Co-Authors: A. Singh, B. Pendyala and A. Patras

In the food and dairy industries, the transmission of infectious diseases and bioaerosol-induced cross-contamination pose significant challenges. Understanding bioaerosols and developing techniques for their inactivation are crucial for public health and food safety. Our study tested the effectiveness of an ultraviolet light-emitting diode (UV-C LED) system having a peak at 279 nm in inactivating bioaerosols of kanamycin-resistant Escherichia coli C3040, Salmonella enterica serovar Enteritidis (ATCC 4931), and Pseudomonas fragi (ATCC 4973) on food contact surfaces. We selected silicon rubber, borosilicate glass, and stainless steel (316L) surfaces for our experiments. In a modified glass chamber, a 50µL cell suspension was aerosolized using a BLAM Nebulizer at 25 psi and then deposited onto surface coupons. The microbial enumeration was conducted using the serial dilution method, with exposures performed in triplicate and plating duplicates. Experimental data was fitted to Bi-phasic kinetic model with high R2 and low RMSE values. A rapid initial inactivation followed by slower kinetics was observed. Glass surfaces exhibited the highest microbial inactivation (2.86, 3.84, and 3.56 log CFU/mL for E. coli, Salmonella, and P. fragi, respectively), followed by stainless steel and silicon rubber. Our findings demonstrate the potential of UV-C LEDs in disinfecting bioaerosols deposited on food contact surfaces.

Co-Authors: Becca Winter

In the realm of public health and safety, the continuous improvement of disinfection technologies is paramount. This presentation explores the transformative power of customer feedback in driving innovation of ultraviolet (UV) disinfection devices. Engaging end-users, understanding their needs, and incorporating their insights into the design process leads to highly effective and user-friendly UV disinfection solutions.

The presentation will delve into the collection and analysis of customer feedback, emphasizing its role in identifying strengths, weaknesses, and opportunities for enhancement in existing UV disinfection devices. Close collaboration between product development engineers, environmental services users, infection prevention professionals, and microbiologists will be highlighted as key to successful innovation. Furthermore, the presentation will address the importance of establishing robust feedback channels to support real-world data collection and continuous improvement efforts. Case studies will highlight instances where customer feedback has resulted in increased efficacy, ease of use, and overall customer satisfaction.

The role of customer feedback in shaping the next generation of UV disinfection devices is not only crucial for product development but also for building trust and credibility within the market. By creating an open dialogue, we can adapt to emerging challenges, stay ahead of evolving pathogens, and refine our products to better meet the dynamic needs of various industries, including healthcare, hospitality, and beyond. Explore the fascinating journey of turning customer insights into cutting-edge solutions that redefine the landscape of ultraviolet disinfection technology.

Co-Authors: Dr. John DuPuis, M.D.

www.esp-dlux.com
ann.dupuis@esp-dlux.com

Introduction: Food processing companies invest significant resources into controlling environmental contamination. One important concern is the control of Listeria monocytogenes. The USDA has a “zero tolerance” for Listeria. The disinfecting properties of UVC are well known, but its practical application in food processing has been difficult. This study evaluates the efficacy of the patented ESP-DLux™ to reduce contamination in meat processing.

Methods:
Cultures and Inoculation: Fresh ground beef was mixed with sterile saline in a 1:2 ratio. Cultures of Listeria were grown individually in trypticase soy broth with 1% yeast extract. A brush was used to apply the Listeria cells to the floor tile, stainless steel, plastic and tile grout. The inoculated surfaces were allowed to dry for at least 30 minutes prior to the application of the UV. The ESP-DLux™ was positioned at 2 meters directly above the inoculated floor tile and was operated following the manufacturer’s instructions for varying exposure periods.

Results Log10 reductions:
The stainless steel log10 reduction exceeded five point five. The plastic log10 reduction exceeded five point two. The tile log10 reduction exceeded four point five. The grout log10 reduction exceeded three.

The porous nature of grout results in a surface which is difficult to clean and sanitize by any method. UV light travels in straight lines, and it is easy to imagine how a bacterial cell, in the porous grout, could be out of the direct line of UV irradiation. A three log10 reduction in population, under these conditions with a very heavy inoculum, is an important finding. This finding demonstrates that with sufficient dosage time, the ESP-DLux™ alone can achieve higher germicidal efficacy than standard mopping, even with enhanced brushes and disinfectant dwell time, while requiring no additional labor costs.

Co-Authors: Brandon E. Boor, W. Travis Horton, Zhi Zhou, Ernest R. Blatchley III

At present, the technologies that have shown the greatest promise for control of airborne pathogens include: increased introduction of outside air (i.e., alteration of HVAC system operating conditions), filtration, and ultraviolet (UV) irradiation. However, data are generally lacking to quantify the characteristics and behavior of these technologies in relevant indoor environments. To address this issue, a surveillance program has been initiated to quantify the effects of UV-C-based air disinfection systems on microbiological and chemical aspects of indoor air quality (IAQ) in occupied, indoor spaces.

The study is based on four “Living Labs” located within the Ray W. Herrick Laboratories at Purdue University. These four rooms, which were designed to facilitate studies of IAQ and are used as graduate student office space, as essentially identical in terms of physical geometry. Each of the rooms is equipped with a dedicated HVAC system, each of which is extensively instrumented and controllable. One of the four Living Labs has been retained in its original configuration to serve as an experimental control. The remaining Labs are configured with UV-C fixtures that are representative of current UVGI options, including: a conventional upper-room configuration based on low-pressure Hg lamps; a system based on optically-filtered KrCl* lamps; and a system based on UV LEDs.

Microbial IAQ within the Living Labs is monitored by a protocol in which a condensation-based bioaerosol sampler is used to collect aerosol samples. The aerosol samples are then subjected to nucleic acid extraction, with subsequent analysis by qPCR to identify the viral species that are present within the aerosol samples.

Monitoring of ozone dynamics is applied as a first step in characterization of chemical IAQ. Ozone concentration is monitored in real time in each room. These measurements illustrate the dynamic behavior of indoor ozone in occupied rooms and are being compared with results of a numerical model that was developed to simulate ozone dynamics.

Lastly, spherical actinometry is applied within the rooms that have been fitted with UVGI systems to quantify the spatial distribution of radiant energy within each room. The results of these measurements will be compared with the results of numerical simulations based on ray tracing. In addition, these results will be compared with the current Threshold Limit Values (TLVs) for skin and eye exposure at wavelengths that characterize the output of each UVGI system used in this study.

Co-Authors: Joyce Lehman, Bryan Townsend

As a part of the Pure Water Southern California program, MWD is planning to implement a full-scale potable reuse facility capable of producing 150 MGD, including the world’s largest UV Advanced Oxidation (AOP) system to date. UV AOP Systems can achieve simultaneous pathogen and chemical control requirements, but industry knowledge in technology and controls have been evolving rapidly over the past decade. Current UV AOP systems are operated using a variety of online instrumentation and performance metrics to monitor driving process variables, performance, and maintain compliance with local regulations. UV AOP technology and understanding have significantly evolved over recent years, resulting in more sophisticated performance metrics designed to enhance performance and increase operational efficiency.

This presentation will review conventional and innovative approaches to UV AOP performance metrics that were quantitatively evaluated at MWD’s demonstration facility. UV AOP monitoring approaches including Electrical Energy Dose, Electrical Energy per Order, Reduction Equivalent Dose, Log Removal Value, and Dose-Product will be defined and discussed regarding their pros and cons to UV AOP operations. Data from a two-year monitoring and testing period, including UV AOP challenge testing, at the demonstration facility will be presented to demonstrate goodness-of-fit for each performance metric achieved in the period. Lessons learned from the project included identifying areas of further optimization, such as required instrumentation needed to validate UV Dose prediction at the pilot scale and how alternative strategies and advanced modeling can incorporate available data to monitor performance. This presentation will discuss the largest UV AOP system to ever be designed in the world, performance metrics and their success in correlating performance based on pilot challenge testing results, and additional considerations MWD and other projects should consider when determining their performance metric options for a UV AOP system.

Co-Authors: Hannah Ray, Eric Wert

Legionella is not regulated in groundwater, but widespread occurrence in untreated Las Vegas Valley groundwater has been documented. In addition to the existing on-site chlorination, LVVWD/SNWA chose to pursue UV-C disinfection at these wells to provide additional public health protection. Results from bench scale collimated beam tests will be presented, showing native L.pneumophila in groundwater was UV sensitive (LP-254 nm, LED-255, 265, 280nm), but less than in previous studies in literature. Bench-scale UV-LED testing performance led to the procurement of the first full scale municipal UV-LED reactor in the US (provided by Aquisense). Full-scale system design and results with low pressure UV and UVLED will be presented, along with a comparison of the benefits, barriers, and challenges encountered during pilot trials. Considering that UV-LED application and Legionella both have minimal federal guidance/guidelines, LVVWDs approach for regulatory acceptance of a multibarrier treatment approach (UV (LP or LED)+chlorination) for Legionella will be discussed. Finally, the ongoing research on this subject will be introduced and updates provided.

Co-Authors:

The session will review the progress made by the Industry Working Group on the initiatives related to the application of GUV systems in public spaces. The objectives, action plans and task force activities will be discussed. This will be an opportunity to discuss and highlight the key items identified during the working group activities and elicit further participation from the IUVA community.

Co-Authors: Athira Haridas, Leila Alidokht, Katrina Fitzpatrick, Caitlyn Butler, Mariana Lanzarini-Lopes

Ultraviolet (UV) light has been proved to be effective in biofilm prevention by inactivating a wide range of microorganisms by damaging their genetic material A novel apparatus, UV-emitting glass (UEG), that can glow UV light from glass surface has been developed in our research group at the University of Massachusetts Amherst to prevent the establishment and growth of biofilm. The proof-of-concept tests have been conducted in-situ and the results confirmed that that UV-emitting glass is a technology with significant environmental impact and should be considered a promising strategy for biofilm inhibition on transparent surfaces. We now seek to understand the benefits of different wavelength emission within the UEGs. In this presentation we will discuss results of biofilm prevention study using 365nm, 310nm, 280nm, and 265nm light emission from UEGs. We will discuss results from using both a model biofouling organism (Pseudomonas bacteria) and marine bacteria derived from Port Canaveral marine, Florida, United States. The results revealed that the most effective wavelength, 265nm, achieved 3.5 and 3.25 Log reduction in preventing biofilms of Pseudomonas bacteria and marine bacteria, respectively, followed by 280nm, 310nm, and 365nm. Additionally, in this presentation we will discuss the mechanisms which are present for biofilm prevention from each wavelength when emitted from the surface of interest and how these results can change in different aqueous environments depending on the radical formation potential. The research aims to advance our comprehension of how various UV wavelengths can inhibit biofilms, with potential applications across industries such as water treatment, healthcare, marine protection, and food processing.

Co-Authors: Shahriar Rouhani, Milad Raeiszadeh

Airborne transmission of bacteria and viruses remains a significant route for the dissemination of diseases including SARS-COV-2. Ultraviolet (UV) radiation has proven to be an effective method for disinfecting air. However, conventional UV lamps have limitations such as fragility, mercury content, and a lack of flexibility in their form factor which hinder their widespread adoption. In contrast, ultraviolet light emitting diodes (UV-LEDs), on offer robustness, compactness, and greater design flexibility making them suitable for creating energy-efficient and highly effective air disinfection systems.

In this presentation, we will showcase the results of our experimental analysis, where we compare the disinfection performance of UVC with alternative methods like photocatalysis, and filtration. Employing the computational fluid dynamics (CFD), we will present several case studies that illustrate the integration of a virtual UV-LED disinfection system within a public bus, highlighting its effectiveness in reducing the risk of infection for passengers close to an infectious person. Additionally, we will present the test results of our technology as evaluated by an independent biosafety level 3 laboratory against SARS-CoV-2 in various scenarios that matches real life situations inside confined spaces. We will demonstrate how our proprietary collimation technology, IntenseBeamTM, enables precise adjustment of UV-LED radiation through a series of optical lensing, resulting in significant advantages for the design of air disinfection units. Furthermore, we will also discuss the importance of proper airflow distribution, in addition to the clean air delivery rate (CADR). Ultimately, our findings pave the way to achieving clean air by widely incorporating UV-LEDs into the heating, ventilation, and air conditioning systems (HVAC) of wide range of motor vehicles, airplanes, and buildings.

Co-Authors: Karl G. Linden; Emma M. Payne

Traditional low-pressure UV (LPUV) lamps emit light at 254 nm which is effective at disinfection but also a health hazard to skin and eyes when exposed. By contrast, KrCl* excimer lamps emits UV in the far-UVC range (200-222 nm) and has been shown to effectively kill pathogens without potentially damaging human tissues. Numerous papers have been published demonstrating that far-UVC is safer for human exposures and more effective at disinfection than LPUV, however, limited studies have investigated the use of KrCl* excimer lamps for UV/advanced oxidation processes (AOPs).

First, we compared the formation of OH radical in 3 different AOP systems, LPUV/peroxide, KrCl*/peroxide, and KrCl*/nitrate. In the lab grade water experiment, results show that UV/nitrate had the highest level of steady-state OH concentration, followed by KrCl*/peroxide, and then LPUV/peroxide. Same results were found in the same experiment using groundwater.

Second, we compared contaminant degradation between LPUV and KrCl* excimer lamps for both carbamazepine and NDMA. Results show that direct photolysis by KrCl* excimer lamps significantly improves the degradation rate constants of both carbamazepine and NDMA compared to LPUV, likely due a higher molar absorption coefficient at 222 nm compared to 254 nm. KrCl*/AOP was able to further improve carbamazepine degradation compared to KrCl* excimer direct photolysis but didn’t improve the degradation of NDMA.

Next, we investigated the degradation pathways of carbamazepine through direct photolysis of KrCl* excimer lamps in lab grade water utilizing a high-resolution liquid chromatography mass spectrometry (LC/MS). Despite no radical promoters present in the water, results demonstrated that both direct photolysis and AOP are involved in the degradation process. This shows that a de facto AOP can occur when utilizing KrCl* excimer lamps and can potentially be a cost-saving alternative to conventional LPUV.

Co-Authors: Karl G. Linden, PhD; Michael J. Watts, PhD, PE

Advanced Oxidation Processes (AOP) are utilized in more than 50% of global potable reuse treatment facilities. They can serve a vital role in mitigating residual chemical contaminants and pathogens. However, applying UV AOP downstream of reverse osmosis (RO) membranes has been the rule for potable reuse treatment. The reported pilot project examined the performance of AOP downstream of a carbon-based treatment train. Ozone/biological active filtration (O₃/BAF) was utilized prior to UV/AOP. Low-pressure UV coupled with hydrogen peroxide (UV/H₂O₂) and sodium hypochlorite (UV/HOCl) were both tested. 8 chemical contaminants based on the intrinsic chemical properties (i.e. second order reaction rate with •OH, chlorine and O₃, logK_ow, etc) were examined.

