Biological denitrification in an anoxic sequencing batch biofilm reactor: Performance evaluation, nitrous oxide emission and microbial community

The present study evaluated the performance of biological denitrification in an anoxic sequencing batch biofilm reactor (ASBBR) and its nitrous oxide (N2O) emission. After 90 days operation, the effluent chemical oxygen demand and total nitrogen removal efficiencies high of 94.8% and 95.0%, respectively. Both polysaccharides and protein contents were reduced in bound EPS (TB-EPS) and loosely bound EPS (LB-EPS) after biofilm formation. According to typical cycle, N2O release rate was related to the free nitrous acid (FNA) concentration with the maximum value of 3.88 μg/min and total conversion rate of 1.27%. Two components were identified from EEM-PARAFAC model in soluble microbial products (SMP). Protein-like substances for component 1 changed significantly in denitrification process, whereas humic-like and fulvic acid-like substances for component 2 remained relatively stable. High-throughput sequencing results showed that Lysobacter, Tolumonas and Thauera were the dominant genera, indicating the co-existence of autotrophic and heterotrophic denitrifiers in ASBBR.