&EPA
United States
Environmental Protection
Agency
EPA/600/R-14/234 I April 2016
www.epa.gov/homeland-security-research
Radiological Contaminant Persistence
and Decontamination in Drinking Water Pipes
Office of Research and Development
National Homeland Security Research Center

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Radiological Contaminant Persistence and Decontamination in
Drinking Water Pipes
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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TABLE OF CONTENTS
Page
TABLE OF CONTENTS	iii
NOTICE	v
ACKNOWLEDGEMENTS	vi
LIST 01 ABBREVIATIONS	vii
EXECUTIVE SUMMARY	viii
1.0 INTRODUCTION	1
2.0	SUMMARY OF PERSISTENCE AND DECONTAMINATION EXPERIMENTAL
DESIGN PROTOCOL (PDEDP)	 1
2.1	Experimental Reactor System	2
2.2	Coupon Biofilm Growth	3
2.3	Persistence and Decontamination Experimental Design Protocol (PDEDP)	4
2.3.1	Method Validation Step 1: Surface Contamination Extraction	4
2.3.2	Method Validation Step 2: Surface Contamination	6
2.3.3	Contaminant Persistence Evaluation	7
2.3.4	Contaminant Flushing Evaluation	8
2.3.5	Chemical Cleaning Agent Evaluation	10
3.0	QUALITY ASSURANCE/QUALITY CONTROL	12
3.1	Experimental Controls	12
3.2	Measurement Methods	13
3.1.1	Cesium, Cobalt, and Strontium	13
3.2.2	Enumeration of Biofilm Growth	13
3.3	Quality Control	14
3.4	Audits	15
3.4.1	Performance Evaluation Audit	15
3.4.2	Technical Systems Audit	15
3.4.3	Deviation	15
3.4.4	Data Quality Audit	16
3.4.5	QA/QC Reporting	16
4.0	RESULTS	17
4.1	Method Validation Step 1: Contaminant Surface Extraction	17
4.2	Method Validation Step 2: Contaminant Surface Contamination	18
4.3	Contaminants on Concrete Persistence Evaluation	18
4.4	Contaminants on PVC Persistence Evaluation	21
4.5	Contaminants on Concrete Flushing Evaluation and Water Exposure Control Experiment
24
4.6	Cesium and Cobalt on PVC Flushing Evaluation and Water Exposure Control Experiment
27
4.7	Cobalt on Concrete Chemical Cleaning Agent Evaluation	28
4.8	Strontium on Concrete Chemical Cleaning Agent Evaluation	31
4.9	Water Quality Measurements	33
5.0	RESULTS SUMMARY	35
5.1	Collection of Surrogate Radiological Persistence Data	35
5.2	Persistence and Decontamination Testing	35
5.3	Future Research Needs	36
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6.0 REFERENCES
37
Figures
Figure 1. Persistence evaluation - percent persistence (%P) of cesium, cobalt, and strontium on
concrete	20
Figure 2. Persistence evaluation - percent persistence (%P) on PVC for cesium, cobalt, and
strontium	22
Figure 3. Flushing evaluation and water exposure control experiment- percent persistence (%P)
on concrete for cesium , cobalt, and strontium	25
Figure 4. Flushing evaluation (FE) and water exposure control experiment (WECE) - percent
persistence (%P) on PVC for cesium and cobalt	27
Figure 5. Chemical cleaning agent evaluation - percent persistence (%P) and cobalt remaining on
concrete for tartaric acid and EDTA	29
Figure 6. Chemical cleaning agent evaluation - percent persistence (%P) and strontium
remaining on concrete for calcium chloride and ammonium acetate	32
Tables
Table 1. Contaminant Analytical Techniques, Limit of Quantitation, and Stock Solution
Concentrations	5
Table 2. Persistence Evaluation (PE)	7
Table 3. Evaluation of Flushing as a Decontamination Approach	9
Table 4. Evaluation of Chemical Cleaning Agents (CCA) as a Decontamination Approach	10
Table 5. Experimental Controls	12
Table 6. Data Quality Objectives for ICP-MS Analysis	14
Table 7. Contaminant Surface Contamination Extraction	17
Table 8. Contaminant Surface Contamination	18
Table 9. Contaminants on Concrete - Probability Value Matrix for Persistence Evaluation	21
Table 10. Contaminants on PVC - Probability Value Matrix for Persistence Evaluation	24
Table 11. Contaminants on Concrete - Probability Value Matrix for Flushing Evaluation	26
Table 12. Contaminants on PVC - Probability Value Matrix for Flushing Evaluation	28
Table 13. Cobalt on Concrete - Probability Value Matrix for Chemical Cleaning Agent
Evaluation	31
Table 14. Strontium on Concrete - Probability Value Matrix for Chemical Cleaning Agent
Evaluation	33
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NOTICE
The U.S. Environmental Protection Agency (EPA), through its Office of Research and
Development's National Homeland Security Research Center, funded and managed this project
through Contract No. EP-C-10-001 with Battelle. This report has been peer and administratively
reviewed and has been approved for publication as an EPA document. It has been reviewed by
the Agency but does not necessarily reflect the Agency's views. Mention of trade names or
commercial products does not constitute endorsement or recommendation for use of a specific
product.
Questions concerning this document or its application should be addressed to:
Jeff Szabo, Ph.D., P.E.
National Homeland Security Research Center
Office of Research and Development
U.S. Environmental Protection Agency
26 W. Martin Luther King Drive
Cincinnati, OH 45268
szabo. i eff@epa. gov
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ACKNOWLEDGEMENTS
Contributions of the following individuals and organizations to the development of this
document are gratefully acknowledged.
Battelle
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LIST OF ABBREVIATIONS
ABC	Analytical Balance Corporation
AR	annular reactor
ASTM	ASTM International
AWWA	American Water Works Association
BG	background or not detectable above background
°C	degrees Celsius
CCA	chemical cleaning agent
cfu	colony forming units
cm	centimeters
EPA	U.S. Environmental Protection Agency
%E	percent error
EDTA	ethylenediaminetetraacetic acid
FE	flushing evaluation
ft/s	foot/second
g	gram
in.	inch
HPC	heterotrophic plate counts
L	liter
lpm	liter per minute
|iL	microliter
|ig	microgram
mg	milligrams
mm	millimeters
mL	milliliters
min	minute
NHSRC	National Homeland Security Research Center
%P	percent persistence
PDEDP	pipe decontamination experimental design protocol
PE	persistence evaluation
PVC	polyvinyl chloride
QAPP	Quality Assurance Proj ect Plan
QC	quality control
%R	percent recovery
RPD	relative percent difference
rpm	revolutions per minute
WECE	water exposure control experiment
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EXECUTIVE SUMMARY
The objective of this study was to use the Pipe Decontamination Experimental Design Protocol
(PDEDP) to evaluate the persistence of cesium, cobalt, and strontium on concrete and polyvinyl
chloride (PVC) and explore possible decontamination approaches. The PDEDP is an approach
for evaluating the persistence characteristics of contaminants on drinking water pipe materials
and various decontamination approaches.
During this study, conditions within operational drinking water pipes were simulated using
annular reactors (i.e., ring-shaped reactors). The annular reactors consist of a glass outer
cylinder and a rotating polycarbonate inner cylinder with 20 flush mounted rectangular
coupons that are made of materials that simulate drinking water pipe materials. For this
study, concrete-lined and PVC coupons (samples) were used. Shear stress was applied to the
coupon surfaces by setting the reactors' inner cylinder rotation to 100 revolutions per minute,
which produces shear forces similar to 1 ft/s flow in a 6 inch pipe. During normal operation,
the flow of drinking water through the reactor was maintained at approximately 0.2 liter per
minute so that the residence time of the water in the reactor was approximately 5 minutes.
Prior to use of any pipe material coupons, a biofilm was grown on all of the coupons. Each
contaminant was studied separately and coupons were not shared between experiments.
The study included five components for each contaminant studied:
•	Surface extraction method validation - The surface extraction method validation
confirmed that cesium, cobalt, and strontium could be extracted from the coupons
after direct contamination of the coupons.
•	Surface contamination method validation - The surface contamination method
validation confirmed that coupons could be contaminated with all three contaminants
by exposing them to a solution of contaminated water.
•	Persistence evaluation - Pipe material coupons were contaminated and then exposed
to fresh tap water in annular reactors operating at 100 rpm (simulating 1 ft/s flow).
The results of the persistence evaluation showed that cesium was not persistent on
concrete pipe materials. Conversely, cobalt and strontium were persistent on
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concrete; cobalt more so than strontium. Similarly to concrete, cesium was not
persistent on PVC pipe materials. In addition, cobalt and strontium were not
persistent on PVC pipe materials.
•	Decontamination evaluation for flushing - Pipe material coupons were contaminated
and then exposed to fresh tap water in reactors operating at 200-250 rpm (simulating
1.6-2.5 ft/s flow). The results from the flushing evaluation for cesium, cobalt and
strontium confirmed the results that were observed during the persistence evaluations.
•	Decontamination evaluation for chemical cleaning agents - Pipe material coupons
were contaminated and then exposed to a solution containing one of the following
cleaning agents in reactors with no rotation: ethylenediaminetetraacetic acid (EDTA),
tartaric acid, calcium chloride, ammonium acetate. EDTA was an effective chemical
cleaning agent for cobalt on concrete. Tartaric acid also performed well for cobalt on
concrete however, it formed a yellow precipitate on the surface of the coupons.
Ammonium acetate and calcium chloride were both moderately effective as chemical
cleaning agents for strontium on concrete. None of the contaminants were persistent
on PVC pipe materials so chemical cleaning agents were not evaluated on PVC.
Cesium was not persistent on concrete so chemical cleaning agents were not
evaluated for cesium.
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1.0 INTRODUCTION
The U.S. Environmental Protection Agency's (EPA) National Homeland Security
Research Center (NHSRC) conducts research to protect infrastructure, and to detect, respond to
and recover from terrorist attacks on the nation's water and wastewater infrastructure. The
potential for contamination of water infrastructure with radiological contaminants is one area of
concern. Previous to this study, EPA's Persistence and Decontamination Experimental Design
Protocol (PDEDP), a procedure to quantitatively determine the persistence of contaminants on
various drinking water pipe materials, had been developed. The objective of this project was to
test the PDEDP using surrogates for radiological contaminants and, if the radiological
contaminants persists, to test techniques for decontaminating the pipe surfaces.
Annular reactors (AR) (i.e., ring-shaped reactor) were used to simulate the flow of contaminants
past drinking water pipe materials. The drinking water pipe materials included concrete and
polyvinyl chloride (PVC). Concrete (or cement-mortar) is a common lining on the interior of
iron drinking water pipes. PVC can be used in home plumbing and distribution system pipes.
The contaminants spiked into the ARs included stable cesium (Cs)-133, cobalt (Co)-59, and
strontium (Sr)-88. These contaminant surrogates were selected because of the likelihood of the
presence of the actual contaminants in water systems due to a radiological incident (e.g.,
Radiological Dispersal Device, Nuclear Power Plant accident, or direct contamination of the
system). The following report includes a summary of the experimental design as well as the
results, with one section dedicated to each pipe material and contaminant combination that was
tested.
2.0 SUMMARY OF PIPE DECONTAMINATION EXPERIMENTAL DESIGN
PROTOCOL (PDEDP)
The PDEDP includes five sequential experimental steps. These steps are included
1.	Surface extraction method validation
2.	Surface contamination method validation
3.	Contaminant persistence evaluation
4.	Contaminant flushing evaluation
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5. Chemical cleaning agent evaluation.
Summaries of the experimental set up, each step of the experimental design, and details of the
analytical methods are provided below. Each contaminant was studied separately using the
PDEDP and fresh coupons were used for each experiment.
2.1 Experimental Reactor System
The conditions within operational drinking water pipes were simulated in annular
reactors (AR) (BioSurface Technologies Corporation, Bozeman, MT). The ARs consist of a
glass outer cylinder and a rotating polycarbonate inner cylinder with 20 flush mounted
rectangular coupons that are made of materials that simulate drinking water pipe materials. Tap
water flows into the top of the reactor, through the annular space, and then exits through the
bottom. The rotating inner drum keeps the water in the annular space well mixed.
For this testing, concrete and PVC coupons (BioSurface Technologies Corporation,
Bozeman, MT) were used. For the concrete-lined coupons, the cement in the concrete (or
cement-mortar matrix) met the requirements of the CI 50-07 ASTM International Standard
Specification for Portland Cement (1) and the thickness of the concrete was approximately 1.3
millimeter (mm), which is slightly less than as specified in American Water Works Association
(AWW A) CI 04-03 Standard for Cement-Mortar Lining for Ductile-Iron Pipe and Fittings for
Water (2). The concrete coupons were made from a polycarbonate backing with the concrete
applied at the above thickness. Concrete was separated from the polycarbonate during sampling
and only the concrete was analyzed. The PVC coupons were made entirely of PVC so no
separation was required.
The coupons had surface areas of 14 mm x 148 mm. Shear stress was applied to the
coupon surfaces by setting the inner cylinder rotation to 100 revolutions per minute (rpm), which
produces shear forces similar to 30.5 centimeter (cm)/second (s) (1 foot (ft)/s) flow in a 15.2 cm
(6 inch (in.)) pipe (3). For the flushing evaluation, the cylinder rotation was set as high as 250
rpm, corresponding to shear similar to 75 cm/s (2.5 ft/s) flow in a 15.2 cm pipe. During normal
operation, the flow of drinking water through the annular space of the AR (connected directly to
the tap) was maintained at approximately 0.2 liter per minute (1pm) so the residence time of the
water in the AR was approximately 5 minutes. This water flow prevented the depletion of
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chlorine levels in the water and minimized re-deposition of sheared contaminants on the
coupons.
The pH and temperature of the drinking water was measured daily using a multi-
parameter water monitor (Rosemount Analytical Model WQS, Rosemount Analytical, Irvine,
CA). The free chlorine concentration of the drinking water was measured daily using a Hach®
analyzer (Hach CL17 or DR5000, Hach Company, Loveland, CO). The ARs were always
operated in the dark by covering them completely with aluminum foil. Because some
contaminant was likely to adsorb onto the non-coupon components of the AR and affect the
amount of contaminant that was available for coupon contamination, the concentration of the
bulk contamination solutions was measured to ensure that an adequate concentration of
contaminant was maintained to achieve coupon contamination.
2.2 Coupon Biofilm Growth
Biofilm was grown on all of the coupons before the method validation (surface
contamination extraction and surface contamination), contaminant persistence and
decontamination (flushing and chemical cleaning agent) steps. The biofilm was grown by
submerging the required number of coupons into a sterile container that allowed recirculation of
dechlorinated tap water fortified with 1 gram (g) of yeast extract as a nutrient for biofilm growth.
Dechlorination of the tap water enhanced biofilm growth and reduced the time necessary to
establish a biofilm. The container was kept in the dark to better simulate biofilm growth in an
enclosed pipe and water was recirculated using a pump for at least four days with an additional 1
g of yeast added after every two days.
The biofilm growth on the coupons was measured using heterotrophic plate counts
(HPC). Coupons to be measured for HPC were centrifuged within a Triton™ X solution (Sigma-
Aldrich, St. Louis, MO), mixed using a vortex mixer (Sigma-Aldrich, St. Louis, MO), and then
decanted. Two tenfold dilutions of that decanted solution were prepared and plated in triplicate
on tryptic soy agar plates using a pipette (Rainin L200, L19304, Rainin Instrument LLC,
Oakland, CA). After incubation for 48 hours at 35-37 degrees Celsius (°C), the distinguishable
