Anaerobic-aerobic-anoxic shortcut nitrification coupled with simultaneous denitrifying phosphorus removal

A novel process consisting of anaerobic-aerobic-anoxic units is designed to achieve shortcut nitrification coupled with simultaneous denitrifying phosphorus removal,and its treatment performance with domestic wastewater was investigated at ambient temperature. This process could start-up quickly by adjusting pH 8.2～8.7 and DO 3～5 mg·L-1 in the aerobic reactor,and nitrite accumulation was obtained. DO was the main factor affecting nitrite accumulation in the steady operating period. The nitrite concentration accumulated to 5～10 mg·L-1 with DO 1.5～2.0 mg·L-1 in aerobic unit 1 and 0.5～1.0 mg·L-1 in aerobic unit 2,while the ammonia removal was above 90% in this system. Analysis of the contributions of COD,nitrite and nitrate to denitrifying phosphorus removal indicated that the denitrifying phosphorus removal using nitrite and nitrate as electron acceptors was achieved in the anoxic unit without addition of an external carbon source,and contributed about 80% to the total phosphorus removal.