UV Disinfection Research Articles

Ultraviolet Germicidal Irradiation Development Method for Transportation Disinfection Modelling

How do you continuously sanitise a coach/bus? Travelling on a coach during the COVID 19 pandemic was risky, and still is in some regions. There are many means of viral transfer: fomites, which is via contact after touching an infected surface; through direct droplet ballistics after a cough, and finally through aerosolization of the sputum into the air. Clean hands and masks reduce the former two. Mitigating viral load aerosol accumulation within the bus is of personal, commercial and societal interest. Done correctly, the passengers are safer; the transport organisation maintains hygienic business conditions and the society sees the viral spread reduction. Ultraviolet Germicidal Irradiation (UVGI) has been in use in operating theatres and water plants for over 100 years to reduce viral and bacterial load in the air and water. Valeo’s Thermal Commercial Vehicles (TCV) product group proposed, developed and now manufactures the most powerful coach/ bus UV Purifier module available. If the module is located within direct reach of the main air conditioning inlet, disinfected air is then delivered and entrained into the vehicle HVAC air delivery system. There it is cleanly distributed to the passengers and driver. During development two linked problems emerged:1. Where do you put the module(s) in retrofit?2. How do you keep the UV-C levels sufficiently high enough to kill the SARS Cov-2 virus but then low enough for continuous driver and passenger daily exposure?Computational Fluid Dynamics (CFD) provides the insight necessary to solve them. However, although high and low UV-C limits can be defined for the latter limit problem, devising a suitably representative model presented a novel challenge to Valeo TCV. This paper deals with the introduction of the radiation and viral field modelling into Valeo’s CFD toolset. Reformulating the InfraRed radiation model into essentially monochromatic UV-C band radiation, and with thoughtful design allowed us to develop a very high intensity virus killer that was also perfectly safe in the vehicle cabin. The modules are sold worldwide. Most importantly we use them daily on our team member transportation coaches to keep our employees safe to and from work at our production facilities.

Effects of Distance, Temperature, and Relative Humidity on the Irradiance of Ultraviolet‐C Germicidal Lamp: A Quantitative Study

Ultraviolet germicidal irradiation (UVGI) as an engineering control against pathogenic microbes necessitates a clear understanding of operational parameters and environmental effects on inactivation rates. Here, we investigated the variation laws of ultraviolet‐C (UV‐C) irradiance under the influence of distance, ambient conditions of temperature, and relative humidity (RH) in a dark chamber using 30‐W low‐pressure mercury lamps, and all data were analyzed with curve fitting methods. UV‐C irradiances in each plane were measured as the distance adjusting between 0.5 and 1.2 m, and a threshold of 70 μW/cm2 was utilized to calculate the effective irradiation area. For the temperature and RH, UV‐C irradiances were measured at 1 m perpendicular from the lamp axis at the lamp midpoint, with the ambient temperature increasing from 15.5°C to 40°C and RH adjusting from 10% to 97%. Results showed that the UV‐C irradiance and effective irradiation area exhibited a notable decrease as the distance increased, both corresponded to polynomial 2nd order fits. The UV‐C lamps operate at maximum efficiency at 20°C. Temperature above or below the optimum value will decrease UV output, especially when the ambient temperature exceeds 38°C and the irradiance decreases by 16% compared to the observed maximum. However, the impact of RH on radiant power is negligible with the UV‐C irradiance maintaining an overall steady state (84–91 μW/cm2) in the 10%–97% RH range. The use of the measurement and modeling techniques demonstrated in this study may help understand various ambient conditions that influence the irradiance of UV‐C and improve reliability and working performance of UVGI systems through better design.

UVC-Mirror for effective pathogens inactivation in air ducts

Improving the air quality of indoor environments (IAQ) is of utmost importance to safeguard public health as people spend about 80–90% of their time indoor. Efficient Ultraviolet germicidal irradiation (UVGI) system represents a strategic and sustainable solution to protect from recurrent and new airborne pathogens. Here, we present a new approach to design highly efficient UVGI systems, which can be installed in existing Air Treatment Units (ATU) plants with minimal effort. The increased efficiency relies on the concept of an optical cavity, thanks to its shape and source position. The internal volume consists of a highly reflective cavity illuminated with UV-C lamps. Optical simulations permitted the variation of the parameters to maximize the internal irradiance and, thus, the performance. The sanitation efficacy of the system was assessed on a full-scale pilot system. Tests were carried out under normal operating conditions against various microorganisms showed an inactivation rate of > 99%. The benefits of such systems are triple and encompass economic, environmental, and societal aspects. Since the system requires little energy to operate, its application for air disinfection may yield significant energy savings and ensure a balance between energy sustainability and good IAQ.