colonies on each plate were counted and surface density of HPC was calculated.
Throughout the concrete and PVC experiments, 15 sets of coupons were used and the
HPC densities were determined for nine of the 15 sets. On average, the HPC densities were 2.3
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x 106 colony forming units (cfu)/cm2. The standard deviation of the HPC densities was 1.6 x 106
cfu/cm2. While there was not a target HPC density for the coupons, the consistent growth of
biofilm (densities within one log of one another) provided a means to simulate pipe conditions
encountered in the field on pipe material coupons.
2.3 Persistence and Decontamination Experimental Design Protocol (PDEDP)
The generation of persistence and decontamination data from this experimental design
included contamination of coupons by exposing them to bulk solutions of the surrogate
radiological contaminants. Thereafter, the persistence of each contaminant on the coupons
and/or the application of a decontamination approach were investigated to determine both the
propensity of each contaminant to persist on the coupons and the effectiveness of
decontamination approaches in removing the contaminant from the coupon surface. The
usefulness of results from such experiments relies on the accuracy of the contaminant
measurements. In order to be confident in these measurements, two important questions needed
to be answered about the approach to contaminant measurement:
•	When a contaminant has adsorbed to the coupon surface, how well can it be extracted
from that surface?
•	When a coupon has been exposed to a bulk solution at a given concentration, how much
of the contaminant is adsorbed to the coupon surface?
To answer these two questions, two method validation steps were conducted as the first two
steps of the experimental design (section 2.3.1 and 2.3.2). First, the surface contamination
extraction method was validated. Second, the coupon surface contamination method was
validated.
2.3.1 Method Validation Step 1: Surface Contamination Extraction
The validation required 20 half coupons of the selected material type with a biofilm
developed as described in Section 2.2. These coupons were removed from the biofilm growth
container and allowed to air dry until water droplets were not visible on the surface, but the
surface was still damp. This drying step ensured the contaminant was added to the coupon
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surface and not added to the water remaining on the coupon surface following the biofilm growth
period.
Each coupon (including blanks) were cut in half with metal snips and five drops of the
contaminant solution were applied directly to each half coupon using a micropipette (Eppendorf
Research Plus, Eppendorf International, Hauppauge, NY) approximately 10 mm apart. The
volume of each drop was 15 microliter (|iL) for a total addition of 7.5 microgram (|ig) for each
contaminant. Five non-contaminated coupons were also extracted as blanks.
For each of the half coupon segments (contaminated and non-contaminated), the concrete
was removed from the polycarbonate backing and placed into a plastic sample container
(Thermo Scientific # 03-342-23, Thermo Fisher Scientific, Inc., Waltham, MA). To prepare the
concrete for analysis, each concrete sample was dried at 50 °C then ground to a powder using a
glass stir rod (Thermo Scientific # 11381E, Thermo Fisher Scientific, Inc., Waltham, MA). The
concrete samples remained in their individual sample containers throughout the drying and
grinding process to minimize cross contamination and sample loss. Dilute nitric acid and
deionized water were used to clean the glass stir rod before each sample was ground. After the
samples were ground, they were shipped to the analysis laboratory where it was digested for
metals analysis (see Table 1 and section 3.2.1 for analytical method details).
Table 1. Contaminant Analytical Techniques, Limit of Quantitation
Contaminant
Analytical
Technique
Approx. Limit of
Quantitation
Cesium
ICP-MS
0.001 mg/L
Cobalt
ICP-MS
0.001 mg/L
Strontium
ICP-MS
0.001 mg/L
In the case of the PVC coupons, the entire coupon half was placed into a plastic test tube
filled with 25 milliliter (mL) aqueous 0.5% nitric acid which fully submerged the coupon. After
inserting the PVC coupon, the test tube was sealed with a cap and sonicated at 40 kilohertz for 5
minutes, the nitric acid was then decanted into another similar test tube and replaced with 25 mL
of fresh nitric acid, and then sonicated for another 5 minutes. The two aliquots of decanted nitric
acid were combined for analysis. The pipe coupon was then removed from the container and
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rinsed one last time with 0.5% nitric acid. Like the concrete, this solution was shipped to the
analysis laboratory (see Table 1 and section 3.2.1 for analytical method details).
The percent recovery (%R) was calculated using the following equation
Cr
o/o R = -f x 100
^O
where Cr is the mass of contaminant recovered from the coupon surface and C0is the mass of
contaminant originally dispensed onto the coupon surface.
2.3.2 Method Validation Step 2: Surface Contamination
Step 2 involved validating a method to contaminate the surface of the coupons in a way
that simulates an actual intentional contamination of a water distribution system. The surface
contamination method to be validated incorporated:
•	Preparing coupons with biofilm
•	Exposing the coupons to contaminated water in the AR without flow (batch mode)
•	Extraction of the contaminant from the coupon using the method validated in Step 1.
To begin the validation, 10 coupons were prepared with a biofilm. Five of the coupons
were loaded in the AR and five were reserved as blank coupons. The bulk contamination
solution for each contaminant was prepared at approximately 100 mg/L (10 g/L for strontium)
and added to the AR through the opening at the top of the AR. Following addition of the bulk
contamination solution, rotation of the AR was initiated as described in Section 2.1, but the water
was not permitted to flow through the AR in order to increase the contact time between the
contaminated water and the coupons. Two hours following the addition of the bulk
contamination solution, the coupons were removed, dipped once into approximately 25 mL of
uncontaminated ASTM deionized water (rinse step) and then treated following the contaminant
extraction method validated as described in Section 2.3.1 and the extracts analyzed as described
in Section 3.2. The rinse step was to ensure that the contaminant is extracted from the surface of
the coupon and was not an artifact of the residual contamination solution on the surface of the
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coupon. The bulk contamination solution was sampled at the start, middle and end of the
contamination time period to confirm the contaminant availability for adsorption.
2.3.3 Contaminant Persistence Evaluation
This section describes the approach to evaluating the persistence of a contaminant on
various pipe coupon materials. Table 2 provides an overview of the persistence evaluation. For
each combination of coupon material and contaminant, biofilm was grown on 20 coupons as
described in Section 2.2. Two coupons with biofilm were the non-contaminated blank coupons
and the rest of the coupons were contaminated with a bulk solution following the surface
contamination method described in section 2.3.2. Immediately following the coupon
contamination step, three coupons were removed to serve as control coupons. The amounts of
contaminant on the surfaces of these control coupons were compared with the amounts
remaining on the coupons that were left in the AR for various lengths of time following the
removal of the control coupons.
After removal of the control coupons, a stopped flow scenario was evaluated by stopping
the rotation of the AR, stopping the flow of water through the AR, and replacing the
contaminated water with uncontaminated drinking water. Stopping flow simulates a no-flow
environment in a water system that could occur when a "do not use" order is issued. This
stopped flow scenario was conducted for 24 hours after which three persistence evaluation
coupons were removed. After that 24 hour period, the flow of drinking water and AR rotation
was resumed to normal operating conditions (AR rotating at 100 rpm and fresh tap water flow
through the AR). Following the stopped flow scenario, sets of three persistence evaluation
coupons were collected from the AR at four different time increments (4 hours, 1 day, 3 days,
and 7 days) following the resumption of flow. Following the removal of each of these sets of
coupons, they were extracted and the amount of contaminant on the coupon surfaces compared
with the amount on the control coupons collected just after the coupon contamination step.
Table 2. Persistence Evaluation (PE)
PE Step
Description
Coupons
removed
(20 total)
PE 1
Developed biofilm (confirmed with heterotrophic plate count) on 20
coupons; remove two coupons as blank control coupons
2
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PE 2
Stopped flow through AR, filled AR with contaminated bulk solution,
inserted 18 coupons into AR, operated AR at 100 rpm, waited 2 hours
0
PE 3
Sampled bulk contamination solution at start, half-way point, and end of
contamination period
0
PE 4
Following 2 hour contamination period, removed three coupons as
contaminated control coupons
3
PE 5
Stopped AR rotation to simulate stopped flow. Replaced bulk
contamination solution with uncontaminated water and remained at
stopped flow for 24 hours; collected three coupons
3
PE 6
Restarted the AR rotation and flow through the AR. Removed three
coupons each at 4 hours, 1 day, 3 days, and 7 days after restart of AR
rotation and flow
12
PE 7
Measured amount of contaminant remaining on coupons and compared to
amount remaining on contaminated control coupons
0
This comparison was made by calculating the percent persistence (%P) of the
contaminant on the coupons as described by the following equation.
o/op = x 100
where Cpe is the mass of contaminant recovered from the coupon surface and Ccis the average
mass of contaminant originally measured from the surfaces of the control coupon surfaces.
The uncertainty of each of the individual measurements required to calculate the %P (i.e.,
uncertainty in the measurements required to determine the control and experimental results) was
used to determine the propagation of uncertainty in the %P calculation. The combined
experimental uncertainty in the %P calculation (AP) was determined using the method of
propagation of errors and is defined below:
HS2 + ffl2 x %p
where SDpcc and SDptc are the standard deviations of the contaminated control coupons and test
coupons, respectively, being compared. Similarly, Pec and Ptc are the average %Ps of the
contaminated control coupons and the test coupons, respectively, being compared. In addition, t-
tests were used to determine the probability that the data from the various experimental
conditions were significantly different from one another at the 95% confidence interval.
2.3.4 Contaminant Flushing Evaluation
This section describes the evaluation of pipe decontamination using flushing. Table 3
provides an overview of the flushing evaluation. As was the case for the persistence evaluation,
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a biofilm was grown on 20 coupons of the desired material and 18 were loaded in the AR and
contaminated using the validated surface contamination method. Three contaminated coupons
were removed to serve as the control coupons. The amounts of contaminant on the surfaces of
these control coupons were compared with the amounts remaining on the coupons that were left
in the AR and exposed to flushing conditions.
Following coupon contamination, the AR inner cylinder rotation was raised from 100
rpm to 200 rpm which corresponded to a water velocity of 0.5 ms"1 (1.6 ft/s) in a 15.2 cm (6 in.)
pipe (3). This increased rotational speed was held for one day. Sets of three coupons were
collected from the AR at three different time increments (2 hours, 4 hours, and 1 day) following
the coupon contamination. Then, the rotational speed was increased again to 250 rpm (2.5 ft/s in
a 6 in pipe) and held for another day, with the collection of three coupons after 4 hours and after
1 day of 250 rpm conditions. Following the removal of each set of three coupons, the coupons
were extracted and the amounts of contaminant on the coupons were compared with the amounts
on the control coupons collected just after the surface contamination step.
A water control exposure experiment was run in parallel with the flushing
experiments. Contaminated coupons were prepared in the manner described above, but they were
exposed only to fresh drinking water with no AR rotation (stagnant water) and sampled at the
same time intervals as in the flushing experiment. The difference between the samples exposed
to flushing and those in the water control exposure experiment show the effect that flushing had
on adhered contaminant.
Table 3. Evaluation of Flushing as a Decontamination Approach
Step
Description
Coupons
removed
(20 total)
F 1
Developed biofilm (confirmed with heterotrophic plate count) on 20
coupons of same material; removed two coupons as blanks
2
F 2
Injected enough contaminant into ARto achieve desired bulk concentration
within AR; inserted 18 coupons and operated AR at 100 rpm, waited 2
hours
0
F 3
Sampled bulk contaminant solution at start, half-way point, and end of
contamination time
0
F 4
Following 2 hour contamination period, replaced contaminated bulk
solution with uncontaminated water and removed three coupons as
contaminated control coupons
3
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F 5
Increased AR rotational velocity to 200 rpm from original velocity of 100
rpm
0
F 6
Removed three coupons each at 2 hours, 4 hours, and 1 day following
increase in rotational velocity
9
F 7
Increased AR rotational velocity to 250 rpm from 200 rpm
0
F 8
Removed three coupons each at 4 hours and 1 day following increase in
rotational velocity
6
F 9
Measured amount of contaminant remaining on coupons and compared to
amount remaining on contaminated control coupons
0
2.3.5 Chemical Cleaning Agent Evaluation
This section describes the evaluation of pipe decontamination using chemical cleaning
agents (CCA). Cleaning agents were only evaluated on contaminants deemed persistent in
previous steps of the PDEDP. Table 4 provides an overview of the CCA experiments. A biofilm
was grown on 20 coupons of the desired material and 18 were loaded in the AR and
contaminated using the validated surface contamination method. After contamination, three
contaminated coupons were removed to serve as the control coupons. The amounts of
contaminant on the surfaces of these control coupons were compared with the amounts
remaining on the coupons that were left in the AR and exposed to CCA.
The CCA evaluation was started in a similar way as for the flushing evaluation.
However, instead of increasing the rotational velocity of the AR, the rotation of the AR was
stopped and the tap water flow through the AR was also stopped to simulate a stopped flow
scenario. Stopping flow simulates a no-flow environment in a water system that could occur
when a "do not use" order is issued. The CCA was then added and the chemical treatment was
performed as a stopped flow treatment. Comparison of the amounts of contaminant adhered to
the coupons before and after treatment was made by calculating the %P as described earlier.
Table 4. Evaluation of Chemical Cleaning Agents (CCA) as a Decontamination Approach
Step
Description
Coupons
removed
(20 total)
CCA 1
Developed biofilm (confirmed with heterotrophic plate count) on 20
coupons of same material; removed two coupons as blanks
2
CCA 2
Injected enough contaminant into ARto achieve desired bulk concentration
within AR; inserted 18 coupons and operate AR at 100 rpm, waited 2 hours
0
CCA 3
Sampled bulk contaminant solution at start, half-way point, and end of
contamination time
0
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CCA 4
Following the 2 hour contamination period, replaced bulk solution with
uncontaminated water and removed three coupons as contaminated control
coupons
3
CCA 5
Stopped flow through AR and stopped rotation of AR; introduced CCA at
desired concentration and pH level
0
CCA 6
Removed three coupons at 2 hours, 4 hours, 1 day, 3 days, and 7 days
following introduction of CCA
15
CCA 7
Calculated percent persistence for all coupons by comparing residual
contaminant on the surface with contaminated control coupons
0
11

