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Sustainable Water-Energy-Centric Communities
Como, 12 May 2016
Chapter 1:
definitions and main characteristics
Basics of oxidation and reduction reactions
2
Each half-reaction has a sta...
In a wastewater treatment plant …
3
OM oxidation (by heterotrophs):
CH3COOH + 2 O2 2 CO2 + 2 H2O
Nitrification (by autotro...
Microbial Electrochemical
Technology (MET)
Chapter 1:
definitions and main characteristics
The Microbial Electrochemical T...
Why to study METs?
• Energy hungry WWTPs, GHG emissions
• Sustainable and flexible technology, wide range of applications
...
6
(Rabaey & Rozendal, 2010)
Working principle of METs
ANODE
CATHODE
The aim is to separate OX and
RED reactions in 2 diffe...
Differences / similarities between MFCs and MECs
7
MFCs MECs
Similarities: oxidation at the anode (AN), reduction at the c...
8
Architecture of METs
Exoelectrogenic
bacteria (anode)
Electrotroph
bacteria (cathode)
CO2 CO2 H2OH2O
(O2)
Dual-chamber M...
9
Materials for METs construction
Ideal electrode
• Highly conductive
• Stable (no sacrificial electrode)
• Biocompatibile...
10
Urban wastewater
Agricultural waste,
e.g. swine manure
What’s the (anode) fuel in METs?
Microbial
FUEL Cell
Food proces...
In a WWTP In a MFC
• Biological catalysts (of ox and red)
• Solid electrode in place of usual TEAs
• Extracellular Electro...
Parameters
OCV (Open Circuit Voltage)
Iscc (Short Circuit Current)
Rint (Internal Resistance)
MPP (Maximum Power Point)
De...
METs applications in Ecocities ?
13
(Cha et al., 2010)
Urban wastewater treatment by MFCs
(Martinucci et al., 2015)
COD re...
METs applications in Ecocities ?
14
(Kelly & He, 2014)
Industrial wastewater treatment by MFCs
COD removal > 90% depending...
METs applications in Ecocities ?
Human waste treatment (MFC latrine)
(Castro et al., 2014) 15
METs applications in Ecocities ?
Human waste treatment (MFC latrine)
(Castro et al., 2014)
COD removal > 90%
Power density...
17
METs applications in Ecocities ?
http://imetland.eu/
Microbial Electrochemical Wetlands (METlands)
Principle: vertical ...
18
METs applications in Ecocities ?
H2 production from domestic wastewater by MECs
(Heidrich et al., 2013)
Principle: cass...
METs applications in Ecocities ?
Bioelectrically enhanced CH4 production by MES
19
Principle: electromethanogenesis, i.e. ...
Laboratory MFC experience
20
The European pigs production according to the European Union
(EUROSTAT, 2010)
47 mln m3 swine manure · year-1
5 L swine ma...
Parameter Value Units
Organic matter
CODtotal 2200 mg O2·L-1
BOD5 1300 mg O2·L-1
Alkalinity Alk 4700 mg CaCO3·L-1
Kjeldahl...
Solid and liquid Fertiliser
Gas Biogas
Anaerobic digestion
Swine manure state of decomposition
and heterogeneity
Presenc...
N2
NO3
- NH4
+
IONICEXCHANGEMEMBRANE
EFFLUENT
V
INFLUENT INFLUENT
EFFLUENT
Organic
matter
CO2
Biofilm Biofilm
ANODE CATHOD...
Anode
effluent
NH4
+
MFC-1 MFC-2
Based on Virdis et al., 2010
Anode effluent
NH4
+
Cathode
effluent
Swine manure
COD and N...
e-
CO2
NO3
-
N2CO2
Organic
matter
ANIONICEXCHANGEMEMBRANE
N2
NH4
+
NO3
-
Externalreactor
Anode Cathode
Recirculation
Recir...
e-
CO2
NO3
-
N2CO2
Organic
matter
ANIONICEXCHANGEMEMBRANE
N2
NH4
+
NO3
-
Externalreactor
Anode Cathode
Recirculation
Recir...
e-
CO2
NO3
-
N2CO2
Organic
matter
ANIONICEXCHANGEMEMBRANE
N2
NH4
+
NO3
-
Externalreactor
Anode Cathode
Recirculation
Recir...
e-CO2
NO3
-
N2
CO2
Organic
matter
CATIONICEXCHANGEMEMBRANE
N2
Recirculation
O2
NH4
+
NO3
-
Anode Cathode
Recirculation
H+
...
e-CO2
NO3
-
N2
CO2
Organic
matter
CATIONICEXCHANGEMEMBRANE
N2
Recirculation
O2
NH4
+
NO3
-
Anode Cathode
Recirculation
H+
...
