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关键词：小城镇污水处理，SBR法处理，高程布置，平面布置。
A small town sewage treatment process design
General description of the design:With the rapid development of China's economic construction, urban construction and small towns around the accelerating pace of construction, appearance of the city has shown a rapid changed dramatically. Meanwhile, we also note that the rapid development of urban construction today, as an important part of urban infrastructure for water treatment systems, construction is lagging behind, there is a water treatment system, such as planning and inadequate waste of water resources, water reuse rate low, drainage network obsolete and other issues. Therefore, to speed up the process of building a sewage treatment plant.
The topics to be covered I designed a small town sewage treatment process design. Design flow 40000m3 / d, the overall design requirements: water quality is，CODcr：≤320mg/L, BOD5：≤180mg/L，SS：≤310mg/L, NH3–N≤35 mg/L，TN≤50 mg/L，TP≤3.0 mg/L. Effluent quality requirements：COD≤100mg L-, BOD≤30mg L-, SS≤30mg L-, NH3-N≤25mg L-,TN≤20mg L-,TP≤2.0mg L-。
Sewage treatment process consists of activated sludge and biofilm French. Activated sludge includes, hypoxia - aerobic denitrification (A / O method), oxidation ditch process adsorption biodegradation processes (AB France) batch activated sludge process (SBR method), the traditional plug-flow aerobic activated sludge process.
Through access to information, compare various aspects of the five kinds of activated sludge process characteristics, including: project investment, operating costs, organic matter and ammonia removal, management systems and automation level, sludge production and covers, etc., integrated several more specific characteristics of the process, combined with the actual situation of small towns, from the operational costs, the removal rate and the level of automation and other aspects into account, choose the SBR batch activated sludge method is most suitable for the urban processes.
Conventional activated sludge process is a continuous operation mode, while intermittent operation mode activated sludge process is intermittent. This process eliminates the need for secondary sedimentation tank and regulator tank, aeration tank volume is less than continuous, infrastructure costs and lower operating costs, but can also denitrification and phosphorus removal, without the need for sludge return.
Batch activated sludge process, by the water, aerating, sedimentation, water, idle five phases, called a run cycle. Aeration reaction stage, the control aeration tanks in the anaerobic and anoxic state, to achieve denitrification and phosphorus removal purposes. Precipitation stage equivalent to conventional activated sludge secondary sedimentation tank, and the method is carried out in a completely stationary state precipitation, so settling effect, the supernatant was discharged basic non-Daini masonry complete separation improved sewage mud activity.
Grille is a set of parallel metal trash rack or screen composition to retain rainwater, sewage and industrial effluent suspended solids or larger floating debris, from water purification to protect the role of the pump, but also reduce the subsequent processing structures the processing load, so that in the normal operation. Rotating selection of LXG chain grate discharge machine back rake. Advection rectangular grit chamber is a common form, with a simple structure, and good effect. The disadvantage is that 15% of the grit containing organic matter, the grit for subsequent processing difficult. Selection PGR-BGT2P advection grit equipment. Aerated grit chamber on one side of the body in the pool air into the sewage pond along the forward rotation, resulting in a vertical transverse circulation with the mainstream. Its advantages: By adjusting the amount of aeration, sewage swirl velocity can be controlled, so that the effect Desanding more stable; less affected by flow changes; also the role of the sewage from the pre-aeration and grit chamber overcome advection shortcomings. SBR process operating conditions of the main features is the intermittent operation, which is based on the timing condition to run, the operation process is pided into five phases: water, reaction, sedimentation, drainage and idle. Aeration system uses aeration, select one of the mesh pore air diffuser. Then set UV disinfection pool of effluent disinfection, ultraviolet disinfection equipment using UV3000PLUS ultraviolet disinfection equipment. Apart from the secondary sedimentation tank effluent, as well as sludge, sewage sludge enriched pollutants in addition to containing ash and large amounts of water (95% to 99%), but also contains a lot of organic matter, pathogenic microorganisms, bacteria, parasites eggs, volatile substances, heavy metals, salts, a plant nutrient (nitrogen, phosphorus, potassium) and so on. Its bulky, and easy to corrupt stink. So to be treated and disposed of, in order to prevent secondary pollution. Wastewater treatment plant located gravity thickened sludge concentration tank, so the concentrated sludge moisture content of 97% (before concentration is 99.2%). After making sludge dewatering, sludge cake Sinotrans.