Performance characteristics and bacterial community analysis of a novel two-step-feed three-stage A/O-MBBR system for nitrogen removal in municipal wastewater

To obtain a high nitrogen removal efficiency and fully use the carbon sources in raw wastewater, a novel two-step-feed three-stage anoxic/oxic (A/O)-moving bed biofilm reactor (MBBR) system with ten chambers was established for municipal wastewater treatment. The designed ten chambers in the 2F-3S-A/O-MBBR system played different roles in nitrogen and organic removals, and they accomplished the task of achieving stable high nitrogen removal efficiency at different temperatures together. Concretely, the average total inorganic nitrogen (TIN) removal efficiency was improved to 72.88 % from 61.55 % without any external carbon sources by the second-stage A/O-MBBR subsystem due to the two-step-feed configuration, and it was further improved to 91.42 % by the third-stage A/O-MBBR subsystem due to the use of the external carbon sources. Specific functional biofilms with different bacterial communities (r = 0.85, P ≤ 0.001) and functional genes of denitrification and nitrification (r = 0.63, P ≤ 0.001) were formed in 4 groups of functional zones, including the first-stage anoxic, second-stage anoxic, third-stage anoxic and oxic chambers. This study developed an efficient 2F-3S-A/O-MBBR biological nitrogen removal process and investigated the performance characteristics and bacterial community to provide fundamental support for the application of this process.