current trends in anaerobic digestion · electric power output (kw-e.m-3 reactor 0.25 – 1.7...
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Current Trends in Anaerobic Digestion
Diversifying from waste(water) treatment to re-source oriented energetic conversion
techniques
Lettinga Associates Foundation (LeAF) Wageningen University, The Netherlands
Jules B. van Lier & Grietje Zeeman
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AD ↔↔↔↔ Energy: heat, energy carriers, electricity
Anaerobic conversions
COD
“heat”
Sludge
Reduced liquid compounds: VFA, alcohols, LCFA, alkanes??*
*Zengler et al., ’99, Nature 401, 266-269: alkanes�CH4
Electrons: MFC/BES
Energy content biomass:
≈ 13.5 MJ/kg COD
“Conservation of electrons”
Reduced gases: CH4, H2, (H2S)
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AD ↔↔↔↔ Energy: heat, energy carriers, electricity
Anaerobic conversions
COD
“heat”
Sludge
Energy content biomass:
≈ 13.5 MJ/kg COD
“Conservation of electrons”
Reduced gases: CH4, H2, (H2S)
SUBSTRATES:- Solid wastes- Slurries- Manure- Energy crops - Co-digestion- Wastewater
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Energy recovery in anaerobic wastewater treatment
Completely mixed
!"#$%&'
influent effluent
Relative capacity: 1
Physical retention
Relative capacity: 5
Immobilisedbiomass
Relative capacity: 25
Enhanced contact
Relative capacity: 75
Development of “high-rate” anaerobic treatment systems
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Influent
Sludge bed
Settler
EffluentBiogas
Sludge blanket
2 2
1 1
3 32
1. Sludge/biomass inlet2. Gas baffle plates3. Return settled sludge
From UASB to EGSB
Sludge bed
Influent
Effluent
Biogas
2
1
1. Sludge/water mixture2. Settled sludge
Recyc
le
BIOTHANE SYSTEMS
INTERNATIONAL
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Application of Multi-layer settling system
From UASB….
..to IC (EGSB)
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Historically applied anaerobic processes
(1981 – 2007 (Jan.) N= 2266)
(Granular) sludge bed based: 77%
IC15%
UASB50%
* 1%FB 2%
HYBR 3%
LAG 4%
CSTR 7%
AF 6%
EGSB 12%
* References with incomplete data (1%)
Source: Worldref. 04-2007
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Currently Applied Anaerobic Processes
(2002 – 2007 (Jan.), N= 610)
* References with incomplete data (1%)
Source: Worldref. 04-2007
(Granular) sludge bed based: 89%
Expanded Bed Reactors: 55%
IC33%
* 1%
FB 2%
HYBR 2%
LAG 1%
CSTR 4%
AF 1%
EGSB 22%
UASB34%
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Full Scale Expanded Bed versus UASB Systems
UASB
Expanded Bed (EGSB, IC, FB)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
1980 1985 1990 1995 2000 2005 2010
Year
Perc
en
tag
e o
f yearl
y p
roje
cts
UASB
HIGH RATE (EGSB+FB+IC)
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Full scale AWWT at beer brewery
Bavaria, LieshoutHeineken, Den Bosch
UASB IC
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Worldwide cumulative anaerobic references
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
19
72
19
75
19
76
19
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00
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20
04
20
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20
06 *
Year
Refe
ren
ces
Anaerobic Industrial Wastewater Reactors, census 2007over 2200 registered high-rate reactors+ ≈ 500 (?) non registered (“home made”)
Van Lier, Wat.Sci.Technol. 57(8), 2008; Data collected by Yolanda Yspeert
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AGRO-FOOD INDUSTRY BEVERAGE ALCOHOL
DISTILLERY
PULP & PAPER MISCELLANEOUS
Sugar
Potato
Starch
Yeast
Pectin
Citric acid
Cannery
Confectionery
Fruit
Vegetable
Dairy
Bakery
Beer
Malting
Soft drink
Fruit juice
Wine
Coffee
Sugar cane juice
Sugar cane molasses
Sugar beet molasses
Grape wine
Grain
Fruit
Recycle paper
Mechanical pulp
NSSC
Sulphite pulp
Straw
Bagasse
Chemical
Pharmaceutical
Sludge liquor
Municipal sewage
Landfill leachate
Acid mine water
High-rate Anaerobic Applications in Industries
Beer, Brazil
Paper, Netherlands
Yeast, ItalyDistillery,
Japan
Chemical,Netherlands
36% 29% 11% 14%10%
Number of installed reactors, N= 2266 (Jan. 2007)
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PARAMETER UNIT Brewery
Flow m³/d 2720 – 5780
COD average
COD range
mg/l
mg/l
4043
2020 – 5790
SS mg/l 260 – 2160
TemperatureOC 21 – 40
PH 2.6 – 7.0
Full scale example: Brewery Effluent
COD-load: 17 ton/dayRequired reactor dimensions:V = 500 m3 only, h = 25 m, d = 5 m
0
1000
2000
3000
4000
5000
6000
0 100 200 300 400 500 600 700
DAY NUMBER
SC
OD
CO
NC
EN
TR
AT
ION
(m
g/l
)
COD influent COD effluent
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Brewery effluent: Energy benefit!
