Co-Authors: Paul Nyangaresi, Fermin Reygadas, Sara Beck

The presence of water that is safe is essential for human survival. United Nations Sustainable Development Goal 6.1 outlines the need for universal and equitable access to safe and affordable drinking water for all by 2030. However, many drinking water sources worldwide are heavily contaminated with microbial contaminants, leading to waterborne diseases. Many efforts are being made to reduce these diseases through efficient water treatment and adequate water supply. One of the water treatment methods employed is ultraviolet disinfection. Ultraviolet (UV) disinfection has been used for pathogen inactivation for many years. According to various studies, one of the limitations of low-pressure UV systems is scaling and fouling of the quartz sleeve of UV lamps due to the presence of organic and inorganic contaminants in the source water, which leads to low efficacy. However, there are limited studies on scaling and fouling in UV LEDs. This research compares the decline in disinfection efficacy of two UV systems, a traditional commercial low-pressure UV reactor, and a UVC LED flow-through reactor, resulting from scaling and fouling. Comparison of the effectiveness of these systems will be achieved by measuring the dose before and after exposure to source water with varying hardness concentrations. Furthermore, the reversal of scaling and fouling in these UV systems using lime and lemon juice, which are available in low-resource settings, will be investigated. This research is ongoing on a laboratory-scale; however, the results will be available before the conference and will have applications in rural communities in the future. Keywords: Ultraviolet disinfection of water, UV LEDs, small-scale systems, low-resource context.

Co-Authors: Kiran Ahlawat, Ramavtar Jangra, Arti Sharma, Meenu Chhabra, and Ram Prakash

Acquiring clean water is one of the greatest worldwide problems affecting people today. By 2050, over 57 percent of the world's population will confront the problem of clean water shortage [1]. In order to reach the objective of having safe and clean water, the concept of eradicating microbes and organic contaminants from textile wastewater is gaining popularity worldwide [2]. Textile effluents are a significant industrial pollutant because they contain approximately 15% unfixed dyes that may be discharged into the environment.

In this work we present a potential solution to fix the dye effluent in the textile industry. A high-efficiency Far UV-C (222 nm) excimer source, safe for human skin and eyes, has been developed and used for the degradation of Reactive Red 35 / Brilliant Red 5B dye (azo dye). The concentration of the dye used for the experiments was 20-100 mg/L in distilled water. The effect of loading of different concentrations of TiO2, H2O2, and the combined effect of both has been studied. The TiO2 concentration has been varied from 0.5-2 g/L. The concentration of H2O2 has been varied from 1-5 mM at an interval of 1 mM. The progress of photocatalytic degradation of the reactive red 35 has been then studied by the maximum absorbance at λ= 536 nm by UV visible spectrophotometer, and also the toxicity of the treated solution has been evaluated by measuring the chemical oxygen demand (COD). pH, H2O2 and TiO2 loading showed to be critical variables for the photocatalytic degradation process for aqueous reactive dye solutions. The experiments indicated that both UV light and H2O2/TiO2 were needed for the effective destruction of the dye. More than 90% COD abatement for the treated dye concentration is obtained with just 10 minutes of treatment, and more than 99% decolourization is achieved in just 3 minutes of treatment with UV/H2O2. The results of these efforts will be presented.

Reference 

[1]A. Boretti, L. Rosa, Reassessing the projections of the World Water Development Report, Npj Clean Water. 2 (2019). https://doi.org/10.1038/s41545-019-0039-9. 

[2]R. Al-Tohamy, S.S. Ali, F. Li, K.M. Okasha, Y.A.G. Mahmoud, T. Elsamahy, H. Jiao, Y. Fu, J. Sun, A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety, Ecotoxicol. Environ. Saf. 231 (2022) 113160. https://doi.org/10.1016/j.ecoenv.2021.113160.

Co-Authors: Amodeo D., De Palma I, Papale G, Nante N, Cevenini G, Messina G.

Background Ultraviolet-C (UVC) radiation, specifically at the peak wavelength range of 260-265 nm, demonstrates a remarkable efficacy in the deactivation of microorganisms. However, conventional low-pressure (LP) or medium-pressure mercury lamps, which emit UVC light at 254 nm, possess limitations such as size, warm-up time, and inherent risks to health and the environment. UV light-emitting diodes (UV-LEDs) have emerged as a viable option, offering instantaneous high-intensity light. These UV-LEDs exhibit compactness, durability, and economic feasibility. Furthermore, they do not contain mercury, ensuring a safer choice, maintaining a consistent output with low-temperature fluctuations, and emitting specific target wavelengths, such as the desired range of 260-265 nm, to effectively accomplish germicidal actions. The primary objective of this study is to compare the performance of four UVC-LEDs, each operating at distinct wavelength peaks, for surface disinfection of two bacterial species.

Methods

This experimental study was conducted between April and May 2023. Petri dishes were contaminated with E. coli and S. aureus at a concentration of 1.5x104 CFU/mL. Petri dishes were then positioned 7 cm distant from the light source, exposing them to different UVC wavelength peaks (232, 255, 265, and 280 nm). Two energy doses were tested for each microbe: 4 and 5 mJ/cm2 for E. coli and 4.5 and 6 mJ/cm2 for S. aureus. The statistical analysis was performed using Stata software. The final results were expressed as the mean logarithmic reduction with a 95% confidence interval.