Feasibility study of UV intensity monitoring in water disinfection systems using reverse-biased LED photometers

Common ultraviolet (UV) photodiodes or detectors for measuring the intensity of UV-light-emitting diodes (LEDs) in UV disinfection systems are costly.

Contaminants of emerging concern reduction and microbial community characterization across a three-barrier advanced water treatment system

This research investigated the removal of contaminants of emerging concern (CECs) and characterized the microbial community across an advanced water treatment (AWT) train consisting of Coagulation/Flocculation/Clarification/Granular Media Filtration (CFCGMF), Ozone-Biological Activated Carbon Filtration (O3/BAC), Granular Activated Carbon filtration, Ultraviolet Disinfection, and Cartridge Filtration (GAC/UV/CF). The AWT train successfully met the goals of CECs and bulk organics removal. The microbial community at each treatment step of the AWT train was characterized using 16S rRNA sequencing on the Illumina MiSeq platform generated from DNA extracted from liquid and solid (treatment media) samples taken along the treatment train. Differences in the microbial community structure were observed. The dominant operational taxonomic units (OTU) decreased along the treatment train, but the treatment steps did impact the microbial community composition downstream of each unit process. These results provide insights into microbial ecology in advanced water treatment systems, which are influenced and shaped by each treatment step, the microbial community interactions, and their potential metabolic contribution to CECs degradation.

Comparative effectiveness of sequential and synergistic (VUV/)UV and chlorine disinfection on DBPs and humic acid reduction

The widespread use of chlorine during disinfection has led to the problems of disinfection by-products (DBPs). Recently, the combination of ultraviolet (UV, 254 nm) and vacuum ultraviolet (VUV, 185 nm) with chlorine has been considered a promising strategy to mitigate the formation of DBPs. This study systematically evaluated the efficacy of six different disinfection methods in abating humic acid (HA), a common precursor of DBPs (UV-Chlorine, VUV/UV-Chlorine, Chlorine-UV, Chlorine-VUV/UV, UV/Chlorine, and VUV/UV/Chlorine). Under 40 mJ/cm2 UV fluence and 3 mg/L chlorine dose, the synergistic processes yielded DBP levels below 20 μg/L, whereas sequential disinfection resulted in DBP levels exceeding 100 μg/L. Additionally, there was no significant difference in the formation of DBPs between the two methods of chlorination followed by irradiation. However, for irradiation followed by chlorination, the addition of VUV led to an increase of 50 μg/L in trihalomethanes (THMs). As the irradiation time increased, the inclusion of VUV demonstrated enhanced control of DBP levels in the sequential disinfection process. Moreover, compared to UV/Chlorine, at 13 mg/L chlorine dose in VUV/UV/Chlorine process, the inclusion of VUV expedited the appearance of peak DBPs by two minutes and reduced the peak value by 25.6 %, but the DBP yield was 12.9 times higher than that at a chlorine dose of 3 mg/L. This study, comparing six combination disinfection methods, will provide deeper insights into precursor abatement and DBP control during drinking water disinfection.

Highly efficient reduction of bromate by vacuum UV/sulfite system

Bromate (BrO3-), a worldwide regulated by-product after ozone disinfection, is often detected in bromide-containing water, and has a strict limit of 10 μg L−1 in potable water. BrO3- degradation by advanced reduction processes (ARPs) has gained much attention because of efficient removal and easy integration with ultraviolet disinfection (UV at 254 nm). In the vacuum UV (VUV, 185/254 nm)/sulfite system, the elimination kinetics of BrO3− increased by 9-fold and 15-fold comparing with VUV alone and UV/sulfite system. This study further demonstrated the hydrated electron (eaq-) works as the dominant species in BrO3- degradation in alkaline solution, while in the acidic solution the H• became a secondary reactive species besides eaq−. Hence, the influences of pH, sulfite concentration, dissolved gas and water matrix on effectiveness of degradation kinetics of BrO3- was explored in details. With increasing pH, the proportion of SO32− species increased and even became the major ones, which also correlated well with the kobs (min−1) of BrO3− degradation. The stability of eaq− also climbs with increasing pH, while that of H• drops significantly. Higher sulfite dosage favored a more rapid degradation of BrO3−. The presence of dissolved oxygen inhibited BrO3- removal due to the scavenging effect of O2 toward eaq− and transformed VUV/sulfite-based ARP to an advanced oxidation process (AOP), which was ineffective for BrO3- removal. BrO3- removal was inhibited to varying degrees after anions (e.g., bicarbonate (HCO3−), chloride (Cl−), nitrate (NO3−)) and humic acid (HA) being added.

