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 algal-bacterial granular bioreactor and its related nitrite accumulation mechanism. After 150-days operation, partial nitrification algal-bacterial granulation bioreactor was achieved under the 200 µmol/(m2·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.