effects of biogas and septic tank sludge centrate on microalgae … · 2017. 10. 17. · learning...
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Effects of Biogas and Septic Tank Sludge Centrate on Microalgae Cultivation
Lu.Dingnan(Ma,hew)DoctoralStudentProf.Zhang.Xiaoqi(Jackie),Ph.D.,P.E.
Civil&EnvironmentalEngineeringUniversityofMassachuse,sLowell
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Presented by
Nihar R. Mohanty, Ph.D. Environmental Engineer, MassDEP
Adjunct, Civil &Environmental Engineering, Umass Lowell
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Introduc)on(MicroalgaeandAnaerobicdiges)on) • Integra)onofmicroalgae-basedanaerobic
diges)on(AD)andwastewatertreatment(WWT)
canprovidemanyenvironmentalandeconomic
advantages:
ü ElectricalpowerandheatforAD
ü Offsetenergyconsump)onforalgae
cul)va)on,processingandextrac)on
ü NutrientsremovalinWWT
ü Poten)altoreplaceac)vedsludge
ü Poten)altominimizeCO2emission
Algaecul)va)onpondinIsraelforbiofuel
hLps://www.greenprophet.com/2011/09/seabio)c-biofuel-algae/
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Introduc)on(Biogas&biogaspurifica)on) • Maincomponentsofbiogas:
ü MethaneCH4(40-70%)
ü CarbondioxideCO2(30-60%downgrade
engineefficiency)
ü HydrogensulfideH2S(tracelevels,
contributestocorrosionofpipelinesand
engines)
ü Watervapor
• Currentpurifica)onmethods(physical
absorp)on,chemicalsolvents,membrane
separa)on,etc.)areenergyintensive.
Biogaspurifica)onsystembypressurizedwater(physicaltreatment)
hLp://www.sarlin.com/sarlin_products/Biogas-upgrading-plants/z3awigjh/2a12e6e6-e2e0-4eb1-a63f-9399f4ca1b25
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• AlgaecanscrubCO2andH2Sfrombiogas:
ü Lowcost
ü Highefficiency
ü Increasesmicroalgalproduc)vityandnutrient
assimila)on
ü CO2frombiogascancontrolthepH(~8.0)in
culturesolu)on(preventNH3andP04)
ü FirstproposedbyOswaldandGoluekein
1960
ü MinimizetheCO2emissiontoatmosphere
Introduc)on(Biogaspurifica)onbymicroalgae)
Biogaspurifica)onsystembyalgae(biologicaltreatment)
hLps://www.israel21c.org/is-2016-the-year-of-the-algae/
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Introduc)on(microalgaeandWWT) • Cul)va)onofmicroalgaeindifferenttypesof
wastewater:
ü Reducenutrients(NandP)
ü Reducesolublechemicaloxygendemand
(sCOD)
ü Increasedalgaeproduc)on
ü Currentlytestedonprimaryeffluent,
industrialeffluentandhigh-strength
wastewater(Wang,etal.2010;Wang,etal
2014)
Theuseofalgaeinwastewatertreatment
hLps://doi.org/10.1016/S0015-1882(14)70180-6
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Introduc)on(Sep)ctanksludgeanditscentrate) • Sep)ctanksludge(STS):
ü Isthefinalproductofonsitewastewater
treatmentsystem(sep)csystem)
ü 20%popula)onintheUSreliesonsep)c
systems
ü Usuallyhashighconcentra)onsoforganic
carbon(~10,000mg/L),ammonianitrogen
(~250mg/L),andphosphate(~55mg/L)(Diaz-
Valbuenaetal.2011).
• Sep)ctanksludgecentrate(STSC):
ü Rarelystudied
ü Poten)allyagoodmediumforalgaeculture
STSC
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Introduc)on(algaegrowthkine)cs) • Idealmicroalgaegrowthkine)cscanbe
determinedifcellsaregrownundersimilar
condi)ons(asshownincurve)
• Thegrowthrateisalwayscontrolledbythe
mostlimitednutrient
• Thenutrientlevelscanalsoaffectthelipid
contentincells(Khozin-GoldbergandCohen
2006,Rodolfietal.2009,Xinetal.2010)Graphicalrepresenta)onsofideal
microalgaegrowth hLp://web.pdx.edu/~rueterj/courses/esr473/notes/compe))on.html
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Objec)ves
• Evaluatetheeffectsofusingbiogasandsep)ctanksludgecentrate(STSC)asthe
majorcarbonsourcesandgrowthmediumformicroalgalcul)va)on.