Technology Selection for Wastewater Treatment in the Maldives

In the Maldives, the discharge of untreated wastewater into the sea poses a significant threat to public health and the marine environment. This study proposes technically feasible, sustainable, and economical wastewater treatment technologies appropriate for small islands in the Maldives. Out of the 187 residential islands in the Maldives, three islands (HA. Dhidhdhoo, HA. Hoarafushi, and HA. Ihavandhoo) were selected as study areas. This study characterized the wastewater from these islands using physiochemical and microbiological water quality assessment parameters. The Water and Wastewater Treatment Technologies Appropriate for Reuse (WAWTTAR), an open-source software developed by the Humbolt State University in 1993, was used to simulate the performance of different wastewater treatment processes to treat the characterized wastewater. The feasible alternatives identified from these simulations were analyzed using a Multi-Criteria Analysis (MCA), considering various indicators that influence the decision-making process. The wastewater quality assessment revealed that the wastewater generated in the three islands produced low concentrations of chemical and biological oxygen demand (COD and BOD), with concentrations ranging from 267 – 309 mg/L and 128 – 219 mg/L, respectively. Nitrate and phosphate concentrations were also low (5.7 – 18.0 mg/L and 2.8 – 14.9 mg/L, respectively), where these concentrations in Dhidhdhoo and Hoarafushi were already within the maximum allowable limits of 15 mg/L and 10 mg/L, respectively, for discharge into the deep sea. Based on the findings, secondary treatment technologies such as membrane bioreactors (MBR) and sequencing batch reactors (SBR) with Ultraviolet (UV) disinfection were found to be the most feasible options for treating the wastewater. These results were further checked for robustness using a sensitivity analysis. This study demonstrates that the proposed methodology is suitable for technology selection and can provide valuable information for policymakers and stakeholders in the country and serve as a basis for future studies.

Inactivation of pathogenic microorganisms in water by electron beam excitation multi-wavelength ultraviolet irradiation: Efficiency, influence factors and mechanism

Due to the limitations of traditional ultraviolet (UV) in microbial inactivation in water, it is necessary to explore a more suitable and efficient UV disinfection method. In this study, an electron beam excitation multi-wavelength ultraviolet (EBE-MW-UV) system was established and aims to analyze its differential microbial inactivation capabilities in comparison to single-wavelength UV-LEDs in waterborne applications. Furthermore, the inactivation mechanisms of this system on microorganisms were explored. The results showed that EBE-MW-UV had significantly higher inactivation effects on the Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Candida albicans in water compared to UV-LEDs (p＜0.05), and the inactivation effect of EBE-MW-UV on Escherichia coli and Pseudomonas aeruginosa at the same UV dose was 3.8 and 1.9 log higher than that of UV-LEDs, respectively, EBE-MW-UV exhibited better inactivation effects on Gram-negative bacteria. Further research found that, under the majority of irradiation doses, neither EBE-MW-UV nor UV-LEDs were significantly affected by the concentration of suspended solids (5 and 20 mg/L) or humic acids (2 and 5 mg/L) in the water. Mechanism analysis revealed that during the disinfection process of EBE-MW-UV, microbial DNA and proteins were initially damaged, which prevented the occurrence of dark repair and led to bacterial inactivation. In addition, UV irradiation led to the production of additional reactive oxygen species (ROS) inside the cells, increasing cell membrane permeability and exacerbating membrane damage. This was accompanied by a decrease in energy metabolism and depletion of ATP, ultimately resulting in microbial inactivation. Therefore, EBE-MW-UV demonstrated more effective disinfection than single-wavelength UV-LEDs, showing great potential. Our research gives new insights into the characteristics of multiple wavelength ultraviolet, and provides scientific basis for the selection of new light sources in the field of ultraviolet disinfection.

