How To Conduct a Jar Test - Dober

Water treatment jar testing is a method of mechanically and physically testing chemical treatments on samples of wastewater to determine the optimal ... WATERTREATMENT JARTESTINGMADEEASY WhatIsAJarTest? Watertreatmentjartestingisamethodofmechanicallyandphysicallytestingchemicaltreatmentsonsamplesofwastewatertodeterminetheoptimalchemicaltreatmentandrelatedchemicaldosagesforaspecificwaterorwastestream.Essentially,jartestingisascaleddownversionofawatertreatmentsystem.Itisgreatforgettinga“snapshot”ofwhatwillbeneededtotreatthewateronalargerscale.Itisimportanttonotethat,justbecauseacertaintreatmentwillworkduringjartesting,on-sitetrialsandscalingupisrequiredtoconfirmtherecommendedprogramanddetermineifadjustmentsareneeded. CanISkipTheJarTest?   Wedon’trecommendit!   TheJarTest isthesinglemostimportanttoolusedindeterminingthebestchemicalpathforachievingindividualwatertreatmentgoals.Throughjartesting,youareabletotesthowspecificchemicalswillfunctionwithinyourtreatmentsysteminordertodeterminewhatchemicalsarebestforyourspecificapplication.Thetestnotonlysavestime,butitsavesmoney,aswell.Throughjartesting,youcantestdifferenttreatmentdosagestoensureyouarenotoverusingandoverspendingonchemicals.   Jartestingisalsousefulbecauseitcanhelpyoudeterminewhataspecificwastestreamconsistsof,alongwithwhetherthesampleofwastewaterwillrequireapHadjustment,filtration,ordifferentchemicalloadthanoriginallyexpected.Everywastewatersamplehasauniquecomposition,requiringauniquetreatment.Jartestsarethebestandmostefficientwaytodeterminethebesttreatmentsystem. TestingEquipment Todoextensivejartesting,itisbesttousewhatiscalledagangstirrer.(Werecentlybrokedowntheprosandconsofsixstirrersonthemarket.)Agangstirrerisaninstrumentthatcanstirmultiplebeakersofwateratatime,somultipledifferentchemicalsordosagescanbetestedonasampleatonce.Theinstrumentalsoensuresthatthemixingisuniformthroughoutthesamples.However,youcanstillcompleteajartestwithoutaccesstoagangstirrer.Grababeaker,oranothercontainer,toholdthewater,andfindsomethingthatcanbeusedtomixthewaterthoroughly.   Onceyouhaveyourstirringsystemsetup,youwillneedtoacquirethechemicalsthatyouplantotestonthewater.Thechemicalsshouldincludeacoagulant,flocculant,orboth.SometimesanacidorbaseisalsoneededduetocertainwastestreamsrequiringapHadjustmenttobetreated.   Otherequipmentrequiredforeffectivejartestingincludessyringes,pHmeters,magnets,anotebook,andapen. FullList ofJarTestingEquipmentRequired: Mixingdevice(Gangstirrerifavailable,otherwisemagneticmixingplates) GlassBeakers,bottles Syringes pHmeterorpHpaper Chemicals Timer GraduatedCylinder Magnets(formixingplates) Notebook     JarTestingChemicalSelection Typically,whencompletingajartest,twodifferentchemicalsareused.ThepHofthewastewaterbeingusedinthetestmayalsoneedtobeadjusted.Thesequenceofchemicaladditionsisimportant. pHAdjust–SometimescoagulantsandflocculantswillnotworkatacertainpH.Sometimesanoilywastestreamrequireswhatwecallan,“Acidcrack.”ThisiswhenyouadjustthepHoftheoilywaterwithacid,andthoseoilsarepulledoutofthewater.Thismakestreatmentmucheasier.Afteracidcracking,youcanbringthepHbackuptoadesiredlevelwithabaseorcausticsoda. Coagulantshavepositively-chargedmoleculesand,whenaddedtowastewater,theydestabilizethenegatively-chargedparticlesinthewater.Theprocessofcoagulationcreates“pinflocs.”Pinflocsaresmall,neutrally-chargedmolecules.Pinflocswilleventuallysettle,buttheymaystaysuspendedlongerthanlargerflocparticleswould,becausepinflocsarenotasheavy. Flocculantshavelongerpolymerchainsthancoagulantsdo;therefore,theylinkmoreparticlestoapolymerchain.Flocculantswillcreate“macrofloc,”whichareclumpsofsolidslargerthanpinflocs.Macroflocswillsettlefasterthanpinflocsbecausetheyareheavier.     