Results

For E. coli, the highest reduction in the bacterial count was observed at 265 nm with a dose of 4 mJ/cm2 (on average 1.60 log10, CI 1.32-1.88), while the lowest reduction was at 232 nm (0.82 log10, CI 0.76-0.89). However, when the dose was increased to 5 mJ/cm2, the highest reduction was obtained at 232 nm (2.04 log10, CI 1.75-2.34), and the lowest reduction was at 255 nm (1.03 log10, CI 0.90-1.16). Regarding S. aureus, at a dose of 4.5 mJ/cm2, the highest reduction was at 232 nm (3.50 log10, CI 2.85-4.15), whereas the lowest reduction was at 255 nm (0.93 log10, CI 0.84-1.02). Conversely, when the dose was increased to 6 mJ/cm2, the highest reduction occurred at 265 nm (3.96 log10, CI 3.35-4.56), while the lowest reduction was at 255 nm (1.32 log10, CI 0.67-1.98).

Conclusion

The study's results indicate that the emission of specific UVC wavelength peaks is a crucial characteristic of LEDs that significantly differentiates the biocidal effectiveness of ultraviolet light.

Co-Authors: N/A

This presentation concerns the complex ultraviolet wavelengths generated by more than 125 years of historical UV lamps from the earliest days of experimentation. The wavelengths were analysed using antique quartz lens and quartz prism spectroscopes from the pioneers in UV spectroscopy, Richard and Joseph Beck and Adam Hilger. The development of the lamps started with the experiments of Heinrich Geissler, Johann Hittorf, and Julius Plücker in the earliest days of Geissler Tubes and gas spectroscopy to the ultraviolet research of Josef Maria Eder, Eduard Valenta, and Wilhelm Conrad Röntgen which led to the accidental discovery of the X-Ray. Other early pioneers include Sir William Crookes, Niels Finsen, Franz Exner, Eduard Haschek, Thomas Edison, Clarence Dally, Nikola Tesla, Thomas Burton Kinraide, Frederick Finch Strong, Theodore Lyman, Sophus Bangs, and Peter Cooper Hewitt. The lamps studied date to the earliest development of UV lamps with icelandic spar and rock crystal windows to the slow development of the quartz lamp, with highlights showing the difficulties in making graded glass seals and cast hermetic seals in the earliest quartz lamp prototypes. Spectra will be shown from carbon arc lamps that include rare earth elements and metallic cores; spark and arc spectra from metallic arc lamps; the development of low to medium and high pressure quartz lamps; and various experimental UV lamps of novel designs where few physical models exist in museums around the world. During a time when UV-LEDs and Excimer lamps are generating wavelengths considered to be new or novel, this presentation will offer insight into the past showing that extensive research into obscure UV spectra has been done over a century ago, and has simply been forgotten over time. The presentation ends with an invitation to the guests to visit a museum and extensive library archive in the United States that features many rare UV lamps, research papers, and literature available to the public both in person and free-to-view online.

Co-Authors: Christopher Bowers, Chris Jones, Eric Prast, Ernest R. Blatchley III, Karl G. Linden, Richard A. Rasansky and Joel Ducoste

The recent COVID-19 pandemic has created a demand for expanded public health interventions against the spread of airborne disease. While N95 masks have been effective, the public response to masking has been unpredictable, sparking interest in novel technologies that are less intrusive. A possible alternative to filtration masking is UVC based personal protection equipment (PPE) that does not impede breathing, and also inactivates airborne pathogens rather than capturing them. Such technology has the potential for widespread adoption and would ensure that vulnerable populations can be safely protected from future airborne biothreats.

The development of UVC based PPE requires critical evaluation of the disinfection potential of several alternative designs. Although experimental evaluation provides the ultimate determination of disinfection performance, such methods can be cost prohibitive when exploring many design alternatives. Numerical multi-physics models that combine optical and computational fluid dynamics (CFD) simulations are a cheaper alternative to evaluate PPE configurations, with optimal designs being then selected to undergo physical and experimental prototyping. The primary objective of this work was to develop and validate such numerical methods to help expedite PPE development, especially when these PPE systems must be designed to minimize energy cost and exploit reflective surfaces.

Photopia and Ansys Speos, cutting edge software that use ray tracing to simulate light source emanation, were used along with the radiative transport equation (RTE) to evaluate the optical properties of a range of UVC spectrum sources in multiple PPE configurations. These light models were coupled with Ansys Fluent CFD simulations to evaluate the average UVC dose delivered to air as it is being breathed, allowing us to evaluate disinfection potential for dynamic systems that match real-world use case scenarios. Our results show that ray tracing models better predict the impact of reflective surfaces than the RTE model, a requirement for PPE that uses material exceeding 40% reflectance. Further, the use of an enclosed design with highly reflective walls was found to improve UVC dosing by up to 80 times, illustrating the importance of effective design. To validate these methods, simulated pathogen inactivation was compared to experimental tests carried out using T1 phage as a pathogen surrogate (as addressed in part-one of this three-part presentation), and the results were in good agreement with one another. This work shows how numerical simulations can play a vital role during iterative design and lays the groundwork to develop more complex and effective PPE in the future.