A new understanding of somatic coliphages belonging to the Microviridae family in urban wastewater

Somatic coliphages (SC) and F-specific RNA coliphages (FRNAPH) have been included in regulations or guidelines by several developed countries as a way of monitoring water safety and the microbiological quality of shellfish harvesting waters. SC are highly diverse in their morphology, size and genome. The Microviridae family contains three genera of phages (Alphatrevirus, Gequatrovirus, and Sinsheimervirus), all having a capsid of similar morphology (icosahedral) and size (25–30 nm in diameter) to that of common pathogenic enteric viruses. Three PCR assays specific for each genus of Microviridae were designed to study these phages in raw and treated wastewater (WW) in order to gain knowledge about the diversity and prevalence of Microviridae among SC, as well as their inactivation and removal during WW treatments. Among the four wastewater treatment plants (WWTPs) monitored here, two WWTPs applied disinfection by UV light as tertiary treatment. First, we noticed that Microviridae represented 10 to 30 % of infectious SC in both raw and treated WW. Microviridae appeared to behave in the same way as all SC during these WW treatments. As expected, the highest inactivation, at least 4 log10, was achieved for infectious Microviridae and SC in both WWTPs using UV disinfection. PCR assays showed that the highest removal of Microviridae reached about 4 log10, but the phage removal can vary greatly between WWTPs using similar treatments. This work forms the basis for a broader evaluation of Microviridae as a viral indicator of water treatment efficiency and WW reuse.

Research and Design of a Novel Hygiene Protection Handrail Based on Pyroelectric Infrared Sensing

This article focuses on the widespread prevention of public health incidents and the promotion of smart cities, proposing a low-cost and widely accessible intelligent health protection railing based on pyroelectric infrared sensing. The railing consists of three main components: power supply, monitoring, and operation. In terms of power supply, the intelligent railing can be divided into solar-powered and electric-powered types depending on its usage. The monitoring part is mainly composed of pyroelectric infrared sensors, which constantly monitor the movement of individuals to determine whether to activate the ultraviolet disinfection function. The core of the operation part is the design of ultraviolet disinfection. When the sensors detect human movement, the railing automatically activates the ultraviolet disinfection function. These three components are organically integrated into the railing body and controlled by a 51 microcontroller. The various power supply options, strong applicability, high safety, and superior effectiveness of ultraviolet disinfection complement each other, making the railing widely applicable and highly functional. The design of this new type of health protection railing, with the advantages of low cost, high efficiency, and broad applicability, allows the general public to complete disinfection and protection without affecting their normal behavior, thus serving the purpose of preventing public health incidents and assisting in the advancement of smart cities.

Ultraviolet germicidal irradiation: A prediction model to estimate UV-C-induced infectivity loss in single-strand RNA viruses

Ultraviolet germicidal irradiation (UVGI) disinfection technology is effective in inactivating microorganisms. However, its performance can vary against different microorganisms due to their diverse structural and genomic features. Thus, rapid predictions of UV (254 nm) inactivation kinetics are essential, particularly for highly infectious emerging pathogens, such as SARS-CoV-2, during the extemporary COVID-19 pandemic. In this study, aiming at single-strand RNA (ssRNA) viruses, an improved genomic model was introduced to predict the UV inactivation kinetics of viral genomes using genome sequence data. First, the overall virus infectivity loss in an aqueous matrix was estimated as the sum of damage to both the entire genome and the protein capsid. Then, the “UV rate constant ratio of aerosol and liquid” was used to convert the UV rate constant for viruses in a liquid-based matrix to an airborne state. The prediction model underwent both quantitative and qualitative validation using experimental data from this study and the literature. Finally, with the goal of mitigating potential airborne transmission of ssRNA viruses in indoor environments, this paper summarizes existing in-duct UVGI system designs and evaluates their germicidal performance. The prediction model may serve as a preliminary tool to assess the effectiveness of a UVGI system for emerging or unculturable viruses or to estimate the required UV dose when designing such a system.