During the O₃/BAF process, a mgO₃/mgDOC=1 produced the optimal overall results. 7 out of 8 selected compound exhibited good removal percentage (>60%), in addition to 63% of effluent organic matter (EfOM) being removed. UV transmittance (UVT) also improved from 88.9% to 93.5%. For UV/AOP, both H₂O₂ (10 mg/L) and HOCl (7 mg/L) were tested. HOCl performed the same or better compared to H₂O₂
These results demonstrated that a carbon-based pre-treatment for downstream AOP is a viable alternative to (RO), and will elucidate the opportunities and challenges for AOP for inland potable reuse.

Co-Authors: Ryan Popko, Aswathi Pradeep

Ultraviolet (UV) Advanced Oxidation Processes (AOPs) are a critical part of advanced water treatment facilities for potable reuse applications. UV AOP is traditionally employed downstream of reverse osmosis (RO), the permeate of which normally contains a chloramine residual to protect against membrane biofouling. Sodium hypochlorite is fed in the RO permeate to establish a free chlorine residual in the UV reactor influent, however the hydraulic residence time (HRT) prior to the UV reactor is typically inadequate to achieve breakpoint chlorination. This results in a dynamic water quality where free chlorine and monochloramines are continuously consumed with a corresponding increase in dichloramines as the water flows from the point of hypochlorite injection to the UV reactor.

The dynamic nature of this unstable water quality presents a unique challenge with regards to the measurement of a UVT and free chlorine concentration that is representative of that entering the UV reactor due to differences in HRT between the analyzer sample line and the main treatment train. Experience derived from several AOP projects have led to an increased understanding of the complications associated with monitoring of this dynamic water quality and the development of various solutions which have been incorporated in the designs of recent advanced treatment facilities, including JEA’s H2.0 Purification Center.

The H2.0 Purification Center, located in Jacksonville, Florida, is a 1 mgd indirect potable reuse demonstration facility incorporating micro/ultrafiltration (MF/UF), RO, and UV/Chlorine AOP as the main treatment processes. Strategies implemented in the UV AOP design to address the dynamic water quality challenges include various elements associated with the piping layout, hypochlorite injection and sample port locations for HRT optimization, in addition to more novel concepts incorporating alternative locations for water quality monitoring and active flow monitoring/control of analyzer sample lines. Center startup/commissioning activities will include testing to evaluate the effectiveness of several optional approaches to identify the preferred solution(s) for implementation in the UV AOP controls.

Co-Authors: Yuqin Zong

Customers are asking a lot of a single UV-C radiometer given the variety of applications required to be measured for a germicidal ultraviolet installation. The Illuminating Engineering Society is working on a Technical Memorandum to help educate the community on the characteristics of UV-C radiometers and the importance of such characteristics under different applications. As an example, a UV-C radiometer can be used to measure the irradiance on a surface from a UV-C device to determine is potential effectiveness. A UV-C radiometer can also be used to measure the fluence rate from a UV-C device to determine the allowable exposure to human occupants. The measurement levels for these two applications are more than 4 orders of magnitude different creating a significant linearity challenge for a single UV-C radiometer.

Another potential sensitivity is the detection of optical radiation or light that is not UV-C. While many UV-C radiometers are advertised as ‘solar blind,’ which means the detection of the solar spectrum at sea level (300 nm – 2500 nm), many register a signal. This sensitivity can be overwhelming if someone is trying to validate an installation in a hallway or room where sunlight coming through a window is present. Some UV-C radiometers have been shown to be sensitive to general illumination from halogen or solid-state lighting devices present in an office or meeting room. Characterization of this sensitivity helps the user understand what environmental conditions are required to make accurate measurements.

Several more examples will be provided along with the full description of the content of the Technical Memorandum under development.

Co-Authors: Christian Grau, Frank Tistle

During this talk attendees will hear how a foundry making truck parts was able to install a new custom designed photooxidation system to meet VOC emission requirements. Due to production growth, the foundry’s existing UV reactor was no longer able to meet their VOC emissions requirement. During the mold production process the sand binder releases VOC´s as it hardens the sand molds. Photooxidation is an effective and efficient procedure to eliminate low VOC concentrations.

Finding an acceptable solution was challenging since there was no space to install additional UV reactors. Additionally, a new process in the plant caused the exhaust air temperature to increase which decreased the operating life of the existing germicidal lamps. In turn, this increased maintenance costs since the germicidal lamps were not reaching their promised life expectancy.

The plant personnel worked with the Heraeus Noblelight’s technical and R&D team to develop a custom lamp to achieve the following goals:

• Meet the official VOC emissions requirements
• Increase the efficiency of the exhaust air treatment without increasing the space of the UV reactor.
• Guarantee maximum VUV output at the higher exhaust air temperatures.
• Minimize the decline of VUV output over the lifetime of the lamps.
• Reduce total cost of ownership

The presentation will include details about the existing germicidal system, the new system design solution, both lamps and overall system, and the resulting benefits for the foundry. Attendees will gain a better understanding of how different UV technologies and custom solutions can cost effectively meet their air treatment challenges.

Co-Authors: Christopher A. Bowers, Richard Rasansky, Joel Ducoste

UV irradiation is increasingly being used to disinfect air at both room and personal protection levels. Reflectivity of surfaces is expected to impact the disinfection potential of UV treatment systems. Using reflective materials in an enclosed space can increase the UV dose by orders of magnitude. Thus, accurate measurement of reflectivity for various materials is beneficial when designing UV air treatment technologies.

Existing methods to determine reflectivity of interchangeable materials are either unwieldy when testing various materials, such as using an integrating sphere, or inaccurate when measuring reflection of diffuse reflective materials with a collimated beam set to a 45-degree incident angle. To eliminate these shortcomings, a new bench scale device has been designed to rapidly measure the surface reflectance of various materials when irradiated with any wavelength of UV. The Parabolic Reflectometric Capsule (PBRC) device contains a parabolic mold that allows a small surface area measurement of the material’s reflectivity in a specially designed chamber that captures the UV source rays reflected from the sample surface. The PBRC can accommodate any UV irradiation source to measure the reflectivity of both specular and diffuse material, as required.

LTI Optics Photopia was used to generate optical simulations of several design configurations with various UV sources and reflective material to assess the PBRC for optimal performance. In all investigated cases, optical simulations demonstrated that the PBRC predicts the reflectivity of both specular and diffuse reflective materials, especially at high reflectivities (>80%). At these reflectivities, the relative error between the value estimated from simulations and the reflectivity tabulated for the simulated material was less than 1%. Overall, the PBRC device has the potential to greatly simplify reflectivity measurements, provide similar accuracy compared to other standard methods, such as using an integrating sphere, and reduce the experimental testing time and cost.

At least 2 billion people worldwide use drinking water sources that are contaminated with feces, causing waterborne diseases: poor sanitation, poor hygiene, and unsafe drinking water result in a daily death rate of more than 800 children under 5 years of age from diarrheal diseases. Most of these cases occur in the developing and underdeveloped world, people collect the water from contaminated lakes or unmaintained community sources, storing it in filthy water tanks, according to the WHO. Current solutions for water disinfection in low-income countries are mainly chemical-based or physical-based mainly filters, they can be effective in some scenarios but do not properly address the challenges of the rural area due to costs, dependent on supply availability, or heavy manual maintenance. Most of the UVC solutions, including UVC- (light-emitting diodes) LED, are not fit for low-income countries since they are operating with electricity, the UVC-LED is expensive and most of the design is fragile and not flexible to different field scenarios. The research study an off-gris remote area use case who suffer from low quality of water quality. This research aims to investigate the feasibility and overall impact of introducing a point-of-use (POU) and point-of-entry (POE) UV-LED water disinfection device at the household level and community level in Namuseru village, Uganda with collaboration with Innovation: Africa. The research aims to take a comprehensive approach by examining microbiological parameters, residual chlorine concentrations and health implications. In addition to testing the disinfection effectiveness of the devices, we examine how household perceptions affect the relationship between water quality and infections before and after the implementation of a POU water disinfection device.

Co-Authors:

When the pandemic hit the world, UK was as surprised and in shock as the rest of the world. The various health care boards in the UK quickly realized extraordinary measurements needed to be taken. UK quickly adapted, developed and expanded their usage of UV-C as an efficient source of disinfection, and it seems they have learnt from the pandemic, since today they are one of the most advanced countries in Europe when it comes to usage of UV-C , and that is a position they are striving to keep. One of the problems that prevent further UV-C expansion and penetration in European healthcare is the lack of standards. When there is a standard to lean on or compare with, or when procedures become mandatory, steps will automatically be taken in the right direction and results will follow. Luckily and finally we now one standard in the leading country, the British Standard BS 8628:2022 that now also include UV-C devices in healthcare, which is a very important step in the right direction, giving credibility and acknowledgment and making UV-C disinfection an equally accepted method for pathogen disinfection. But which criteria’s was the UV-C device tested against? Which parameters had to be ticked off? Which device/s made it through the eye of the needle? How was the result measured? Which type of measurement tools were used? And how did the selected measurement tools - the color changing dosimeters from Intellego Technologies played a crucial part in the results assessment and achievement? Will this standard impact rest of Europe and also other parts of the world and how will this impact the UV industry?

Co-Authors: none

Vacuum UV radiation, because of its ability to break chemical bonds, has long been studied and used for a variety of applications. VUV Technologies Inc. has recently introduced proprietary corona discharge lamps providing high-power VUV light at 172 nm. Typical electrical efficiency is ~50% with a theoretical maximum > 65%. The lamps are instant start/stop and can be electronically controlled. In addition they are operable over a wide range of temperatures and can be directly immersed in water. Lamps can efficiently produce ozone in dry air or in oxygen atmosphere with ozone yields exceeding 200g/kWh. A single photon splits O2 into two oxygen atoms that combine with other O2 molecules to yield two ozone molecules. Maximum ozone concentrations exceeding 30% are possible with oxygen feed and exceeding 7% with dry air feed. Similarly, photochemical cleavage of water provides both OH. and free proton radicals for advanced oxidation applications. Tubular lamps (4cm diameter) can be fabricated with various lengths from 10 to 100 cm and output from 7 to 75 W. Semiconductor processing, wastewater treatment and advanced oxidation technologies are just a few of the applications possible with this unique lamp.

Co-Authors: Jose Dominquez

Until recently, low pressure mercury lamps with narrow band 254 nm output, have been the standard for germicidal disinfection of water, air and surfaces. Said wavelength, near the peak of the DNA absorption curve, has been used for most of the past century. However, the toxicity of mercury, coupled with the lamp’s long warm up time and its output variability with temperature have led to the research and development of alternative GUV light sources. These include LED sources at wavelengths above 254 nm, KrCl* excimer lamps peaked at 222 nm, and broad-spectrum phosphor lamps covering the range from 200 to 280 nm. Numerous investigators have studied the wavelength sensitivity, or effectiveness, of GUV in the region from 200 to 300 nm for a variety of pathogens including viruses, bacteria and other harmful microorganisms. For most species, the wavelength sensitivity does not directly follow the DNA absorption spectrum with significant enhancements typically noted in the region from 200 to 240 nm. A figure of merit for GUV lamps, in units of relative sensitivity per watt of UV light, can be obtained by integrating the convolution of the sensitivity curve for a specific microbe with a lamp’s output spectrum normalized to 254 nm. Other parameters also important to consider for specific applications include the light source cost per watt, its power efficiency, useful lifetime and absorption in the medium irradiated. Results for several lamps and microbes are considered. In general, especially for multiple species present, a broad-spectrum light source is preferable.

Co-Authors: Saya Han, Peter Chung, Pratibha Sharma

Ultraviolet light-emitting diodes are highly adaptable, narrow wavelength light sources with no-warm-up times, and with commercial availability in small packages making them suitable for complex engineering applications. However, due to low efficiencies and a low single chip output flux, specifically at shorter wavelengths (265/275nm), a densely populated LED array, driven at higher currents is essential to attain higher optical outputs in a small emitting area. However, dense arrays imply higher junction temperatures which can negatively impact optical output, device lifetimes, and reliability. In this paper, we investigate the development of high density UVC LED arrays keeping thermal considerations in mind. Development of a modular 1W optical output array in a <2 cm2 emitting area will be shown along with package and system level temperature distributions determined using thermal simulations. Optical simulation results with multiple modules will be shared. The impact of using standard thermal management packaging technologies vs advanced heat extraction methodologies such as the 3-PAD technology would be investigated. With a target to maximize heat extraction at the chip and package level using a direct, low thermal resistance path from the LED junction, we will present an increase in optical output (>50%) and improvement in LED lifetimes (>4000 hrs) at high driving currents (>700mA), Finally, optical performance results along with thermal simulation data will be shared for an 8W array.

Co-Authors: Daniel Murnick, Ezra L. Cates

Direct photolysis by high energy UV photons is a relatively simple and effective method of destroying recalcitrant organic contaminants in water, including poly-/perfluoroalkyl substances (PFAS). Herein, we investigated an unconventional vacuum ultraviolet (VUV) source – a corona discharge xenon (Xe2*) excimer lamp, with emissions centered at 172 nm (7.2 eV) and a wall efficiency of up to 40%. The lamp is mercury-free, does not require a warm-up phase, and its pure noble gas composition purportedly imparts much longer lifetime compared to other excimer lamp technologies. The photodegradation of PFAS, including perfluorobutanoic acid (PFBA), perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS), was investigated using a 25 W Xe₂* lamp in an immersion photoreactor. Various treatment conditions were tested, including different initial pH, with and without N2 purging, oxidative conditions with ferric iron complexation, and reducing conditions. After a 2-hour runtime, the results revealed up to ~70% degradation of PFBA and PFOA at pH 7, and 58% degradation of PFOS under oxidation conditions with FeCl₃ at pH 3. Additional optimization was conducted by manipulating power supply pulse frequency/width and voltage settlings to maximize both intensity and electrical efficiency, as well as by optimizing reactor mixing conditions to reduce mass transfer limitations. Finally, the Xe₂* was applied to heterogeneous (h-BN) photocatalytic PFOS degradation.

Co-Authors: W. Travis Horton and Jon Douglas

ASHRAE Standard 241 provides a framework for evaluating engineering and non-engineering measures that can be implemented in indoor air spaces to provide effective control of airborne pathogens; in this context, “effective control” translates to the incorporation of control measures that reduce the risk of airborne, communicable disease transmission to acceptably low levels. Among engineering controls, process options include increased introduction of outdoor air, filtered recirculated air, and air disinfection processes. Among disinfection options, those that involve germicidal ultraviolet (GUV) radiation are regarded as having the greatest potential for pathogen inactivation, while also requiring the lowest upfront capital and long-term operating costs.

