The design of a urban sewage emissions of 10000 tons/day.
  Due to the design requirements and the concept of innovation ideas, and high nitrogen of the sewage ，high BOD5 and SS content ，nitrogen treatment , so i decide to us the mature sewage process - A20 process . A20 process can adapt to the different environmental conditions, different microbial community organic coordination function。combined with anaerobic, anoxic and aerobic condition , non-biodegradable organic  may break or open, the N, P and organic carbon can be removed at the same time ，as a result，we can  improve the removal efficiency of non-biodegradable organic compounds.
   T-oxidize ditch and unoxidize pool are two important part and water flows into three ditchs in turn, also T-oxidize ditch plays the role of secondary settling. The unoxidize pond release phosphorus. Along with aeration distance,  the dissolved oxygen density reduces. This make oxidize area and unoxdize area present in ture. Namely appears the nitration and the counter- nitration process in succession , get the result of denitrogenation. At the same time the fine oxygen district absorbs the phosphorus, get the result of getting rid of phosphorus.
  The process of the sewage is that: The sewage runs from pump house to sand sinking pond, to the pond of sedimentation tank, to disinfection pond, then  calculation trough ,finally the sewage lets out. The process of the sludge is that: Surplus sludge from the sedimentation tank enters concentration pond, enters digestion pond , hen enters automatically translated text:, at last the sludage will be carried out from the plant。  The main structure of this process include pump house，sand sinking pond,pond of sedimentation tank，disinfectio
n pond
Besides A2O process own a simple technological process, high efficiency, reasonable energy saving, which can effectively inhibit characteristics of filamentous bacteria, improve the sludge sedimentation performance 。Thus it can lead to excellent water quality. i adopted A2O process as the main process, the process is relatively simple,have mature technology, stable sewage processing, easy to control, which meet the design requirements, truly satify the comprehensive utilization of wastewater demand.
This design has a reasonable process. Investment costs is 1381.7 million yuan, sewage treatment costs is 0.79 yuan per ton. The reduction in the amount of COD: 14,016 tons, the reduction in the amount of BOD: 8322 tons. The  design process can effectively save the project investment, reduce processing costs, efficient use  floor space, and have other advantages to ensure stable operation of wastewater treatment.
Key words: A2O; Nitrogen and phosphorus; Design specification
 1    绪论
1.1    背景介绍
       城市污水的组成及危害，城镇污水是排入城镇排水系统中各类废水的总称，一般指生活污水、生产污水以及其他排入城镇排水系统中的污水还包含城镇雨水, 初期雨水就内含在半分流制排水系统中。生活污水包含城市生活中使用的各种洗涤剂和污水、垃圾、粪便等，多数为无毒的无机盐类，生活污水中主要化学元素为氮、磷、硫,水质稳定但混浊，颜色深，气恶臭,呈微碱性,一般不含有毒物质,但含有大量的致病细菌和寄生虫卵是生活水质特征。在生活污水中, 总质量的0.1%~0.2%是固体物质, ,污水中悬浮固体占1/3~2/5，主要溶解性固体(主要是各种无机盐和可溶性的有机物质)约占3/5~2/3.在生活污史中,所含固体物质约占总质量的0.1%~0.2%,其中溶解性固体(主要是各种无机盐和可溶性的有机物质)约占3/5~2/3,悬浮固体占1/3~2/5,此外,生活污水中还有氮磷等物质.水中含有的污染物是城镇污水对环境和人体健康造成有危害性的根源.城镇污水中的污染物质大致可以分为无机有毒物和有机有毒物，有机有毒物：重金属、砷、氰化物、氟化物等；无机有毒物：苯酚、多环芳烃、PCB 、有机氯农药等 每天30万立米污水处理厂生物处理工艺设计+CAD图纸(2):http://www.751com.cn/huaxue/lunwen_25666.html