Anode effluent
NH4
+
Flow = 3.0 L·d-1
80% of biodegradable organic
matter was removed
Swine manure
COD and NH4
+
e-CO2
NO3...
MFCs performance
Microbial community
Comments and open issues
 The study confirms that MFCs successfully treat swine manu...
How to enhance MFCs electric production?
e-
Organics
CO2
Electrode
Electron discharge
capability
Electron flow
Microbial
c...
34
max
𝑅 𝑒𝑥𝑡
𝑃 = max
𝑅 𝑒𝑥𝑡
𝐸2
𝑅 𝑒𝑥𝑡
Maximum Power Point Tracking (MPPT)
(Premier et al., 2011)
MPP se Rext = Rint
MPPT met...
• Visual Basic software
• 5 potentiometers connected in parallel,
as variable Rext (range 6-200 Ω, ΔR 2 Ω)
• 2 multimeters...
36
Replicate MFCs construction
Ref-MFC
(Rext = 30 Ω, fixed)
MPPT-MFC
(Rext = Rint, variable)
Days
1 - 4
• MFCs inoculation
• Rext of 30 Ω
Days
4 - 53
• FIRST PERIOD
• OLR of 10.5±0.7 kg COD m-3 d-1
• MPPT switched o...
Second periodFirst period
MPPT-MFC
time (days)
0 7 14 21 28 35 42 49 56 63 70 77
P(mW)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Rex...
Second periodFirst period
MPPT-MFC
time (days)
0 7 14 21 28 35 42 49 56 63 70 77
P(mW)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Rex...
Comments:
• Only electrical current and Coulombic efficiency are significantly different (*)
• Coulombic efficiency increa...
How to outcompete methanogens?
Days
88 - 103
• THIRD PERIOD (only for MPPT-MFC)
• OLR of 0.7±0.1 kg COD m-3 d-1
OPEN
CIRCU...
MFC Period
OLR
(kg COD m-3 d-1)
COD rem.
(%)
Imean
(mA)
Pmean
(mW)
CECODs
(%)
CEBODt
(%)
MPPT First 10.5 ± 0.7 39 ± 16 14....
43
Anode gas effluent analysis
time interval (days)
14-49 50-52 53-78 79-81 88-100
Gasproductionrate(mLd-1)
0
100
200
300
...
Several multiphysics phenomena:
• Swine manure characterization
• Treatment by Microbial Fuel Cells
• Organic matter oxida...
Several multiphysics phenomena:
• Swine manure characterization
• Treatment by Microbial Fuel Cells
• Organic matter oxida...
Several multiphysics phenomena:
• Swine manure characterization
• Treatment by Microbial Fuel Cells
• Organic matter oxida...
There are several modelling “levels” in Microbial Fuel Cells research:
Can we model all this?
47
(Picioreanu et al., 2008)...
An introduction to biochemical models
Activated Sludge Model (ASM) = IWA model framework for AS plants treating wastewater...
2-populations MFC model
Model components (Pinto et al., 2010)
Anaerobic MFC anode chamber is
populated by 2 microbial comm...
Wastewater characterization
50
Inert particulate
material (Xi)
Slowly biodegradable
organics (Xs)
Inert soluble material
(...
Integration of MFC model with ASM2d
51
Pinto’s model considers only the presence of anodophils (Xa) and methanogens (Xm)
B...
Integration of MFC model with ASM2d
52
53
A closer look to microbial dynamics
54
Influent wastewater characterization Microbial populations
Current production Metha...
Sustainable Water-Energy-Centric Communities
Como, 12 May 2016
Dr. Daniele Molognoni, PhD
University of Pavia, Italy
Dept....