This project involves assessments of facilities at Purdue University and their conformance to ASHRAE 241 guidance. These assessments involve a range of facility types on the Purdue campus including: classrooms, lecture halls, conference rooms, restrooms, sports facilities, dining facilities, dormitory rooms, and a child care facility. This range of facility types was chosen to maximize translation of the results of this work to other settings. For each facility type, representative measurements are being conducted to quantify current Equivalent Clean Airflow rate (ECAi), based on operational characteristics of the installed HVAC system, as well as any air cleaning technologies that have been installed and that are operational (e.g., air filters, GUV systems). These values are then compared with minimum ECAi required to mitigate disease transmission risk, as defined by ASHRAE 241. For facilities where ECAi is less than the minimum ECAi required to mitigate disease transmission risk, such as when a facility needs to operate in Infection Risk Management Mode (IRMM), a further assessment of the control measures that could be implemented to conform to 241 guidance is being conducted, together with an assessment of the capital and operating costs associated with these measures.

The results of this project will inform and illustrate the impact of ASHRAE 241, including the roles that can be played by GUV systems. The results provide quantitative assessments of the conformance of existing facilities to ASHRAE 241. In addition, the results of this work will illustrate attributes of facilities that are out of conformance with ASHRAE 241, as well as quantitative comparisons of the engineering control measures that could be implemented to bring a facility into conformance.

Co-Authors: Hugo Carrisoza-Gaytan

The reduction of free residual chlorine in the water is an important step in the water treatment for human or industrial uses. The methods most employed to accomplish this, are the use of activated carbon or UV-mercury lamps. However activated carbon is a precursor of microbiological growth and the mercury lamps produce adverse effects on the environment.

The purpose of this work is to design a water dechlorination system using a 275nm UVC-LED lamp, with a flow capacity of 1 gallon per minute (GPM).

The LED-dechlorination system consists of a stainless-steel chamber with 350 mm length x 80 mm diameter, containing 5 LED cards, each card possesses 12 UVC-LEDs (0.61W per LED), mounted between an aluminum heat sink and a 90% transmittance quartz duct. The system contains a flow sensor that activates the LEDs when the water, to be treated, flows through the quartz duct, increasing the life of the LEDs and saving energy. We calculated a UV-dose of 131 mJ/cm² (at 275nm) to reduce 1 ppm of free chlorine.

The system was tested supplying water containing 1.56 ppm of free chlorine at 1 GPM. After the treatment with 131 mJ/cm² UV-dose, the output water exhibited a chlorine concentration of 0.86 ppm. The free chlorine concertation was determined by photometry.

We demonstrate the feasibility of use UVC-LED lamps to reduce free residual chlorine in water.

Co-Authors: Tianyi Chen, Chengjin Wang, Ron Hofmann

The ·OH scavenging potential indicates the consumption rate of ·OH by non-target compounds in water, which directly affects advanced oxidation design and performance. An external calibration method for measuring ·OH scavenging potential (SP) was previously developed. SP was measured by comparing the decay rates of ·OH probe - methylene blue (MB) in samples against those in standard solutions with known SPs under UV/H2O2. This method assumes that MB only reacts with ·OH, which needs to be experimentally verified. If other radicals such as carbonate radical, superoxide radical, and organic radicals consume MB, it would lead to faster MB decay than by ·OH itself, resulting in underestimated ·OH SP results. Additionally, the impact of bromide, chloride, and chloramines on SP measurement is not clear. They may have dual roles as ·OH scavengers and generators of reactive species (e.g., amino and bromine radicals) that may contribute to MB decay. Therefore, experiments were designed to create conditions featuring high concentrations of superoxide radicals, organic radicals and carbonate radicals, under which the MB decay was monitored to study whether there was interference of these radicals on SP detection. The impacts of chloride, bromide, and chloramines on SP measurement was investigated by measuring SPs of synthetic solutions with different concentrations of these species spiked. Overall, this study shows that the external calibration method using MB as the probe is immune from interferences from radicals other than ·OH, and it demonstrates significant contribution of chloramines and bromide at low mg/L levels to the ·OH scavenging potential.

Co-Authors: Jan Winderlich

UV is an established technology for the treatment of water or air in many industrial processes. New technologies always generate a lot of attention and discussion. However, improvements in already established technologies, such as UV mercury lamp technology, should be viewed with just as much attention and discussion given their potential impact on the market. This talk will discuss the NNI1500Light, a new, higher power, low pressure mercury lamp which offers significant benefits for water treatment including advanced oxidation processes.

Attendees will learn about the features and benefits of this new 1500 W low pressure lamp which has significantly higher UVC output than known lamps in the range from several 100 to 1000 W.

The new lamp design:

• Enables higher flow rates with lower head losses
• Reduces the number of lamps needed
• Offers stable output over a wide range of water temperatures
• Delivers unmatched power density

As a result users can reduce maintenance, electricity costs and downtime to improve overall treatment efficiency. Offering the lowest total cost of ownership, this new lamp is an ideal solution for large-scale water treatment installations for drinking, waste and industrial water, e.g. in agriculture, aquaculture, or food and beverage production.

Co-Authors:

On behalf of the U.S. Department of Energy (DOE), Pacific Northwest National Laboratory and Lawrence Berkeley National Laboratory are conducting research, development, and demonstration activities of germicidal ultraviolet (GUV) air disinfection technologies for their potential benefits to reduce building energy use and carbon emissions. When combined with ventilation, evidence indicates GUV is more energy-efficient and effective to reduce the spread of airborne pathogens and meet new CDC and ASHRAE building design standards than ventilation alone. This presentation will provide an overview of DOE’s GUV research and development activities. We will share findings from simulation testbeds that analyze the effectiveness and energy use of airborne pathogen mitigation measures for prototypical buildings. Measures such as increased outdoor air ventilation, more efficient filtration, and germicidal ultraviolet technologies are analyzed for meeting ASHRAE 241 and CDC standards. The results show that in-room GUV technologies can deliver equivalent clean air with 80% lower energy use and carbon emissions than ventilation strategies alone. We will also share initial findings from field assessments of real-world GUV installations in which effectiveness, safety, and occupant experience were evaluated. As part of this, we will discuss methods for quantifying realized equivalent clean airflow from GUV systems in situ. GUV systems are recognized as strategies that can be deployed to meet the ASHRAE 241 standard for control of infectious aerosols, however, the standard thus far does not specify an in situ-based method for quantifying realized equivalent clean airflow.

Co-Authors: Graham Gagnon, Bryan Townsend, Anthony Pimentel

Water Research Foundation Project 5173, Feasibility of Full-Scale Implementation of UV LED Disinfection, aims to perform a quantitative assessment of the feasibility of full-scale ultraviolet light emitting diode (UV LED) systems for drinking water and wastewater disinfection applications. As a part of the study, Black & Veatch is leading a Regulatory Committee (RC) consisting of state/province and federal regulators from the United States and Canada who will participate in the project. The RC provides a platform for the project team to engage the regulatory community to ensure the project is properly addressing the concerns and potential challenges for implementation in municipal applications from a regulatory perspective. In addition, the RC provides participating regulators an opportunity to engage one another and play an active role in the development of guidance and protocols for the implementation of LEDs in municipal disinfection applications.

As part of the project kickoff, a survey was provided to the RC to (i) gage the existing level of knowledge and comfort with UV LED technologies; (ii) identify the drivers and characteristics of UV LEDs that would favor their installation in municipal applications; and (iii) determine the concerns, barriers and knowledge gaps that need to be addressed prior to implementation from a regulatory perspective. This presentation will review the goals and role of the regulatory committee in the project and discuss the results of the survey to provide insight from a regulatory perspective regarding the implementation of UV LED in municipal disinfection applications.

Co-Authors: Kyle M. Schei

The National Association of Lighting Management Companies (NALMCO) is offering a Germicidal Ultraviolet Training and Certification Program for professionals who are responsible for the design, installation, and maintenance of germicidal UV-C luminaires. The program aims to provide participants with a comprehensive understanding of germicidal UV-C technology and its effective implementation in various industries. The program covers the following topics:

• Introduction to germicidal UV-C technology and its principles and mechanisms of disinfection
• Safety considerations and protocols for the proper and safe use of germicidal UV-C luminaires
• Installation and maintenance requirements and best practices for germicidal UV-C luminaires
• Case studies and real-world applications of germicidal UV-C technology in different settings
• Hands-on training and practical demonstrations of germicidal UV-C equipment
• Certification examination to assess the knowledge and skills of the participants

The program is facilitated by industry experts who have extensive experience in UV-C technology and its applications. Upon successful completion of the program, participants will be certified as UV-C Management Consultants and will be able to install, maintain, and utilize UV-C equipment safely and effectively. The program is designed to equip participants with the necessary skills and knowledge to enhance their disinfection practices and promote a healthier environment.

The presentation goal is to provide insights in how our team partecipated in drawing the training content and bring the expertise “from the field” to train professionals with a practicle perspective. We will share also a review of the training due in March in Dallas, during 2024 NALMCO Spring Seminar.

Co-Authors:

This study investigates the effectiveness of simultaneous application of multiple UV LED wavelengths in a flow-through reactor for inactivating E. coli in tap water. Conducted at a flow rate of 1 Liter per Minute (LPM), the research departs from conventional single-wavelength UV disinfection by employing a multi-wavelength strategy. The experimental setup consisted of UV LED reactors, each emitting light at specific and simultaneous wavelengths. This configuration allows for an in-depth examination of the combined effects of different UV wavelengths on E. coli inactivation. The comparative analysis of simultaneous irradiation using combined LED wavelengths (specifically LED280/300) against the theoretical summation of separate LED wavelengths demonstrates a significantly higher inactivation rate. This multi-wavelength approach shows a 1.7-log synergy in inactivating E. coli, a substantial enhancement compared to the less than 1-log inactivation achieved by the individual 280 nm or 300 nm LEDs. The combined LED280/300 method achieved nearly 99.9% disinfection. These findings show the increased efficiency of using combined UV LED wavelengths in water disinfection. The synergy in inactivation observed can be attributed to the concurrent activation of multiple inactivation pathways encompassing nucleic acid damage and protein-based mechanisms, presenting a new approach to microbial inactivation rather than methods that rely on a singular pathway. The integration of these mechanisms highlights the multiwavelength potential to achieve enhanced disinfection outcomes. These results pave the way for UV LED disinfection technology innovations, potentially improving public health and environmental safety.

Co-Authors: Sitao Liu, Cheng Tan, Xuejun Yu

Reductive water treatment using hydrated electrons is a promising technology to destruct perfluoroalkyl substances (PFAS). We developed a chemical-free vacuum UV (VUV) water photolysis system for reductive destruction of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). The new treatment platform drives VUV photons to directly photolyze water into hydrated electrons. The system achieved nearly complete defluorination of both PFOA and PFOS. The PFAS degradation kinetics was fast across a wide range of pHs. The presence of salinity and other background ions in the PFAS-impacted water matrix had a promotive effects on PFAS defluorination. This novel chemical-free VUV water ionization systems also significantly reduced energy consumption for PFAS treatment in comparison to other traditional UV-based PFAS options. Recent development on this VUV technology application for PFAS treatment will be discussed in the presentation.

Co-Authors: Annelies Aerssens, Mieke Flour, Silke Ternest, Leen Van Simaey, Duncan Verstraeten, Alain Kalmar, Isabel Leroux-Roels, Philip Meuleman, Piet Cools

Introduction
A variety of methods is available to ensure adequate disinfection of medical instruments. Despite the existence of many reprocessing guidelines, there are still remaining challenges such as error prone manual disinfection. We aimed to explore whether the application of ultraviolet C (UVC)-light emitting diodes (LEDs) as an alternative disinfection technology might provide an answer to some of these challenges for certain medical instruments.

Methods
The functionality of a UVC-LED device, the ZAPARAY RAY-ONE prototype 0/102, was validated using a petri dish with a 10 µL droplet containing S. aureus ATCC 25923 which was exposed to a 5-minute disinfection cycle (equivalent to approximately 118.5 mJ/cm2). An untreated control was prepared in parallel. Bacteria were collected and quantified to determine the log reduction. Medical instruments were identified through surveys conducted in a Belgian hospital of which a selection was subjected to microbiological testing.

Results
The device’s functionality was confirmed by demonstrating a more than 9 log10 reduction on a petri dish. The medical instruments tested were hand and angle pieces, orthodontic pliers, nasal sensors, disposable laryngoscope blades and external ultrasound transducers. The level of disinfection, using an instrument-specific protocol, varied from no to complete bacterial reduction depending on the instrument.

Conclusion
We demonstrated that the UVC-LED device has high disinfecting ability on a petri dish. The results obtained on medical instruments showed that the shape and desired level of disinfection of the instrument should be considered when using UVC-LED as an alternative disinfection technology.

Co-Authors: none

New measurements of photochemical ozone generation by 222nm in large rooms require a fresh look at the ozone generation mechanisms of Far UVC lamps and the implications for real world applications. Although the absorption of 222nm in air is very small, and the ozone generation cross section is very small compared to shorter wavelengths, especially below 200nm, the resulting concentrations of ozone in a room can reach levels that need further considerations. Analysis of the generation process and a application model will be presented. The ozone generation of Far UV-C lamps depends on the power of the lamp, the light distribution and the room size.

Various, established ozone reduction mechanisms have been taken into account to calculate real world estimates of expected concentrations in rooms. Calculated concentrations are being compared to measurements.

The simulation and measurement results indicate that although ozone concentrations in room settings are higher than previously estimated, the real world ozone concentrations will stay well below FDA guidelines.

Co-Authors: Housyn Mahmoud, Aakash Sharma, Ankit Patras

Microbiological cross-contamination has been a contributing factor to several well-documented outbreaks of foodborne illness worldwide. The airborne bacteria transmission relies on the ability of pathogens to survive aerosol transport and settle on food contact surfaces. The suspensions of microscopic solid or liquid particles in the air are defined as ‘bioaerosols’. To strengthen preventive measures against food re-contamination by microorganisms via bioaerosols generated during food processing, food industry is interested in the adoption of additional disinfection approaches other than regular sanitation procedures. This study aims to investigate the effectiveness of UV-C LED devices ( 279 nm peak wavelength) on aerosolized bacterial inactivation. We designed and developed a UV-C disinfection system for bioaerosol treatment. The chamber's shape, size, and internal structure was engineered to ensure that all bioaerosols get adequate UV-C exposure. A nebulizer and an impinger were connected to the system at the inlet and outlet of the system. A forced air system was also connected to ensure that all bioaerosols pass through the UV exposure zone. Preliminary experiments were conducted using Escherichia coli (ATCC 25922) as bioaerosol. Bioaerosols were generated in a Blaustein Atomizing Module nebulizer (BLAM) at 20 psi and passed through the UV-C chamber at a flow rate ranging from 1 meter per second. The bioaerosols were collected in a liquid impinger, after which samples were taken for serial dilution and analyzed using classical platting technique on TSA plates. 3 log10 reduction of Escherichia coli aerosols were observed in preliminary trials. Due to the poor recovery of bioaerosols, we predict total UV-C fluence of > 10 mJ/cm2. Further laboratory studies are needed to further validate the effectiveness of UV-C air disinfection with enhanced recoveries.

