Electrokinetic Lecture Notes

Electrokinetic RemediationElectrokinetic RemediationResearch Status & Case StudyResearch Status & Case Study

Environmental Remediation Engineering Laboratory

Korea Advanced Institute of Science and Technology

Yang, Ji-Won


ContentsContents

Introduction

Electrokinetic RemediationHistory of ElectrokineticsPrinciples of ElectrokineticsHybrid Applications & Methods

Research Status & Case StudyResearch Status of Electrokinetic RemediationCase Study: in-situ, ex-situ, pilot studies


Source of ContaminationSource of Contamination

Landfills/Waste storage facilitiesUnderground storage tanksAgricultureMiningIndustrial facilities

Wood preservingPesticide manufacturingChemical manufacturingPetroleum refining

Nuclear


Soil & Groundwater RemediationSoil & Groundwater Remediation

Original approach

Dig & Dump

Ex-situ

Dig & IncinerationDig & Wash

Pump & Treat

In-situ

Development of several technologies


Remediation TechnologiesRemediation Technologies

Slurry Phase Treatment

Composting / Landfarming

Solvent Extraction

Soil Washing

Incineration

ExEx--situsitu

Bioventing

Chemical Oxidation

Electrokinetic Process

Soil Flushing

Soil Vapor Extraction (SVE)

InIn--situsitu


Limitations of inLimitations of in--situ Technologiessitu Technologies

Works best for homogeneous, permeable soils

Difficult to apply under heterogeneous subsurface conditions such as:

Low-permeable soilsPresence of low permeable soil lenses or layers

Mobility improvement in low-permeable soils

Electrokinetic Process

Electrokinetic RemediationElectrokinetic Remediation

1. History of Electrokinetics2. Principles of Electrokinetics3. Hybrid Applications & Methods


History of ElectrokineticsHistory of Electrokinetics

The first EK phenomenon was observed. A direct current clay-water mixture. (19C)

Propose a theory dealing with the electroosmotic velocity and zeta potential. (Helmholtz & Smoluchowski equation)

Removing unwanted salts from agricultural soil. (1930s)

Dewatering soil and sludges. (1939)

To concentrate metals and to explore for minerals in deep soils. (1970s)

EK separation of metals from soils. (mid-1980s)


Electrokinetic (EK) ProcessElectrokinetic (EK) Process

ElectrokineticsA developing technology that is intended to separate and extractheavy metals, radionuclides, and organic contaminants from saturated or unsaturated soils, sludges and sediment, and groundwater

Electrokinetic remediationEspecially for the remediation of low-permeable contaminated soils


Electrokinetic RemediationElectrokinetic Remediation

Removal of the contaminants from low-permeable soilsCost-effective in-situ processSupply of low-density current


Principles of EK remediationPrinciples of EK remediation

Electrolysis(anode) H2O → 2H+ + ½ O2 (g) + 2e-

(cathode) 2H2O + 2e- → 2OH- +H2 (g)

Transport and removal of contaminantsElectroosmosisElectromigrationElectrophoresis

H+

OH-H+

H+

H+

OH-

OH-

OH-

H+

OH-

OH-

H+

(+) (-)

H+ OH-Pb+

Pb+

Cu2+

Cu2+ PAH

PAH


Applicable ContaminantsApplicable Contaminants

Heavy metals (Pb, Cd, As, Cr, Hg, Zn, Cu, Co, …)Radioactive species (Cs137, Sr90, Co60, U)Toxic anions (nitrates and sulfates)Dense, non-aqueous-phase liquids (DNAPLs)Cyanides;Petroleum hydrocarbons (diesel fuel, gasoline, kerosene, lubricating oils)ExplosivesMixed organic / ionic contaminantsHalogenated hydrocarbonsNon-halogenated pollutantsPolynuclear aromatic hydrocarbons (PAHs)


Hybrid Application & Methods 1Hybrid Application & Methods 1

Enhancement and ConditioningTo overcome the premature precipitation of ionic speciesAddition of chelating agent, acid (cathode) or base (anode) Electrolyte circulation

Use of Cation-Selective membraneIn front of the cathodeTo maintain the low soil pH

(+) (-)OH-



Electrokinetic FenceLasagnaTM ProcessMovement of contaminants to treatment zone EKImmobilization or decomposition

