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2006 CORM Conference – 11 May 2006: Page 1
Optical Technology Division
Calibration and Characterization of UV Sensors for Water Disinfection
Authors: Thomas Larason and Yoshi Ohno
Optical Technology DivisionPhysics Laboratory
National Institute of Standards and TechnologyGaithersburg, MD 20899-8441, USA
2006 Council of Optical Radiation Measurements ConferenceGaithersburg, Maryland 9-11 May 2006
National Institute of Standards and Technology
2006 CORM Conference – 11 May 2006: Page 2
Optical Technology Division
• 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 WorkNote: 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.
Outline
2006 CORM Conference – 11 May 2006: Page 3
Optical Technology Division
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.
2006 CORM Conference – 11 May 2006: Page 4
Optical Technology Division
Increasing use of UV for Drinking Water DisinfectionMunicipalities like Vancouver, BC and New York, NY
are planning water treatment facilities that incorporate UV light in the water disinfection process.
http://www.gvrd.bc.ca/water/pdfs/SCFPOverview.pdf
Update: UV water disinfection is coming to Montgomery and Prince Georges counties in Maryland.
UV Reactor
From Greater Vancouver Regional District document: SCFPOverview.pdf
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
2006 CORM Conference – 11 May 2006: Page 5
Optical Technology Division
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
2006 CORM Conference – 11 May 2006: Page 6
Optical Technology Division
Example UV Sensors
2006 CORM Conference – 11 May 2006: Page 7
Optical Technology Division
Measurement Quantity: Microbicidal Irradiance
The physical quantity to be measured is the microbicidally weighted irradiance (microbicidal irradiance):
d)()(relmik,mik EsE [unit: W/m2]
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
200 220 240 260 280 300 320 340 360 380 400
Wavelength [nm]
Rel
ativ
e R
esp
onsi
vity
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Rel
ativ
e P
ower
UV Sensorsmik(λ)LPMMPM
s mik,rel(λ )
E(λ): spectral irradiance (e.g., W/m2/nm)
smik,rel(λ)
2006 CORM Conference – 11 May 2006: Page 8
Optical Technology Division
American Water Works Association Research Foundation (AwwaRF)
NIST is participating in AwwaRF Project 2977: Design and Performance Guidelines for UV Sensor Systemscollaborating 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
2006 CORM Conference – 11 May 2006: Page 9
Optical Technology Division
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.
2006 CORM Conference – 11 May 2006: Page 10
Optical Technology Division
.
DetectorCarousel
Light Tight Enclosure
MonitorDetector
Sources
Baffle
Alig
nmen
t L
aser
Wav
elen
gth
Dri
ve
Shutter
OrderSortingFilter
Beam Splitter
Double GratingMonochromator
UV WS
UV Spectral Comparator Facility (UV SCF)
UV Working Standards
Test UV Sensor
2006 CORM Conference – 11 May 2006: Page 11
Optical Technology Division
UV SCF Measurement Setup
Photo of UV SCF Measurement Setup
UV Sensor
UV SCF Working Standards
2006 CORM Conference – 11 May 2006: Page 12
Optical Technology Division
Spectral Irradiance and Radiance Calibrations using Uniform Sources (SIRCUS) Facility
Computer
Intensity Stabilizer
Spectrum Analyzer Wavemeter
Monitor Photodiode
Integrating Sphere
Exit Port
Lens
Galvo-driven Oscillating Mirroror Optical Fiber and Ultrasonic Bath
Transfer Standard
Translation Stages
