Comparisons of nitrogen and phosphorus removal efficiency in A²/O process, UCT process, MUCT process, enhanced phosphorus removal process and inverted A²/ O process based on GPS-X simulation

By using the GPS-X software, the enhanced phosphorus removal (EPR)process was simulated in this study. The comparisons among nitrogen and phosphorus removal efficiency of traditional A²/O process, University of Cape Town (UCT) process, Modified University of Cape Town (MUC) process and inverted A²/O process were conducted, in order to determine the best process under the same conditions of construction investment and running cost. The results showed that the simply reversed A²/O process exhibited poor total phosphorus (TP) removal efficiency under low carbon level. The effluent water qualities of the other three processes under low, medium and high levels of carbon source met the first B level criteria in Discharge Standard of Pollutants for Municipal Wastewater Plan (GB18918-2002) for China. The ranges of removal efficiencies of TP, TN, NH₄⁺-N and COD were 63.15% ∼ 94.91%, 55.38% ∼ 77.89%, 96.91% ∼ 97.70% and 90.89% ∼ 93.66%, respectively. Denitrifying phosphorus removal occurred in anoxic tank of EPR process. The phosphorus accumulation concentration was 6.91 mg/L, and the maximum phosphorus released in anaerobic tank was 24.01 mg/L, and the higher P release gave the EPR process a high P removal effiency. Except for the TN which met the first B level criteria (GB18918-2002), TP, NH₄⁺-N and COD met the first A level criteria GB18918-2002), above that, the process was feasible. Inverted A²/O process exhibited the highest nitrogen removal efficiency for its sufficient carbon source in anoxic tank.