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Lectures Capodaglio - Molognoni

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Sustainable Water - Energy - Centric Communities school
May 9 - 13, 2016 – Lake Como School of Advanced Studies

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Lectures Capodaglio - Molognoni

  1. 1. Sustainable Water-Energy-Centric Communities Como, 12 May 2016
  2. 2. Chapter 1: definitions and main characteristics Basics of oxidation and reduction reactions 2 Each half-reaction has a standard electrode potential (E0) evaluated at standard conditions (25°C, 1 M, 1 bar). E0 cell = E0 Cu2+/Cu – E0 Zn2+/Zn = E0 cathode – E0 anode = electromotive force (Eemf)
  3. 3. In a wastewater treatment plant … 3 OM oxidation (by heterotrophs): CH3COOH + 2 O2 2 CO2 + 2 H2O Nitrification (by autotrophs): NH4 + + 3/2 O2  NO2 - + H2O + 2H+ NO2 - + 1/2 O2  NO3 - Denitrification (by heterotrophs): NO3 -  NO2 -  NO  N2O  N2 WW intrinsic energy content of 4.4 kWh kg-COD-1 oxidised (Owen, 1982) equal to about 10x the energy needed by aerobic WWT (Shizas & Bagley, 2004) 7500 GWh yr-1 of EE consumption in developed countries are used for WWT Can we exploit oxidation and reduction half-processes to harvest energy?
  4. 4. Microbial Electrochemical Technology (MET) Chapter 1: definitions and main characteristics The Microbial Electrochemical Technologies 4
  5. 5. Why to study METs? • Energy hungry WWTPs, GHG emissions • Sustainable and flexible technology, wide range of applications • Upgrading of existing WWTPs to novel biotechnological factories Microbial Electrochemical Technology (MET) Microbial Fuel Cell (MFC) Microbial Electrolysis Cell (MEC) • Electrical energy harvesting • Mineralization of wastewaters OM • Spontaneous process (ΔE0 < 0) • Energy consumption • Production of valuable energy vectors (H2) or nutrients removal • Non-spontaneous process (ΔE0 > 0) Europe2020Chapter 1: definitions and main characteristics The Microbial Electrochemical Technologies 5 Microbial ElectroSynthesis (MES)
  6. 6. 6 (Rabaey & Rozendal, 2010) Working principle of METs ANODE CATHODE The aim is to separate OX and RED reactions in 2 different MET compartments. Example:  COD oxidation at the anode  O2 reduction at the cathode • E0 (V vs SHE) are tabulated • E0’ (V vs SHE) by Nernst eq. Eemf = E0’cat – E0’an = 1.1 V (MFC) Eemf = E0’cat – E0’an = -1.1 V (MEC)
  7. 7. Differences / similarities between MFCs and MECs 7 MFCs MECs Similarities: oxidation at the anode (AN), reduction at the cathode (CAT) electrons and cations from AN to CAT, anions from CAT to AN Differences: in MFCs’ electric circuit there is a load, in MECs a power source in MFCs Ecat > Ean, while in MECs Ean > Ecat
  8. 8. 8 Architecture of METs Exoelectrogenic bacteria (anode) Electrotroph bacteria (cathode) CO2 CO2 H2OH2O (O2) Dual-chamber MFC Single-chamber MFC Three-chamber MDC (Zhang & He, 2012)
  9. 9. 9 Materials for METs construction Ideal electrode • Highly conductive • Stable (no sacrificial electrode) • Biocompatibile • High specific surface (Wei et al., 2011) Ideal membrane • Separation of anode and cathode • Selective permeability (H+) • Low internal resistance • Cheap, mechanically strong PEM CEM AEM
  10. 10. 10 Urban wastewater Agricultural waste, e.g. swine manure What’s the (anode) fuel in METs? Microbial FUEL Cell Food processing wastewater Industrial wastewater Landfill leachate
  11. 11. In a WWTP In a MFC • Biological catalysts (of ox and red) • Solid electrode in place of usual TEAs • Extracellular Electron Transfer (EET) What’s the engine of METs? 11 Electro-Active Bacteria (EAB): • Exoelectrogens (AN) • Electrotrophs (CAT)
  12. 12. Parameters OCV (Open Circuit Voltage) Iscc (Short Circuit Current) Rint (Internal Resistance) MPP (Maximum Power Point) Developed techniques Electrochemical characterization of METs Polarization curve and power curve (for MFCs) OCV MPP Rint Iscc Others (CV, EIS) for MECs V (Rabaey et al., 2005) 12
  13. 13. METs applications in Ecocities ? 13 (Cha et al., 2010) Urban wastewater treatment by MFCs (Martinucci et al., 2015) COD removal = 70–80% depending on OLR Power density = 1–6 W m-3 Drawbacks: low electric conductivity low soluble COD concentration Milan WWTP
  14. 14. METs applications in Ecocities ? 14 (Kelly & He, 2014) Industrial wastewater treatment by MFCs COD removal > 90% depending on OLR Power density = 27 W m-3 Advantages: BOD/COD ≈ 1 Drawbacks: pH can be slightly acid A lab-MFC experiment is currently proceeding at University of Pavia, treating DAF effluent of a local cheese factory.
