ISPE预处理选项

1、PRETREATMENTOPTIONS预处理选项4. PRETREATMENTOPTIONS预处理选项4.1 INTRODUCTION简介Pretreatmentisallprocessstepsorunitoperationspriortothelast(final)watertreatmentstep.Pretreatmentisaseriesofunitoperationstomodifythefeedwaterqualitysothatitwillbeofadequatequalitytobefedtoafinaltreatmentstep.ThisfinalstepmaybeReve

2、rseOsmosis,Ultrafiltration,MultiorMixedBedDeionizationorDistillation.ThesefinalstepsarediscussedinChapters5and6.预处理是指最后(最终)水处理步骤之前的所有加工步骤或单元操作。预处理是一系列的单元操作，用来改善给水水质以使其水质足够好而进入终处理步骤。最终步骤可以是反渗透、超滤、多或混合床去离子或蒸储。第5、6章中将详细讨论这些最终步骤。ReverseOsmosisisuniquesinceitcanbeapretreatmentstep,inadditiontobeingafinal

3、treatmentstep.ReverseOsmosisapplicationsinpretreatmentarediscussedinthischapterandChapter11,butReverseOsmosisasatechnologyisdiscussedinChapters5and6.反渗透很特别，因为它即可以是一个预处理步骤，另外还能是一个终处理步骤。本章和第11章将讨论反渗透作为预处理的情况，而将其作为一门技术的情况将在5、6章中详述。Theinitialsectionsofthischapterdiscusstheprocessdesign(programmingissues

4、)forpretreatmentdesignincludingfeedwaterqualityandoutputwaterqualityfrompretreatment.Thechapterthendiscussestheselectionoftreatmentoptions(i.e.unitoperations)forfourgroupsofimpurities:本章的开始部分讨论预处理设计的过程设计(程序设计问题)，包括给水水质和经过预处理后出来的水质。然后讨论针对四种杂质所做选择的处理选项(即单元操作)：?Controloffouling-removalofturbidityandpar

5、ticulates浑浊度和粒子的除垢控制?Controlofscaling-removalofhardnessandmetals硬度和金属的除氧化皮控制?Removaloforganicsandmicrobiologicalimpurities有机物和微生物杂质的去除?Removalofmicrobialcontrolagents微生物防治因子的去除Pre-treatmentoptionsaresummarizedinFigure4-1attheendofthechapter.本章结尾处的图4-1中总结了预处理的可选方案。Thefinalsectionsofthechapterdiscusst

6、heimportanceofanioncomposition/concentration,pH,materialsofconstruction,andpretreatmentsystemcontrol.本章的最后讨论了阳离子的构成/深度、pH、组成材料以及预处理系统控制的重要性。ThisdiscussionisbasedonthedescriptionofthesetechnologiespresentedinChapter11.这些讨论是建立在11章中出现的对这些技术的叙述基础之上的。4.2 PROCESSDESIGNOFPRETREATMENT预处理的过程设计Processdesignof

7、thepretreatmentsystemisthespecificationoftheunitoperationsorprocessstepstotreatthefeedwater.Typicalinformationincludesflowrates,temperatures,pressure,andcompositionofallstreams.DetailedmechanicaldesignoftheequipmentforagivenunitoperationorprocessstepisbeyondthescopeofthisGuide.预处理系统的过程设计是对处理给水的单元操作或

8、加工步骤的规范。典型信息包括流速、温度、压力以及所有水流的组合。为给出的单元操作或加工步骤的设备做详细的机械设计不在此指南范围内。Theprocessdesign(programmingissues)forapretreatmentsystemmayinclude:预处理系统的过程设计(程序设计问题)可能包括：a) Requiredquantityandqualityofthewaterfromthefinaltreatmentprocess.经过终处理程序出来的必须的水量和水质。b) Temperatureconstraintsonthewaterusedinapharmaceuticalp

