Study On Denitrifying Phosphorus Removal Performance Of Bio-flocculation-hydrolysis And Acidification-A~2/O Combined Sytem

The combined system used in this experiment mainly consists of biological flocculation process, hydrolysis and acidification process and anaerobic-anoxic-oxic process. The characteristic of this system is that part of particulate, colloidal organics in influent wastewater collected by biological flocculation process and transformed into small subclass organic matter which can be easily used in the hydrolysis and acidification process. The product will be added to the anoxic reactor as carbon sources to improve the efficiency of denitrification and phosphorus removal in the system.The experiment content in this test is denitrifying phosphorus removal, mainly study the effect of the mixture reflux ratio and the sludge reflux ratio to denitrifying phosphorus removal in the combined system. To investigate the effect of the mixture reflux ratio,the sludge reflux ratio was set as 100%, and the mixture reflux ratio was set as 100%, 200%,300% and 400% respectively, To investigate the effect of the sludge reflux ratio, the mixture reflux ratio was set as 300%, and the sludge reflux ratio was set as 60%, 80% and100% respectively, then analyzed the changes of the TP, COD and TN in the different situation and calculate the percentage of denitrifying phosphorus removal in the anaerobic pool according to the material balance equation.The results of this evperiment are as follows:(1) when discuss the effect of the mixture reflux ratio,the results show that, with the increasing of the mixture reflux ratio, the trend of the proportion of denitrifying phosphorus removal increased first and then decreased, the proportion was 11.17%,18.99%, 26.22% and 20.43% respectively. But the mixtue reflux ratio has little effect on the removal of COD. The qualities of effluent meet the standard of the designation and reach the A standard of Discharge standard of pollutants for municipal wastewater treatment plant. When the mixtue reflux ratio was 100%, the concentration of TN can’t meet the standard of designation. The removal proportion of TN in other three conditions are better, the concentration of TN can meet the standard of designation, the removal proportion of TN was 70.76% when the mixture reflux ratio was 300%, which was the best result in the four conditions. Considering all the elements such as the efficiency of denitrification, denitrifying phosphorus removal and so on, the optimal mixture reflux ratio we chosen was 300%.(2)When discuss the effect of the sludge reflux ratio, the results show that, with the increasing of the sludge reflux ratio, the trend of the proportion of denitrifying phosphorus removal decreased, the proportion was 19.04%, 14.05% and 9.41% respectively. So we should choose 60% as the best sludge reflux ratio considering the efficiency of denitrifying phosphorus removal. And the sludge reflux ratio has little effect on the removal of COD.The qualities of effluent meet the standard of the designation and reach the A standard in all conditions. With the increase of the sludge reflux ratio, the trend of the efficiencies of denitrification increased. The removal rate of TN were 58.76%, 66.88% and 67.93%respectively, when the sludge reflux ratio were 60%, 80% and 100%. The TN concentration of effluent can meet the standard of designation(below 15mg/L). But when r was 60%, the TN concentration of effluent was too high to exceed the designation. So considering the efficiencies of denitrification, we should choose 80% or 100% as the sludge reflux ratio.In summary, if only considering the the efficiency of denitrifying phosphorus removal,the best r is 60%, the best R is 300%. But considering the efficiencies of denitrification and denitrifying phosphorus removal, the best r is 80%, the best R is 300%.