ANAEROBIC DIGESTION OF OLIVE MILL WASTEWATER ...

Departamento de Energias Renováveis Anaerobic digestion of OMW: Department of Renewable Energy anaerobic filter vs. hybrid LNEG – Laboratório Nacional de Energia e Geologia National Laboratory of Energy and Geology

Anaerobic digestion of Olive Mill Wastewater: Anaerobic Filter vs. Hybrid Isabel Paula Marques [email protected]

Marta Gonçalves and Paulo Freitas

Bioenergy – II: Fuels and Chemicals from Renewable Resources 8-13 March 2009, Rio de Janeiro. Brasil

Anaerobic digestion of OMW: anaerobic filter vs. hybrid



IPaula

Silvio Tanaka

Olive tree

olives (fruit)

olive oil



Olive oil industry Great economic and social importance: Mediterranean area [Olives are also cultivated: USA, Argentina, Australia and South Africa]

olives (fruit)

olive oil Olive Mill Wastewater 5 kg olives (OMW)

5 L OMW

1 L olive oil



OMW [three-phase extraction system]



OMW • generated in huge quantities • during a short period of the year • one of the most polluting agro-industrial effluents

OMW holds a great energetic potential (Biogas)



Anaerobic digestion - OMW promising attempt to face the negative environmental impact

• • • • •

high organic matter of these effluent (200 kg COD m-3) lower: sludge volumes, space requirement and capital cost - aerobic proc., easily restarting after several mouths of shutdown, low energy requirement for operation, recovering the valuable end-product --- methane



Olive Mill Wastewater - OMW • inhibiting substances (phenolic lipidic-LCFA) • unfavourable C/N ratio • acid pH render

OMW inappropriate direct biological treatment



Reduce concentration and toxicity Olive Mill Wastewater

high dilutions physic

chemical addition of alkalis biological pre-treatments



OBJECTIVE: treat and recover the energetic potential of the raw OMW anaerobic digestion Successful digesting stability is obtained

“complementary substrate” concept Depart. of Renewable Energies - LNEG • without any pre-treatment • tap water dilution • chemical correction of OMW



OMW: composition + seasonal effluent

Another effluent:

continuously produced - same region + able to complement OMW

Piggery effluent

to secure a stable operation year-around



CQO

C/N

(kg/m3)

Olive oil

OMW

Swine

Piggery effluent

NH4+

pH

(kg/m3)

50 200

high

low

4-5

< 30

low

high

≈7-8



Olive Mill Wastewater

dilute and to supplement (N, P) Piggery effluent

+ • decrease - inhibiting capacity • more favourable C/N ratio • pH values



OBJECTIVE: Anaerobic Filter vs. Hybrid

g as

g as

ef

ef

inf . UASB

inf

inf

.

Hybrid

Anaerobic filter

Fixe bed



Operational difficulties gas

ef

inf .

inf.

UASB

Washout – overload concentrated effluents

Anaerobic filter

[concentrated effluents] Channelling - Column clogging

Packing bed material – Lab. AF classic problems



Packing bed material – Lab.

good progress

several long-term experiments

no troubles as a result of a clogging process



OBJECTIVE: Anaerobic Filter vs. Hybrid

g as

g as

ef

inf

ef

inf

economic issue: least of packing material required

.

Hybrid

Anaerobic filter

Fixe bed



packing material = 30% reactor height Bioenergy – II: Fuels and Chemicals from Renewable Resources 8-13 March 2009, Rio de Janeiro. Brasil


Operational conditions Anaerobic Filter vs. Hybrid

60

53

53 41

OMW (% v/v)

40

27 20

8 0 0

40

80

120

160

200

240

280

320

Time (d) OMW.H

OMW.AF



Operational conditions Hybrid

La (kgCOD m-3)

10 8 6 4 2 0 110

130

La (in)

150

La (OMW)

Time (d)

190

210

AF

10

La (kgCOD m-3)

170

8 6 4 2 0 200

220

La (in)

La (OMW)

240

260

280

300

320

Time (d)



Results Gas 80 70 60

3

50 2

40 30

1

CH4 (%)

