October 2005
Environmental Technology
Verification Report
ANALYTICAL TECHNOLOGY, INC.
Q45WQ CONTINUOUS
MULTI-PARAMETER WATER QUALITY
MONITOR
Prepared by
Battelle
Baireiie
Ira Business erf Innovation
Under a cooperative agreement with
U.S. Environmental Protection Agency
ET/ET1/ET1/
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October 2005
Environmental Technology Verification
Report
ETV Advanced Monitoring Systems Center
ANALYTICAL TECHNOLOGY, INC.
Q45WQ CONTINUOUS MULTI-
PARAMETER WATER QUALITY MONITOR
by
Ryan James
Amy Dindal
Zachary Willenberg
Karen Riggs
Battelle
Columbus, Ohio 43201
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THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM
ET/
«U PA Bairene
^^^™ • * Ue Business o/Innov;
.S. Environmental Protection Agency
ETV Joint Verification Statement
TECHNOLOGY TYPE: MULTI-PARAMETER WATER MONITORS FOR
DISTRIBUTION SYSTEMS
APPLICATION: MONITORING DRINKING WATER QUALITY
TECHNOLOGY NAME: Q45WQ Series
COMPANY: Analytical Technology, Inc.
ADDRESS: 6 Iron Bridge Drive PHONE: 610-917-0991
Collegeville, Pennsylvania 19426 FAX: 610-917-0992
WEB SITE: www.analyticaltechnology.com
E-MAIL: sales @ analyticaltechnology.com
The U.S. Environmental Protection Agency (EPA) supports the Environmental Technology Verification (ETV)
Program to facilitate the deployment of innovative or improved environmental technologies through performance
verification and dissemination of information. The goal of the ETV Program is to further environmental protection
by accelerating the acceptance and use of improved and cost-effective technologies. ETV seeks to achieve this
goal by providing high-quality, peer-reviewed data on technology performance to those involved in the design,
distribution, financing, permitting, purchase, and use of environmental technologies. Information and ETV
documents are available at www.epa.gov/etv.
ETV works in partnership with recognized standards and testing organizations, with stakeholder groups
(consisting of buyers, vendor organizations, and permitters), and with individual technology developers. The
program evaluates the performance of innovative technologies by developing test plans that are responsive to the
needs of stakeholders, conducting field or laboratory tests (as appropriate), collecting and analyzing data, and pre-
paring peer-reviewed reports. All evaluations are conducted in accordance with rigorous quality assurance (QA)
protocols to ensure that data of known and adequate quality are generated and that the results are defensible.
The Advanced Monitoring Systems (AMS) Center, one of six technology areas under ETV, is operated by Battelle
in cooperation with EPA's National Exposure Research Laboratory. The AMS Center evaluated the performance
of the Analytical Technology, Inc., (ATI) Q45WQ Series water quality monitor in continuously measuring free
chlorine, turbidity, temperature, conductivity, pH, and oxidation-reduction potential (ORP) in drinking water. This
verification statement provides a summary of the test results.
VERIFICATION TEST DESCRIPTION
The performance of the Q45WQ was assessed in terms of its accuracy, response to injected contaminants, inter-
unit reproducibility, ease of use, and data acquisition. The verification test was conducted between August 9 and
October 28, 2004, and consisted of three stages, each designed to evaluate a particular performance characteristic
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of the Q45WQ. All three stages of the test were conducted using a recirculating pipe loop at the U.S. EPA's Test
and Evaluation Facility in Cincinnati, Ohio.
In the first stage of this verification test, the accuracy of the measurements made by the Q45WQ units was
evaluated during eight, 4-hour periods of stable water quality conditions by comparing each Q45WQ unit
measurement to a grab sample result generated each hour using a standard laboratory reference method and then
calculating the percent difference (%D). The second stage of the verification test involved evaluating the response
of the Q45WQ units to changes in water quality parameters by injecting contaminants (nicotine, arsenic trioxide,
and aldicarb) into the pipe loop. Two injections of three contaminants were made into the recirculating pipe loop
containing finished Cincinnati drinking water. The response of each water quality parameter, whether it was an
increase, decrease, or no change, was documented and is reported here. In the first phase of Stage 3 of the
verification test, the performance of the Q45WQ units was evaluated during 52 days of continuous operation,
throughout which references samples were collected once daily. The final phase of Stage 3 (which immediately
followed the first phase of Stage 3 and lasted approximately one week) consisted of a two-step evaluation of the
Q45 WQ performance to determine whether this length of operation would negatively impact the results from the
Q45 WQ. First, as during Stage 1, a reference grab sample was collected every hour during a 4-hour analysis
period and analyzed using the standard reference methods. Again, this was done to define a formal time period of
stable water quality conditions over which the accuracy of the Q45WQ could be evaluated. Second, to evaluate
the response of the Q45WQ to contaminant injection after the extended deployment, the duplicate injection of
aldicarb, which was also included in the Stage 2 testing, was repeated. In addition, a pure E. coli culture, including
the E. coli and the growth medium, was included as a second injected contaminant during Stage 3. Inter-unit
reproducibility was assessed by comparing the results of two identical units operating simultaneously. Ease of use
was documented by technicians who operated and maintained the units, as well as the Battelle Verification Test
Coordinator.
QA oversight of verification testing was provided by Battelle and EPA. Battelle QA staff conducted a technical
systems audit, a performance evaluation audit, and a data quality audit of 10% of the test data.
This verification statement, the full report on which it is based, and the test/QA plan for this verification test are
all available at www.epa.gov/etv/centers/centerl.html.
TECHNOLOGY DESCRIPTION
The following description of the Q45WQ unit was provided by the vendor and does not represent verified
information.
The Q45WQ unit can be customized based on users' needs to include various monitoring devices. The unit
verified during this test included sensors for pH, conductivity, free chlorine, ORP, temperature, and turbidity. The
purpose of the unit is to provide an integrated package of monitors that can be deployed throughout water
distribution systems to collect general water quality data and transmit it to remote locations, giving water
companies access to real-time data from throughout their systems.
In this verification test, pH was measured using a differential pH sensor containing two glass pH electrodes, one
for sensing and another in buffer to serve as a reference electrode. ATI informed Battelle that, during the same
time period as this verification test, several users of its pH sensors reported a drift in the pH measurement similar
to that observed during testing. ATI stated that it determined that a problem with the salt bridge assembly was
causing the downward drift, which impacted not only the accuracy of the pH measurement, but also of the
chlorine measurement. According to ATI, the problem was subsequently corrected. Conductivity was measured
with a four-electrode conductivity sensor that measures the current-carrying capacity of the water. ORP was
measured in millivolts with a differential ORP sensor containing a platinum sensing electrode and separate glass
electrode in buffer to serve as a reference electrode. A membrane-covered amperometric (polarographic) sensor
provided direct chlorine response without the need for chemical reagents. The conductivity sensor provided the
output for both the conductivity and temperature measurements. Turbidity was measured with a 90-degree scatter
nephelometer, using an infrared light source for stability and a sealed flow chamber to reduce bubble formation.
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The Q45WQ unit that was tested was 24 inches wide by 47 inches high. The units normally provide 4-20 mA
outputs for each parameter and can be connected to virtually any type of user-specified data acquisition system.
During this verification test, ATI provided HOBO® data loggers from Onset Computer Corp. (Bourne,
Massachusetts) to collect the data. Data points were collected every 30 seconds. The data logger generated a file
with a .dtf suffix that required conversion to a delimited text file using software from Onset. This file was then
imported into Microsoft Excel prior to further data analysis. These data loggers were downloaded daily using a
serial port on a personal computer and Onset's Boxcar® software. The cost of the unit as configured for the
verification test is $1 1,500. In addition, ATI estimates that the total cost of replacement parts is approximately
$150 per year. This includes replacement membranes, electrolytes, O-rings on the chlorine sensor, and the salt
bridge on the pH and ORP electrodes. Total labor required for preventive maintenance is approximately one hour
per month.
VERIFICATION OF PERFORMANCE
Evaluation Parameter
Stage 1—
Accuracy
Stage 2—
Response to
Injected
Contaminants
Stage 3—
Accuracy During
Extended
Deployment
Stage 3 —
Accuracy After
Extended
Deployment
Stage 3 —
Response to
Injected
Contaminants
Injection
Summary
Inter-unit
Reproducibility
(Unit 2 vs. Unit 1)
Ease of Use
and Data
Acquisition
Units 1 and 2, range
of %D (median)
Nicotine
Arsenic
trioxide
Aldi-
carb
Reference
Q45WQ
Reference
Q45WQ
Reference
Q45WQ
Units 1 and 2,
range of %D
(median)
Unit 1, %D
Unit 2, %D
E. coli
Aldi-
carb
Reference
Q45WQ
Reference
Q45WQ
Free
Chlorine
-4 1.5 to
54.3 (-15.7)
-
-
-
-
-
-
-33.7 to
29.7 (-7.3)
1.1
-1.1
-
-
-
-
Turbidity
-47.2 to
-16.9 (-24.9)
(b)
+
(b)
+
(b)
+
-88.0 to
18.2 (-42.3)
-5.9
11.8
+
+
+
+
Tem-
perature
-5.5 to
1.3 (-1.4)
NC
NC
NC
NC
NC
NC
-4.9 to
1.5 (-1.4)
0.0
-0.9
NC
NC
NC
NC
Conduc-
tivity
-19.7 to
-2.6 (-12.7)
NC
NC
+
+
NC
NC
-19.4 to
-5.3 (-13.6)
-14.0
-7.9
+(0
NC
NC
NC
pH
-11.8 to
-0.9 (-5.0)
NC
NC
+
+
NC
NC
-8.3 to
1.5 (-3.5)
0.1
-2.2
-
-
-
(c)
ORP
(a)
-
-
-
-
-
-
(a)
(a)
(a)
-
-
-
-
For a reason that is not clear, aldicarb altered the pH, as measured by the reference method, during
the Stage 3 injections, but not during the Stage 2 injections.
Slope (intercept)
r2
p-value
0.88 (0.10)
0.77
0.59
0.97 (0.028)
0.99
0.76
0.97(0.31)
1.00
0.41
1.09 (-1.1)
0.97
0.00020
0.71 (2.4)
0.85
0.48
0.89 (40)
0.96
0.0093
The ORP and conductivity sensor generated results that were significantly different from one another.
