Kurt D. Pennell, PhD, PE, BCEEDepartment of Civil & Environmental Engineering

Tufts UniversityJed Costanza, Kelly Fletcher, Tyler Marcet, Natalie Cápiro,

and Frank Löffler

Thermal Treatment of ChlorinatedSolvents Offers Opportunities for

Combined Remedies

Advances in Thermal Remediation Workshop University of Texas at Austin

January 8-9, 2013

Combined Remedy Scenarios

Remediation Time or Cost ($)

Soi

l or G

roun

dwat

er

Con

c.

Remediation target (e.g., MCL)

“Stalled” Remediation

2. Combine remedies (in series) to achieve remediation goals (polishing step).1

2

1. Combine remedies (in parallel) to improve effectiveness and reduce time/cost of treatment.

3. At complex sites, combine remedies in space and time to more effectively achieve remediation goals.

4. Ultimate goal is site closure; inst./eng. controls

Remediation Technologies: What’s Hot, What’s Not

Hot

Not

Bioremediation (Bioaugmentation, Biostimulation, MNA)

Thermal Treatment (electrical resistive heating, steam flushing, conductive heating, combustion)

Chemical Oxidation/Reduction (ISCO, nano)Dig and Haul (ex situ treatment/disposal)Permeable Reactive Barriers/Walls (ZVI, zeolite)Surfactant/Cosolvent FlushingSoil Vapor Extraction (SVE)/Air SpargingPump and Treat

Documented successes, and not many “failures”

Prevalence of complex and/or low permeability sites

Industry and Regulatory Acceptance: Advocates and skilled practitioners

Research Funding/Activities Limitations/failure of other technologies

Emergence of Thermal Remediation

Primary limitation is cost (ca. $2-4M for small sites), Other issues: energy/carbon, patent rights, safety

Example Chlorinated Solvent SiteGroveland (MA) Superfund Site

ERH+Steam Treatment of TCE Source Zone

6

Groveland Superfund Site Timeline

http://cfpub.epa.gov/supercpad/cursites/csitinfo.cfm?id=0100750

• 1979: TCE detected in town water supply wells• 1983: NPL Listing• 1992: PRP installed SVE system• 2000: EPA-funded groundwater extraction,

treatment, discharge system installed• 2002: PRP abandoned site, SVE closed • 2008: Extracted and treated a total of 388 MG

water and recovered 1,100 lbs VOCs• 2010: Thermal Remediation: Steam+ERH, ca. $3M

Petroleum Hydrocarbon Remediation

Oil Lakes in Kuwait (first Gulf war,1990-1991)

United Nations Environmental

Program (UNEP)(e.g., Nigeria)

Category Hot Water Injection

Steam Injection

Conductive Heating

Electrical Resistive Heating

Electro-magneticHeating

Heat Transfer Convective Convective Conductive Conductive Radiative

Energy Source Hot Water Steam Steel Well Casing Electrical Electromagnetic

Temp. Limit 100oC 100-120oC 100-800oC 100-120oC 100-300oC

Technology Example

Contained Recovery of Oily Waste (CROW)

Steam Enhanced

Remediation (SER)

In-Situ Thermal

Desorption (ISTD)

Three/Six-Phase

Heating (SPH)

Microwave; Radio

Frequency

AdvantagesNo Phase

Change, Low Cost

High Perm Zones,

Energy Efficient

Low Volatility Contaminants

Lower Cost, Low Perm.

Zones

Uniform Heating, Low

Perm.

LimitationsPreferential Flow, Low Efficiency

Pref. Flow, Cost, DNAPL,

Safety

High Element Density, Cost, Temp, Safety

Pref. Heating, Drying, Safety

Low Energy Transfer-Drying

Field Sites: Source Zone

UGI ColumbiaBrodhead Creek

Visalia, CASRS, SC

Rocky Mtn Arsenal

Alhambra Pole

Fort Lewis, WA

Paducah, KY

Kelly AFB, SRS, Kirkland AFB

Comparison of Thermal Remediation Technologies

Self-Sustaining Treatment for Active Remediation (STAR)

(a.k.a. Smoldering Combustion)

1. Slow burning process involving oxidation of condensed phase (solid/liquid) at the fuel surface.

2. Ignition source plus air (oxygen) source; can be self-sustaining.

3. Typically applied to oils and coal tars at relatively high saturations (pilot at cresol site in NJ).

Switzer et al., 2009, ES&T, 43: 5871-5877.Pironi et al., 2011, ES&T, 45: 2980-2986.U.S. Patent No. 8,132,987; 2012.

