| In recent years, issues of water pollution and eutrophication have become serious environmental problems waiting to solve in both developed regions and less developed areas along with the improvement of economic. For municipal wastewater treatment plant, the key to make the effluent satisfy the discharge standards is to realize the high efficiency removal of nitrogen and phosphorus. In China, most medium and large municipal sewage treatment plants usually take use of A/A/O process and its deformation as the primary means of wastewater biological treatment. However, the inherent defects of A/A/O process have hampered its treatment results and further promotion. The application of denitrifying phosphorus removal can make up for deficiencies of A/A/O process, achieving nitrogen and phosphorus removal by denitrification at the same time and saving carbon and energy source, which provides the basis for the upgrade of A/A/O process. So, It takes great significance to research A/A/O process for municipal sewage nitrogen and phosphorus removal by denitrification performance.In this thesis, we took the actual intake of a sewage treatment plant in Zhengzhou City as our study object, used A/A/O devices to achieve a continiuous flow of nitrogen and phosphorus removal by denitrification, investigated the main factors influencing the A/A/O process denitrifying phosphorus and nitrogen removal performace and explored the influent ratio of two-point water how to affect the removal effect of A/A/O process. Finally we can drew the following conclusion:(1) The system can obtain a relative stabe denitrificaiton biological nitrogen and phosphorus removal in treating municipal wastewater, realize the enrichment of the denitrifying phosphate by controling the appropriate parameters and achieve a good nitrogen and phosphorus removal effect. In the start-up period, the amount of phosphorus uptake in anoxic zone increased from 0 mg/L to 16 mg/L accounting for a larger proportion of the total P uptake, which meaned the realization of denitrificaiton of phosphorus in system.(2) The oxidation reduction potential (ORP) went though the after the first negative-positive process within the system and ORP value always varied from-100 to-300. The ORP value is usually negative in anaerobic zone and the smaller this value, the more conductive to anaerobic phosphorus release, while the ORP value is positive in aerobic zone. The exporation of ORP and pH changes'laws along with the whole system can provide both a reference for achieving automatic control of sewage treatment plants and a basis for realization of denitrification phosphorus and nitrogen removal.(3) The A/A/O process can obtain the best phosphorus and nitrogen removal effect with mixture reflux ratio of 200%, sludge reflux ratio of 100%, sludge age of 15d and the volume ratio between anaerobic zone and anoxic zone of 1:1, when the effluent TP, TN concentrations were respectively 0.28mg/L and 12.9mg/L. In addition, the removal rate of COD remained at about 90% and the effluent concentration kept at 20mg/L or so regardless of operating conditions.(3) COD removal percentage was respectively 83.2%,15.0% and 1.8% in anaerobic zone, anoxic zone and aerobic zone under the best operating conditions through accounting materials. TN removal percentage was 89.0%,8.2% and 2.8% in three reaction zones. The removal percentage of TP was 62.6% and 37.4% respectively in anoxic zone and aerobic zone. In the static experiment following, anoxic phosphorus uptake accounted for aerobic microbes microbial phosphorus ratio of about 0.52, indicating that anoxic phosphorus uptake system has been dominant microbial proliferation(4) Two-point influent ratio had less impact on COD removal and the COD removal efficiency had slight fuctuations with the increase of the influent ratio. While removal efficiencies of TN, NH4+-N and TP showed significantly higher trend as the water ratio increased. When the influent ratio was 3:7, removal efficiencies of TN, NH4+-N and TP were volatile indicating the system's instability and weak shock. The average removal rates of the three were respectively 70.3%,98% and 92.5% when the influent ratio was 7:3 and the concentration of pollutants can satisfy A standard of the national sewage disposal criterion.(5) Compared with the single-point influent pattern, the two-point water ratio of 7:3 had a more stable and higher average removal rate of TN and NH4+-N. However, the removal rates of TP and COD were slightly higher when the influent patter took use of the single-point measure. If the removal rate of TN was a little lower with a higher concentration of effluent and the removal of TP did not constitute a limiting factor we suggested that the two-point influent pattern was best choice.(6) In practice, municipal wastewater treatment plant in running process should focus on investigating of various factors how to affect on denitrifying phosphorus bacteria, and creating favorable conditions to boost the accumulation of denitrifying phosphate bacteria so that denitrifying phosphorus removing bacteria gave full play to its advantages and played the role of savings both carbon and energy.
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