ABSTRACT
Escherichia coli O157:H7 is a major cause of foodborne disease outbreaks throughout the world, while methicillin-resistant Staphylococcus aureus (MRSA) is responsible for many difficult-to-treat infections in humans. Ultraviolet (UV) irradiation is commonly used for disinfection in food processing, medical facilities, and water treatment to prevent the transmission of these pathogen. With increased use of UV disinfection technologies over the last few years because of COVID-19 and concerns about other communicable disease, it has become a concern that microbial species could develop tolerance to UV irradiation, especially when it is applied continuously. To elucidate the effect of continuous UV exposure at different wavelengths and power levels on the tolerance development of bacteria, Escherichia coli O157:H7 and MRSA)USA300 growths were investigated by continuously exposing inoculated agar plates to six different commercially available UV sources at wavelengths of 222 nm, 254 nm, 275 nm, and 405 nm. The agar plates in these experiments were partially covered by a thin acrylic sheet, which provided either complete protection from the UV to the cells directly under the sheet, no protection if significantly away from the sheet, or partial protection near the edges of the sheet due to shading or small amounts of UV reflection under the sheet at the edges. In these experiments, tolerant cells of E. coli and S. aureus were found from the 222 nm, the 405 nm, and one of the 254 nm sources. Upon examination of the power of each UV source, it was shown that the 275 nm and 254 nm sources that resulted in no tolerant cells had surface power densities [at 25 cm (10 in.)] that were more than 10-200 times greater than those that had tolerant cells. These results suggests that bacterial cells have a higher chance to develop UV tolerance under lower power UV sources (under the experimental conditions in our laboratory). Genome investigation of the tolerant colonies revealed that there are no significant differences between the cells that developed tolerance and the original organism, hinting at the need to explore the role of epigenetics mechanisms in the development of UV tolerance in these bacteria. © 2023 American Society of Civil Engineers.
ABSTRACT
In connection with the COVID-19 pandemic, there is an urgent need for disinfecting devices that can be used both indoors and in transport. Currently, the most common of these devices are ultraviolet (UV) germicidal lamps. However, they have significant disadvantages, such as short service life, presence of mercury, lack of flexible control, large dimensions, etc. The paper analyzes the sources of UV radiation to find an alternative to UV lamps. Although these elements currently have low efficiency and high cost, etc., it is proposed to use UVC LEDs as a UV source. Due to the COVID-19 pandemic and the general interest in the fight against viruses, as well as the ban on the use of mercury, investments have been attracted in the development of UVC LEDs, which will make them competitive in the future compared to germicidal lamps both in cost and efficiency. The paper presents a disinfection device developed on the basis of UVC LEDs. The principle of operation is described;the control system, the drawing, and the design of the UVC LED-based disinfection device are presented. Due to the described limitations of UVC LEDs, this design can be used for disinfection of small surface areas where frequent on/off switching is required and high power is not required.
ABSTRACT
In this study, a low-cost Ultraviolet disinfection system is proposed to be used inside ambulances for minimizing the cross-infection of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) during patient transfer. The disinfection system consists of a tower unit that contains the Ultraviolet type C (UVC) light fixture and a control box where the power unit is placed. The UVC tower unit is portable, lightweight, and can be easily placed anywhere inside an ambulance. Two ultraviolet (UV) lamps used in the tower part have 254 nm wavelength with a total power of 180 Watt. The disinfection system can provide a dose of 16.9mj/cm2 within 1.06 seconds and 26.83 seconds if the distance of the targeted surface inside the ambulance from UV sources are 0.3 meters and 1.5 meters respectively. We have chosen various distances from UV source to targeted surface inside an ambulance and calculated the required corresponding times to reach the required dose to inactivate all viral concentrations. The designed disinfection system not only reduces the spread of SARS-CoV-2 by the semi-autonomous way inside ambulances but also requires the least labor efforts which are crucial in the current Covid-19 pandemic. © 2021 IEEE.
ABSTRACT
In the last years, low pressure ozone UVC mercury germicidal lamps have been widely used to decontaminate air, surfaces, and water. This technology is mature, and it has been widely used during the pandemic as a measure against SARS-CoV-2, the coronavirus that causes COVID-19; because the exposure of this virus to the wavelength wave of 254 nm has been proven to be an effective way to eliminate it. However, the Minamata Convention in 2013 decided to limit mercury lamps by 2020; therefore, the development of new technology devices based on UVC-LEDs (short-wave ultraviolet, light-emitting diodes) are receiving a lot of attention. Today, this technology is commercially available from 265 to 300 nm peak wavelengths, and recently up to 254 nm. Notwithstanding, due to the characteristics of these LEDs, arrangements with a precisely dosed power supply are regularly required to provide effective decontamination. Thus, this article reports the design and implementation of a power electronic converter for an array of 254 nm UVC-LEDs, which can be used to decontaminate from SARS-CoV-2 in a safe way.