Study On Nitrogen Removal Performance Of Biological Fluidized Bed And Step-feed A/O Combined Process Based On Simultaneous Nitrification And Denitrification

Sewage treatment technology has the existing problems,such as low organic loading rate,nitrogen removal effect is not stable and so on.In recent years,the step feed A/O process has recieved widely attention of scholars at home and abroad.The experiment combined step feed A/O process with biological fluidized bed.The process has the following characteristics,stable nitrogen removal efficiency of the system greatly,sludge concentration,no external carbon source,without the nitrified liquid recirculation and strong capacity of resisting impact load etc..Process of the research is using theoretical analysis,experimental validation and modeling methods,in-depth studied on fluidized bed step feed A/O process for nitrogen removal efficiency.At the same time,the treatment effect improved by adjusting the system running parameters.The process has high efficiency and low energy consumption and reactor has the advantages of simple structure.It is suitable for application to wastewater denitrification and existing sewage treatment plant upgrading reconstruction.Fluidized bed step feed A/O process flow distribution method are studied through the theoretical analysis,including the carbon and nitrogen score distribution method and load equal allocation method.Respectively,from fully meet and complete nitrification and denitrification as a starting point,tests were conducted on the distribution of flow,and derived the optimal shunt coefficient formula.Finally,compared the suitable conditions of the two distribution method,using carbon and nitrogen score matching method is more suitable.The oxygenation testing determined the test early filling rate.Finally,compared the suitable conditions of the two distribution method,using carbon and nitrogen score matching method is more suitable for.The oxygenation of testing to determine the test early filling rate.When the filling rate was 40%,the system has the best effect of oxygen transfer.After the reactor start up,the removal of organic matter and nitrogen are good on the process of start up stage.Experimental study on system operation parameters on nitrogen removal was studied,including C/N ratio,HRT,sludge return ratio,volume ratio of anoxic zone and aerobic zone,filling rate,dissolved oxygen concentration.The results showed that:The higher the C/N ratio,the greater removal rate of TN,but when C/N ratio is higher than 8,increased gradually become slow;when HRT is greater than 8h,nitrogen efficiency is improved slowly.To enable the efficient operation of the system,using 8h as the HRT;Expand the anoxic zone occupied volume can enhance the denitrification performance,so as to improve the TN removal rate;Sludge reflux ratio for the system effects of nitrogen removal efficiency was not significant.Considering from the energy saving low carbon,50%reflux relatively is appropriate;Considering the operation effect and cost,40%dosage is appropriate;With the increasing of DO concentration,the TN removal efficiency increases first and then decreases,when the concentration of DO was 1.5mg/L,TN removal effect is the best.The actual operation of the process by the concentration of DO was 1.5mg/L.In the experimental process,reactor aerobic zone nitrogen loss phenomenon is obvious,the experiment studied the different DO aerobic zone of simultaneous nitrification and denitrification process,under the concentration of four stage aerobic zone SND rate,the aerobic zone of simultaneous nitrification and denitrification,aerobic zone occurrence mechanism of simultaneous nitrification and denitrification dynamics.The test results show that,the total loss of the aerobic zone nitrogen reactor is larger than that of nitrogen assimilation of daily consumption of microbial biomass.The results show that,low DO system is conducive to the smooth conduct of the SND,different aerobic zone SND rate have bigger difference,the front end effect is good.According to the classical dynamics of activated sludge model,the dynamics model of simultaneous nitrification and denitrification has deduced.The study shows,biological fluidized bed step feed A/O process is a kind of energy-saving,high efficiency,stable sewage denitrification process.Aerobic zone of simultaneous nitrification and denitrification phenomenon can be used in new construction and renovation of the sewage treatment plant,and achieve the best ginseng tens system by adjusting the operating conditions.