WI080040_Monitoring (Report)_20020329

Technical Data Summary
for
Reductive Anaerobic Biological In Situ Treatment Technology
(RABITT) Treatability Testing
at
Camp Lejeune
Site 88
by
Battelle Memorial Institute
505 King Avenue
Columbus, Ohio 43201
March 29, 2002
OjK
N�
i

Contents
FIGURES
TABLES
1.0 Introduction
2.0 Pre -Demonstration Activity
2.1 Bromide Tracer Testing
3.0 Sampling
4.0 Camp Lejeune RABITT Test Results .
4.1 Chloroethene Concentration Profiles
4.1.1 Tetrachloroethene . _
4.1.2 Trichloroethene
4.1.3 cis-Dichloroethene
4.1.4 Vinyl Chloride
4.2 Dissolved Gasses ._
4.2.1 Ethene
4.2.2 Hydrogen
4.3 Organic Acids .
4.4 Inorganics
4.4.1 pH and Alkalinity
4.4.2 Nitrate, Nitrite, and Ammonia
4.4.3 Sulfate
4.4.4 Chloride
4.5 Dissolved Organic Carbon
5.0 Conclusions
Figures
Figure 1. Plan View of RABITT Demonstration Site
Figure 2. Bromide Tracer Testing Contour Plots
Figure 3. PCE Injection Concentration
Figure 4. PCE Concentration (µM) Contour Plots
Figure 5. TCE Concentration (µM) Contour Plots
Figure 6. cis-DCE Concentration (µM) Contour Plots
Figure 7. Vinyl Chloride Concentration (µM) Contour Plots
Figure 8. Ethene Concentration (µM) Contour Plots
Figure 9 Average Dissolved Ethene, Ethane, and Methane Concenti-�
Figure 10. Average Organic Acid Concentrations
Figure 11. Average Field pH and Alkalinity Concentrations _
Figure 12. Average Nitrate, Nitrite, and Ammonia Concentrations..
Figure 13. Average Sulfate Concentrations
Figure 14. Average Chloride Concentrations
Figure 15. Average Dissolved Organic Carbon Concentrations .......�

1.0 Introduction
The Reductive Anaerobic Biological In situ Treatment Technology (RABITT) demonstration at Camp
Lejeune was the fourth in a series of Environmental Security Technology Certification Program
(ESTCP)-funded demonstrations completed at Department of Defense (DoD) sites around the country. At
each of the four sites, a draft protocol was implemented to determine if microbially-catalyzed reductive
dechlorination of chloroethenes could be stimulated in situ. The overall objective of the program was to
assess the utility of the draft protocol in its current form and revise the protocol based on field experience.
Because the project's primary objective was refining the draft protocol, only one final technical report
was planned and no funds were allocated to provide test facilities with site -specific reports. However, in
deference to the facilities that generously hosted the demonstrations we wanted to provide base personnel
with a complete description of the field activities and a full set of the data collected from their site. This
informal document has been prepared to provide base personnel with a description of field activities and
results.
1

