Efficacy of single pass UVC air treatment for the inactivation of coronavirus, MS2 coliphage and Staphylococcus aureus bioaerosols

Publication history: Accepted - 20 April 2022; Published online - 26 April 2022There is strong evidence that SARS-CoV-2 is spread predominantly by airborne transmission, with high viral loads released into the air as respiratory droplets and aerosols from the infected subject. The spread and persistence of SARS-CoV-2 in diverse indoor environments reinforces the urgent need to supplement distancing and PPE based approaches with effective engineering measures for microbial decontamination – thereby addressing the significant risk posed by aerosols. We hypothesized that a portable, single-pass UVC air treatment device (air flow 1254 L/min) could effectively inactivate bioaerosols containing bacterial and viral indicator organisms, and coronavirus without reliance on filtration technology, at reasonable scale. Robust experiments demonstrated UVC dose dependent inactivation of Staphylococcus aureus (UV rate constant (k) = 0.098 m2/J) and bacteriophage MS2, with up to 6-log MS2 reduction achieved in a single pass through the system (k = 0.119 m2/J). The inclusion of a PTFE diffuse reflector increased the effective UVC dose by up to 34% in comparison to a standard Al foil reflector (with identical lamp output), resulting in significant additional pathogen inactivation (1-log S. aureus and MS2, p < 0.001). Complete inactivation of bovine coronavirus bioaerosols was demonstrated through tissue culture infectivity (2.4-log reduction) and RT-qPCR analysis – confirming single pass UVC treatment to effectively deactivate coronavirus to the limit of detection of the culture-based method. Scenario-based modelling was used to investigate the reduction in risk of airborne person-to-person transmission based upon a single infected subject within the small room. Use of the system providing 5 air changes per hour was shown to significantly reduce airborne viral load and maintain low numbers of RNA copies when the infected subject remained in the room, reducing the risk of airborne pathogen transmission to other room users. We conclude that the application of single-pass UVC systems (without reliance on HEPA filtration) could play a critical role in reducing the risk of airborne pathogen transfer, including SARS-CoV2, in locations where adequate fresh air ventilation cannot be implemented.This research was partly funded through the Invest Northern Ireland Innovation Voucher Programme (IV130218200 and IV130232906). We are grateful to the Global Challenges Research Fund (GCRF) UK Research and Innovation (SAFEWATER; EPSRC Grant Reference EP/P032427/1) for supporting Mr Arsalan Afkhami, Dr William J Snelling and Dr Jeremy W.J. Hamilton. Research at AFBI is funded by US-Ireland Research and Development Partnership in Agriculture grants BRDC-Seq and BRDC-URTMVP. We wish to thank Jonathan McMaw at AFBI for acquisition of images

Chapter Green Nanotechnology: Development of Nanomaterials for Environmental and Energy Applications

This book chapter discusses the syntheses of various nanomaterials, for green nanotechnology applications in detail. Special attention is given to the development of emerging areas, such as environmental as well as energy materials. Various approaches for preparing nanostructured photocatalysts, such as titanium dioxide, zinc oxide, iron oxide, and metal sulfides, different conventional methods and novel methods, including sol-gel methods, hydrothermal methods, microwave-assisted methods and sonochemical methods are introduced. The use of nanomaterials as photocatalysts, supporting materials for solar cells, and disinfectants is reported for environmental remediation and energy applications. Advanced applications of nanomaterials for water detoxification, air purification, and the inactivation of pathogenic microorganisms in water as well as dye-sensitized solar cells is also discussed. The enhancement of selectivity of photocatalysis, especially TiO2 systems, for the destruction of target contaminants in water is comprehensively presented. Finally, the role of reactive oxygen species (ROS), such as hydroxyl radical (•OH), superoxide anion radical (O2•-), singlet oxygen (1O2) and hydrogen peroxide (H2O2), in semiconductor photocatalysis is introduced and various experimental techniques to detect ROS are also discussed

A Review on the Visible Light Active Titanium Dioxide Photocatalysts for Environmental Applications