Energy recovered:17 ton COD x 0.85 (eff) x 3820 kWh** x 40% CHP eff. = 22 MWh-e/day ≈ 1MW powerplant
No energy consumption: Average energy requirement activated sludge: ≈ 1 kWh-e/kg COD removed
Saved: 17 ton COD x 0.85 (eff.) = 15 MWh-e/day
Total energy benefit: 22 + 15 = 37 MWh-e/day≅ 3300 €/d (with 0.09 €/kWh)≅ 1.2 x 106 €/year
Energy content 1 ton COD ≈ 13.5 GJ ≈ 3.8 MWh
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Brewery effluent: CO2 emission reduction!
Energy recovered:
17 ton COD x 0.85 (eff) x 3820 kWh** x 40% CHP eff. = 22 MWh-e/day ≈ 19 ton CO2 reduction/day (coal)
No energy consumption:
17 ton COD x 0.9 (eff.) = 15 MWh-e/day≈ 13 ton CO2 reduction/day (coal)
Total CO2 emission reduction: 19 + 13 = 32 ton CO2 /day
≅ 380 €/d (with 20 €/ton CO2)≅ 140.000 €/year
Coal powered electricity plant: 0.86 ton CO2/MWh-e
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1.9 – 13CO2 emission reduction (tonCO2.m-3.y-1,
compared to coal-driven power plant)
0.25 – 1.7Electric power output (kW-e.m-3 reactor installed)
55 – 390Energy output (MJ.m-3 reactor installed.d-1)
10 – 35Loading capacity (kg COD.m-3.d-1)
Assumptions: - 80% CH4 recovery relative to influent COD load - 40% electric conversion efficiency using a modern
combined heat power (CHP) generator- Intermediate values are obtained by linear interpolation.
Energy output and CO2 emission reduction using AD systems
2008 state-of-the-art
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Importance for developing countries:
Energy recovery & CO2 credits as an incentive to implement environmental technologies in developing countries ?
Treatment alcohol distillery effluents Cuba (Santa Clara):- 800 m3.d-1, - 65 kg COD.m-3
Anaerobics: 13,500 m3 CH4.d-1
or: about 2.2 MW-electric (40% eff.)At a price of 0.12 US$ .kWh-1 this equals: 2.300.000 US$.y-1
CO2 credits: 330.000 US$.y-1 (coal)
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board industry
H2S removal
steam
80 ton/d
9000 m3/d biogas
0.2 ton/d
sulfur
paper
1000 ton/d
1050 ton/d
stock
1000 m3/d 1000 m3/d
fresh water evaporation
55 oC
waste sludge
1 ton/d
4000 m3/d
cooling
aerobicanaerobic
35 oC
4000 m3/d
More energy from “end-of-the-pipe” to “zero-discharge”
Energy savings
no effluent 1045* MJ/ton
(115 MWh-e/dag)anaerobics 200 MJ/ton
(22 MWh-e/dag)
corrugated card board industry
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Anaerobics as “kidney technology”?
