1. 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 Division Physics Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899-8441, USA 2006 Council of Optical Radiation Measurements Conference Gaithersburg, Maryland 9-11 May 2006 National Institute of Standards and Technology

2. 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 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. Outline

3. 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.

4. 2006 CORM Conference – 11 May 2006: Page 4 Optical Technology Division 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. 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

5. 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

6. 2006 CORM Conference – 11 May 2006: Page 6 Optical Technology Division Example UV Sensors

7. 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): [unit: W/m 2 ] E(λ): spectral irradiance (e.g., W/m 2 /nm) s mik,rel (λ)

8. 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 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

9. 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.

10. 2006 CORM Conference – 11 May 2006: Page 10 Optical Technology Division UV Spectral Comparator Facility (UV SCF) UV Working Standards Test UV Sensor

11. 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

12. 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 Mirror or Optical Fiber and Ultrasonic Bath Transfer Standard Translation Stages Test Meter Laser Radiance and Irradiance Responsivity SIRCUS uses tunable lasers from 200 nm to 1800 nm

13. 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

14. 2006 CORM Conference – 11 May 2006: Page 14 Optical Technology Division Relative Spectral Responsivities of the UV Sensors

15. 2006 CORM Conference – 11 May 2006: Page 15 Optical Technology Division Irradiance Responsivity Linearity (Limited Range)

16. 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

17. 2006 CORM Conference – 11 May 2006: Page 17 Optical Technology Division Temperature Dependence of the Irradiance Responsivity

18. 2006 CORM Conference – 11 May 2006: Page 18 Optical Technology Division Angular Dependence Measurement Setup Set up for angular responsivity measurement (top view)

19. 2006 CORM Conference – 11 May 2006: Page 19 Optical Technology Division Angular Responsivities of the UV Sensors

20. 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). Responsivity for MPM lamp:[A/(W/m 2 )] Typical MPM Lamp Spectrum (or LPM lamp)

21. 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

22. 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