Each unit's results were highly correlated with one another; but, because of the small degree of
variability in each sensor's results, they were significantly different.
Based on the performance of the free chlorine and pH sensors, the pH sensor may have to be adjusted
periodically to maintain the accuracy of both measurements. No other maintenance was necessary
during the test.
(a) ORP was not included in the accuracy evaluation because of the lack of an appropriate reference method.
(b) Relatively large uncertainty in the reference measurements made it difficult to determine a significant change.
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Original signed by Gregory A. Mack 10/17/05 Original signed by Andrew P. Avel 1/17/06
Gregory A. Mack Date Andrew P. Avel Date
Assistant Division Manager Acting Director
Energy, Transportation, and Environment Division National Homeland Security Research Center
Battelle U.S. Environmental Protection Agency
NOTICE: ETV verifications are based on an evaluation of technology performance under specific,
predetermined criteria and the appropriate quality assurance procedures. EPA and Battelle make no expressed or
implied warranties as to the performance of the technology and do not certify that a technology will always
operate as verified. The end user is solely responsible for complying with any and all applicable federal, state,
and local requirements. Mention of commercial product names does not imply endorsement.
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Notice
The U.S. Environmental Protection Agency (EPA), through its Office of Research and
Development, has financially supported and collaborated in the extramural program described
here. This document has been peer reviewed by the Agency. Mention of trade names or
commercial products does not constitute endorsement or recommendation by the EPA for use.
11
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
nation's air, water, and land resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this
mandate, the EPA's Office of Research and Development provides data and science support that
can be used to solve environmental problems and to build the scientific knowledge base needed
to manage our ecological resources wisely, to understand how pollutants affect our health, and to
prevent or reduce environmental risks.
The Environmental Technology Verification (ETV) Program has been established by the EPA to
verify the performance characteristics of innovative environmental technology across all media
and to report this objective information to permitters, buyers, and users of the technology, thus
accelerating the entrance of new environmental technologies into the marketplace. Verification
organizations oversee and report verification activities based on testing and quality assurance
protocols developed with input from major stakeholders and customer groups associated with the
technology area. ETV consists of six verification centers. Information about each of these
centers can be found on the Internet at http://www.epa.gov/etv/.
Effective verifications of monitoring technologies are needed to assess environmental quality
and to supply cost and performance data to select the most appropriate technology for that
assessment. Under a cooperative agreement, Battelle has received EPA funding to plan,
coordinate, and conduct such verification tests for "Advanced Monitoring Systems for Air,
Water, and Soil" and report the results to the community at large. Information concerning this
specific environmental technology area can be found on the Internet at
http://www.epa.gov/etv/centers/centerl.html.
111
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Acknowledgments
The authors wish to acknowledge the support of all those who helped plan and conduct the
verification test, analyze the data, and prepare this report. We would like to thank Roy Haught
and John Hall of the U.S. Environmental Protection Agency's (EPA's) Test and Evaluation
(T&E) Facility (operated by Shaw Environmental, Inc. [Shaw]) in Cincinnati, Ohio, for hosting
the verification test. The U.S. EPA primary contract to Shaw provided significant support in
interfacing the continuous monitors with the pipe loop, as well as facilitating the experimental
plan. The T&E Facility's contribution included providing the reference analyses and operating
the pipe loop, as well as reviewing the test/quality assurance (QA) plan and the reports. In
addition, we would like to thank Steve Allgeier of EPA's Office of Water, Gary Norris and Alan
Vette of the EPA National Exposure Research Laboratory, Lisa Olsen of the U.S. Geological
Survey, Matthew Steele of the City of Columbus Water Quality Assurance Laboratory, and Ron
Hunsinger of East Bay Municipal Utility District, who also reviewed the test/QA plan and/or the
reports.
IV
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Contents
Page
Notice ii
Foreword iii
Acknowledgments iv
List of Abbreviations viii
1 Background 1
2 Technology Description 2
3 Test Design 4
3.1 Introduction 4
3.2 Test Stages 4
3.2.1 Stage 1, Accuracy 5
3.2.2 Stage 2, Response to Injected Contaminants 5
3.2.3 Stage 3, Extended Deployment 6
3.3 Laboratory Reference and Quality Control Samples 6
3.3.1 Reference Methods 7
3.3.2 Reference Method Quality Control Samples 8
4 Quality Assurance/Quality Control 9
4.1 Audits 9
4.1.1 Performance Evaluation Audit 9
4.1.2 Technical Systems Audit 10
4.1.3 Audit of Data Quality 10
4.2 Quality Assurance/Quality Control Reporting 10
4.3 Data Review 10
5 Statistical Methods 12
5.1 Accuracy 12
5.2 Response to Injected Contaminants 12
5.3 Inter-unit Reproducibility 13
6 Test Results 14
6.1 Accuracy 15
6.2 Response to Injected Contaminants 19
6.3 Extended Deployment 23
6.4 Accuracy and Response to Injected Contaminants After Extended Deployment ... 29
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6.5 Inter-unit Reproducibility 33
6.6 Ease of Use and Data Acquisition 34
7 Performance Summary 36
8 References 37
Figures
Figure 2-1. Analytical Technology, Inc. Q45WQ 2
Figure 6-1. Stage 2 Contaminant Injection Results for Free Chlorine 20
Figure 6-2. Stage 2 Contaminant Injection Results for ORP 21
Figure 6-3. Stage 2 Contaminant Injection Results for Turbidity 21
Figure 6-4. Stage 2 Contaminant Injection Results for pH 22
Figure 6-5. Stage 2 Contaminant Injection Results for Conductivity 22
Figure 6-6. Extended Deployment Results for Free Chlorine 24
Figure 6-7. Extended Deployment Results for pH 24
Figure 6-8. Extended Deployment Results for ORP 25
Figure 6-9. Extended Deployment Results for Temperature 25
Figure 6-10. Extended Deployment Results for Conductivity 26
Figure 6-11. Extended Deployment Results for Turbidity 26
Figure 6-12. Stage 3 Contaminant Injection Results for Free Chlorine 31
Figure 6-13. Stage 3 Contaminant Injection Results for ORP 31
Figure 6-14. Stage 3 Contaminant Injection Results for Turbidity 32
Figure 6-15. Stage 3 Contaminant Injection Results for pH 32
Figure 6-16. Stage 3 Contaminant Injection Results for Conductivity 33
vi
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Tables
Table 3-1. Reference Methods 7
Table 3-2. Reference Analyses and Quality Control Samples 8
Table 4-1. Performance Evaluation Audit and Reference Method
Duplicate Analysis Results 10
Table 4-2. Summary of Data Recording Process 11
Table 6-1. Summary of Test Stages and Type of Data Presentation 14
Table 6-2a. Accuracy Evaluation Under Various Conditions—Free Chlorine 15
Table 6-2b. Accuracy Evaluation Under Various Conditions—Turbidity 16
Table 6-2c. Accuracy Evaluation Under Various Conditions—Temperature 17
Table 6-2d. Accuracy Evaluation Under Various Conditions—Conductivity 18
Table 6-2e. Accuracy Evaluation Under Various Conditions—pH 18
Table 6-3. Effect of Contaminant Injections Prior to Extended Deployment 20
Table 6-4. Accuracy During Extended Deployment 27
Table 6-5. Post-Extended Deployment Results 29
Table 6-6. Effect of Contaminant Injections After Extended Deployment 30
Table 6-7. Inter-unit Reproducibility Evaluation 34
vn
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List of Abbreviations
AMS Advanced Monitoring Systems
ATI Analytical Technology, Inc.
cm centimeter
°C degree centigrade
DI deionized
EPA U.S. Environmental Protection Agency
ETV Environmental Technology Verification
L liter
|iS/cm microSiemens per centimeter
mg/L milligram per liter
NIST National Institute of Standards and Technology
ntu nephelometric turbidity unit
ORP oxidation reduction potential
%D percent difference
PE performance evaluation
PVC polyvinyl chloride
QA quality assurance
QC quality control
QMP quality management plan
SD standard deviation
T&E Test and Evaluation
TSA technical systems audit
Vlll
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Chapter 1
Background
The U.S. Environmental Protection Agency (EPA) supports the Environmental Technology
Verification (ETV) Program to facilitate the deployment of innovative environmental
technologies through performance verification and dissemination of information. The goal of the
ETV Program is to further environmental protection by accelerating the acceptance and use of
improved and cost-effective technologies. ETV seeks to achieve this goal by providing high-
quality, peer-reviewed data on technology performance to those involved in the design,
distribution, financing, permitting, purchase, and use of environmental technologies.
ETV works in partnership with recognized testing organizations; with stakeholder groups
consisting of buyers, vendor organizations, and permitters; and with the full participation of
individual technology developers. The program evaluates the performance of innovative
technologies by developing test plans that are responsive to the needs of stakeholders,
conducting field or laboratory tests (as appropriate), collecting and analyzing data, and preparing
peer-reviewed reports. All evaluations are conducted in accordance with rigorous quality
assurance (QA) protocols to ensure that data of known and adequate quality are generated and
that the results are defensible.
The EPA's National Exposure Research Laboratory and its verification organization partner,
Battelle, operate the Advanced Monitoring Systems (AMS) Center under ETV. The AMS Center
evaluated the performance of the Analytical Technology, Inc. (ATI) Q45WQ Series water
quality monitor in continuously measuring free chlorine, turbidity, temperature, conductivity,
pH, and oxidation-reduction potential (ORP), in drinking water. Continuous multi-parameter
water monitors for distribution systems were identified as a priority technology verification
category through the AMS Center stakeholder process.
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Chapter 2
Technology Description
The objective of the ETV AMS Center is to verify the performance characteristics of
environmental monitoring technologies for air, water, and soil. This verification report provides
results for the verification testing of the Q45WQ water quality monitor. Following is a
description of the Q45WQ, based on information provided by the vendor. The information
provided below was not verified in this test.
The Q45WQ unit (Figure 2-1) can be customized based on users' needs to include various
monitoring devices. The unit verified during this test included sensors for pH, conductivity, free
chlorine, ORP, temperature, and turbidity. The purpose of the unit is to provide an integrated
package of monitors that can be deployed
throughout water distribution systems to collect
general water quality data and transmit it to remote
locations, giving water companies access to real-
time data from throughout their systems.