2.0 Pre -Demonstration Activity
Field activity was initiated at Camp Lejeune on October 25, 2000 with the collection of aquifer cores and
groundwater for use in a laboratory microcosm study. Mud -rotary drilling was used to advance three
boreholes in the vicinity of existing monitoring well88-MW05IW. A 2-in diameter core barrel lined with
acetate sleeves was used to collect aquifer material from 11-15 ft bgs and 45-49 ft bgs from each of the
three boreholes. In addition, five liters of groundwater was collected from monitoring wells 88-MW05
and 88-MW051W. Microcosm studies were conducted at Cornell University. (Data not shown.)
The installation of the RABITT demonstration system began on April 17, 2001. A total of 12 wells were
installed with screened intervals ranging from 45 to 48 ft bgs. Three wells, designated MW-1, MW-3,
and MW-4, were installed using a 3.25-inch inner diameter (ID) hollow stem auger. The remaining 9
wells were installed using mud rotary drilling. A polymeric drilling fluid additive, Insta-VisTM Plus, was
used to prevent the collapse of the borehole during installation of these wells. This material, which had
the consistency of syrup, was present in purge water for several weeks following well installation despite
assurances from the driller that it would biodegrade within 48 hours. Well installation was completed on
April 22, 2001.
Two existing wells were used during the demonstration. The first, designated 88-MW05IW, exhibited
consistently high levels of PCE and was used to supply contaminated groundwater for the demonstration.
The second, designated 88-MW03IW, was used to collect background samples. Table 1 outlines well
specifications. The relative locations of system wells are shown in Figure 1.
Table 1. Well SEiecifications
Parameter
Injection
Wells
Monitoring Wells
88-MW05IW
88-MW031W
_
Number of wells
3
9
1
1
Diameter (in.)
0.75
1
2
2
Screened Interval (ft bgs)
45-48
45.75-47.25
45-50
45-50
Slot Size (in.)
0.01
0.01
0.01
0.01
1 Material
Sch 80 PVC
Sch 80 PVC
Sch 40 PVC
Sch 40 PVC
2.1 Bromide Tracer Testing
Following the installation of system wells a bromide tracer test was initiated on May 11, 2901 to
determine the direction of groundwater flow through the monitoring well array. A review of existing
groundwater potentiometric contour maps led us to believe that the general movement of groundwater in
this area would be to the northwest, but tracer -testing results would contradict that assumption.
Groundwater was continuously pumped from monitoring well88-MW05IW and amended with a
concentrated sodium bromide solution in the on -site field trailer. A calibrated metering pump was used to
add a consistent amount of bromide stock solution to the groundwater flow. After amendment with
bromide stock solution, the flow was evenly split and injected into injection wells IW-1, IW-2, and IW-3.
The target bromide concentration for injected water was 100 mg/1. The bromide stock solution was
prepared by adding 3.038 kg of NaBr to 15 gallons of tap water. Flow rates and concentrations are
presented in Table 2.
2

•
O
0
M
Field Trailer
Figure 1. Plan View of RABITT Demonstration Site

Cable 2. Tracer Testin Flow Rates and Concentrations
0 erational Parameter
Initial Design (May)
Modified Design {June)
Total pumping rate from 88-MW05IW
1.8 1/min
0.6 1/min
Bromide stock solution feed rate
4.34 ml/min
1.44 ml/min
Bromide stock solution concentration
41,550 mg/L as MI]
41,550 mg/L as jBr ]
Bromide concentration of injected water
100 mill
100 mg/1
Wells used for injection
IW-1, IW-2, IW-3
MW-5
After four days the bromide concentration in the monitoring wells closest to the injection wells had
increased far less than expected. In addition, there was evidence that bromide levels might be increasing
in the supply well (88-MW05IW). This prompted a shutdown of the tracer test and a reexamination of
water levels within the monitoring well array. Because the monitoring wells are located so near each
other it was difficult to measure significant differences in water elevation; nonetheless, water level
measurements did suggest that the primary direction of groundwater flow might be to the northeast. DOC
measurements suggested that residual drilling fluid was present on the northwestern side of the plot. It is
possible that this residual drilling fluid may have decreased hydraulic conductivity within the monitoring
well array and impacted local groundwater movement.
Tracer testing was restarted on June 22, 2001, but with a modified design. For this second phase of
testing the bromide amended groundwater was injected into the MW-5, in the center of the monitoring
well array. This strategy was used to ensure the movement of tracer could be observed regardless of the
direction of groundwater flow. Because the number of injection wells had been reduced from three to
one, the injection flow rate was reduced from 1.8 1/min to 0.6 1/min, and the bromide stock solution feed
rate was reduced from 4.3 ml/min to 1.4 ml/min. Figure 2 shows a time series of contour plots, which
illustrate the movement of bromide through the testing zone. Plots were generated using data collected in
the field with an OrionTM 290A field meter and a bromide -specific electrode.
The first contour map in Figure 2 shows data collected three days prior to initiation of the June 22 tracer
test. These data show that bromide from the May 18 tracer test was still present in the injection wells IW-
1, IW-2, and IW-3, and that bromide had begun to impact monitoring wells MW-2, MW-3, and MW-5.
Subsequent contour maps show the radial movement of bromide from MW-5, which served as the point
of injection for the tracer test initiated on June 22.
Despite the fact that bromide was being injected at only 100 mg/L, the concentration of bromide
measured in the plot using the bromide -specific electrode was considerably higher. Because laboratory
measurements did not corroborate these elevated concentrations, and because the bromide concentration
in the supply well remained consistently low (<3.3 mg/L) throughout the demonstration, it is suspected
that the bromide -specific electrode provided artificially high bromide values due to the presence of
interfering ions. The manufacturer lists seven ions capable of interfering with the bromide -specific probe,
but only ammonia (NH3) and sulfide (S"2) are likely to have been present at concentrations high enough to
cause interference. In addition, the suspiciously high bromide concentrations were only observed after
the injection of electron donor, and only in areas with very low redox potentials, which is exactly where
one would expect to see the formation of ammonia and sulfide. Although the specific bromide
concentration data in these areas appear to have been compromised, the data do provide an indication that
these areas were highly reduced and were probably impacted by the addition of electron donor.
Assuming an in situ bromide concentration of 100 mg/1, the maximum allowable NH3 and S-2
concentrations are 4.3 x 10-2 mg/1 and 4 x 10- mg/1, respectively. Ammonia concentrations ranging up to
1 mg/1 were observed within the boundaries of the test plot. Sulfide ion measurements were not made.
4