Development of visible light active (VLA) titania photocatalysts Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO 2) semiconductor mate-rials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applica-tions. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO2 photocatalytic materials. In this review, a background on TiO2 struc-ture, properties and electronic properties in photocatalysis is presented. The development of different strategies to modify TiO2 for the utilization of visible light, including non metal and/or metal doping, dye sensitization and coupling semiconductors are discussed. Emphasis is given to the origin of visible light absorption and the reactive oxygen species generated, deduced by physicochemical and photo-electrochemical methods. Various applications of VLA TiO2, in terms of environmental remediation and in particular water treatment, disinfection and air purification, are illustrated. Comprehensive studies on the photocatalytic degradation of contaminants of emerging concern, including endocrine disrupting compounds, pharmaceuticals, pesticides, cyanotoxins and volatile organic compounds, with VLA TiO2 are discussed and compared to conventional UV-activated TiO2 nanomaterials. Recent advances in bac-terial disinfection using VLA TiO2 are also reviewed. Issues concerning test protocols for real visible light activity and photocatalytic efficiencies with different light sources have been highlighted

Efficacy of single pass UVC air treatment for the inactivation of coronavirus, MS2 coliphage and Staphylococcus aureus bioaerosols

Publication history: Accepted - 20 April 2022; Published online - 26 April 2022There is strong evidence that SARS-CoV-2 is spread predominantly by airborne transmission, with high viral loads released into the air as respiratory droplets and aerosols from the infected subject. The spread and persistence of SARS-CoV-2 in diverse indoor environments reinforces the urgent need to supplement distancing and PPE based approaches with effective engineering measures for microbial decontamination – thereby addressing the significant risk posed by aerosols. We hypothesized that a portable, single-pass UVC air treatment device (air flow 1254 L/min) could effectively inactivate bioaerosols containing bacterial and viral indicator organisms, and coronavirus without reliance on filtration technology, at reasonable scale. Robust experiments demonstrated UVC dose dependent inactivation of Staphylococcus aureus (UV rate constant (k) = 0.098 m2/J) and bacteriophage MS2, with up to 6-log MS2 reduction achieved in a single pass through the system (k = 0.119 m2/J). The inclusion of a PTFE diffuse reflector increased the effective UVC dose by up to 34% in comparison to a standard Al foil reflector (with identical lamp output), resulting in significant additional pathogen inactivation (1-log S. aureus and MS2, p < 0.001). Complete inactivation of bovine coronavirus bioaerosols was demonstrated through tissue culture infectivity (2.4-log reduction) and RT-qPCR analysis – confirming single pass UVC treatment to effectively deactivate coronavirus to the limit of detection of the culture-based method. Scenario-based modelling was used to investigate the reduction in risk of airborne person-to-person transmission based upon a single infected subject within the small room. Use of the system providing 5 air changes per hour was shown to significantly reduce airborne viral load and maintain low numbers of RNA copies when the infected subject remained in the room, reducing the risk of airborne pathogen transmission to other room users. We conclude that the application of single-pass UVC systems (without reliance on HEPA filtration) could play a critical role in reducing the risk of airborne pathogen transfer, including SARS-CoV2, in locations where adequate fresh air ventilation cannot be implemented.This research was partly funded through the Invest Northern Ireland Innovation Voucher Programme (IV130218200 and IV130232906). We are grateful to the Global Challenges Research Fund (GCRF) UK Research and Innovation (SAFEWATER; EPSRC Grant Reference EP/P032427/1) for supporting Mr Arsalan Afkhami, Dr William J Snelling and Dr Jeremy W.J. Hamilton. Research at AFBI is funded by US-Ireland Research and Development Partnership in Agriculture grants BRDC-Seq and BRDC-URTMVP. We wish to thank Jonathan McMaw at AFBI for acquisition of images

Comparison of Photocatalytic Activities of Commercial Titanium Dioxide Powders Immobilised on Glass Substrates

Semiconductor photocatalysis is an advanced oxidation technology reported to be effective for the degradation of a wide range of organic pollutants found in water. Titanium dioxide is the most suitable photocatalyst for water treatment as it is insoluble under normal pH conditions, is photoactive, photostable, readily available and inexpensive. In this work Millennium Chemicals PC500, PC105, PC100, PC50, PC10 and Evonik Degussa P25 powders were immobilised onto borosilicate glass, via dip-coating and spray coating, producing thick films ranging from 0.2 to 1.4 mg catalyst per square cm of glass substrate. The photocatalytic activity of the immobilised films was compared under back-face UVA irradiation in a stirred-tank reactor using formic acid and phenol as model pollutants. Based upon the rate constant derived from the removal of the parent compound, and using the optimum catalyst loading determined under the experimental conditions employed, the order of photocatalytic activity for the degradation of formic acid was found to be P25 > PC100 > PC50 > PC105 ≥ PC500 > PC10, while for phenol degradation the order was P25 > PC50 > PC105 > PC100 ≥ PC500 > PC10