In this verification test, pH was measured using a
differential pH sensor containing two glass pH
electrodes, one for sensing and another in buffer to
serve as a reference electrode. Conductivity was
measured with a four-electrode conductivity sensor
that measures the current-carrying capacity of the
water. ORP was measured in millivolts with a
differential ORP sensor containing a platinum
sensing electrode and separate glass electrode in
buffer to serve as a reference electrode. A
membrane-covered amperometric (polarographic)
sensor provided direct chlorine response without
the need for chemical reagents. The conductivity
monitor provided the output for both the
conductivity and temperature measurements.
Turbidity was measured with a 90-degree scatter
nephelometer, using an infrared light source for
stability and a sealed flow chamber to reduce
bubble formation.
Figure 2-1. Analytical Technology, Inc.,
Q45WQ
The Q45WQ unit that was tested was 24 inches wide by 47 inches high. The units normally
provide 4-20 mA outputs for each parameter and can be connected to virtually any type of
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user-specified data acquisition system. During this verification test, ATI provided HOBO® data
loggers from Onset Computer Corp. (Bourne, Massachusetts) to collect the data. Data points
were collected every 30 seconds. The data logger generated a file with a .dtf suffix that required
conversion to a delimited text file using software from Onset. This file was then imported into
Microsoft Excel prior to further data analysis. These data loggers were downloaded daily using a
serial port on a personal computer and Onset's Boxcar® software. The cost of the unit as
configured for the verification test is $11,500. In addition, ATI estimates that the total cost of
replacement parts is approximately $150 per year. This includes replacement membranes,
electrolytes, O-rings on the chlorine sensor, and the salt bridge on the pH and ORP electrodes.
Total labor required for preventive maintenance is approximately one hour per month.
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Chapter 3
Test Design
3.1 Introduction
The multi-parameter water monitors tested consisted of instrument packages that connect to or
are inserted in distribution system pipes for continuous monitoring. Also included in this
technology category were technologies that can be programmed to automatically sample and
analyze distribution system water at regular intervals. The minimum requirement for
participation in this verification test was that the water monitors were able to measure residual
chlorine, as well as at least one other water quality parameter. Residual chlorine is a particularly
important water quality parameter because changes in its concentration can indicate the presence
of contamination within a distribution system, and chlorination is a very common form of water
treatment used by water utilities in the United States.
This verification test was conducted according to procedures specified in the Test/QA Plan for
Verification of Multi-Parameter Water Monitors for Distribution Systems^ and assessed the
performance of the Q45WQ units in continuously monitoring pH, conductivity, free chlorine,
ORP, temperature, and turbidity in terms of the following:
• Accuracy
• Response to injected contaminants
• Inter-unit reproducibility
• Ease of use and data acquisition.
Accuracy was quantitatively evaluated by comparing the results generated by two Q45WQ units
to grab sample results generated by a standard laboratory reference method. Response to injected
contaminants was evaluated qualitatively by observing whether the measured water quality
parameters were affected by the injection of several contaminants. Inter-unit reproducibility was
assessed by comparing the results of two identical Q45WQ units operating simultaneously. Ease
of use was documented by technicians who operated and maintained the units, as well as the
Battelle Verification Test Coordinator.
3.2 Test Stages
This verification test was conducted between August 9 and October 28, 2004, and consisted of
three stages, each designed to evaluate a particular performance characteristic of the Q45WQ
units. All three stages of the test were conducted using a recirculating pipe loop at the U.S.
EPA's Test and Evaluation (T&E) Facility in Cincinnati, Ohio. The recirculating pipe loop
consisted of ductile iron pipe, 6 inches in diameter and 100 feet long, which contained
approximately 240 gallons of Cincinnati drinking water with a flow rate of approximately
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1 foot/second. The water within the pipe loop had a residence time of approximately 24 hours.
Water from the pipe loop was plumbed to two Q45WQ units by a 2-inch section of polyvinyl
chloride (PVC) pipe in series with a shut-off valve with a ribbed nozzle that was connected to
the Q45WQ units with a 1/2-inch PVC hose and a hose clamp. Reference samples of
approximately 1 liter (L) (enough volume to perform all the required analyses) to be analyzed by
each standard laboratory reference method were collected from the reference sample collection
valve located approximately 23 feet from the Q45WQ units on the PVC pipe.
3.2.1 Stage 1, Accuracy
During the first stage of this verification test, the accuracy of the measurements made by both
Q45WQ units was evaluated by comparing the results from each unit to the result generated by a
standard laboratory reference method. Stage 1 testing simulated the characteristics of a variety of
water quality conditions by changing two variables: pH and temperature. Using eight sets of pH
and temperature conditions, this evaluation consisted of separate four-hour testing periods of
continuous analysis, with reference method sampling and analysis every hour. Four sets of
conditions involved varying only the pH by injecting the pipe loop with a steady stream of
sodium bisulfate. Those sets consisted of pHs of approximately 7, 8, and 9 pH units (ambient pH
at the T&E Facility was between 8 and 9) and a temperature between 21 and 23 degrees
centigrade (°C) (T&E Facility ambient during the time of testing). Two other sets included
changing the water temperature to between 12 and 14°C and testing at pHs of approximately 7
and 8; and two sets at approximately these pHs, but at a temperature of approximately 27°C. The
pipe loop ambient conditions were analyzed at the start and end of this stage. Prior to each
testing period with unique conditions, the water in the pipe loop was allowed to equilibrate until
the pH and temperature were at the desired level, as determined by the standard reference
methods. This equilibration step took approximately 12 hours from the time the sodium bisulfate
was added (to decrease pH) or the temperature was adjusted.
3.2.2 Stage 2, Response to Injected Contaminants
The second stage of the verification test involved testing the response of the Q45WQ units to
changes in water quality parameters by injecting contaminants into the pipe loop, i.e., testing
whether the water quality parameter continuous monitors changed in a positive or negative
direction upon the injection of a contaminant. Two injections of three contaminants were made
into the recirculating pipe loop containing finished Cincinnati drinking water. Each injection was
made over a period of approximately 15 seconds by connecting the injection tank to the pipe
loop's recirculating pump. The three contaminants were nicotine, arsenic trioxide (adjusted to
pH 12 to get it into solution), and aldicarb. With the exception of the first nicotine injection, each
of these contaminants was dissolved in approximately 5 gallons of pipe loop water that had been
dechlorinated using granular carbon filtration to prevent degradation of the contaminant prior to
injection. Upon injection, concentrations of these contaminants within the pipe loop were
approximately 10 milligrams per liter (mg/L). For the first nicotine injection, however, not
enough nicotine to attain this concentration was available so the available nicotine was dissolved
into 2 gallons of the dechlorinated pipe loop water and injected. The resulting nicotine
concentration in the pipe loop was approximately 6 mg/L. Because the qualitative change in
water quality parameters was similar for both nicotine injections despite the concentration
difference, it was not necessary to repeat the 10 mg/L injection of nicotine. For all three sets of
injections, a reference sample was collected prior to the injection and again at 3, 15, and
5
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60 minutes after the injection. The difference between reference method results occurring before
and then again after each injection indicated the directional change in water quality caused by
the injected contaminant. For each injected contaminant, the results from the Q45WQ units were
evaluated based on how well their directional change matched the reference measurement result.
After each injection, the pipe loop was allowed to re-equilibrate for approximately 12 hours so
that each Q45WQ unit returned to a steady baseline. Injected contaminants were obtained from
Sigma-Aldrich (St. Louis, Missouri) or ChemService (West Chester, Pennsylvania) and were
accompanied by a certificate of analysis provided by the supplier. Battelle QA staff audited the
gravimetric preparation of these solutions.
3.2.3 Stage 3, Extended Deployment
In the first phase of Stage 3 of the verification test, the performance of the Q45WQ units was
evaluated during 52 days of continuous operation. The Q45WQ units required no regularly
scheduled maintenance during this deployment. To track the performance of the Q45WQ units
with respect to the reference results, reference samples were collected and analyzed for the
selected parameters at least once per day (excluding weekends and holidays) for the duration of
Stage 3. All continuously measured data were graphed, along with the results from the reference
measurements, to provide a qualitative evaluation of the data. Throughout the duration of the
deployment, the average percent difference (%D), as defined in Section 5.1, between the results
from the Q45WQ units and those from the reference methods was evaluated.
The final phase of Stage 3 (which immediately followed the first phase of Stage 3 and lasted
approximately one week) consisted of a two-step evaluation of the Q45WQ unit performance
after the 52-day extended deployment to determine whether this length of operation would
negatively impact the results from the Q45WQ. First, while the Q45WQ units were continuously
operating, a reference sample was collected every hour during a 4-hour analysis period and
analyzed using the standard reference methods. This was done to define a formal time period of
stable water quality conditions for the accuracy of the Q45WQ to be evaluated. Second, to
evaluate the response of the Q45WQ units to contaminant injection after the extended
deployment, the duplicate injection of aldicarb, which was also included in the Stage 2 testing,
was repeated. In addition, a pure E. coli culture, including the E. coli and the growth medium,
was included as a second injected contaminant during Stage 3. E. coli was intended as an
injected contaminant during Stage 2, but was not available until later in the test. During this
contaminant injection component of Stage 3, reference samples were collected as they were
during Stage 2.
3.3 Laboratory Reference and Quality Control Samples
The Q45WQ units were evaluated by comparing their results with laboratory reference
measurements. The following sections provide an overview of the applicable procedures,
analyses, and methods.
-------
3.3.1 Reference Methods
To eliminate the possibility of using stagnant water residing in the reference sample collection
valve (dead volume) as the reference samples, the first step in the reference sample collection
procedure included collecting and discarding approximately 1 L of water, which was estimated
to be approximately 10 times the dead volume of the reference sample collection value. Then,
from the same valve, approximately 1 L of water was collected in a glass beaker and carried
directly to a technician, who immediately began the reference analyses. All the analyses were
performed within minutes of sample collection. The standard laboratory methods used for the
reference analyses are shown in Table 3-1. Also included in the table are method detection limits
and quality control (QC) measurement differences. Battelle technical staff collected the
reference samples, and technical staff at the T&E Facility performed the analyses. The T&E
Facility provided calibrated instrumentation, performed all method QA/QC, and provided
calibration records for all instrumentation. The T&E Facility provided reference sample results
upon the analysis of the reference samples (within one day). Because previous work at the T&E
facility(2) showed that the laboratory reference method for ORP using a grab sample is not
directly comparable to a continuous measurement in a flowing pipe, accuracy results were not
included for ORP. ORP reference and continuous measurement results were, however, included
for the purpose of a qualitative data evaluation in figures showing the continuous data and
reference method results. Although the ORP reference value may not be equivalent to the
continuous measurement, changes in the continuous measurements were evaluated with the
reference results to determine whether the sensor was identifying increases and decreases
correctly.