  15. 15. METs applications in Ecocities ? Human waste treatment (MFC latrine) (Castro et al., 2014) 15
  16. 16. METs applications in Ecocities ? Human waste treatment (MFC latrine) (Castro et al., 2014) COD removal > 90% Power density = 0.2 mW m-3 Advantages: COD + N treatment, recovery of compost Drawbacks: very poor EE recovery Agona Nyakrom, Ghana 16
  17. 17. 17 METs applications in Ecocities ? http://imetland.eu/ Microbial Electrochemical Wetlands (METlands) Principle: vertical flow wetland with internal redox gradient electrochemical control to enhance treatment rate COD removal = 95% with raw urban wastewater Advantages: small communities, zero energy Drawbacks: ecological footprint
  18. 18. 18 METs applications in Ecocities ? H2 production from domestic wastewater by MECs (Heidrich et al., 2013) Principle: cassette-type MEC modules powered at 1.1 V Newcastle, UK COD removal = 34% H2 recovery (pure gas) = 15 mL-H2 L-1 d-1 Energy efficiency = 70% Advantages: lower energetic cost than AS pilot-scale reactor (120 L) Drawbacks: not self-sustainable low COD removal
  19. 19. METs applications in Ecocities ? Bioelectrically enhanced CH4 production by MES 19 Principle: electromethanogenesis, i.e. conversion of CO2 (from OM oxidation) to CH4 an external electric power supply drives the reaction COD removal = 80-90% with production of high quality biogas (> 80% CH4) Advantages: containerized, modular, stackable Drawbacks: technology not (yet) self-sustainable
  20. 20. Laboratory MFC experience 20
  21. 21. The European pigs production according to the European Union (EUROSTAT, 2010) 47 mln m3 swine manure · year-1 5 L swine manure · day-1 Swine manure production Germany 24% Spain 16% France 9% Poland 8% Denmark 8% Italy 7% Holand 6% Belgium 5% United Kingdom 3% Others 14% 21 mln m3 swine manure · year-1 Why swine manure is a problem? 21
  22. 22. Parameter Value Units Organic matter CODtotal 2200 mg O2·L-1 BOD5 1300 mg O2·L-1 Alkalinity Alk 4700 mg CaCO3·L-1 Kjeldahl Nitrogen TKN 650 mg N-TKN·L-1 Ammonium NH4 + 550 mg N-NH4 +·L-1 Nitrite and nitrate NOx - 0 mg N-NOx -·L-1 Suspended solids TSS 400 mg SST ·L-1 Conductivity 8.6 mS cm-1 60% of COD is biodegradable C/N of 2 High conductivity Swine manure characteristics If swine manure is not properly disposed:  Eutrophication of surface water bodies  Groundwater contamination  Toxic microorganisms proliferation Experimental data from IRTA (Monells, Girona, Spain) 22
  23. 23. Solid and liquid Fertiliser Gas Biogas Anaerobic digestion Swine manure state of decomposition and heterogeneity Presence of inhibitory substances (Cu, Zn, antibiotics and disinfectants) Does not remove nitrogen Need for subsequent treatments Cost of digestate disposal Anaerobic digestion problems: Traditional use/treatment of swine manure Agriculture Soil discharge Fertiliser RD 324/2000 and 3483/2000 D.Lgs 152/2006 part III and D.M. 07/04/2006 Previously encouraged by national legislations 23
  24. 24. N2 NO3 - NH4 + IONICEXCHANGEMEMBRANE EFFLUENT V INFLUENT INFLUENT EFFLUENT Organic matter CO2 Biofilm Biofilm ANODE CATHODE Microbial fuel cells e- Organic matter treatment Nitrogen treatment O2 Alternative swine manure treatment 24
  25. 25. Anode effluent NH4 + MFC-1 MFC-2 Based on Virdis et al., 2010 Anode effluent NH4 + Cathode effluent Swine manure COD and NH4 + Reactor effluent NO3 - Swine manure COD and NH4 + Cathode effluent Based on Virdis et al., 2008 MFC configurations 25
