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Pulsed and continuous light UV LED: microbial inactivation, electrical, and time efficiency.

Kari Sholtes1, Karl G Linden1

  • 1Department of Civil, Environmental and Architectural Engineering, University of Colorado Boulder, USA.

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PubMed
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Pulsing ultraviolet light emitting diodes (UV LEDs) do not significantly improve microbial inactivation compared to continuous operation. Optimal UV LED selection for disinfection systems requires considering microbial inactivation, electrical, and time efficiencies (E_NETO).

Keywords:
BacteriaBacteriophageDisinfectionDrinking waterUV LED wavelengths

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Area of Science:

  • Environmental Microbiology
  • Photochemistry
  • Biotechnology

Background:

  • Ultraviolet light emitting diodes (UV LEDs) are increasingly used for microbial inactivation across various applications.
  • Current UV LED efficiency metrics lack a time component, hindering optimal design choices.
  • Understanding UV LED performance under different operating conditions is crucial for effective disinfection.

Purpose of the Study:

  • To investigate the microbial inactivation efficacy of UV LEDs under continuous and pulsing conditions.
  • To evaluate the impact of different wavelengths and operating parameters on disinfection performance.
  • To introduce a comprehensive efficiency metric (E_NETO) for UV LED system design.

Main Methods:

  • Testing UV LED disinfection of planktonic microorganisms (E. coli, MS-2, P. aeruginosa).
  • Comparing continuous UV LED operation against various pulsing duty rates and frequencies.
  • Analyzing microbial inactivation, electrical efficiency, and time efficiency.

Main Results:

  • Pulsing UV LEDs did not yield statistically significant differences in disinfection performance compared to continuous operation.
  • UV LEDs emitting at wavelengths matching a microorganism's peak action spectrum are most effective on a fluence-basis.
  • A new metric, E_NETO, allows designers to compare normalized microbial inactivation, electrical, and time efficiencies.

Conclusions:

  • Pulsing operation does not enhance UV LED disinfection efficacy over continuous light.
  • Optimal UV LED wavelength selection balances microbial inactivation with electrical efficiency.
  • The E_NETO metric provides a holistic approach for selecting UV LEDs, improving system design, and potentially reducing costs.