Biogas (m3 m m-3 d-1)

4

20 10

0

0 2

3

Biog-FA

Biog-H

4

CH4-FA

5

CH4-H

6

7

8

Loading rate, La (kg m3 d-1)

Gradual increase of biogas production – increment LA Good methane content



Results 90 80 70 60 50 40 30 20 10 0

90 80 70 60 50 40 30 20 10 0 2

CODt Inf. FA

3

4

CODt Inf. H

5

CODtr FA

6

7

CODr (%)

Influent (kg COD m-3)

COD removal: 27-41% OMW v/v

8

La in (kg m3 d-1)

CODtr H

AF ≠ H = COD removal



Results. Solids removal: 27-41% OMW v/v AF

H

TS (%)

51-63

22-50

VS (%)

60-76

41-67

VSS (%)

66/80-96

5/55-69

Some comments are needed to better understand the finding



Operational conditions Anaerobic Filter vs. Hybrid

60

OMW

(% v/v)

40

20

0 0

40

80

120

H overload OMW.H

160

200

240

280

320

Time (d)

OMW.AF



Sharp change in sludge bed The blanket of biologic solids went upwards and penetrated the fixed bed section Some biomass was lost - not cause the failure

[18% OMW] La = 5.3-9.5 kg COD m-3 d-1 (31-55 kg COD m-3)

Gas - 1.3-2.1m3 m-3 d-1 COD removal - 57-65/69%



ability of resisting

H - overloading was tested - new influent

previous plan of work (27% OMW v/v)



Operational conditions 60

OMW (% v/v)

40

20

0 0

40

80

120

160

200

240

280

320

Time (d) OMW.H

OMW.AF



90

90

80

80

70

70

60

60

50

50

40

40

30

30

20

20

10

10

0

0 2

3

4

5

6

7

CODr (%)

Influent (kg COD m m-3)

COD removal: + 53% OMW v/v

8

La (kg m3 d-1) Inf-FA

Inf-H

CODr-FA

CODr-H

≠ digesters behaviour = AF ↓ . H↑ Bioenergy – II: Fuels and Chemicals from Renewable Resources 8-13 March 2009, Rio de Janeiro. Brasil


RESULTS H digester: remaining packing material - 1/3 height

Effective effects - accidental overload

The maintenance of a sufficient amount of biomass inside the unit allowed preventing the process failure



100

8

80

6

60

4

40

2

20

0

0 2

3

4

5

6

7

VFA rem (%)

VFA inf. (kg m-3)

VFA removal 10

8

La (kg m3 d-1) VFAin FA

VFAin H

VFAr FA

VFAr H

Hybrid: VFA = ≈ 4 times more concentrated



Conclusions Anaerobic filter and hybrid: can be used to treat the raw OMW (without any pre-treatment or chemical correction)

AF ≠ H (27 and 41% OMW v/v) = COD and solids removal AF=69-83% vs. H=60-73% [overload (18% OMW v/v)]

H recovery process → packed bed material was effective in preventing the excessive loss of biomass

Confirmation → better performance of H than AF (53% OMW v/v) [COD removal: AF = 80 → 70%, H = 73-78%]



Conclusions Anaerobic Filter vs. Hybrid Important issue related to the applicability of the Hybrid

Anaerobic digestion of Olive Mill Wastewater is the lower costs related to the amount of packing material



Acknowledgements

financial support project PTDC/ENR/69755/2006 and the grant given to Marta Gonçalves SFRH/BD/40746/2007.


Departamento de Energias Renováveis Anaerobic digestion of OMW: Department of Renewable Energy anaerobic filter vs. hybrid LNEG – Laboratório Nacional de Energia e Geologia National Laboratory of Energy and Geology

Anaerobic digestion of Olive Mill Wastewater: Anaerobic Filter vs. Hybrid

Isabel Paula Marques [email protected]

Marta Gonçalves, Paulo Freitas

Thanks for your attention Bioenergy – II: Fuels and Chemicals from Renewable Resources 8-13 March 2009, Rio de Janeiro. Brasil