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October7,2016

NewDevelopmentsinBioWin5.1Theprimaryfocusofthisreleasehasbeentoimprovebothsteadystateanddynamicsimulationspeed,particularlyfor(a)largeflowsheetsincorporatingmanyelements;and(b)systemsincorporatingbiofilmelements(e.g.mediabioreactorsinMBBRandIFASconfigurations,submergedaeratedfilters,tricklingfilters,etc.).

SpeedImprovements-SteadyStateSimulationThebasicmethodologyforsteadystatesimulationsremainsunchanged.Thatis,BioWinusesa“hybrid”solverthatcombinesaDecoupledLinearSearch(DLS)methodandaModifiedNewton-Raphson(MNR)method.ThesolvertypicallystartswithafewiterationsofDLS,andthenswitchestoMNRtofinish.TheMNRismuchmoreefficientatobtainingsolutions,butitiscomputationallyintensive.Forexample,inpreviousversionsofBioWin,theMNRcouldtakeuptoseveralminutesperiterationforsystemswithlarge,complexflowsheets.Giventhatseveraliterationsoftenarerequired,thistranslatedintosteadystatesolutiontimesof20-30minutesforverylargesystems.InBioWin5.1,thenumericalengineunderlyingtheMNRmethodhasbeenreplaced,resultinginhugegainsforlargeflowsheets.Forexample,inourinternaltestingwehavesystemsthatweretaking~200secondsperiterationreduceto~4secondsperiteration,i.e.50timesfaster!SpeedImprovements-DynamicSimulationBioWin5.1usesanewdynamicintegrationmethodknownasBDF(BackwardsDifferentiationFormula).TheBDFmethodisfasterthanthepreviousmethodforlarge,complexflowsheetsandflowsheetsincorporatingbiofilm-basedelements.OurBioWin5.1testinghasindicated:

• Largesystemsnotincorporatingbiofilmreactorsrun3–6timesfaster• Systemsincorporatingbiofilmreactorsrun10–50+timesfaster

IfyouopentheProject>CurrentProjectOptions>Numericalparameterstabshownbelow,theBDFmethodshouldbeselectedasthedefaultmethod–evenforafileyoucreatedina

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previousversionofBioWin.The“old”BioWinmethod(BWHeun)isalsostillavailablebecausethenewBDFmethodisnotyetavailableforsimulationofSBRsystems.

ModelChange–DiffusionofColloidalMaterialinBiofilmsBioWin’sbiofilmmodelhasalwaysincorporatedadiffusionrateforcolloidalmaterialintothebiofilmlayers.ThisparametercanbefoundontheProject>Parameters>Biofilm>Effectivediffusivitiestabshownbelow:

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InpreviousversionsofBioWin,thedefaultvalueassignedfortheeffectivediffusivityofcolloidalmaterialwas5.0x10-12.Thisvalueisgreaterthantheoneassignedtoparticulatematerial(e.g.particulatedegradableCODhasavalueof5.0x10-14),butlowerthansolublematerial(e.g.solublereadilybiodegradableCODhasavalueof6.9x10-10).Thefateofcolloidalmaterialinbiofilmsystemsisdirectlyimpactedbythisparametervalue.Forexample,considerthesystembelowconsistingoffourmovingbedbioreactor(MBBR)unitsinseries:

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Usingthedefaultdiffusivityparameters,thesolubleCODandBODprofilesareasfollows:

NotethatsolubleBODisnotsignificantlyreduceduntiltheendofthethirdMBBRunit(bottomchart).Thiscanbeexplainedbylookingatthetopchart.Althoughtheuptakeofsolublereadilybiodegradablematerialisnearlycompletebytheendofthesecondunit,theuptakeofcolloidalmaterialisnotasrapidandmuchofthesolubleBODleavingthesecondandthirdMBBRunitsisduetocolloidalmaterial.OurinvestigationsintoperformanceofsystemsliketheonepicturedabovesuggeststhatthesolubleBODisremovedtoagreaterextentbytheendofthesecondstage.Asaresult,inBioWin5.1thedefaultvalueassignedfortheeffectivediffusivityofcolloidalCODmaterialhasbeenincreasedto5.0x10-10.Thisvalueiscloserto,butslightlylessthan,thevalueassignedtosolublematerial(recallthatsolublereadilybiodegradableCODhasavalueof6.9x10-10).Thisresultsinmorecompleteremovalofcolloidalmaterialbytheendofthesecondstage,andgivesthesolubleBODprofileshownbelow:

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ModelChange–DissolvedOxygenHalf-SaturationConstantforPhosphorusAccumulatingOrganismsInpreviousversionsofBioWin,thephosphorusaccumulatingorganisms(PAO)usedthesamedissolvedoxygen(DO)half-saturationmodelparameterastheordinaryheterotrophicorganisms(OHO).ThisreflectedconventionalwisdomwhichsuggestedthatPAOsdidnottakeupphosphoruseffectivelyatlowDOconcentrations.However,currentresearch(Jimenezetal.,2014)suggeststhatPAOsareinfactabletotakeupphosphoruseffectivelyatverylowDOconcentrations.Toreflectthesefindings,BioWinnowincorporatesaseparatedissolvedoxygen(DO)half-saturationmodelparameterforPAOs.Thisimprovesthemodel’sabilitytotrackbiologicalphosphorusremovalbehaviorinsystemsoperatingunderlowDO/simultaneousnitrification-denitrificationconditions.ThisparameterisfoundviatheProject>Parameters>Kinetic>Switchestabshownbelow:

