[14] and [15]. Meanwhile, raw wastewater should be concentrated to facilitate the application of AD and nitritation–anammox. Direct membrane filtration (DMF) of wastewater has recently gained attention, because it provides the opportunity of concentrating organics and nutrient via membrane concentration; its other advantages include high-quality effluent, simple design, and simple maintenance [16].
In the present study, we explored a membrane combined process of AD and nitritation–anammox, which includes an anaerobic membrane bioreactor (AnMBR) and an MBR applied in completely autotrophic nitrogen removal over nitrite process (CANON). Additionally, a dual membrane device [ultrafiltration (UF)–reverse osmosis (RO)] is used as pretreatment to up-concentrate municipal wastewater for elevating the concentrations of COD and N from municipal wastewater. Thus, in AnMBR, the organic C of concentrate from UF and RO was removed to generate biogas. In CANON MBR, concentrated ammonium was partially oxidized to nitrite by AerAOB, and nitrite and remaining ammonium were converted to nitrogen gas by anammox [17]