IME Process Metallurgy and Metal RecyclingRWTH Aachen University, Germany
Prof. Dr.-Ing. Bernd Friedrich
EMC 2007, June 11-14, Düsseldorf – Germany
Drawbacks & Opportunities of ElectrocoagulationTechnology in the Wastewater Treatment
J. Rodriguez, S. Stopić, B. Friedrich
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World Water Supply
Saltwater97.5%Freshwater 2.5%
68.9% – Glaciers30.8% – Groundwater0.3% – Lakes and Rivers
Source: WHO
Total available for anthropogenic consumption is less than 0.007%
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World Water Use
1900 1920 1940 1960 1980 2000
4000
3000
2000
1000
0
Reservoir losses
Domestic
Industry
Agriculture
Source: FAO Aquastat
[Km3/a]
[Year]
In 2020, 17% more water than is available will be required to feed the world
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70%
8%
22%
0%
20%
40%
60%
80%
100%
World
Agriculture Domestic Industry
Competing Water Uses
Source: UNEP
High-Income
30%
11%
59%
Low- & Mid-Income
82%
8%10%
22%
9%
69%
Europe
4%11%
85%
Germany
A compromise concerning Sustainable Water Reuse Practices must be found
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Source: UNEP
ScarcityStress
Predicted World Water Scarcity & Stress in 2025
Water-borne diseases kill more than 25,000 peopleon a daily basis, from them a child every 8 seconds
80% of all diseases in developing countries are related to water
50% of world’s population do not have access to adequate sanitation (2.64 B.)20% do not have sustainable access to safe drinking water (1.0 B.)
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pH useful for NaOH Extended pH using lime or soda ash
pH with first precipitation Admissible pH for discharge
9pH 4 5 6 72 3
2 3 4
8
5 6 7 8 9
Mn (++)
Ni (++)
Zn (++)
Cu (++)
Cr (+++)
Al (+++)
Fe (+++)
Discharge
pH
10 11 12
10 11 12
Lack of Efficiency in Industrial Wastewater Treatment
Some heavy metals like Manganese (Mn), force the precipitation process to go over the neutral range in order to achieve their removal
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Wastewater Treatment using a Precipitation Line
ReactorReactor11
ReactorReactor22
ReactorReactor33
PumpPump
StirrerStirrer
pH meterpH meter
StorageStoragetanktank
ProductProducttanktank
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Hydroxide Precipitation of Copper Production Effluents
15min15minpH=5.7pH=5.7
+ 15min+ 15minpH=7.3pH=7.3
+ 15min+ 15minpH=9.3pH=9.3
Cu = 0.9 mg/lAl = 0.4 mg/lMn = 3.3 mg/l
Cu = 0.9 mg/lAl = 0.3 mg/lMn = 0.1 mg/l
Cu = 34 mg/lAl = 12.3 mg/lMn = 5.5 mg/l
Before treatment with sodium hydroxide NaOH:Cu = 50 mg/l Al = 13 mg/l Mn = 6 mg/l pH = 4.3
0,90,9
50
34
0,4 0,3
13 12,3
0,16 5,5
3,30
10
20
30
40
50
00:00 15:00 30:00 45:00
Time [min]
Con
cent
ratio
n [m
g/L]
4,0
5,1
6,2
7,3
8,4
9,5pH
[-]
Cu [mg/L] Al [mg/L] Mn [mg/L] pH [-]
HCl NaClNaOH +
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Proposed Electrocoagulation Mechanism
& Complexation
Al24(OH)60(H2O)2412+Al10(OH)22(H2O)16
8+
Al AlOHOH
Al2(OH)2(H2O)84+ Al6(OH)12(H2O)12
6+
Al AlOHOH
H2O
H2O
H2O
H2O
Al
H2O
OH H2O
H2OOH
H2O
Al
H2O
H2O H2O
H2OH2O
H2O
Al+ 2H3O++
Al2(OH)2(H2O)84+ + 2H3O+ = 8 H2O + + 2H3O+
, Condensation
2 Al(H2O)63+
H2O
H2O H2O
H2OH2O
H2O
Al
Hydrolysis
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Absorption Principle of Aluminium Hydroxide
WaterWater
AlAl--HydroxideHydroxide
Al24(OH)6012+. 24 H2O Al
Al
Al
Al
AlAl
AlAl
Al
