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