carbon and nutrient scavenging from sewage and flue gas with mab-flocs

8/6/2019 Carbon and Nutrient Scavenging From Sewage and Flue Gas With MaB-Flocs

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Carbon and nutrient scavenging

from sewage and flue gaswith MaB-flocs

Sofie Van Den Hende, Sem Desmet, Han Vervaeren, Nico Boon

Brussels, 22 October 2010

AquaFUELs Roundtable Meeting

Enbichem, University College West-Flanders, Kortrijk, Belgium

LabMET, Ghent University, Ghent, Belgium

1Enbichem


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Micro-algae for biofuel production

Micro-algae for biofuel production

seem promising

Publications greatly outnumber theindustrial implementations

Not yet economically viable causemicroalgal biomass is expensive

2

Google: 883 000 resultsScience Direct: 505 publications

In Europe: ?

Industrial implementationsMicro-algae + biofuel

Written documentsMicro-algae + biofuel


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Micro-algal biomass production at lower cost

Main costs

Carbon

Water and nutrients (N, P)

Harvesting: up to 50 %

(Richmond, 2004)

3

Flue gas

Sewage

Bio-flocculation


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Bio-flocculation offers advantagescompared to micro-algae cultures

Micro-algal Bacterial flocs

MaB-flocs

Microalgae and bacteria(Van Den Hende et al, 2010)

Micro-algae difficult to harvest

MaB-flocs settle by gravity

Interaction CO2 and O2

4

50m

CO2

O2

Bacteria

Microalgae

Organic

carbon


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Addition of flue gas in sewage fed reactors

Sewage as a cheap H2O, C, N, P source

Sewage C:N = 3-7 vs micro-algae C:N = 6-15(Benemann, 2003; van Harmelen and Oonk, 2006)

+ Micro-algae increase pH

-> ammonium volatilization

-> non optimal pH formicro-organisms

5

+ Flue gas

Provide extra C

to adjust C:N ratio

Provide CO2,

NOx, SO2

to avoid high pH

MicrobialResourceManagementforacheapermicroalgalbiomassproduction


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Therefore we investigated...

...theproductionofaquaticbiomass:

MicroalgalBacterialflocs=MaBflocs

combined

with

the

polishingofprimarytreatedsewage

andfluegas

inalabscalephotobioreactor

6

+

+

=


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Influent

Primary treated sewage

MWWTP Aquafin, Harelbeke

Flue gas

Model flue gascoal power plant

(Xu et al, 2004)

12 % CO2300 ppmv NO

200 ppmv SO2

0.6 L gas h-1 -> 0.0025 vvm

7

Cheap resources

Sedimentationandflotationtank


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Labscale reactor

Air bubble photobioreactor

Circulation pump: counter flow4 L working volume

Sequencing Batch Reactor

HRT= 0.67 days

PFD ~ 100 mol PAR m-2 s-1

MaB-flocs

Local micro-algae strains

Activated sludge(Van Den Hende et al, 2010)

1 g VSS L-1

Withdraw

0.5h

Fill

+react

0.5h

8

Settle

0.5h

React

6.5h

MaB-floc reactor


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Analysis

Wastewater and effluent

TIC, TOC, N, P, S

Turbidity, pH

Flue gas and off gas

CO2, NO, NO2, SO2, O2T, P

MaB-flocs

Productivity of VSSSludge volume index SVI

Chlorophyll a, Pheophytine a

Physiological condition: A664/A665a

Autotrophic index AI(APHA, 1985)

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Experimentalsetup

10

Experiment Influent Gasflow

rate

(Lh1)

Biomass Time

(days)

MaB

CONTROLS

Sewage 0.6 MaBflocs 32

NoGas Sewage 0.0 MaBflocs 13

NoMaB Sewage 0.6 / 19

RH2

O Deionised

water

0.6 / 4


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Results

MaB-flocs

Sewage treatmentC, N, P and turbidity removal

Flue gas treatmentCO2, NOx & SO2 removal

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MaB-flocs

Sewage treatmentC, N, P, pH and turbidity

Flue gas treatmentCO2, NOx & SO2


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Results

MaB-flocs



12

MaB-flocs




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MaB-floc quality

Fast settling flocsAverage SVIMaB: 57 ml g-1 TSS

NoGas: 111 ml g-1 TSS

Good incorporationof micro-algae

19 3 mg Chlorophyll a g-1 VSS

No significant decreaseof the physiological condition

by adding flue gasA664/A665a between 1.0 and 1.7Pheophytine a vs Chlorophyll aMaB 1.54 0.06

vs NoGas 1.58 0.02

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Chlorellasp.

