Impact of reflux on nitrogen and phosphorus removal performance of a pilot scale of intermittent A/O-MBR

To enhance the quality of wastewater treatment plant's (CASS process) effluent in Foshan to satisfy the water reuse standards, the impact of reflux ratios and reflux modes on nitrogen and phosphorus removal performance of a pilot scale of intermittent A/O-MBR fed with municipal wastewater was studied in this paper. The results showed that the reflux ratios and reflux modes had no remarkable influence on removal of COD_Cr and NH₄⁺-N, and the concentrations of COD_Cr and NH₄⁺-N in the effluent both reached the primary standard A of <Discharge standard of pollutants for municipal wastewater treatment plant> (GB18918-2002). The reflux ratios and reflux modes had significant influence on removal of TN and TP. The removal efficiencies of TN and TP were poor with a continuous reflux and a larger reflux ratio (350%); When the reflux ratio was 130%, the continuous mode was propitious to TN removal, and the removal efficiency could reach (48.00±10.05)%, what's more, the concentration of TN in the effluent reached the primary standard A, while the intermittent mode was also propitious to TP removal, the removal efficiency could reach (78.27±23.41)%, and the concentration of TP in the effluent reached the primary standard B.