ConductingaJarTest Tobegin,makesureyouunderstandthegoalsofyourtest.Whatarethetreatmentgoalsforthewater?Whatiscurrentlybeingusedfortreatment?IsthewaterinaDAFtank?Willitberunthroughafilter?Allofthesequestionscangreatlyaidinthejartestingprocessandsaveyoutime.Next,collectarepresentativesampleofthewastewater.Arepresentativesamplemeansthesamplehasbeenmixedverywell,andthatyouarecollectingfromthebottomup.Havingarepresentativesampleensuresyouaregettingafullprofileofthewastewater.Ifyoucollectwaterfromthetopofasample,youwon’tbegettingmaterialthathassettledorthathasagreaterdensity.Now,placeyourwaterinto4-6600mLbeakers.Fillthebeakersupto500mL.Placeyoursamplesontheinstrumentyouareusingtomix,suchasagangstirrerwithnumerouspaddles.Setthemixingtimeonthestirringinstrumenttoreflecthowitwouldbemixedintreatment,orsetatimerifyouarewithoutagangstirrer.Gatheryourchemicals.ThiscanincludepHadjusters,suchassulfuricacidandcausticsoda,aswellasyourcoagulantsandflocculants.Ifthewaterisoily,youmayalsohaveanoilemulsifier. Whilethewatersamplesarebeingstirred,checkthepHofthesample.ThiswillhelpdetermineifapHadjustmentisneeded.CausticsodawillincreasethepH,andanacidsuchassulfuricacidwilllowerthepH.WerecommendcheckingyourcoagulantsandflocculantstoseewhatpHtheyworkbestat.Reviewanynecessarybackgroundinformation,aswell.SometimeswatermustbeatacertainpHdependingonthecompanyorwastestreamyouaregettingitfromduetodifferentneedsandregulations.     OncetheoptimalpHisachieved,itistimetoscreenyourcoagulants.Thecoagulantsneedtobedilutedinordertoaccuratelydosethem.Thisisdonebyadding10%ofthecoagulantto90%waterandmixing,creatinga10%coagulantsolution.(Example:10mlsofcoagulantinto100mlsofwaterwouldbea10%solution).Withthissolution,every1mLaddedtothe500mLofwaterequatesto200partspermillion(PPM)ofchemical.Onedropofthiswillbeequalto10ppmofchemical. Next,lineupthecoagulantsolutionsthatyouwishtotest,oneinfrontofeachbeaker.Ineachbeaker,add10ppmofchemical,oronedropfrom1mLsyringe.Mixat100rpmfor1minute.Notethatrpmandmixtimeswillvarydependingonactualoperatingparameters.After1minute,stopmixingandobserve.Atthecoagulationphase,wearelookingforsmallormicro-particlesoftenreferredtoasa“break”.Theamountofparticlescombinedwiththelevelofclarityinbetweenthoseparticlescanindicateadequatechemicaldosing.Continuedosingandmixingat10-20ppmincrementsuntilthedesiredamountofparticlesandlevelofclarityisachieved.   Onceitisdeterminedthatanoptimumcoagulationdosagehasbeenachieved,thenextstepistodiluteaflocculant.Theflocculantneedstobemixedwithwatertomakeasolution.Typically,a0.25%solutioninwateriscreated.Thesolutioncanbeachievedbytaking1.25mlofflocculent,addingitto500mlofwater,mixingthoroughlybyshakingormixing.Adding1mlofa0.25%solutionofflocculantto500mlofwaterequatestoadosageof5ppm.Ineachbeaker,add1mloftheflocculantsolutionandmixfor1minuteatanrpmof75.Duringtheadditionofaflocculant,lookforlargeflocparticlescalledmacroflocthatarepopcorn-likeinappearance,well-formed,andseparatedfromeachother.Stopthemixerafteryouseelargeflocparticlesform.Toknowifthewatermeetsyourtreatmentgoals,thereareafewextrastepsyoucantake.Youcanfilterthewaterandmeasuretheturbidityonaturbidityreader,youcanlookattheclarityandappearanceofthewater,oryoucanputitthroughdifferentmicronlevelsoffilters.Iftheclarityandflocformationdonotmeetyourtreatmentgoals,thistypicallymeansthatothercoagulantsorflocculantsneedtobeevaluated.Selectadditionalproductsandproceedwithsteps3-16untilthedesiredtreatmentisachieved.   NextSteps Interpretingresultsdependsontheuniquewastestreamandtreatmentgoals.Sometimesthewaterneedstobecrystal-clear,andothertimesitneedstobesemi-clear.   Itisimportantthatobservationsofjartestingtakeintoconsiderationthedesignoftheactualtreatmentsystem,andthatthebesteffortismadetoreplicatereal-lifetreatmentscenarios.Chemicalcontacttime,mixingenergy,settlingtime,volumeofsolids,soliddewaterability,andshearingpotentialareexamplesoffactorsthatneedtobetakenintoconsiderationwhenjartesting.   Lookingforassistanceconductingajartest?Doyouhavesamplesyou'dlikeourlabtotestforyou?Getincontactwithourlabteamtoday.