Biogeochemical Reductive Dechlorination

of Chlorinated Solvent Plumes

Status of Practice Shift from Biotic

to Abiotic Degradation Pathways

Presented by James E. Studer, M.S., P.E

Managing Principal, The InfraSUR Team

Albuquerque, New Mexico, USA

RemTech 2012

Fairmont Banff Springs, Alberta October 17-19, 2012

Presentation Objectives

Using Dover AFB National Test Site case histories, compare engineered

biotic reductive dechlorination to engineered iron sulfide dominated

biogeochemical reductive dechlorination (BiRD)

Speculate on where the field practice of engineered in-situ reductive

dehalogenation is headed

Black FeS enriched

sand mixed with

gravel (originally

red/orange colored)

Base confining clay

(no change)

Source: OnMaterials.com

Highlight abiotic, biotic, and biogeochemical

reductive dechlorination process discoveries and

commercial developments for engineered in-situ

reductive dehalogenation of chlorinated aliphatic

hydrocarbons such as PCE, TCE, and TCA

AFCEE

Milestones In Dehalogenation S

ween

ey,

19

80

Cu

0/F

e0

Gil

lha

m,

1990

ZV

I (F

e0)

Tra

tnyek

, 1

99

4 Z

VI/F

e O

xid

es

Kri

eg

ma

n-K

ing

, 1994

Py

rite

Ferr

ey

& W

ilso

n,

20

02

Ab

ioti

c M

NA

Lee &

Batc

helo

r, 2

00

2 P

yri

te /

Mag

n.

EZ

VI 2

00

3

Ken

ned

y,

20

05

BiR

D

Zh

an

g 1

997

, N

an

o-F

e

Batc

helo

r, 1

99

8 Z

VI/C

lay

ZVI

DVI

Biogenic

.

Modified from R. Brown, May 2012

Kle

cka

& G

on

sio

r, 1

98

4

Org

an

o-M

eta

llic

Co

mp

lexs

1980 1990 2000 2010

A-1981-1983 Initial Discovery (Roberts, et. al., Bouwer & McCarty)

B-1994-1995 Molasses, High Fructose CS used in practice

C-1996 Dehalococcoides (DHC) Maymo-Gatell et. al

D-1999 AMIBA Protocol Paper, Kennedy and Everett

E-2002 AFCEE/ESTCP Technical Protocol for Using Soluble Carbohydrates

F-2007 AFCEE Protocol Insitu Bioremediation of Chlorinated Solvents Using Edible Oil

G-2008 AFCEE Technical Protocol for Enhanced Anaerobic Bioremediation using Pemeable Mulch Biowalls and Bioreactors

A C B D E F G

Biotic

BiRD Basics Biogeochemical Reductive Dechlorination (BiRD) is a

patented process for the treatment of chlorinated solvents and certain metals [Kennedy - US Patent Off. #6,884,352 B1]

Basis for BiRD is: Typical clastic aquifers have much native iron and can be

supplemented if necessary

But, this iron is not reactive and can’t treat CAH’s

BiRD stimulates natural bacteria to convert native Fe to FeS minerals

FeS facilitates the complete autoreduction of CAH compounds similar to zero valent iron (ZVI).

BiRD is focused on engineered in-situ iron sulfide reaction zones and the abiotic reactions with contaminants

No desired role for enhanced biological reductive dehalogenation

Aquifer Environment

Natural mineral Fe is one of the most

common earth elements found in all

clastic sediments

Typical aquifer matrix has 0.1 to 10%

Fe or 4 to 400 lbs/m3

This iron is well dispersed and often as

poorly crystalline grain coating

Most native Fe minerals are Fe(III),

stable, and not effective against

CAH‘s

Native Fe can be converted to a

reactive mineral form via biochemical

reactions

SEM Normal Fe3+ coated sand grain

SEM Normal Fe3+ removed showing quartz

BiRD Functional Steps:

Phase 1 - Biological Step:

Supplied organic + sulfate stimulate common sulfate reducing soil bacteria:

CH2O + ½ SO4

2- HCO3 + ½ HS- (ag) + H2O + H+

Phase 2: Geochemical Step:

HS- from SRB respiration reacts with native or supplied mineral Fe II or III to produce FeS:

3HS- + 2FeOOH (s) 2FeS (s) + So + H2O +3OH-

Phase 3: Dechlorination Step:

Reactive FeS reductively dechlorinates CAH abiotically:

4/9FeS + C2HCl3 + 28/9 H2O 4/9 Fe(OH)3 + 4/9SO4

2- + C2H2 + 3Cl- + 35/9H+

With FeS surface area, CAH treatment usually begins

within 2 – 3 weeks or sooner.