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3.0 QUALITY ASSURANCE/QUALITY CONTROL
3.1 Experimental Controls
Table 5 summarizes the controls included in this study. The controls are important
because the results of the persistence and decontamination experiments are dependent on the
original concentration of contaminants on the surface of the control coupons. In addition, the
AR has available surface area that could become contaminated, thus becoming a source of
secondary contamination.
Table 5. Experimental Controls
Component of Pipe
Decontamination
Experimental Design
Type of Control
Description
Surface Contamination
Extraction Method Verification
Five non-
contaminated blanks
Allows comparison between coupons that have
contaminant applied and those that have not
Surface Contamination Method
Verification
Five non-
contaminated blanks
Allows comparison between coupons that have
contaminant adsorbed from the bulk solution and
those that have not
Evaluation of Contaminant
Persistence
Two non-
contaminated
control coupons
blanks
Taken from a set of coupons following biofilm
growth; allows comparison of coupons that have been
contaminated from the bulk solution and those that
have not been contaminated
Three contaminated
control coupons
Removed from AR after contamination of coupons,
but before persistence testing in clean water; allows
comparison of coupons containing a "diminished"
amount of contaminant (due to "normal" flow of
clean water) with coupons containing "total" amount
of contaminant (not influenced by the "normal" flow
of clean water)
Evaluation of Flushing
Decontamination
Two non-
contaminated blanks
Taken from set of coupons following biofilm growth;
allows comparison of coupons that have been
contaminated from the bulk solution and those that
have not
Three contaminated
control coupons
Removed from AR after contamination of coupons,
but before flushing at increased velocities in clean
water; allows comparison of contaminant remaining
on the coupons only due to increased rotational
velocity
Water Exposure
Control Experiment
(18 coupons)
Contaminated coupons that are exposed only to clean
water (no AR rotation) to determine decontamination
differences at increased time intervals and increased
AR rotational speeds
Evaluation of Chemical
Cleaning Agent
Decontamination
Two non-
contaminated blanks
Taken from set of coupons following biofilm growth;
allows comparison between coupons that have
contaminant adsorbed from the bulk solution and
those that have not
Three contaminated
control coupons and
Removed from AR at specified coupon collection
time intervals and placed in container with
dechlorinated drinking water; allows comparison of
12

