The main task of this design is to complete the sewage treatment plant design and calculation in accordance with the original data and information in the task book，and assign the plane layout, elevation layout based on the calculate date and relevant principal,as well as draw the corresponding plane,elevation map and profile map of sewage plant main structures.Moreover, economic accounting of sewage plant is also conducted in accordance with relevant estimation methods,and finally on environment,fire protection and occupational health and safety were evaluated.
The designed volume of waste water is 50000t/d,and the main characteristic of water is that the high nitrogen contention is quite high.Currently,there are several methods for sewage biological nitrogen removal process：the A/O,A/A/O method,the AB method,the SBR method，the oxidation ditch，all of them have their weakness and strength,The characteristic of urban sewage treatment technology and water requirements,taking into account the sewage treatment，and the need for effective removal of sewage nitrogen，phosphorus and organic matter,and considering the factors such as reducing operating costs，the design project using the A/O process,making water quality of urban sewage emission meet the requirement of GB18918-2002-B standard.
The design strictly follow the five basic principles: (1) Carefully study the basic data,a comprehensive analysis of various influencing factors, have a good command of  the water quality characteristics and geographical characteristics, a reasonable choice of design parameters so as to provide a reliable basis for engineering design. (2) Water quality characteristics of the advanced technology, stable operation, investment and processing costs and reasonable treatment process, active and prudent use of the proven effective new technologies, new processes, new materials and new equipment, advanced processing technology. reliable, stable treated water quality discharge standards. (3) Try to avoid or reduce the negative impact on the environment, properly disposal of gate slag, sludge and odor which are formed in leachate works , to avoid secondary pollution to the environment. (4) The reasonable layout of building structures, the automatic control of the process, and strive to secure, reliable, affordable, improve the management level to facilitate and reduce the intensity of labor and operating costs. (5) Strictly enforce the relevant provisions of the State Environmental Protection, the treated water discharge standards.
This paper analyzes the nitrogen pollutants in the sewage generated links, pollutants and major sources of pollution, and from lack of oxygen, the good kind of biological treatment to consider the wastewater treatment process, the A / O process,which can lower wastewater pollutant index such as BOD from 100 mg / L to 20 mg / L ，SS dropped from 40 mg / L to 15mg / L or less, NH3-N dropped from 30 mg / L to 8 mg / L or less water to meet the standards,
    The main flow of the sewage treatment plant process: advanced sewage water grille, backward pumping station and the fine grid to stop the interception of sewage in suspension or floating state chunk solids removed by the grit chamber diameter particles the larger particles into the secondary treatment, ie, the A/O pool, and then by the final settling tank sedimentation and disinfection of pool water; the secondary settling tank sludge back to the anoxic tank, and finally the sludge treatment. The process is as follows:
    The primary sedimentation tank in the nitrogen-containing wastewater → Grid → Sewage lifting pumping station → Adjust the grit chamber of the pool → Grit chamber→The primary sedimentation tank→ A/O tank →Secondary sedimentation tank → Contact tank pool disinfection → Measurement weir → Discharge water
AO process characteristics denitrification alkalinity added nitrification needs, you can add about 50% of the alkalinity of the nitration reaction can take advantage of the organic carbon in the sewage, and denitrifying bacteria in the carbon utilization is more extensive, including the degradation is more difficult degradationorganic matter. The process is a compact structure, flexible operation control shock load, the small amount of sludge characteristics, practice shows that the combined process of reliable performance, less investment, simple operation and management which provides a feasible way for high concentrations of nitrogenous wastewater treatment with good economic, environmental and social benefits. 日处理50000吨生活污水脱氮除磷设计(2):http://www.751com.cn/huaxue/lunwen_8232.html