Effect of re-aerobic tank HRT on the nutrient removal performance of a modified A2N process
后曝气池HRT对改进型A2N工艺脱氮除磷性能的影响

Biofilm was added in the re-aerobic tank in order to enhance nutrient removal performance of A2N denitrifying phosphorous removal process. Effect of re-aerobic tank hydraulic retention time (HRT) on the nutrient removal performance and simultaneous nitrification and denitrification (SND) in re-aerobic tank were investigated in this modified process treating domestic wastewater. High average total phosphorus (TP) removal efficiency of 90% and average total nitrogen (TN) removal efficiency of 75% could be achieved at re-aerobic tank HRT of 1.3 h. However, average effluent ammonium concentration was high (8.6 mg L-1) and SND was not observed. The average TP removal and TN removal efficiencies were 95% and 80%, respectively at re-aerobic tank HRT of 2.3h. Correspondingly, the effluent ammonium concentration was low than 2.2 mg L-1 and the net removed amount of TN via SND in re-aerobic tank was 2.42 mg L-1. After prolonging the re-aerobic tank HRT to 4h and 6h, the average TN and TP removal efficiencies decreased to 60%. The TN loss via SND did not increase distinctly with increasing of re-aerobic tank HRT, since less degradable COD was available in re-aerobic tank. It was demonstrated that the nutrient removal performance would be enhanced by adding biofilm and selecting a proper HRT in re-aerobic tank.