9、rocessandtheapproachtomicrobialcontrol.对用于制药工艺的水温和防治微生物所需的温度限制。c) Thefinaltreatmentoptionthathasbeenchosen,asthisdefinestherequiredwaterqualityleavingpre-treatment.已经选定的终处理选项，这就规定了离开了预处理步骤所需达到的水质。d) Qualityofthefeedwaterthatistheinputtothepretreatmentsystem(waterqualitytobevalidatedoveraoneyearperio

10、d).预处理系统的给水水质(验证水质需要一年以上的期限)e) Differencebetweeninputwaterqualityanddesiredoutputwaterquality.Thedifferencedeterminesimpritiesthatmustberemovedbythepretreatmentsystem.Thedifferenceisdeterminedbyperformingamaterialbalance.Attentionshouldbepaidtoimpuritiesandminorcomponents.输入水水质和希望得到的输出水水质之间的差异。此差异确定

11、了必须要用预处理系统去除的杂质。此差异是通过执行一个物料平衡来决定的。应当特别注意杂质和较小的组分。f) Pretreatmentoptionstoprovidethedesiredremovalofimpuritiesconsideringotherfactorssuchascapabilitiesofthelaborforce,economics,wastedisposal,environmentalconsiderations,validation,andtheavailablespaceandutilities.鉴于劳动力、经济、废物处理、环境因素、验证以及或用的空间和设施之类的因素，

12、预处理选项要能理想地去除杂质。Inadditiontodefiningtheoptionsforremovalofimpurities,theapproachtakentomicrobialcontrolisanintegralpartoftheprocessdesignofthepretreatmentsystem.Considerationsinclude:除了规定去除杂质这一项以外，用于防治微生物的途径也是预处理系统过程设计需要整合的部分。考虑包括：a) Ifthedrinkingqualitywatertothepretreatmentsystemcomesfromamunicipal

13、ityintheUnitedStates,itwilltypicallycontainchlorine,orchloramines,asamicrobialcontrolagent.InEurope,ozoneisthemorecommonmicrobialcontrolagent.Theconcentrationoftheagentshouldbesufficienttoprotecttheinitialstepsofthepretreatment.如果预处理系统的饮用水是来源于美国市区，那么它都会含有用作微生物防治因子氯或氯胺。在欧洲，臭氧是最普遍的微生物防治因子。因子的浓度应当足够用来防

14、护预处理的最初步骤。b) Ifthequantityofmicrobialcontrolagentisinsufficient,additionalmicrobialcontrolagentmaybeaddedorprovisionmadetoperiodicallysanitizetheinitialequipmentinthepretreatmentsystem.Thisislikelyifwatercomesfromasourceotherthanamunicipality.Increasedmonitoringoffeedwaterandtheinitialstepsmaybewarr

15、anted.如果微生物防治因子的量不够，那么可以添加额外的微生物防治因子或者在预处理系统的首个设备进行定期消毒。如果水是来源于市政以外，这种情况是很有可能的。希望能够保证增加对给水和最初步骤的监控。c) Atsomepointinthepretreatmentprocess,themicrobialcontrolagentmustberemovedbeforegoingtothefinaltreatment.Atthispoint,ameansofeithercontinuousorperiodicsanitizationneedstobeselectedforthetreatmentstep

16、sfollowingthisremoval.在预处理过程的某些点上，进行终处理前必须去除微生物防治因子。在这种点上，必须为去除之后的步骤选择连续或定期消毒两种方式其中之一。TheUSPrequirementthatcompedialwatersshouldcontainnoaddedsubstancd"eliminatesadditionofchemicalsto"PurifiedWater"orWaterForInjection.However,additionofchemicalagentsisnotprohibitedinpretreatment.Subst

17、ancesarefrequentlyaddedinpretreatmentandsubsequentlyremovedinthepretreatmentorfinaltreatment.Someexamplesare:USP规定法定水应当含有“非添加物质”，这就排除了向“纯化水”或注射用水中添加化学物质的可能性。但是，在预见处理中并不禁止添加化学助剂。预处理时经常会加入一些物质，而它们又会在预处理或终处理中被去除。比如：?Chlorine(tocontrolmicrobialgrowth,removedinlaterstagesofpretreatment)氯(为了防治微生物生长，会在预处理的

