Date of Award

Winter 2023

Project Type

Dissertation

Program or Major

Civil Engineering

Degree Name

Doctor of Philosophy

First Advisor

James Malley

Second Advisor

Paula Mouser

Third Advisor

Thomas Ballestero

Abstract

The COVID-19 pandemic highlighted the need for more robust surface disinfection technologies. Photoinactivation efficacy for microbial pathogens and many surrogates has been well studied for water disinfection. However, there is a limited body of knowledge from research on surface disinfection applications of these technologies. The onset of the global pandemic resulted in a dramatic increase in surface disinfection devices being marketed to consumers, yet regulations for such devices have not been developed. This doctoral research studies the inactivation efficacy of two wavelengths, UV254 and BL405. The objective of this doctoral dissertation was to expand the body of knowledge required to properly design and regulate UV and visible light surface disinfection devices allowing increased protection of public health.

This dissertation covers three chapters examining the effects of surface materials and properties on photoinactivation efficacy. Chapter 1 focuses on FFR (Filtering Facepiece Respirator) disinfection of MS-2 bacteriophage and E. coli. This research was catalyzed by the FFR shortage at the onset of the COVID-19 pandemic. Frontline medical professionals inquired about utilizing a commercially purchased UV254 device to safely disinfect FFRs for reuse. Our research revealed the challenges associated with line-of-sight disinfection technologies when applied to multi-layer, porous FFR materials. Additionally, this research was the first to report on the importance of using bacterial or viral surrogates rather than inert particles when quantifying FFR materials degradation due to UV254 exposure.

Chapter 3 expands upon the findings of Chapter 2, by studying UV254 disinfection efficacy of MS-2 bacteriophage on five materials with variable surface properties. Findings presented in Chapter 3 reveal novel correlations between viral recovery and surface properties such as contact angle, porosity, surface roughness, reflectivity, and zeta potential.Finally, Chapter 4 explores an alternative wavelength, BL405, that has gained significant interest within the healthcare industry. This wavelength is thought to have germicidal properties, without the harmful effects to skin and eyes, associated with UV254 exposure. At present, there are very few studies in the literature on viral inactivation with BL405. Additionally, the effects of dew point on BL405 inactivation have not been studied. Chapter 4 reveals that the viricidal effects of BL405 are greatly increased in high dew point environments. It is hypothesized that this results from an increase in the production of reactive oxygen species. BL405 experiments required long exposure times to achieve the desired dose since they are up to three orders of magnitude higher than the dose needed with UV254. Therefore, careful control experiments were vital to distinguish the germicidal effects of BL405 from viral degradation.

This research has contributed novel findings to the surface photoinactivation body of knowledge. This work provides critical insights into the effects of surface characteristics on UV254 and BL405 disinfection efficacy. Additionally, the work conducted with BL405 indicates that environmental conditions are highly influential to the disinfection efficacy of this wavelength. These findings expand the industries knowledge of the effects of surface characteristics and environmental conditions, which will ultimately lead to more effective designs and regulations for the utilization of surface photoinactivation devices to increase public health protection.

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