Transcript Calibration and Characterization of UV Sensors for Water

2006 Council of Optical Radiation Measurements Conference
Gaithersburg, Maryland 9-11 May 2006
National Institute of Standards and Technology
Calibration and Characterization of UV
Sensors for Water Disinfection
Authors: Thomas Larason and Yoshi Ohno
Optical Technology Division
Physics Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899-8441, USA
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Outline
• Background
•
Using UV light to disinfect drinking water
• NIST Measurements
•
•
•
•
Relative spectral responsivity, 200 nm to 400 nm
Linearity of response
Temperature dependence
Angular responsivity
• Proposed Alternate Calibration Method
• Future Work
Note: This talk was presented at the 6th UVNet Workshop on Ultraviolet Radiation Measurements,
21 October 2005 in Davos, Switzerland and published in Metrologia 43 (2006) S151-S156.
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Background
Ultraviolet radiation (UV) effectively inactivates
common pathogens found in ground and surface
waters such as Cryptosporidium, Giardia, and most
bacterial pathogens (e.g., E. coli).
Water treatment facilities recently started using
ultraviolet radiation for disinfection of drinking
water, replacing standard chemical treatment.
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Increasing use of UV for Drinking Water Disinfection
Municipalities like Vancouver, BC and New York, NY
are planning water treatment facilities that incorporate
UV light in the water disinfection process.
Vancouver (2008 construction complete )
12 UV Reactors: 480 million gallons / day
Wash. DC Suburbs (2007 installation begins)
12 UV Reactors: 300 million gallons / day
New York City (2011 operational)
56 UV Reactors: 2.4 billion gallons / day
UV Reactor
From Greater Vancouver
Regional District document:
SCFPOverview.pdf
Update: UV water disinfection is
coming to Montgomery and Prince
Georges counties in Maryland.
http://www.gvrd.bc.ca/water/pdfs/SCFPOverview.pdf
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Example UV Reactor Vessel
There are many different designs for the reactor vessels
and lamp placement inside the vessels. UV Sensor
design and configuration varies with manufacturer.
Illustrations courtesy of Severn Trent
Services from US EPA document
815-D-03-007 June 2003 Draft
http://www.epa.gov/safewater/lt2/guides.html
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Example UV Sensors
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Measurement Quantity: Microbicidal Irradiance
The physical quantity to be measured is the microbicidally
weighted irradiance (microbicidal irradiance):
Emik   smik,rel ( )E ( )d
[unit: W/m2]

E(λ): spectral irradiance (e.g., W/m2/nm)
Relative Responsivity
1.4
smik,rel(λ)
1.2
1.2
UV Sensor
ssmik(λ)
mik,rel(λ )
LPM
MPM
1.0
0.8
1.0
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
0.0
200
220
240
260
280
300
320
340
Wavelength [nm]
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360
380
400
Relative Power
1.6
American Water Works Association Research Foundation
(AwwaRF)
NIST is participating in AwwaRF Project 2977:
Design and Performance Guidelines for UV Sensor Systems
collaborating with
• Carollo Engineers, Boise, ID
• Camp Dresser and McKee, Denver, CO
• Institute of Medical Physics and Biostatistics at the University
of Veterinary Medicine, Vienna, Austria
In this project, NIST is responsible for
Task 3. Methods Development and Lab Studies
3.1 Methods Development
3.2 UV Sensor Testing
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NIST Measurements of the UV Sensors
We have tested several UV sensors (reference and duty)
used to monitor UV reaction chambers in water
treatment facilities for several characteristics:
•
Absolute irradiance calibration at 254 nm
• Relative spectral responsivity, 200 nm to 400 nm
• Linearity of response
• Temperature dependence
• Angular responsivity
Some problems have been identified on the absolute
calibration of these UV sensors.