Begins in days

Instantly

CAH treatment

half life 30 ± 15

days

Microbial Production of FeS in Microcosm

Microcosm consists of native sediment, added SO42-, and low carbon

organic acids. These results were reported in Kennedy and Everett, 2001.

0.0

32

64

96

128

160

192

224

256

288

320

0 2 4 6 8 10 12

Time (Weeks)

S (

mg

/Kg

)

S as (FeS)

S as (FeS2)

BiRD Response in the Lab

Dechlorination of TCE by reaction with mineral FeS

Treatment is rapid and complete – no DCE production

TCE

Acetylene

cis-DCE

0 500 1000 1500 2000 2500

2

4

6

8

1.0

1.2

1.4

1.6

Hours

Co

nc. (m

Mo

l/L

)

Butler and Hayes, Environ. Sci. Technol. 1999, 33, 2021-2027

1.6 mMol/L = 210 mg/L

0.2 mMol/L = 26.3 mg/L

2500 hours = 104 days

FeS forms a permeable reactive zone into which aqueous CAHs may flow.

Dechlorination is complete and dechlorinated products are mineralized to CO2.

Ground Water Flow Direction

Fe3+

Fe3+

Fe3+ Fe3+

Fe3+ Fe3+

Fe3+ Fe3+

Fe3+

Fe3+

Fe3+

TCE Plume

Fe3+

Fe3+

Fe3+

Fe3+

Fe3+

Fe3+

Fe3+

Water Table

Organic Solution + SO42-

FeS

FeS FeS

FeS

FeS

FeS

FeS

Mineral FeS Reactive Barrier

BiRD Application by Injection

Ground Water Flow

Trench

Groundwater CAH

BiRD Application by PRB

Ba

ckfill

Ma

teria

l

Solid reactants form solid FeS so is mostly “invisible” to aqueous monitoring.

FeS forms in the trench and down-flow gradient

FeS

FeS

FeS

FeS

FeS

FeS

Case History

Dover AFB National Test Site

Biogeochemical Reductive Dechlorination

(BiRD) Pilot

with Comparison to

Biological Reductive Dechlorination Pilot

BiRD Reactive Zone Created Using

Aqueous Injections

BiRD was tested next to bioremediation test plot at the

Dover AFB National Test site

Bioremediation was stimulated with emulsified vegetable oil

BiRD was stimulated by injection of Mg SO4۰7H2O (Epsom

salt) and Sodium lactate (Envirolac™)

For BiRD sediment was sampled pre and post injection to

measure FeS development

Bioremediation

Test Site

(Emulsified VegOil)

BiRD

Test Site

BiRD Site Map

Injection

Wells Down

Gradient

Example Well

MWs and

Line of

Section

Dover AFB TCE plume, test site location and injection layout schematic

Profile of mineral FeS development (mg/Kg as S) and example photo of sediment core with FeS.

ESM1 ESM2 ESM3 ESM4 ESM5ESM6

0

5

10

15

20

25

30

35

40

45

Fine sand grading to

coarse with depth

Fine sand grading to coarse sand with depth

Medium to fine sand with clay

Gravel

Gravel

Fine sand grading to

coarse with depth

Fine Sand Gravel

Fine sand grading to

coarse with depth

Gravel

Clay

Clay Confining Layer

Land Surface

DE

PT

H S

CA

LE

(F

T)

V

ER

TIC

AL =

HO

RIZ

ON

TA

L 1.39

1.86

2.00

1.75

9.99

12.58

5.87

6.18

78.91

3.00

1.43

1.67

2.72

1.79

1.44

5.46

3.23

7.70

112.83

38.83

2.04

1.16

4.15

2.26

2.87

1.79

1.41

1.40

1.80

1.75

2.22

0.27

1.77

11.71

66.47 84.08

0 5 10 20 40 80 160

FeS (mg/Kg)

Black FeS enriched

sand mixed with

gravel (originally

red/orange colored)

Base confining clay

(no change)

Line of 5 Injectors Perpendicular to Profile

Comparative CAH Treatment Response

Bioremediation response

(right) showed decreasing

TCE but increasing DCE

and VC

15 feet down gradient from injector

0

200

400

600

800

1000

1200

1400

1600

0 50 100 150 200 250 300 350Days After Injection

Co

ncen

trati

on

(u

g/L

)