Multi-target assessment of advanced oxidation processes-based strategies for indirect potable reuse of tertiary wastewater: Fate of compounds of emerging concerns, microbial and ecotoxicological parameters

Two advanced oxidation processes (AOPs), namely ozone/H2O2 and UV/H2O2, were tested at pilot scale as zero-liquid-discharge alternative treatments for the removal of microbiological (bacteria and viruses), chemical (compounds of emerging concern (CECs)) and genotoxic responses from tertiary municipal wastewater for indirect potable reuse (IPR). The AOP treated effluents were further subjected to granular activated carbon (GAC) adsorption and UV disinfection, following the concept of multiple treatment barriers. As a reference, a consolidated advanced wastewater treatment train consisting of ultrafiltration, UV disinfection, and reverse osmosis (RO) was also employed.The results showed that, for the same electrical energy applied, the ozone/H2O2 treatment was more effective than the UV/H2O2 treatment in removing CECs. Specifically, the ozone/H2O2 treatment, intensified by high pressure and high mixing, achieved an average CECs removal efficiency higher than UV/H2O2 (66.8% with respect to 18.4%). The subsequent GAC adsorption step, applied downstream the AOPs, further improved the removal efficiency of the whole treatment trains, achieving rates of 98.5% and 96.8% for the ozone/H2O2 and UV/H2O2 treatments, respectively. In contrast, the ultrafiltration step of the reference treatment train only achieved a removal percentage of 22.5%, which increased to 99% when reverse osmosis was used as the final step.Microbiological investigations showed that all three wastewater treatment lines displayed good performance in the complete removal of regulated and optional parameters according to both national and the European Directive 2020/2184. Only P. aeruginosa resulted resistant to all treatments with a higher removal by UV/H2O2 when higher UV dose was applied. In addition, E. coli STEC/VTEC and enteric viruses, were found to be completely removed in all tested treatments and no genotoxic activity was detected even after a 1000-fold concentration.The obtained results suggest that the investigated treatments are suitable for groundwater recharge to be used as a potable water source being such a procedure an IPR. The intensified ozone/H2O2 or UV/H2O2 treatments can be conveniently incorporated into a multi-barrier zero-liquid-discharge scheme, thus avoiding the management issues associated with the retentate of the conventional scheme that uses reverse osmosis. By including the chemical cost associated with using 11–12 mg/L of H2O2 in the cost calculations, the overall operational cost (energy plus chemical) required to achieve 50% average CECs removal in tertiary effluent for an hypothetical full-scale plant of 250 m3/h (or 25,000 inhabitants) was 0.183 €/m3 and 0.425 €/m3 for ozone/H2O2 and UV/H2O2 treatment train, respectively.

A Systematic Review on the Application of Ultraviolet Germicidal Irradiation to HVAC Systems

With the renewed focus on indoor air quality (IAQ) due to “Sick building syndrome” and the recent COVID-19 pandemic, the availability of innovative components and innovative guidance for maintenance and systemic safety design will play an important role, with HVAC systems as protagonists. UV-C irradiation has been investigated for a long time, and some system solutions are known. The aim of this work is to provide an overview of the latest outcomes related to the innovative components of HVAC systems using UV-C irradiation and investigate the current state of the art. A procedure based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was adopted, and the Scopus database was used to query the relevant literature. A total of 66 publications qualified for inclusion in the survey: 29 articles report experimental investigations, 24 articles are related to numerical or theoretical analysis, and both approaches were used in 13 articles. Many papers deal with upper-room UVGI, AHUs, and ducts. A few papers analyse mobile devices. The evaluation of the dose, as in the case of the definition of irradiance, is reported in a small number of articles. This lack of information makes the scenario imprecise and non-quantitative.

Quantitative Microbial Risk Assessment for Quantification of the Effects of Ultraviolet Germicidal Irradiation on COVID-19 Transmission.

Quantitative microbial risk assessment (QMRA) is presented as a tool for evaluation of the effectiveness of ultraviolet germicidal irradiation (UVGI) systems for the disinfection of indoor air. The QMRA is developed in the context of UVGI system implementation for control of SARS-CoV-2 infection and comprises submodels to address problem formulation, exposure assessment, and health effects assessment, all of which provide input to a risk characterization submodel. The model simulations indicate that UVGI systems can effectively control the risk of infection associated with SARS-CoV-2 for low to moderate virus emission rates. The risk of disease transmission is strongly influenced by the rate of pathogen emission by an infected individual, the output power of UVGI fixtures and their configuration, the source of UV-C radiation implemented in the UVGI fixtures, and the characteristics of the heating, ventilation, and air conditioning (HVAC) system. The QMRA framework provides a quantitative link between UVGI/HVAC system characteristics and changes in the risk of disease transmission. The framework can be adapted to other airborne pathogens and provides a rational basis for the design, testing, and validation of UVGI systems.

