Understanding possible underlying mechanism in declining germicidal efficiency of UV-LED reactor

Hyunkyung Lee, Yongxun Jin, Seungkwan Hong

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


Since ultraviolet light emitting diodes (UV-LEDs) have emerged as an alternative light source for UV disinfection systems, enhancement of reactor performance is a demanding challenge to promote its practical application in water treatment process. This study explored the underlying mechanism of the inefficiency observed in flow-through mode UV disinfection tests to improve the light utilization of UV-LED applications. In particular, the disinfection performance of UV-LED reactors was evaluated using two different flow channel types, reservoir and pathway systems, in order to elucidate the impact of physical circumstances on germicidal efficiency as the light profile was adjusted. Overall, a significant reduction in germicidal efficiency was observed when exposure time was prolonged or a mixing chamber was integrated. Zeta analysis revealed that the repulsion rate between microorganisms decreased with UV fluence transfer, and that change might cause the shielding effect of UV delivery to target microorganisms. In line with the above findings, the reduction in efficiency intensified when opportunities for microbial collision increased. Thus, UV induced microbial aggregation was implicated as being a disinfection hindering factor, exerting its effect through uneven UV illumination. Ultimately, the results refuted the prevailing belief that UV has a cumulative effect. We found that the reservoir system achieved worse performance than the pathway system despite it providing 15 times higher UV fluence: the differences in germicidal efficiency were 1-log, 1.4-log and 1.7-log in the cases of P.aeruginosa, E.coli and S.aureus, respectively.

Original languageEnglish
Pages (from-to)136-142
Number of pages7
JournalJournal of Photochemistry and Photobiology B: Biology
Publication statusPublished - 2018 Aug

Bibliographical note

Funding Information:
This research was supported by a grant from the Technology Innovation Program (Technology development of an ultra-pure water process for semiconductor level industrial water and localization for four kinds of consumable material) funded by the Ministry of Trade, Industry and Energy , Republic of Korea ( 10052814 ).

Publisher Copyright:
© 2018 Elsevier B.V.


  • Disinfection
  • Flow-through reactor
  • Microbial aggregation
  • UV-LED
  • Ultraviolet

ASJC Scopus subject areas

  • Radiation
  • Radiological and Ultrasound Technology
  • Biophysics
  • Radiology Nuclear Medicine and imaging


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