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


Presented by

Nihar R. Mohanty, Ph.D. Environmental Engineer, MassDEP

Adjunct, Civil &Environmental Engineering, Umass Lowell


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/


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


• 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/


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


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


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


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.


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


Materials(STSCandmicroalgae) • STCS:

ü Filteredusingglassfiberfilters

ü Autoclavedat120oCfor30min

• Microalgae:

ü Strainwasisolatedfromtheprimary

clarifiersattheLowellRegional

WastewaterU)lity

ü Cul)vatedinthemodifiedBoldBasal’s

medium(BBM)

SinglemicroalgalcellimageobtainedinUmassLowellEnvironmentalLab


Methods(experimentaldesign) • 500mLcultureboLleswith400mLworkingvolumefor10days

• Metalcapwithtwostainlesssteelfiongsandrubberwasher

• Biogascircula)onfromaTedlarbagtoculturesolu)on,forcedbya

peristal)cpump(10mL/min)

• 30oCand24hrillumina)onatroughly3,000Lux

Schema)cdiagramformicroalgaecul)va)on


Cul)va)onApparatus


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


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)


• Specificgrowthrate(μ)(unit:day-1)

ü T1andT2bothhadthehighestμat

day4-5

ü T1μ(0.53d-1)

ü T2μ(0.35d-1)


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 T6hadthehighestμatday1-2

ü T6μ(0.55d-1)

• Resultsshowashorthyper-growthperiod,

indica)ngincreasedheterotrophic

metabolismofmicroalgaeinSTSC


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 T4hadthehighestμatday1-2(0.59

d-1)

ü T5hadthehighestμatday4-5(0.45

d-1)

• Resultsshowamaximumbiosynthe)crate

governedbymixotrophicmetabolism


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


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


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.


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)


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).


Conclusion

• Biogasandsep)ctanksludgecentratecancausemicroalgaetoshi{tomixotrophic

metabolism,andsignificantlyincreasebiomassproduc)on

• Biogascontainshighconcentra)onofCO2,canbufferthepHofculturesolu)onand

preventammoniavola)liza)onandphosphateprecipita)on

• Phosphateisthelimi)ngnutrientinthiscul)va)onsystem,anditsconcentra)on

canbeusedtopredictthemicroalgaegrowth

• Nutrientdeficientcondi)oncancausethemicroalgaetoaccumulatemorelipid


Acknowledgements

• TheauthorswouldliketoacknowledgethefundingsupportfromtheUniversityof

MassachuseLsLowell(UML).

• TheauthorsthankProf.MarkHinesfromtheBiologicalSciencesDepartment

assistanceinthebiogasanalyses.

• TheauthorswouldalsoliketothankthestaffattheLowellRegionalWastewater

U)lityforassistanceinobtainingsep)csludgeandclarifiersupernatant.


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Effects of Biogas and Septic Tank Sludge Centrate on Microalgae … · 2017. 10. 17. · Learning...

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