Table 3-1. Reference Methods
Parameter
Method
Reference Instruments
Method Detection
Limit
Acceptable
Differences for QC
Measurements
PH
Conductivity
Free chlorine
ORP(a)
Temperature
Turbidity
EPA 150.1(3)
SM2510(4)
SM 4500-G(5)
SM2580-B(6)
EPA 170.1(7)
EPA 180.1(8)
Corning 320 pH meter
YSI556 multi-parameter
water monitor
Hach 2400 portable
spectrophotometer
YSI 556 multi-parameter
water monitor
YSI 556 multi-parameter
water monitor
Hach 21 OOP turbidimeter
NA
2 microSiemens/
centimeter (|iS/
cm)
0.01mg/LasCl2
NA
NA
0.067
nephelometric
turbidity unit (ntu)
tO.3 pH units
±25 %D
±25 %D
±25 %D
±1°C
±25 %D
-------
3.3.2 Reference Method Quality Control Samples
As shown in Table 3-2, duplicate reference samples were collected and analyzed once daily
during Stages 1 and 2 and weekly during Stage 3. Also, laboratory blanks consisting of
American Society for Testing and Materials Type n deionized (DI) water were analyzed with the
same frequency. Reference analyses of these blank samples were most important for chlorine
and turbidity because they were the only parameters that needed confirmation of the lack of
contamination. For the other parameters, the performance evaluation (PE) audit confirmed the
accuracy of the method and the absence of contamination. Duplicate measurements had to be
within the acceptable differences provided in Table 3-1.
Table 3-2. Reference Analyses and Quality Control Samples
1:
2:
3:
Stage
Accuracy
Response to
injected
contaminants
Extended
deployment
Reference Reference
Sampling Sample Samples QC Samples per Total QC
Periods (length) Frequency per Period Period Samples
One at start, one
8 (4 hours) every hour
thereafter
One pre-injection;
, , . . .. , one at 3, 15, and
6 (one in ection) „ .
60 minutes post-
injection
1 /co A \ Once each
1 (52 days) , ,
weekday
One duplicate and
5 one DI water blank
daily
One duplicate and
4 one DI water blank
daily
One duplicate and
37 one DI water blank
each week
16
12
16
3: Post-extended
deployment
accuracy
1 (4 hours) Same as Stage 1
Same as Stage 1
3: Response to
injected
contaminants
4 (one injection) Same as Stage 2
Same as Stage 2
-------
Chapter 4
Quality Assurance/Quality Control
QA/QC procedures were performed in accordance with the quality management plan (QMP) for
the AMS Center(9) and the test/QA plan(1) for this verification test.
4.1 Audits
4.1.1 Performance Evaluation Audit
A PE audit was conducted to assess the quality of the reference measurements made in this
verification test. With the exception of temperature, each type of reference measurement was
compared with a National Institute of Standards and Technology (NIST)-traceable standard
reference water sample. The standard reference water samples had certified values of each water
quality parameter that were unknown to the analyst. These samples were analyzed in the same
manner as the rest of the reference analyses to independently confirm the accuracy of the
reference measurements. The temperature PE audit was performed by comparing two
independent thermometer results. As Table 4-1 shows, all PE audit results were within the
acceptable differences provided in Table 3-2. The percent difference (%D) was calculated using
the following equation:
C - C
%D= — xlOO%
where CR was the reference method result and CN the NIST value (or, for temperature, data from
the second thermometer) for each respective water quality parameter. Other QC data collected
during this verification test were reference method duplicate analysis results, which are also
shown in Table 4-1. With the exception of one duplicate measure of turbidity, all parameters
were always within the differences defined in Table 3-2. Because pH units are measured on a
logarithmic, rather than linear, scale, and the measurement of temperature is extremely precise;
the quality control metrics for those two parameters were the absolute units rather than percent
difference. No corrective action was taken for the one turbidity measurement (55.2%) that was
outside the acceptable difference. If this outlier is removed, the upper range of percent
differences was 18.2% and the average absolute value of differences was 5.4%.
-------
Table 4-1. Performance Evaluation Audit and Reference Method Duplicate Analysis
Results
Parameter
pH
Conductivity (|iS/cm)
Free chlorine (mg/L)
Temperature (°C)
Turbidity (ntu)
NIST
Standard
Value
9.26
1,920
4.19
23.80(a)
20
PE Audit
Reference
Method
Result
9.18
1,706
3.62
23.80
22.3
Difference
-0.08 pH units
-11.1%
-13.6%
0.00°C
11.5%
Duplicate Analysis
Average of
Absolute Values Range of
of Difference Difference
0.04 pH units 0.0 to 0. 1 3 pH units
0.25% -1.9 to 0.7%
2.62% -7.3 to 2.1%
0.02°C -0.18to0.29°C
7.49% -8.7 to 55.2%
ORP was not included in the accuracy evaluation because of the lack of an appropriate reference method.
(a) Since a standard for temperature does not exist, the PE audit for temperature was performed by comparing the
results with those from a second thermometer.
4.1.2 Technical Systems Audit
The Battelle Quality Manager performed a technical systems audit (TSA) to ensure that the
verification test was performed in accordance with the AMS Center QMP,(9) the test/QA plan,(1)
published reference methods, and any standard operating procedures used by the T&E Facility.
The TSA noted no adverse findings. A TSA report was prepared, and a copy was distributed to
the EPA AMS Center Quality Manager.
4.1.3 Audit of Data Quality
At least 10% of the data acquired during the verification test was audited. Battelle's Quality
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 also were checked.
4.2 Quality Assurance/Quality Control Reporting
Each assessment and audit was documented in accordance with Sections 3.3.4 of the QMP for
the ETV AMS Center.(9) Once the assessment report was prepared, the Battelle Verification Test
Coordinator ensured that a response was provided for each adverse finding or potential problem
and implemented any necessary follow-up corrective action. The Battelle Quality Manager
ensured that follow-up corrective action was taken. The results of the TSA were sent to the EPA.
4.3 Data Review
Records generated in the verification test were reviewed before these records were used to
calculate, evaluate, or report verification results. Table 4-2 summarizes the types of data
recorded. The review was performed by a technical staff member involved in the verification
test, but not the staff member who originally generated the record.
10
-------
Table 4-2. Summary of Data Recording Process
Data to Be
Recorded
Where Recorded
How Often
Recorded
By
Whom
Disposition of
Data
Dates, times, and
details of test
events
ETV data sheets
and testing
notebook
Start/end of test and
at each change of a
test parameter
Battelle
and T&E
Facility
Used to organize/
check test results;
manually
incorporated in
data spreadsheets
as necessary
Calibration
information
(Q45WQ units and
reference methods)
ETV data sheets
and testing
notebook
Upon each
calibration
Battelle
and T&E
Facility
Manually
incorporated in
data spreadsheets
as necessary
Q45WQ unit
results
Recorded
electronically by
each unit and then
downloaded to
computer daily
Recorded
continuously
Battelle Comma delimited
text files.
Reference method
procedures
ETV laboratory
record books or
data recording
forms
Throughout sample T&E
analysis process Facility
Transferred to
spreadsheets or
laboratory record
book
11
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Chapter 5
Statistical Methods
The statistical methods presented in this chapter were used to verify the Q45WQ units' accuracy,
response to injected contaminants, and inter-unit reproducibility.
5.1 Accuracy
Throughout this verification test, results from the Q45WQ units were compared to the results
obtained from analysis of a grab sample by the reference methods. During Stage 1, the percent
difference between these two results was calculated using the following equation:
C - C
%D= —^—-x 100%
where CR is the result determined by the reference method and Cm is the result from a Q45WQ
unit; the Q45WQ unit results were recorded every 30 seconds, whereas collecting the reference
samples took only a few seconds. Therefore, Cm was the measurement recorded closest to the
time the reference sample was collected. Water quality stability, as well as the stability of each
sensor, was evaluated during the four-hour time period when reference samples were analyzed
every hour for each of the parameters. Ideally, if the result from a Q45WQ unit and a reference
method measurement were the same, there would be a percent difference of zero. It should be
noted that the formula for percent difference is sensitive to reference results that are small in
magnitude. For example, if the reference turbidity is 0.1 ntu, and the online instrument reads 0.2,
the percent difference is 100%. Alternatively, if the reference turbidity is 1.0 ntu, and the online
instrument reads 1.1, the percent difference is only 10%. During Stages 2 and 3, the continuous
data, graphed with the reference method results, were visually examined to evaluate the response
of the Q45WQ unit to the injection of contaminants and their stability over an extended
deployment. During the accuracy and contaminant injection components of Stage 3, the data
were evaluated as they were for Stages 1 and 2, respectively.
5.2 Response to Injected Contaminants
To evaluate the response (i.e., the increase or decrease of water quality parameter measured by
the Q45WQ units) to contaminant injections, the pre- and post-injection reference samples were
graphed as individual data points, along with the continuous measurements. The reference
results showed the effect of each injection on the chemistry of the water in the pipe loop, and the
continuous results from the Q45WQ units highlighted their response to such changes.
12
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5.3 Inter-unit Reproducibility
The results obtained from two identical Q45WQ units were compared to assess inter-unit
reproducibility. Each time a reference sample was collected and analyzed (approximately
127 times throughout this verification test), the results from each Q45WQ unit were compared to
evaluate whether the two units were generating similar results. This was done in two ways. First,
the results from one unit were graphed against the results of the other unit. In this evaluation, a
slope of unity and a coefficient of determination of 1.0 would indicate ideal inter-unit
reproducibility. Slopes above 1.0 may indicate a high bias from Unit 2 (graphed on the y-axis) or
a low bias for Unit 1 with respect to each other. Similarly, slopes below 1.0 may indicate a low
bias for Unit 2 or a high bias for Unit 1, again with respect to each other. Second, the data from
each unit were included in a paired t-test, with the assumption that the data from each unit had
equal variances. The t-test calculated the probability of obtaining the subject results from the two
units if there was no significant difference between their results. Therefore, probability values
(p-values) of less than 0.05 (i.e., less than a 5% probability that this data set would be generated
if there actually was no difference between the two units) indicated a significant difference
between the two units. In addition, the results from both units were graphed together for the
Stages 2 and 3 results, allowing a visual comparison.