Co-Authors: Johannes Schleusener, Silke B. Lohan, Marius Kröger, Daniela F. Zamudio Díaz, Neysha Lobo-Ploch, Claudia Sicher, Nevin Opitz, Paula Zwicker, Cornelia M. Keck, Martina C. Meinke

Due to the global spread of multidrug-resistant pathogens, the development of alternative physical disinfection methods is strongly needed. A very promising method for pre-surgical decolonization of the skin, as well as for the treatment of critically colonized or chronic wounds, is the use of 233 nm far-UVC radiation by applying LED systems. At an application dose from 40 to 60 mJ/cm2, this radiation already shows complete eradication of Methicillin-resistant Staphylococcus aureus (MRSA) on agar plates and germ carriers. Unlike UVC radiation of 254 nm, which is known for the disinfection of water and surfaces, it is strongly absorbed in the uppermost, non-nucleated layer of the skin, the stratum corneum. However, a comprehensive risk assessment addressing the effects of this radiation on skin is necessary to ensure its translation into the clinical field. Thus, we have evaluated the formation of DNA damage and free radicals in intact and wound ex vivo skin as well as in 3D epidermal skin models. Moreover, the damage development was investigated in different skin types. 233 nm far-UVC showed only superficial DNA lesions in intact skin compared to UVB and 254 nm radiation. Furthermore, the radical formation was lower than for VIS-NIR irradiation, which is equivalent to a 20 min stay in the noon sun under a cloudless sky. Additionally, no increase in the abundance and depth of DNA damage in wound skin covered by artificial wound exudate could be observed as compared to intact skin. In various skin types, the differences in DNA damage were much smaller than the differences after UVB irradiation. From these results, it can be concluded that the application of 233 nm on human skin at antimicrobial doses from 40 to 60 mJ/cm2 can be considered safe in various settings.

Co-Authors: Eman Alhamdan, Daniel Murnick

Low pressure mercury (LP) lamps are widely employed in disinfection applications for their efficient and sharp emission peak at 254 nm; however, mercury vapor discharge also produces a minor emission peak in the vacuum ultraviolet (VUV) range at 185 nm. These photons are of sufficient energy to directly photolyze many recalcitrant water contaminants and have recently been pursued for destruction of poly-/perfluoroalkyl substances (PFAS). Unlike with germicidal emissions, the VUV output intensities of LP lamp products can vary widely and specifications relevant to photolytic applications are rarely provided by the manufacturers. Herein we present an assessment of the VUV output of five commercial LP lamps and discuss the roles of ballast selection, glass composition, amalgams, carrier gas, pressure, and temperature. Radiometer readings and degradation of perfluorobutanoic acid (PFBA) were used for comparing relative intensities. Depending on the specific configuration of the lamp system, VUV output varied by as much as 100% between lamps with the same wattage rating. Methods of quantifying VUV intensity were also assessed, and significant drawbacks to the commonly-used collimated beam approach were revealed. Finally, a highly efficient corona discharge xenon excimer lamp (Xn2*; λ=172 nm) was also evaluated as a source for photolytic water treatment. While the excimer source degraded PFBA with a higher energy efficiency than LP sources, the difference was not proportional to its much greater VUV fluence and possibly indicated a saturation effect.

Co-Authors: Danmei Chen, Ron Hofmann, Yuri Lawryshyn, Erin Mackey

Ultraviolet germicidal irradiation (UVGI) disinfection systems are used in air ducts, with their potential importance underscored by the recent pandemic. However, the absence of a universal standard for performance assessment poses challenges in regulating claims made about their treatment efficacy. In performance testing, a target microorganism’s inactivation efficacy is estimated by assuming that the target microorganism receives the same dose as the surrogate. In reality, different elements in a UV system may receive different UV doses. The variance in UV dose distribution could lead to a discrepancy between the reduction equivalent dose (RED) of a target microorganism and that of a surrogate. This is called the RED bias. Neglecting the RED bias leads to uncertainties related to the consistency with which a surrogate accurately reflects the treatment of a target. The RED bias concept is well-established in UV water disinfection, but its implications in air disinfection remain unexplored. In this study, the RED bias was evaluated in an in-duct UVGI air disinfection system based on the existing U.S. EPA test series using computational fluid dynamics (CFD) modeling. Additionally, a control strategy called the combined variable (CV) approach was proposed to mitigate the RED bias effect. The results addressed the limitation of characterising an air device with average dose, highlighted the existence of RED bias when using a resistant surrogate (e.g., MS2) to predict inactivation of a sensitive target (e.g., SARS-CoV-2), and demonstrated the use of the CV approach as a reliable system control strategy. By addressing the RED bias effect and offering a solution for mitigating it during performance assessment of air devices, this study’s outcomes could benefit various stakeholders involved in UVGI air disinfection systems.