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other collected
contaminant remaining before and after introduction

coupons
of the chemical cleaning agent
3.2 Measurement Methods
3.2.1	Cesium, Cobalt, and Strontium
The analytical method that was used for the chemical form all three contaminants is EPA
Method 200.8 (4) "Determination of Trace Elements in Waters and Wastes by Inductively
Coupled Plasma - Mass Spectrometry". Although cesium and strontium are not covered by
Method 200.8, the techniques in Method 200.8 were used to digest the cement-mortar samples.
Analytical Balance Corporation (ABC) has extensive experience using Method 200.8 to treat and
digest water samples, and performed all ICP-MS analyses of aqueous cesium, cobalt and
strontium in this study. Calibration standards were prepared in ASTM Type 1 water with
external standards and acidified. A six-point calibration curve was generated prior to sample
analyses. A calibration blank was also prepared using ASTM Type I water and acidified with
the same acid matrix as the calibration standards. The calibration levels bracketed the sample
concentration. The limit of quantification for ICP-MS analyses of aqueous (post-digestion) Cs,
Sr and Co was approximately 0.001 mg/L. Two continuing calibration check solutions were
analyzed after every 10 samples and at the end of the sequence in order to verify instrument
sensitivity and calibration throughout the analysis. The results of these samples were always
between 90 -110% of the known concentration. A laboratory reagent blank consisting of ASTM
Type I water was analyzed and no contamination was found. A laboratory fortified matrix
sample was analyzed with each batch of samples. Recoveries for the samples were always
within the acceptable range of 85-115%. It should be noted that the radiochemistry method for
each contaminant would be used in the event of a contamination incident with radionuclides.
3.2.2	Enumeration of Biofilm Growth
Biofilm growth on the coupons was enumerated using the following steps. A sterile
0.01%) solution (by volume) of Triton X-100 (Sigma-Aldrich, St. Louis, MO) in phosphate
buffered saline was prepared. The coupon to be analyzed was either cut in half (for the PVC pipe
material), or the concrete was chipped off the polycarbonate backing (for the concrete pipe
material) then placed in a sterile centrifuge tube (VWR # 89004-364, VWR, West Chester, PA)
containing 30 mL of the 0.01% Triton X solution, mixed using a vortex mixer, and then
13

