Unit9

Sedimentation

—p59新浪微博：南昌工程學(xué)院臾涼先森Newwordsandexpressionspotableadj.可飲用的，potablewaterClarificationn.澄清，凈化clarifiern.澄清池，澄清器開(kāi).apparatusn.器械,設(shè)備,儀器prechlorinationn.預(yù)氯化inlet

n.進(jìn)口turbulent

adj.紊流的，湍流的Turbulencen.紊流，紊亂perimeter

n.周長(zhǎng)圓周weir

n.堰，溢流堰layoutn.規(guī)劃,設(shè)計(jì),(書(shū)刊等)編排,版面,(工廠(chǎng)的)布局圖rectangularadj.矩形的，成直角的2新浪微博：南昌工程學(xué)院臾涼先森NewwordsandexpressionsInclinedtuben.斜管effluentadj.流出的n.流出物,出水Sphericaln.球形的球的depositn.沉淀物堆積物；儲(chǔ)蓄存款Reinforcedconcreten.鋼筋混凝土controversial

n.爭(zhēng)論的爭(zhēng)議的Innovationn.改革創(chuàng)新inclinationadj.傾斜,彎曲,傾度,傾向,愛(ài)好hexagonaladj.六角形的六邊形的backwashn.v.反洗反沖洗modulen.模數(shù)，模塊，組件3新浪微博：南昌工程學(xué)院臾涼先森Sedimentationorclarificationistheremovalofparticulatematter,chemicalfloc,andprecipitatesfromsuspensionthroughgravitysettling.沉淀和澄清是從懸浮物中通過(guò)重力沉降去除顆粒物、化學(xué)絮凝產(chǎn)物和凝結(jié)沉淀物。Thismakeswaterclarificationavitallyimportantstepinthetreatmentofsurfacewatersforpotablesupplyandinmostcasesthemainfactorindeterminingtheoverallcostoftreatment.這使得水的澄清是飲用水供應(yīng)中地表水處理的至關(guān)重要一步，在很多情況下，它也是決定全部水處理費(fèi)用中主要的因素。Poordesignofthesedimentationbasinwillresultinreducedtreatmentefficiencythatmaysubsequentlyupsetotheroperations.糟糕的沉淀池設(shè)計(jì)將會(huì)導(dǎo)致降低處理效率，接下來(lái)這也許會(huì)影響到其它（水處理工藝）的運(yùn)行。4新浪微博：南昌工程學(xué)院臾涼先森Surfacewatercontaininghighturbiditymayrequiresedimentationpriortochemicaltreatment.地表水（包含）在高濁度下就要求在化學(xué)處理工藝之前沉淀。Presedimentationbasinsareconstructedinexcavatedgroundoroutofsteelorconcrete.預(yù)沉淀池建在被挖坑的地下或用鋼筋混凝土建造。Steelandconcretetanksareoftenequippedwithacontinuousmechanicalsludgeremovalapparatus.鋼筋混凝土池通常裝配有持續(xù)的機(jī)械除泥設(shè)施。5新浪微博：南昌工程學(xué)院臾涼先森Theminimumrecommendeddetentiontimeforpresedimentationis3h,althoughatmanytimesoftheyear,thismaynotbeadequatetoremovefinesuspensions.在預(yù)沉池，（被建議）規(guī)定的最短停留時(shí)間是3小時(shí)，盡管在一年的很多時(shí)候，這個(gè)時(shí)間可能不足夠去去除細(xì)小懸浮物質(zhì)。Chemicalfeedequipmentmaybeprovidedaheadofpresedimentationtoprovideprechlorinationorpartialcoagulationforperiodswhenwateristooturbidtoclarifybyplainsedimentation.當(dāng)通過(guò)平流池水太渾濁而不能澄清時(shí)，化學(xué)藥劑投加裝置就需要設(shè)置在預(yù)沉池之前去預(yù)加氯或者添加部分的混凝劑。6新浪微博：南昌工程學(xué)院臾涼先森Settlingbasinsareusuallyprovidedforchemicalcoagulationorsoftening.沉淀池通常投加一些混凝劑和軟化藥劑。Thesebasinsmaybeconstructedofconcreteorsteelinawidevarietyofshapesandflowmechanisms.這些池子用鋼筋混凝土建成各種各樣的形狀和流動(dòng)機(jī)制。Tominimizetheeffectsofshort-circuitingandturbulentflow,careistakenintheeffectivehydraulicdesignofinletandoutletstructuresinalltanks.精心的考慮到所有池子進(jìn)出口結(jié)構(gòu)的水力設(shè)計(jì)，去最小化短流與紊流的影響。7新浪微博：南昌工程學(xué)院臾涼先森Inletstructuresareexpectedto:(1)uniformlydistributeflowoverthecrosssectionofthesettlingzone;(2)initiateparallelorradialflow;(3)minimizelarge-scaleturbulence;and(4)precludeexcessivevelocitiesnearthesludgezone.進(jìn)口結(jié)構(gòu)考慮部分包括以下幾點(diǎn)：（1）一致地（均勻地）分配到沉淀區(qū)域的各個(gè)部分（2）發(fā)起平行或輻射狀的流動(dòng)（3）最小化產(chǎn)生大規(guī)模紊流（4）阻止靠近污泥的區(qū)域有過(guò)大的流速Flowthroughasedimentationbasinentersatthetopofthebasin.水流流經(jīng)沉淀池到達(dá)池子的頂部Insomecircularbasins,theflowmayenteracentralflocculatingchamberofthebasin,effluentflowsverticallyoutoverperimeterweirs.在一些圓形的池子，水流將會(huì)流進(jìn)池子中央的絮凝室，出流水流從周?chē)膰叽怪绷鞒觥?