Co-Authors: De Palma I., Amodeo D., Manzi P., Puccio A., Nante N., Barcaccia M., Marini D., Pietrella D., Cevenini G., Messina G.

Introduction
Surfaces disinfection in hospital is essential to prevent the transmission of pathogens. This study investigates the efficacy of violet-blue light (VBL) at 405 nm, emitted by LED ceiling lamps, in disinfecting high-touch surfaces (HTS) and methicillin-resistant Staphylococcus aureus (MRSA)-contaminated surfaces in a Hospital Laboratory in Perugia (Italy).

Materials and methods
The study was carried out using 3 ceiling lamps, equipped with Luminus SST-10-UV VBL LEDs. Microbial sampling of HTS was performed before and after continuous 18-hour daily exposure to VBL for 7 days, using RODAC plates incubated at 37 and 22°C. Additional experiments were carried out on plastic and steel surfaces, contaminated with an MRSA isolate. Statistical analysis was performed using Stata 17 software, choosing a 95% significance level (p<0.05).

Results
The energy dose ranged from 9.7 (the sink) to 64.8 J/cm2 (the incubator handle). Results showed consistent microbial reduction in percentages and Colony Forming Unit: i) desk and keyboards with reductions of 78% and 86%, respectively, remained constant until the final sampling (87 % and 90%); ii) incubator handle: low microbial load with no growth post-irradiation.

On MRSA-contaminated surfaces, VBL significantly inactivated microbial load with greater reductions on steel than on plastic. Percentage reductions compared to covered controls were: 92% on the computer keyboard, 94% on the worktable and 98% on the laboratory sink.

Conclusion
LEDs emitting VBL at 405 nm were effective in reducing microbial contamination on various surfaces. This method shows potential for implementation in healthcare facilities, with further optimisation and integration into recommended infection control practices.

Co-Authors: Gabe Arnold, Margaret Axelson, and Eduardo Rodriguez-Feo Bermudez

The U.S. Department of Energy (DOE) launched the CALiPER program in 2006 to address a need for unbiased, trusted performance information for solid-state lighting (SSL) products, including those incorporating LED emitters. DOE testing and analysis, conducted by qualified test labs using industry-approved test procedures, helped to encourage high-quality products and discourage inflated performance claims. Early CALiPER testing also contributed fundamentally to the development of standardized photometric test methods specifically for SSL and the associated accreditation of testing laboratories.

The COVID-19 pandemic led to a similar environment for germicidal ultraviolet (GUV) products, where unsubstantiated performance claims proliferate, new technologies and test methods are in development, and the capabilities of commercial test laboratories are limited. In response, and further motivated by the desire to improve resilience to any future pandemics, the CALiPER program recently expanded its scope to include GUV products used to treat air and surfaces in occupiable spaces. Results from the first round of GUV product testing were published in September 2023, and can be found at https://www.energy.gov/eere/ssl/caliper.

This presentation will share key findings from Round 2 of GUV product testing, which focused on electrical and radiometric characteristics of upper-room luminaires. Products of this type are designed to safely treat occupied spaces by irradiating the volume above occupants. Eight wall-mounted luminaires rated to produce UV-C were tested, five using low-pressure mercury lamps and three using LED technology. UV-C radiant intensity distribution was measured far-field using a mirrored gonioradiometer, and spectral distribution in the 200–400 nm range was measured in the direction of maximum intensity. Performance claims were compared with measurements taken after 0, 100, and 500 hours of operation.

Co-Authors: Sean. A. MacIsaac, Graham. A. Gagnon

The application of germicidal UV in the field of drinking water and wastewater has been used for years for conventional UV sources and is becoming more feasible for LED sources. The practical use of UV advanced oxidation processes (AOPs) has been demonstrated to have great potential for degrading organic compounds fo concern. UV-LEDs have had little published use as an AOP source but could serve as a useful technology due to a more convenient design, stable power and wavelength output, efficient conversion of energy and flexibility when designing new reactors . This work characterizes a new UV-LED bench-scale instrument which enables UV LED AOP work at the bench scale while simultaneously improving sample throughput by two orders of magnitude when compared to the typical collimated beam setup. The instrument was characterized by using a selection of probe compounds to quantify the kinetics of degradation when using 280nm-based AOPs. Additionally, hydrogen peroxide and chlorine were used in conjunction with the UV LED source to provide a broad range of AOPs. The probe compounds used in this study were caffeine, 4-chlorobenzoic acid (pCBA), tryptophan, tyrosine, and sorbitol. The power output, influent flow, and flow cell style (turbulent or laminar) were also factors in this study to fully understand the capabilities UV LED AOPs.

Co-Authors: None

Operating junction temperature is a critical parameter for UV LEDs, especially expensive UV-C LEDs. GUV product designers must ensure their LEDs are operating near the designed junction temperature. Otherwise the emitted power may be below or above the intended value.

Too little power and the product may not meet its specifications, too much and it is likely overdesigned and more expensive than it needs to be.

Junction temperature can be assessed using simple thermal resistance calculations, but this technique can be difficult to implement, especially in dense arrays, and the resulting temperature may be off by 10 degrees or more -- enough to impact emitted power by several percent.

This paper discusses a technique for assessing junction temperature more accurately, in-situ, using the JEDEC Electrical Test Method (ETM). The equipment needed is presented, along with example calculations for a typical GUV product.

Co-Authors: Greg McKee, Labsphere Inc, gmckee@labsphere.com

UV-C LEDs are highly temperature sensitive. A 10 C increase in operating temperature drops power output by 3 to 4%, and it shifts wavelength up, reducing germicidal efficacy. This unfortunate reality must be considered by GUV lighting designers when using and specifying LEDs, to ensure that product performance specifications will be met, and also to optimize their products to be commercially competitive.

Traditional LED test methods, based upon long test pulses that heat the LED, were adequate for general-illumination LEDs, but when used with UV-C LEDS, their measurement uncertainty can force designers to include an unacceptable design margin in order to guarantee the product will always meet specifications.

This paper discusses a new LED test method, based upon the IES LM-92 testing standard, that produces accurate measurements -- correlated to temperature. A measurement system based upon this method is presented, along with example measurements that illustrate how designers can tailor electrical and radiometric measurements to produce cost-effective GUV designs.

Co-Authors: Shigeharu Yamauchi, Takeshi Tanaka, Menno Schake, Masaaki Tsunano

Since the corona pandemic began in 2019, ultraviolet LED technology has attracted worldwide attention, especially for wavelengths 280nm and below, known as UV-C. Its properties in killing germs have been widely accepted, and many research and development departments continue to focus on this topic. Now, the usage of UV LEDs allows the creation of new applications and offers the potential of existing applications to be revolutionized.

Central to this effort is the successful technological advancement and understanding of the underlying technology and mode of action of appropriate UV radiation for germicide and pest control is central to this effort. Essential basic steps have been taken and for some applications the performance of the available components is already sufficient.

Looking at the entire range of ultraviolet radiation, from UV-A to UV-C, existing light sources, containing mercury, are still widely used in many applications. These light sources are either exempted from the global regulation to eliminate mercury or are given a longer grace period. Nichia Europe’s Mr. Jonatan Klee plans to discuss these exemptions for mercury-based solutions and the necessary technological advancements for UV LEDs to achieve the goal of eliminating mercury to the greatest extent possible. In addition to the pure performance of the component, aspects of technical integration in modules and systems, scientific understanding of how UV radiation works, and cost aspects are also critical.

The advantages of implementing LED based solutions in areas where mercury-based solutions are currently still used will be demonstrated using specific examples. A key advantage, in addition to the reduction in mercury content, is the potential energy savings and reduction in maintenance costs due to the potentially longer lifetimes of the light source. The current technological status, and the foreseeable further performance developments, will be explained.

Co-Authors: Jennifer N. Dootz, Kirsten H. Parratt, Stephanie L. Servetas, Monique E. Hunter, Nancy J. Lin

Confidence in measurements of microbial inactivation after germicidal UV (GUV) treatment is crucial for decision making regarding indoor air quality and surface disinfection. This confidence is attainable through rigorous protocol evaluation by the assessment of sources and types of error, repeatability and robustness, by the use of orthogonal characterization techniques to provide new or complementary information, and by the application of robust statistical tools. The results of this measurement assurance process provide quality data for the GUV stakeholder community.

In this work, we apply the principles of measurement assurance to better characterize the microbial samples to support interpretation of GUV surface inactivation results. The ASHRAE SPC 185.4 draft standard, “Method of Test Method of Testing In‐Room Ultraviolet Devices and Systems for Microbial Inactivation on Surfaces in a Test Room”, provides the use-case to demonstrate this approach. Generally, the only microbial quantification used in GUV or chemical inactivation is counting of colony forming units (CFU) of exposed microbes compared against unexposed. Here, we expand the microbial characterization portfolio. We provide values for total cell count, spore purity (%), and spore germination (%) for B. spizizenii (formerly B. subtilis subsp spizizenii) grown on tryptic soy agar (TSA) and sporulation agar (SA). These values provide important information on the spore viability and also presence of inert biomass on the sample carrier which may be taken into consideration when evaluating GUV inactivation data. Lastly, we map the 3D morphology of B. spizizenii on the carrier surface for evidence of cell stacking implicated in hindering GUV inactivation. These efforts only represent a portion of the work needed to ensure measurement quality, and future efforts focus on the reminder of the protocol looking at the relationship between cell processing and GUV inactivation.

Co-Authors: Samantha Meeker, Kim Langdon, Ann Mann, Rosemary Boettinger, Hailey Reel, Mike Rockwood, Caroline King, Hayden Nix,

Objective: We assessed the public acceptability of far-UVC light as a disinfection method in long-term care (LTC) facilities through participant recruitment for the Preventing Respiratory Viral Illness Invisibly (PRiVII) trial, a pragmatic cluster-randomized trial of far-UVC light in LTC homes. Given the pressing need for technologies to mitigate airborne and fomite disease transmission, far-UVC (200–230 nm) is increasingly recognized for its potential in continuously disinfecting occupied indoor spaces. This is possible because of far-UVC’s high efficacy at inactivating pathogens while remaining safe to occupants within accepted exposure guidelines. Understanding public opinion on the use of far-UVC and its safety is crucial for the effective implementation of this technology.

Methods: Consent discussions were conducted with residents and/or their substitute decision makers (SDMs) from three participating LTC homes for the PRiVII trial. Consent discussions require clear information given in lay terms about the use of far-UVC lamps as a disinfection method and any associated risks. Residents or their SDMs then approved or declined to participate. The number of individuals approached, declined, or approved consent was recorded, along with reasons for refusal.

Results: We approached 412 individuals for consent discussions regarding the PRiVII trial. Given the high burden of cognitive impairment in the LTC population, 75% of consent conversations were with SDMs (n=308). Of those approached, 14% declined (n=56). Reasons for refusal are detailed in the table. Five of the 56 individuals who declined expressed skepticism of far-UVC technology, which constitutes for 1% of all 412 individuals approached.

Conclusion: We found a high level of acceptability among those willing to hear about far-UVC technology’s risks and benefits, with only 1% of participants expressing skepticism. In our sample, no one chose not to hear us out. Here, reluctance to participate was largely unrelated to skepticism about far-UVC technology. Instead, it was associated with uncertainty about participating in any clinical trial, and concerns about the individual burden involved. Over against the assumption of public hesitancy toward far-UVC, it appears that informed individuals are more receptive to its use as a disinfection method.

Co-Authors: Keen O.S

The UV/H₂O₂ AOP is one of the multibarrier techniques for potable water and wastewater treatment. It involves partial degradation of categories of emerging pollutants that conventional technologies cannot manage. The hydrogen peroxide residual left over after treatment interferes with chlorine disinfection by reacting with chlorine. Because of the low molar absorptivity of H₂O₂, the amount of H₂O₂ needed for an efficient process is fairly high (commonly 2-10 mg/L). With only a small fraction (5-10%) consumed in the process, a non-trivialH₂O₂ residual remains after treatment that requires high chlorine demand after AOP. This project evaluates the quenching of H₂O₂ with Bayoxide iron oxide media column as compared to granular activated carbon (GAC) column at a pilot scale (1 gal/min flow rate per column). Iron oxide showed promise at bench scale for reducing the cost of H2O2 quenching by using less expensive medium that potentially requires less energy to run and has lower operation and maintenance cost. The pilot plant was constructed with two clear PVC columns (5 ft length, 0.5 ft diameter, 7.3 min empty bed contact time) filled with either GAC or granular iron oxide with sampling ports before and after each column and at intermediate points for monitoring H₂O₂ concentration. The pilot was housed at a local drinking water treatment plant, and filter effluent from the treatment plant with 10 mg/L of H₂O₂ added was used as influent for the columns. Pressure drop was monitored for the inlet and outlet of each column to determine backwash requirements. This presentation will show the results of the 5 months of the pilot operation.

Co-Authors: Kiran Ahlawat, Ramavtar Jangra, and Ram Prakash

Textile effluents are a significant industrial pollutant because they contain approximately 15% unfixed dyes, predominantly constituting 60-70% of azo dyes, which are being discharged into the environment. In this paper, the degradation of Reactive Black 5 (azo dye) has been performed by means of an environment friendly mercury free far UV-C excimer light source along with an advanced oxidation process (AOP) using TiO₂/H₂O₂. For this purpose, at first, a dielectric barrier discharge (DBD) plasma based 222 nm wavelength excimer lamp has been designed and developed, where a wire mesh is used as a ground electrode in a coaxial configuration of DBD geometry. The impact of different concentrations of TiO₂ loading, intensity of Excimer-UV light, initial concentration of dye, pH of the suspension, and addition of H₂O₂ are investigated for degradation of RB5 dye. The complete degradation has been achieved within 3 minutes in the case of Excimer-UV/H₂O₂, attributed to an abundance of hydroxyl radicals generated by the AOP. A more than 95% reduction in chemical oxygen demand (COD) value has been achieved in 40 minutes in the case of Excimer-UV/H₂O₂. The maximum energy yield reported in this study is 5712 mg/kWh. The COD and HR-MS analysis establish the removal of dye toxicity potential and chemical degradation pathway. A high degree of degradation is found in the alkaline medium. Since textile effluent is highly alkaline, this result is significant, as no neutralisation of the solution is required, and direct treatment is possible. The treated effluent was then utilized to study the reusability in the agriculture purpose, on the germination of radish seeds in soil. The treated water resulting from these separate treatments shows positive effects on radish seed germination and growth when compared to untreated dye wastewater.