Treatment zone



Electrokinetic BioremediationTo activate microbes and other microorganisms present in soilsSupply and dispersion of nutrients, heating, movement of MOs

Surfactant-Enhanced Electrokinetic RemediationTo improve solubility of hydrophobic organic contaminants

WATERVELOCITYPROFILE

-ANODE + - CATHODE

- - - - - - - - -

-- - - - - - - - - -- +

Research Status & Case StudyResearch Status & Case Study

1. Research Trend: Published papers related with electrokinetic

remediation between 2002 and 2004 (<100 papers)2. Case Study of Electrokinetic Remediation


Research TrendsResearch Trends

Target contaminantsHeavy metals : • Cd, Cu, Cr(VI), Pb, Ni, Zn, Hg, As etc.Organic compounds : • PAHs (phenanthrene), Chlorinated hydrocarbons, Sovents

(phenol, ethylbenzene)Radionuclides: U, Sr

2%

23%

75%

Heavy metalOrganicsRadionuclide


Research TrendsResearch Trends

SoilMainly artificially contaminated soilThe portion of the test with contaminated soil in field site is considerable (mostly heavy metals).

48%

30%

22%

Spiked soilField soilEtc.

Scale of the testLab-scale : > 92 %Several pilot & field applications were attempted. (Metal removal)


Former timber impregnation plant, Loppersum, the Netherlands (1989)

In situ electro-reclamation at the siteAfter remediation, site became residential area.

In situ Remediation of As In situ Remediation of As Contaminated SiteContaminated Site (by (by GeokineticsGeokinetics International, Inc.)International, Inc.)

Volume: 250 m³As in heavy clayDuration: 80 days of 18 hoursEnergy: 150 kWh/ton

11


Removal of ArsenicRemoval of Arsenic

As > 250 mg/kg100 < As < 250 mg/kg

30 < As < 100 mg/kgAs < 30 mg/kg

25 m25 m

As concentration

Max. 500 mg/kg Average 115 mg/kg

Max. 29 mg/kg Average 10 mg/kg


Military airbase, Woensdrecht, the Netherlands (1992-1994)Ex situ electrokinetic remediation in temporary landfillTo reduce Cd to < 50 mg/kg

Ex situ Remediation of Heavy metalsEx situ Remediation of Heavy metals(by (by GeokineticsGeokinetics International, Inc.)International, Inc.)

Volume: 3500 m³Duration: 2 yearsEnergy: 150 kWh/ton

22


0

2000

4000

6000

8000Co

ncen

trat

ion

(mg/

kg)

75

80

85

90

95

100

Dec

reas

e (%

)

Start (m g/kg) 7300 2600 860 770 730 660

End (m g/kg) 755 860 80 98 108 47

Decrease % 90 89 91 87 85 93

Cr Zn Ni Cu Pb Cd

Change of Heavy Metal ConcentrationsChange of Heavy Metal Concentrations

< 50 mg/kg


Gaseous diffusion plant, Paducah, Kentucky (1995)Initial TCE conc. : aver. 87 ppm

Removal of TCE Removal of TCE Using Using LasagnaLasagnaTMTM ProcessProcess (by Monsanto Company)(by Monsanto Company)

5 ft

10 ft

> 50 ppmElectrodes

Carbon

3 X 4.6 m

33


Change of TCE Concentration 1Change of TCE Concentration 1


Change of TCE Concentration 2Change of TCE Concentration 2


FieldField--scale Test of Metal Contaminated Sitescale Test of Metal Contaminated Site

Naval Air Weapons Station (NAWS), Point Mugu, Ventura County, California (1998)

Contamination exists in a large area where electroplating and metal finishing operations disposed of their effluent between 1947 and 1978.Approximately 95 million gallons of plating rinse solution was discharged.

