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ResearchontheExpansionProjectoftheMunicipalSewageTreatmentPlant---ThesampleofXi’anfourthsewagetreatmentplantADissertationSubmittedfortheDegreeofMasterCandidate：LiShengSupervisor：Prof.GaoJunfaChang’anUniversity,Xi’an,Chinai摘要西安第四污水处理厂（简称四污）一期工程设计处理能力为25万m3/d，自2008年11月投运以来，来水量在逐步增加，同时，草滩生态园区污水管网的逐步完善，近期将有3万m3/d（远期达22万m3/d）的污水通过已建成的草滩提升泵站排入第四污水处理厂，已经超出该厂处理能力，同时，四污出水排入漕运明渠，该渠道最终进入渭河，根据陕西省渭河三年治理规划，四污应该承担更重的处理任务，故尽快实施第四污水处理厂扩建工程是非常必要的。该工程拟采用和一期一样的工艺,主要构筑物包含粗细格栅，曝气沉砂池，初沉池，生物反应池(倒置A2O)，终沉池，接触消毒池等水工构筑物，污泥处置拟采用重力浓缩+中温消化+机械脱水方式进行处理，最终泥饼外运填埋。另外污水是一种稳定可靠的、可再生利用的水资源，污水回用是解决城市缺水的一条重要途径，污水经深度处理后可回用于工矿企业、市政环卫、园林绿化以及城市河道景观等方面。合理开发和利用城市污水资源，体现了水的“优质优用，低质低用”和“开源节流并重、节流优先、治污为本、科学开源、经济利用”的原则。所以，在第四污水处理厂扩建的同时、统一规划和建设中水回用系统是非常必要的。为选择合适的工艺方案通过对来水水质、水量的分析，并对一期污水处理运行的情况进行了分析，而且对现有的几个传统成熟工艺进行了比选，从中选择最佳的适合四污以后运行的方案。同时为以后提标改造和中水回用也预留了很大的空间。关键词：扩建必要性倒置A2O脱氮除磷最终沉淀中水回用加氯消毒污泥消化机械脱水iiAbstractThedesignprocessingcapacityofXi’anfourthsewagetreatmentplantinfirstphaseis250000m3/d,butthequantityofinfluentincreasegraduallysincetheplanthadbeenputintooperationinNovember2008.Atthesametime,sewagepipenetworkofCaotanecologicaldistrictisimproved,recently30000m3/d(220000m3/dinthefuture)ofsewagewillbeendischargedintotheXi’anfourthsewagetreatmentplantthroughthepumpingstation,andthetotalquantityofinfluentwillbebeyondthecapacityoftheplant.Futhermore,theeffluentofplantisdrainedCaoyunopenchannel,theneventuallyflowintotheWeiheriver.AccordingtothethreeyearscontrolplanofShaanxiWeihe,andXi’anfourthsewagetreatmentplantshouldbeheldmoreheavyprocessingtasks,therefore,theexpansionprojectofXi’anfourthsewagetreatmentplantassoonaspossibleisverynecessary.Thisprojectisusedthesameprocess(invertedA2O)asthatinthefirstphase,andthemainstructurescontainthickandfinegird,aeratedgritchamber,primarysettlingtank,biologicalreactiontank,secondarysedimentationtank,contactingdisinfectiontank,sludgedisposalisusedthemethodsofgravityconcentration+mesophilicdigestion+mechanicaldewatering,andfinallythecakewaslandfill.Moreover,sewageisastableandreliablerenewablewaterresource,sewagereuseisanimportantwayofwatertosolvethewatershortageincities,deeptreatmentofsewagecanbeusedinindustrialenterprises,municipalsanitation,landscapeandurbanriverlandscape,etc.Thereasonableexploitationandutilizationofsewageresourcesreflectedtheprincipletheoptimaluseofthehighqualityandlowqualitywaterandscientific,economicuseofthewaterresource.So,planningandconstructionofthereusesystemisverynecessaryduringtheplantexpansion.Tochoosethesuitableprocess,thequalityandquantityofinfluentismeasured,andtheplantoperationinthefirstphaseareanalyzed.Atlastbestsuitableplantwasdeterminedthroughcomparisonofseveralexistingtraditionalmatureprocess.Atthesametime,theplanreservedalotofspaceforreconstructionandsewagereuse.Keywords:expansionnecessity,invertedA2O,nitrogenandphosphorusremoval,secondarysedimentationtank,reclaimedwaterreuse,chlorinedisinfection,mechanicaldewateringiii目录第一章绪论.....................................................................................................................-1-1.1我国水资源及城市污水处理厂建设概况...................................................................-1-1.2西安市污水处理情况概述...........................................................................................-2-1.3西安市第四污水处理厂扩建工程概述......................................................................-2-1.3.1项目的必要性.......................................................................................................-2-1.3.2四污服务范围内排水现状...................................................................................-3-1.3.3四污一期处理现状...............................................................................................-4-1.4本文研究内容与目的..................................................................................................-6-第二章预测污水量及处理规模.......................................................................................-7-2.1污水进出水水量水质预测..........................................................................................-7-2.1.1预计工程设计规模...............................................................................................-7-2.1.2水质测定方法.......................................................................................................-7-2.1.3进水水质确定.......................................................................................................-8-2.1.4出水水质确定.......................................................................................................-8-2.1.5回用水用水量预测...............................................................................................-8-2.1.6回用水水质确定...................................................................................................-9-2.2污水处理工艺方案选择指导思想...............................................................................-9-2.3工艺总体分析............................................................................................................-10-2.3.1BOD5/CODcr比值..............................................................................................-11-2.3.2BOD5／TN（即C/N）比