Co-Authors: Katrina Fitzpatrick, Caitlyn Butler, Kelli Z. Hunsucker, Mariana Lanzarini-Lopes

Marine biofouling causes serious environmental problems and has adverse impacts on the maritime industry. Biofouling on windows and optical equipment reduces surface transparency, limiting their application for on-site monitoring or continuous measurement purposes. Among various strategies, irradiation of germicidal light (250-280 nm wavelengths) (UVC) is considered environmentally friendly and has been illustrated to successfully prevent marine biofilm formation at extremely low irradiance. However, it is nearly impossible to evenly distribute UV radiation across a window surface without damaging it. In this presentation, we will discuss a new technology, UV-emitting glass (UEG), that can glow UV light from the surface of interest to prevent the establishment and growth of biofilm. We were able to make UEGs that maintain a transparency of over 99% as measured by the naval research laboratory. The UEGs reduced visible biological growth by 98.29 % and resulted in a decrease of 1.79 log in detected cell-forming units when compared to the control during a 20 day submersion at Port Canaveral, Florida, United States. In addition, this technology decreases the energy consumption and maintenance required to upkeep these surfaces. These findings serve as strong evidence that UV-emitting glass is a technology with significant environmental impact and should continue to be studied and developed as a strategy for biofilm inhibition on transparent surfaces. We were able to identify the main areas where improvement is needed while providing redundant proof that UEGs have significant promise in preventing biofilm formation in marine environments.

Co-Authors: Manoj Singh, Acuva Technologies Inc.

Ingesting microbiologically contaminated water is among most common sickness routes. Ultraviolet radiation is the known to be the most effective water disinfection method, compared to chemical and filtration approaches. Ultraviolet light emitting diodes (UV-LEDs) based water treatment systems, unlike conventional mercury UV lamps-based systems, can be operated on DC voltage and low energy consumption, does not contain toxic mercury, and does not require frequent maintenance, and enables design of superior performance devices within more compact spaces for integration into wide range of applications.

Acuva Technologies has designed and commercialized wide range of water and air disinfection solutions based on its proprietary IntenseBeamTM technology, which is more efficient, effective, and distinct from other commercialized UV-LED products exist in the market. Here, I will present the advantages of Acuva’s unique approach in designing UV-LEDs water and air treatment system. The challenges and opportunities for UV-LED systems are presented and Acuva commercial products are presented. We show that UV-LED water and air disinfection systems operated on provide microbially safe drinking water and air from contaminated sources and meet the most stringent criteria that is typically not achievable by commercial products from conventional technologies. Finally, I will provide an overview on the future of UV-LED disinfection technologies and the scope of work that can help UV community to introduce this technology to wider range of applications and geographies.

Co-Authors: Mengkai Li*, Jiale Wang1, Xingjia Gao1, Zhimin Qiang

Ultraviolet (UV) light-emitting diode (UV-LED) has been regarded as an emerging UV light source for disinfection and photochemical oxidation in water and wastewater treatment. As compared to the conventional low-pressure (LP) mercury lamp, UV-LED has the merits of small size and various output wavelengths, which allow for more flexible light source layout and wavelength selection in the design of a reactor. A micro-fluorescent silica detector (MFSD, 0.7 mm3 volume) can capture photons uniformly from nearly all directions at a test point. This MFSD, fixed on a precise two-dimensional guideway, could directly measure the PFR distributions accurately in various types of UV reactors, such as LP reactor[2], medium-pressure UV lamp reactor[3], reactor with different inner-wall materials[4], and reactors with multiple lamps[5], exhibiting high stability, fast response, water resistance, and small size. This detector has great potential to be applied for the determination of optical field for UV-LED reactors. So we herein report the use of this MFSD to reveal the optical fields of commercial UV-LED reactors (Fig.1). The PFR distribution of a commercial UV-LED reactor filled with water with various UV transmittances were measured (Fig.2). The impact of water UVT and inner wall reflection were examined. The delivered UV dose could be calculated by using CFD software based on the measured PFR distribution, and validated by the biodosimetry with MS2 as the challenge micro-organism. The application of this reactor in tap water disinfection has been discussed and the main properties of UV-LED reactors were compared with those of conventional LP lamp reactors. This emerging reactor has been applied in the water supply disinfection in rural area and the disinfection performance has been evaluated for three months. This work provides significant results for the optimal design and high-efficacy operation of a UV-LED reactor.

Co-Authors: Mengkai Li*, Yanyan Huang, Zhimin Qiang

Micropollutants have attracted increasing attention because of their potential threat to aquatic ecosystem and public health. In 2022, China issued the Action Plan for Control of Emerging Contaminants that emphasizes the need to efficiently mitigate micropollutants in our environment. Ultraviolet-based advanced oxidation processes (UV-AOPs) have been regarded as effective approaches for micropollutant degradation, especially in China that dozens of drinking water treatments plants selected UV/H2O2 process to remove micropollutants. The efficiency of UV-AOPs is influenced by many factors such as water matrix, target micropollutants, and operating conditions (e.g., reagent dose). To optimize UV-AOPs, a significant number of experiments are required to identify the optimal process and operating conditions. These involve frequent field water collections/transportations, and a high level of professional skills for the operation of photoreactor and advanced analytical instruments, which are time-consuming, laborious, and expensive. Thus, it is crucial to develop a facilitated method for predicting the photon fluence-based rate constant of micropollutant degradation (k′p,MP) and the EEO values. This study developed a novel method, through combination of model simulation with portable measurement (MS-PM) [1], to facilitate the k′p,MP prediction in real waters in various UV-AOPs. Moreover, a scale up method of UV-AOPs was developed to predicted the EEO values based on the k′p,MP [2]. Portable measurement instruments for the scavenging capacities of principal reactive radicals (RRSCs) involved in UV-AOPs (HO^•, SO4^•-, and Cl^•) was conducted on a mini-fluidic photoreaction system (MFPS) [3]. Combined with the UV fluence monitoring based on the previously developed micro-fluorescent silica detectors, the operation monitoring and control of UV-AOPs to remove micropollutants could be conducted. This technology has been applied in a drinking water treatment plant in Zhejiang Province in China for half a year (Fig.1), which could obviously reduce the cost and ensure the reliability of the UV-AOPs.

Co-Authors: Ulli Hansen, Simon Maus, Xiaodong Hu

UVC-LEDs are gaining increasing importance in disinfection applications for water, surface and air disinfection. The efficiency and quality of such devices is developing quickly and due to small size, instant light emission and low power consumption these LEDs enable a large variety of new applications like e.g., point-of-use disinfection of drinking water in off-grid areas.

Past contributions have shown that the use of miniaturized mirror elements placed close to the LED can help to significantly increase light output and improve the thermal behavior of the packaged LED. This results from a large amount of the generated light being emitted over the LED die edges which can be recovered by these mirrors. UVC-LED modules with high power are either achieved by arranging many packaged LEDs in an array-format or by placing several LED chips into one package. The former requires a larger footprint, the latter has the drawback that the LEDs will – due to a large portion of side-emitted light - heat each other making the module less efficient.

We propose a novel solution using integrated mirror arrays to enable very efficient multi-chip packages with each LED optically insulated from the others for optimal optical performance. This approach can accomplish high-power modules by placing several UVC-LEDs in the package. By using cost-efficient low-power Mini-LEDs a high-power module with improved cost/power ratio (factor 0.5) can be achieved. This paper will describe such a cost-efficient ultra-high power multi-die UVC-LED module based on an 6x6 array of low-power (10-15mW) Mini-LEDs.

Co-Authors: Brock Emerson

Researchers and water municipalities alike are reaping the benefits of piloting all forms of water treatment – including UV. Whether the focus is UV disinfection, AOP applications, industrial, or a comparison of multiple UV systems and/or technologies, piloting provides the meaningful data needed to enable educated decisions on the future deployment of UV water treatment.

This presentation will include an overview of piloting best practices as they specifically apply to UV piloting. Several case studies of UV pilots done by small and large municipalities will offer a snapshot of the current state of UV piloting including lessons learned in each case and special considerations that must be taken to ensure a successful UV pilot.

The presentation will conclude with a challenge to the UV industry on the future of UV piloting. As UV piloting has grown in popularity, a gap in controls and system size has become evident. Parameters surrounding UV systems – flowrate, UVT, water temp, etc – are all easily observed and collected, however there are no pilot-sized systems that offer the same detailed controls available in full-scale municipal systems. This leaves researchers with imperfect options – they either get limited data from a small system or face the challenge and costs of ‘piloting’ a full-scale system. This leads to decision makers not having the best data to make informed decisions with. Given the hope of the industry to expand UV technology, enabling better testing of it would be beneficial to not only the industry, but humanity at large.

Co-Authors: Mariana Lopes

There is growing interest in using germicidal ultraviolet (UV) radiation light-emitting diodes (LEDs) for surface disinfection and biofilm prevention. UV radiation prevents bacterial attachment, growth, and biofilm formation on wetted surfaces of tight channels, such as those found in point-of-use plumbing, water treatment devices and medical equipment. Although the approach of delivering UV irradiation for (A) biofilm prevention and (B) surface disinfection may be similar, there are distinct differences in (1) definition, (2) inactivation mechanism and (3) minimum irradiance needed depending on the extent of disinfection needed and maturity of a biofilm. Our group is currently tackling these two scenarios in two different studies, where we have explored the use of UV-C side-emitting optical fibers to inactivate surface-bound bacteria inside a tight channel and to prevent biofilm formation inside a flow-through channel. This presentation will discuss three important questions related to surface-bound and biofilm-attached bacterial inactivation including: (1) Difference in characteristics of surface-bound bacteria and a biofilm layer (2) UV irradiance (μW/cm2) required for surface-bound and biofilm-attached bacterial inactivation (3) how hydraulics (flow rate (ml/min)) of a reactor affect the efficacy of UV inactivation for biofilm attached bacteria.

Co-Authors: Earnest Blatchley Ph.D., Phil Arnold, Ashley Fry, Maria Topete, William Palmer, Patrick Piper, Ling Zhou Ph.D., Ilan Arvelo Ph.D.

This presentation introduces the development of a UV-sensitive DNA-tagged aerosol tracer designed for real-world applications, specifically targeting the assessment of Equivalent Air Changes per Hour (eACH) that ultraviolet fixtures provide, in diverse environments. As the importance of indoor air quality gains prominence, understanding the efficacy of UV fixtures as additive air purification systems becomes critical. The DNA-tagged aerosol tracer offers a unique solution by enabling precise measurement and evaluation of the impact of UV fixtures on eACH.

By employing a UV-sensitive aerosol, we can track the dispersion and degradation dynamics in real-world scenarios, providing a comprehensive assessment of supplemental ventilation efficiency, provided by UV fixtures. The versatility of this tracer allows for application in various settings in the built environment in general. The presentation will delve into the methodology behind the tracer's development, and highlight the resulting data from our forthcoming publication, that sheds light on the contribution of UV fixtures to overall air quality improvement and the tracer’s correlation with bacteriophage MS2, a gold standard in airborne pathogen surrogates. The findings presented contribute to the ongoing scientific discourse on the role of UV fixtures in achieving healthier, safer environments.

Co-Authors: None

The first municipal scale deployment of UV-C LED technology was by United Utilities (UK) in 2019. The system designed and manufactured by Typhon Treatment (UK) was also 3rd party validated in accordance with the 2006 USEPA UV Disinfection Guidance Manual. Ultimately six systems were installed with a total flow rate of around 28 MLD (~5,000 USGPM). This proved the engineering/technical viability of mercury-free UV LED lamp technology at municipal scale. However, even with this installation in operation for over 4 years, it’s fair to say that opinions remain varied on the commercial viability and hence wider scale adoption of this technology.

The variation of opinions is largely centered on whether it’s possible to overcome the barriers of relatively high-cost/low-efficiency LED devices, i.e. is it possible for a sub-5% efficient UV light-source to be incorporated in a commercially viable treatment system, when there are 15% to 35% efficient UV light-sources available? This paper will reference technical data from publications demonstrating both viability and non-viability of UV LED technology deployment.

This paper will further discuss the broader elements of; mid/long term supply chain security implications, regulations considerations and technical limitations.

Finally, this paper will give an overview of some case studies of UV LED technology projects currently deployed in municipal applications. It will provide application goals and performance results. It will also outline the challenges and advantages in comparison to conventional mercury-vapor lamp technology. The case studies include:

United Utilities
Municipal Drinking Water, United Kingdom
28 MLD (5,072 USGPM)

Southern Nevada Water/Las Vegas Valley Water
Municipal Drinking Water, USA
6 installations with flow rates 315 m3/hr to 1,500 m3/hr

HDR
Potable Reuse. Maryland, USA
Goal to improve long-term water supply resiliency & water quality using UV Disinfection with comparison of conventional and LED UV technology

University of Colorado at Boulder Mobile Trailer, USA
Compare LP UV & UV LED system for disinfection of pathogens and viruses.
Operate as an AOP by injecting either hydrogen peroxide (H2O2) or free chlorine into the water upstream of the UV unit

Halifax Water / Dalhousie University
Wastewater Discharge. Nova Scotia, Canada
To compare existing LP UV system with LED UV system

Co-Authors: Laith Furatian, Anthony Pimentel

AOP reactors are designed by the system manufacturers based on the water quality, and only some of the designs take into account hydroxyl radical scavenging by the water matrix. One of the major reasons is the lack of a standard protocol for measuring scavenging. Scavenging is inversely proportional to the steady-state concentration of hydroxyl radicals. So, in situations where steady-state conditions can be assumed, when scavenging is, for example, 4 times lower than what the system is designed for, the concentration of HO• is 4 times higher. The observed first-order reaction rate constant with which a target compound reacts with hydroxyl radicals will be 4 times higher as the result, and the UV dose it will take to achieve a desired log removal will be 4 times lower. Consequently, the wasted energy could be as high as 75%.

This presentation will report the efforts of the IUVA Task Force to establish a standard protocol to measure scavenging of hydroxyl radicals by the water matrix. The draft protocol has been developed by the task force co-chairs and reviewed and vetted by the Task Force members consisting of researchers, consultants and representatives of AOP reactor manufacturers. A spreadsheet was developed for easy implementation to minimize the errors by individual users. We will present an overview of the protocol method, potential challenges and limitations, and how interested parties can access the protocol. We will also discuss the next stage of the protocol development involving experimental validation.

Co-Authors: Cody W. Haag, George Holliday, Kenneth Archulet, Weiming Tang, P.K. Swain

UV-C room disinfection devices have known physical limitations, including reduced efficacy on distant, angled, and shadowed surfaces. Competing placement strategies employed by commercial room disinfection devices may be more or less inhibited by these factors; however, there are limited data for direct comparison. In a community hospital setting, an experiment was conducted to measure the UV-C dosage of competing placement strategies in various challenge environments, including a patient room, an operating room, and an emergency room. Ten commercially available dosimeters were placed in a grid-like formation throughout the challenge environments. The UV-C emitter placements’ distance, angle, and exposure to the dosimeters were measured. Room temperature and humidity were recorded as factors that may impact UV-C irradiance. A modified remote-controlled UV-C emitter (254 nm) was used for each of the competing placement strategies, including whole-room, spot, and autonomous strategies. The primary outcome was the mean UV-C dose of a triplicate 10-minute disinfection cycle for each placement strategy. A secondary outcome measured the dosage difference of a commercially-available autonomous device and the modified emitter autonomous placement. The autonomous strategy was less inhibited by the known physical limits of UV-C irradiance, thus achieved a significantly higher UV-C dose compared to the whole-room and spot strategies. Second, the commercially-available autonomous UV-C emitter provided similar doses to the modified UV-C emitter’s autonomous strategy, therefore the modified emitter was likely an appropriate analog for commercially-available autonomous UV-C devices. Author’s note: An earlier version of this study was published online in Infection Control and Hospital Epidemiology titled “Comparing UV-C dosages of emitter placement strategies in a community hospital setting” on December 16, 2022, available at: https://www.cambridge.org/core/journals/infection-control-and-hospital-epidemiology/article/abs/comparing-uvc-dosages-of-emitter-placement-strategies-in-a-community-hospital-setting/33E358712EE7280E492ECE43829114E9.