13
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Chapter 6
Test Results
As mentioned previously, this verification test was conducted in three stages that focused on
three different aspects of multi-parameter water monitors for distribution systems. The three
stages are summarized in Table 6-1. The first stage consisted of an evaluation (with varied pHs
and temperatures) of the accuracy of each Q45WQ sensor: free chlorine, turbidity, temperature,
conductivity, and pH. ORP was also measured; but, because a laboratory reference measurement
equivalent to the on-line continuous measurement was not available, ORP was not included in
the accuracy evaluation. The second stage of the verification test consisted of an evaluation of
the response of the Q45WQ units to the injection of several contaminants into the pipe loop. The
third stage consisted of deploying the Q45WQ units for 52 consecutive days with minimal
intervention for maintenance. In addition, contaminant injections were performed at the close of
Stage 3 to confirm that the Q45WQ units were still responsive to contaminant injection after the
extended deployment. Two Q45WQ units were tested to evaluate inter-unit reproducibility. In
addition, required maintenance and operational characteristics were documented throughout the
verification test. This chapter provides the results of the three testing stages, the inter-unit
reproducibility data, and ease of use information.
Table 6-1. Summary of Test Stages and Type of Data Presentation
Stage Summary
Data Presentation
1 Accuracy when pH and temperature
were varied
Table of percent differences between
Q45WQ units and reference measurements
Response to contaminant injection
Graphs of Q45WQ unit measurements and
reference measurements, table showing the
effect of injections on both reference and
Q45WQ measurements
Extended deployment with minimal
maintenance along with post-extended
deployment accuracy and response to
contaminant injections
Graphs of Q45WQ unit measurements with
reference measurements, table showing
average percent differences throughout
extended deployment, table showing the
effect of injections on both reference and
Q45WQ measurements
14
-------
6.1 Accuracy
Tables 6-2a-e list the data from the accuracy evaluation performed during the first stage of the
verification test. During four-hour periods, the water quality conditions were held stable, and
reference samples were collected and analyzed five times, once at the start of the designated test
period and four times at one-hour increments thereafter. Because reference sample collection
took just a few seconds, and the results from the Q45WQ units were recorded every 30 seconds,
the water quality parameter measurement at the time closest to reference sample collection was
compared to the reference sample. For each unit, this approach resulted in five paired Q45WQ
and reference results for each of the eight sets of water conditions used to simulate pH and
temperature variations at a water utility. The average and standard deviations of these five results
are shown in the tables below, as well as the percent difference between the average results from
both Q45WQ units and the average of the reference results.
Table 6-2a. Accuracy Evaluation Under Various Conditions—Free Chlorine
Set
1
2
3
4
5
6
7
8
Conditions
ambient pH,
ambient temperature
decreased pH, ambient
temperature
decreased pH, ambient
temperature
ambient pH, decreased
temperature
decreased pH, decreased
temperature
ambient pH, increased
temperature
decreased pH, increased
temperature
ambient pH, ambient
temperature
Reference
Average (SD)
[mg/L]
0.94 (0.04)
0.65 (0.01)
0.29 (0.02)
0.41 (0.08)
1.47 (0.06)
0.60 (0.04)
0.54 (0.05)
0.91 (0.03)
Unitl
Average (SD)
[mg/L]
1.17(0.01)
0.38 (0.04)
0.18(0.01)
0.41 (0.01)
1.00(0.04)
0.48 (0.01)
0.40 (0.03)
0.73 (0.02)
%D
24.5
-41.5
-37.9
0.0
-32.0
-20.0
-25.9
-19.8
Unit 2
Average (SD)
[mg/L]
1.45 (0.01)
0.57 (0.00)
0.19 (0.01)
0.54 (0.01)
1.19 (0.04)
0.67 (0.01)
0.49 (0.05)
1.10(0.05)
%D
54.3
-12.3
-34.5
31.7
-19.0
11.7
-9.3
20.9
15
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Table 6-2b. Accuracy Evaluation Under Various Conditions—Turbidity
Reference
Unit 1 Unit 2
Average (SD) Average (SD) Average (SD)
Set Conditions [ntu] [ntu] % D [ntu] %D
1 an*ientPH' 0.88(0.07) 0.64(0.02) -27.3 0.66(0.03) -25.0
ambient temperature
2 decreased pH, ambient 0.97 (0.33) 0.64(0.04) -34.0 0.73(0.05) -24.7
temperature
3 decreased pH, ambient L54 (0.20) 1.28(0.06) -16.9 1.24(0.06) -19.5
temperature
4 ambient pH, decreased 0.89(0.41) 0.53(0.21) -40.4 0.47(0.07) -47.2
temperature
5 decreased pH, 0.99(0.21) 0.79(0.03) -20.2 0.81(0.04) -18.2
decreased temperature
6 ambient pH, increased 0.92(0.16) 0.70(0.02) -23.9 0.69(0.02) -25.0
temperature
? decreased pH, increased 1-00(0-35) 0.77(0.01) -23.0 0.76(0.01) -24.0
temperature
8 ambient pH, ambient 0.46(0.11) 0.29(0.03) -37.0 0.31(0.03) -32.6
temperature
16
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Table 6-2c. Accuracy Evaluation Under Various Conditions—Temperature
Reference
Unit 1 Unit 2
Average (SD) Average (SD) Average (SD)
Set Conditions [°C] [°C] %D [°C] %D
1 an*ientPH> 22.60(0.33) 22.58(0.31) -0.1 22.12(0.36) -2.1
ambient temperature
2 decreased pH, ambient 21.66(0.08) 21.72(0.11) 0.3 21.14(0.09) -2.4
temperature
3 decreased pH, ambient 21.93(0.15) 21.76(0.17) -0.8 21.62(0.47) -1.4
temperature
4 ambient pH, decreased 13 82 (0.44) 13.60(0.26) -1.6 13.66(0.88) -1.2
temperature
5 decreased pH, 12.63(0.26) 12.16(0.23) -3.7 11.94(0.22) -5.5
decreased temperature
6 ambient pH, increased 26.60(0.27) 26.94(0.25) 1.3 26.44(0.25) -0.6
temperature
decreased pH, increased 2669(023) 26.78(0.11) 0.3 26.30(0.22) -1.5
temperature
8 Ambient pH, ambient 2279(021) 22.24 (0.37) -2.4 21.98(0.41) -3.6
temperature
17
-------
Table
Set
1
2
3
4
5
6
7
8
Table
Set
1
2
3
4
5
6
7
8
6-2d. Accuracy Evaluation Under Various Conditions — Conductivity
Conditions
ambient pH,
ambient temperature
decreased pH, ambient
temperature
decreased pH, ambient
temperature
ambient pH, decreased
temperature
decreased pH,
decreased temperature
ambient pH, increased
temperature
decreased pH, increased
temperature
ambient pH, ambient
temperature
Reference
Average (SD)
[|j,S/cm]
451(1)
503 (6)
694 (12)
412(1)
501 (10)
447 (1)
529 (2)
442 (1)
Unitl
Average (SD)
[[iS/cm]
362 (4)
421 (13)
587 (27)
335 (0)
417 (9)
388 (5)
464 (4)
384 (0)
%D
-19.7
-16.3
-15.4
-18.7
-16.8
-13.2
-12.3
-13.1
Unit 2
Average (SD)
[[iS/cm]
390 (9)
443 (14)
649 (24)
362 (8)
456 (9)
431 (4)
515 (5)
419 (5)
%D
-13.5
-11.9
-6.5
-12.1
-9.0
-3.6
-2.6
-5.2
6-2e. Accuracy Evaluation Under Various Conditions — pH
Conditions
ambient pH,
ambient temperature
decreased pH, ambient
temperature
decreased pH, ambient
temperature
ambient pH, decreased
temperature
decreased pH, decreased
temperature
ambient pH, increased
temperature
decreased pH, increased
temperature
ambient pH, ambient
temperature
Reference
Average (SD)
[pH units]
8.76 (0.02)
7.52 (0.04)
6.73 (0.12)
8.48 (0.02)
7.31 (0.08)
8.37 (0.05)
7.60 (0.06)
8.74 (0.01)
Unitl
Average (SD)
[pH units]
8.60 (0.00)
7.08 (0.04)
6.04 (0.05)
8.20 (0.00)
6.62 (0.08)
7.68 (0.04)
6.70 (0.00)
8.00 (0.00)
%D
-1.8
-5.9
-10.3
-3.3
-9.4
-8.2
-11.8
-8.5
Unit 2
Average (SD)
[pH units]
8.60 (0.00)
7.30 (0.00)
6.30(0.10)
8.40 (0.00)
7.00 (0.07)
8.16 (0.05)
7.10(0.00)
8.40 (0.00)
%D
-1.8
-2.9
-6.4
-0.9
-4.2
-2.5
-6.6
-3.9
18
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Of the parameters that were evaluated for accuracy, the free chlorine percent differences (with
the median shown in parentheses) ranged from -41.5 to 54.3 (-15.7); for turbidity, -47.2 to -16.9
(-24.9), for temperature, -5.5 to 1.3 (-1.4), for conductivity, -19.7 to -2.6 (-12.7), and for pH,
-11.8 to -0.9 (-5.0).1 These ranges show that the free chlorine sensor generated results with the
largest spread of percent differences compared to the reference method. The results may be
because of the chlorine sensor's dependence on pH correction. As will be discussed in
Section 6.3, regular calibration of the pH sensor was required to maintain accurate free chlorine
measurements. Periodically, the accuracy of the pH sensor drifted, affecting the free chlorine
results. The standard deviations of the reference and continuous measurements collected during
each test period were, with few exceptions, very small with respect to the average result. In only
a few instances was the standard deviation greater than 5% of the average result. This shows
both that the water conditions during these test periods were very stable and that there was very
little variability in the sensors themselves. The results were not remarkably different among the
various sets of water quality conditions; therefore, the Q45WQ unit performance was apparently
not dependent on the water conditions.