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decanted. Thereafter, two tenfold dilutions of that decanted solution were prepared using the
0.01% Triton X solution as the diluent. Each of those solutions were plated in triplicate by
dispensing 100 [jL onto agar plates (Teknova #T0134, Teknova, Hollister, CA). Using a
spreader, the aliquot was evenly distributed on the plate and placed in an incubator for at least 48
hours at 35-37 °C. After incubation, the distinguishable colonies on each plate were counted. In
order to be considered a viable plate count, the number of colonies on a given plate were
required to be between 30 and 300. The density of colony forming units (cfu/cm2) was
determined by dividing the average number of colonies by the plated volume, multiplying by the
dilution factor and the sample volume and then dividing by the coupon area.
3.3 Quality Control
Quality control samples for the contaminant reference methods, including continuing
calibration checks, laboratory blanks, and laboratory fortified matrix samples are described in
Section 3.2.1. The data quality objectives for each of these samples are provided in Table 6.
The acceptable ranges were established to limit the error introduced into the experimental work.
Table 6. Data Quality Objectives for ICP-MS Analysis
Method
Sample Type
QC Requirement
Corrective Action
ICP-MS
analysis of
cesium, cobalt,
and strontium
(EPA Method
200.8)
Initial calibration
verification
(secondary source)
90-110% of known
concentration
Rerun analysis
Continuing
calibration check
90-110% of known
concentration,
every batch of 10
samples
Repeat sample analysis; if still
outside of range repeat calibration
Calibration and
laboratory reagent
blank
+/-10% of detection
limit; include with
each batch of 10
samples
Determine and correct cause of
contamination
Laboratory
fortified matrix
spike
85-115% of known
concentration;
every batch of 10
samples
Repeat sample analysis; if still
outside of range repeat calibration
Laboratory
duplicate sample
<20% RPD
Repeat sample analysis; if still
outside of range repeat calibration
Matrix and
digestion spike
80-120%
Repeat sample analysis; if still
outside of range repeat calibration
Digestion blank
+/-10% of detection
limit
Repeat sample analysis; if still
outside of range repeat calibration
ICP-MS, inductively coupled plasma - mass spectrometry: RPD, relative percent difference
14

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3.4 Audits
3.4.1 Performance Evaluation Audit
A performance evaluation audit was conducted to assess the accuracy of the ICP-MS
reference method (EPA Method 200.8). A performance evaluation sample containing 105 mg/L
cesium, 40 mg/L cobalt, and 49 mg/L strontium was provided for analysis. Accuracy of the
measurement was expressed in terms of the percent error (%E), as calculated from the following
equation:
where CRwas the standard or reference concentration of the performance evaluation sample and d
was the measurement obtained using the reference method. Ideally, if the reference value and
the measured value were the same, there would be a percent error of zero. The results of the
reference method indicated %E of 2% for cesium, 7% for cobalt, and 19% for strontium. All of
these values are within the acceptable %E of 25%, which is an internal Battelle standard for
accuracy.
3.4.2	Technical Systems A udit
The Battelle QA Manager conducted a technical systems audit at the Columbus, OH
testing location to ensure that the evaluation was performed in accordance with the quality
assurance project plan (QAPP) for this study. As part of the audit, the Battelle QA manager
reviewed the reference sampling and analysis methods used, compared actual evaluation
procedures with those specified in the QAPP, and reviewed data acquisition and handling
procedures. No significant adverse findings were noted in this audit. The records concerning the
audit are permanently stored with the Battelle QA manager.
3.4.3	Deviation
There was one deviation to the quality assurance project plan during this project. During
Method Validation Step 2: Surface Contamination, the bulk solution used for contamination was
100 mg/L for cesium and cobalt. For strontium, 100 mg/L did not provide enough strontium to
the surface of the coupon for strontium detection above the background. A 10 g/L strontium
solution was used successfully. The QAPP listed the bulk contamination solution to be 1 mg/L
Cr
15

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for all three contaminants. A 10 g/L strontium solution was employed in Step 2 and all
subsequent steps where strontium used. There was no negative impact as a result of this
deviation.
3.4.4	Data Quality A udit
At least 10% of the data acquired during the evaluation were audited. The Battelle QA
manager traced the data from the initial acquisition, through reduction and statistical analysis, to
final reporting, to ensure the integrity of the reported results. All calculations performed on the
data undergoing the audit were checked.
3.4.5	QA/QC Reporting
Each assessment and audit was documented in accordance with the Testing and
Evaluation Contract QAPP. Once an assessment report was prepared by the Battelle QA
manager, it was routed to the work assignment leader and Battelle Testing and Evaluation
Program manager for review and approval. The Battelle QA manager then distributed the final
assessment report to the EPA contracting officer's representative, QA manager, and Battelle
staff.
16

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4.0 RESULTS
Testing of the PDEDP included use of non-radioactive cesium, cobalt, and strontium with
concrete lined and PVC AR coupons. The results are divided into separate sections for each
combination of contaminant and coupon type. In order to further evaluate the data, t-tests were
performed to determine what time periods exhibited significant differences from one another at
the 95% confidence interval. The null hypotheses of the t-tests were that the difference in
amount of contaminant remaining on the coupons across the various sample collection time
periods was zero. The probabilities (p) generated by the t-test were the probabilities of the null
hypothesis being confirmed. Therefore, p-values less than 0.05 indicated a small likelihood the
difference between the two data sets was zero, and thus, are considered to be significantly
different from one another.
4.1 Method Validation Step 1: Surface Contamination Extraction
The objective of this component of testing was to determine if the three contaminants
could be extracted from the coupon surfaces. Concrete and PVC coupons were spiked with 7.5
|ig of cesium, cobalt, or strontium. For concrete coupons, the concrete was removed from the
polycarbonate backing using the method described in Section 2.3.1, but the results were reported
for only the concrete. The PVC was rinsed with dilute nitric acid and the rinse analyzed directly.
Table 7 gives the results including the amount of contaminant spiked onto the coupons, the
amount extracted, the total recovery, and the standard deviation.
Table 7. Surface Contamination Extraction

Amount
spiked
Gig)
Avg. amount
recovered (jug)
Total
Recovery
SD
Cs concrete
7.5
1.3
18%
4%
Co concrete
0.8
11%
6%
Sr concrete
BG
BG
BG
Cs PVC
7.1
95%
17%
Co PVC
4.7
62%
4%
Sr PVC
7.6
101%
15%
Five replicates were spiked and extracted at each concentration level.
BG-indicates that the spiked Sr was not detectable above the background; this experiment was not repeated because
Method Validation Step 2 revealed successful detection extraction from the concrete coupon (see section 4.2).
17

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4.2 Method Validation Step 2: Surface Contamination
This testing indicates whether or not a contaminant will adsorb to the pipe coupon surface
after the coupon is exposed to a bulk water solution. Table 8 gives the results from the surface
contamination method validation on concrete and PVC after a two hour exposure to 100 mg/L of
each contaminant in the ARs. Excluding strontium on concrete, an average of between 3.1 |ig
and 33 jug of contaminant was adsorbed to the coupon surfaces out of a total of 100,000 |ig of
contaminant (0.003-0.03%) that was available in the bulk solution. The results show that
cesium, cobalt, and strontium (on PVC only) reproducibly adsorbed to the surface of the concrete
and PVC coupons and could be recovered.
Strontium was not detectable on the concrete above the background levels when a 100
mg/L solution was used. Therefore, strontium contamination was performed with a 10 g/L
strontium solution in this step and all subsequent steps of the PDEDP. Using a 10 g/L solution
resulted in an average of 385 |ig of recoverable strontium from concrete. Overall, the ratio of
target contaminant on the concrete to the target contaminant measured in the background
concrete coupon samples was 29, 41, and 7 for cesium, cobalt, and strontium (10 g/L
contamination solution), respectively. For the PVC coupons, the ratios were 63, 152, and 26 for
cesium, cobalt, and strontium (all 100 mg/L contamination solutions), respectively.
Table 8. Contaminant Surface Contamination
Contaminated
Coupon
Amount Recovered from Concrete (ng)
Amount Recovered from PVC (ng)
Cesium
Cobalt
Strontium3
Cesium
Cobalt
Strontium
#1
3.6
25
410
19
18
30
#2
2.8
24
422
16
16
42
#3
2.7
20
444
14
14
19
#4
4.4
69
348
15
15
23
#5
2.0
27
305
15
19
21
Avg.
3.1
33
385
16
16
27
St. Dev.
0.9
20
58
2.0
2.1
9.4
%RSD
30%
61%
15
12%
13%
35%
11 Sr experiments included use of a 10 g/L contamination solution.
4.3 Contaminants on Concrete Persistence Evaluation
18