Co-Authors: Miles Bengtson, Pao Chen, Saya Han and Peter Chung

UV LED technology has come a long way over the past decade, gaining popularity in a variety of commercial applications. While curing, disinfection, and food processing applications dominate the industrial product space, unique applications in spectroscopy and space-related projects are securing ground as well.

With the emergence of new applications, there is a need for advanced simulation and modeling capabilities which can aid in cost-reduction at the design stage. In this paper, we will showcase the design and development of a high-intensity UVLED array for application in a terrestrial simulation of the space electron flux environment. LED light sources with energies in the UVA range and photocathodes with a low work function coating were used to create the electron beam. A non-sequential ray-tracing simulation was conducted using Zemax® software and a model was developed, incorporating the material characteristics of the electron gun. Beam shaping lenses were used to achieve targeted irradiance and uniformity on the specific detector areas.

Design optimization results suggested the use of 14x custom-designed, chip-on-board LED arrays with 64x 365 nm LEDs each to achieve a target flux of 0.1W/cm2. Optically boosted, thermally enhanced UVA LEDs were used for the project. The UV LED array was manufactured, and initial characterization was performed in the Air Force Research Laboratory. Several challenges related to thermal dissipation were identified for consideration during the design of the next version.

Co-Authors: Jonathan Mann; James Grandusky; Patrick Aigeldinger

UVC LEDs are gaining traction in point-of-use and point-of-entry water disinfection as they offer efficient, sustainable, and maintenance-free operation at an optimal germicidal output of 265 nm. Designing for disinfection applications with UVC LEDs requires an understanding of the relationships between wavelength, dose, irradiance, exposure time, and system materials. Characterization of output power, wall plug efficiency and lifetime of a population of UVC LEDs provides system designers with the critical parameters that influence their end product performance.

Industry typically discusses lifetime in terms of LXXBXX, where L is the percentage of power remaining after a given timeframe, and B is the percentage of devices within a population retaining this percentage of power. Most current standards consider L70 based on visible lighting, where people will notice a drop in output power greater than 30%, and B50 implying that a failure rate of 50% is acceptable. However, in UVC disinfection applications these characteristics are more nuanced and highly depended on the application and system design.

Approaching requirements for UVC LED lifetime in terms of what is needed for system performance at end of life provides a more realistic methodology. In point-of-use water disinfection, the use case demands a high level of reliability for a short number of hours. These applications typically only need between 250 to 500 hours of LED-on time throughout the life of the water dispenser: at two liters per minute, this adds up to between 30,000 and 60,000 liters, which is anywhere from one to ten years of use.

In this discussion we will look at multi-LED system and how an L70 failure rate of a single LED is tempered by the remaining output power of that LED and by the power of the remaining LEDs within the full system. We will also look from system designer point of view of better understanding tradeoffs by using the system failure rate at 300 hours rather than a standard specification of L70B50 at a arbitrary figure.

Co-Authors: none

AlGaN-based Deep UV (DUV) LEDs with peak emission wavelengths shorter than 365 nm emerged as enabling technology for diverse applications in military, national security, industrial and commercial applications. Major impact on the development of DUV LEDs had two major DARPA programs: Semiconductor Ultraviolet Optical Sources (SUVOS, 2005-2008, J. Carrano) and Compact Mid-Ultraviolet Technology (CMUVT, 2011-2013, J. Albrecht). Programs focused development of the core DUV LED technology and DUV LED-based sensors for detection of weaponized bio-agents and harmful pathogens (combination of UV-C and UV-B), and covert Non-Line-of-Sight communications (NLOS) in solar-blind spectral range (UV-C).

First commercial applications of DUV LED-based products included scientific instrumentation, UV spectroscopy, sensors, medical, bio-medical devices, horticulture. Niche applications emerged for military and space flight equipment. In parallel, significant efforts focused on UV-C LEDs for water, air and surface disinfection with wide variety of products entering marketplace. We will review main areas and sample applications of DUV LEDs besides disinfection.

Co-Authors: Jennifer Pagán, Ph.D.

The use of UV-C LED reactors for municipal-scale photolytic water treatment is now firmly underway with installations by early adopters receiving clearance for active discharge (Las Vegas, Nevada; Halifax, Nova Scotia). UV sensing is a critical part of the operational assurance and performance validation of such systems, which are often deployed to protect human health (e.g. drinking water disinfection) or the environment (e.g. wastewater treatment).

The reality of full-scale UV-C LED systems has been long debated, though the rate of progress of regulatory development has been inadequate in comparison to the rate of technological development; therefore, systems have emerged prior to the establishment of widespread and accepted governing principles.

One area in particular which requires attention is the method for appropriate monitoring of the UV output from a UV-C LED array and how these needs differ from those of a conventional UV system (either single or multi-lamp). National regulations for conventional systems can include prescriptive guidance on the design and placement of UV sensing elements; where adaptations are being sought (e.g. DINoLED in Germany) care must be taken to adapt requirements in a way that considers the differences in design and need of an LED system. Through system deployment AquiSense has generated a dataset of large LED array characteristics that may be used to inform regulations and guidelines. This paper shall present our understanding of UV-C LED array emissions, the status of current efforts to describe and standardise monitoring of such arrays, and an analysis of the mathematics by which sensor observation of such arrays are described.

Co-Authors: Jennifer Pagán, Ph.D., Oliver Lawal

UV-C LED technology has sustained rapid development since its emergence in 2003, though this has not been a linear process. With nearly 2 decades of device evolution, it is possible to trace macroscopic trends in the technology, highlighting areas of focus and the factors driving them. This retrospective approach provides context for predictions of wider trends in future characteristics, performance, and pricing.

Expanding on previous discussions on this topic, a summary of performance benchmarking shall be provided for UV LEDs; notably, cutting edge devices newly released to the market at time of presentation shall be included in this analysis.

This presentation will provide a view of the UV-C LED device and systems market from a system manufacturer perspective. The intent is to state plainly, and without hyperbole, what is visible to an active player in UV-C LED technology and to provide a point of reference for wider industry professionals and policy makers.

Co-Authors: None

I will present a summary of the extensive semi-structured expert interview process that Blueprint is undertaking, and our preliminary conclusions on a roadmap for a future role of far-UVC to prevent future pandemics. I will also describe the research that Blueprint Biosecurity has already commissioned, including funding eye safety studies and efficacy modelling, and our plans for the future.

We are still writing the roadmap, but will be tying together the threads of different research, from efficacy to skin and eye safety to air chemistry and the regulatory landscape, to identify the biggest scientific challenges that need to be addressed through industry innovation and future research. We will also describe the role Blueprint Biosecurity intends to play as a facilitator and funder to accelerate technical and scientific progress in the field.

As we are still writing the roadmap, there are a number of potential areas in which we could highlight our technical findings. One example of this would be identification of ozone mitigation strategies, including various potential ozone removal technologies. I cannot commit today as to which area we think is the most important to highlight to the audience, but it would be our intention to describe at least one challenge in scientific detail.

Co-Authors: Bailey Reid, Amina Stoddart, Graham Gagnon

Drinking water and wastewater treatment facilities rely on disinfection treatment systems to provide properly treated water for drinking and reuse respectively. An emerging treatment option for disinfection processes is using UV LEDs instead of conventional mercury ballasted UV sources. This project explores the feasibility of UV LEDs as an appropriate technique for full-scale wastewater disinfection. A 280nm, 100 gpm closed-channel UV LED reactor was installed in a wastewater facility in Atlantic Canada. The disinfection performance of the instrument was assessed using UV auditing pre and post installation in the wastewater facility. UV auditing was done by comparing collimated beam dosimetry with twice weekly full-scale sampling to assess the performance of UV LEDs compared to conventional UV disinfection. Pre-installation data clearly indicated that UV LEDs perform comparatively to conventional UV sources and is in alignment with previously published work from Dalhousie. Establishing the boundaries of flow, UV transmittance, and water quality where UV LEDs perform similarly to conventional systems is a key outcome of this work and will help utilities in their decision making when retrofitting and upgrading facilities. The elimination of mercury from full-scale systems is a potential environmental boon in terms of improving the inherent safety and One Water performance. Additional outcomes from this project will help quantify these benefits and assess best practices for using UV LEDs across several magnitudes of flow.

Co-Authors: W. Travis Horton, Jon Douglas, Holger Claus, Brian Stern, Laura Callahan, Ernest R. Blatchley III

The development of Far UV-C technology has opened up the possibility of implementing “whole-room” UVGI systems. This is because the current exposure limits for Far UV-C radiation are significantly higher than those for longer wavelengths. However, to date only limited information exists to quantify the effects of Far UV-C radiation on airborne viruses. Moreover, methods for testing and validation of upper-room and whole-room UVGI fixtures are still evolving.

To address these issues, a study was initiated to develop and implement a test method to quantify the performance of Far UV-C systems for inactivation of airborne, viral challenge agents, to assess the safety of these systems in terms of human exposure to Far UV-C radiation, and to examine ozone dynamics. The experiments involve Far UV-C lamp fixtures that have been installed in an indoor air quality (IAQ) chamber (volume = 55 m3) located within the Ray W. Herrick Laboratories at Purdue University. The experiments are conducted under well-mixed conditions, which have been verified using CO2 tracer experiments. Viral challenge agents used in these experiments include the phages T1, MS2, and 6, which span a range of viral types and sensitivities to Far UV-C radiation. The fluence rate field delivered by the Far UV-C lamp fixtures has been quantified by spherical actinometry; the results of these measurements have been compared with numerical simulations based on ray tracing. Ozone dynamics were measured and compared with predictions of a mathematical model. Collectively, the results of these experiments and simulations allow translation of the results of this work from the test environment to the application environment, which represents a critical feature of any testing and validation scheme.

Co-Authors: Sei Rim Kim, Zhenhui Jin, Caden Eagler, Zhihu Liang, Yi-Cheng Wang

The ongoing challenge of ensuring the safety of fresh produce is highlighted by the frequent occurrence of multi-state foodborne illness outbreaks each year, leading to significant human suffering and economic losses. While several approaches to decontaminating fresh produce have been proposed, many are constrained by concerns related to human health, environmental impact, and the high consumption of energy and associated costs. Light-based techniques, particularly UV light, have emerged as a promising alternative. In contrast to conventional UVC-based light, far UV-C light at 222 nm is less harmful to human exposure while maintaining its effectiveness in inactivating bacteria and viruses. This offers a unique opportunity to develop a flexible and innovative decontamination process. In this study, we introduce cases for decontaminating various foodborne pathogens using far-UVC microplasma lamps. We have devised a compact far-UVC irradiation system that demonstrates highly effective antimicrobial activity against bacteria and viruses, resulting in a reduction of pathogen count by at least 4log10. We have integrated a series of 222 nm far-UVC microplasma lamps into a module reactor to ensure uniform and optimal disinfection performance under varying treatment conditions.

Our research focuses on investigating the inactivation efficacy of target pathogens such as E. coli O157:H7 and L. monocytogenes using the 222 nm wavelength within specific processing timeframes within the reactor. We will present optimized far-UVC disinfection parameters suitable for various fresh produce and raw samples. Additionally, we will assess the impact of repeated treatments or specific wavelength dosages on food quality and the degradation of packaging materials.

Co-Authors: NA

Anne Arundel County (AACo) is currently operating the first indirect potable reuse pilot for managed aquifer recharge in the state of Maryland, operating at flows between 2- 10gpm. UV disinfection is a critical part of the overall pathogen reduction approach to achieve 12-10-10 reduction of virus, crypto, and giardia (V/C/G) consistent with CA reuse goals. More specifically, the UV system is being run at REF254nm 186mJ/cm2 to contribute 4-6-6 reduction of V/C/G. Despite the global prevalence of UV treatment, conventional mercury-UV technology has significant drawbacks including the inability to dose-pace at the small flows typical to pilot facilities.

In response to these drawbacks, AACo is piloting the first UV system capable of dose-pacing at pilot-scale made possible by light emitting diode (UVLED) technology. UVLEDs are gaining popularity in the water industry due to their reduced environmental impact, robust design, and flexible operation. UVLEDs contains no mercury, require no start-up time, and can be turned on and off frequently without negatively impacting lamps’ lifetime or performance. This study compared the mercury UV and UVLED reactors from a disinfection, scalability, cost savings, and operability perspective.

This presentation will discuss findings from this UV pilot research being conducted at the AACo Patuxent Water Treatment Facility. This includes testing the UVLED device at fluences ranging from 40-2000 mJ/cm2 under both disinfection and UVAOP scenarios, comparisons in cost and power consumption, considerations for operators, and implications for scale-up as the County approaches demonstration scale of 0.5MGD.

Co-Authors: Dylan Gleason; Vladimir Popović

A custom-built ultraviolet (UV) light conveyor system was developed to the treatment of grains and solid food samples in pilot scale. The system was designed to support four sets of interchangeable panels with mounted UV lights that are available commercially or under development: low-pressure mercury (LPM) lamps, medium-pressure mercury (MPM) lamps, UV-LEDs, and a novel phosphor pulsed light (PL) lamp. Samples were placed on a UV-permeable Teflon sample tray which could be moved through UV chamber at an adjustable speed (0.3 cm/s – 2.1 cm/s) between a set of lower and uppers UV lamps which produced 3D light exposure.

First, UV fluence delivery at different wavelengths emitted by four light sources was fully characterized inside the conveyor and on the tray surface using various measurement devices and approaches. This was critical for accurately determining the relative efficacy and uniformity of the UV light sources and treatment conditions. This presentation will outline the methodology used for characterizing UV light conveyor systems and compare the accuracy of common UV light measurement devices including a radiometer with two different UV-C detectors, a spectrometer, and two wireless pucks. Then, the results of evaluation of fluence distribution on the tray surface will be presented. Finally, testing of destruction of naturally contaminated DON mycotoxin on the surface of whole corn and ground corn was conducted using various light sources. The efficacy of DON destruction was measured on corn and results will be presented in comparison with model surfaces.