IW-1
•
Figure 2. Bromide Tracer Testing Contour Plots
MW-1
•
MW-4
•
I 2$ MVE2 (---1 / • M s -5 N MW-8
ni
IW-3 MW-3 j" MW-6 MW-9
• • • •
Samples collected on June 19, three days prior to initiation of second tracer test
MW-7
•
MW- 1
•
o
M W e, `x / , MW 5, to c.0
\ iv 0) •
cry • I
•
MW-4
Ms-6
Time Zero (No samples collected from outlying wells)
IW-1
• r J
IW-2 o MV %
• r •
IV L
3 days
IW-1 MW-1
• SZ—-J!
!W.-2s MW-2 •
• \ ` • �/
I
•
25 days
•
W-2 u a
* 4r] r--
IVV 3 v 'IIVV 3
• •
48 days
n
(J
O
MW-4
•
MW-5 LO
o
•
M W-6
•
MW-8
•
MW-8
•
MW-7
•
MW -9
MW-4 MW-7
, -s• \ \ •
OS L
Mi-5 , ca M+-8 ek
MW-6 \ - MW-9
MW-1 MW-4 MW-7
•
MW �� -5 ' M W -80
M W-5 MW-9M
5

3.0 Sampling
Sampling began on May 16, 2001 with the collection of baseline samples. Table 2 shows the sampling
schedule and the types of samples that were collected/analyzed. Table 3 lists the analytes for each sample
type.
Ta
Ta
tole 3. Sampling Dates and Sample Types
Date
Elapsed Time
(Weeks)
Field Data
VOCs
Dissolved
Gases
VFA
Data
Inorganic
Data
DOC
H2
16-May-01
(pre -injection)
19-Jun
X
X
X
X
X
25-Jun-01
(injection begins)
X
X
X
X
X
X
21-Jun
17-Jul-01
3
X
X
07-Aug-01
6
X
X
X
X
X
X
28-Aug-01
9
X
X
02-Oct-01
14
X
X
Not Analyzed
X
X
X
X
23-Oct-01
17
X
X
13-Nov-01
20
X
X
X
X
X
X
04-Dec-01
23
X
X
18-Dec-01
25
X
X
07-Jan-02
28
X
X
X
X
X
X
X
Field Data
VOCs
Dissolved
Gases
VFA Data
Inorganic
Data
DOC
H=
Water Level
PCE
Ethene
Lactic acid
pH
Dissolved
Dissolved
Redox
TCE
Ethane
Acetic acid
Conductivity
organic carbon
hydrogen
potential
cis-DCE
Methane
Propionic acid
Alkalinity
pH
VC
Butyric acid
Nitrate
Temperature
Nitrite
Bromide
Ammonia
DO
Chloride
Fe(II)
Sulfate
Bromide
6