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Figure 1 shows the results from the persistence evaluation for each contaminant on the
concrete coupon surfaces. The vertical axes show the percent of each contaminant remaining on
the coupons after each time period (shown across the horizontal axis) during which fresh tap
water is flowing through the AR and the AR is rotating at 100 rpm. The columns at the far left
side of the graphs (0 hr) represent the initial contamination level (as measured on the
contaminated control coupons) and each successive column represents the time periods and
experimental conditions defined by the PDEDP. The error bars on the graphs are the standard
deviations of the contaminant remaining on the three coupons sampled.
Cesium on Concrete
160%
140%
120%
100%
%P 80%
60%
40%
20%
0%
Background Oh 24 h Stop 4 h	1 day 3 day 7 day
Flow
Cobalt on Concrete
250%
Background Oh 24 h Stop 4 h	1 day 3 day 7 day
Flow
19

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%p
Strontium on Concrete
140%
120%
100%
80%
60%
40%
20%
0%
Jill
Background 0 h
24 h Stop
Flow
4 h
1 day
3 day
i
7 day
Figure 1. Persistence evaluation - percent persistence (%P) of cesium, cobalt, and
strontium on concrete.
Based on observation of the graphs in Figure 1, the amounts of residual cesium and
strontium decreased throughout the experiment while the residual cobalt remained steady or
possibly exhibited a slight increase. In order to further clarify the data, t-tests were performed to
determine what time periods exhibited significant differences from one another at the 95%
confidence interval. The null hypotheses of the t-tests were that the difference in amount of
contaminant remaining on the coupons across the various time periods was zero. The
probabilities (p) generated by the t-test were the probabilities of the null hypothesis being
confirmed. Therefore, p-values less than 0.05 indicated a small likelihood that the difference
between the two data sets was zero, and thus, are considered to be significantly different from
one another.
Table 9 gives the p-values for comparison of each possible set of coupons collected at the
various time periods. The data that exhibited significant differences are highlighted in gray. For
cesium, the initial contamination level was significantly different from each of the subsequent
sample collection times. Therefore, the residual cesium in Figure 1 decreased during stopped
flow and 4 hours later. The decrease steadied thereafter as the residual amounts became
relatively small. Statistically, the day 3 cesium sample was the same as the 24 hour sample, but
it was still significantly different than the 0 hour sample. For cobalt, there were only two
significant differences, both of which provided indication of an increase between the initial
contamination and the 3 day sample. For strontium, the only significant differences were
20

-------
between the zero hour sample and the rest of the time intervals. These data indicate that after the
initial contamination (0 hr), strontium concentration at all of the subsequent time intervals was
significantly smaller than at time zero. However, the concentration of strontium on the coupons
at all time intervals past time zero were statistically the same.
In summary, the cesium does not persist on the concrete coupons as the residual percent
persistence (%P) values decrease to less than 5% within 4 hours after the stopped flow.
Strontium is slightly more persistent in that the %Ps decrease to approximately 30% over the
course of the experiment. Cobalt is very persistent as there is no significant decrease in %P
throughout the course of the experiment.
Table 9. Contaminants on Concrete - Probability Value Matrix for Persistence Evaluation
Cesium
Cobalt
Strontium
Persistence
Evaluation Times
Oh
24 h Stop Flow
4 h
1 day
3 day
Oh
24 h Stop Flow
4 h
1 day
3 day
Oh
24 h Stop Flow
4 h
1 day
3 day
probabi ity (p) values (< 0.05 - significant difference)
24 h stop 4 h
0.0327
0.2831
0.0184
0.0290
0.0023
0.0812
0.8843
0.0084
0.4632
1 day
0.0280
0.0046
0.0219
3 day
0.0279
0.0778
0.9141
0.3845
7 day
0.0277
0.0027
0.1486
0.9480
0.3818
0.4888
0.0021
0.2093
0.9841
0.0657
0.9691
0.9098
0.0093
0.8170

0.1744
0.9958
0.0315
0.0217
0.0013
0.0016
0.4573
0.0959
0.0753
0.8974
0.2463
0.1490

0.3989
0.2748
0.6058
Light shading indicates significant differences
4.4 Contaminants on PVC Persistence Evaluation
Figure 2 shows the results from the persistence evaluation for each contaminant on the
PVC coupon surfaces. The vertical axes show the percent of each contaminant remaining on the
coupons after each time period (shown across the horizontal axis) during which fresh tap water is
flowing through the AR and the AR is rotating at 100 rpm. The columns at the far left side of the
graphs represent the initial contamination level (0 hr as measured on the contaminated control
coupons) and each successive column represents the time periods and experimental conditions
21

-------
Cesium on PVC
140%
120%
100%
Background Oh 24 h Stop 4 h
Flow
1 day 3 day 7 day
Cobalt on PVC
140%
120%
100%
Background 0 h
24 h Stop 4 h
Flow
1 day 3 day
7 day
Strontium on PVC
%P
140%
120%
100%
80%
60%
40%
20%
0%
1
1


1
1.	
Background Oh 24 h Stop
Flow
4 h
1 day 3 day 7 day
Figure 2. Persistence evaluation - percent persistence (%P) on PVC for cesium, cobalt, and
strontium.
22

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defined by the PDEDP. The error bars on the graphs are the standard deviations of the remaining
contaminant measured on the three coupons sampled.
Based on observation of the graphs in Figure 2, the amounts of all three contaminants
decreased throughout the experiment relative to the 0 hour and 24 hour samples. There was a
slight increase at the end of the cesium experiment while the residual levels of the other two
contaminants steadied over the final days of the experiment. In order to further clarify the data,
t-tests were performed to determine what time periods exhibited significant differences from one
another at the 95% confidence interval. The null hypotheses of the t-tests were that the
difference in amount of contaminants remaining on the coupons across the various time periods
was zero.
Table 10 gives the p-values for comparison of each possible set of coupons collected at
the various time periods. The data that exhibited significant differences are highlighted in gray.
For all three contaminants, the initial contamination level was significantly different from each
subsequent sample collection interval. In addition, the 24 hour stopped flow sample was
significantly different than the subsequent samples, indicating that a decrease in residual
contaminant concentration continued past the 24 hour stopped flow sample. However, beyond
the sample collected 4 h after the stopped flow, only strontium exhibited a continued significant
concentration decrease. Interestingly, the cesium exhibited a significant increase in %P when
comparing the 3 day to the 7 day sample. There is no clear reason for this apparent increase in
average residual contaminant. In summary, none of the three contaminants persist on the PVC
coupons as the residual %Ps decrease to less than 5% within 4 hours after the stopped flow. The
only exception observed here was the 7 day cesium sample.
23

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Table 10. Contaminants on PVC - Probability Value Matrix for Persistence Evaluation
Cesium
Cobalt
Strontium
Persistence
Evaluation Times
Oh
24 h Stop Flow
4 h
1 day
3 day
Oh
24 h Stop Flow
4 h
1 day
3 day
Oh
24 h Stop Flow
4 h
1 day
3 day
probabi ity (p) values (< 0.05 - significant difference)
24 h stop 4 h
0.0002 0.0000
0.0320
0.0330
0.0259
0.0194
0.0415
0.0209
0.0277
1 day
0.0000
0.0241
0.4647
3 day	7 day
0.0000
0.0293
0.0742
0.6914
0.0000
0.5350
0.0000
0.0001
0.0006
0.0194
0.0193
0.0186
0.0383
0.0380
0.0346
0.1463
0.1416
0.0827

1.0000
0.2193
0.2222
0.0203
0.0202
0.0209
0.0243
0.0186
0.0261
0.0452
0.5326
0.7045

0.4699
0.0857
0.4161
Light shading indicates significant differences
4.5 Contaminants on Concrete Flushing Evaluation
Figure 3 shows the %P results from the flushing evaluation and water exposure control
experiment for all three contaminants on the concrete coupon surfaces. The bars at the far left
side of the graphs (0 h) represent the %P of the average initial contamination level measured on
the three contaminated control coupons (by definition the %P is 100%). The remaining bars
represent the %P of cesium, cobalt, and strontium after exposure to the rotational velocities noted
along the horizontal axis. The error lines on the graphs represent the propagated error around the
calculation of %P as described in Section 2.3.3. The water exposure control experiment included
the contamination and collection of coupons in a manner identical to that of the flushing
evaluation, but the AR was not rotating (see section 2.3.4).
24