Al
Al
Al
AlAl
Al
Al
OO
OH
O
OOH
O
OH
O
OH
OH
O
O
O
O
OHOH
OH
OH
OHOH
OH
Mn+
Mn+
Mn+
Mn+
Mn+
Mn+
absorbed cations
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Wastewater Treat. using an Electrocoagulation System
ECEC--ReactorReactor
Power supplyPower supply
ConductivityConductivitypH meterpH meter
Power meterPower meter
Data acquisitionData acquisition
ConditioningConditioning
FiltrationFiltration
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Electrocoagulation Treat. of Copper Production Effluents
+ 5min+ 5minpH=4.8pH=4.8
+ 5min+ 5minpH=5.1pH=5.1
Cu = 0.09 mg/lAl = 0.6 mg/lMn = 1.4 mg/l
Cu = 0.009 mg/lAl = 0.57 mg/lMn = 0.97 mg/l
Cu = 22.2 mg/lAl = 5.5 mg/lMn = 4.9 mg/l
Beforetreatment withAl-hydroxide:Cu = 50 mg/lAl = 13 mg/lMn = 6 mg/l
pH = 4.3 + 5min+ 5minpH=5.5pH=5.5
0,09 0,009
22,2
50
0,6 0,575,5
13
1,4 0,974,96
0
10
20
30
40
50
00:00 05:00 10:00 15:00
Time [min]
Con
cent
ratio
n [m
g/L]
4,0
5,1
6,2
7,3
8,4
9,5pH
[-]
Cu [mg/L] Al [mg/L] Mn [mg/L] pH [-]
No NaCl in treated effluents, enabling water reuse
No need for complete neutralization, since there is no disposal required
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0.9
0.3
0.1
0,0
0,3
0,6
0,9
1,2
1,5C
once
ntra
tion
[mg/
L]
Chemical Precipitation
Copper Aluminium Manganese
Hydroxide Precipitation vs. Electrocoagulation
pH = 9.3 pH = 5.1
Electrocoagulation
0.09
0.6
1.4
110 m3/y 526 m3/y
4.8 kWh/m3 2 kWh/m3
11 EUR/m3 0.82 EUR/m3
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S O
W T
SWOT Analysis – Hydroxide Precipitation
Effective option for very acidic industrial wastewatersEffective option for very acidic industrial wastewaters
Nei
ther
Nei
ther
aafa
stfa
stno
rno
r aaco
stco
st-- e
ffect
ive
effe
ctiv
ete
chno
logy
tech
nolo
gy Not suitable for sustainable developm
entN
ot suitable for sustainable development
Very simpleVery simpledosage processdosage process
Expensive materialExpensive materialraw (NaOH), whichraw (NaOH), whichcertainly influencescertainly influencestreatment processtreatment process
(<1 mg/l)(<1 mg/l)
EnvironmentalEnvironmentalconcerns due toconcerns due to
neutral salty neutral salty effluents aftereffluents after
treatmenttreatment
Suitable for effluentsSuitable for effluentswith low pH valueswith low pH values
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SWOT Analysis – Electrocoagulation
Best option for the majority of industrial wastewatersBest option for the majority of industrial wastewaters
Rel
iabl
e fa
st &
cos
tR
elia
ble
fast
& c
ost -- e
ffect
ive
tech
nolo
gyef
fect
ive
tech
nolo
gy Suitable for sustainable development
Suitable for sustainable development
Low energy demandLow energy demandper cubic meter &per cubic meter &best metal removalbest metal removalat higher flow ratesat higher flow rates
(0.09 mg/l Cu)(0.09 mg/l Cu)
May require externalMay require externalpH conditioning forpH conditioning for
some effluentssome effluents
Uncertainties asUncertainties asregards renewableregards renewableenergy resourcesenergy resourcesrequired to driverequired to drivethe ECthe EC--process process
Higher efficiencies Higher efficiencies regarding materialregarding material
raw usage and raw usage and disposal costdisposal cost
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MechanicalTreatment
• Influx• Sand removal• Sedimentation
BiologicalTreatment
• Oxidizing beds• Aerated filters
• Membrane reactors
ChemicalTreatment