4.0 Camp Lejeune RABITT Test Results
Results from the RABBIT demonstration at Camp Lejeune are presented in the following subsections.
Chloroethene concentrations are presented in a series of contour plots showing the spatial distribution of
contaminant in the test plot over time. The remaining analytical parameters are presented in graphs that
show the average concentration in the test plot over time. The data presented in these graphs represent
the average total concentration from Monitoring Wells 1 through 9 and Injection Well 2 (used as a
monitoring well). Data from the supply, gradient, and background wells were not included. Tables
containing the raw data are included in the appendices.
4.1 Chloroethene Concentration Profiles
The results for PCE, TCE, cis-DCE and VC are presented from selected VOC sampling events. Contour
plot concentration units are in µM to allow for direct comparison between the four compounds on an
equivalent basis. Results for trans-DCE, 1,1-DCE and other VOCs are included in the Appendix A.
4.1.1 Tetrachloroethene. PCE-contaminated groundwater was pumped from the supply well,
amended with electron donor solution and then injected into MW-5, which is located in the center of the
test plot. This injection strategy insured that contaminated groundwater within the plot was not simply
displaced with uncontaminated injection solution. Figure 3 shows the concentration of PCE measured in
samples collected from the supply well and from MW-5. The data suggest that the dechlorination of PCE
occurs very rapidly following injection.
30
25
7
5 15
aa
—00— Supply Well —B MW-5 (Injection Well)
No
injection
0
5 10 15 20 25 30
Time (Weeks)
Figure 3. PCE Injection Concentration
The disappearance of PCE within the test plot is illustrated in Figure 4, which shows a time series of PCE
concentration contours. The figure shows that pre -injection PCE concentrations (time zero) ranged across
the test plot from 18.1 µM (3000 ppb) to 53.8 µM (8,920 ppb), and that the degradation of PCE proceeded
relatively quickly following the initiation of electron donor injection. Injection was interrupted from
Weeks 11-14 due to a pump malfunction, so for the Week 14 samples no groundwater had been injected
for the previous three weeks. The PCE observed around MW-5 in the latter weeks of the demonstration
illustrate the constant influx of PCE-contaminated groundwater into MW-5.
7

Iw-1
•
IW-2
N 1
IW-3
•
Time Zero
4OIW-2
•
Figure 4. PCE Concentration (µM) Contour Plots
MW-1
•
MW-S�
MW-3
•
MW-4
■
MW-6
MW-1 MW-4
MW-5 -M
-/3 0 1 p\' f r I 2
_ • 3 I j 1►I i -6
MW-8
MW-7
fi
4�-9
•
3 Weeks
IW-1 MW-1
• h •
I :2 II MW-2: f
u+
I•3 1/ M;-3
6 Weeks
IW-1
IW-2
MW-2
■
MW-1
MW-4
■
MW-6
■
MW-4
• s
MW-5 ■ MW-8 �25
• -i
MW-7
MW-7
IW-3 MW-3 MW-6 MW-9
• • • ■
14 Weeks (all wells < 0.01 µM [2 ppb] except MW-7, no injection for previous 3 weeks)
IW-1 MW-1
■
IV2 MW-2
•
I W/-3 MW-3
•— •
20 Weeks
IW--1 MW-1
■
IVW-2 MW-2
• •
I V3 M W-s
23 Weeks
IW-1 MW-1
��I •2 M: 2
IV\'-3 M W -3 MW-6+
•
MW-4
- MW-8
■
cs.
MW-6
•
MW-4
MW-6
•
MW-7
s
MW-8
MW-4
M`-9
MW-7
•
MW-9
•
28 Weeks
11
MW-8
•
MW-7
M� 9
8

4.1.2 Trichloroethene. TCE was also present within the test plot prior to the injection of the nutrient -
amended groundwater solution, but at lower levels than PCE. Pre -injection TCE concentrations ranged
from 1.63 µM (201 ppb) to 5.19 µM (682 ppb). Figure 5 shows that as the demonstration progressed TCE
concentrations were significantly reduced throughout most of the test plot. Increases in the TCE.
concentration observed around MW-5 were caused by two factors. First, the injected nutrient -amended
groundwater consistently contained higher TCE concentrations than those observed initially in the test
plot; injection concentrations ranged from 8.37 µM (1,100 ppm) to 21.31 µM (2,800 ppb), except during
Weeks 11-14 when no injection occurred. The second factor was the continuous degradation of PCE to
TCE that occurred around MW-5. The Week 14 contour plot shows that reductive dechlorination
continues temporarily in the absence of nutrient injection.
Figure 5. TCE Concentration (µM) Contour Plots
IW-1 MW-1 MW-4
r T • •
MW-2 MW-5
Pre -Injection
I W-1
IW MW-
,•
I `3
Time Zero
IW-1
I W-1
MW-3
■
MW-1
M:=
MW-1
MW-6
M W-d
tiLIS
M W-6rh
MW-4
■
IW-2 MW-2 MW-5 MW-8
• • • ■
IW-3 MW 3 MW-6- M! 9
IW-1 MW-1 MW-4 MW-7
• • •
MW-7
MW-7
MW-7
• • •
14 Weeks (all wells < 0.02 µM [2 ppb] except MW-7, no injection for previous 3 weeks)
IVi-2 MW-2
• I
Iv
W 3 MW-3\
ii w
20 Weeks
� � 1
ir,
MW-5
�v+, f •
1
CYIf
MW-7
0
MW-9
•
9