-------
%p
140%
120%
100%
80%
60%
40%
20%
0%
Cesium on Concrete
:11 •
FE
A"
WECE
300%
250%
200%
%P 150%
100%
50%
0%
Oh 2h 200 4 h 200 24 h 200 4 h 250 24 h 250
rpm rpm rpm rpm rpm
Cobalt on Concrete
]|| J	J	J	ill	ill
JJzl	¦	¦	¦	¦
0h 2h 200	4 h 200	24 h 200	4 h 250	24 h 250
rpm rpm	rpm	rpm rpm
FE
I WECE
Strontium on Concrete
120%
100%
%P 60%
WECE
2h 200 4 h 200
rpm rpm
24 h 200
rpm
4 h 250 24 h 250
rpm rpm
Figure 3. Flushing evaluation (FE) and water exposure control experiment (WECE)
percent persistence (%P) on concrete for cesium, cobalt, and strontium.
Upon observation of Figure 3, the data confirm the results determined during the
persistence evaluation. The cesium does not persist under flushing conditions. In fact, the water
25

-------
exposure control experiment results indicate that cesium exposed to stagnant water also does not
persist as there is very little detectable residual cesium near the end of the experiment. Strontium
persists to a larger extent, with the %P decreasing to approximately 40% over the course of the
experiment. Strontium also persisted in stagnant water. Cobalt is the most persistent with no
significant decrease observed. Also, the cobalt water exposure control experiment result
suggests that cobalt on concrete is persistent in stagnant water.
Statistical analyses were performed using t-tests to further clarify any differences
between the time intervals during each flushing scenario. Table 11 gives the p-values for
comparisons of all possible pairs of coupons collected at the various flushing conditions. The
significant differences are highlighted in gray. These results show that for cesium and strontium,
only the initial contaminated samples are significantly different from the rest of the samples
indicating that the decrease in residual contaminant steadies after the 2 h, 200 rpm sample is
collected and remains statistically unchanged for the rest of the experiment. No significant
change in cobalt concentration was observed during the course of flushing.
Table 11. Contaminants on Concrete - Probability Value Matrix for Flushing Evaluation
Cesium
Cobalt
Strontium
Persistence
Evaluation Times
Oh
2h 200 rpm
4 h 200 rpm
24 h 200 rpm
4 h 250 rpm
Oh
2h 200 rpm
4 h 200 rpm
24 h 200 rpm
4 h 250 rpm
Oh
2h 200 rpm
4 h 200 rpm
24 h 200 rpm
4 h 250 rpm
probabi ity (p) values (< 0.05 - significant difference)
2h 200 4 h 200
rpm
0.0034
0.4656
0.0484
rpm
0.0094
0.4226
0.3106
0.4062
0.0200
0.0804
24 h 200
rpm
0.0094
0.4226
NA
4 h 250 24 h 250
rpm
0.0094
0.4226
NA
NA
rpm
0.0094
0.4226
NA
NA
NA
0.2517
0.2500
0.2587
0.4061
0.2802
0.4160
0.7077
0.7109
0.7366

0.9087
0.9668
0.9459
0.0464
0.0034
0.0378
0.1042
0.0177
0.0932
0.5242
0.5436
0.5928

0.7845
0.8862
0.9068
Light shading indicates significant differences
NA: Not Analyzed
26

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4.6 Cesium and Cobalt on PVC Flushing Evaluation and Water Exposure Control
Experiment
Figure 4 shows the %P results from the flushing evaluation and water exposure control
experiment for cesium and cobalt only on PVC. Strontium was not tested during flushing since
adhesion to PVC was low during the persistence evaluation when strontium was spiked at the
higher concentration of 10 g/L.
Cesium on PVC
150% -i	 	
Cobalt on PVC
¦ WECE
Oh 2h 200 4 h 200 24 h 200 4 h 250 24 h 250
rpm rpm rpm rpm rpm
Figure 4. Flushing evaluation (FE) and water exposure control experiment (WECE) -
percent persistence (%P) on PVC for cesium and cobalt.
The results in Figure 4 also confirmed the persistence evaluation results. The cesium did
not persist either in the flushing evaluation or during the water exposure control experiment.
Interestingly, the %P decreased more in the stagnant water of the water exposure control
27

-------
experiment. Cobalt also did not persist, but it does seem that the flushing provides an
enhancement of decontamination compared with the water exposure control experiment. Table
12 gives the p-values for comparisons of all possible pairs of coupons collected at the various
flushing conditions. The significant differences are highlighted in gray. These results show that
for cesium, only the initial contaminated samples are significantly different from the rest of the
samples, indicating that the decrease in residual contaminant steadies after the 2 h, 200 rpm
sample is collected and remains statistically unchanged for the rest of the experiment. For
cobalt, Figure 4 shows a clear difference between the average values of the initial contaminated
coupon and the subsequent sample collection times. However, there is not a statistically
significant difference between the time zero concentration and the rest of the coupons because of
a large uncertainty in the measurement of the initial coupon.
Table 12. Contaminants on PVC - Probability Value Matrix for Flushing Evaluation
Cesium
Cobalt
Persistence
Evaluation Times
Oh
2h 200 rpm
4 h 200 rpm
24 h 200 rpm
4 h 250 rpm
Oh
2h 200 rpm
4 h 200 rpm
24 h 200 rpm
4 h 250 rpm
probabi ity (p) values (< 0.05 - significant difference)
2h 200 4 h 200
rpm
0.0207
0.0794
rpm
0.0204
0.1734
0.0792
0.8419
24 h 200
rpm
0.0205
0.0474
1.0000
4 h 250 24 h 250
rpm
0.0204
0.0824
0.7250
0.6495
rpm
0.0204
0.0824
0.7250
0.6495
1.0000
0.0776
0.0768
0.0764
0.1135
0.0691
0.0447
0.1007
0.0572
0.0326