Numerical simulation study of indoor disinfection spray distribution based on CFD-DPM method

In today's world, environmental safety has become a top priority, with a special focus on terminal disinfection of indoor environments, which has proven to be a crucial and formidable issue in infection control. The use of hydrogen peroxide disinfection through vaporization or atomization presents a viable solution to the challenges posed by traditional wiping disinfection and ultraviolet disinfection methods that are plagued by incomplete disinfection and other factors that can significantly reduce the virus content within a room. To improve the application of hydrogen peroxide disinfection spray, the CFD-DPM (Computational Fluid Dynamics-Discrete Particle Model) method is employed to simulate the particle distribution of traditional sprays in a 30 m3 room. The study places emphasis on analyzing the impact of the placement position and bottle number of disinfection spray on the distribution of spray particles. The results demonstrate an impressive consistency between the numerical simulation method and experimental findings regarding the particle size distribution of disinfectant spray across various Schemes, validating the method's accuracy and reliability. However, the placement of a single disinfection spray source is insufficient to achieve uniformly distributed particles throughout the space when a bathroom is present within a given room. Nevertheless, by placing internal and external sources within the bathroom, the distribution of disinfectant spray particles becomes more even, thanks to a well conceived placement technique and an increased number of spray sources. Among all the schemes tested, Scheme 4 stands out for its ability to produce the greatest number of spray particles, with almost 60.71% of these particles remaining airborne for over 40 s. Therefore, it is also the most effective scheme for conducting disinfection.

Ultraviolet disinfection (UV-D) robots: bridging the gaps in dentistry.

Maintaining a microbe-free environment in healthcare facilities has become increasingly crucial for minimizing virus transmission, especially in the wake of recent epidemics like COVID-19. To meet the urgent need for ongoing sterilization, autonomous ultraviolet disinfection (UV-D) robots have emerged as vital tools. These robots are gaining popularity due to their automated nature, cost advantages, and ability to instantly disinfect rooms and workspaces without relying on human labor. Integrating disinfection robots into medical facilities reduces infection risk, lowers conventional cleaning costs, and instills greater confidence in patient safety. However, UV-D robots should complement rather than replace routine manual cleaning. To optimize the functionality of UV-D robots in medical settings, additional hospital and device design modifications are necessary to address visibility challenges. Achieving seamless integration requires more technical advancements and clinical investigations across various institutions. This mini-review presents an overview of advanced applications that demand disinfection, highlighting their limitations and challenges. Despite their potential, little comprehensive research has been conducted on the sterilizing impact of disinfection robots in the dental industry. By serving as a starting point for future research, this review aims to bridge the gaps in knowledge and identify unresolved issues. Our objective is to provide an extensive guide to UV-D robots, encompassing design requirements, technological breakthroughs, and in-depth use in healthcare and dentistry facilities. Understanding the capabilities and limitations of UV-D robots will aid in harnessing their potential to revolutionize infection control practices in the medical and dental fields.

Considerations for determining the performance of ultraviolet light emitting diode fluid disinfection systems.