TCE

cDCE

VC

TCE: Decreasing

DCE: Increasing

VC: Increasing

Exchanging One Contaminant for Another0

200

400

600

800

1000

1200

1400

1600

-25 0 25 50 75 100 125 150 175 200 225 250Days

TC

E a

nd

VC

(u

g/L

) a

nd

TO

C (

mg

/L)

0

1000

2000

3000

4000

5000

6000

DC

E (

ug

/L)

an

d S

O4

(mg

/L)

Injection Date

SO4

TOC

TCE

VC

DCE

BiRD response (left)

showed complete treatment

of TCE and DCE with no

daughter products.

BiRD was rapid and

complete

BiRD Tested by Solid Permeable Reactive

Barrier (PRB)

BiRD was tested in

an “apples to apples”

with bioremediation

using PRB approach

Bio used municipal

mulch as organic &

sand for weight

BiRD also used

municipal mulch &

sand but added

crushed gypsum

(CaSO4) for sulfate.

MW11

MW01

MW02

MW03

MW04

MW05

MW10

MW09

MW08

MW07

MW06

MW12

MW013MW012

NORTH

0 25 50 feet

Monitoring

Well

Reactive Barrier

LEGEND

Bioremediation

Side

BiRD

Side

Soil Sample

Line of Profile

Comparative CAH Treatment Response

BiRD (top) showed

rapid and complete

treatment of PCE,

TCE & DCE

Bioremediation

(bottom) showed

TCE transformed to

DCE with no net

treatment

0.00

5.00

10.00

15.00

20.00

25.00

0 50 100 150 200

days

CA

H (

ug

)

, PCE

TCE

1,1DCE

cDCE

tDCE

VC

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

0 50 100 150 200

days

CA

H (

ug

)

, PCE

TCE

1,1DCE

cDCE

tDCE

VC

EPA Independent BiRD Testing

EPA Kerr Lab tested BiRD for over a year (H. Shen and J. Wilson)

Two column experiments made with cotton seed (organic) mixed with sand & sand with hematite (natural iron)

Ground water was pumped at normal velocity with: 1500 mg/L sulfate 2000 ug/L TCE 10 ug/L residual DCE

During the experiment aqueous samples were obtained: Before the mulch mix column After the mulch mix column After the aquifer sediment column

EPA’s study showed that:

• The 2000 ug/L flowing into the BiRD treatment columns was

treated to 99.9% in both treatment test cells.

• No daughter products were generated.

0.1

1

10

100

1000

10000

0 50 100 150 200 250 300 350 400

Operation Days

TC

E,

µg

/LHematite- & limestone-added biowall effluent

Hematite-added biowall influent

Hematite- & limestone-added biowall influent

Hematite-added biowall effluent

MCL

TCE flowing in

TCE flowing out

99

to99.9

%Tre

atm

en

t

BiRD Costs

BiRD will typically be the least expensive treatment option

compared to bioremediation and ZVI

Similar dependency on quality site characterization and

subsurface engineering

Fewer optimization concerns – bioaugmentation, carbon

maintenance, low pH

Injectable BiRD can use bulk organic and fertilizers for

< $1.5/lb (< $3.30/kg)

Trench-based PRB BiRD can use municipal yard waste and

bulk sand/gypsum ranging in cost from free to about

$50/yd3

Main BiRD Advantages:

Flexibility in application (trench-based and direct injection)

Is a natural process enhanced by engineering design

Reagents need not be continuously applied as solid

phase FeS remains

Reservoir permeability is not adversely affected

Reacted FeS oxidized Fe + S can be cycled back into

FeS again

CAH treatment is complete with virtually no daughter

product generation

CAH treatment similar to ZVI with half life of 30 days ±15

BiRD is low cost so even large plumes could be treated

economically

Looking Ahead:

Consistent success in subsurface remediation is challenging

and requires competency in several areas:

Subsurface Characterization / Conceptual Site Modeling (50%)

Treatment Technology Selection (20%)

Subsurface Engineering (30%)

While engineered approaches based on abiotic

dechlorination pathways (e.g., ZVI and BiRD) offer intrinsic

advantages, the future will favor technology promoted by

solution providers that demonstrate “50-20-30”

competency.

Thank You

James E. Studer, M.S., P.E

Managing Principal, The InfraSUR Team

Albuquerque, New Mexico, USA

505-858-3136

505-463-6175

jstuder@InfraSUR-LLC.com