Achieving simultaneous nitritation, anammox and denitrification (SNAD) in an integrated fixed-biofilm activated sludge (IFAS) reactor: Quickly culturing self-generated anammox bacteria

In this study, by inoculating nitritation suspended sludge, simultaneous nitritation, anammox and denitrification (SNAD) was established quickly in an integrated fixed-biofilm activated sludge (IFAS) reactor to treat high-ammonia municipal wastewater. Results showed that, deep-level total nitrogen and chemical oxygen demand removal efficiencies (92.8% and 78.8%, respectively) were achieved, and their effluent concentrations were 13.2 and 39.3 mg/L, respectively. Excess generation of nitrate was once occurred under continuous aerobic condition, but it could be solved by suppressing nitrite oxidizing bacteria activity stably via switching to intermittent aeration mode (alternate 7 min of aerobic and 21 min of anoxic) and rising influent ammonium concentration temporarily (lasted 31 days). High-throughput sequencing analysis revealed that, Candidatus_Brocadia, as dominant anammox bacteria, was self-generated in flocs (2.93%) but mainly biofilm (7.67%), whereas uncultured_f_Nitrosomonadaceae as ammonia oxidizing bacteria was mainly found in flocs (2.4%). This work not only demonstrated that anammox bacteria could be self-generated and retained in the SNAD-IFAS system, but also suggested a promising application of the SNAD-IFAS in wastewater treatment plants. [Display omitted] •SNAD-IFAS system was fast established by inoculating nitritation suspend sludge.•High TN and COD removal efficiencies of 92.8% and 78.8% were achieved in SNAD-IFAS.•Both intermittent aeration and high influent NH4+-N could effectively inhibit NOB.•Candidatus_Brocadia-AAOB was self-generated in flocs (2.93%) and biofilm (7.67%).•SNAD-IFAS might be applied in sidestream of conventional WWTPs for advanced BNR.