1. How to cope with more extreme conditions?:- Accumulation of toxic / recalcitrant compounds- temperature increase (thermophilic)- salinity increase (Na+)
2. Biofilm/granule stability guaranteed?3. Integration with complementary technologies?
- Adapting / optimising sludge bed systems?- Alternative anaerobic technologies?
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Ca++ extraction by Na+
Na+
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Granule Strength Decreaseafter 6 months of UASB operation
Fines production in bubble column
Jeison et al, Wat.Sci.Technol., 2008Ismail et al., Wat.Sci.Technol., 2008
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Anaerobic MBR technology for extreme conditions?
Application potential:- when sludge immobilisation is not likely (high
temperatures, high salinity, fluct. pH) - presence of recalcitrant compounds (spec. bacteria)- high solids concentrations - other extremes?
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JC
(L/m 2d)
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(m/h)Biomass
Concentration (gSS/L)
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(Jeison and van Lier, J. of Membr. Sci., 2006)
Extreme conditions beneficial for membrane filtration ?
Impact of temp. on achievable membrane flux
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0
5
10
15
20
25
0 50 100 150 200 250
Time (d)
Cri
tical fl
ux (
L/m
2h
)
R1: thermophilic
completely acidifiedR3: mesophilic
completely acidified
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Role of anaerobics in novel sanitation concepts
MDG can not be reached!2008: UN year of sanitation
Black water
Grey water
Urine
Rain water
1.2 + 35
Water quantity (l/d)
100
85
(Re)source oriented sanitation concepts (Desar):
AD in Desar:- sludge stabilisation- nutrients production- energy production- scavenger micropollutants
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Resources from domestic wastewater?
Black water
Grey water
Urine
Rain water
1.2 + 35
Water quantity (l/d)
10085
Urine + faeces= 1.2 l/pers./day !!
Recovery of energy &
nutrients feasible
Grey water for irrigation!!
Urine + faeces + kitchen waste:- 1.5 l in volume- 91 % N- 69 % P- 70 % COD- Pathogens- salts- micro pollutants
(Zeeman et al., 2007)
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Black water treatment: Sneek
Black water vacuum toilets
UASB (ST)Struvite(MAP) precipitation
Autotrophic N removal (OLAND) Discharge
to surface water
Final polishing
stabilized sludge (reuse?)
Sludge(return UASB)
CH4
MAP(fertilizer)
N2
Black water vacuum toilets
UASB (ST)Struvite(MAP) precipitation
Autotrophic N removal (OLAND) Discharge
to surface water
Final polishing
stabilized sludge (reuse?)
Sludge(return UASB)
CH4
MAP(fertilizer)
N2
UASB (ST) HRTmin=7d;
Tmax = 30oC
Struvite tcontact=30min
N-removal HRTmin=3.5d
Mg++
MgNH4PO4
Zeeman et al., Wat.Sci.Technol., 2008
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Energy in
MJelectric.p-1.year-1
EnergyUtility
Biogas production
(black/grey water, kitchen waste)
Waste(water) treatment
10,5 m3 CH4.p-1.y-1
= 374 MJ.p-1.y-1
131
Energy consumption
Vacuum transport 25 kWh.p-1.y-1 -90
Kitchen waste grinders
-5 kWh.p-1.y-1 -18,0
Post- treatment -43
Energy saving STP 24 kWh.p-1.y-1 86
Conventional sewer
30 kWh.p-1.y-1 108
Drinking water 0.5 kWh.m3produced 26
Total 200
Energy balance of the Sneek concept:
Zeeman et al., Wat.Sci.Technol., 2008
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Domestic wastewater as a resource (Sneek results):
Total energy savings in Sneek: 200 MJ.person-1.year-1
Extrapolating to the Netherlands: 915 million kWh/year
≅ 100 MW
≅ 200.000 4-persons households
Nutrients: 0.14 kg P.person-1.year-1
or: 2.310 ton P.year-1 as struvite (NH4MgPO4)
Potentially reusable grey water: 90 l.person-1.year-1
≈540 million m3.year-1 in NL≈(8-11 million ha irrigated area..)
