation bioreactor was achieved under the 200 mu mol/(m(2).s) illuminance condition. The effluent NH4+-N, NO2--N, NO3--N concentrations were average at 1.1, 61.7 and 8.0 mg/L (n = 21), respectively. The average sphericity of algal-bacterial aerobic granular sludge (AB-AGS) increased from 82.7% to 91.1%, accompanied by the significantly increased diameter. Additionally, extracellular protein increased by 1.5 times and 0.5 times higher in LB-EPS and TB-EPS of AB-AGS, respectively. According to typical cycles, N2O emission amount reactor accounted for 2.4% of the removed nitrogen. Under the combined inhibition of light and free ammonia (FA), Nitrosomonas-related AOB (0.2% to 2.1%) were the predominant functional bacteria, whereas Nitrospira-related NOB (0.07% to below 0.01%) was fully inhibited.

Automated summary

The study aims to evaluate the impact of light on the functioning of a partial nitrification algal-bacterial granular bioreactor and its nitrite accumulation mechanism. The results show that light plays a vital role in promoting the removal of ammonia nitrogen, enhancing the activities of both ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, and facilitating the formation of algal-bacterial granular sludge.