Research Motivation

• In situ thermal treatment offers two distinct advantages relative to competing technologies • No chemical agents are introduced into the subsurface • Potential to effectively treat low-permeability, heterogeneous

subsurface formations

• However, very little was known about:• Chemical reactivity and reaction pathways• Effects of subsurface heating on microbial activity

• These knowledge gaps limit our ability to understand and improve thermal remediation technologies, and to design effective combined remedies or polishing technologies.

Thermal Treatment Processes

Physical Recovery: Heat subsurface to increase rate of mass transfer from condensed phases (e.g., NAPL, solid) to mobile phases(e.g., water, gas)Abiotic Reactions: Increase in temperature may increase rate of abiotic chlorinated solvent degradation due to:

• Oxidative dechlorination (Knauss et al., 1999, Appl. Geochem., 14:531)

2C2Cl3H + O2(aq) + 2H2O 4CO2 + 6HCl • Reductive dechlorination (Truex et al., 2007, Ground Water Monit. R., 2:96)

C2Cl3H + 3Fe0 + 3H+ 3Fe2+ + C2H4 + 3Cl-

• Hydrolysis (Jeffers et al., 1989, Environ. Sci. Technol., 23:965)

C2Cl3H + 4H2O 2CO2 + 3HCl + 3H2Δ

Δ

Δ

Biotic Reactions: Increase in temperature releases organic compouds electron donor; potential to stimulate or inhibit microbial reductive dechlorination

Research Objectives

• Measure physical-chemical and sorption-desorption properties of PCE and TCE as a function of temperature

• Quantify PCE and TCE reactivity and product formation as a function of temperature and system properties

• Assess the survival and activity of native, pure, and mixed consortia of dechlorinating bacteria at elevated temperatures

• Evaluate the destruction and recovery of PCE and TCE during laboratory-scale thermal treatment of field-contaminated soils

Investigate physical, chemical and biological processes governing thermal remediation of DNAPL source zones

13

C C

Cl

ClCl

Cl

C C

H

ClCl

Cl

C C

H

ClCl

H

C C

H

ClH

H

tetrachloroethlyene trichloroethylene cis-1,2-dichloroethylene vinyl chloride

H2ORadical Chain

C CY

Y

Cl

Y

O O

dioxetane

Unique Intermediate

Reactive Species

peroxyl radical

Elimination-Addition

HS-, HO-, HPO42-, HCO3

-, SO42-, NO3

-, H2O

C CY

Y

Cl

chlorovinylic anion

C CY Cl

chloroacetyleneIntermediate Products

C O

Cl

Cl

C O

C CH

Y

Cl

Y

O

C CH

Y

Cl

Y

O+

phosgene

epoxide acetyl chloride

O C O

C CHO

Y

YHO

C CHO

OH

HHOglycolic acid

T > 70oC

C CH

Y

Cl

Y

O

chloroacetyl chloride

H2O

+

chloroacetic acid

Parent Compounds

+ +

+

O2T > 70oC

Aqueous Phase Products

Gas Phase Products

Final Products

C C

Cl

Cl

H

Cl

Cl

O O

H2O or H3O+ ?H2O

O2

HCl

Y = Cl or H

OCH

HO

formic acid

+

CCH

Cl

Cl

Cl

CCCl

Cl

Cl

Cl

dichloroacetyleneClC CCl

chloroacetyleneClC CH

acetylene

HC CH

CCH

Cl

Cl

H

trans-DCE

CCH

Cl

H

Cl

cis-DCE

CCH

H

Cl

Cl

1,1-DCE

CCH

Cl

H

H

vinyl chloride

CCH

H

H

H

SRE1 Hs

Hs

EHs

Hs

Hs

Hs

SRE1

H-donor

Cl-2Cl-

Hn

Hn

Hn

C2H6ethane

PCE

TCEH-donor

HClE1cb

E1cb

E1cb

C C C C

H

H

H

H

H

H

H

H

1-butene

Hn + coupling

+cis- and trans-butene, and butadiene

SRE1

Complex Reaction Pathways-PCE/TCEOxidation Reduction

Experimental SystemsVOA vial 50 mL Ampule Microcosm-Ft Lewis Flow-Thru Reactor

1 m ERH Column

Chemical Reactivity of TCE and PCE in Heated Three-Phase Systems

Flame seal

Gas Headspace

50 mL Ampules

Solids

Aqueous Phase

Pressure Transducer

Compressed Dry Carrier Gas

MKS 179AMass Flow Meter

TCE via syringe pump

Water and Pre-MixController

25 to 100oC

Tube Oven Controller

30 to 1200oC

Tube Oven

DCM Trap Aniline Trap

Tedlar Bag

Ottawa Sand Ampule Reactor(deionized water, 1% goethite, and argon headspace)