18、最后阶段去除)?Sodiumions(insoftenerwithexchangeformultivalentions,removedinionremovalprocess）钠离子（在软化器中和多价离子进行交换，在去离子工序中被去除）?Acid（fordegasificationtoremovecarbondioxide,counterions,removedinasubsequentionremovalprocess）酸（为了脱除二氧化碳气、反离子，在随后的去离子工序中被去除）?Sulfite（toreducechlorinetochloride,orchloramihes,toammoni

19、umandchloridewhileformingsulfate,removalbysofteningorionremovalprocess）亚硫酸盐（在形成硫酸盐的同时将氯转化为氯化物，或者将氯胺转化为镂和氯化物，通过软化或去离子工序去除）?Sequestrants（topreventscalinginfinaltreatment,removedbyROinfinaltreatment）螯合剂（在终处理中防止结垢，通过终处理中的RO去除）?pHcontrolagents（removedinionremovalprocess）pH控制因子（在去离子工序中去除）Addedsubstancesar

20、eanissueiftheyresultinanincreaseinmicrobialgrowthorendotoxins.如果添加的物质导致微生增长或内毒素增加，那么它们就是一个问题。Afinalconsiderationistherelationshipbetweeninvestmentandoperatingdollarsinpretreatment,andtheperformanceandcostofthefinaltreatmentprocess.Thefollowingaregenerallytrue:最后需要考虑的是预处理的投资和开发费用与终处理工艺的性能和成本之间的关系。?Af

21、inaltreatmentsystemwillnotoperatereliablyoverthelongterm,withoutreliableoperationofthepretreatmentsystem.如果预处理系统操作性不可靠，那么终处理系统的长期操作也不会可靠。?Inadequateoperationinpretreatment（breakthroughofparticulates,hardness,orchlorine）maynotimmediatelyaffectwaterqualityfromfinaltreatment,butitwillbereflectedinlongt

22、ermmaintenanceandoperatingreliability,andpossiblyinwaterquality.预处理中操作不充分（有粒子、硬度或氯漏过）或能不会立即影响到终处理的水质，但是会反映在长期维护和操作可靠性上，也有可能是水质。?Investmentinpretreatmentcapabilityandreliabilitycanreturnmanytimestheinvestmentinfinaltreatmentmaintenancecosts.在预处理能力和可靠程度上的投资得到的回馈会是花费的终处理维护上的几倍。?Pharmaceuticalwatersyste

23、msareexpectedtogeneratewatermeetingfinalpharmaceuticalproductwaterstandards.Thesystemshouldbedesignedtocontrolimpurityspikesintheincomingwaterquality,orseasonalimpurityprofilechanges.Arobustpretreatmentsystemdesignhandlesimpurityspikesdetrimentaltofinaltreatment.我们期望制药用水系统生成的水能够达到最终药品的水质标准。设计系统时应当控制

24、给水水质中的杂质峰，或者杂质表现出的周期性变化。设计一个坚固耐用的预处理系统来处理那些终处理不易去除的杂质峰。Thereisnosingle"right"answertotheprocessdesignofthepretreatmentsystem.Pretreatmentsystemprocessdesignisaseriesofchoicesandoptions,eachwithadvantagesanddisadvantages.预处理系统的过程设计并没有唯一的“正确”答案。预处理系统的过程设计是一系统的选择，每个都有各自的利弊。4.3 FEEDWATERTOPRET

25、REATMENTQUALITY:TESTINGANDDOCUMENTATION预处理给水水质：测试和文件记录Compendialpharmaceuticalwatersystemsarerequiredtousefeedwatercomplyingwith"DrinkingWater"standards.法定的药用给水系统应当用符合“饮用水”标准的给水。Mostpharmaceuticalmanufacturersutilizemunicipalwatersupplies.Thiswatergenerallymeets"DrinkingWater"qua

26、litystandardsandistreatedwithamicrobialcontrolagent.HistoricallyintheUS,themicrobialcontrolagentischlorine,butchloramineisnowusedwithincreasingfrequency.Eitherfeedwatercompositionormicrobialcontrolagentconcentrationmaybesubjecttooccasionalandseasonalvariations.Thesevariationsmaynegativelyimpactwater

