Abstract
Ammonia-rich lagoon supernatant has a low alkalinity/nitrogen ratio, which is ideal for single reactor nitritation-denitritation operation. In the present study, an integrated fixed film and activated sludge system in sequencing batch mode (IFAS-SBR) was operated at 21 °C for 140 days. The stability and feasibility of nitritation-denitritation performance was evaluated, and the microbial activities and microbial community dynamics were investigated. With a hydraulic retention time (HRT) of 2 days, the IFAS-SBR achieved a stable inorganic nitrogen removal rate of 98 %. Nitritation and denitritation activities were both higher in suspended flocs as compared to biofilm. The dominant nitrifying and primary denitrifying genera were Nitrosomonas and Thauera, respectively. During long-term operation, the relative richness of Nitrosomonas and Thauera increased in both biofilm (from 0.27 % to 1.12 % and from <1 % to 14.2 %, respectively) and flocs (from 0.8 % to 2.43 % and from 42.6 % to 54.6 %, respectively). The specific activity test and microbial community analysis revealed that the flocs contributed more on both the nitritation and denitritation processes.