2000 2010 2020 2030 2040 2050 2060 20700
20
40
60
80
100
year
‘Available' phosphorus reserves (%)
2% growth
2.5% growth
3% growth
apatite
Source: Driver et al. (2001)
2000 2010 2020 2030 2040 2050 2060 20700
20
40
60
80
100
year
‘Available' phosphorus reserves (%)
2% growth
2.5% growth
3% growth
2000 2010 2020 2030 2040 2050 2060 20700
20
40
60
80
100
year
‘Available' phosphorus reserves (%)
2% growth
2.5% growth
3% growth
apatite
Source: Driver et al. (2001)
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AD sanitation potentials for developing countries??
- prevent diseases- prevent water pollution- protect drinking water source- produce nutrients- produce energy
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AD is consolidated technology for wastewater treatment
Conclusions
AD may play a prominent role in sustainable sanitation approaches coupling: hygiene, disease prevention, energy recovery, production of fertilisers, protection water resources/environment.
Energy efficiency and actual energy recovery is a driver of increasing importance!... 1 ton COD ≈ 13.5 GJ.…
AD needs adaptation to more extreme environments! Need for stable sludge bed systems, anaerobic MBR, other?
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Tania Fernandes
Lina Abu Ghunmi
David Jeison
Grietje ZeemanHardy Temmink
Thanks to all colleagues, PhDs and research fellows
Ghada Kassab
Thobias Bigambo
Sammy LetemaRosaElena Beas
Shahrul Ismail
Claudia Pabon
KirstenSteinbush
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Direct scavenging of electrons
Clean waterWastewater
Anaërobe cel
CO2
+ 4H+
[CH2O] + H2O
4e-
H+
Aërobe cel
Met water en zuurstof
Beluchting(O2)
4e-
O2 + 4H+
2H2O
+-
KathodeAnodee-
e-
Scheidings-wand
Anaerobic cell
CO2
+ 4H+
[CH2O] + H2O
4e-
H+
Aerobic cell
Aeration (O2)
4e-
O2 + 4H+
2H2O
+-
CathodeAnodee-
e-
Ion selective -membrane
Organic matterconversion
Water reduction
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Biomass cascading in alcohol distilleries, Brasil
Van Haandel, 2004
Van Haandel & Van Lier, 2006
= percentage of cane energy
Output without AD of wastes= 5 m3 EtOH/ha= 4 ton EtOH= 40% cane energy
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Biomass cascading in alcohol distilleries, Brasil
Optimised energy output alcohol distillery:(using all by-products)- Heat (steam production for local use)- Surplus Electric (35% eff.): 6.3 MWh-e/(ha.y) (≈ 0.7 kW/ha)- Liquid: alcohol: 5 m3/(ha.y)
alcohol price (2006): 400 US$/m3 (≈ 300 €/m3)Total economic benefit: 1500 + 630 = 2130 €/(ha.y).
Full digestion of cane: 24 MWh-e/(ha.y) ≈ 2.8 kW/ha
50 % digestion eff. of solid fractionNon-digestable fraction is incinerated
At 0.10 €/KWh-e: 2400 €/(ha.y)……..
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Bio-methanation of energy crops: sustainable contribution ?
Maiz
MiscanthusGenerally: 0.5 – 1.5 MW-eHRT up to 90 days…
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Substrate
0
10
20
30
40
50
60
0 42 84 126 168 210 252 294 336 378 420 462 504 546 588 630Time
Su
bs
tra
te I
np
ut
t.d-1
0 500
1 0001 500
2 0002 500
3 0003 500
Me
tha
ne
pro
du
ctio
n
Nm
CH
43
. d-1
Maize whole crope silage Grass Clover Methane Production
Resch, Braun and Kirchmayer, 2007.
AD reactor not the biggest concern..- raw materials- logistics- maximising energy recovery- digestate application- etc.