  26. 26. e- CO2 NO3 - N2CO2 Organic matter ANIONICEXCHANGEMEMBRANE N2 NH4 + NO3 - Externalreactor Anode Cathode Recirculation Recirculation Recirculation 3.2 mg O2 L-1 MFC-1 80% of biodegradable organic matter is removed CE of 24% Electrochemical characterization Swine manure COD and NH4 + Flow = 3.0 L·d-1 26
  27. 27. e- CO2 NO3 - N2CO2 Organic matter ANIONICEXCHANGEMEMBRANE N2 NH4 + NO3 - Externalreactor Anode Cathode Recirculation Recirculation Recirculation 3.2 mg O2 L-1 80% of biodegradable organic matter was removed 95% of ammonium is nitrified Electrochemical characterization Anode effluent NH4 + Swine manure COD and NH4 + Flow = 3.0 L·d-1 MFC-1 27
  28. 28. e- CO2 NO3 - N2CO2 Organic matter ANIONICEXCHANGEMEMBRANE N2 NH4 + NO3 - Externalreactor Anode Cathode Recirculation Recirculation Recirculation 3.2 mg O2 L-1 95% of ammonium was nitrified Anode effluent NH4 + 80% of biodegradable organic matter was removed Swine manure COD and NH4 + Flow = 3.0 L·d-1 Reactor effluent NO3 - 7% of nitrogen is removed Cathode effluent 2.5 mWof power production Electron acceptor competition Oxygen intrusion CE of 10% Electrochemical characterization MFC-1 28
  29. 29. e-CO2 NO3 - N2 CO2 Organic matter CATIONICEXCHANGEMEMBRANE N2 Recirculation O2 NH4 + NO3 - Anode Cathode Recirculation H+ H+ 1.3 mg O2 L-1 MFC-2 Swine manure COD and NH4 + 80% of biodegradable organic matter is removed Flow = 3.0 L·d-1 CE of 5% Electrochemical characterization 29
  30. 30. e-CO2 NO3 - N2 CO2 Organic matter CATIONICEXCHANGEMEMBRANE N2 Recirculation O2 NH4 + NO3 - Anode Cathode Recirculation H+ H+ 1.3 mg O2 L-1 80% of biodegradable organic matter was removed 50% of ammonium is nitrified Swine manure COD and NH4 + e-CO2 NO3 - N2 CO2 Organic matter CATIONICEXCHANGEMEMBRANE N2 Recirculation O2 NH4 + NO3 - Anode Cathode Recirculation H+ H+ 1.3 mg O2 L-1 e-CO2 NO3 - N2 CO2 Organic matter CATIONICEXCHANGEMEMBRANE N2 Recirculation O2 NH4 + NO3 - Anode Cathode Recirculation H+ H+ 1.3 mg O2 L-1 Flow = 3.0 L·d-1 Electrochemical characterization MFC-2 Anode effluent NH4 + 30
  31. 31. Anode effluent NH4 + Flow = 3.0 L·d-1 80% of biodegradable organic matter was removed Swine manure COD and NH4 + e-CO2 NO3 - N2 CO2 Organic matter CATIONICEXCHANGEMEMBRANE N2 Recirculation O2 NH4 + NO3 - Anode Cathode Recirculation H+ H+ 1.3 mg O2 L-1 50% of ammonium was nitrified 22% of nitrogen is removed 0.25 mW of power production Electrochemical characterization MFC-2 31 Low oxygen concentration Heterotrophic denitrification
  32. 32. MFCs performance Microbial community Comments and open issues  The study confirms that MFCs successfully treat swine manure.  Anodes show similar organic removal rates with low CE.  MFC-1 system produces ten times more electricity than MFC-2.  In the anode microbiome C. disporicum is related to swine manure and G. sulfurreducens is involved in current production.  Different nitrification rates are linked to diverse AOB microbial composition. (Nitrosomonas europaea nitrifies faster than Nitrosospira sp.)  Similar denitrification rates are linked to similar microbial community (Bacteroidetes, Chloroflexiaceae and Proteobacteria). 32 * Vilajeliu-Pons et al. (2015). Microbiome characterisation of MFCs used for the treatment of swine manure. Journal of Hazardous Materials, 288, 60–68.