0.1835
0.0765
0.1835
Light shading indicates significant differences
4.7 Cobalt on Concrete Chemical Cleaning Agent Evaluation
Data from the persistence evaluation and flushing evaluation experiments strongly
suggested that cobalt was persistent on concrete under routine and flushing flow conditions.
Therefore, two separate experiments were performed to evaluate 0.1 M tartaric acid (pH 3) and
0.1 M ethylenediaminetetraacetic acid (EDTA) as decontaminating agents for cobalt adhered to
concrete. The coupons were contaminated, the control coupons were removed, and then the
CCA was added to the AR with no flow or rotation and coupons were then collected over the
course of the next 7 days.
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Cobalt on Concrete - Tartaric Acid
160%
140%
120%
100%
%P 80%
i ¦
Ohr	2 hr	4 hr	1 day	3 day	7 day
Cobalt on Concrete - EDTA
180%
160%
140%
120%
100%
0 hr
2 hr	4 hr	1 day	3 day	7 day
Figure 5. Chemical cleaning agent evaluation - percent persistence (%P) on concrete for
tartaric acid and EDTA.
Observation of the graphical results indicate that EDTA is an effective CCA for cobalt on
concrete. Tartaric acid also appears to have good CCA characteristics. However, a yellow
precipitate formed on the concrete coupons application of tartaric acid, making it a less than
desirable CCA from a practical standpoint. Also, the concentration of cobalt increased at later
time intervals, which may result from the observed precipitation.
When comparing the CCA decontamination results in stagnant water to the effect of
stagnant water alone, the effectiveness of the CCA is clear. In Figure 1 (pg. 21, section 4.3), the
effect of stagnant water alone on the removal of cobalt from cement-mortar is shown. Cobalt
concentration effectively remained the same over the course of 24 hours. When exposed to
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EDTA, the adhered cobalt concentration decreased by approximately 95% within 2 hours and
remained at that level up to 7 days. Figure 1 also shows that the cobalt concentration remained
the same or increased over the course of 7 days after exposure to flow, which suggests that
further treatment with stagnant water alone would be ineffective.
Statistical analyses were performed using t-tests to further clarify any differences among
the data from each CCA treatment scenario. Table 13 gives the p-values for comparisons of all
possible pairs of coupons collected at the various time intervals.
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Table 13. Cobalt on Concrete - Probability Value Matrix for Chemical Cleaning Agent
Evaluation
EDTA
Evaluation
Conditions
probability (p) values (< 0.05 - significant difference)
Tartaric
Acid
Ohr
2	hr
4 hr
1	day
3	day
Ohr
2	hr
4	hr
1 day
3	day
0.0447
0.0497
0.0533
0.0724
0.0758
0.9973
0.3695
0.0589
0.0279
0.1999
0.0000
0.0419
0.0532
0.0526
0.3972
0.0558
0.0556
0.0574
0.0587
0.0571
0.4002
0.2204
0.0231
0.3535
0.1858
0.0177
0.3116
0.4090
0.9900
0.5596
Light shading indicates significant differences
The significant differences are highlighted in gray. For the tartaric acid, the first two time points
(2 h, 4 h, and 1 day) were significantly different than the initially contaminated coupon even
though there was a relatively high level of uncertainty in the initial measurement due to one
measurement that was close to an outlier. Later in the experiment, there were some significant
differences that were driven by the increase in concentration mentioned above. For EDTA, the
contaminated control samples were almost significantly different than many of the rest of the
samples collected. However, there was some uncertainty in that measurement that caused the p-
values to be just above what would be considered significantly different at the 95% confidence
interval. Within the first two hours, the cobalt concentration dropped to levels near the detection
limit and remained there the rest of the experiment. The data suggest that EDTA is a strong
CCA for cobalt from concrete.
4.8 Strontium on Concrete Chemical Cleaning Agent Evaluation
Data from the persistence evaluation and flushing evaluation experiments suggested that
strontium was persistent on concrete under routine and flushing flow conditions. Therefore, two
separate experiments were performed in order to evaluate 0.1 M calcium chloride and 0.2 M
ammonium acetate (pH 3) as decontaminating agents for concrete lined pipes. The coupons
were contaminated, the control coupons were removed, and then the CCA was added to the AR
with no flow or rotation and coupons were then collected over the course of the next 7 days.
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Strontium on Concrete - Calcium Chloride
Ohr	2 hr	4 hr 1 day 3 day 7 day
. _no/ Strontium on Concrete - Ammonium Acetate
lZU/o ~|	
100%
80%
%P 60%
40%
20%
0%
Ohr 2 hr 4hr 1 day 3 day 7 day
Figure 6. Chemical cleaning agent evaluation - percent persistence (%P) and strontium
remaining on concrete for calcium chloride and ammonium acetate.
Observations of the graphical results indicate that calcium chloride is a moderately
effective CCA for strontium on concrete. The %P dropped to approximately 10% within the first
2 hours and then stabilized. Ammonium acetate dropped the strontium concentration, which
then increased over the following several days.
Figure 1 (pg. 21, section 4.3) shows that after exposure to stagnant water for 24 hours,
strontium concentration decreased by 43%, with no further reduction (or a slight reduction) when
shear was applied. These results indicate that continued exposure to stagnant water would not
improve decontamination effectiveness. When coupons were exposed to calcium chloride and
ammonium acetate, a strontium reduction of 90% occurred within two hours. This result held
constant for calcium chloride, but continued exposure to ammonium acetate led to some
strontium reaccumulating after 7 days of exposure. Once again, these results show the benefit of
CCAs compared to stagnant or flowing water.
-1		1-
HI
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Table 14. Strontium on Concrete - Probability Value Matrix for Chemical Cleaning Agent
Evaluation
Calcium
chloride
Ammonium
Acetate
Evaluation
Conditions
probability (p) values (< 0.05 - significant difference)
Ohr
2 hr
4 hr
1	day
3	day
Ohr
2	hr
4	hr
1 day
3	day
0.0224
0.0193
0.0202
0.0213
0.0537
0.0688
0.5389
0.9087
0.1766
0.0020
0.0019
0.0006
0.0016
0.6793
0.0569
0.0035
0.0613
0.0029
0.0770
0.2423
Light shading indicates significant differences
As with the persistence and flushing evaluations, statistical analyses were performed
using t-tests to further clarify any differences among the data from each flushing scenario. Table
14 gives the p-values for comparisons of each possible set of coupons collected at the various
time intervals. The significant differences are highlighted in gray. For both CCAs, samples at
each time interval were significantly different from the contaminated control at the 95%
confidence level. The calcium chloride results then steadied at the 2 hr concentration while the
ammonium acetate exhibited significant differences at later time points, driven by the increase in
residual strontium concentration at those time intervals. It is not clear why this increase
occurred. The data suggest that calcium chloride removed 90% of the adhered strontium and is a
good candidate for decontamination. Application of ammonium acetate yielded similar results,
although the unexplained apparent increase in strontium after application may negate its
effectiveness.
4.9 Water Quality Measurements
Throughout this evaluation the pH, temperature, and free chlorine concentration of the
tap water was measured daily. The pH of the tap water was on average 7.4 +1-0.2. The average
free chlorine concentration of the tap water was measured to be 1.3 mg/L +/-0.3mg/L. The
average temperature of the tap water was 15.5 °C +/-6°C (this includes summer and winter
months).
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5.0 RESULTS SUMMARY
The objective of this study was to collect data pertaining to the persistence of surrogate
radiological contaminants on concrete-lined and/or PVC pipe coupons and possible
decontamination approaches. Several key points are summarized below.
5.1	Collection of Surrogate Radiological Persistence Data
Use of the AR proved to be an effective means of reproducibly simulating the flow of
water past pipe materials, contaminating the coupons with cesium, cobalt, and strontium, and
simulating a water distribution system. The surface extraction and surface contamination
method validation steps were necessary to demonstrate whether or not the radiological surrogates
could be studied (if it cannot be extracted it will be difficult to study its persistence) and if it is a
viable threat (if a contaminant will not partition onto a pipe from an aqueous solution, it may not
be a decontamination concern). These method validation steps were demonstrated with a limited
number of replicates for cesium, cobalt, and strontium. Each of these method validations could
be more rigorously tested. Tests could include more replicates or additional separate experiments
that optimize certain components of the extraction such as sonication time and extraction acid.
5.2	Persistence and Decontamination Testing
The surface extraction method validation confirmed that cesium, cobalt, and strontium
could be extracted from the surface of concrete after direct contamination of the coupon. The
surface contamination method validation confirmed that a coupon could be contaminated with
cesium, cobalt, and strontium by exposing it to a solution of contaminated water. The results
from the persistence evaluation are summarized below:
•	Cesium was not persistent on concrete or PVC pipe materials
•	Cobalt was very persistent on concrete, but less persistent on PVC
•	Strontium was persistent on concrete, but not on PVC.
Results from the decontamination portion of the study are as follows:
•	Flushing was not effective for cobalt or strontium on concrete
•	EDTA was an effective chemical cleaning agent for cobalt on concrete.
•	Tartaric acid was an effective chemical cleaning agent for cobalt on concrete, but it
formed a yellow precipitate on the surface of the coupons.
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•	Ammonium acetate and calcium chloride were both moderately effective as chemical
cleaning agents for strontium on concrete.
•	None of the contaminants were persistent on PVC pipe materials, so chemical
cleaning agents were not evaluated on PVC.
5.3 Future Research Needs
The water system decontamination research area is one with many factors to be explored.
Listed below are possible areas for further study:
•	Biofilm is a factor that impacts surface adsorption of contaminants. Additional work
could be performed to determine more information about the role of biofilm in
persistence and decontamination of contaminants from pipe material.
•	Broadening of the adsorption/decontamination data set by expanding on the list of
chemical contaminants and examining biological contaminants.
•	Use of additional pipe materials as well as additional decontamination agents.
•	Scaling up of AR experiments to experiments with real pipe in order to study how well
the AR experiments translate into a large scale scenario.
•	Comparison of the PDEDP with an experimental design that does not include flowing
water (5). Such a design may be easier and cheaper to implement.
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6.0 REFERENCES
1.	ASTM C 150-07 Standard, 2007, "Standard Specification for Portland Cement," ASTM
International, West Conshohocken, PA, www.astm.org.
2.	American Water Works Association C104-03 Standard, 2004, "Standard for Cement-
Mortar Lining for Ductile-Iron Pipe and Fittings for Water" Denver, CO: AWWA
Research Foundation, www.awwa.org.
3.	Szabo, J.G., Impellitteri, C,A., Govindaswamy, S., Hall, J.S. 2009., Persistence and
decontamination of surrogate radioisotopes in a model drinking water distribution
system, Water Research (2009), doi:10.1016/j.watres.2009.08.012.
4.	U.S. Environmental Protection Agency. Method 200.8 (Revision 5.4): Determination of
Trace Elements in Waters and Wastes by Inductively Coupled Plasma - Mass
Spectrometry. Cincinnati, OH: U.S. Environmental Protection Agency, Office of
Research and Development, Environmental Monitoring Systems Laboratory.
5.	Welter, G., M. Lechevallier, S. Spangler, J. Cotruvo, R. Moser, Guidance for
Decontamination of Water System Infrastructure. Denver, CO: AWWA Research
Foundation, 2007.
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vvEPA
United States
Environmental Protection
Agency
PRESORTED STANDARD
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
Office of Research and Development (8101R)
Washington, DC 20460
Official Business
Penalty for Private Use
$300

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