Co-Authors: Maksym Bazhal, Olena Kushnir, Ken Sturgess, Richard Mariita, Tatiana Koutchma

Amidst the turmoil of war, millions in Ukraine face a dire water crisis, forced to rely on unsafe drinking water sources like lakes, rivers, and old wells. This desperate situation has heightened the need for effective and accessible water purification solutions. Germicidal Ultraviolet (UVC) light generated by light emitting diodes (LEDs) emerges as a promising answer, offering a simple but effective mobile means of water disinfection. Recognizing the potential of this technology, UV4Good, a non-governmental organization was formed. Through the support of Crystal IS, National University of Food Technologies (NUFT) of Ukraine, voluntary donations and seed funding from Institute of Food Technologists (IFT, USA), UV4Good developed and supplied portable UVC disinfection kits to locals in Ukraine. More kits are being manufactured and deployed. These portable UVC disinfection systems comprise of a manual water sprayer, a three-stage filtration system, a UVC LED disinfection unit, and a versatile power supply unit capable of operating on standard 220 VAC, battery 12/24 VDC, or a 15 W power bank. Initial tests conducted in Ukraine demonstrated the kit's efficacy against microbial assemblages found in the Irpin River, with initial turbidity levels of 1.6 NTU. A combination of standard filters (1 μm mechanical filter, 5 μm carbon filter, and 1 μm mechanical filter) and Klaran reactor achieved a significant reduction in the initial total microbial count, from ~5.9 logs to 2.4 logs after treatment. Water purification units were distributed to the local population affected by the crisis. Further development is underway to optimize the solutions design and determine the optimum system requirements needed to achieve drinking water quality standards set by Ukrainian regulations. This UVC innovative solution holds immense promise for alleviating the water crisis in Ukraine and has the potential to benefit communities affected by disasters, manmade or natural, worldwide.

Co-Authors:

Airborne allergens pose indoor air quality challenges; each allergenic protein contains unique immunogenic antigens that are recognized by mammalian immune system. Allergenic protein structure and integrity is essential in facilitating pro-inflammatory responses, triggering allergenic and hypersensitivity reactions through skin contact and aerosol (respiratory) contact. Thus, disrupting allergenic protein integrity represents a treatment strategy to reduce the negative health effects associated with allergen exposure. We report here, common airborne allergenic potential disruption from exposures to low doses of Far-UVC (UV222). Experiments were conducted to disrupt the protein conformation of the following allergens: Der p1/f1 (dust mite), Fel d1 (feline dander), Can f1 (canine dander), Phl p5 (Timothy Grass pollen), Bet v1 (Birch pollen), and Asp f1 (Aspergillus fumigatus mold) using commercially available Far-UVC (UV222) equipment designed for indoor use. Allergens were extracted from purified and natural sources and aerosolized in a respirable size range (0.5 – 5.0 µm) within contained, well-mixed, environmentally-controlled chambers (1 m3 and 10 m3). Air samples were collected from these chambers using condensation growth tube samplers, and aeroallergens were measured by ELISA (Enzyme-Linked Immunosorbent Assay) or MARIA (Multiplex Array for Indoor Allergens). Conformational changes or degradation of the protein allergens would result in lower abundance of allergens in these assays as they both utilize antibody-based allergen epitope recognition. Aerosols recovered in the presence of UV222 showed a decrease in aeroallergen half-life in as early as 20 minutes of UV222 exposure (< 10 mJ/cm2) compared to otherwise identical chamber experiments without UV(RH, temperature, ambient light). These results suggest that UV222 may be applied to inactivate airborne allergens by disrupting the conformational structure of allergenic proteins in time frames relevant to common indoor air exchange rates.

Co-Authors: Erik Swenson, Brian Montalbano

The UVC LED revolution has begun and with it the need for thorough evaluation techniques. Evaluations were first focused solely on LED output. That evolved to a focus on microbicidal power, a simple function of output and microbicidal effectiveness. Though a good start, this does not address a major advantage and valid expectation of UVC LEDs, lifetime, and prolonged effectiveness.

Unfortunately, a clear method for defining UVC LED lifetime has not been defined. Currently, lifetime projections are left to the LED manufacturers which have led to incomplete claims showing only partial data aimed at marketing rather than a clear presentation of lifetime data. Additionally, some groups have attempted to use mathematical simulations to predict lifetime, like TM-21 which was developed for visible LEDs. Since the breakdown mechanisms and responses of UVC LEDs differ from visible LEDs, these attempts could have dangerous impacts to end users as well as damage a promising technologies acceptance with the disinfection market.

Nichia’s Mr. Todd Mikowski will present a useful method for UVC LED lifetime comparison using microbicidal maintenance. This method utilizes key LED characteristics with lifetime data to balance wavelength differences and provide an apples-to-apples comparison, aligning LED selection with system lifetime requirements. Additionally, Mr. Mikowski will share potential solutions and challenges to long term lifetime reporting through the adoption of LM-80 practices for UVC LEDs.

With UVC LED claims beginning to mimic the early mistakes made in general illumination, now is the time for a metric geared towards reliability. Microbicidal maintenance can ensure honest reporting until suitable standardized testing, reporting, and extrapolation can be developed.

Co-Authors: Sean A. MacIsaac, Richard M. Simons, Amina K. Stoddart & Graham A. Gagnon

For decades, ultraviolet germicidal irradiation (UVGI) has been used as a treatment technology for delivering potable water and for upper airway disinfection in shared spaces. Utilizing UV light emitting diodes (UV-LEDs) on surfaces gained popularity at the onset of the COVID-19 pandemic as the cleanliness of shared surfaces and limiting pathogen transfer was becoming increasingly necessary. The maturation of UV- LED technologies coincided with this interest, enabling a new design space for UVGI devices. This work builds on this knowledge base and encompasses some of the first attempts to understand the behavior of surface pathogens using UV-LED technologies.

Industrial pathogens (Aspergillus brasiliensis, Bacillus subtilis) commonly used for validation of industrial disinfectants and antiseptics were inoculated onto common industrial surfaces (steel, glass, plexiglass, epoxy painted coupons) before being irradiated by a 280nm AquiSense Technologies PealLab Beam. A 2-log reduction across all surface types was achieved for Aspergillus brasiliensis and Bacillus subtilis at a fluences of approximately 200 mJ/cm^2 and 15 mJ/cm^2, respectively. The findings from this research provide the foundation for which future UV-LED surface disinfection research can be built upon. Additionally, this work provides methodology for conducting UV-LED experiments on a variety of surfaces and material types and an appropriate recovery method which allows for reproducible results.

Co-Authors: Aaron Goldfain, Heather Patrick, Catherine Cooksey, Thomas Germer

The radiation dose distributed throughout a room or public space determines the germicidal efficacy and safety hazards of the ultraviolet radiation. To accurately model the radiation dose throughout the space, it is critical to know the directional reflectance properties of materials used in the space. There is currently little publicly available data for the UV-C directional reflectance of materials relevant to various aspects of the modeling. In this talk we will describe what the bidirectional reflectance distribution function (BRDF) is, commercial instruments at NIST for BRDF measurements, and NIST’s national BRDF reference instrument. We will include examples of data already collected using the various instruments and discuss the ongoing process of building a publicly available database of the BRDF of common materials.

Co-Authors: Harold Wright and Mark Heath

Carollo has operated the Portland UV Validation Facility since 2003 and performed over 80 validations with flows up to 72 mgd. Validations include both closed vessel and open channel systems done in accordance with the USEPA’s UV Disinfection Guidance Manual, the Ultraviolet Disinfection Guidelines for Drinking Water and Water Reuse, and the IUVA Uniform Protocol for Wastewater UV Validation Applications. Carollo has also been working with Technologiezentrum Wasser (TZW) to perform joint DVGW and UVDGM validations at their validation facility in Sankt Augustin, Germany.

During the past several years, Carollo has been validating more open channel wastewater systems for high level disinfection for non-potable reuse and closed vessel systems for 6 log inactivation for direct potable reuse. This work has shown that low UV dose pathways through the UV reactor can have notable impacts on achieving 5 or 6 log inactivation. Low dose pathways have been attributed to flow behind parked wipers, lamp mounts located on channel floors, seals between the modules and channel walls, and low UV intensity regions between the lamp electrode and the wall or floor of the reactor. This presentation describes how low UV dose pathways impact the relation between log inactivation and the combined variable (S/S0/Q/DL) and how UV dose models based on Computational Fluid Dynamics can be used to identify and address low UV dose pathways, which is recommended before conducting full-scale UV validation testing for high level UV disinfection.

Co-Authors: Steffen Rüting; Philipp Sperle, Christian Bokermann

UV-based advanced oxidation is often applied as final treatment step after reverse osmosis in indirect and direct potable reuse projects. Recent studies reported advantages of UV/HOCl compared to UV/H2O2, because HOCl is readily available onsite, generates hydroxyl and chlorine radicals, and provides disinfection residual. However, the (photo)chemistry of hypochlorous acid and chloramines from RO permeate adds complexity including breakpoint reactions that impact free chlorine and chloramine concentrations upstream of the UV reactor, as well as photolysis and advanced oxidation of those compounds through the UV reactor, all of which impact UV transmittance, UV dose delivery, and UV sensor readings.

The WRF report “UV-Chlorine AOP for Potable Reuse” (WRF5050) provides guidance for implementing UV/HOCl AOP. Following this guidance, this presentation will outline a new concept to operate and monitor UV/HOCl AOP with RO permeates. As the UV dose highly depends on UV transmittance (UVT), which substantially increases due to chlorine and chloramine reduction through the UV reactor, we propose accurate monitoring of UVT at the reactor inlet and outlet with redundant sensors combined with modelling of the UV transmittance profile within the reactor. The modelled UVT profiles are integrated into a CFD-based control strategy that calculates reduction equivalent dose (RED) based on contaminant UV sensitivity.

The new control strategy is validated with data from previous installations (e.g. UVTprofiles measured at Terminal Island) and will be applied at full-scale for the first time in the San Diego Pure Water Project.

Co-Authors: Ana Paula Marques, Carolina Santos, Nicole Ferreira, Katia Luz, Guilherme Ebo, João Sério, Maria Teresa Crespo, Vanessa Jorge Pereira

The development of effective disinfection treatment processes will be crucial to help the water and food industries cope with the inevitable challenges resulting from the increase in human population and climate change.

In this work, light emitting diodes (LEDs) that emit light at different wavelengths were tested in terms of their potential to inactivate Gram-negative and Gram-positive bacteria that are routinely monitored as fecal contamination indicators of water quality (total coliforms, Escherichia coli and Enterococcus faecium) as well as bacteria associated with foodborne outbreaks (Salmonella enterica and Listeria monocytogenes), present at occurrence levels and spiked in real water matrices, salads and stainless-steel surfaces. Extremely high inactivation results were obtained after the LEDs exposure. Additionally, the mechanisms underlying bacterial inactivation, potential photoreactivation, and dark repair were investigated.

The combination of membrane filtration and LED pannels achieved an extremely high quality of permeate in terms of water quality indicator bacteria and bacteria resistant to antibiotics while guaranteeing an extremely high treatment of the retentate, one of the issues associated with the membrane processes.

The results obtained show that ultraviolet-C light emitting diodes are a promising approach for the water and food industries to guarantee effective inactivation of bacteria present in water, food and surfaces.

Co-Authors: Maria Beatriz Cristóvão, Ana Paula Marques1, Andreia Bento-Silva, João Sério1, Maria Gossard1, Mónica Nunes1, Maria Teresa Barreto Crespo1, Pedro Brás de Oliveira, Maria Rosário Bronze, João Goulão Crespo, Vanessa Jorge Pereira

Agriculture irrigation accounts for approximately 70% of all water withdrawals. Climate change and the increase in human population will lead to a higher food and water demand. Hence, it is crucial to explore new water sources for agriculture irrigation, such as the reuse of wastewater effluents.

In this study, different water sources (wastewater effluents, wastewater effluent after nanofiltration treatment and tap water) were used for the irrigation of raspberries. Several antibiotics (ciprofloxacin, levofloxacin, ampicillin, ertapenem and meropenem) as well as total coliforms and E. coli resistant to different antibiotics (ciprofloxacin, levofloxacin, meropenem, streptomycin and ampicillin) were quantified in the different irrigation waters over a 5 month irrigation period.

The combination of UV photolysis with membrane filtration was tested to further treat the permeate and retentate samples from the nanofiltration unit. When ciprofloxacin was present in the permeate samples, after exposure to UV photolysis using a low pressure mercury lamp the antibiotic was not detected. In the highly concentrated retentate samples, 57% of ciprofloxacin and 31% of levofloxacin were degraded by UV photolysis using an extremely low UV fluence. If a higher exposure time was used, the higher degradation levels would be achieved. These low UV fluences were able to inactivate successfully the antibiotic resistant bacteria in the retentate samples (with percent inactivation’s higher than 4-log).

The combination of nanofiltration and UV photolysis produced extremely high quality water for irrigation in terms of the antibiotics and antibiotic resistant bacteria monitored in this study.

Co-Authors:

Disinfection with far-UVC light has made great strides over the past decade, powered by the availability of krypton-chloride (KrCl) excimer gas lamps emitting a safer form of ultraviolet light at wavelengths of 222 nanometers. This initial success has spurred interest in the possibility of additional new far-UVC light sources. Solid-state sources, especially, may be able to deliver far-UVC light in smaller form factors at lower costs, expanding the footprint of human-safe far-UVC disinfection applications beyond those currently enabled by KrCl lamps. Manufacturers of current-generation solid-state light-emitting diodes (LEDs) have started to deliver longerwavelength UVC LEDs (>254nm) for discrete air-, surface-, and water-disinfection applications. However, LED manufacturers have not yet overcome the many significant technical challenges required to deliver the much shorter wavelengths required for human-safe far-UVC (210-to-230nm) disinfection applications. NS Nanotech, a nanotechnology materials company developing university-patented nano-LED technologies, is addressing these challenges on two fronts:

• First, we are developing a solid-state semiconductor that emits far-UVC light. While larger than an LED, our far-UVC semiconductor based lamp is smaller and delivers other solid-state technology advantages. We expect to start delivering it in 2024 and to position it as an effective, safe, solid-state disinfection solution for personal and closer-quarters applications where excimer lamps are not currently practical.
• Second, we are progressing on a multi-year plan to develop an entirely new generation of submicron-scale nanowire-based LEDs that will break the cost and technology barriers holding back current-generation LEDs. We have already demonstrated world record performance for nano-scale red and green LEDs and are on a path to deliver the world’s first solid-state nanoLEDs that emit far- UVC light in the 210-to-230nm wavelength range.

Co-Authors: Sung-Jin Park, Christopher Jones, Christopher Bowers, Ernest R. Blatchley III

Far UV-C radiation is known to be effective for inactivation of airborne pathogens, but to also have the benefit of having less potential to cause damage to human tissues (esp. skin and eyes) than longer wavelengths of UV-C radiation. With those features in mind, a project was initiated to develop personal protective equipment (PPE) that incorporates Far UV-C radiation, specifically as alternatives to filtering masks, such as those that meet the N95 standard. The ultimate goal of this project is to develop alternative PPE devices based on Far UV-C radiation that are effective for inactivation of airborne pathogens, but that do not present other unacceptable risks to the users. Design and validation of these devices has involved a combination of laboratory experiments and numerical simulations.

