Because of the rural Sewage volume is small, the quality and quantity of changes large at various times of the day. And more concentrated; especially the early, late in the cooking time, the amount of sewage reached the peak. It is out of the usually sewage emissions by 2 - 3 times. At the same time, rural residents living time consistency and the intermittent production of township enterprises make the water use variation coefficient is far greater than the value of city. In addition, water is often caused by a specific industry or drainage, many small towns contain a considerable amount of livestock wastewater. The drainage system is not perfect and without proper planning, when in the rainy season ,the rain and sewage mixed ,to make the variation of water large.
3.The collection of Sewage is difficult, the emission is also crude.
Due to historical reasons, most of the small towns in China is the lack of scientific planning. with the Complex terrain. Living in scattered, the road is narrow. The network is not complete, all kinds of land layout is not reasonable; the township sewage collection system is not perfect. In addition, because of the poor quality of the network construction , serious water leakage, cause a lot of water into the sewage pipe network in the rainy season. the areas of high ground water level usually into a lot of rain, resulting in large amount of sewage, make the sewage’s COD and BOD pollutant concentration is too low, greatly reduce the operational efficiency of the wastewater treatment facilities. Most properties of rural domestic sewage water is similar, usually does not contain heavy metals and toxic and harmful substances. BOD and COD are generally higher than the urban sewage, good biodegradability, B/C 0.45 ～ 0.55, nitrogen, high phosphorus content is the main character
In the synthesis of the actual weather, rural area of our country's geography, economic conditions, and characteristics of wastewater .finally , select the process of A/O combined with MBR to design the process of sewage treatment situation of villages and towns.
Nitrogen and phosphorus removal process in conventional biological (A/O process), there are sludge circulation between the anoxic and aerobic section.
The sludge by nitrifying bacteria, denitrifying bacteria, and other microorganisms, however, because of the best environment for the growth of various bacteria are different, there is a contradiction between them. but when make the MBR method combining with A/O method, makes this complex process has strong adaptability and resistance to shock loading. the removal of organic matter is more effective and at the same time can go for the good removal effect of nitrogen, combines the advantages of membrane separation technology and biological treatment technology, the effluent water quality is more better and suspended solids and turbidity is close to zero. Because of it provide a very favorable environment for the survival of long sludge age for nitrifying bacteria growth slow, then it can also effectively improve the nitrification effect, and make the treated water quality excellent, the operation is also simple, produce low sludge yield, covers an area of small features. The application scope and scale is continually expanding. Organics removal effect is better, and the nitrification and oxygen demand lower oxygen . At the same time, the membrane module settings play an important role for the stability of the water and improve the system capacity of resisting impact load. Sewage treatment is suitable for low carbon source.
Key Words: rural sewage treatment system ; A/O ; MBR ; characteristics of rural sewage
目 录
1.绪论
1.1设计任务 9
1.2设计背景 10
1.2.1原始条件10
1.2.2村镇污水水质特点11
1.2.3 设计要求 12 村镇污水处理工艺的研究与设计+CAD图纸(3):http://www.youerw.com/huaxue/lunwen_3759.html