Figure 5. TCE Concentration (µM) Contour Plots (cont'd)
IW-1 MW-1
■
IW-2 MW-2
•
I -3 M1N 3�,
28 Weeks
•
//'/
MW-5
MW-4 MW-7
•
MW-8
M W-9
•
4.1.3 cis-Dichloroethene. Figure 6 shows that cis-DCE was also initially present in the test plot with
concentrations ranging from 1.09 µM (106 ppb) to 17.74 µM (1720 ppb). Three weeks into the
demonstration cis-DCE levels had risen dramatically to greater than 80 µM in some locations. This
provides compelling evidence that reductive dechlorination of PCE and TCE was occurring since the cis-
DCE concentrations in injected groundwater never exceeded 22 µM (2133 ppb). It also suggests that the
reductive dechlorination of cis-DCE was occurring considerably slower than the dechlorination of its
parent compounds, resulting in its accumulation.
Iw-1
•
Time Zero
IW-1
•
IW-2 v
•
I V' -3
•
3 Weeks
IW-1
•
IW-2
•
3
•
9 Weeks
Figure 6. cis-DCE Concentration (µM) Contour Plots
MW '
•
MW-2
•
MW-1
•
MW-,
MW-4
MW-6
•
MW-7
•
M W-9
•
MW-1 MW-4 MW-7
• \� i
MW 5 ` •
o4.1
I1�►11-3
MW-1
•
M VV- 3
■
v
M W-5
•
MW-4
•
MW-9
•
MW-7
sr Es; G -
•
M V1Q5 -
• - •
IW-1 MW-1 MW-4 MW-7
• + ■ �!►
TO
IW-2 `. -le 6d ----- M1A/-5- .. - - MW-8
• • y' g4 •• �� • 60
p sQ 6TvlW-9MI'�-3�3O MW-6 I V1-3
20 Weeks
10

IW-3 a
28 Weeks
Figure 6. cis-DCE Concentration (µM) Contour Plots (cont'd)
MW-1 M W-4 M W-7
•
70
60 MW-5 M1N: B
•
M : -3 40 `r0 �a Nide . _ M W -9•
MW-1 M W-4
•
50
W-2 W.. 40 `, ;W 5-
- 30
tea
M.W-8
sQ
MW-7
-70J
4.1.4 Vinyl Chloride. VC was not initially present within the test plot (see Figure 7), nor was it
present in the injected groundwater that was obtained from the supply well. The absence of VC in the test
plot for the first 14 weeks of the demonstration shows that a considerable lag occurred before the
dechlorination of cis-DCE began. An examination of the cis-DCE and VC contour plots from Weeks 20,
25 and 28 reveals a strong spatial correlation between decreases in cis-DCE concentrations and increases
in VC concentrations. The production of VC and its correlation with decreasing cis-DCE concentrations
demonstrate that reductive dechlorination of cis-DCE was occurring within the test plot. Interestingly,
microcosms constructed from sediments in this area did not demonstrate dechlorination of cis-DCE. The
reason for this discrepancy is unknown.
I W-1
•
IV1'-2 MW-2 MW-5 MW-8
• ` • •
I VW-3 MW-3 MW-6
• • •
Time Zero through Week 14 (All wells < 0.08 µM [5 ppb])
IW-1 MW-1 MW-4
k
• •IW2 M W -2 M W-5 M W -8
•
1
IW-3 M W-3 MW-6
• • •
Week 17
I W-1 M W-1 M W-4
• - •
I Ukk-? z -2 ^ 5 M W-8
IU 31 MW-3 MW-6
•
Figure 7. Vinyl Chloride Concentration (µM) Contour Plots
MW-1 M W-4 MW-7
• • !
Mt/-9
Week 20
MW-7
MW-9
•
MW-7
•
M+-9
11