Co-Authors: Tianyi Chen, Susan Andrews, Ron Hofmann

In the full advanced treatment (FAT) process for water reuse (i.e., microfiltration, reverse osmosis and advanced oxidation), chloramines are often added before MF to prevent biofouling. More than 50% of these chloramines may pass through the RO and then react with free chlorine that is applied to the RO permeate for downstream UV/chlorine AOP. The reaction between chlorine and chloramines happens in the order of tens of seconds at the low pH (e.g., 5.5) of RO permeate. Therefore, the progress of the reactions can affect the exact oxidant speciation when the water enters the UV reactor. As chlorine and chloramines have different photochemical properties, the subsequent UV-chlor(am)ine efficiency may vary depending on the chlor(am)ine speciation. Although kinetic models to predict oxidant speciation exist, they generally lack validation for conditions relevant to RO permeate (e.g., < 1 min, pH ~5.5). Furthermore, it is unclear how the progress of the chlorine and chloramine reactions affects radical formation and pollutant degradation in UV/chlor(am)ine treatment. In this study, a published chlor(am)ine model was rebuilt and calibrated by experiments conducted at pH 5.5. The calibrated model showed good accuracy in predicting chlorine and chloramine concentrations under various conditions at pH 5.5. The model results were used to predict pollutant log reduction in UV/chlor(am)ine treatment, through OH radical exposure (∫[OH]dt) for UV reactions starting at different lag times following introduction of the chlorine to the RO permeate. The log reduction was predicted to be 10-25% higher if UV reaction started 200 sec later than immediately after chlorine addition. Further analysis showed Cl radical formed by chloramine photolysis converted to OH and overcame the decrease in OH from HOCl. The optimal chlorine dose was also predicted for common reaction conditions in RO permeate. Pollutant log reduction is affected by the specific concentrations of chlorine and chloramines when UV exposure starts.

Co-Authors: n/a

The accurate measurement of UV radiation encounters more challenges than the equivalent measurements of visible light [1]. The need to accurately measure far-UVC sources in order to determine germicidal efficacy and photobiological hazard, presents particular difficulties.

UV radiometers are extensively used for measuring UV irradiance (W/m2) or radiant exposure (J/m2) over a specific spectral range or in accordance with a spectral function such as photobiological actinic UV. Biological action spectra are typically highly wavelength dependent and therefore difficult to implement. The consequences of the imperfect spectral sensitivity function of UV radiometers as well as their spatial response must be considered carefully. Whilst appropriate calibration methods can minimize spectral mismatch errors, UV radiometers are prone to both over and under record photobiological hazard of far-UVC sources.

Spectroradiometers overcome the lack of spectral resolving power of radiometers and enable the comprehensive characterization of UV products including the conformity testing against international safety standards [2]. Double monochromator-based spectroradiometers are considered to be the reference instrument. In practice, array-based spectrometers are more commonly employed, but most tend to overstate the actinic UV hazard.

Internal stray light is often the dominant factor limiting the accuracy of UV spectroradiometers. A number of techniques can be employed to reduce internal stray light including the use of a tunable laser to characterize a spectrometer enabling a stray light correction matrix to be applied to subsequent measurements. Careful implementation of stray light correction techniques is necessary to ensure accurate far-UVC dosimetry as well as photobiological hazard assessments in accordance with latest standards [3].

References

[1] CIE 220:2016, Characterization and Calibration Method of UV Radiometers

[2] IEC 62471:2006, Photobiological safety of lamps and lamp systems

[3] ACGIH 2022 TLVs and BEIs. (2022).

Co-Authors: Cameron Miller

It is common practice to validate the effectiveness of GUV equipment by testing the reduction of pathogens in specified settings. The technology and procedures are well established in the water disinfection. However, the increasing use of GUV in air and surface disinfection raises questions about practicality of such procedures, costs of testing and the accuracy, repeatability and validity of the results in actual applications.

The presentation takes a systematic look at the expected outcome of such testing and analyses some of the error causes. It is suggested to take a fresh, critical look at the current practice. The measurement and modeling of the light distribution on surfaces and in volumes is very well established and can be modelled and measured with relatively high accuracy.

However, the pathogen testing procedures and the measurement of pathogen susceptibility shows wide error margins that may depend on small details that are very difficult to control, measure and repeat. The results on surfaces depend among others on surface roughness, wettability, soiling, substrate reflection and inoculate concentration and preparation. Some of these are very challenging to estimate, measure, repeat or improve. Moreover, often surrogates instead of the actual pathogen of interest are used for practical, safety and cost reasons. Although there are reasonable assumptions that such practice is acceptable, the uncertainty and variability of results raises additional questions about the actual validity of such results.

Measurement of pathogen reduction in air is even more challenging. Especially air flow patterns and residence time of pathogens in a test chamber, in addition to wall effects, seem to indicate that such measurements are of minor value for practical applications where these parameters will always be different.

The practitioners of GUV are encouraged to take a fresh look at the current practices in air and surface effectiveness. It is suggested to take irradiance or fluence rate as a key metric of GUV systems. For modeling of practical outcomes, corrections could be applied that have been established by rigorous scientific research.