27、quality,andcanbedetectedonlybyextensivesampling.Inaddition,waterqualityattheplantsitemaynotbeequivalenttothatfromamunicipaltreatmentfacility,duetopotentialforcontaminationorlossofmicrobialcontrolagentinthedistributionsystem.Documentationoffeedwaterqualityisrecommendedeitherbyuseofmunicipalitytesting

28、(ifapplicable)supplementedbysometestingattheplantsideorbyextensivetestingoffeedwaterquality.大多数的药品制造商都是使用的市政供水。这个水一般都满足“饮用水”的质量标准，并用微生物防治因子处理过。在美国历史上，微生物防治因子是氯、但是现在使用氯胺的频率也在增加。给水成份或微生物防治因子的浓度都会受偶然因素或季节变化的影响。这种变化对水质会有不利影响，而且只有用扩大抽样才能检查出来。此外，在工厂里的水质也有可能和市政处理厂出来的不一样，这是因为在分配系统中微生物防治因子在污染或丢失的可能性。给水的水质文件推

29、荐用市政测试结果(如果适用的话)，再补充一些在工厂里所做的测试结果，也可以对给水水质做全面的测试。Typicalcontaminantsinfeedwaterinclude:给水中含有的典型成分有：?ParticulatesSilt,dust,pollen,pipescale,ironandsilica,undissolvedmineralsandorganics粒子泥沙、灰尘、花粉、管垢、铁和二氧化硅、不溶的矿物质和有机物?InorganicsCalciumandmagnesiumsalts,heavymetals(iron,aluminum,andsilica)withtheircorre

30、spondinganions无机物钙盐和镁盐、带有相应离子的重金属（铁、铝和硅）?OrganicsNATURALLYOCCURRINGBYPRODUCTSOFVEGETATIVEDECAY,I.E.,HUMICANDFULVICACIDSAND"MAN-MADEORGANICS"SUCHASPESTICIDESANDAUTOMOTIVEPOLLUTION（OILS）有机物自然存在的植物腐烂后的副产物，即腐殖酸和富里酸，以及“人造有机物”如杀虫剂和汽车污染物（油）?BacteriaBACTERIALCONTAMINATIONANDITSBYPRODUCTS,ENDOTOXIN

31、S,ANDPYROGENS细菌细菌污染及其副产物，内毒素和热原Testingrecommendationsinclude:推荐的测试包括：?Documentationthatfeedwatermeetsdrinkingwaterquality.Thismaybebasedonresultsoftestingbythemunicipality,possiblysupplementedbylocalorin-processtesting.Frequencyofin-processtestingwillbeaffectedbyreliabilityofthemunicipality,importan

32、ceofmonitoredvariables,andcompanyphilosophy.给水符合饮用水水质的文件。这可能是根据市政的测试结果，也有可能是由当地或过程中测试结果补充的。市政当局的可信度、监控变量的重要性以及公司的理念都会影响过程中测试的频率。?Monitoringformicrobialcontrolagentlevelsatthestartofthepretreatmentsystem.ChlorinelevelisaffectedbypH.Achlorinelevelof0.2-1.0ppmisgenerallyconsideredadequatetocontrolmicro

33、bialgrowthandgenerallyhasnegligibleeffectsonpretreatmentequipmentorperformance.在预处理系统初始处对微生物防治因子水平的监控。氯的水平会受到pH的影响。一般认为0.2-1.0ppm的氯完全能够防治微生物生长，而且它对预处理设备和性能的影响也可以忽略不计。?Specifictestingforcontaminantsknownorsuspectedofbeingpresentinthefeedwater.Thisistodetermineifdatafromthemunicipalityisadequate;e.g.,

