THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM
v>EPA
U.S. Environmental Protection Agency
ET/
Battelle
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ETV Joint Verification Statement
TECHNOLOGY TYPE: MULTI-PARAMETER WATER MONITORS FOR
DISTRIBUTION SYSTEMS
APPLICATION:
MONITORING DRINKING WATER QUALITY
TECHNOLOGY NAME: Model WQS
COMPANY: Rosemount Analytical
ADDRESS:
WEB SITE:
E-MAIL:
2400 Barranca Parkway
Irvine, CA 92606
www.emersonprocess.com
Richard.Baril @ EmersonProcess.com
PHONE: 949-757-8500
FAX: 949-863-9159
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 Rosemount Analytical Multi-Parameter/Optical Water Quality System (Model WQS) in continuously
measuring free chlorine, temperature, conductivity, pH, and oxidation-reduction potential (ORP) in drinking water.
This verification statement provides a summary of the test results.
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VERIFICATION TEST DESCRIPTION
The performance of the WQS unit 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
of the WQS unit. 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 WQS units was evaluated
during nine, 4-hour periods of stable water quality conditions by comparing each WQS 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 WQS 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 WQS 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 WQS performance to determine
whether this length of operation would negatively impact the results from the WQS. 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 WQS could be evaluated. Second, to evaluate the response of the WQS unit 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 WQS unit was provided by the vendor and does not represent verified
information.
The WQS unit measures pH, ORP, conductivity, temperature, and free chlorine in drinking water. The system
combines user-specified instruments and sensors to create a customized system for monitoring water quality. The
WQS unit does not need added reagents and uses minimum process flows of less than 183 milliliters per minute.
The WQS unit uses three basic electrochemical principles of operation: millivolt measurements for pH and ORP,
conductance/resistance measurements for conductivity, and amperometric/polarographic measurements for
chlorine residuals. The WQS unit continuously monitors each parameter to provide constant surveillance of water
quality events to ensure that acceptable water quality conditions are maintained. The WQS unit includes a sensor,
cables, and instruments to measure water quality parameters. The verified WQS unit was 26 inches high and
32 inches wide. The width varies by system from 26 inches to 50 inches wide. The data output from the system is
available as 4/20 mA analog, highway addressable remote transducer (HART®) or Foundation fieldbus® (HI), RS-
485, Ethernet, or Modbus RTU digital outputs. It uses 115/230-volt alternating current or 24-volt direct current.
During this verification test, a Fluke (Everette, Washington) data logger was configured to the WQS unit to record
the data every 30 seconds. The data logger was connected to a laptop computer that stored the data onto its hard
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drive as a delimited text file that was easily imported into a spreadsheet. The costs of the units as configured for
the verification test ranged from $12,000 to $15,000. In addition, calibration reagents cost approximately $200
annually.
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
Aldicarb
Reference
WQS
Reference
WQS
Reference
WQS
Units 1 and 2,
range of %D (median)
Unit 1, %D
Unit 2, %D
E. coli
Aldicarb
Reference
WQS
Reference
WQS
Free
Chlorine
-11.1 to 96.7
(14.5)
-
-
-
(b)
-
-
-36.2 to 68.3
(1.6)
-1.1
-2.2
-
-
-
(b)
Tem-
perature
-5.9 to 1.5
(-1.7)
NC
NC
NC
NC
NC
NC
-4.1 to 2.4
(-0.2)
0.6
0.2
NC
NC
NC
NC
Conductivity
2.9 to 5.3
(4.2)
NC
NC
+
+
NC
NC
3.4 to 6.7
(5.2)
5.1
5.3
+
NC
NC
NC
pH
-7.4 to -1.1
(-3.0)
NC
NC
+
+
NC
NC
-2.8 to 1.8
(-1.2)
-0.6
-0.9
-
-
-
NC
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
0.48 (0.45)
0.271
0.367
1.01 (-0.19)
0.999
0.882
1.00(0.26)
1.00
0.787
0.97 (0.25)
0.958
0.832
0.97 (-4.38)
0.950
0.01 l(c)
With the exception of ORP, the t-test indicated that the sensors on each unit were performing
similarly. For ORP, the linear correlation between the two units was very high, but the extremely
small variability in the signal caused the difference between the two units to be statistically
significant. Although the free chlorine sensors were not highly correlated with one another, the
large variability in their measurements prevented the t-test from determining a significant
difference between the units.
Based on the performance of the free chlorine sensors, calibration and membrane replacement
may have to occur periodically to maintain accurate measurements, especially those involving
response to injected contaminants. Also, the regular variability in free chlorine and pH
measurements may prevent observing small changes in those water quality parameters.
(a) Because a laboratory reference measurement equivalent to the on-line continuous measurement was not available, ORP was
not included in the accuracy evaluation.
(b) Results from duplicate injections did not agree.
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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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