Co-Authors: Jessica Bennett, Lindsay Anderson, Liam Salsman, Amina Stoddart, Graham Gagnon

Shifts in drinking source water quality across the globe, including changes in water chemistry and increasing concentrations of emerging contaminants, are necessitating the use and development of advanced treatment processes and monitoring tools for efficient production of safe and clean drinking water. Photocatalytic processes rely on the activation of a semiconductor material with sufficient photon energy to effectively drive oxidation and reduction reactions. TiO2 is the most widely used semiconductor for photocatalytic applications due to its efficacy, innocuous nature, well-defined chemical characteristics, and relatively low cost. The addition of a bias voltage that is above the flat-band potential of the semiconductor to TiO¬2/UV systems (i.e., photoelectrocatalysis) improves oxidation efficiency by reducing the recombination of generated electron/hole pairs – reactive sites on the TiO2 surface – upon irradiation. Electron/hole pairs can oxidize or reduce contaminants and natural organic material (NOM) in water matrices directly, or indirectly through the production of reactive intermediates. Though TiO2 is well-established in its use as a photocatalyst, more recent work has explored TiO2-based photoelectrocatalytic technologies for drinking water applications including environmental monitoring and the remediation of contaminants of concern.

Here, we provide an overview of our use of TiO2-based photoelectrocatalytic processes for drinking water monitoring and treatment. We demonstrate the effectiveness of a photoelectrocatalytic monitoring system as an indicator of water treatment performance by detecting changes in NOM character that are not always identified by conventional metrics (e.g., TOC, UV254) ¬as well as the use of this technology for treating emerging contaminants (e.g., estrogens). This work highlights the utility and potential of TiO2-based photoelectrocatalysis for both monitoring and treating changing source waters and provides impact to users interested in the capabilities of this versatile technology.

Co-Authors: Irene Carra, Peter Jarvis, Olivier Autin, Emma Goslan, Pablo Campo Moreno

The UV/chlorine advanced oxidation process (AOP) is a promising alternative to the conventional UV/hydrogen peroxide (UV/H2O2) process due to the availability of chlorine disinfectants, like hypochlorite (HOCl), at water treatment works. Chlorine photolysis also generates reactive chlorine species (RCS) in addition to hydroxyl radicals (HO●). UV/chlorine is also compatible for use with UV-LEDs as these can be configured to emit light at wavelengths compatible for photolysis of chlorine. UV-LEDs allow for flexible reactor design and operation compared to conventional mercury lamps. However, chlorine photolysis is also influenced by pH since aqueous chlorine dissociates into HClO or ClO-, depending on pH and each of these species has different absorption properties. There is lack of studies that account for the synergistic impact of wavelength of irradiation and pH on radical composition and yield when comparing UV/HOCl and UV/H2O2 AOPs. How these AOPs differ in terms of transformation pathways and by-products of pesticide degradation is yet to be studied.

Bench scale AOP tests were conducted to compare the degradation of 5 persistent pesticides in the UV/chlorine and the UV/H2O2 processes. Pesticides were selected based on occurrence and for representation of different reactivities towards the various radicals produced. Operating conditions such as, choice of oxidant, wavelength of irradiation and pH, were varied to evaluate their impact on radical production and pesticide degradation. The transformation products were identified, and transformation pathways were compared between the AOPs. The results of this study will provide a detailed comparison of UV/Chlorine and UV/H2O2 technologies and allow for a better understanding of the upstream and downstream processes required for the successful application of UV/chlorine AOPs for drinking water treatment.

Co-Authors: Mark Hernandez

Airborne allergens pose unique indoor air quality challenges; of these, house dust mites (HDM) produce a variety of immunogenic antigens including Der p1, a water-soluble cysteine protease, which is a major component of HDM excrement. Der p1 can trigger allergenic and hypersensitivity responses during both tactile and aerosol (respiratory) contact. The Der p1 protein conformation is specifically recognized by mammalian immune systems in ways that result in a broad variety of atopic responses. Der p1 structure is essential in facilitating pro-inflammatory functions; thus, disrupting this protein’s conformation represents a treatment strategy for reducing the negative health effects associated with Der p1 exposures.

In response, experiments were conducted to disrupt the protein conformation of Der p1 containing aerosols, using commercially available Far-UVC (UV222) equipment designed for indoor use. Following its extraction from HDM excrements, Der p1 was aerosolized with water in a respirable size range (0.5 – 5.0 um) and contained in well-mixed, humidity-controlled chambers (1 and 10 cubic meters). Every ten minutes, aerosol containing Der p1 was collected using condensation growth tube samplers. Serial experiments compared Der p1 epitope recognition in aerosols recovered from otherwise identical chamber conditions (RH, temperature, light) in the presence and absence of UV222 exposure. As judged by Enzyme Linked Immunosorbent Assay (ELISA) of aerosol condensates, the half-life of airborne Der p1 epitopes that could be recognized by monoclonal antibodies following continuous UV222 exposure, was 20 minutes at 60% relative humidity. These results suggest that UV222 may be applied to inactivate airborne allergens by disrupting their conformational structure, in time frames relevant to common indoor air exchange rates.