34、feedwaterfromasurfacesourceforpesticidesinanagriculturalareawhererunofffromfarmsmaybeseasonal.存在于给水中的已知或可疑污染物的特效试验。这个试验取决于市政方面的数据是否充分；例如来源于地表的给水，因为从家业地区的农田中流出的杀虫剂可能是季节性的。QUALITYOF4.4 OUTPUTWATERFROMPRETREATMENT:FEEDWATERTOFINALTREATMENT预处理输出水：终处理的给水水质Thegoalsforpretreatmentaretoprovidewaterqualityth

35、atminimizestheoperatingandmaintenanceproblemsinthefinaltreatmentequipmentandtopermitthefinaltreatmentsteptoproducewatermeetingthedesiredspecificationsforfinaltreatment.预处理的目的是供水，所供的水质应当能够减少对终处理设备的操作和维护，并使终处理步骤生产出来的水符合终处理预期的要求。Theimpuritiesthatmustberemovedinthepretreatmentprocesstopermitreliableoper

36、ationofthefinaltreatmentstepdependonthefinaltreatmentstepselectedandthetoleranceofafinaltreatmentstepfortheimpurities.Ifpretreatmentisinadequate,resultingproblemscanbecomeverylargeinmagnitude,asseeninTable4-1below:那些必须在预处理过程中去除从而保证终处理步骤可靠的杂质取决于所选择的终处理步骤以及终处理步骤对杂质的耐受程度。如果预处理不充分，最终导致的问题可能会非常严重，参见下表4-1

37、:Table4-1表4-1MAGNITUDEOFPROBLEMSINFINALTREATMENTCAUSEDBYTYPEOFIMPURITY由杂质类型引起的终处理中的问题大小程度IMPURITY杂质FOULING:causedbyparticulates污垢：由粒子引起SCALING:causedbyhardnessandminerals结垢：由硬度和矿物引起CORROSION:causedbychlorides府蚀：由氯化物引起DEGRADATION:causedbychlorine分解：由氯引起ReverseOsmosis反渗透Large大Large大None无Large*大*OtherM

38、embraneProcesses其它膜工艺Large-moderate大-中Large-moderate大-中None无Large*大*SingleEffectDistillation单效蒸储Moderate中Moderate中Moderate-large大-中Large大Multi-effectDistillation多效蒸储Large-moderate大-中Large-moderate大-中Moderate-large大-中Large大VaporCompressionDistillation蒸汽压缩蒸储Moderate中Moderate中Small小Large大*Membranedepen

39、dent*取决于膜Pretreatmentrequirementsforfeedwatertothefinaltreatmentprocessusuallyinclude:终处理的给水所做的预处理要求通常包括：FORMEMBRANES相对于膜Theconcernsarefoulingbysuspendedsolids(particulates)andscaling(precipitatingsolids)aswaterisremoved.Atypicalgoalforcontrolinpretreatmentmightbeasiltdensityindex(SDl)of3-5andhardne

40、ssof<1grain/gallonforon-siteanalysis.Membranestoleratechloridesbutonlysomemembranestoleratechlorine.它所担心的是水移开后由悬浮固体(粒子)引起的污垢和结垢(致沉淀的固体)。在预处理中控制的最典型目标是在线分析的泥沙密度指数(SDI)为3-5,硬度<1格令/加仑。膜能够耐受氯化物，但是仅有一些膜能够耐受氯。FORDISTILLATION相对于蒸储Theconcernsarescaleformationduetohardnessandcorrosionduetochlorides.Typ

41、icalwaterqualitymightbeashighas1.0Mohm/cm,whichoftenrequiresadditionaltreatmentbeyondpretreatment,i.e.ROorultrafiltration.Distillationhasnotoleranceforchlorineduetocorrosionandcarryovertotheproduct.Distillationhassometoleranceforparticulates.它所担心的是由硬度引起的结垢以及由氯化物引起的腐蚀。代表性的水质可能有1.0Mohm/cm那么高，除了预处理以外经常

42、还需要一些附加处理，即RO或超滤。由于腐蚀和带给产品污染的原因，蒸储并不耐氯。但是蒸储对粒子却有一些耐受力。Pretreatmentgenerallyhaslittleeffectontheotherparametersindicativeofwaterqualitysuchasanions,microbiallevels,conductivity,totalorganiccarbons(TOC),andvolatiles.预处理一般来说会对影响水质的其它参数有一点影响，比如阴离子、微生物水平、电导率、总有机碳(TOC)和挥发性。Selectingpretreatmenttoreliablyp