Initially, less than 5% of TCE transformed after 300 days at 120oC

Reaction products included CO, CO2, glycolate and formate

TCE half-life decreased from 330 to 40 days with addition of 1% geothite to reactor

Costanza et al., 2005, ES&T

0

20

40

60

80

100

0 100

200

300

400

500

600

700

800

900

Reactor Temperature (oC)

Per

cent

of T

CE

Rea

ctan

t (%

)

TCE sand filled reactorPCE sand filled reactorTCE empty reactorPCE empty reactorTCE Yasuhara et al., 1990PCE Yasuhara et al., 1990

Ottawa Sand Quartz Reactor(TCE-saturated nitrogen gas influent stream)

Substantial conversion of TCE PCE and other chlorinated byproducts above 400 oC

Soil and Groundwater Samples

Fort Lewis, WAEast Gate Disposal Yard

Maywood, CAPemaco Superfund Site

West Fargo, NDCamelot Dry Cleaners

Great Lakes, ILNaval Training Center

Ottawa, IL20-30 mesh Ottawa Sand

Field Site Location Soil Type Contaminant

Camelot Cleaners Superfund Site West Fargo, ND Clay PCE

East Gate Disposal Yard,DNAPL Area #3 Fort Lewis, WA

Glacial Outwash (Gravel to

Clay)

TCE

Great Lakes Naval Training Center, Site 22 Great Lakes, IL Silty Clay PCE

Pemaco Superfund Site Maywood, CA Silty Sand TCE

Field-Contaminated Soil Samples

Camelot Cleaners, Fargo, NDFort Lewis, WA (EDGY)

ERH Field Sites

Camelot Dry Cleaners, ND(low permeability clay soil contaminated with PCE)

PCE half-life > 7000 days at 95oC

TCE half-life of 157 days at 55oC and 26 days at 95oC

Costanza and Pennell, 2007, ES&T

Fort Lewis, WA(high permeability soils contaminated with TCE)

TCE completely transformed to cis-DCE by halorespiringbacteria at 25oC

TCE recovery increased with increasing temp.

Chloride evolution indicates TCE half-life of 1.8 years at 95oC

Costanza et al., 2009, ES&T

Great Lakes, MI(low permeability soil contaminated with PCE)

PCE levels increased 2-3 fold with increasing temperature

Chloride levels were relatively constant at 300 mg/L

Negligible PCE degradation after 185 days at 95oC

Pemaco, CA(medium sand to silt contaminated with TCE)

TCE levels steady over 190 days at temps up to 95oC

Chloride levels constant, no intermediate products detected

Negligible TCE degradation after 190 days at 95oC

Field Site 25oC 50oC 70oC 95oC

Camelot PCE (parent) CO2

CO2 TCE

CO2TCE

CO2, CO, c/tDCE, TCE, 1-butene, benzene, furan

Fort Lewis TCE (parent)

cis-DCE (parent)CO2 CH4

CO2 , CO, CH4, acetylene, ethene, ethane

NACO2, CO, CH4,

acetylene, ethene, ethane

Great Lakes PCE (parent)TCE (parent)

cis-DCE (parent)

CO2, TCA CO2 CO2

CO2, CO, CH4, acetylene,

ethene, ethane, 1-butene

PemacoTCE (parent) CO, CO2 CO, CO2 CO, CO2

CO, CO2, 1-butene, furan

Formation of Reaction Products

Reaction Products ≠ Parent Reactivity Soil Degradation

PV vs Cleff

Volume Water Through Column (L)0 5 10 15 20

Gas

Pha

se (%

)

0

5

10

15

20

25

30

Sour

ce Z

one

Tem

pera

ture

(o C)