Co-Authors: n/a

Since 1953 NALMCO® (international Association of Lighting Management Companies) has been committed to raising the professional level of its members and the performance of lighting systems by providing education, certification and networking opportunities for the lighting industry. NALMCO was the first organization in the lighting industry to create nationally recognized professional certifications addressing lighting management.

NALMCO recognizes that system design, commissioning and operation are crucial to the safe and effective operation of GUV systems. Maintaining GUV systems over time and working safely in spaces with GUV systems are important reasons to develop recognized certifications. Uniform training and certifications are needed to demonstrate the ability to provide a safe facility and to maintain the appropriate levels of GUV disinfection and compliance with any Federal or State regulatory requirements.

In response to this need, NALMCO, is actively working with IUVA, IES and ASHRAE and alongside industry experts, to develop three nationally recognized UV certifications - An Apprentice GUV technician, Senior GUV technician and Certified GUV management consultant. Our proposal is to present an overview of our certification program and its curriculum, and the implementation plan and schedule for its roll-out. The presentation will conclude with an invitation for other to join us, and adapt it to other regulatory requirements in non-US applications.

Co-Authors: Tina Beck Hansen, Lisbeth Truelstrup Hansen

Authors: Kasper Espekvist, Tina Beck Hansen, Lisbeth Truelstrup Hansen Title: Milk fats influence the germicidal effect of UV-C treatment of milk Research focus: Food microbiology and hygiene Institution: The Technical University of Denmark

The germicidal potential of treating milk with UV-C is well described in scientific literature, for a range of different reactor types. Less attention has been given to the influence of the composition of the milk on the effect of the UV-C treatment. For a dairy transition from traditional pasteurization to UV-C treatment, this knowledge is a pre-requisite.

Previously stated issue has been examined using a novel spiral-wound UV-C reactor, the design and scale of which is close to industrial. Different types of milk, with different levels of fat (0.1 – 8.0 %), were separately spiked with Pseudomonas fluorescens and Lactococcus cremoris, and subsequently treated with a range of UV-C doses (0 – 110 W/m2, UV-C lamp output). The UV-C sensitivity of the bacteria were determined using a collimated beam apparatus (1.5 mJ/cm2 for both organisms for a 1 log reduction). Mathematical models based on bio-dosimetry were used to quantify the influence of fat on the germicidal effect of UV-C.

Experimental results showed increased fat content lowers the germicidal effect of UV-C treatment, in the most extreme cases tested, requiring double UV-C dose for attaining identical bacterial reductions. This knowledge is important, as it impacts where UV-C can potentially be placed on a dairy processing line, i.e., before or after cream separation, homogenization, standardization etc., and it aids in determining adequate UV-C doses, for reaching a specific desired germicidal effect.

Co-Authors: Itay Belfer

The accumulation of microorganisms on membrane surfaces, known as biofouling, can lead to reduced performance and shortened RO lifespan. This phenomenon results in rapid increase in DP (differential pressure), frequent CIP and higher energy consumption. Moreover, biofouling can cause permanent damage to the membrane, requiring expensive replacements and causing downtime. Current methods to prevent biofouling such as biocides, can be costly and potentially harmful to human and the environment, and don't always solve the problem.

Traditionally, Atlantium technology was supplying medium pressure HOD-UV systems with high energy consumption, for a chemical dechlorination, and this was used as an alternative technology for sodium bi sulfite (SBS) or carbon filter prior to RO membranes. The feedback obtained from clients was very positive - not only did the dechlorination process was achieved by the UV but also it influenced the RO membrane performance, mainly extending the time between CIP procedures and cartridge filters replacement. Following this feedback, Atlantium carried extensive fundamental research to quantify the influence of a RO pre-treatment using a small MPUV system for disinfection. Results showed that RO surface had less biofouling and less EPS (extracellular polymeric substances). The next step was field installations.

A 100,000 m³/day seawater reverse osmosis (SWRO) facility undertook a comparative study to evaluate the disinfection efficacy of a novel hydro-optic ultraviolet (HODTM-UV) technology to provide enhanced protection of the RO elements and positively affect overall RO system, maintenance procedures and facility performance.

Prior to HOD-UV installation, the plant experienced frequent RO clean-in-place (CIP) events as well as frequent Cartridge filters (CF) replacement. Following the installation of HOD-UV, the facility experienced a 40% decrease in CIP frequency and a 65% decrease in the number of micron filter replacement events, leading to a 4.8% and 7.7% cost savings, respectively. Membrane performance also improved: there was a 21% decrease in post-CIP differential pressure (DP) and a 5% increase in total membrane permeate quantity with the use of the hydro-optic UV technology.

