mercury cleanup through the use of electrochemical remediation technologies

Weiss AssociatesP2-Soil Remediation, Inc.

Electro Petroleum Inc.

presentation at

“Breaking the Mercury Cycle” ConferenceBoston, Massachusetts

May 1–3, 2002

prepared by

Falk Doering, Ph.D., & Niels Doering—P2 Soil Remediation, Inc.Joe L. Iovenitti, Donald J. Hill, Ph.D., & William A. McIlvride—

Weiss AssociatesJ. Kenneth Wittle—ElectroPetroleum, Inc.

Weiss Associates is skilled and experienced in areas essential to Environmental Industry geoscience problem solving. Staff membersinclude geologists; hydrogeologists; civil, environmental, chemical and mechanical engineers; environmental scientists; regulatory specialists and technicians.

We recognize that each individual'sintelligence, creativity and perseverance are essential ingredients to create a superiorwork product. These individual human traits are cultivatedand encouraged at WA.

WA's staff uses the most advanced field equipment, techniques and computer technology. Quality is maintained through communication with staff and careful recruiting, training and supervision. The result is work that consistently satisfies or exceeds the require-ments of our clients and local, state and federal regulators.

Expertise in Geology, Engineering and Environmental Science

At Weiss Associates,outstanding

people produce outstanding

results.

For additional information, please contact Joe L. IovenittiTelephone (510) 450-6141 Fax (510) 547-5043 e-mail [email protected]

MERCURY CLEANUP THROUGH THE USE OF

ELECTROCHEMICAL REMEDIATION TECHNOLOGIES

K:\mrktng\presenta\technolo\direct current\ECRT\presentations\oral\NEWMOA_Hg\ECRT-IC Hg8.ppt

© Weiss Associates, 2002. Reproduction or transmittal in any form or by any means, with prior written permission only.

DIRECT CURRENT TECHNOLOGIES

Direct Current Technologies (DCTs)

Electro-Kinetic Aided Remediation (EKAR)

Carbon Dioxide Vacuum Stripping Wells with Electrolytic Destruction

(CVS-II)

Induced Complexation(IC)

Geotechnical Applications

ElectroKinetics

ElectroChemicalGeoOxidation (ECGO)

ElectroChemical Remediation



INDUCED REDOX REACTIONS How Do They Occur?

Electrodes are placed in the sediment where a low voltage and low amperage coupled DC/AC field is imposed

An Induced Polarization (IP) field is created the soil acts as a capacitor, discharging and charging

electricity electrical discharge cycle causes reduction electrical charging cycle causes oxidation

REDOX reactions occur at a high frequency throughout the matrix



INDUCED REDOX REACTIONS Where Do They Occur?

In the soil under Ex-Situ or In-Situ conditionsReactions take longer in gravel than fine sand, fine sand

takes longer than clay Reaction rate is inversely proportional to grain size

At the Pore ScaleTheory = Reactions occur at any and all interfaces within

the soil-water-contaminant system

No pumping or addition of chemicals required during ECRTs-ECGO or ECRTs-IC.



ELECTRICAL ENERGY INPUT



ECRTs—ECGO ELECTRICAL DISCHARGES



Soil Particle or Colloid

Sorbed water molecule

Hydrated Anion

Capacitor Structure

Outer Helmholtz Plane

Inner Helmholtz Plane

Diffuse layer

Hygroscopic Water— serves as a dielectric

A zone of redox reaction

Hydrated Cation

REDOX reactions occur at any and all interfaces and are believed to result from electrolysis of water.

ECRTs PORE SCALE REDOX MODEL



Water TDS: ~ 3.5 g/l mainly sodium chloride

Main Pollutants: Elemental and methyl Hg

Electrodes: Steel pipes 192 mm OD, each 8 m long

Power input: 5.6 kW

Sediment: silts

UNION CANAL, SCOTLAND

Initial Average Total Hg Concentration: 243 mg\kg




220 m3



Results (all figures in mg Hg/kg dm)

Hg

0100200300400500600700800900

0 2 4 6 8 10 12 14 16 18 20 22 24 26days

[mg/

kg d

.m.]