Figure 7. Vinyl Chloride Concentration (µM) Contour Plots (cont'd)
M W-1 MW-4 M W-7
s a
3 yp 7 -
iav-- —_~1 _ a v-5 _ - �- MW-8
•
-3 `�-���' � MW-169 MVN-9
r
Week 25
I W-1 M W-1 M W-4 M W-7
Iv _ 3o M1 -otrs
MW-9
Week 28
4.2 Dissolved Gasses
The dissolved gasses ethene, ethane, and methane were monitored during the field demonstration to
determine the extent of chloroethene degradation and assess the microbiological conditions within the
testing zone. Dissolved gas samples were collected only once every 6-8 weeks, and unfortunately, the
samples collected during Week 14 were not analyzed due to a laboratory error.
4.2.1 Ethene. Ethene was not detected in groundwater samples collected through the first 6 weeks of
the demonstration (see Figure 8). By Week 20 ethene had begun to appear in IW-2, which is the same
location VC was first observed. The correlation between VC and ethene would become evident over the
next eight weeks as the concentration and distribution of ethene continued to increase in locations that
showed the presence of VC. This observation supports the conclusion that chloroethenes can be
completely dechlorinated to a non -hazardous endpoint by native microbial flora.
Figure 8. Ethene Concentration (µM) Contour Plots
IW-1 MW-1 MW-4 MW-7
• • a is
IV1J-2 MW-2 MW-5 MW-8
■ i • a
I W-3 MW-3 M W-6 MW-9
a to • a
Time Zero through Week 6 (All wells < 2.4 µM)
IW-1 MW-1 MW-4 MW-7
a — * • a
1- "' MW-2 MW-5 MW-8
4j a 0 at
Iv MW-3 M W-6 M W-9
✓ a a
Week 20
12

Figure 8. Ethene Concentration (µM) Contour Plots (cont'd)
IW-1 MW-1 MW-4
• • •
N
EVV-2 - — • `'1?1W-2 MW-5 MW-8
• • + •
E VV-3 MW-3 MW-6
• • •
Week 23
MW-7
•
M -9
■
I W-1 MW-1 M W-4 MW-7
• • •
IV c•�tra
- W-2r MW-5• MW-8
11.41111 MW-3 M: 6 Mi-9
Week 28
Figure 9 shows the average ethene, ethane and methane concentrations across the test plot. Ethane
remained below the detection limit throughout the demonstration. Methane results show that
concentrations increased fairly rapidly and remained high through the end of the demonstration. Field
notes report the formation of bubbles in groundwater samples collected after Week 17. This observation
suggests that degassing was occurring and would tend to corroborate the high levels of dissolved methane
observed in the latter few weeks of the demonstration.
Methane (mg/L)
30,000
25,000
20,000
15,000
10,000
5,000
0 CI
0
5
—0— Methane — —Ethene —in-- Ethane
10 15
Time (Weeks)
6.0
- 5.0
4.0
3.0
2.0
1.0
❑ ❑ ❑ 0 0.0
20
25
30
Ethene and Ethane (uM
Figure 9 Average Dissolved Ethene, Ethane, and Methane Concentrations
13