1. Studytheeffectofbiogasonmicroalgalbiomassgrowth(autotrophic
metabolism);
2. StudytheeffectofSTSConmicroalgalbiomassgrowth(heterotrophic
metabolism);
3. Analyzetheeffectofbiogasonnutrient(NandP)removalfromSTSC;
4. Studythekine)csofnutrientremovalbasedonbiologicalassimila)on;
5. StudytheeffectofbiogasandSTSConmicroalgallipidcontent.
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Significance
ADofmicroalgaetoproducebiogas
Thisstudy
Cul)va)onofmicroalgaeto
generatebiomass
• ADofmicroalgaehasbeenwidelystudiedand
proventoproducecleanenergy–methane
• Cul)va)onofmicroalgaeindifferenttypesof
wastewaterforbiomassproduc)onandWWT
isalsoreceivingaLen)on
• Thisstudyaimstointegratethetwoaspects
• Webelieve:
Ø Iftheprocessesofmicroalgae-basedbiogaspurificaLon
andanaerobiccentratereusecanbeintegrated,wecould
redefinetheroleofmicroalgaeinenvironmentalengineering
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Materials(STSCandmicroalgae) • STCS:
ü Filteredusingglassfiberfilters
ü Autoclavedat120oCfor30min
• Microalgae:
ü Strainwasisolatedfromtheprimary
clarifiersattheLowellRegional
WastewaterU)lity
ü Cul)vatedinthemodifiedBoldBasal’s
medium(BBM)
SinglemicroalgalcellimageobtainedinUmassLowellEnvironmentalLab
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Methods(experimentaldesign) • 500mLcultureboLleswith400mLworkingvolumefor10days
• Metalcapwithtwostainlesssteelfiongsandrubberwasher
• Biogascircula)onfromaTedlarbagtoculturesolu)on,forcedbya
peristal)cpump(10mL/min)
• 30oCand24hrillumina)onatroughly3,000Lux
Schema)cdiagramformicroalgaecul)va)on
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Cul)va)onApparatus
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Methods(groupset-up) 1. Assay(T1):biogasandBBM
2. Assay(T2):airandBBM
3. Assay(T3):N2andBBM
• ComparisonbetweenT1andT2canshowtheadvantageofhigh
concentra)onofCO2frombiogas
• ComparisonbetweenT3andT6cantestthepoten)alofheterotrophic
pathwayofmicroalgaeinSTSCandcanshowtheadvantagesofjointeffect
frombiogasandSTSC
4. Assay(T4):biogasandSTSC
5. Assay(T4):airandSTSC
6. Assay(T4):N2andSTSC
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Results(T1vs.T2)
0
200
400
600
800
1000
1200
0 2 4 6 8 10VS
S(m
g/L)
Days
T1(Biogas/BBM)T2(Air/BBM)
• BiomassProduc)on(measuredbyvola)le
suspendedsolidsVSS):
ü T1’sbiomassproduc)on(890mg/L)
ü T2’sbiomassproduc)on(495mg/L)
• Specificgrowthrate(μ)(unit:day-1)
ü T1andT2bothhadthehighestμat
day4-5
ü T1μ(0.53d-1)
ü T2μ(0.35d-1)
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Results(T3vs.T6)
0
100
200
300
400
500
600
0 2 4 6 8 10VS
S(m
g/L)
Days
T6(N2/Centrate)T3(N2/BBM)
• BiomassProduc)on(measuredbyVSS):
ü T3’sbiomassproduc)on(nega)ve)
ü T6’sbiomassproduc)on(306mg/L)
• Specificgrowthrate(μ)(unit:day-1)
ü T6hadthehighestμatday1-2
ü T6μ(0.55d-1)
• Resultsshowashorthyper-growthperiod,
indica)ngincreasedheterotrophic
metabolismofmicroalgaeinSTSC
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Results(T4vs.T5)
0
200
400
600
800
1000
1200
0 5 10VS
S(m
g/L)
Day
T4(Biogas/Centrate)T5(Air/Centrate)
• BiomassProduc)on(measuredbyVSS):
ü T4’sbiomassproduc)on(1,074mg/L)
ü T5’sbiomassproduc)on(471mg/L)
• Specificgrowthrate(μ)(unit:day-1)
ü T4hadthehighestμatday1-2(0.59
d-1)
