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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
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