Biological nutrient removal in a continuous anaerobic–aerobic–anoxic process treating synthetic domestic wastewater

A continuous anaerobic–aerobic–anoxic (AOA) process was established to remove nutrients from domestic wastewater without the addition of external carbon source. The AOA process was based on an enhanced biological phosphorous removal (EBPR) system with influent COD, NH4+–N and PO43-–P concentrations of 300, 50 and 3.8 mg/L, respectively. Nitrogen and phosphorous were removed simultaneously driven by internal carbon sources under low dissolved oxygen (DO) condition. The removal efficiencies of total nitrogen (TN) and PO43-–P reached above 90% and 99% when the DO concentration of the aerobic unit was controlled at 1.2 ± 0.2 mg/L and the HRT of the aerobic and anoxic units were at 2 h and 4 h, respectively. Denitrification was mainly driven by poly-β-hydroxybutyrate (PHB), which increased via shortening the aerobic HRT. Results demonstrated that TN was removed via simultaneous nitrification and denitrification (SND) and denitrifying phosphorous removal in the continuous AOA process.

► A continuous post-anoxic process (AOA) with low DO level was established.
► Nutrient removal was improved by controlling aerobic HRT and DO concentration.
► TN was removed efficiently via SND and denitrifying phosphorous removal.
► Denitrification was mainly driven by poly-β-hydroxybutyrate (PHB).