Research on Optimal DO Concentration in Aerobic Pool of Simultaneous Biological Nitrogen and Phosphorus Removal Process

A pilot-scale nutrient removal activated sludge system, based on A2/O configuration, was used to treat municipal sewage. In the experiment, the nutrient removal affected by DO concentration in the aerobic stage was observed at given operating condition. Results showed the effect of DO concentration on COD removal was much smaller, and the removal rate of COD, had a tendency to rise with the increase of DO concentration under 3.0mg/L. The optimal DO concentration for total nitrogen removal was between 1.5 to 2.5mg/L, lower or higher would increase the effluent concentration. Anaerobic phosphorus release and anoxic phosphorus uptake were distinctly affected by DO concentration, but the effluent total phosphorus stable. In the system, denitrifying and phosphorus uptake were both observed, but it was denitrifying phosphorus removal or not was not judged.