Co-Authors: Stephanie Gora, Rich Simons, Ben Ma, Paul Westerhoff, Karl Linden, Benoit Barbeau, Hamed Torkzadeh, Mariana Lanzarini-Lopes, Zhe Zhao, Graham Gagnon, Christian Matthews, Dana Pousty

Biofilms are often problematic in water and wastewater infrastructure, the food industry, and healthcare settings, as biofilms can cause fouling and corrosion and can serve as a harbor and source of pathogens. Given the efficacy of UV disinfection against all classes of microorganisms and the recent developments in UV technology, especially in UV light emitting diodes (LEDs) and excimer lamps, UV has the potential to be an effective and sustainable approach to control biofilms in various engineered settings. There is a need for a more comprehensive understanding of the mechanisms and potential applications of the technology as well as a consistent terminology framework to ensure that… The IUVA Task Force on UV for Biofilm Control reviewed and summarized the current knowledge regarding biofilm control with UV light and evaluated the experimental designs and methods used in previous studies, including biofilm growth conditions, UV exposure protocols, and biofilm extraction and quantification. A recommended terminology was defined to categorize four categories describing the different ways that UV can interact with biofilms. Research gaps and future directions were also identified, such as comparison of UV device configurations (pretreatment vs. direct exposure), exposure schemes (continuous vs. cycling), evaluation of the combined impacts of UV and water matrix effects on biofilm physical/chemical characteristics and the biofilm microbiome and understanding the mechanisms for the UV resistance of biofilms across UV wavelengths. In addition, potential challenges of UV applications for biofilm control were discussed, including energy consumption, performance monitoring, device maintenance, and regulation. In sum, this IUVA Task Force document provides a comprehensive overview of the current state of knowledge related to biofilm control with UV light and recommendations and guidance for future research directions and experimental practices, all of which will be presented and discussed.

Co-Authors: Amina Stoddart, Sean MacIsaac

The outputs of UV LEDs have drastically improved over the last five years and are on track to continue to improve throughout the decade. Recent work using the UV Auditing approach has suggested that 280nm UV LED disinfection achieves an equivalent level of disinfection compared to conventional UV systems at a third of the delivered fluence when using real wastewater. Considering the system efficiency of UV LED disinfection is a key factor that encompasses both wall-plug efficiency and the overall savings in labour and delivered fluence. A 100 GPM, 280nm UV LED wastewater system has been installed in parallel to a conventional open channel UV disinfection system at a facility in Halifax, Nova Scotia. This presentation will present evidence as how UV LEDs are able to be highly effective at disinfection in wastewater and capture the potential of UV LEDs in a first-ever study at this scale. The presentation will address study plan for the pilot-assessment and as appropriate, provide preliminary sampling and data collection which will inform the performance, operational costs, and fouling susceptibility of high-capacity UV LED reactors in both drinking water and wastewater settings. This work is vital for understanding how to further scale this technology and identify the key factors when comparing LEDs to conventional systems.

Co-Authors: Remis Gaska, Igor Agafonov, Steven Britz, Yuri Bilenko, F. C. Thomas Allnutt

We report on the impact of illumination using UV-C and UV-B LEDs with peak emission wavelength shorter than 300 nm on the surface disinfection/cleaning. Our study focused on the eradication of microorganisms over the surfaces of irregularly-shaped objects by optimizing combination of optical and electro-mechanical designs, and active bio-response in order to avoid shadowing effects.

We will present testing results on the survival of bacteria on passive surfaces such as Hearing Aid Devices (HADs), AirPods, Earbuds, etc. and suppression of mold buildup on bio-active surfaces such as fresh produce.

Testing of passive surface disinfection was performed for a compact, pocket-sized (diameter 90 mm, height 30 mm) devices that used a single 270 nm – 280 nm UV-C LED with optical output power of approximately 1.5 mW at 20 mA current. Initial germicidal efficiency of the devices was evaluated by testing the eradication of common skin bacteria Bacillus cereus and Staphylococcus epidemidis adsorbed to a surface of HAD after constant UV-C illumination for up to 2 hours. The most probable number method was used for quantification of bacterial loads on UV-treated and untreated (control) HADs. Reproducible 99.9% eradication of both bacterial strains for all-in-ear HADs was demonstrated after 20 minutes exposure, while 99.99% kill was achieved after 1 hour exposure. These results demonstrated the potential of compact, robust and low-power consumption UV-C LED-based disinfection devices.

Our results demonstrated that while disinfection of passive surfaces required a uniform 360o exposure with UV-C LED emission, the combination of UV-C/UV-B illumination in the range of 280 nm – 300 nm LED emission stimulated active bio-response in fresh produce, such as strawberries, which enabled a uniform suppression of mold buildup (self-cleaning) by only partial surface exposure.

Co-Authors: Mark Gerber, MD Leo Schowalter, PhD

We have developed a UVC phototherapy platform that addresses the global crisis of antibiotic resistance in non-healing wounds. The World Health Organization (W.H.O.) has stated that the current growing crisis of antibiotic resistance threatens to undo a century of medical progress. (1). In the United States alone there are 2 million people who suffer with antibiotic resistant infections (2). The ability of pathogens to defeat existing antibiotics outpaces the development of new antibiotics to combat these threats. Therefore, the global healthcare community is searching for alternatives to traditional antibiotics.