6.2 Response to Injected Contaminants
Six injections of contaminants were performed during the second stage of this verification test;
i.e., duplicate injections of nicotine, arsenic trioxide, and aldicarb. Table 6-3 shows the
directional change of each reference and Q45WQ measurement in response to the contaminant
injections. In general, free chlorine and ORP were the only parameters clearly affected (for both
the reference and continuous measurements) by all six injections. Figures 6-1 through 6-5 show
the responses of free chlorine, ORP, turbidity, pH, and conductivity. The blue and yellow lines
on the graphs represent the measurements made by each Q45WQ unit, and the magenta data
points represent the results from the laboratory reference method. Because accuracy was the
focus of the first stage of verification testing, percent differences between the Q45WQ units and
the reference method results are not presented here; however, the reference method results are
included in these figures to confirm that the fluctuations in the continuous results are due to
changes in water chemistry as the result of the injected contaminants. The figures are divided
with vertical lines that define the approximate time period for each injection. Each injection time
period defined on the figures is approximately 24 hours, but the times vary somewhat depending
on when chlorine was added to restore the system to pre-injection conditions. The contaminant
that was injected and whether it was the first or second replicate are shown at the top of each
section of the figures. For each injection, at least four reference sample results were collected,
and are included in these figures. The first occurred within approximately one hour prior to
contaminant injection during a period of stable water quality conditions. The next three reference
data points were from samples collected 3, 15, and 60 minutes after contaminant injection. For
some of the injections, another reference sample was collected the following day to show that
the pipe loop system had recovered or was in the process of recovering after the injection. This
1 Throughout this report, median values are provided when a range of values is presented. The median of a set of
positive and negative numbers provides a good indicator of the overall direction of the percent differences in the
data set (i.e., whether most values were positive or negative). The disadvantage is that, unless the signs of all the
data are the same, information about the magnitude of change is not available from the median. In summary, the
medians in this report provide the direction, not magnitude, of difference information.
19
-------
Table 6-3. Effect of Contaminant Injections Prior to Extended Deployment
Nicotine
Arsenic Trioxide
Aldicarb
Parameter Reference Q45WQ Reference Q45WQ Reference W45WQ
Free chlorine
Turbidity
Temperature
Conductivity
pH
ORP
-
(a)
NC
NC
NC
-
-
+
NC
NC
NC
-
_ _
(a) (a)
NC NC NC
+ + NC
+ + NC
- - -
-
+
NC
NC
NC
-
r" Relatively large uncertainty in the reference measurements made it difficult to detect a significant change.
+/- = Parameter measurement increased/decreased upon injection.
NC = No change in response to the contaminant injection.
final reference data point also served as the first reference sample collected for some of the
injections, representing the stable baseline just prior to injection.
Figure 6-1 shows how the measurement of free chlorine was affected by the contaminant
injections. Prior to the injections, the free chlorine level was maintained at approximately
1 mg/L, as is evidenced by the magenta data points near the start of each section of the figure. In
— Unitl
* Reference
Unit 2
Each section (separated by vertical lines) represents approximately 24 hours.
Figure 6-1. Stage 2 Contaminant Injection Results for Free Chlorine
20
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1200
1000
Nicotine 1 Nicotine 2 Arsenic 1 Arsenic 2 Aldicarb 1 Aldicarb2
— Unrtl
* Reference
Unit 2
Each section (separated by vertical lines) represents approximately 24 hours.
Figure 6-2. Stage 2 Contaminant Injection Results for ORP
Figure 6-3. Stage 2 Contaminant Injection Results for Turbidity
21
-------
9.5
9
8.5
8
7.5 -
7 -
6.5 -
6 -
5.5 -
Nicotine 1
f *
^
Nicotine 2
i
^
Arsenic 1
%
t
* +
\
1^-
Arsenic 2
*
t
»*
1.
4,
Aldicart 1
^
JH I —
Aldicart 2
**
_j~l
— Unitl
* Reference
Unit 2
Each section (separated by vertical lines) represents approximately 24 hours.
Figure 6-4. Stage 2 Contaminant Injection Results for pH
600
550 n
£500
|450-
Nil :cre 1
icotine 2
Arsenic 1
Arsenic 2
Aldicart 1
Aldicarb 2
— Unitl
* Reference
Unit 2
300
Each section (separated by vertical lines) represents approximately 24 hours.
Figure 6-5. Stage 2 Contaminant Injection Results for Conductivity
22
-------
each case, within one hour of contaminant injection, the free chlorine level, as measured by the
laboratory reference method, dropped to near zero. As shown by the vertical drop in the line
representing the free chlorine concentration, it was clear that the chlorine sensor on the Q45WQ
units responded to the drop in free chlorine levels as a result of the presence of the contaminant.
For each injection, the drop to nearly zero free chlorine levels was followed by the restoration of
the pipe loop system to approximately pre-injection conditions through the addition of sodium
hypochlorite. This is shown in Figure 6-1 by the rapidly increasing free chlorine concentration
after the sensor reached a low point in free chlorine concentration following each injection. The
ORP in water is highly dependent on the occurrence of oxidation-reduction chemical reactions
within the water. Therefore, when free chlorine is reacting with injected contaminants, it can be
expected that the ORP would be affected. Figure 6-2 shows that this parameter tracked the
concentration of free chlorine upon injection of the contaminants. However, it is not conclusive
whether the change in ORP is due to the change in chlorine or to the presence of the
contaminants. Additional controls would be needed to make that determination. Note that the
offset between Unit 1 and Unit 2 was due to a loose wire to Unit 1's data logger. That problem
was corrected by ATI during Stage 3 of the verification test.
Figure 6-3 shows the turbidity measurements during the contaminant injections. As for the other
water parameters, the reference samples were collected prior to the contaminant injection and at
3, 15, and 60 minutes following the contaminant injection. Therefore, each cluster of magenta
symbols on the figure indicate when a contaminant injection had occurred. However, for all the
injections except the second arsenic injection, the level of turbidity measured by the reference
method decreased from the time the pre-injection reference sample was collected until the
subsequent reference samples were collected and analyzed. This suggests that 1) the contaminant
injections did not increase the turbidity in the flowing water or, 2) that the uncertainty in the
reference measurements was too large to determine whether turbidity was significantly affected.
Because the continuous turbidity measurement of the Q45WQ seemed to increase at least
slightly (through a visual inspection of the data) with each injection, it seems that the latter
scenario is more likely to be the case. For the nicotine injections, the change in turbidity
according to the Q45WQ measurements was very small, while the changes during the arsenic
and aldicarb injections were slightly more pronounced. Because each of these contaminants was
dissolved in water prior to injection, these observed increases could have been due to changes in
the optical properties of the water resulting from the dissolution of the contaminant or the
co-injection of small amounts of air, introducing a few bubbles into the pipe, thus causing an
increase in turbidity. Note that during the latter half of the first and second nicotine injections
and just prior to the final aldicarb injection, there were turbidity spikes that were not due to the
injection of any contaminants. Apparently, some outside perturbations in the water system
caused these brief events. For both pH and conductivity, there was a small increase measured by
both the reference and continuous measurements during the injection of arsenic trioxide only.
For both water quality parameters, the increase may have been due to the pH adjustment
required to get this contaminant into solution.
6.3 Extended Deployment
Figures 6-6 through 6-11 show the continuous measurements from both Q45WQ units during the
52-day extended deployment stage of the verification test. Those measurements are represented
by the blue and yellow lines, while the results of the reference samples, collected once daily
23
-------
— Unitl
* Reference
Unrt2
Duration of Stage 3: 52 days
Figure 6-6. Extended Deployment Results for Free Chlorine
10
9.5 -
9 -
8.5 -
8 -
7.5
— Unitl
» Reference
Unit 2
Duration of Stage 3: 52 days
Figure 6-7. Extended Deployment Results for pH
24
-------
1200
1000 -_
800
600
400 -
200 -
— Unitl
* Reference
Unit 2
Duration of Stage 3: 52 days
Figure 6-8. Extended Deployment Results for ORP
18
15
Duration ot Stage 3: 52 days
Figure 6-9. Extended Deployment Results for Temperature
25
-------
01
500
450
400
350 -
300
250 -
200
150 -\
100
50 -\
0
\^fff^^
Duration of Stage 3: b2 days
Figure 6-10. Extended Deployment Results for Conductivity
o
7 -
6 -
5 -
4 -
3 -
2 -
1 -
n
»
Event
#1
\
-* ?_ !>?**•• 1
— Unitl
* Reference
Unit 2
I
V t ** I
^^LUX: t^.,* ^ 1 1 , j . ^
Duration of Stage 3: 52 days
Figure 6-11. Extended Deployment Results for Turbidity
26
-------
throughout this deployment, are represented by the magenta symbols. The x-axis on each figure
represents the period of time between September 1, 2004, and October 22, 2004, while the y-axis
gives the results of each water quality measurement. Data points were recorded every 30 seconds
during the verification test; and, for the extended deployment figures, only data points collected
approximately every 2 minutes were depicted. This was done so that a standard spreadsheet could
be used to generate these figures. This approach was inconsequential to interpreting figures.
The objective of this stage of the verification test was to evaluate the performance of the Q45WQ
units over an extended period of time with minimal intervention to simulate a situation in which
the units may be deployed at a remote location. The continuous trace was evaluated visually to
see whether any aspects of the data were noteworthy. A second, more quantitative, evaluation was
then performed to get an indication of the accuracy of the extended deployment measurements.
This evaluation, much like the accuracy evaluation conducted during the first stage of testing,
included calculating the percent differences between the average continuous measurements and
average reference sample results throughout the extended deployment, as well as the standard
deviation of each of those measurements. The standard deviation of the results provided a means
to evaluate the stability of the water conditions during Stage 3, as well as how the standard
deviations of the continuous measurements differed from the standard deviations of the reference
measurements. Similar relative standard deviations between the continuous and reference
measurements indicate that the variability was mostly dependent on the water conditions and not
due to systematic variability in the Q45WQ unit results. (Note that reference results were only
generated during business hours, so any fluctuations occurring during off hours are not reflected
in the standard deviation of the reference results. Because of this, free chlorine, a parameter that
varied at times during weekends when the supply of chlorine ran low, might have been expected
to have a larger variability than other more stable parameters.) Table 6-4 lists the percent
differences, along with the average and standard deviations of the reference and continuous
results during the extended deployment. The range and median (see the footnote in Section 6.1 for
direction on interpreting the median) percent difference for each water quality parameter, as
measured for each reference sample analyzed during the extended deployment, are also given.