43、rovidetherequiredfeedwaterqualitytofinaltreatment,inspiteofspikesinfeeddrinkingwaterquality,willreduceoperatingandmaintenancecostsinfinaltreatment.选择预处理来为终处理提供所需水质的给水，将会减少在终处理中的操作和维护费用，尽管供给的饮用水中有杂质峰。4.5 CONTROLOFFOULING:REMOVALOFTURBIDITYANDPARTICULATES污垢的防治：浑浊度和粒子的去除Theprincipalmethodsforremovingpa

44、rticulatesandreducingturbidityare:去除粒子以及降低浑浊度的主要方法是：?Clarificationandtheaccompanyingoperationsofflocculation,coagulation,andsedimentation澄清以及絮凝、凝结和沉淀的附随操作?DepthorMediafiltrationincludingsingleandmultimediafiltration(particlesretainedbythemedia)深层和介质过滤，包括单一过滤和多重过滤(介质中所含的粒子)Thedefinitions,filtrationme

45、chanismsandtypicalremovalprocessesfortheseareoutlinedinChapter11.第11章中将概述它的定义，过滤机制和这些杂质的典型去除工艺。Clarificationisnotapplicable,asfeedwatersourcesarepotablequalityorbetter.澄清是不适用的，当给水水源是适合饮用或更好时。Depthormediafiltrationisusedinpharmaceuticalwatersystemsandisoftenthefirststepinapretreatmentsystem.Multi-siz

46、edsandisthemostcommonmedia,butothermediamayprovidebetterperformancewithsomefeedwaters.Removalofparticulatesdownto10micronsispossibleanddependsonselectionofmedia.Microbialgrowthisakeyconcerninamediafilter,unlessthefeedwatercontainsamicrobialcontrolagent.Otherwise,microbialcontrolinthedepthfilterisreq

47、uired(e.g.,periodicsanitizationusingeitherheatorachemicalsanitizingagent).深层和介质过滤用于制药给水系统，通常也是预处理系统的第一步。大小不一的沙子是最普遍介质，但是其它介质可能会为某些给水提供更好的性能。去除10微米以上的粒子是有可能的，这取决于所选的介质。在介质过滤中，微生物的生长是担心的关键，除非给水中含有微生物防治因子。否则，深层过滤中就需要对微生物进行防治(例如，用加热或化学消毒剂进行定期灭菌)。4.6 CONTROLOFSCALING:REMOVALOFHARDNESSANDMETALS水垢的控制：硬度和金属

48、的去除Whenwaterisseparatedfromitsimpuritiesinthefinaltreatmentprocess,thosecompoundswithlowsolubilityareconcentratedtothepointwheretheyprecipitate.Thisprecipitation,orscaling,istheresultofexceedingthesolubilityofthedivalentandtrivalentcations,usuallyasasparinglysolublesaltsuchascarbonateorsulfate.Theme

49、thodsofcontrolare:在最终的处理工艺中将水和杂质分离开后，那些微溶性的化合物就会浓缩到它们的深沉点。这些沉淀或水垢，通常是一种像碳酸盐或硫酸盐之类的微溶性的盐超过了它二价和三价阳离子溶解度的结果。控制方法有：?Removalbyionexchange.Theseareprincipallycalciumandmagnesiumandmayincludedivalentandtrivalentionssuchasiron,aluminumandsilica.Pretreatmentisusuallywatersoftening,(exchangingtheionscausingh

50、ardnessandscalingforsodiumions).用离子交换去除。这些主要是钙和镁，也有可能包括一些二价和三价离子，像铁、铝及硅。通常的预处理是水软化(将钠离子与引起硬度和水垢的离子进行交换)?Removalofcarbonatebyacidification.Acidificationconvertsthecarbonatetocarbondioxide,whichisremovedbysubsequentdegasification.加酸去除碳酸盐。酸会使碳酸盐转化成二氧化碳，它在后面的脱气中即可去除。?Removaloftheoffendingcompoundbyabarr

