The Study On A~2/O Process For Treating Urban Sewage Nitrogen And Phosphorus Removal Performance

Urban sewage accounts for an important proportion of China's sewage discharge.If urban sewage is not treated,it will be discharged,which will damage the water environment.The A²/O process has the functions of simultaneous nitrogen and phosphorus removal,and is widely used in China's sewage treatment industry.In order to further study the treatment effect of A²/O process on urban sewage,this study used the actual influent of a county sewage treatment plant in Handan City as the treatment object,using A²/O process test.The device processes it.Sludge culture method with intermittent water inflow and continuous water inflow continuously,the sludge concentration rises above 4000 mg/L,and SV₃₀0 stabilizes between 20%and 30%.The removal rate of COD_Crr and NH₄⁺-N is stable at about 80%,the TN removal rate is stable at around 70%,and the TP removal rate is stable at around50%.At this time,the activated sludge has high activity and good sedimentation.The removal effect of various pollutants is stable.It is considered that the activated sludge cultivation is completed.This study includes two parts:single factor test and orthogonal test.The study mainly discussed the effects of hydraulic retention time?HRT?,mixture reflux ratio and sludge reflux ratio on the treatment effect of the A²/O process test device.The analysis result shows that 16h is the best operation condition for HRT,and the average removal rates of COD_Cr,NH₄⁺-N,TN and TP were 76.71%,87.92%,82.03%and 41.02%;the best operation condition for mixture reflux ratio is 200%,and the average removal rates of COD_Cr,NH₄⁺-N,TN and TP were 74.02%,88.29%,81.87%and 45.22%;the best operation condition for sludge reflux ratio is 200%,and the average removal rates of COD_Cr,NH₄⁺-N,TN and TP were 74.49%,89.29%,85.70%and 45.02%.Through orthogonal tests on HRT,mixed liquid reflux ratio,and sludge reflux ratio,the test results were analyzed for range and variance.In the removal rate of COD_Crr and TP,the order of influence of each factor on the reaction is:HRT>sludge reflux ratio>mixed liquor reflux ratio.In the removal rate of NH₄⁺-N and TN,the order of influence of each factor on the reaction is:HRT>mixture reflux ratio>sludge reflux ratio.The HRT has the most significant influence on various indexes.The HRT and the reflux ratio of the mixture have a significant effect on the TN removal rate,and other factors have no significant effect on the index.The best working condition were determined as follows:hydraulic retention time is 16 h,mixture reflux ratio is 200%,sludge reflux ratio is 100%.The study has instructive significance for urban sewage treatment with A²/O process,and provides with theoretical and data support for the parameter optimization of A²/O process.