Feed distribution based on ammonium introduced in a sequencing batch reactor (SBR) was applied to a 24 m3 single-stage deammonification to treat reject water. With field experience, the conventional SBR exhibited limited adaptability to fluctuations in influent load. This study proposed a new approach capable of coping with the influent fluctuations. The pH and alkalinity were clustered as factors that affect the NRE, which was related to the ammonium behavior in the SBR sub-cycle. To establish the real-time control, the pH value, which has the highest correlation with them, was applied. In the SBR feeding phase, their variations rather than pH values were useful in predicting the ammonium behavior. This was formulated so that the reject water in the anoxic and aerobic phases was introduced semi-continuously. In the aerobic phase, the pH was suitable for determining the partial nitritation break-point. Its efficacy was verified in a pilot. A stable NRE of 90 +/- 2.1 % was achieved even though the influent nitrogen fluctuated from 508.0 to 744.9 mg/L. In addition, as the SBR parameters (HRT, aerobic cycle, and exchange ratio) were optimized in real-time, the nitrogen removal rate further improved by 0.15 kg/m3/d.
