An intermittently aerated membrane bioreactor (IAMBR) process is designed to achieve greater removal efficiency of organic matter and nutrients than a regular membrane bioreactor (MBR) through the control on and off of an aerator. In this paper, we have investigated Oxidation/Reduction Potential (ORP) and Dissolved Oxygen (DO) values compared to NH4+-N and NO3-N concentrations at SRTs of 20, 30 and 40 days and C/N ratios of 4.5, 7, and 10. Additionally, the paper addresses a comprehensive approach to evaluate ORP as an appropriate factor for the auto-control of IAMBR process on the nitrification and denitrification and present ΔORP/Δt curve to confirm accurate completion time of aeration on and off. As the results of ORP and DO curve, it is proven that points of ORP bending and knee are appropriate factors for auto-control of the process in both aeration on and off time and ORP as well as DO relate to the dynamic behavior of nutrient concentration during a cycle. A peak point at aerobic state and a slump point at anoxic state on ΔORP/Δt curve obviously present the ORP bending point. Hence, it could find that peak point and slump point indicated the relatively accurate completion time of nitrification and denitrification respectively in IAMBR.

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