View
219
Download
0
Category
Preview:
Citation preview
1
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
2
previousversionofBioWin.The“old”BioWinmethod(BWHeun)isalsostillavailablebecausethenewBDFmethodisnotyetavailableforsimulationofSBRsystems.
ModelChange–DiffusionofColloidalMaterialinBiofilmsBioWin’sbiofilmmodelhasalwaysincorporatedadiffusionrateforcolloidalmaterialintothebiofilmlayers.ThisparametercanbefoundontheProject>Parameters>Biofilm>Effectivediffusivitiestabshownbelow:
3
InpreviousversionsofBioWin,thedefaultvalueassignedfortheeffectivediffusivityofcolloidalmaterialwas5.0x10-12.Thisvalueisgreaterthantheoneassignedtoparticulatematerial(e.g.particulatedegradableCODhasavalueof5.0x10-14),butlowerthansolublematerial(e.g.solublereadilybiodegradableCODhasavalueof6.9x10-10).Thefateofcolloidalmaterialinbiofilmsystemsisdirectlyimpactedbythisparametervalue.Forexample,considerthesystembelowconsistingoffourmovingbedbioreactor(MBBR)unitsinseries:
4
Usingthedefaultdiffusivityparameters,thesolubleCODandBODprofilesareasfollows:
NotethatsolubleBODisnotsignificantlyreduceduntiltheendofthethirdMBBRunit(bottomchart).Thiscanbeexplainedbylookingatthetopchart.Althoughtheuptakeofsolublereadilybiodegradablematerialisnearlycompletebytheendofthesecondunit,theuptakeofcolloidalmaterialisnotasrapidandmuchofthesolubleBODleavingthesecondandthirdMBBRunitsisduetocolloidalmaterial.OurinvestigationsintoperformanceofsystemsliketheonepicturedabovesuggeststhatthesolubleBODisremovedtoagreaterextentbytheendofthesecondstage.Asaresult,inBioWin5.1thedefaultvalueassignedfortheeffectivediffusivityofcolloidalCODmaterialhasbeenincreasedto5.0x10-10.Thisvalueiscloserto,butslightlylessthan,thevalueassignedtosolublematerial(recallthatsolublereadilybiodegradableCODhasavalueof6.9x10-10).Thisresultsinmorecompleteremovalofcolloidalmaterialbytheendofthesecondstage,andgivesthesolubleBODprofileshownbelow:
5
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:
6
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
7
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.
0
1
2
3
4
5
6
7
8
0 2 4 6
SE
TT
LIN
G V
EL
OC
ITY
(m/h
)
SOLIDS CONCENTRATION (kg/m3)
Traditional Vesilind
Modified Vesilind
8
OtherUsabilityImprovementsThefollowingminorfixeshavealsobeenimplementedinBioWin5.1:
• YoucanchoosewhetherornottheNoteswindowisdisplayedwhenyouopenaBioWinfile,bycheckingoruncheckingtheAutomaticallyshownotesafterloadingfileboxunderTools>Customize>General
• UsersofpreviousversionsofBioWinreporteda“sluggish”behaviorinBioWinfilesthatincorporatedverylargetablesintheBioWinAlbum.Thisisnolongerthecase,solongastheuserdoesnotsetBioWintoupdatetablescontinuallyduringsimulations.TheSteadystatesimulationtableupdatesandDynamicsimulationtableupdatescheckboxesshouldremainatthedefaultuncheckedstate.
0.00
0.05
0.10
0.15
0.20
0.25
8 10 12 14 16
SE
TT
LIN
G V
EL
OC
ITY
(m/h
)
SOLIDS CONCENTRATION (kg/m3)
Traditional Vesilind
Modified Vesilind
9
• 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.
Recommended