ü T5hadthehighestμatday4-5(0.45
d-1)
• Resultsshowamaximumbiosynthe)crate
governedbymixotrophicmetabolism
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Results(PhosphateremovalforT4andT5)
6
8
10
12
0
2
4
6
8
10
0 5 10
pH
PO4-P(m
g/L)
Days
T4(PO4-P) T5(PO4-P)T4(pH) T5(pH)
• Bothassaysshowsignificantreduc)onof
phosphate(T4=97.27%,T5=98.87%)
• T4hadslowreduc)onrate4.14mg/L*d-1
• T5hadincreasedreduc)onrateof8.10
mg/L*d-1
• IncreaseinpHwith)meofT5indicates
phosphateprecipita)on
• T4’spHwasbufferedduetohighCO2
concentra)oninbiogas
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Results(AmmoniaremovalforT4andT5)
6
8
10
12
0
20
40
60
80
100
120
0 5 10
pH
NH 3-N(m
g/L)
Day
T4(NH3-N) T5(NH3-N)T4(pH) T5(pH)
• T5hadgreaterammoniaremovalthanT4
(T4=71.50%,T5=98.96%)
• Por)onofvola)liza)onofammoniainT5
canbecalculatedbyequa)on
Ø FAN/TAN=1/(1+10(pKa-pH))
• InT5,80.92%ofammoniawasvola)lized
(only18.04%wasusedbymicroalgae)
• InT4,ammoniavola)liza)onwas
neglected
• Again,inT4,thepHwasbuffereddueto
thepresenceofbiogas
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Results(Algaegrowthkine)csofnutrientremovalforT4)
• (Y)Yieldofbiomasswithrespecttothenutrientconsump)onofphosphorusor
nitrogen:
Ø YP=(B-B0)/(P0-P);YN=(B-B0)/(N0-N) {Bisbiomass}
• YP/YNis8.95
• IdealN/Pra)o(Yideal)formicroalgaeis7.2(C106H181O45N16P)(Grobbelaar,2003)
• YP/YN>Yidealindicatesthephosphoruswasthelimi)ngnutrient
• Kine)csofnutrientremovalshouldfocusonlimi)ngnutrientP.
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Results(Algaegrowthkine)csbasedonphosphateremovalforT4)
0
0.05
0.1
0.15
0.2
0.25
0.3
0 2 4 6 8 10
μ(d
-1)
PO4-P(mg/L)
KS
1/2(μmax)
μ=(0.29)*[S/(S+0.65)]
• Monodequa)onwasused
Ø dx/x=[μmax*S/(Ks+S)]*dt
• Microso{ExcelSolverwasusedto
determinetheMonodequa)oncoefficients:
Ø μmax=0.29(d-1);Ks=0.65(mg/L)
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Results(Lipidanalysis)
0
5
10
15
20
25
30
Lipid%
• T1andT2hadsimilarlipidcontents
ü T1(17.3%),T2(18.9%)
• T5hadhigherlipidcontentthanT4
ü T4(12.3%),T5(24.1%)
• Thevola)liza)onofNH3and
precipita)onofPO4inT5causedthe
“nutrientsdeficientcondiLon”,and
significantlytriggeredthemicroalgaeto
accumulatelipid.
• Thissitua)onwaswidelyobservedbyotherresearchers(Khozin-Goldberg
andCohen2006,Conver)etal.2009,Rodolfietal.2009,Xinetal.2010).
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Conclusion
• Biogasandsep)ctanksludgecentratecancausemicroalgaetoshi{tomixotrophic
metabolism,andsignificantlyincreasebiomassproduc)on
• Biogascontainshighconcentra)onofCO2,canbufferthepHofculturesolu)onand
preventammoniavola)liza)onandphosphateprecipita)on
• Phosphateisthelimi)ngnutrientinthiscul)va)onsystem,anditsconcentra)on
canbeusedtopredictthemicroalgaegrowth
• Nutrientdeficientcondi)oncancausethemicroalgaetoaccumulatemorelipid
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Acknowledgements
• TheauthorswouldliketoacknowledgethefundingsupportfromtheUniversityof
MassachuseLsLowell(UML).
• TheauthorsthankProf.MarkHinesfromtheBiologicalSciencesDepartment
assistanceinthebiogasanalyses.
• TheauthorswouldalsoliketothankthestaffattheLowellRegionalWastewater
U)lityforassistanceinobtainingsep)csludgeandclarifiersupernatant.
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Questions?