• Phosphorous removal• Nitrogen removal
• Disinfection
Excess of nutrients as Phosphor and Nitrogen causes Eutrophication
Lack of Efficiency in Municipal Wastewater Treatment
Electrocoagulation
Chemical Treatment+⇔+ 2 Al (OH)316 H2OAl2(SO4)3 + 10 H2O 3 H2SO4
+⇒+2 Al (H2O)63+ Al (OH)2 (H2O)8
4+ 2H3O2 e–
EutrophicatedEutrophicated
NormalNormal
Municipal EffluentsMunicipal Effluents
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Electrocoagulation Treatment of Municipal Wastewater
Treated EffluentsTreated Effluents
BeforeBefore AfterAfter
Ortho-P = 4,3 mg/lTSS = 500 NTU COD = 572 mg/lTOC = 166 mg/lTNb = 41.1 mg/l
NH4-N = 28.9 mg/l
Ortho-P < 0.05 mg/lTSS < 1 NTU
COD = 251 mg/lTOC = 97.5 mg/lTNb = 19.4 mg/l
NH4-N = 20.5 mg/l
99.199.1 99.899.8
56.156.141.341.3
52.852.8
29.129.1
0%
20%
40%
60%
80%
100%
Overall Removal Rates [%]
ElectrocoagulationOrtho-P TSS COD TOC TNb NH4-N
Phosphor Ortho-P and suspended solid TSS removal up to 100%, as well as over 50% organic loads removal like COD, TOC, TNb; providing a sustainable methodology for municipal wastewater treatment and agricultural water reuse
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Effluents after ECEffluents after EC--processprocessRegular Tap WaterRegular Tap WaterNonNon--Treated EffluentsTreated Effluents
After ElectrocoagulationAfter ElectrocoagulationAfter Hydroxide PrecipitationAfter Hydroxide Precipitation
Improved separation of organic matter without contamination of residual sludge, enabling sustainable water reuse practices while providing better support to waste management cycles and clean energy production
Conclusions – Sustainable Water Reuse Practices
Higher metal removal rates without increasing the content of neutral salts, resulting in greater water reuse opportunities and improved cost-efficiencies due to material raw usage and avoidance of disposal fees
Salty effluents No salty effluents
No marketable sludge Marketable Sludge
Eutrophicated
Healthy
Lack of nutrients
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Outlook – Sustainable Water Management Concept
ElectrocoagulationElectrocoagulation Biological TreatmentBiological Treatment
CommuneCommune
MunicipalMunicipalWastewaterWastewater
Clean EnergyClean Energy
Ferromagnetic SeparationFerromagnetic Separation Metal RecyclingMetal Recycling
Biogas ProductionBiogas Production FertilizersFertilizersBiogas CombustionBiogas CombustionElectrical GridElectrical Grid
Water ReuseWater Reuse
Basic NeedsBasic Needs
Waste ManagementWaste Management
ElectricityElectricity BiogasBiogas SludgeSludge
IronIron
Water CycleWater CycleWastewaterWastewater
ElectricityElectricity
SludgeSludgeBiogasBiogas
IronIron
Water CycleWater Cycle
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EECCEECC
Acknowledgements
Opt
imiz
ing
Ener
gy U
se
Opt
imiz
ing
Ener
gy U
seProm
oting Sustainable Development
Promoting Sustainable Developm
ent
Improving Wastewater TreatmentImproving Wastewater Treatment
ElectricalElectricalEngineeringEngineering
ChemicalChemicalEngineeringEngineering
ProcessProcessEngineeringEngineering
PrecipitationPrecipitation
ElectrolysisElectrolysis
ElectroElectro--coagulationcoagulation
HydrolysisHydrolysis
Sixth FrameworkProgramme
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Thank you for your attention.
EMC 2007, June 11-14, Düsseldorf – Germany
IME Process Metallurgy and Metal RecyclingRWTH Aachen University, Germany
Prof. Dr.-Ing. Bernd Friedrich