Contaminant concentrations• Cr : 180 ~ 1100 mg/kg (Regulation: <109 mg/kg)• Cd : 5 ~ 20 mg/kg (Regulation: <3 mg/kg)

(Gent et. al., J. Hazard. Mater. 110 (2004) 53(Gent et. al., J. Hazard. Mater. 110 (2004) 53--62)62)44


System DescriptionSystem Description

Anode-cathode spacing: 4.57 m (15 ft)

Same electrode spacing: 1.5 m (5 ft)

Depth: 3 m


Constant voltage: 13 V/m

Current density: 10 – 17 A/m2

6 monthsEnergy expenditure:

200 kWh/m3

System DescriptionSystem Description

Control of cathode pH: citric acid


pH distribution in depthpH distribution in depth

Between electrodes after 6 months of processingInjection of citric acidHigh pH


Removal of ChromiumRemoval of Chromium

Chromium extraction: 2319 g 1621 g78 % of soil volume has been cleared.


Chromium extraction: 70.9 g 36.8 g70 % of soil volume has been cleared.

Removal of CadmiumRemoval of Cadmium


Chemical laundry at Wildervank, Groningen, the Netherlands (2001-2004)

A pollution with VOCs has extended into a large plume of about 250m length.High grades (10 g/kg) of volatile chlorinated hydrocarbons180 g/L of PCE mass transfer at 10 m below ground surface

Remediation of Remediation of VOCsVOCs using using EK BiofenceEK Biofence (by (by HakHak MilieutechniekMilieutechniek BV)BV)

55


Site CharacteristicsSite Characteristics

Laundry

Groundwater flow

Horizontal dispersion of VOCsby groundwater

Plume

EK Biofence


Electrokinetic BiofenceElectrokinetic Biofence

Inducement of nutrientsHomogeneous dispersion of nutrientsTemperature increase

Infiltration wells for nutrients

Source of Contamination

Direction of groundwater flow

Electrokinetic Biofence area

Contaminated groundwater plume

Aquifer

Anode & Cathode electrodesEnhancement of

biodegradation inside and downstream of the fence

area


Nutrient DispersionNutrient Dispersion

Groundwater flow

Contaminated Groundwater plume

Cathode Anode

Infiltration wells with nutrients

Direction of groundwater flow

Negative charged nutrients

Infiltration well

Positive charged nutrients

Cathode


Description of EK BiofenceDescription of EK Biofence

Fence data: 30ⅹ3ⅹ10 m (LⅹWⅹD)Volume: 900 m³A-C distance: 5 mInfiltration wells: 24Power: 30A/20VGW flow: 7 m/yearContaminants:

PCE, TCE, CIS, VC Duration: 2 years GROUNDWATER FLOW

Nutrient filters

Electrodes

Monitoring wells

GROUNDWATER FLOW

Nutrient filters

Electrodes

Monitoring wells


Change of Chloride IndexChange of Chloride Index

Cl-index was decreasedVOCs were dechlorinated by bio-activity.

CathodeAnodeMonitoring wellNutrient infiltration

Index of chloride1,0-1,51,5-2,02,0-2,52,5-3,03,0-3,5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Index of chloride, March 2001

C CC AA

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Index of chloride, July 2002

C C AA

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Index of chloride, January 2003

C CC AA

GroundwaterGroundwater


Gas station site in UlsanGasoline & diesel contamination2 set of hexagonal electrode configuration

EKEK--Fenton Removal of Gas Station SiteFenton Removal of Gas Station Site((울산한국환경기술울산한국환경기술))

66

휘발유

(-) 전극

등유 경유

경유

휘발유 등유

경유

(+) 전극

경유 휘발유휘발유

휘발유

등유

사무실

2

1

6

11

3

4

9

8

5

10

12

7

2.0

1.95

2.0

1.97

2.34

1.45

2.07

2.0

1.96

2.17

1.65

1.5

2.25

1.85

2.23

2.4

2.35

2.47

2.7

2.26

2.15

2.92 2.1 2.75

Blower

Separator

정류기

유수분리조

분배기


Remediation of Gasoline & Diesel oilRemediation of Gasoline & Diesel oil

13.9ton H2O2injection

220V×10mA×16hr×60day×1.2 = 2,534KwKwPower consumption

60 (72)dayDuration

TPH : av. 90% BTEX : av. 94%%Removal

TPH : av. <10BTEX : av. <100

TPH : av.10,169BTEX : av.185㎎/㎏Initial

concentration

23.121.3%Water content

sand : 28.3%silt : 30.2% clay : 41.5%

sand : 25%silt : 29.5% clay : 45.5%

%Particle distribution

Site closingSite information and investigationUNITITEMS

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Electrokinetic Lecture Notes

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