The International Ultraviolet Association (IUVA) Task Force was formed to develop guidelines regarding testing and reporting on performance of UV LED water disinfection systems. The goal was to provide clarity in a guidance document on measuring system performance across the global UV LED water disinfection system market. A review of current performance measurement protocols for mercury lamp based systems shows that the common elements of UV LED system performance measurement protocols should be as follows: specified standard for the amount of pathogen reduction required, the requirement that the validation testing be conducted by a competent facility, and that the system be continually monitored by UV sensors while in use to verify system performance unless pathogen reduction is not claimed. UV LEDs have selectable peak wavelengths, as opposed to mercury lamps that have fixed emission wavelength values. As a result of this difference, the following changes to protocols used to test mercury lamp systems are recommended. First, the use of disinfection benchmarks other than 254 nm dose, such as direct inactivation values, dose benchmarks referenced to 254 nm, and/or dose benchmarks at the UV LED emission wavelength that give the same inactivation as the original 254 nm UV dose benchmark. Second, the use of 254 nm UV water transmittance values as a placeholder, rather than an assumed correct value, for systems under test with LED wavelengths >250 nm and water transmittance values ≥87%. More research is needed for lower wavelengths and UVTs. Third, the recommendation that germicidal response UV sensors be used in UV LED based systems to ensure that the validated disinfection is delivered. Finally, additional LED-specific considerations were also noted. UV LEDs are also instant-on devices, making them ideal light sources for systems operated intermittently. Performance testing of systems operated intermittently should include a test to insure that pathogens do not migrate past the UV LEDs while the LEDs are off. UV LED devices have recognized protocols for determining the lifetime of the devices, as well as for measuring other device properties. Caution should be exercised in using these lifetime values for devices in UV disinfection systems, since the thermal environment of the devices may be different for protocol testing and disinfection system operation. PRACTITIONER POINTS: Validation of UVC LED fluid disinfection is necessary for point of use, point of entry, and municipal applications. The emission spectrum properties, considerations and measurements for output over lifetime, and unique system design considerations of UVC LEDs as light sources are factors that must be considered when evaluating fluid disinfection performance. The instant-on operation, system geometry, validation benchmarks, system sensing, water transmittance, and fouling must also be considered for UVC LED devices when evaluating fluid disinfection performance.

Is ultraviolet light disinfection fit to be the future standard for the disinfection of flexible endoscopes without a working channel?

To investigate colony-forming unit (CFU) reduction on contaminated flexible endoscopes (FEs) without a working channel after UV-C light disinfection, compared to the current disinfection method with the endoscope washer disinfector (EWD). After pharyngolaryngoscopy, a manual pre-cleaning with tap water was performed. A culture was then collected by rolling the distal 8-10 cm of the FE over an Agar plate. The FE was disinfected using the D60 (60-s disinfection process with UV-C light) or the EWD (gold standard reprocessing process with water and chemicals). Another culture was then taken. After incubation, a CFU count was performed. A total of 200 FEs without a working channel were divided equally between the two disinfection groups. After clinical use and manual pre-cleaning, 84 of the 100 (84.0%) (UV-C light group) and 79 of the 100 (79.0%) (EWD) FEs were contaminated with at least 1 CFU. FEs that showed no contamination after use were excluded from further analysis. After disinfection with UV-C light, 72 (85.7%) FEs showed no contamination (i.e., 0 CFUs) versus 66 (83.5%) FEs after reprocessing with the EWD. There is no difference in CFUs reduction on contaminated FEs without a working channel between UV-C light disinfection and the current gold standard, the EWD.

Reduction of airborne and surface-borne bacteria in a medical center burn intensive care unit using active, upper-room, germicidal ultraviolet (GUV) disinfection.

To determine the effectiveness of active, upper-room, germicidal ultraviolet (GUV) devices in reducing bacterial contamination in patient rooms in air and on surfaces as a supplement to the central heating, ventilation, and air conditioning (HVAC) air handling unit (AHU) with MERV 14 filters and UV-C disinfection. This study was conducted in an academic medical center, burn intensive care unit (BICU), for 4 months in 2022. Room occupancy was monitored and recorded. In total, 402 preinstallation and postinstallation bacterial air and non-high-touch surface samples were obtained from 10 BICU patient rooms. Airborne particle counts were measured in the rooms, and bacterial air samples were obtained from the patient-room supply air vents and outdoor air, before and after the intervention. After preintervention samples were obtained, an active, upper-room, GUV air disinfection system was deployed in each of the patient rooms in the BICU. The average levels of airborne bacteria of 395 CFU/m3 before GUV device installation and 37 CFU/m3 after installation indicated an 89% overall decrease (P < .0001). Levels of surface-borne bacteria were associated with a 69% decrease (P < .0001) after GUV device installation. Outdoor levels of airborne bacteria averaged 341 CFU/m3 in March before installation and 676 CFU/m3 in June after installation, but this increase was not significant (P = .517). Significant reductions in air and surface contamination occurred in all rooms and areas and were not associated with variations in outdoor air concentrations of bacteria. The significant decrease of surface bacteria is an unexpected benefit associated with in-room GUV air disinfection, which can potentially reduce overall bioburden.