Inorganic nitrogen removal of toilet wastewater with an airlift external circulation membrane bioreactor

Removal of inorganic nitrogen (inorganic-N) removal of toilet wastewater with a pilot-scale airlift external circulation membrane bioreactor (AEC-MBR) was studied in this paper. The results showed that in the AEC-MBR, with a limited addition of alkalinity and the volumetric loading rates of inorganic-N at 0.19-0.40 kg inorganic-N/(m3·d), the desired nitrification and denitrification were achieved. Furthermore, the effects of pH and DO on inorganic-N removal were examined. Under the condition of MLSS at 1.56-2.35 g/L, BOD5/NH4 -N at 1.0, pH at 7.0-7.5 and DO at 1.0-2.0 mg/L, the removal efficiencies of NH4 -N and inorganic-N were 91.5% and 70.0% respectively in the AEC-MBR. The cost of addition of alkaline reagent was approximately 0.5-1.5 RMB Yuan/m3,and the energy consumption was approximately 0.72 kWh/m3 at the flux of 8 L/(m2·h).