T1 anode

T6 anode

T3 middle

T5 middle

T2 cathode

T4 cathode

outside


After 26 days of remediation 168 lbs of mostly mercury was deposited on both electrodes

Post-remediation average total Hg Concentration = 6 mg/kg; cleanup objective was 20 mg/kg

Sample Location Remediation Time (days)1 12 26

T1 anode 33 204 11T6 anode 218 417 9T3 middle 102 36 11T5 middle 282 48 6T2 cathode 98 45 4T4 cathode 156 9 0.7Outside 809 73 4Average Concentration 243 119 6.5



MONTLUÇON, FRANCE 350 T of Sewage Treatment

Plant Sludge Contaminated with Hg from Dental Amalgams

Pretreatment Hg Concentration = 15 mg\kg to 54 mg/kg; Cleanup Level = 5 mg/kg

Ex-Situ Treatment with 2.3 kW Power Input over 7 Days; Total Project Electrical Cost ~$40 @ $0.10 \ kW-hr

Final Hg concentrations = 0.02 to 0.35 mg/kg, Significantly Below the Cleanup Level

.



Y-12 PLANT, OAK RIDGE ECRTs Mercury Remediation Laboratory Test

Soil box: 90 cm x 50 cm x 45 cm with 150 L of saturated (fresh water) Y-12 contaminated clay loam

Plate electrodes: 80 cm x 32 cm

Initial Hg concentration: 252 mg/kg



Y-12 PLANT, OAK RIDGE

Typically ECRTs Can Not Be Tested in the Laboratory Due to the Electrical System Resistance

Y-12 Plant Soil Contains 12,000 mg\kg Iron Making It Highly Electrically Conductive Allowing the ECRTs-IC Phenomena to Occur

Evidence for the ECRTs-IC Phenomena Is Indicated by the Migration of Mercury to the Anode which Can Only Occur Through the Formation of Negative Hg Complexes Hg concentration increase is >100% at anode Hg concentration decrease is 60% at cathode

ECRTs Laboratory Test




Sampling the Test Array

Sampling after 81, 450, and 741 hrs of operation at sites between anode and cathode electrodes

Sampling Locations at the Anode Face, Quarter Point, Mid-Point, Three Quarter Point, and Cathode Face

Approximate Plate Electrode Positions



Y-12 PLANT, OAK RIDGE TEST DATAECRTs Laboratory Test—Change in Total Mercury Concentration

0

100

200

300

400

500

600

Anode Face Quarter Point Mid-Point Three-Quarter Point Cathode Face

Sampling Location between Anode and Cathode Electrodes

Tot

al M

ercu

ry C

once

ntra

tion

(mg/

kg)

Pre-Test Concentration

After 81 hr of Operation





ECRTs Laboratory Test—Percent Change in Mercury Concentration Based on Aqua Regia Leach Test

-80%

-40%

0%

40%

80%

120%


Sampling Locations between Anode and Cathode Electrodes

% C

hang

e

Baseline

After 81 hrs of Operation



Y-12 PLANT, OAK RIDGE TEST DATA



Y-12 PLANT, OAK RIDGE TEST DATAECRTs Laboratory Test—TCLP Data

0

200

400

600

800

1000

1200

1400


Sampling Locations between Anode and Cathode Electrodes

TC

LP

Lea

chat

e C

once

ntra

tion

(mg/

L) Pre-Test Concentration


Clean-Up Target




Hg Contaminated Soils Saturated with Fresh Water Were Successfully Treated to below the DOE Site Imposed TCLP Cleanup Level Mercury species reported by DOE Site to be present include:

mercury chloride, mercury nitrate, mercury sulfide, elemental mercury, and methyl mercury

No detailed Hg speciation conducted during test reported herein

Laboratory Results Corroborate Fresh and Brackish Water Field Remediation Results

LABORATORY TEST RESULTS




Work conducted for the U.S. Department of Energy (DOE) National Environmental Technology Laboratory (NETL) in cooperation with DOE Oak Ridge Operations Office and Bechtel Jacobs, LLC, the DOE Oak Ridge environmental site contractor.

Work completed with assistance from TPG Applied Technology, ADA Technologies, Inc., and Hazen Research.

ACKNOWLEDGEMENTS



FUNDED ECRTs PROJECTS PCBs in Soils/Sediment at an Upland Site, New York

Hg, Phenols, PCBs and PAH in Marine Sediments, Puget Sound, Washington (USEPA SITE Program Project)

Chlorinated Volatile Organic Compounds in Soil and Ground Water, NAS Dallas, Texas

PAHs in Lake Superior Fresh Water Sediments, Minnesota

mercury cleanup through the use of electrochemical remediation technologies

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