Bacteria Phormidium

sp.

50m


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MaB-floc quantity

Biomass productivity0.05 - 0.19 g Lreactor

-1 day-1

Lipid concentration

12 % of DW (first results E. Ryckebosh)

Extrapolate to industrial scale

Correction factor to extrapolate to open pond system: 0.19

80 % of a year operational

-> Max. 60 ton microalgal bacterial biomass ha-1 year-1

(Max. 7 ton lipids ha-1 year-1)

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Results

MaB-flocs



15

MaB-flocs




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A good effluent quality

Discharge standardsfor a Flemish MWTP

are feasible

Average values

> 100.000 PE

10 mg TN L-1

1 mg TP L-1

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NO2

N NO3

NNH4+N

N

PO43

PO43

MaB


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An adequate N and P removal

Very high NH4+ removal efficiency

94 6 %

Daily nitrogen removal

27.1 4.1 mg N L-1 day-1

PO43- removal efficiency was significantly higher

w ith a higher HRT

67 13 % if HRT = 0.67 days vs 99 2 % if HRT=1.33

days

Daily PO43- removal

2.3 0.9 mg P-PO43- L-1 day-1

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A good turbidity removal

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28 times lower turbidity of sewagein MaB-floc reactor

Influent: 44.2 15.3 FTUEffluent: 1.6 0.6 FTU

MaB MaB


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A neutral pH was maintained

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With sewage the pH stabilizedaround 6.7

(MaB-reactor)

With deionised water the pHdecreased to 4.5 (RH20)

Buffering capacity of sewageand micro-algal growth


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Results

MaB-flocs



20

MaB-flocs




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A good off gas quality

High removal efficiencies

49 % CO288 % NOx99 % SO2

Sewage reinforced

removal of NO

Off gas concentrationslower than Flemishdischarge standardsDaily averages for a CPP,

Ruien, Electrabel

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CO2 SO2O2 NO2NO

NOx

SO2

Component

Conc

entrationNO,

NO2orSO2

(m

g/Nm)

MaB


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Extrapolation to industrial scale

Large pond area needed for flue gas treatment

Correction factor for extrapolation to an open pond system: 0.19

80 % of a year operational

Min. 2000 ha for 50 % reduction of CO2 of a 50 MW plant

CO2 credits

1775 ha-1

year-1

(15.30 ton-1

CO2)

NOx credits

Only some countries (100 ton-1 NOx Netherlands), not yet in Belgium

Flue gas is cheap carbon source algae,

algae not a treatment for all industrial flue gas

22

C l i


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Good productivity of MaB-flocs combined w ith a

successful treatment of sewage and flue gas

Bottlenecks still exist

Large areas are needed

How to valorise this biomass in the most sustainable way?

Only data on lab scale

Future research should include

Valorisation of the aquatic biomassImplementation on pilot scale (light/dark cycle)

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Conclusions


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Thankyou

foryourattention [email protected]

labmet.ugent.be www.howest.be

Enbichem

Di h f ff d f O


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Discharge norms for off gas and reference O2

A correction for off gas concentrations isneeded before comparing to norms

To avoid diluting off gas

This O2 reference depends on fuel

and installation

Diesel: 3 % - coal: 6 % - biomass: 11 %

In algal technology O2 is produced (+6 %)

-> Om > Or -> Er > Em

This makes discharge norms more stringentfor oxygen producing gas treatment

Policy makers -> Adjustment needed

25

Er

= (21Or

). Em

(21Om

)

Or

:referenceO2concentration(%)

Om

:measuredO2concentration(%)

Em :measuredconcentration(mg/Nm)

Er :correctedconcentration(mg/Nm)

carbon and nutrient scavenging from sewage and flue gas with mab-flocs

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