Simultaneous Nitrogen And Phosphorus Removal In A/O Process

Water eutrophication problem caused by nitrogen and phosphorus discharged excessivly has become a environmental issue most concerned by human. It results of the requirements on emission of nitrogen and phosphorus increasing strictly in Sewage disposal standards. Thus, developing energy-efficient wastewater biological nitrogen and phosphorus removal process will be a new research focus in the field of water pollution controlling.Simultaneous nitrification and denitrification and denitrifying phosphorus removal is a new biological nitrogen removal process which was developed in the last few years. Not only this process may shorten the nitrogen removal pathway, but also omit the second(anoxic) tank, or reduce its size,.and save the construction cost further more. The simultaneous nitrification and denitrifying phosphorus removal via to nitrite can be achieved by controlling ammonia to be oxidized to nitrite only. Theoretically it can shorten reaction process further, and reduce carbon source and oxygen demand more.The experiment was carried out to research on the synthetic municipal wastewater in A/O process. The test researches the training process, removal efficiency, main factors of combining shortened simultaneous nitrification and denitrification and denitrifying phosphorus removal , with treatment object being simulated the urban sewage. It determines the best operating conditions to achieve the process of combining shortened simultaneous nitrification and denitrification and denitrifying phosphorus removal. At the basis of these studies, the change law of DO, temperature,sludge age and pH in the reaction process was studied .The results show that it achieves shortened simultaneous nitrification and denitrification and denitrifying phosphorus removal in A/O process by controlling DO, sludge age and pH . In the stable operation period,when the conditions of influent COD is 108.04²71.35mg/L(257mg/L), NH₄⁺-N is 21.60³0.55mg/L(28.50mg/L),TN is 23.51³4.74 mg/L(30.18mg/L),TP is 3.54⁷.18 mg/L(6.85mg/L), the best controlling range of factors in combining shortened simultaneous nitrification and denitrification and denitrifying phosphorus removal are:DO about 0.5¹.0mg/L, sludge age about 10¹5d, temperature about 15²5℃,pH about 7.0⁷.5. In the parameters of this process, the average effluent concentration of COD,NH₄⁺-N,TN and TP are 13～19mg/L,0.48～0.96mg/L,1.0～4.0mg/L and 0.30～0.86mg/L, the average removal rates are 92%～96%,96%～99%,89%～93% and 90%～94%.