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

Learning with Purpose Learning with Purpose

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 with Purpose Effects of Biogas and Septic Tank Sludge Centrate on Microalgae Cultivation