A Contastive Study Among The A~2/O Process, The Inverted A~2/O Process And The Pre-anoxia A~2/O Process On Treatment Of Municipal Sewage.

In recent years, A lots of environmental problems happen with the rapid improvement of our country economic development, in which the water eutrophication caused by the wastewater contains nitrogen and phosphorus. Most of swage plants are secondary biological treatment process which has limition removal of nitrogen and phosphorus. Making these swage plants which have not the nitrogen and phosphorus removal simultaneously capacity upgrade become urgent when the water eutrophication is increasingly serious and the discharge standard of nitrogen and phosphorus becomes increasingly strict.Meanwhile, the prevalence rate of swage plant in our country is quite low especially in Middle and Small Towns.lots of swage plants which have the nitrogen and phosphorus removal simultaneously capacity need to be built.Therefore,it is important to study the nitrogen and phosphorus removal simultaneously process of sewage.This paper studies the development and change of nitrogen and phosphorus removal simultaneously process, We use the GDFB of one sewage treatment plant as a simulation object and use actual sewage water as a pilot. Compare and analyse the nitrogen and phosphorus removal of the A2/O process, the inverted A2/O process and the pre-anoxia A2/O process. The actual water quality tests:COD208-412mg/L, BOD598-228 mg/L,NH4+-N18.9-36.8 mg/L,TN20.1-49.8 mg/L,TP2.5-7 mg/L.The test studies nitrogen and phosphorus removal of the A2/O process and the inverted A2/O process in different reflux ratios and mlss.Futher,we also study nitrogen and phosphorus removal of the pre-anoxia A2/O process in different influent conditions comparing with the A2/O process.Last changing the influent way make the pre-anoxia A2/O process more optimizing.This test has the following conclusions:1.On the same reflux ratio condition, the inverted A2/O process has better nitrogen removal than the A2/O process,however, the A2/O process has obviously better phosphorus removal than the inverted A2/O process.2. Within the limit of the mixed liquor reflux ratio,the nitrogen removal of the A2/O process and the A2/O process becoms better and better along with the reflux ratio increasing,but too high reflux ratio can make the nitrogen and phosphorus removal decline in the same time.The sludge reflux ratio changing is bound up with nitrogen removal of the A2/O process, different with the A2/O process, the sludge reflux ratio changing is bound up with phosphorus removal of the inverted A2/O process.3.The A2/O process and the inverted A2/O process using 100% of the sludge reflux ratio and 200% of the mixed liquor reflux ratio are suitable considering the nitrogen and phosphorus removal and the economical factors. On this condition, using the A2/O process, TN of the effluent commonly belows 12mg/L and the removal is about 70%,and TP of the effluent commonly belows 0.5mg/L and the removal is about 90%. using the inverted A2/O process,TN of the effluent is about 10mg/L and the removal is about 70%,and TP of the effluent commonly belows lmg/L and the removal is about 84%.4.The suitable mlss is in favor of nitrogen removal.the sludge age is bound up with phosphorus removal,the phosphorus removal gets worse when the mlss improves. Considering the nitrogen and phosphorus removal simultaneously, the A2/O process and the inverted A2/O process using 3000mg/L mlss is in favor of them acquiring better nitrogen and phosphorus removal.5.The nitrogen removal of the pre-anoxia A2/O process is better than the A2/O process.The nitrogen removal of it can reach 74%.Comparing to 70% of the A2/O process,it improves about 4%.The two processes have roughly the same phosphorus removal, TP of the effluent commonly belows lmg/L and the removal is about 90%. Changing the influent way can improve the nitrogen removal of the pre-anoxia A2/O process on condition that having not an effect on organism and phosphorus removal. The nitrogen removal can reach 78%, TN of the effluent commonly belows 10mg/L. 6.Analyse the A2/O,the inverted A2/O and the pre-anoxia A2/O process, we has the conclusion:the pre-anoxia A2/O process is the best choice.This study has the role of reference and guidance for conventional secondary biological treatment process of sewage plants upgrade, and provides the appropriate basis for the same types of sewage plants.