Effect of dissolved oxygen on the performance of a step-feed hybrid MBR process treating synthetic domestic wastewater

Abstract

Abstract An innovative step-feed Anaerobic-(Oxic/Anoxic) n -Membrane Bioreactor [An-(O/A) n -MBR] process was developed to treat synthetic domestic wastewater. Performance of the lab-scale system was investigated at different dissolved oxygen (DO) concentration (0.4–2.4 mg/L) in the aerobic tank of the multiple A/O zone. The results showed that, under the conditions imposed, the DO level has little influence on chemical oxygen demand removal and the removal efficiency was more than 94% throughout the operation. However, DO levels have great influence on nitrogen and phosphorus removal. Better nitrification efficiency could be obtained when DO was in the range of 0.8–2.4 mg/L; the ammonia removal efficiency was more than 99%. High total nitrogen (TN) and total phosphorus (TP) removal performance can be obtained when DO was in the range of 0.8–1.2 mg/L; the average removal efficiency was 74.8 and 71.4%, respectively. In this condition, DO can meet the demand of nitrification and phosphorus uptake simultaneo...