Application And Efficiency Of A~2/O Nitrogen And Phosphorus Removal Process In Small Towns Sewage Treatment Plant

Sewage treatment is one of the urgent problem of modern urban economic and social sustainable development and indispensable component of small towns infrastructure construction.Since Reform and Opening up, China's economy developed rapidly, but it highlights serious of environmental problems, especially in small town's water pollution problems have become more intensified.In recent years, domestic and international community of common concern to the problem of water pollution of nitrogen, phosphorus and other nutrients cause eutrophication problems. Therefore, small town's sewage treatment plant of grade A about high nitrogen and phosphorus removal technology is one innovation of this paper.In order to solve small town's sewage treatment plant of grade A about high nitrogen and phosphorus removal problem,in this paper, we study the A~2/O and deformation process for a high level of phosphorus and nitrogen removal and comparative analysis of the effectiveness of small scale and pilot scale results based on Wu Qing Fourth Sewage Treatment Plant as the research platform, specifically includes:⑴Introduce characteristics, operating conditions, mechanism of biological nitrogen and phosphorus removal, influencing factors, new forms of A~2/O and deformation technology are introduced. The design and efficiency of high-efficient Nitrogen and Phosphorus Removal Process in Small Town Sewage Treatment Plant are specifically discussed. The test result shows that NPR process is effective in removing organic substance, nitrogen and phosphorus, when the BOD, COD, SS, NH 3-N, TN and TP removal efficiency reached 87.2%, 82.4%, 95.0%, 79.8%, 68.3%, 88.2% respectively in normal temperature. NPR process has certain advantages such as combination with the BAF and fill in the aerobic zone with high biological activity of packing make the effluent quality complies with Level A standard stipulated in the Discharge Standard of Pollutants for Municipal Wastewater (GB 18918-2002).⑵Two comparative conditions results show that compared with what can be achieved in normal temperature of NPR process, the COD, NH 3-N, TN and TP removal efficiency are respectively 10.3%, 12.3%, 13.2%, 21.7% lower in low temperature while no significant change of BOD and SS removal efficiency. Improvements and technical measures are proposed to improve low nitrogen and phosphorus removal for the current northern city sewage treatment plants in winter. Such as reducing the sludge load of the system and aeration in aerobic zone, increasing the sludge return ratio, extending the HRT of the system making the system of the COD, NH 3-N, TN and TP removal efficiency improved to some extent. It also can reduce power consumption and maximize the benefits of the sewage plant.⑶Lab scale and pilot scale studies of NPR process, Inverted A~2/O integrated oxidation ditch process and Bio-contact oxidation process with two new built-in suspension spherical packing based on three perspectives such as to further improve nitrogen removal rate, to lower investment and power consumption, to select low-temperature micro-organisms are made in this thesis. The result of orthogonal test are also used in the repeatability test and efficiency analysis. The results show that when filled the new built-in suspension of fiber bundle packing in NPR system aerobic zone and compared with continuous aeration, intermittent aeration improves removal rate of TN and TP as well; The system have obvious effects of simultaneous nitrification and denitrification and denitrifying removing phosphorus, thus it is economical and practical. The orthogonal test show that the ideal parameters are as follows: T: 20℃, DO: 2mg/L, water allocation ratio between the anoxic zone and the anaerobic zone:3:1, HRT:13.5hr.Under this condition, the BOD, COD, SS, NH 3-N, TN and TP removal efficiency reached 94.25%,89.59%,98.31%,95.90%,70.04% and 83.35% respectively of Inverted A~2 /O integrated oxidation ditch process, much better than NPR process. Compared with NPR process in normal temperature, Inverted A~2/O integrated oxidation ditch process annual totally saving costs 421000 yuan including electricity 378500 yuan, sludge disposal costs37000 yuan, maintenance of equipment 5500 yuan and so on.