Test Meter
Laser
Radiance and Irradiance ResponsivitySIRCUS usestunable lasersfrom 200 nmto 1800 nm
2006 CORM Conference – 11 May 2006: Page 13
Optical Technology Division
SIRCUS Facility Measurement Setup
Diffuser plate was used to increase the irradiance levels
Frosted glass diffuser plate
Irradiance Standard Detector – Trap and Precision Aperture
UV Sensors
2006 CORM Conference – 11 May 2006: Page 14
Optical Technology Division
Relative Spectral Responsivities of the UV Sensors
0.0
0.5
1.0
1.5
2.0
2.5
200 220 240 260 280 300 320 340 360 380 400
Wavelength [nm]
Nor
mal
ized
Res
pon
sivi
ty
Sensor #1
Sensor #4
Sensor #6
Sensor #7
Sensor #8
Sensor #10
smik,rel(λ) s mik,rel(λ )
2006 CORM Conference – 11 May 2006: Page 15
Optical Technology Division
Irradiance Responsivity Linearity (Limited Range) Sensor #1
0.90
0.92
0.94
0.96
0.98
1.00
1.02
0 5 10 15 20 25 30 35
Irradiance [W/m2]
Rel
ativ
e re
spon
sivi
ty
Sensor #9
0.90
0.92
0.94
0.96
0.98
1.00
1.02
0 5 10 15 20 25 30
Irradiance [W/m2]
Rel
ativ
e re
spon
sivi
ty
Sensor #10
0.90
0.92
0.94
0.96
0.98
1.00
1.02
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Irradiance [W/m2]
Rel
ativ
e re
spon
sivi
ty
Sensor #3
0.80
0.85
0.90
0.95
1.00
1.05
0 5 10 15 20
Irradiance [W/m2]
Rel
ativ
e re
spon
sivi
ty
Sensor #7
0.80
0.85
0.90
0.95
1.00
1.05
0 5 10 15 20 25
Irradiance [W/m2]
Rel
ativ
e re
spon
sivi
ty
Sensor #4
0.800
0.850
0.900
0.950
1.000
1.050
0 5 10 15 20
Irradiance [W/m2]
Rel
ativ
e re
spon
sivi
ty
2006 CORM Conference – 11 May 2006: Page 16
Optical Technology Division
Temperature Dependence Measurement Setup
Photo of variable temperature chamber used for UV sensor characterization
UV Sensor Position
Radiator Coils circulating water for temperature control
Test Chamber Entrance Port
Water Bath, set water temperatures, 10 °C to 35 °C
Twin-tube 35 W LPM lamp with intensity monitor
2006 CORM Conference – 11 May 2006: Page 17
Optical Technology Division
Temperature Dependence of the Irradiance Responsivity
0.98
1.00
1.02
0 5 10 15 20 25 30 35 40
Sensor Temperature [°C]
Rel
ativ
e Si
gnal
Sensor #1 Sensor #4 Sensor #6 Sensor #7 Sensor #8 Sensor #10
Error bars show typical expanded uncertainty (k =2)
2006 CORM Conference – 11 May 2006: Page 18
Optical Technology Division
Angular Dependence Measurement Setup
Set up for angular responsivity measurement (top view)
Cross-section of a twin tube LPM lamp
Aperture screen
inttensity monitor
Rotation stage
UV sensor
22 cm
3.5°Shutter
2006 CORM Conference – 11 May 2006: Page 19
Optical Technology Division
Angular Responsivities of the UV SensorsAngular Response of UV Sensors
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
-100 -80 -60 -40 -20 0 20 40 60 80 100
Incident Angle (deg)
Rel
ativ
e R
esp
onsi
vity
Sensor #1
Sensor #4
Sensor #6
Sensor #7
Sensor #8
Sensor #10
Cosine
2006 CORM Conference – 11 May 2006: Page 20
Optical Technology Division
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).
MPM lamp
Reference Detector
Sensor under test
Output current y
200 250 300 350 400
Wavelength (nm)
Responsivity for MPM lamp: [A/(W/m2)])MPM(
)MPM(mik
microb E
ys
Typical MPM Lamp Spectrum
LPM)(or mikEMPM)(mikE
(or LPM lamp)
2006 CORM Conference – 11 May 2006: Page 21
Optical Technology Division
• 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.
Future Work
2006 CORM Conference – 11 May 2006: Page 22
Optical Technology Division
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.
Acknowledgements