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ModelChange–CompressionSettlingofSolidsInBioWinuserscandefineasolidsconcentrationthatrepresentsthemaximumcompactabilityofsolidsinamodelsettlingtankunit(i.e.alimitonunderflowTSSconcentration).Inearlierversions,asthesolidsconcentrationinalayerofamodelsettlingtankapproachedthemaximumcompactabilityvalue,thatlayerwould“re-suspend”solidsintothelayerabove;inthiswaytheconstraintonmaximumcompactabilitywasmaintained.Thisapproachwasnotalwayssatisfactorybecause(a)undercertainconditionsitresultedinunstablebehavior,and(b)itdidnotproperlyreflectwhatphysicallyoccursassolidstransitionfromthehinderedsettlingregimetocompressionsettling.InBioWin5.1,theapproachformodellingsettlingbehaviorathighsolidsconcentrationsandimposingamaximumcompactabilityhaschanged.Thefollowingsectiondiscussesthenewapproachusedathighsolidsconcentrations,aswellastheapproachthathasalwaysbeenusedtomodelsettlingatlowconcentrations.SludgesettlingvelocityismodeledaccordingtotheVesilindequationforhinderedsettling.Thesettlingvelocityinagivenlayerisgivenby:

𝑉",$ = 𝑉&𝑒)*+, (1)where𝑉&=maximumsettlingvelocity(m/d),𝐾=hinderedsettlingparameter(m3/kgTSS),and𝑋$ =totalsuspendedsolids(TSS)concentration(kgTSS/m3)inlayeri.AcriticismofEq.1isthatitover-predictssettlingvelocitiesatlowconcentrations.Furthermore,thestandardVesilindequationdoesnotaccountforcompressionsettling.BioWinemploysswitchingfunctionstoswitchoffthesludgesettlingvelocityexpressionatverylowsolidsconcentrations,andalsoasthesolidsconcentrationapproachesthemaximumsolids

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compactabilityinthelowerlayersofthesettlingtank.Thisprovidesasimplifiedmethodofmodelingthepoorlyflocculatingsolidsintheupperlayersofthesettlingtank,andcompressionsettinginthelowerlayers.Asthesolidsconcentrationintheupperlayersapproachesauser-definableconcentration(theupperlayersettlingvelocityswitch),thesettlingvelocityapproacheszero,andsolidsarecarriedupwardsbytheoverflowstream(resultinginsolidsinthesettlingtankeffluent).Asthesolidsconcentrationinthelowerlayersapproachestheuser-definablemaximumcompactability,thesettlingvelocityisquicklyandsmoothlyreducedtozero.ThecompletesettlingvelocityequationusedbyBioWinis:

𝑉",$ = 𝑉&𝑒)*+, ⋅𝑋$

𝐾" + 𝑋$⋅

11 + 𝑒)23456788$39"7::;$9<=6>98$:$39?>@:36⋅(+BCD)+,) (2)

WhereKSistheupperlayersettlingvelocityswitch,XMAXisthemaximumcompactability,andothervariablesarethesameasinEq.1.Theswitchingfunctioneffectatlowconcentrationsforagivencombinationofsettlingvelocityparametersisshowninthefigurebelow:

YoucanincreasethesuspendedsolidsconcentrationatwhichsettlingvelocityisdecreasedbyincreasingtheKSparameter.VaryingtheKSparameterisapossiblewaytovarythepredictedeffluentsuspendedsolids.Theswitchingfunctioneffectathighconcentrationsinthelowerlayersofthesettlingtankforagivencombinationofsettlingvelocityparametersisshowninthefigurebelow.LoweringtheXMAXparameterisawaytosimulatepoorlycompressiblebulkingsludge.

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OtherUsabilityImprovementsThefollowingminorfixeshavealsobeenimplementedinBioWin5.1:

• YoucanchoosewhetherornottheNoteswindowisdisplayedwhenyouopenaBioWinfile,bycheckingoruncheckingtheAutomaticallyshownotesafterloadingfileboxunderTools>Customize>General

• UsersofpreviousversionsofBioWinreporteda“sluggish”behaviorinBioWinfilesthatincorporatedverylargetablesintheBioWinAlbum.Thisisnolongerthecase,solongastheuserdoesnotsetBioWintoupdatetablescontinuallyduringsimulations.TheSteadystatesimulationtableupdatesandDynamicsimulationtableupdatescheckboxesshouldremainatthedefaultuncheckedstate.

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• AprogressbarnowshowsatthebottomofthesimulationcontrolboxwhileBioWinplacesnumericalseedvaluesinallflowsheetelements.Thiswillonlybereadilyevidentonlargeflowsheetswithmanyelements.

• Improvedplottingseriesnamingformulti-layerelements(e.g.SAF).

• ItisnowpossibletodisplayaRateswindowforaSAFelement.

• Tighternumericaladherencetosplitterswith“zero”fractionsandratesspecifiedforastream.

• Anaerobicdigestersandvariablevolumebioreactorsmaynowbesetto“constant”

volume.

• BiofilmdetailstablesintheAlbummaynowbecopiedtotheclipboardforexportingtoExcel.

• ThesoftwarepackagethatBioWinusesforitschartingengine(TeeChart)hasupdated

toanewversion.ThefunctionalityissimilartowhatitwasinpreviousBioWinversions,buttheinterfacehaschangedsomewhat.

ReferenceMainstreamNitrite-ShuntwithBiologicalPhosphorusRemovalattheCityofSt.PetersburgSouthwestWRF.Jimenez,J.,Wise,G.,Burger,G.,Du,W.andDold,P.ProceedingsoftheWaterEnvironmentFederation86thAnnualTechnicalExhibition&Conference,NewOrleans,Louisiana,USA,September27toOctober1,2014.