4.2.2 Hydrogen. Dissolved hydrogen samples were collected three times during the demonstration
using the bubble -strip method. Samples were collected 4 days prior to injection, at mid -demonstration
(Week 14) and at the end of the demonstration (Week 28). Table 5 outlines the results and Table 6
provides a previously published correlation between dissolved hydrogen concentration and predominant
terminal electron accepting process. Although results did suggest that the subsurface environment was
highly reduced, they did not provide any diagnostic value. The unusually high dissolved hydrogen
concentrations observed prior to electron donor injection could not be explained, but may have been
linked to the impact of the residual drilling fluid. Despite these high hydrogen levels, methanogenesis did
not appear to be the predominant electron accepting process early in the demonstration (see Figure 9).
Table 5. Dissolved HN drogen Concentrations Across the Testing Plot
Monitoring
Location
Hydrogen Concentration OM)
Pre -Injection
Week 0
Mid -Demonstration
Week 14
Final
Week 28
IW-2
Not Sampled
6
2.3
MW-1
4
7
5.2
MW-2
2
41
3.7
MW-3
830
10
5
MW-4
21
8
5.3
MW-5
120
19
10
MW-6
410
10
7
MW-7
230
59
6.3
MW-8
130
29
4.9
MW-9
34
75
7.2
Table 6. Correlation of Dissolved Hydrogen Concentrations with
Terminal Electron-Acce»ting Process
Terminal Electron -Accepting Process
Hydrogen Concentration (nM)
Methanowenesis
> 5
Sulfate Reduction
1 to 4
Ferric Iron Reduction
0.2 to 0.8
Denitrification
< 0.1
Source: EPA 1998
4.3 Organic Acids
The concentrations of acetic, butyric, lactic, and propionic acids were tracked during the field
demonstration to ensure that sufficient butyric acid was being injected and to examine the fate of added
reducing equivalents. Figure 10 shows the average concentration of each of these acids within the test
plot. The injection concentration of butyric acid was 3,000 µM throughout the demonstration, except from
Week 11 to Week 14 when electron -donor injection was interrupted. The data show that a residual
concentration of butyric acid was maintained in the test plot and that acetic acid was the predominant
fermentation product.
14

2000
• 1800
d'
1600
c• g 1400
o
a a 1200
• 1000
u w 800
CO
O 600
u U
400
pq • 200
0
I —ate-Butyric Acid —0—Lactic Acid--♦-Propionic Acid (Acetic Acid
0
4.4 Inorganics
5
10 15
Time (Weeks)
20
25
Figure 10. Average Organic Acid Concentrations
4000
3600
3200
2800
2400
2000
1600
1200
800
400
0
30
Acetic Acid Concentration (uM)
Several inorganic species were tracked throughout the field demonstration, including: pH, alkalinity,
nitrate, nitrite, ammonia, sulfate, and chloride. Data for each of these species is described in the following
subsections and is presented in Figures 12 through 16.
4.4.1 pH and Alkalinity. Figure 11 shows that the average groundwater pH within the testing zone
remained relatively neutral despite the addition of butyric acid throughout the demonstration period.
Readings for pH were collected in the field prior to sample collection.
15

Alkalinity (mg/L)
500
450
400
350
300
250
200
150
100
Alkalinity —A— pH
0 5 10 15
Time (Weeks)
20
25
Figure 11. Average Field pH and Alkalinity Concentrations
8.0
7.5
7.0
6.5
6.0 0.
5.5
5.0
4.5
4.0
30
4.4.2 Nitrate, Nitrite, and Ammonia. Figure 12 shows that nitrate and nitrite concentrations were
initially very low in the test plot and remained low throughout the demonstration despite some minor
fluctuations. Ammonia levels were also fairly stable during the demonstration, but were found at
concentrations an order of magnitude greater than either nitrate or nitrite. These observations coupled
with field measurements showing the depletion of oxygen suggest that the plot had exhausted the electron
acceptors oxygen, nitrate and nitrite even before the demonstration began. Based on field measurements
of redox potential in the groundwater the terminal electron accepting process at the site was probably
sulfate reduction.
0.7
• 0.6
E 0.5
O
▪ 0.4
u 0.3
0
0
0.2
0.1
0.0
0
5
—0— NH3 NO3 — k — NO2
No
injection
10 15
Time (Weeks)
20
25
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
30
Figure 12. Average Nitrate, Nitrite, and Ammonia Concentrations
NO3 and NCk Concentrations
es
E
16