Table 6-4. Accuracy During Extended Deployment
(a)
Parameter
Free chlorine
Turbidity
Temperature
Conductivity
PH
Reference
Average
(SD)(a)
0.95(0.10)
0.73 (1.55)
22.83 (0.36)
335 (57)
8.72 (0.07)
Unitl
Average (SD)(a)
0.99
0.29
22.65
285
8.54
(0.21)
(0.64)
(0.30)
(51)
(0.30)
%D
4
-60
-0.
-14
_2.
.2
.8
8
.9
1
Unit 2
Average (SD)(a)
0.79
0.32
22.35
319
8.28
(0.17)
(0.64)
(0.32)
(54)
(0.17)
%D
-16.8
-56.2
-2.1
-4.8
-5.0
Both Units %D
Range (median)
-33.7 to
-88.0 to
-4.9 to
-19.4 to
-8.3 to
29.7 (-7.3)
18.2 (-42.3)
1.5 (-1.4)
-5.3 (-13.6)
1.5 (-3.5)
Free chlorine, mg/L; turbidity, ntu; temperature, °C; conductivity, |_iS/cm; pH, pH units.
For free chlorine, visual inspection of the data in Figure 6-6 revealed that, for the first
approximately one-third of the extended deployment, the free chlorine measurements were
approximately 0.7 mg/L (with some variation) for both units, while the reference method
measurements ranged from approximately 0.8 mg/L to 1.1 mg/L. At that point, the ATI
representative visited the testing facility and adjusted the pH sensor (that works in concert with
27
-------
the free chlorine sensor) to correct the free chlorine measurement to match the reference method
result (free chlorine Event #1 in Figure 6-6). When this was done, both Q45WQ units tracked the
free chlorine reference measurements rather well until the supply of sodium hypochlorite (used to
maintain the chlorine concentrations in the pipe loop) ran low after a weekend (free chlorine
Event #2). When this occurred, the chlorine level dropped significantly from background levels.
After this variation, the chlorine sensor on Q45WQ Unit 1 recovered to a measurement somewhat
higher than the reference results, and the Q45WQ Unit 2 recovered to a measurement somewhat
lower than the reference result (free chlorine Event #3). Unit 1 continued to have a higher
measurement until near the end of the extended deployment when the results from the two units
abruptly converged to a measurement slightly higher than the reference measurement. This
marked the time that ATI again adjusted the pH sensor to match the reference method result (free
chlorine Event #4). During the extended deployment, the percent differences for both units ranged
from -33.7 to 29.7, with a median of -7.3. The average free chlorine concentration, as measured
by the reference method, was 0.95 mg/L ± 0.10 mg/L. Prior to the first pH adjustment, the percent
difference ranged from -33.7 to -16.9, with a median of -24.7; and, after the pH sensor
adjustment, the average percent difference ranged from -29.9 to 29.7, with a median of 4.6. The
accuracy of the free chlorine sensor on the Q45WQ units was heavily dependent on the accuracy
of the pH sensor that is used to correct the chlorine measurement.
The pH results presented in Figure 6-7 reflect the adjustments made to the pH sensor during the
verification test. For the first approximately one-third of the extended deployment, Units 1 and 2
were measuring the pH as approximately 8.0, while the reference method was measuring it as
approximately 8.8. At that time, ATI made the adjustment to the pH sensor to bring both units'
measurements in line with the reference measurement. This is shown by the abrupt convergence
of both Unit 1 and 2 measurements with the reference measurement (pH Event #1 in Figure 6-7).
After that point, the Unit 1 pH sensor was more accurate than Unit 2, which seemed to drift
lower. Near the end of the extended deployment, ATI adjusted the pH results again in both units
so both of their results were in line with the reference results (pH Event #2). Again, this is shown
by the abrupt convergence of all three measurements. The average pH, as measured by the
reference method, was 8.72 ± 0.07, and the average pH as measured by Q45WQ Units 1 and 2
was 8.54 ± 0.30 and 8.28 ± 0.17, respectively. Overall, during the extended deployment, the
percent difference for the pH sensors ranged from -8.3 to 1.5, with a median of -3.5. ATI
informed Battelle that, during the same time period as this verification test, several users of its pH
sensors reported a similar drift in the pH measurement. ATI determined that a problem with the
salt bridge assembly was causing the downward drift, which affected not only the accuracy of the
pH measurement, but also of the chlorine measurement. ATI subsequently corrected this problem.
The other four water quality parameters were not affected by the pH adjustment. The ORP,
temperature, conductivity, and turbidity sensors were allowed to operate without intervention
throughout the extended deployment. The measurements from these four sensors are shown in
Figures 6-8 through 6-11. In Figure 6-8, the ORP results are shown along with a laboratory
reference method result. The reference method is not an accurate representation of water in a
flowing pipe, but it can be used to evaluate a trend in the decrease and increase in the ORP, as it
was in the previous section for the contaminant injections. With the exception of Unit 1 for the
first one-third of the extended deployment, the ORP results were steady with few abrupt increases
or decreases. The large consistent positive bias in the Unit 1 results early in the extended
deployment was caused by a loose wire extending from the ORP sensor to the data collection
port, which was corrected by ATI (ORP Event #1 in Figure 6-8).
28
-------
The temperature, conductivity, and turbidity results for both Units 1 and 2 mostly tracked the
reference method results throughout the extended deployment. The temperature results from both
Units 1 and 2 had regular variability because the test was conducted in a facility where the water
temperature was heavily affected by the outdoor temperature; therefore, the water temperature
changed as a function of the high and low for the day. No aspects of the conductivity or turbidity
results were notable, except for a turbidity spike that lasted for approximately a day (turbidity
Event #1 in Figure 6-11), which occurred about half-way through the stage and was measured by
both the Q45WQ units and the reference method. It was not evident what caused this spike. In
addition, in the early part of Stage 3, the continuous turbidity results were generally lower than
the reference method result; however, this improved during the second half of the stage. Note that
the missing Unit 2 conductivity and temperature data from the latter part of this stage (see Figures
6-9 and 6-10) were the result of a problem with the data logger used with the Q45WQ. The data
logger was replaced just prior to the end of this stage of the test.
6.4 Accuracy and Response to Injected Contaminants After Extended Deployment
After the 52-day deployment of the Q45WQ units with minimal intervention, their performance
was evaluated during a 4-hour period of ambient pH and temperature during which reference
samples were collected hourly. The results of this evaluation are given in Table 6-5. With the
exception of free chlorine and turbidity, these results seemed comparable to those collected
during Stage 1. During Stage 1, the free chlorine percent differences ranged from -41.5% to
+54.3%. During this final stage, the percent differences were less than 2%. This improvement is
because the pH sensors were adjusted to match the reference result just prior to Stage 3. For
turbidity, the Stage 1 results ranged from -47.2 to -16.9; while, during this final stage, the percent
differences were -5.9% and 11.8%. The reason for this improvement in turbidity measurements is
not apparent.
Table 6-5. Post-Extended Deployment Results
(a)
Parameter
Free chlorine
Turbidity
Temperature
Conductivity
PH
Reference
Average (SD)(a)
0.92 (0.02)
0.17(0.02)
22.66 (0.16)
356(1)
8.59 (0.01)
Unitl
Average (SD)(a)
0.93 (0.03)
0.16(0.03)
22.65 (0.17)
306 (0)
8.60 (0.00)
%D
1.1
-5.9
0.0
-14.0
0.1
Unit 2
Average (SD)(a)
0.91 (0.02)
0.19(0.03)
22.45 (0.10)
328 (5)
8.40 (0.00)
%D
-1.1
11.8
-0.9
-7.9
-2.2
Free chlorine, mg/L; turbidity, ntu; temperature, °C; conductivity, |_iS/cm; pH, pH units.
A second evaluation of the response to injected contaminants after the extended deployment used
four contaminants. Two were a repeat of the aldicarb injections performed during Stage 2 and two
were injections of E. coli, which was not available for injection during the earlier stage of the test.
Table 6-6 shows the directional change of each reference and Q45WQ measurement in response
to the contaminant injections. Figures 6-12 through 6-16 show the effect of the injections on free
chlorine, ORP, turbidity, pH, and conductivity. In general, free chlorine, ORP, and turbidity were
the only parameters visibly affected (for both the reference and continuous measurements) by all
four injections. The response and recovery of the continuous chlorine sensor was consistent for all
29
-------
four injections and, as during Stage 2, the ORP sensor tracked the chlorine response for each
injection. Turbidity seemed to be affected by all four injections as well, but the results were not as
consistent. For example, the first aldicarb injection produced an increase in turbidity of only 0.12
ntu, while the first and second E. coli injections and the second aldicarb injection produced
increases according to the reference method of 0.82, 0.43, and 1.03 ntu, respectively. Because of
the inherent turbidity of an E. coli culture, it was expected that turbidity would be consistently
responsive to that contaminant. Also, because aldicarb was completely dissolved, it was not
expected to increase the turbidity of the water upon injection. However, the conditions
surrounding the injection of both contaminants, such as the co-injection of air bubbles, may have
affected the turbidity as much as or more than the contaminant itself. Regardless of what caused
the variable turbidity, the continuous monitor tracked the relative magnitude of the change in
turbidity rather well.
Table 6-6. Effect of Contaminant Injections After Extended Deployment
Parameter
Free chlorine
Turbidity
Temperature
Conductivity
PH
ORP
E. coli
Reference Q45WQ
-
+ +
NC NC
+(a) NC
-
-
Aldicarb
Reference Q45WQ
-
+ +
NC NC
NC NC
(a)
-
(a) Results from duplicate injections did not agree.
+/- = Parameter measurement increased/decreased upon injection.
NC = No change in response to the contaminant injection.
The pH was clearly affected by both E. coli injections (as shown by both the reference and
continuous measurements) and, to a lesser extent, by the aldicarb injections. The reference
method displayed a slight decrease for both aldicarb injections, while the continuous measure-
ment only detected a change during the final aldicarb injection. In addition, during the E. coli
injections, a very slight increase in conductivity was measured by the reference method; however,
no such change was detected by the continuous measurement. Aldicarb had not altered the pH
during the Stage 2 injections, so this result was unexpected. The continuous measurements were
similar to these results for the E. coli injections and the second aldicarb injection.
The conductivity results increased according to the reference method for the first injection of
E. coli. However, for the continuous measurements for all of the injections and the reference
measurements for the rest of the injections, there was very little effect. Note that an unexplained
occurrence of high variability in Unit 2 took place during the final aldicarb injection.
