A new dual-collimation batch reactor for determination of ultraviolet inactivation rate constants for microorganisms in aqueous suspensions

J Photochem Photobiol B. 2016 Sep;162:674-680. doi: 10.1016/j.jphotobiol.2016.07.028. Epub 2016 Jul 25.


We developed, characterized, and tested a new dual-collimation aqueous UV reactor to improve the accuracy and consistency of aqueous k-value determinations. This new system is unique because it collimates UV energy from a single lamp in two opposite directions. The design provides two distinct advantages over traditional single-collimation systems: 1) real-time UV dose (fluence) determination; and 2) simple actinometric determination of a reactor factor that relates measured irradiance levels to actual irradiance levels experienced by the microbial suspension. This reactor factor replaces three of the four typical correction factors required for single-collimation reactors. Using this dual-collimation reactor, Bacillus subtilis spores demonstrated inactivation following the classic multi-hit model with k=0.1471cm(2)/mJ (with 95% confidence bounds of 0.1426 to 0.1516).

Keywords: Bacillus subtilis; Collimated-beam reactor; Germicidal; Inactivation rate constant; Ultraviolet; k-Value.

MeSH terms

  • Bacillus subtilis / physiology*
  • Spores, Bacterial / radiation effects*
  • Ultraviolet Rays*
  • Water Purification / instrumentation
  • Water Purification / methods