4.4.3 Sulfate. Figure 13 shows that sulfate reduction was likely occurring throughout the
demonstration period. Influent concentrations of sulfate from the supply well ranged from 24 to 35 mg/L.
By Week 28, the influent concentration was an order of magnitude greater than sulfate concentrations
elsewhere in the test plot.
Average SO4 Concentration (mg/L)
50
45
40
35
30
25
20
15
10
5
0
No
injeetiofl
0
5 10 15 20 25 30
Time (Weeks)
Figure 13. Average Sulfate Concentrations
4.4.4 Chloride. The reductive dechlorination process causes increases in local chloride levels as
chlorine atoms are sequentially removed from parent chloroethene compounds. Measurements of
chloride at the Camp Lejeune demonstration site showed an initial increase in chloride levels immediately
following the injection of electron donor. The increase in chloride concentration during the first 6 weeks
of the demonstration was about 6 times higher than expectations based on the average concentration of
chloroethenes injected into MW-5. This discrepancy could have resulted from the dechlorination of
chloroethenes sorbed to soils within the test plot and/or by the accumulation of injected chloroethenes
within the testing zone.
Midway through the demonstration chloride levels stabilized and then dropped off dramatically. The
pump failure that stopped injection of the nutrient -amended groundwater from Week 11 to Week 14
contributed to the lower rate of chlorine production that occurred between Week 6 and Week 14, but
cannot explain the subsequent declines in chloride levels. The reason for the dramatic decline in chloride
is unknown.
Chloride concentrations in both the background and supply wells remained relatively low. Background
concentrations remained between 4 and 7 mg/L and supply well concentrations ranged from 11 to 13
mg/L.
17

70
0 60
50
40
o0
E 30
20
R
L
10
0 5 10 15 20 25 30
Time (Weeks)
Figure 14. Average Chloride Concentrations
2000
1600
1200
800
400
0
Average Chloride Concentration (uM)
4.5 Dissolved Organic Carbon. Dissolved organic carbon measurements were made to determine
their value as a surrogate parameter for the more costly organic acid analysis. Figure 15 shows that the
DOC concentration curve closely resembles the curve generated by superimposing the curves of the
organic acids (see Figure 10), but surprisingly, the DOC results are consistently lower than would be
expected based on the concentrations of organic acids present. Although the DOC measurement cannot
differentiate the various organic acids, it does show that organic carbon concentrations were significantly
increased and sustained by the addition of butyric acid.
Dissolved Organic Carbon (mg/L)
180
160
140
120
100
80
60
40
20
0
No
injection
5
10
15
Time (Weeks)
20 25 30
Figure 15. Average Dissolved Organic Carbon Concentrations
18

5.0 Conclusions
Results from the RABITT field demonstration at Camp Lejeune show that native subsurface microbial
populations are capable of sequentially reducing PCE to ethene. PCE and TCE concentrations were
reduced to below detectable levels in almost all wells after 14 weeks and remained depressed throughout
the remainder of the demonstration. The degradation of PCE and TCE was so rapid that injected PCE-
contaminated groundwater was free of both PCE and TCE by the time it reached the first monitoring well
only 5.4 feet away. As a result, kinetic parameters could not be estimated.
As one would expect, the dechlorination of cis-DCE was considerably slower than that of PCE and TCE.
As a result, cis-DCE temporarily accumulated in the testing area. After approximately 20 weeks, a
proportional conversion of cis-DCE to vinyl chloride and finally to ethene was observed at the eastern
edges of the testing location. Neither vinyl chloride nor ethene had been detected previously; strongly
supporting the premise that reductive dechlorination was occurring.
The overall impact of the demonstration on the subsurface included subtle changes in several geochemical
parameters. The addition of the butyric acid solution raised the level of dissolved organic carbon in the
aquifer and contributed to a slight drop in the average site pH from an initial value of 7.9 to a final value
of 6.8. Most electron accepting species were depleted in the testing area prior to the demonstration and
were therefore unaffected. The relatively low levels of sulfate present at system startup were reduced by
about an order of magnitude.
The most significant geochemical change that occurred within the testing location was the production of
methane towards the end of the demonstration. The accumulation of methane shows that a large portion
of added reducing equivalents was being used by methanogens, possibly reducing the efficiency of the
process. An alternative feeding strategy (e.g., pulsed feeding) may help alleviate methane production and
increase treatment efficiency.
The RABITT demonstration system installed at Site 88 provided convincing evidence that native
microorganisms can be stimulated in situ to catalyze the complete reductive dechlorination of chlorinated
ethenes. Based on testing results, this technology appears to be a viable candidate for achieving
reductions in chloroethene contamination at Site 88. Any application of this technology would require a
thorough understanding of the local subsurface hydrogeology and an engineered approach to electron
donor dosing and distribution.
19