  33. 33. How to enhance MFCs electric production? e- Organics CO2 Electrode Electron discharge capability Electron flow Microbial community External resistance control Microbial Fuel Cell (MFC) 33
  34. 34. 34 max 𝑅 𝑒𝑥𝑡 𝑃 = max 𝑅 𝑒𝑥𝑡 𝐸2 𝑅 𝑒𝑥𝑡 Maximum Power Point Tracking (MPPT) (Premier et al., 2011) MPP se Rext = Rint MPPT methods Perturbation Observation (P/O) Gradient (G) Multi-Unit (MU)
  35. 35. • Visual Basic software • 5 potentiometers connected in parallel, as variable Rext (range 6-200 Ω, ΔR 2 Ω) • 2 multimeters for voltage (V) and current (A) measurement • Computer for data acquisition and control 35 MPPT system implementation
  36. 36. 36 Replicate MFCs construction Ref-MFC (Rext = 30 Ω, fixed) MPPT-MFC (Rext = Rint, variable)
  37. 37. Days 1 - 4 • MFCs inoculation • Rext of 30 Ω Days 4 - 53 • FIRST PERIOD • OLR of 10.5±0.7 kg COD m-3 d-1 • MPPT switched on for MPPT-MFC Days 53 - 77 • SECOND PERIOD • OLR of 5.2±0.1 kg COD m-3 d-1 • MPPT in dynamic conditions Days 88 - 103 • THIRD PERIOD (only for MPPT-MFC) • OLR of 0.7±0.1 kg COD m-3 d-1 • To outcompete methanogens Aerobic activated sludge 20% Anode effluent of lab-MFC 10% Swine manure 10% Tap water 60% BES (only for anodes) 9.5 mM 37 Inoculation and operation
  38. 38. Second periodFirst period MPPT-MFC time (days) 0 7 14 21 28 35 42 49 56 63 70 77 P(mW) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Rext,Rint() 0 20 40 60 80 100 120 140 160 180 200 P Rext Rint Second periodFirst period Ref-MFC time (days) 0 7 14 21 28 35 42 49 56 63 70 77 P(mW) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Rext,Rint() 0 20 40 60 80 100 120 140 160 180 200 P Rext Rint OLR = 10.5 kg COD m-3 d-1 [days 10 – 36] P = 0.8 ± 0.2 mW OLR = 5.2 kg COD m-3 d-1 [days 66 – 77] P = 1.8 ± 0.1 mW OLR = 10.5 kg COD m-3 d-1 [days 16 – 38] P = 2.0 ± 0.3 mW OLR = 5.2 kg COD m-3 d-1 [days 66 – 77] P = 1.9 ± 0.1 mW Ref-MFC MPPT-MFC 38 Power generation
  39. 39. Second periodFirst period MPPT-MFC time (days) 0 7 14 21 28 35 42 49 56 63 70 77 P(mW) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Rext,Rint() 0 20 40 60 80 100 120 140 160 180 200 P Rext Rint Second periodFirst period Ref-MFC time (days) 0 7 14 21 28 35 42 49 56 63 70 77 P(mW) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Rext,Rint() 0 20 40 60 80 100 120 140 160 180 200 P Rext Rint 39 Ref-MFC MPPT-MFC Start-up time: time for P and Rint to become stable • MPPT-MFC ≈ 14 days • Ref-MFC ≈ 49 days MPPT reduces start-up time of 1 month* Start-up time * Molognoni et al. (2014). Reducing start-up time and minimizing energy losses of Microbial Fuel Cells using Maximum Power Point Tracking strategy. Journal of Power Sources, 269, 403–411.
