1. School of Municipal and Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; 2. School of Ecological Environment, Ningxia University, Yinchuan 750021, China; 3. China Wine Industry Technology Institute, Yinchuan 750021, China
Abstract：In this study, an integrated fixed-film activated sludge (IFAS) system was established to explore the feasibility of treating low carbon/nitrogen (C/TN=1.63) wastewater by coupling partial denitrification (PD) suspended sludge and anaerobic ammonia oxidation (Anammox) biofilm. During the experiment, As a result, the TN removal efficiency could be up to (90.7±0.1)% with the effluent TN of (5.07±0.2) mg/L, and the Anammox pathway contributed to TN removal reached (86.61±3.4)%. And the contribution of biofilm to anammox activity was 100%, μ(NO3--N) accounted for 99.32%, μ(NO2--N) accounted for 99.22% in the suspended sludge; indicating that partial denitrification process was dominated in the suspended sludge and Anammox process in the biofilm. Compared with that before coupling, the nitrate reductase (Nar) in the suspended sludge increased from (0.43±0.05) to (0.49±0.09) μmol/(mg protein·min). The nitrite transformation ratio significantly increased from (70±2.2)% to (90.01±2.3)%. In other words, the competition of nitrite between denitrifying bacteria and anaerobic ammonia oxidation bacteria (AnAOB) partially strengthened the partial denitrification process in the suspended sludge. Illumina MiSeq sequencing results show that the abundance of Candidatus_Brocadia, the dominant bacteria in the biofilm (33.61~33.43)%, had no obvious change before and after coupling. In the phase of suspended sludge, the abundance of Prosthecobacter, Ferruginibacter, and OLB8 tended to increase. Evidently, the PD/A technology in the IFAS system will provide technical guidance for its practical application.
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