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Calibration and Characterization of UV Sensors for Water Disinfection

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Title: Calibration and Characterization of UV Sensors for Water Disinfection


1
Calibration and Characterization of UV Sensors
for Water Disinfection
2006 Council of Optical Radiation Measurements
Conference Gaithersburg, Maryland 9-11 May
2006 National Institute of Standards and
Technology
  • Authors Thomas Larason and Yoshi Ohno
  • Optical Technology Division
  • Physics Laboratory
  • National Institute of Standards and Technology
  • Gaithersburg, MD 20899-8441, USA

2
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.

3
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
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
5
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
Example UV Sensors
7
Measurement Quantity Microbicidal Irradiance
  • The physical quantity to be measured is the
    microbicidally weighted irradiance (microbicidal
    irradiance)

unit W/m2
E(?) spectral irradiance (e.g., W/m2/nm)
smik,rel(?)
8
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
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
UV Spectral Comparator Facility (UV SCF)
UV Working Standards
Test UV Sensor
11
UV SCF Measurement Setup
  • Photo of UV SCF Measurement Setup

UV SCF Working Standards
UV Sensor
12
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
Spectrum Analyzer
Wavemeter
Transfer Standard
Test Meter
Computer
Translation Stages
Exit Port
Lens
Integrating Sphere
Monitor Photodiode
Galvo-driven Oscillating Mirror or Optical Fiber
and Ultrasonic Bath
13
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
14
Relative Spectral Responsivities of the UV Sensors
15
Irradiance Responsivity Linearity (Limited Range)
16
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
Water Bath, set water temperatures, 10 C to 35 C
UV Sensor Position
17
Temperature Dependence of the Irradiance
Responsivity
18
Angular Dependence Measurement Setup
  • Set up for angular responsivity measurement (top
    view)

19
Angular Responsivities of the UV Sensors
20
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
(or LPM lamp)
Responsivity for MPM lamp A/(W/m2)
21
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.

22
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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