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毕业论文关键词： 污水处理；A/A/O工艺；脱氮除磷
The Municipal Sewage Treatment Plant Process Design
The total description of design:With the continuous development of the social whole economy, people are also making increasingly strict requirements of sewage treatment. Sewage treatment has already become one of the most important factors that affect the development of economy. Considering my major and the practical of this project design,for the subject of graduation is 100000m3/d municipal sewage plant’s process design(Reference area in Shanghai),which margin of safety coefficient is 1.2. In view of the processing object is mainly for urban sewage,generally materials like BOD5 as the main object is removed.,to ensure that the nitrogen and phosphorus can be removed and effectively reduce the content of BOD5,SS in sewage, so the core of process for A/A/O technology seems appropriately. The inflow water The inflow water quality are as flows:BOD5:190mg/l,COD:380mg/L,SS:160mg/L,NH4-N：38mg/L,TP:2mg/L,TN:40mg/L. We could know that the the ratio of BOD5 and COD is 0.5,In accordance with the requirements, the discharge water quality are supposed to meet the grade A of”Discharge standard of pollutants for municipal sewage treatment plant”,namely:BOD5≤10
mg/L,SS≤10mg/L,COD≤50mg/L,NH4-N≤5mg/L,TP≤0.05mg/L,TN≤15,PH 6~9.The main task of graduation design is completing the processing structures design of the sewage treatment plant and hand in plane drawing、elevation drawing、and 6 inpidual structures drawings.
The sewage treatment plant process is as follows: first sewage through the bar screen and into the aerated grit chamber by sewage pump ascension and primary sedimentation tank in turns,then after the preliminary processing of sewage into the reaction tank,next the secondary sedimentation tank,entering the disinfection pool finally and water outflow.Among the process,the sludge of primary sedimentation tank into the sludge storage tank,part of the sludge from secondary sedimentation tank as returned sludge into the aeration tank and the excess activated sludge from the second sedimentation tank is discharged into the sludge thickener、sludge storage tank, Sludge dewatering room in turns by sludge pipeline,and finally sinotrans sludge disposal.
We set up one header pipe to receive the sewage from municipal without the inlet well,and the sewage directly through the inlet valve,floater or suspended matters intercepted by the grilling.The sewage treatment is consist of grilling,grit chamber,first sedimentation tank, and the pumping house is combined built with grilling.The type of pumping house is self-irrigation,and the grilling is mid-grill,which grill sapce is 20mm.The aerated grit chamber is separated into two parts,which making the larger inorganic particles sedimented by gravity.The main processing object of first sedimentation tank is suspended solids,and reduce the concentration of BOD5 in a certain extent at the same time.By comparison and analysis,the first sedimentation tank adopt two radial-flow sedimentation tanks,and the water quality index after treatment can be achieved as flows:BOD5≤152mg/L,COD≤323mg/L,SS≤114mg/L，TN≤15mg/L,TP≤1.8mg/L.The core of process we adopted is A/A/O technology,and the arrangement type is five corridors(first is anaerobic zone,second is anoxia zone,the rest of three corridors is aerobic zone),where sludge agitator and air aerator are set.The outflow water quality is as flows:COD≤60mg/L,BOD5≤20mg/L,SS≤20mg/L,TN≤20mg/L,TP≤1mg/L.Four secondary sedimentation tanks are also adial-flow,which adopted the centre-inflow and surrounding-outflow type,which not only make the solid-liquid separated from the mixture but also make sludge thickened.The sludge concentration of mixed liquor suppose 3000mg/L,and
sludge return ratio is 60%.To ensure the outflow water quality,contact disinfection pool using hypochlorous acid to disinfect,which using five corridors pushed fluid layout form.The treating Processes are like this way:raw sludge--sludge thickening--sludge adjustment--mechanical dewatering--final disposal.Considering actual engineering situation and economic benefit,we Are not ready to set the sludge digestion tank.After chemical adjustment and dewatering,which are final unify organized to transport outside the city.