Effect of C/N ratio and aeration rate on performance of internal cycle MBR with synthetic wastewater

Abstract

Effect of C/N ratio and aeration rate on performance of continuously operated internal circulation membrane bioreactor (ICMBR) was investigated thoroughly using synthetic domestic wastewater. The results show that COD and total nitrogen (TN) removal efficiencies were improved with the increase of C/N ratio under certain conditions (T = 25 °C, MLSS = 10 g/L, aeration rate was 0.15 m3/h, influent NH3-N concentration was 20 mg/L, influent NO3--N concentration was 100 mg/L, and HRT = 12 h). Meanwhile, a steady ammonia nitrogen (AN) removal rate (~80%) was obtained when C/N ratio increased from 2:1 to 6:1. Furthermore, when C/N ratio was 6:1 and aeration rate was 0.15 m3/h, average removal rates of COD, AN, and TN reached 98.5, 97.4, and 52.6%, respectively. Additionally, the improvement in activity of denitrifying bacteria could increase TN removal rate at a lower aeration rate. Under the optimal operation parameters (C/N ratio of 6:1 and aeration rate of 0.05 m3/h), the high average removal efficiencies of COD (96.0%), AN (96.4%), and TN (81.0%) were obtained by ICMBR. Finally, the membrane fouling was unobvious during this experiment process.