The Far UV-C sources being used in this work are optically-filtered, flat-panel KrCl* plasma lamps, which emit at a characteristic wavelength of 222 nm. Laboratory-based measurements have included quantification of the fluence rate field around individual lamps using a micro-fluorescent silica detector (MFSD). The MFSD allows measurements that accurately characterize local fluence rate. The experiments involved a 3-dimensional measurement space that resulted in quantification of the fluence rate field in the vicinity of the lamps at locations and distances that are relevant to near-field applications.

A prototype device was developed for use in testing of human exposure and aerosolized viral inactivation. Colorimetric dose cards designed for 222 nm radiation were cut into pieces and placed around the face of a manikin with the prototype mask installed to quantify human exposure to Far UV-C radiation. A viral challenge of the device was performed using coliphage T1 as the challenge agent. Aerosolized T1 were presented to the manikin using a Collison nebulizer. T1 inactivation was quantified by drawing air containing aerosolized T1 through the nose and mouth of the manikin at a range of known volumetric flow rates with the mask installed and uninstalled (control).

Numerical simulations involved a combination of raytraced optical fluence rate field modeling and computational fluid dynamics (CFD) air flow modeling. The fluence rate field simulations were compared with the MFSD and skin/eye exposure measurements described above. The fluence rate field and lagrangian particle tracking from the CFD simulations were used to simulate inactivation of aerosolized T1, matching the viral challenge experiment.

Collectively, the coordinated laboratory experiments and numerical simulations allow for detailed analysis of the characteristics and performance of this system, as well as its implications with respect to human health and safety.

Co-Authors: Andrew Miller, Yushi Onoda, Kai Ishida, Toshihiko Aizawa, Shigeharu Yamauchi, Yasuo Fujikawa, Tomotake Tanaka, Kazuaki Mawatari, Akira Takahashi, Richard Kuhn, E.R. Blatchley III

RSV and HMPV are airborne viruses that cause similar infections of the human respiratory system. Both are negative-sense, single-stranded RNA viruses that belong to the Paramyxoviridae family that cause respiratory infections with similar symptoms. A vaccine against RSV has recently become available; no vaccine has been developed for HMPV. Both viruses can be transmitted via an airborne route, so control of disease transmission associated with these viruses may be possible through implementation of germicidal UV irradiation (UVGI) systems. However, the responses of RSV and HMPV to exposure to germicidal UV radiation have not been quantified.

A collaboration among Nichia Corporation, Tokushima University, and Purdue University was developed to evaluate the action spectra of RSV and HMPV. A collimated beam device was used based on UV LEDs to allow selection of output (peak) wavelengths of 250, 254, 257, 260, 263, 267, 270, 275, 280, 290, and 300 nm. Wavelength selection was accomplished by selection and insertion of an LED-based UV “light engine” for the wavelength of interest. Additional collimated beams based on KrCl* excimer, low-pressure Hg lamp, and UV LEDs were applied to expand the wavelength range and explore other phenomena. For each wavelength, a series of UV exposure doses was applied to an aqueous suspension of either RSV or HMPV. For each wavelength-pathogen pair, exposed samples were subjected to TCID50 or plaque assays to quantify changes in infectivity among the exposed viruses. The data were fit to a 1st-order inactivation model to develop estimates of the inactivation constant at each wavelength. In turn, these values were used to quantify the action spectrum of both viruses. This experimental approach can be expanded easily to allow quantification of the action spectra of other pathogens.

Co-Authors: Jonathan Heler, Eyal Ben Yitshak

Jewish ritual baths (mikveh) are designed for the Jewish rite of purification, for both man and women. A typical mikveh is a 2 x 1.5 x 2 borehole, filled with water which must contain a certain percentage derived directly from a natural source. Thousands of ritual baths exist in the world, serving hundreds of thousands of orthodox Jews daily. Due to the fixed purification hours, ritual baths usually operate under a huge momentarily bathers load, and the water is typically treated with chlorine. However, its harmful effect on bathers and ineffectivity toward protozoa forced regulators and engineers to look for alternative solutions. A highly attractive new option is the use of UV LEDs for disinfection.

A key advantage of LEDs in this perspective (over Hg UV lamps for example), is their flexible reactor configuration. This answers a principal problem in applying technology for ritual baths – the strict laws of the Halacha. These laws forbid any water pumping or circulation, as well as forcing other mechanical constraint. Azrieli college, together with Mikveh Tech company, has developed the first kosher LEDs UV reactor, designated for treating Jewish ritual baths. The reactor comprises of a tubular pipe, divided into two sections: the upper section holds a cartridge filter and the lower section is a UV cell housing 3 280 nm LEDs. The entire reactor is submerged vertically inside the borehole, with a motor at its bottom circulation the water downward (through the filter then the LEDs).

Both pilot- and full-scale experiments produced extraordinary results, with inactivation of both E.coli (by 6-log) and B. subtilis spores (by 4-loge) after merely four turnover of the water volume. In addition, the LEDs disinfected any biofilm detached from the filter, and the water remained microorganism-free for at least 7 days without the need of additional chlorine.

Co-Authors: Natalie Hull

Antibiotic resistant bacteria (ARB) and opportunistic pathogens (OP) have captured a lot attention due to their potential to survive and potentially cause infections in individuals after water treatment processes. This study investigated how engineered disinfection technologies such as UV impact waterborne microorganisms. The research addresses the impact of UV wavelengths on OP and ARB at cell and molecular levels and impact of drinking water treatments on microbial community composition. To assess the impact of UV wavelengths on cell inactivation, gene damage, and limitation of virulence of ARB and OP, Bacillus subtilis 1A18 and nontuberculous mycobacteria (NTM) strains including M. smegmatis and smooth, rough, and mixed morphotypes of M. avium-intracellulare clinical isolates) were exposed to either 222 nm KrCl excimer lamp or 254 nm low pressure Hg lamp. In the ARB study, 222 nm wavelength was more effective than 254 nm at cell inactivation, extracellular DNA damage and HGT inhibition. For OP study, inactivation by 222 nm and 254 nm were similar for M. smegmatis while smooth morphotypes of MAC were more sensitive to UV, the 222 nm wavelength was more effective than 254 nm for rpoB and hsp65 gene damage. For microbial community in a small drinking water treatment plant, 16S rRNA sequencing was used to characterize bacterial composition in bulk water and biofilms with a particular focus on genera potentially containing OPs from sample sources through treatments including filtration, chlorination, and UV light-emitting diode (LED) disinfection. Significant differences were observed between water and biofilms and sample sources. Compared with filter effluent, there was no significant difference for UV but a significant difference for chlorination, indicating that a higher selective pressure chlorine disinfection. Together, these results indicate the potential for targeted implementation of UV disinfection methods to fight waterborne pathogens and minimize the risks to human health.

Co-Authors: Danmei Chen

The combined variable (CV), defined as the ratio of the power output percent (based on sensor readings) divided by the flow rate and organism sensitivity, has been shown to provide a strong linear relationship between it and the log inactivation of a given UV reactor and has gained acceptance in estimating UV reactor performance based on bioassay data. The CV approach stems from the fact that the log inactivation (LogI) for a single microbial path will be directly proportional to the UV lamp intensity and inversely proportional to the flow rate and organism sensitivity. However, the application of the CV approach for validation of small UV LED reactors has two important challenges that require exploring. First, it is not clear if the CV approach can be generally applied for the case where one or more LEDs have been turned off. Such a scenario is similar to the case of a regular UV reactor where a lamp is / has turned off, and arguably leads to an entirely different UV dose distribution requiring its own set of calibration parameters. Second, small UV LED reactors are typically not fitted with sensors. A key parameter of the CV is the sensor reading, which is a function of lamp output power and the UV transmittance (UVT) of the water leading to issues in properly applying the CV in validation, as well as operation. In this work we utilize CFD and numerical models to address both issues and provide practical recommendations in the context of reactor validation and operation.

Co-Authors: Bruce Rittmann, Pedro Alvarez, Paul Westerhoff

Biofilms give rise to a range of issues, spanning from harboring pathogens to accelerating microbial-induced corrosion in pressurized water systems. Introducing germicidal UV-C (200–280 nm) irradiation from light-emitting diodes (LEDs) into flexible side-emitting optical fibers (SEOFs) presents a novel light delivery method to inhibit the accumulation of biofilms on surfaces found in small-diameter tubing or other intricate geometries. This work used surfaces fully submerged in flowing water that contained Pseudomonas aeruginosa or Legionella pneumophila, opportunistic pathogens commonly found in water system biofilms. A SEOF delivered a UV-C gradient to the surface for biofilm inhibition. Biofilm growth over time was monitored in situ using optical conference tomography. Biofilm formation was effectively inhibited when the 275 nm UV-C irradiance was ≥8 μW/cm2. Biofilm samples were collected from several regions on the surface, representing low and high UV-C irradiance. RNA sequencing of these samples revealed that high UV-C irradiance inhibited the expression of functional genes related to energy metabolism, DNA repair, quorum sensing, polysaccharide production, and mobility. However, insufficient sublethal UV-C exposure led to upregulation genes for SOS response and quorum sensing as survival strategies against the UV-C stress. These results underscore the need to maintain minimum UV-C exposure on surfaces to effectively inhibit biofilm formation in water systems.

Co-Authors: Bruce Rittmann, Pedro Alvarez, Paul Westerhoff

Agriculture irrigation accounts for approximately 70% of all water withdrawals. Climate change and the increase in human population will lead to a higher food and water demand. Hence, it is crucial to explore new water sources for agriculture irrigation, such as the reuse of wastewater effluents.

In this study, different water sources (wastewater effluents, wastewater effluent after nanofiltration treatment and tap water) were used for the irrigation of raspberries. Several antibiotics (ciprofloxacin, levofloxacin, ampicillin, ertapenem and meropenem) as well as total coliforms and E. coli resistant to different antibiotics (ciprofloxacin, levofloxacin, meropenem, streptomycin and ampicillin) were quantified in the different irrigation waters over a 5 month irrigation period.

The combination of UV photolysis with membrane filtration was tested to further treat the permeate and retentate samples from the nanofiltration unit. When ciprofloxacin was present in the permeate samples, after exposure to UV photolysis using a low pressure mercury lamp the antibiotic was not detected. In the highly concentrated retentate samples, 57% of ciprofloxacin and 31% of levofloxacin were degraded by UV photolysis using an extremely low UV fluence. If a higher exposure time was used, the higher degradation levels would be achieved. These low UV fluences were able to inactivate successfully the antibiotic resistant bacteria in the retentate samples (with percent inactivation’s higher than 4-log).

The combination of nanofiltration and UV photolysis produced extremely high quality water for irrigation in terms of the antibiotics and antibiotic resistant bacteria monitored in this study.

Description

GUV manufacturers and users are experiencing amazing changes in technology that promise to accelerate capabilities for reducing the risks of variable infectious disease transmission. The International Ultraviolet Association (IUVA) Healthcare Working Group invites you to join its partners and invited GUV experts to explore the key issues faced by businesses and public organizations developing or deploying state-of-the-art GUV technology. This special session is on day 3 of the 2024 IUVA Americas Conference in Orlando and is packed with actionable intelligence and guidance on GUV for healthcare. The agenda provides a combination of insights from leading business, technical, and policy authorities in GUV.

Why attend?

The GUV industry is continuously improving GUV source and device designs, manufacturing, and applications and investing in infectious disease transmission countermeasures. Having to keep up with emerging trends, needs, and changes in the risk environment is a challenge. At this session, gain insights from GUV innovators and leaders and learn about GUV and its relevance to your work. The session is dynamically organized, featuring leading speakers in the field to connect you with the information you need to achieve positive advances in GUV for healthcare.

Who should attend?

All stakeholders interested in the design, development, administration, or use of GUV sources and devices for infection control, risk reduction, and prevention are welcome to participate. This session is designed to connect commercial companies of all sizes with subject matter experts in infectious disease, UV industry markets and trends, and government programs, measures, and policies.

Presentation Overview

Far UV-C radiation has characteristics that are distinct from other parts of the UV spectrum, in terms of photochemistry and photobiology. These characteristics have motivated investigations into new applications of UV radiation. However, important challenges exist that have limited the application of technologies based on Far UV-C radiation.

Speaker

Ernest R. Blatchley III is the Lee A. Rieth Professor in Environmental Engineering at Purdue University, where he holds a joint faculty appointment in the Lyles School of Civil Engineering and the Division of Environmental & Ecological Engineering. The focus of research within the Blatchley group is on physico/chemical processes of Environmental Engineering, with particular emphasis on photochemical reactor theory. Recent research in the Blatchley group has been directed largely at applications of UV radiation for disinfection of air and surfaces. He is currently the President-Elect of IUVA.

Coauthors: Sandra Probst-Rüd PhD, Paul Onkundi Nyangaresi Ph.D., Adefolawe A. Adeyeye, Martin Ackermann, Ph.D., Kristopher McNeill Ph.D.

As UV technologies continue to evolve, so does the need to understand disinfection mechanisms to ensure that UV treatment continues to adequately protect public health. In this research, two Escherichia coli (E. coli) strains (a wild type K12 strain and an engineered strain) were irradiated with UV-C at 268 nm both independently and after exposure to UV-A (365 nm).

A synergistic effect was found on the viability of the wild type E. coli K12 strain when UV-A irradiation was applied prior to UV-C. Sublethal UV-A doses, which had a negligible effect on cell viability alone, enhanced UV-C inactivation by several orders of magnitude. This indicated a specific cellular response mechanism to UV-A irradiation, which was traced to direct photolysis of the transfer RNA (tRNA), which are critical links in the translation of messenger RNA to proteins. The wild type K12 strain MG1655, containing tRNAs with a thiolated uridine, directly absorbs the UV-A light, which leads to a reduction in protein synthesis, making them more susceptible to UV-C induced damage. However, the K12 strain SP11 (ThiI E342K), with a point mutation in the thiI gene that prevents a post-transcriptional modification of tRNA, experienced less inactivation upon subsequent irradiation by UV-C. The growth rate of cells, which was inhibited by sublethal UV-A doses, was not inhibited in this mutant strain with the modified tRNA.

Time-lapse microscopy with microfluidics showed that sub-lethal UV-A caused a transient, reversible, growth arrest in E. coli. However, once the growth resumed, the cell division time resembled that of unirradiated cells. Damage induced by UV-A impaired the recovery of damage induced by UV-C. Depending on the UV-A dose applied, the synergistic effect remained even when there was a time delay of several hours between UV-A and UV-C exposures. The effect of sublethal UV-A was reversible over time; therefore, the synergistic effect was strongest when UV-C was applied immediately after UV-A. Combining UV-A and UV-C irradiation may serve as a practical tool to increase UV disinfection efficacy, which could potentially reduce costs while still adequately protecting public health.