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

Abstract

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\xa0mg/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\xa0min of aerobic and 21\xa0min of anoxic) and rising influent ammonium concentration temporarily (lasted 31\xa0days). 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.