2006 CORM Conference – 11 May 2006: Page 1 Optical Technology Division Calibration and Characterization of UV Sensors for Water Disinfection Authors: Thomas

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



• 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



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.



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



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



Example UV Sensors



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)



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



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.



.

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



UV SCF Measurement Setup

Photo of UV SCF Measurement Setup

UV Sensor

UV SCF Working Standards



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



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



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 )



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



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



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)



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



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



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)



• 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



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

Documents

2006 CORM Conference – 11 May 2006: Page 1 Optical Technology Division Calibration and Characterization of UV Sensors for Water Disinfection Authors: Thomas