新浪微博：南昌工程學(xué)院臾涼先森Inrectangulartankswaterflowshorizontallytoanendweirfordischarge.在矩形的水池，水流水平地流向池子終點(diǎn)的出水堰。Anefficientlydesignedverticaltankismorestablethanahorizontalone.Theratingofaverticaltankasrelatedtothebulksettlingvelocityisusually3.3to9.8ft/h(1to3m/h).有效設(shè)計(jì)的豎流式沉淀池比平流池運(yùn)行穩(wěn)定。豎流式沉淀池的速率與較大絮凝體的沉速有關(guān)，通常為3.3到9.8英尺/小時(shí)（1到3米/小時(shí)）9新浪微博：南昌工程學(xué)院臾涼先森Recentdevelopmentshavebeenmadewiththeimplementationoftubesettlinginthedesignofhorizontal-flowsettlingtanks,whicharesaidtoovercomesomeofthepreviousdifficultiesandenablehigherratesofsedimentation.近期在平流沉淀池設(shè)計(jì)中，通過(guò)沉淀管的安裝取得了一些進(jìn)步，據(jù)說(shuō)這些進(jìn)步克服了先前的困難和提高了沉淀效率。Upflowsolidscontactclarifiers,andhorizontal-flowbasinsmayincreasetheirvolumetriccapacity50to150percentormorewiththeintroductionofinclinedtubesintotheirbasins.向上流的固體接觸到澄清池和平流式沉淀池會(huì)增加50%—150%的處理能力，或者通過(guò)采用斜管沉淀池可以增加更多的處理能力。Similarorimprovedeffluentqualityisobservedinthesemodifiedprocesses.類(lèi)似的或改善的出水水質(zhì)在這些改進(jìn)的工藝中被研究觀(guān)察。10新浪微博：南昌工程學(xué)院臾涼先森Effluentqualityforanysedimentationprocessisdependentuponpreviouswaterquality,coagulantsadded,mixing,flocculation,andfiltration.一些沉淀工藝的出流水質(zhì)取決于進(jìn)水水質(zhì)、混凝劑的投加、混合、絮凝和過(guò)濾。Withtheexceptionofpresedimentation,sedimentationprocessesareusuallyprecededbycoagulationandfollowedbyfiltration.除了預(yù)沉淀工藝，沉淀工藝通常先于混凝后于過(guò)濾。Therefore,typicalremovalsofregulatedcontaminantsbysedimentationandfiltrationarereportedaccordingtocoagulantsusedinconjunctionwiththeseprocessesforremovalofaspecificcontaminant.因此，通過(guò)沉淀和過(guò)濾工藝來(lái)去除典型污染物的去除率，是按照使用在這些工藝中去除特定污染物的混凝劑來(lái)確定的。11新浪微博：南昌工程學(xué)院臾涼先森Basically,thetheoryofsedimentationisthetheoryoftheeffectofgravityonparticlessuspendedinaliquidoflesserdensity.從根本上說(shuō)，沉淀理論是顆粒物懸浮在比其密度更低的液體中，利用重力的作用沉淀。Undertheinfluenceofgravity,anyparticlehavingadensitygreaterthan1.0willsettleinwateratanacceleratingvelocityuntiltheresistanceoftheliquidequalstheeffectiveweightoftheparticle.在重力的影響下，任何密度大于水的顆粒物將會(huì)以加速度在水中沉降，直到液體對(duì)顆粒物的阻力等于其自身重力時(shí)，（加速度才變?yōu)榱悖?。Thereafter,thesettlingvelocitywillbeessentiallyconstantandwilldependuponthesize,shape,anddensityoftheparticle,aswellasthedensityandviscosityofthewater.此后，顆粒物的沉速本質(zhì)上將不會(huì)改變和其沉速取決于它的大小、形狀和密度，同樣取決于水的密度和粘滯性。12新浪微博：南昌工程學(xué)院臾涼先森Formosttheoreticalandpracticalcomputationsofsettlingvelocitiesinsedimentationbasins,theshapeoftheparticlesisassumedtobespherical.在沉淀池中大部分沉速的理論和實(shí)踐計(jì)算，是假定顆粒物的形狀為球形（得出的）。Settlingvelocitiesofparticlesofothershapescanbeanalyzedinrelationtospheres.其他形狀的顆粒物的沉速可以通過(guò)與球形的聯(lián)系來(lái)推斷分析。Paragraphfive:4-513新浪微博：南昌工程學(xué)院臾涼先森NumberofBasins

Probablythemostimportantconsiderationsintheselectionofthenumberofsedimentationbasinsare:(1)theeffectupontheproductionofwaterifonebasinisremovedfromservice;and(2)thelargestsizewhichcanbeexpectedtoproducesatisfactoryresults.選擇沉淀池?cái)?shù)量最重要的因素可能是：（1）假如一個(gè)池子不能工作對(duì)產(chǎn)水的影響（2）供應(yīng)得到滿(mǎn)足的結(jié)果需要的最大尺寸14新浪微博：南昌工程學(xué)院臾涼先森Plantlayoutandsiteconditionsalsomayinfluencethenumberofbasins.水廠(chǎng)的設(shè)計(jì)和地理位置條件也會(huì)影響池子的數(shù)量。Foranysupplywhichrequirescoagulationandfiltrationfortheproductionofsafewater,aminimumoftwobasinsshouldbeprovided.對(duì)于任何安全水的生產(chǎn)供應(yīng)，要求