The integration of methanogensis with simultaneous nitrification and denitrification in a membrane bioreactor

A staged anaerobic and aerobic membrane bioreactor (MBR) was constructed. The membrane module was submerged in the aerobic zone of the reactor, and was operated under the mode of alternative suction and air backwash. Air backwash and aeration around the membrane module served as the cleaning of the membrane, resulted in the steady operation of the reactor at the flux of 5-14 l m−2 h−1 for up to 200 h without any additional cleaning. The efficiency of COD removal was more than 99% at up to 10.08 g COD l−1 per day of the volumetric loading rate (VLR). The efficiency of ammonium removal was 100% at a VLR of 0.18 g NH4+-N l−1 per day. Sixty to 80% of COD was anaerobically biodegraded in the anaerobic zone of the reactor and this produced a great amount of methane. Methane passed to the aerobic zone of the reactor and could serve as a carbon source for denitrification. Intermittent aeration allowed nitrification and denitrification to occur simultaneously in the aerobic zone of the reactor. The capacity for ammonium removal reached up to 0.5 g NH4+-N l−1 per day. Eighty-four to 94% of the total oxidised nitrogen converted from the oxidisation of ammonium was denitrified.