  40. 40. Comments: • Only electrical current and Coulombic efficiency are significantly different (*) • Coulombic efficiency increases with MPPT (18% with swine manure!)  How to outcompete methanogens? 40 MFC Period OLR (kg COD m-3 d-1) COD rem. (%) Imean* (mA) CECODs* (%) CEBODt* (%) CH4 rate (mL d-1) Ref First (10-36) 10.5 ± 0.7 36 ± 18 5.0 ± 0.7 6 ± 3 7 ± 3 74 ± 10 Ref Second (66-77) 5.2 ± 0.1 49 ± 10 7.5 ± 0.4 10 ±2 11 ± 1 78 ± 13 MPPT First (16-38) 10.5 ± 0.7 39 ± 15 13.5 ± 3.0 15 ± 7 18 ± 9 76 ± 7 MPPT Second (66-77) 5.2 ± 0.1 51 ± 5 11.2 ± 0.8 14 ± 4 15 ± 1 83 ± 4 Organics removal and Coulombic efficiency Differences between MFCs were analysed by ANOVA test
  41. 41. How to outcompete methanogens? Days 88 - 103 • THIRD PERIOD (only for MPPT-MFC) • OLR of 0.7±0.1 kg COD m-3 d-1 OPEN CIRCUIT 41
  42. 42. MFC Period OLR (kg COD m-3 d-1) COD rem. (%) Imean (mA) Pmean (mW) CECODs (%) CEBODt (%) MPPT First 10.5 ± 0.7 39 ± 16 14.9 ± 3.6 2.1 ± 0.3 16 ± 9 19 ± 10 MPPT Second 5.2 ± 0.1 47 ± 10 12.0 ± 2.1 2.0 ± 0.2 15 ± 5 15 ± 1 MPPT Third 0.7 ± 0.1 52 ± 22 6.2 ± 2.7 0.7 ± 0.5 68 ± 33 77 ± 10 Low OLR -> High efficiency Optimization of efficiency parameters 42
  43. 43. 43 Anode gas effluent analysis time interval (days) 14-49 50-52 53-78 79-81 88-100 Gasproductionrate(mLd-1) 0 100 200 300 400 N2-gas N2-solution CH4-gas CH4-solution CO2-gas CO2-solution OLR = 10.5 kg COD m-3 d-1 5.2 kg COD m-3 d-1 0.7 kg COD m-3 d-1 MPPT ON MPPT ON MPPT ON OPEN CIRCUIT OPEN CIRCUIT OPEN CIRCUIT no gas production detected after 3 days N2-solution CH4-gas CH4-solution CO2-gas CO2-solution 79-81 88-100 N2-gas N2-solution CH4-gas CH4-solution CO2-gas CO2-solution 00 N2-gas N2-solution CH4-gas CH4-solution CO2-gas CO2-solution Comments: • CO2 e CH4 indicate competition between exoelectrogens and methanogens • NO2 - presence in WW (18 ppm during first period) can lead to heterotrophic denitrification • Open circuit condition stops exoelectrogenic respiration and enhances CH4 production • Low OLR limits CH4 production and selects exoelectrogenic bacteria * Molognoni et al. (2015). Multiparametric control for enhanced biofilm selection in microbial fuel cells. Journal of Chemical Technology & Biotechnology.
  44. 44. Several multiphysics phenomena: • Swine manure characterization • Treatment by Microbial Fuel Cells • Organic matter oxidation, nitrification, denitrification • Electricity production • Electron acceptors competition Can we model all this? 44
  45. 45. Several multiphysics phenomena: • Swine manure characterization • Treatment by Microbial Fuel Cells • Organic matter oxidation, nitrification, denitrification • Electricity production • Electron acceptors competition • Exoelectrogens, methanogens, heterotrophs • External resistance control Can we model all this? 45 Phylum Actinobacteria Bacteroidetes Chloroflexi Firmicutes Proteobacteria WWE1 Synergistetes WPS-2 Others B A SM2 SM1 MPPT_M3 MPPT_M2 MPPT_M4 Ref_R1 Ref_R2 Ref_R4 Ref_R3 MPPT_M1 0.05
  46. 46. Several multiphysics phenomena: • Swine manure characterization • Treatment by Microbial Fuel Cells • Organic matter oxidation, nitrification, denitrification • Electricity production • Electron acceptors competition • Exoelectrogens, methanogens, heterotrophs • External resistance control • Methane production • Organic Loading Rate variation Can we model all this? 46
  47. 47. There are several modelling “levels” in Microbial Fuel Cells research: Can we model all this? 47 (Picioreanu et al., 2008) ANODE CHAMBER models: - Mass transfer within bulk liquid and biofilm - Biochemical reactions - Electron transfer from bacteria to electrode - Microbial populations dynamics SPECIFIC MODELS: - Hydrodynamic (CFDs) - Equivalent circuit, etc.