30
-------
«i.J
2 -
1.5 -
O)
E
1 -
0.5 -
n
Benin
(**
I
E. colt 2
* r
u /
Aldicarb 3
4
N
f
X~
r
Altficarb 4
•
*
/'
.
— Unitl
* Reference
Unit 2
Figure 6-12. Stage 3 Contaminant Injection Results for Free Chlorine
Each section (separated by vertical lines) lepresents appioximately 24 hours.
Figure 6-13. Stage 3 Contaminant Injection Results for ORP
31
-------
E. COS 2
Aldicart4
Each section (separated by vertical lines) lepresents approximately 24 hours.
Figure 6-14. Stage 3 Contaminant Injection Results for Turbidity
»
8.8 -
8.6 -
8.4 -
8.2 -
8
7.8 -
7.6 -
7.4 -
7.2 -
7
E. coil 1
«5J1 |—
\ -I
r^
F
IT
*
E ca&2
1— 1
•
1
j
I
Aldicarb 3
*
*
Aldicarb 4
J t
f
4
— Unitl
* Reference
Unit 2
Each section (separated by vertical lines) represents approximately 24 hours.
Figure 6-15. Stage 3 Contaminant Injection Results for pH
32
-------
450
400 -
o
u
£
Figure 6-16. Stage 3 Contaminant Injection Results for Conductivity
6.5 Inter-unit Reproducibility
Two Q45WQ units were compared throughout the verification test to determine whether they
generated results that were similar to one another. This was done using the Q45WQ data collected
whenever a reference sample was collected throughout the verification test. Two evaluations were
performed to make this comparison. First, the results from Unit 2 were graphed on the y-axis,
those from Unit 1 were graphed on the x-axis, and a line was fitted to the data. Second, a t-test
assuming equal variances was performed on those same data. For the linear regression analysis, if
both units reported the identical result, the slope of such a regression would be unity (1), the
intercept zero (0), and the coefficient of determination (r2) 1.0. The slope can indicate whether the
results are biased in one direction or the other, while the coefficient of determination provides a
measure of the variability of the results. The t-test shows whether the sensors generated
statistically similar data. Small p-values (<0.05 at a 5% confidence level) would suggest that the
results from the two units are significantly different from one another. Table 6-7 gives the slope,
intercept, and coefficient of determination for the regression inter-unit reproducibility evaluation
and the p-value for the t-test performed for each sensor.
As can be seen from Table 6-7, the temperature and turbidity sensors had coefficients of
determination greater than 0.99 and slopes of 0.97, indicating that their results were very similar
and repeatable. Confirming that evaluation, the t-test p-values for temperature and turbidity were
0.41 and 0.76, respectively, indicating that each sensor generated statistically similar results. The
ORP and conductivity sensors had coefficients of determination greater than 0.95, indicating that
they were highly correlated with one another, but their slopes were approximately 11% and 9%
33
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Table 6-7. Inter-unit Reproducibility Evaluation
Parameter
Free chlorine
Turbidity
Temperature
Conductivity
pH
ORP
Slope
0.88
0.97
0.97
1.09
0.71
0.89
Intercept
0.10
0.028
0.31
-1.1
2.4
40
2
0.77
0.99
1.00
0.97
0.85
0.96
t-test p-value
0.59
0.76
0.41
0.00020
0.48
0.0093
Shading = significant difference between units as determined by a t-test.
from unity. For ORP, the slope was less than unity, indicating that the results for Unit 2 were
consistently lower than those for Unit 1; and for conductivity, the slope was greater than unity,
indicating that Unit 2 results were consistently higher. For both sensors, this evaluation was
confirmed by the t-test since the p-values for these two sensors were much less than 0.05
(shaded), indicating a significant difference in their results. This difference is driven by the small
amount of variability in the conductivity and ORP measurements; therefore, small differences in
the means were statistically significant. In addition to the inter-unit statistical evaluation, the
results for all four sensors were confirmed through a visual evaluation of the figures throughout
Chapter 6. For temperature and turbidity, the results from the two units are graphed nearly on top
of one another, while for ORP and conductivity, a small but consistent difference was evident.
With respect to Unit 2, Unit 1 was biased high for ORP and low for conductivity.
The free chlorine and pH sensors had lower coefficients of determination and slopes that deviated
from unity by at least 10%. This lower correlation was observed in the figures for the extended
deployment when Unit 2 drifted to lower pHs (and therefore lower chlorine results), while Unit 1
remained steady or drifted upward slightly. In addition, adjusting the chlorine sensor twice during
the verification test increased the variability in the pH and free chlorine results. Because of this,
the t-test indicated that the results from each of the free chlorine and pH sensors were statistically
the same, despite the observed differences.
6.6 Ease of Use and Data Acquisition
Throughout the duration of the verification test, the verification staff was not required to perform
any routine maintenance. However, on two occasions, ATI representatives adjusted the pH sensor
reading to match the reference sample measurement. The measurement of free chlorine is a
function of the pH measured by the pH sensor; therefore, the accuracy of the free chlorine
measurement was directly affected by this adjustment. Based on the performance of the free
chlorine and pH sensors, the pH sensor may have to be adjusted periodically to maintain the
accuracy of both measurements. This would require a means of measuring the pH of the water, as
well as a site visit, to make the adjustment. No other maintenance was necessary during the test.
ATI provided HOBO® data recorders for use during the verification test. Each sensor was plugged
into a HOBO® data recorder, and data were collected based upon preset recording frequency.
With a 30-second data collection frequency, the storage capacity of the HOBO® recorder was
approximately 3 days. Generally, data were downloaded every working morning by attaching a
34
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serial connector to an output on the HOBO® recorder. After affirming that the data (named for the
test period) had properly exported to a spreadsheet program, the data were deleted from the data
logger and the loggers were reinitialized. During the test period, two of the HOBO® recorders
experienced problems upon relaunch that necessitated their replacement. In those instances,
several days of data were not recorded while waiting for a replacement data logger.
35
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Chapter 7
Performance Summary
Evaluation Parameter
Stage 1 —
Accuracy
Stage 2—
Response to
Injected
Contaminants
Stage 3 —
Accuracy During
Extended
Deployment
Stage 3 —
Accuracy After
Extended
Deployment
Stage 3 —
Response to
Injected
Contaminants
Injection
Summary
Inter-unit
Reproducibility
(Unit 2 vs. Unit 1)
Ease of Use
and Data
Acquisition
Units 1 and 2, range
of %D (median)
Nicotine
Arsenic
trioxide
Aldicarb
Reference
Q45WQ
Reference
Q45WQ
Reference
Q45WQ
Units 1 and 2,
range of %D
(median)
Unit 1, %D
Unit 2, %D
E. coli
Aldicarb
Reference
Q45WQ
Reference
Q45WQ
Free
Chlorine
-4 1.5 to
54.3 (-15.7)
-
-
-
-
-
-
-33.7 to
29.7 (-7.3)
1.1
-1.1
-
-
-
-
Turbidity
-47.2 to -16.9
(-24.9)
(b)
+
(b)
+
(b)
+
-88.0 to
18.2 (-42.3)
-5.9
11.8
+
+
+
+
Tem-
perature
-5.5 to 1.3
(-1.4)
NC
NC
NC
NC
NC
NC
-4.9 to
1.5 (-1.4)
0.0
-0.9
NC
NC
NC
NC
Conductivity
-19.7 to
-2.6 (-12.7)
NC
NC
+
+
NC
NC
-19.4 to
-5.3 (-13.6)
-14.0
-7.9
+(0
NC
NC
NC
pH
-11.8 to
-0.9 (-5.0)
NC
NC
+
+
NC
NC
-8.3 to
1.5 (-3.5)
0.1
-2.2
-
-
-
(c)
ORP
(a)
-
-
-
-
-
-
(a)
(a)
(a)
-
-
-
-
For a reason that is not clear, aldicarb altered the pH, as measured by the reference method, during the
Stage 3 injections, but not during the Stage 2 injections.
Slope (intercept)
r2
p-value
0.88 (0.10)
0.77
0.59
0.97 (0.028)
0.99
0.76
0.97(0.31)
1.00
0.41
1.09 (-1.1)
0.97
0.00020
0.71 (2.4)
0.85
0.48
0.89 (40)
0.96
0.0093
The ORP and conductivity sensors on each unit generated results that were significantly different from
one another. Each unit's results were highly correlated with one another; but, because of the small
degree of variability in each sensor's results, they were determined to be significantly different.
Based on the performance of the free chlorine and pH sensors, the pH sensor may have to be adjusted
periodically to maintain the accuracy of both measurements. No other maintenance was necessary
during the test.
(a) ORP was not included in the accuracy evaluation because of the lack of an appropriate reference method.
(b) Relatively large uncertainty in the reference measurements made it difficult to determine a significant change.
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Chapter 8
References
1. Test/QA Plan for Verification of Multi-Parameter Water Monitors for Distribution Systems,
Battelle, Columbus, Ohio, August 2004.
2. Personal communication with John Hall, U.S. EPA, July 23, 2004.
3. U.S. EPA, EPAMethod 150.1, pH, inMethodsfor Chemical Analysis of Water and Wastes,
EPA/600/4-79/020, March 1983.
4. American Public Health Association, et al., SM 2510, Conductivity, in Standard Methods for
the Examination of Water and Wastewater. 19th Edition, Washington, D.C., 1997.
5. American Public Health Association, et al., SM 4500-G, Residual Chlorine, in Standard
Methods for the Examination of Water and Wastewater, 19th Edition, Washington, D.C., 1997.
6. American Public Health Association, et al., SM 2580-B, Electrochemical Potential, in
Standard Methods for the Examination of Water and Wastewater, 19th Edition, Washington,
D.C., 1997.
7. U.S. EPA, EPA Method 170.1, Temperature, in Methods for Chemical Analysis of Water and
Wastes, EPA/600/4-79/020, March 1983.
8. U.S. EPA, EPA Method 180.1, Turbidity, in Methods for Chemical Analysis of Water and
Wastes, EPA/600/4-79/020, March 1983.
9. Quality Management Plan (QMP)for the ETV Advanced Monitoring Systems Center,
Version 5.0, U.S. EPA Environmental Technology Verification Program, Battelle, Columbus,
Ohio, March 2004.
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