20

40

60

80

100

120

H2

CO2

• Great Lakes soil treated with ERH Heated to 74 oC,

• PCE increased from below the 0.2 mg/L detection limit to 106 ± 16 mg/L after heating

• Gas phase samples measured hydrogen, carbon monoxide and carbon dioxide

• Slight increases in gas production following heating from 88 to 100oC and from 88 to 95oC

• Potential for ED formation to support reductive dechlorination

Thermal Treatment (ERH) + Bioremediation(PCE-contaminated Great Lakes Soil)

42% increase in total PCE mass recovery compared to ERH alone (after 20 L of water)

CO2 and Cl increased after each persulfate injection; 4.8% of PCE recovered from column was oxidized

Increase in PCE Mass Recovered Cumulative PCE Mass RecoveredWater Through Column (L)

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

PC

E (m

g)

0

100

200

300

400

500

600

InitiateHeating

7 g/L persulfateERH + Persulfate

ERH

313 mg

447 mg

Water Through Column (L)0 2 4 6 8 10 12 14 16 18 20 22

Incr

ease

in M

ass

(%)

0

10

20

30

40

50

607 g/L persulfate

InitiateHeating Increase from heating

Thermal Treatment (ERH) + Persulfate(PCE-contaminated Great Lakes Soil)

Costanza et al., 2010, ES&T

Microbial Reductive DechlorinationMultiple species dechlorinate PCE and TCE to cis-DCE, but only

Dehalococcoides can transform cis-DCE and VC to ethene

0.2 µmDehalococcoidessp. strain BAV1

Dehalococcoides sp. strain H10, strain VS, strain KB-1/VC

He et al. 2003. Nature. 424:62

Geobacter sp. strain SZ

Sulfurospirillum, Desulfitobacterium,Dehalobacter, Enterobacter, Clostridium, Desulfuromonas

0.2 µm

PCE TCE cis-DCE VC ETH0.2 µm

Microbial Reductive Dechlorination at 30oC

0

3

6

9

12

15

18C

once

ntra

tion

(μm

ole/

bottl

e)

Incubation Time (Days)

PCE

TCEcDCE

VC

Ethene

BDI-30ºC

Complete dechlorination of PCE to Ethene at 30ºC

PCE to cis-DCE pure cultures: Desulfuromonas michiganensis strain BB1 and Geobacter lovleyi strain SZ

PCE to Ethene mixed cultures: Bio-Dechlor INOCULUM™ (BDI) and OW (Rice)

Reductive Dechlorination at 35oC and 40oC

0

3

6

9

12

15

18

0 10 20 30 40

0

3

6

9

12

15

18

0 20 40 60 80

PCETCEDCEVCEthene

Incubation Time (Days)Incubation Time (Days)

Con

cent

ratio

n (μ

mol

e/bo

ttle)

BDI-35ºC BDI-40ºC

Persistence of PCE and Accumulation of Vinyl Chloride at 40ºCAccumulation of Vinyl Chloride at 35ºC

Fletcher et al., 2011, ES&T

CultureTemperature (Degrees C)

24 30 35 40 45

Pure Cultures

SZ cis-DCE cis-DCE cis-DCE cis-DCE ND

BB1 cis-DCE cis-DCE cis-DCE ND ND

Mixed Cultures

BDI Ethene Ethene VC ND ND

OW Ethene Ethene VC VC ND

ND = No Dechlorination= Dechlorination ceased after 1 month

Summary of Pure and Mixed Culture Response to Elevated Temperature

Concluding Thoughts

Abiotic TCE and PCE degradation is generally slow at temperatures less than 120oC, but can be greatly improved in the presence of catalysts (e.g., Fe-containing minerals) and at higher temps (200-400oC).

Microbial reductive dechlorination ceases at temperatures above 40oC, but can be recovered with bioaugmentation and biostimulation, and thermal treatment can release/produce ED.

Substantial sorbed-phase contaminant mass may persist in fine-textured soils even after thermal treatment, but oxidants can enhance rates of contaminant recovery and reactivity.

Project ER-1419 Project ER-2129

Acknowledgements

Kelly Fletcher (Georgia Tech)

Jed Costanza(U.S. EPA)

Graduate Student Fellowship

Frank Löffler(Tennessee)

Ground Water and Ecosystems RestorationR-82947401-0

Natalie Capiro(Tufts)

Tyler Marcet(Tufts)