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Light Tight Enclosure
Detector
UV WS
Carousel
ning
n
a
c
S
iage
Carr
Baffle
Beam Splitter
Test UV Sensor
Monitor
Detector
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Order
Sorting
Filter
Wavelength
Drive
UV Working Standards
Double Grating
Monochromator
Shutter
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Alignment Laser
UV Spectral Comparator Facility (UV SCF)
Sources
UV SCF Measurement Setup
Photo of UV SCF Measurement Setup
UV SCF
Working
Standards
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UV Sensor
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Spectral Irradiance and Radiance Calibrations using
Uniform Sources (SIRCUS) Facility
Radiance and Irradiance Responsivity
SIRCUS uses
tunable lasers
from 200 nm
to 1800 nm
Intensity
Stabilizer
Laser
Test
Meter
Spectrum
Analyzer
Transfer
Standard
Wavemeter
Computer
Translation
Stages
Exit
Port
Integrating
Sphere
Lens
Monitor
Photodiode
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Galvo-driven Oscillating Mirror
or Optical Fiber and Ultrasonic Bath
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SIRCUS Facility Measurement Setup
Diffuser plate was used to increase the irradiance levels
Irradiance Standard
Detector – Trap and
Precision Aperture
UV Sensors
Frosted glass
diffuser plate
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Relative Spectral Responsivities of the UV Sensors
2.5
Normalized Responsivity
Sensor #1
Sensor #4
2.0
Sensor #6
Sensor #7
Sensor #8
1.5
Sensor #10
smik,rel(λ)
s mik,rel(λ )
1.0
0.5
0.0
200
220
240
260
280
300
320
Wavelength [nm]
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340
360
380
400
Irradiance Responsivity Linearity (Limited Range)
Sensor #3
Sensor #1
1.02
1.05
Relative responsivity
Relative responsivity
1.00
0.98
0.96
0.94
0.92
1.00
0.95
0.90
0.85
0.80
0.90
0
5
10
15
20
25
30
0
35
5
10
Irradiance [W/m ]
1.000
1.00
0.950
0.900
0.850
0.800
5
20
Sensor #7
1.05
Relative responsivity
Relative responsivity
Sensor #4
1.050
0
15
Irradiance [W/m2]
2
10
15
0.95
0.90
0.85
0.80
20
0
5
10
15
20
25
2
Irradiance [W/m ]
Irradiance [W/m2]
Sensor #10
1.02
1.00
1.00
Relative responsivity
Relative responsivity
Sensor #9
1.02
0.98
0.96
0.94
0.92
0.98
0.96
0.94
0.92
0.90
0.90
0
5
10
15
20
25
30
0.0
2
1.0
1.5
2.0
2
Irradiance [W/m ]
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0.5
Irradiance [W/m ]
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2.5
3.0
Temperature Dependence Measurement Setup
Photo of variable temperature chamber used for UV
sensor characterization
Test Chamber
Entrance Port
Radiator Coils
circulating
water for
temperature
control
Twin-tube
35 W LPM
lamp with
intensity
monitor
UV Sensor
Position
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Water Bath, set
water
temperatures,
10 °C to 35 °C
Temperature Dependence of the Irradiance Responsivity
Temperature Dependance of UV Sensors
1.02
Relative Signal
Error bars show typical
expanded uncertainty (k =2)
1.00
0.98
0
5
10
15
20
25
30
35
Sensor Temperature [°C]
Sensor #1
Sensor #4
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Sensor #6
Sensor #7
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Sensor #8
Sensor #10
40
Angular Dependence Measurement Setup
Set up for angular responsivity measurement (top view)
Cross-section of
a twin tube LPM
lamp
Aperture screen
3.5°
inttensity
monitor
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Shutter
22 cm
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Rotation stage
UV sensor
Angular Responsivities
ofResponse
the UV
Sensors
Angular
of UV
Sensors
1.4
Sensor #1
Sensor #4
1.2
Sensor #6
Sensor #7
Sensor #8
Sensor #10
Relative Responsivity
1.0
0.8
Cosine
0.6
0.4
0.2
0.0
-0.2
-100
-80
-60
-40
-20
0
20
Incident Angle (deg)
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40
60
80
100
Proposed Calibration Method for Sensors used with
MPM Lamp Systems
Calibrate the sensors used for MPM lamp systems, against
irradiance by a MPM lamp (strict substitution).
Typical MPM Lamp Spectrum
Emik (MPM)
or Emik (LPM)
200
250
300
350
400
Wavelength (nm)
(or LPM lamp)
y
Responsivity for MPM lamp: smicrob (MPM) 
[A/(W/m2)]
Emik (MPM)
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Future Work
• NIST will measure the absolute spectral responsivity
of the 10 test sensors after UV exposure testing by the
Institute of Medical Physics and Biostatistics at the
University of Veterinary Medicine.
• NIST has a plan to develop a new facility and
calibration service to establish traceability for the UV
sensors used by the water disinfection community.
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Acknowledgements
This work is part of AwwaRF-funded Project 2977. We thank
AwwaRF for their support and the technical discussions with
the project advisory committee members.
We thank the project members for their valuable technical
discussions and providing data:
• Harold Wright of Carollo Engineers,
• Christopher Schulz of Camp Dresser and McKee,
• Alexander Cabaj of the Institute of Medical Physics and
Biostatistics at the University of Veterinary Medicine
We also thank the vendors of the UV sensors and water
disinfection facilities who provided the project with the sample
UV sensors.
And lastly, our NIST colleagues, Keith Lykke, Steve Brown, and
Yuqin Zong for their assistance in taking data.
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