Using the synthetic domestic sewage as treatment object, focused on the A~3/O-MBR process characteristics of denitrification and phosphorus removal when nitrate recycling ratio(α) of 100%, and internal return ratio(R) as 100%, 150%, 200% respectively. The results showed that the removal rates of COD, NH_4+~-N and TN are almost not influenced by the change of internal recycle ratio, and the effluent concentrations of COD, NH_4+~-N and TN less than 50, 2, 20 mg/L respectively. As while as the average removal ...