Experimental and Numerical Studies of a New Pulsed Upper-room Multi-wavelength UV-LED Disinfection System

Description

The transmission of airborne disease is a major global public health issue. An infected personcan transmit airborne pathogens to the general public, even before diagnosis. If the transmissionis rapid, it can eventually lead to an epidemic, as what occurred with severe acute respiratorysyndrome (SARS). Communicable disease control is therefore crucial to the prevention of suchillnesses.Several engineering strategies are currently implemented to reduce the risk of pathogen spread:increasing ventilation rates, using high efficiency filtration systems and adopting activedisinfection systems. Due to its high airflow handling capacity, upper-room ultravioletgermicidal irradiation (UR-UVGI) has been introduced to heating, ventilation and airconditioning markets as a viable alternative technology.Light-emitting diodes (LEDs) are now the illumination source of choice. They are durable, havehigh output efficiencies and are manufactured without hazardous materials. They can operate incontinuous or pulsed mode, and do not generate ozone. Very recently, UV-LEDs have becomecommercially available.Although the results of preliminary studies in stationary water samples showed synergisticeffects for different UV-LED wavebands, and that inactivation efficacies were increased underpulsed operation, there have not been any studies on airborne pathogens. The compact size ofLEDs also allows for “moving irradiation.” These are the three promising aspects that underliethis study, and may allow for significant enhancements in disinfection performance over currentUVGI systems.This project aims to carry out a systematic study that combines empirical, experimental andcomputational advances towards a novel UR-UVGI engineering system. It will study synergisticeffects utilizing LEDs of UV-A, UV-B and UV-C wavebands. Furthermore, enhancedantimicrobial effects of pulsed UV light will also be investigated. The system will be mounted ona rotating platform and the effect of moving irradiation on disinfection efficacy will beevaluated.The experiment will be conducted in a full-scale chamber. Different types of bacteria will beselected. The disinfection performance of the UV-LED and the conventional system will becompared methodologically by considering different pathogens’ emission scenarios. Atomicforce microscopy will be used to study the disinfection mechanisms by examining changes incellular structure after exposure to the UR-UVGI. A computational tool will be developed, andthe UV irradiation and microorganism continuity equations will be solved.The findings of this study are expected to contribute to the development of a safer, moreefficient, ozone emission free disinfection system, and to help policy-makers tackle global publichealth challenges.