  48. 48. An introduction to biochemical models Activated Sludge Model (ASM) = IWA model framework for AS plants treating wastewater • ASM1 (1987) incorporates carbon oxidation, nitrification and denitrification processes • ASM2 (1995) and ASM2d (1999) add phosporous removal and anaerobic processes Both models adopt a biokinetic matrix notation. What is it? Mass balance equation for i component: Accumulation = Input – Output ± Reaction ∀𝑖, 𝑑(𝐶𝑖 𝑉) 𝑑𝑡 = 𝑄 𝐶𝑖 𝑖𝑛 − 𝑄 𝐶𝑖 𝑜𝑢𝑡 + 𝜈𝑖𝑗 𝜌𝑗 𝑗 𝑉 𝑑𝐶𝑖 𝑑𝑡 = 𝐷 𝐶𝑖 𝑖𝑛 − 𝐶𝑖 𝑜𝑢𝑡 + 𝜈𝑖𝑗 𝜌𝑗 , 𝑗 𝐷 = 𝑄 𝑉 Model expressed in terms of: i = model component (acetate, bacteria, oxygen, etc.) j = process (bacterial growth, decay, hydrolysis, etc.) C = concentration, V = volume, Q = flow-rate, ρ = process rate, ν = stoichiometric coefficient ∀𝑗, 𝜈𝑖𝑗 𝑖 𝑐,𝑖 = 0 𝑖 Continuity check for each j process Conversion factor [Mc Mi -1] where c are COD, N, P, charge and mass Dilution rate 48 COD continuity check in process 1: 1 + − 1 𝑌 + −1 − 1−𝑌 𝑌 = 0 OK Mass balance for component 1 (XB): 𝑑𝑋 𝐵 𝑑𝑡 = 𝐷 𝑋 𝐵,𝑖𝑛 − 𝑋 𝐵 + 1 𝜇𝑆 𝑠 𝐾𝑠+𝑆 𝑠 𝑋 𝐵 − 1 𝑏𝑋 𝐵 Example of stoichiometric matrix for aerobic bacterial growth
  49. 49. 2-populations MFC model Model components (Pinto et al., 2010) Anaerobic MFC anode chamber is populated by 2 microbial communities - Anodophilic bacteria (Xa) - Methanogenic archaea (Xm) Acetate is the only substrate (Sa) Model processes (Pinto et al., 2010) - Microbial growth (μ) on acetate - Endogenous decay (Kd) - Dilution and biofilm retention (α) - Exoelectrogenesis - Methanogenesis IMFC = 49 CH4 rate Process rates expressed by Monod kinetics
  50. 50. Wastewater characterization 50 Inert particulate material (Xi) Slowly biodegradable organics (Xs) Inert soluble material (Si) Fermentable organics (Sf) Fermentation products (Sa) Wastewater organics expressed in terms of COD (Chemical Oxygen Demand) Particulate COD Soluble COD Pinto’s model considers only the presence of acetate BUT urban and industrial wastewaters are more complex Wastewater characterization procedure STOWA method (Roeleveld & Van Loosdrecht, 2002)
  51. 51. Integration of MFC model with ASM2d 51 Pinto’s model considers only the presence of anodophils (Xa) and methanogens (Xm) BUT the anode chamber of MFCs may contain also heterotrophs (Xh) from AS inoculum Integration of MFC model with ASM2d in MATLAB Simulink environment Calibration with experimental data from MFCs treating swine manure Simulation of COD removal, current and methane production, and microbial populations dynamics Xh Sa Sf Xs Xi Xm Xa CH4 IMFC SNH4 SNO3 Salk SN2 Si SO2 • Hydrolysis • Fermentation • Aerobic respiration • Anoxic respiration (denitrification) • Endogenous respiration • Exoelectrogenesis • Methanogenesis * All processes expressed by multiplicative Monod kinetics
  52. 52. Integration of MFC model with ASM2d 52
  53. 53. 53
  54. 54. A closer look to microbial dynamics 54 Influent wastewater characterization Microbial populations Current production Methane production
  55. 55. Sustainable Water-Energy-Centric Communities Como, 12 May 2016 Dr. Daniele Molognoni, PhD University of Pavia, Italy Dept. of Civil Engineering and Architecture daniele.molognoni@unipv.it

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