51、ierfiltrationprocesssuchasnanofiltration.Waterpassesthroughthemembraneandcompoundsareretainedbythemembraneandremovedasapurgestream.用钠滤之类的屏障过滤过程去除引起困扰的化合物。让水通过膜，化合物作为一个净化流就被留在膜上去除掉了。TheseremovalprocessesaredetailedinChapter11.这些去除工艺将在第11章详细讨论。Watersofteningionexchange,whichremovesdivalentandtrivalent

52、ionsandreplacesthemwithsodium,isaverycommonprocessusedinpretreatmentofpharmaceuticalwater.Itisapplicableforallflowratesandallhardnesslevels,andiswellunderstoodandeasytooperate.Itinvolvesthehandlingofsaltonly,andproducesanon-hazardouswastestream.However,thehightotaldissolvedsolids(TDS)inthewastestrea

53、mmaylimitdisposaloptions.WatersofteningisalsoeasilycontrolledmanuallyorwithaPLC.水软化离子交换是用钠代替水中的二价和三价离子，它是制药用水预处理中非常常用的方法。它可用于各种流率和各种硬度水平，并且易于掌握和操作。它只涉及盐的处理，并且排出的废液是无害的。然而，废水中高的总溶解固体(TDS)量可能会限制处理选项。水软化也易于用手动或PLC控制。Forlargeflowrates(>50gpmor0.18m3/min)andhighhardness(>50ppm)degasification(aftera

54、cidification)maybetheprocessofchoice.ThisdegasificationprocessisoftenemployedbetweenthetwostagesofanROandinvolvesthehandlingofacidandbasefortwopHadjustments:对于大流率(>50gpm或0.18m3/min)以及高硬度(>50ppm)的水，可选则脱气(酸化后)。该脱气过程常用于两级反渗透之间，并涉及酸碱处理的两个pH调节：LoweringofpHbeforefirststageofRO一级反渗透前降低pHIncreasingofp

55、HbeforesecondstageofRO二级反渗透前增加pHTheprincipaladvantageisthatthecarbondioxideisreleasedtotheatmosphereratherthanbeingaliquidwastestreamrequiringdisposal.主要优点是：二氧化碳释放到大气中而不是留在需处理的废液中。Nanofiltrationisamembraneprocessthatmaybeapplicablewithcertainfeedwatersandspecializedsituations.Thefiltrationisusuallyc

56、ross-flowandinvolvesasignificantpurgestream.ItismuchlikeRO,thedifferencesbeingporesizeinthemembraneandthecorrespondingeffectonionremoval.Removalofdivalentionscanbegreaterthan98%.纳米过滤是一种膜处理，它可能用于特定的给水和特殊的情况。该过滤通常是错流，并涉及一个重要的除污流。它和反渗透非常相似，它们之间的差别是膜的孔径不同，以及相应的去除离子的效果的不同。二价离子的去除水平可大于98%。Chemicalinjectio

57、nisanalternatemethodtocontroltheionsorcompoundsthatcontributetoscaling.Thisprocessinjectsacompound(usuallyaproprietaryorganiccompound)tothefinaltreatmentfeedwater.Thesecompoundsarecalledsequestrantsandact"totieupandcomplex"theoffendingionsorcompoundstoformacomplex,orcompound,thatismoresolu

58、bleandwillnotprecipitateinthefinaltreatmentprocess.The"complexedionandsequestrant"havealargemolecularweightandareremovedasapurgestreaminthefinaltreatmentprocess.Sequestrantsarealmostalwaysproprietarycompounds,whichrequiretestingtoverifyapplicabilityanddosagelevelfortheparticularfeedwater,andanalysistoverifyremovalinthefinaltreatmentprocess.可选择用添加化学药品的方法来控制离子或易于结垢的化合物。该处理是在给水的最后处理时，向其中添加化合物(通常是专用有机化合物)。该化合物被称为多价螯合剂，它的作用是将需去除的离子或化合物“连接或复合”起来形成一个复合