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设计总说明：生活污水即人们在日常生活中用过的水。污水中所含的大量有机物，是污水处理过程中的主要对象。本次设计为城市污水处理工艺设计，设计程度为初步设计，针对城市污水的水质水量等特点，设计一套合理可行的方案。本次设计处理水量为20000m3/d，原污水的各项指标为：BOD5=210mg/L，COD=440 mg/L，SS=250 mg/L，TN=55 mg/L，NH3-N=38 mg/L，PH=6~9。要求出水水质达到中华人民共和国国家标准《城镇污水处理厂污染物排放标准》（GB18918-2002）二级标准，即BOD5≤20mg/L，COD≤100mg/L，SS≤20mg/L，TN≤55 mg/L，NH3-N≤15mg/L，PH=6-9。37170
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本次设计采用的是A2/O工艺，工艺流程为：污水—格栅—污水提升泵房—调节池—沉砂池—初沉池—A2/O反应池—二沉池—清水池—消毒池—出水
污水先经过粗格栅去除污水中较粗大漂浮物和悬浮物，再经过污水提升泵房进入细格栅后进入调节池。在调节池内进行水质水量的调节。从调节池出来的污水进入到沉砂池，在沉砂池中去除污水中的泥沙等相对密度较大的无机颗粒后再进入到初沉池，初沉池的主要去除对象是SS和BOD5。污水由初沉池进入A2/O反应池进行脱氮除磷后流入二沉池，之后依次进入清水池、消毒池后达标出水。来自沉淀池、A2/O生化反应池的剩余污泥通过污泥提升泵房，进入到污泥浓缩池内被浓缩，浓缩后进入到污泥脱水机房，进一步对污泥进行脱水。污泥脱水后形成泥饼，并装车外运。
该工艺方案通过厌氧段丝状菌的抑制，使活性污泥膨胀得到了有效控制。同时能够把厌氧、缺氧及好氧这三者有机结合起来，使该工艺能够同时做到去除N、P、BOD5及COD的功能。该工艺还具有运行操作灵活，抗冲击负荷好，污水处理效果好。通过实践表明该工艺处理性能可靠，同时还具有良好的社会效益、经济效益和环境效益。
毕业论文关键词： 城市污水；污水处理；A2/O工艺
Process design of city sewage treatment
The water we use in our daily life, called sewage. This kind of water contains a lot of pathogens and organic matter, it must be treated before its emissions.Sewage contains a large amount of organic matter,which is the main object in the process of sewage treatment.The design is for the urban sewage treatment process design, in view of the characteristics of urban sewage in the water, design a set of feasible scheme, design degree for preliminary design. The treatment capacity of the design is 20000m3/d,Each index of raw sewage is: BOD5=210mg/L，COD=440 mg/L，SS=250 mg/L，TN=55 mg/L，NH3-N=38 mg/L，PH=6~9.
This design uses A2 / O process,the process flowsis: sewage- barriers-sewage pump room- regulating reservoir-grit chamber- primary settling tank-A2/O reaction tank-secondarysettling tank- clean water tank- disinfecting tank- effluent.
Sewage after coarse screen first relatively bulky floater and suspended solids in wastewater，after sewage pump into fine screen again into the regulating pool. In the regulation of adjusting the water quality in the pool water, the PH is between 6 ~ 9 in the pool. Out of adjusting pool, sewage flow into the grit chamber, remove the sediment and other relative density is larger in the sewage of inorganic particles into the pond, main removal at the beginning of the object is a BOD5 and SS. Sewage early access to the A2/O reaction pool for nitrogen and phosphorus, and then flow into the second pond, after standard in turn into the pool of clear water reservoirs and sterilization pool. From the surplus sludge sedimentation tank, A2/O reaction pool after the sludge pump is concentrated into the sludge concentration pool, enrichment in sludge dewatering room, after further for dewatering sludge.
The process scheme through the inhibition of anaerobic period of filamentous fungi, gives active sludge bulking control effectively; The anaerobic, anoxic and aerobic organic combination, at the same time to remove the function of N, P, BOD5 and COD.At the same time, this process also has flexible operation, good resistance to impact load, gentrification and phosphorus removal effect is good, generally applicable to the requirements of nitrification and phosphorus removal characteristics of large and medium-sized city sewage plant. Practice shows that the process performance is reliable, but also has a good economic benefit, environmental benefit and social benefit.