Research On Rural Domestic Sewage Treatment Based On Improved AAO Process

Rural domestic sewage has many problems,such as wide sources,complex components,high nitrogen and phosphorus concentration and large fluctuation of water quality.The application of traditional AAO Process often can not meet the requirements of nitrogen and phosphorus removal.Therefore,in order to solve the contradiction between nitrogen and phosphorus removal that cannot be balanced by the traditional process.This study,with the goal of rural domestic sewage treatment in Zhongwei City,proposes a series of improvement methods.By adjusting the operation parameters,using two-point water inflow operation and adding bacterial agent,a set of high-efficiency nitrogen and phosphorus removal AAO process operation mode based on two-point water inflow was developed.In this study,the physical and chemical indexes of inlet and outlet water before and after the process improvement and the microbial community composition of the system were analyzed,and the nitrogen and phosphorus removal effects of the system on artificial simulated domestic sewage under different working conditions were investigated,and the following results were obtained:1.Optimum conditions for operating parametersThe internal and external reflux ratio of AAO system and Anoxic hydraulic retention time have a great impact on the denitrification effect of the process.When the Anoxic HRT（hydraulic retention time）is between 2.25 h and 3 h,the system has a good denitrification effect.In addition,a better TN removal effect can promote TP removal,but improving TN removal rate by increasing external reflux will have an adverse impact on TP removal.Therefore,it is necessary to improve TN removal rate by increasing internal reflux and reducing external reflux as much as possible.Therefore,it is necessary to improve the TN removal rate by increasing the internal reflux and reducing the external reflux as much as possible.The optimal operating parameters obtained in this study are V anaerobic:V anoxic:V aerobic=1:2:6,anoxic HRT=3h,and the internal and external reflux ratios are 250%and 50%respectively.2.Optimum water distribution ratio of two-point inflowWhen the two-point water inflow mode was adopted,with the increase of the proportion of water inflow in the anoxic area,the removal rate of TN increases first and then decreases.The results of this study show that when the influent ratio of anoxic tank is 0～20%,the TN removal effect increases gradually with the increase of influent ratio of anoxic tank;When the influent ratio is 20%～30%,the system can still maintain a good TN and TP removal effect;When the influent ratio exceeds 30%,with the increase of the influent ratio of the anoxic tank,the effect of nitrogen and phosphorus removal of the system will be worse and worse until the system cannot operate normally.3.Analysis of microbial community structureUsing two-point water inflow and adding bacterial agent changed the microbial community composition of the system and improved the relative abundance of functional microorganisms involved in nitrogen and phosphorus removal.In the two-point water inflow mode,the denitrifying phosphorus accumulation effect is enhanced,and the addition of bacterial agent makes the system have a strong denitrification effect of heterotrophic nitrification and aerobic denitrification.After adjusting the operation parameters,using two-point water inflow and adding bacterial agent,the effluent effect of AAO process is optimized.The effluent concentrations of TN,TP and NH₄⁺-N are 7.68mg/l,0.64mg/l and0.78mg/l respectively.Compared with the traditional process,the removal rates were increased by 8.4%,6%and 7%respectively,and the ability to treat unstable water quality and high load water quality was enhanced.In this study,the improvement test of AAO process was carried out using an integrated device,and significant optimization results were obtained.The optimal operating parameters and operating modes obtained by the study have strong reference significance for single-family or small-scale（daily treatment capacity of 20～50 m³）AAO facilities to treat rural domestic sewage in Zhongwei City.However,whether it is suitable for large-scale facilities（with a daily treatment capacity of more than 100 m³）or a sewage treatment plant has yet to be examined,and it needs to be adjusted according to the operation.