Effect Of Nitrogen And Phosphorus Removal From Sewage With Improved A~2/O Process

The treatment efficiency of nitrogen and phosphorus in domestic wastewater was analyzed based on an improved A2/O (anaerobic-anoxic-oxic) process in comparison with the traditional one. Versatile improvements were proposed to promote the removal efficiency of nitrogen and phosphorus. Packing media was added in the bioreactor to create a separation-phase culture environment for microorganisms with the purpose of enhancing their growth. Compared with the traditional serial connected way, the way of parallel connected reactors was proposed to reduce carbon source competition of microorganisms; the regulating reservoir was added to homogenize the raw water composition. Nitrification liquid was refluxed from the outlet, in which way reduced the influence on the treatment process caused by dissolved oxygen.The improved process was adjusted in the initial phase to reach a stable operation and was invulnerable to various influents. Results show that the average removal efficiency of CODcr, NH3-N, TN and TP corresponds to78.4%,95.9%and86.4%. The system is efficient on the removal of turbidity with99.5%of removal rate achieved, and the effluent can be maintained clear.Water distribution ratio was harnessed at6:4,5:5and4:6respectively in anoxic and anaerobic tank, the results indicate that the removal efficiency of CODcr and ammonium nitrogen doesn’t make much great change and this parameter still has a good effect on the removal of contaminants. The value of TP and TN shows high removal efficiency in resin with high influent ratio. In order to get the hybrid removal for both nitrogen and phosphorus, the optimum influent water distribution ratio was manipulated at5:5.System operated stable under the condition of150%,200%and250%of nitrified liquid recycle ratio, and this didn’t have great influence on the removal of CODcr, TN and TP. The removal efficiency of TN is in proportion with nitrified liquid recycle ratio and increases from70.8%to71.9%when recycle ratio varies from200%to250%, and it doesn’t change much. All in all, the optimal recycle ratio is determined at200%despite of the slightly change of the results obtained.The system exhibited a stable remove on CODcr with effluent concentration lower than50mg/L under various DO concentrations. The optimum parameter of DO corresponds to the operation site2(former part of2mg/L, latter part of1.6mg/L), showing that2.2mg/L of NH3-N (i.e.,92.7%of removal efficiency) and12.1mg/L of TN (i.e.,70.8%of removal efficiency) in effluent have achieved.The results show that the improved A2/O process has great significant impact on the reconstruction and update of sewage plant by integrating the separated nitrified liquid-sludge recycle, the parallel connected influent way and the supplement of volcanic and combined packing media method.