Notice of RetractionEvaluation of Nitrogen and Phosphate Removal in Full-Scale Modified A²/O Process

Notice of Retraction

After careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE´s Publication Principles.

We hereby retract the content of this paper. Reasonable effort should be made to remove all past references to this paper.

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A modified A²/O biological system is applied for the sewage treatment in a full-scale WWTP. Compared with conventional A²/O process, this modified A²/O process adds a pre anaerobic stage, and introduces inflow into pre-anaerobic, anaerobic and anoxic tank simultaneously. These measures bring about a further improvement of nitrogen and phosphorus in urban wastewater. The monitoring results for one year show that the influent concentrations of BOD, NH₄-N, TN, TP are 21.9-263.0, 16.3-30.8, 9.7-668 and 1.0-11.3 mg L-l, respectively. After the treatment of modified A²/O process, the average effluent concentrations of BOD, NH₄-N, TN, TP are 6.5, 0.6, 10.4, 0.6 mg L-l, and the average removal rates are 93.5%, 96.9%, 61.5% and 78.9%, respectively. The effluent quality meets the 1 B level discharging criteria in China. The operation results show that the modified A²/O process can achieve a high reduction of nitrogen and phosphorus in spite of the fluctuation of influent, and can be widely used in municipal wastewater treatment plants.