Our phototherapy platform, which uses UVC LEDs (supplied by Crystal IS, Inc.), has achieved disinfection results which could be used as an effective alternative to antibiotics. In adult swine, we created a Methicillin-Resistant Staph Aureus (MRSA) cellulitis (Element labs CFU 5.05 X 108). After 24 hours, we exposed the cellulitis to phototherapy. We achieved a 94% decrease in colony forming units (CFUs) in 60 seconds (60mJ/cm2). Following an additional 250 seconds of exposure (total 310mJ/cm2) we achieved >97% decrease in CFUs. Further, by measuring Cyclobutane Pyrimidine Dimer formation, we found that our device, has a less detrimental effect on host tissue compared with the longer wavelength (265nm) UVC LEDs (figure 2), even though the efficacy of the 235nm against infection appeared comparable to 265nm radiation. At the same time, 235nm radiation has a greater penetration depth than 222nm radiation and, thus, may more effective against biofilms as in this application. (Data, charts and graphs available)

Co-Authors: Leo Schowalter

We have developed a UVC phototherapy platform that addresses the global crisis of antibiotic resistance in non-healing wounds. The World Health Organization (W.H.O.) has stated that the current growing crisis of antibiotic resistance threatens to undo a century of medical progress. (1). In the United States alone there are 2 million people who suffer with antibiotic resistant infections (2). The ability of pathogens to defeat existing antibiotics outpaces the development of new antibiotics to combat these threats. Therefore, the global healthcare community is searching for alternatives to traditional antibiotics.

Our phototherapy platform, which uses UVC LEDs (supplied by Crystal IS, Inc.3), has achieved disinfection results which could be used as an effective alternative to antibiotics. In adult swine, we created a Methicillin-Resistant Staph Aureus (MRSA) cellulitis (Element labs CFU 5.05 X 108). After 24 hours, we exposed the cellulitis to phototherapy. We achieved a 94% decrease in colony forming units (CFUs) in 60 seconds (60mJ/cm2). Following an additional 250 seconds of exposure (total 310mJ/cm2) we achieved >97% decrease in CFUs. Further, by measuring Cyclobutane Pyrimidine Dimer formation, we found that our device, has a less detrimental effect on host tissue compared with the longer wavelength (265nm) UVC LEDs even though the efficacy of the 235nm against infection appeared comparable to 265nm radiation. In addition, 265nm exposure produced CPDs at a greater depth in host tissue extending into the dermis. At the same time, 235nm radiation has a greater biofilm penetration depth than 222nm radiation and, thus, may more effective against biofilms as in this application.

(1)Director General WHO statement June 2019

(2)February 14, 2020 statement

Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Division of Healthcare Quality Promotion

(3)Optan 235 LEDs supplied by Crystal IS, Inc.

Supported in part by the Asahi Kasei Corporation under the UV Accelerator Program (www.uvaccelerator.com)

**Founder Crystal IS; now retired

Co-Authors: none

A highly desirable UVC disinfection system verification and maintenance goal remains unfilled. It is to be able to determine, essentially in real time, consistently, and accurately that the total UVC exposure received by air flowing through a duct or in the upper portions, or potentially the entire volume of an occupied room, by an object placed in a sanitation enclosure, on target surfaces exposed by a mobile UVC unit, or flowing water through a water treatment reactor has been adequate to achieve the requisite level of disinfection. Measuring, communicating, and documenting that the ability of the system to inactivate a standard group of unclumped, test pathogens to a designed level is desired and its accuracy would rely on indicating the actual integrated UVC dose received by recognized standard challenge pathogen such as the endospore of Bacillus subtilis which is not infectious in the vegetated state and is typically used for validation testing. Given the stated goal, a bio-photonic method, based upon Established UV excited green photo-luminescence from Tb3+ lanthanide-DPA, which can quickly determine the fraction of test endospores that survive exposure to the UVC or FarUV dose, the delivery mechanism and delivery of the technique, in the form of a Biological Indicator vial, as well as a design for a fast counter, will be introduced allowing evaluation and certification of system performance confirming efficacy, and, in the case of FarUV exposure, also that the desired level of human exposure has not been exceeded.

Co-Authors: Zhimin Fu, Junhua Wang & Keyu He

Since the outbreak of COVID-19, the problem of microbial transmission caused by indoor air has become the focus of attention. Ultraviolet (UV), as an efficient and safe air disinfection and sterilization technology, has been widely used, but how to use UV in central air conditioning environment is still controversial. In this paper, the experimental method was used to study the germicidal efficiency of ultraviolet sterilization (UVGI) device when air passed through the air duct section at one time. The results show that when the size of the air duct is 500*250mm and the U-shaped UV lamp is arranged perpendicular to the air flow direction, the germicidal efficiency will decrease significantly with the increase of wind speed. When the UV lamp is arranged in the air duct, the more suitable wind speed should be 1-3m/s. When the ratio of UV lamp power (w) to air volume (m3/h) reaches 1.67, the one-time sterilization efficiency can reach more than 90%. The germicidal efficiency of the ultraviolet sterilization device decreases with the increase of particle size. The partial correlation analysis between sampling particle size and germicidal efficiency shows that the particles of 0.65-4.7 μm are sensitive to ultraviolet radiation. The combination of 75w ultraviolet disinfection device and electrostatic adsorption filter can achieve 99.7% germicidal efficiency at 3m/s wind speed.

Co-Authors: Zhimin Fu, Ziyang Ou, Junhua Wang & Keyu He

Using ultraviolet (UV) light for rapid disinfection of central air conditioning ventilation is an important research direction in the field of UV technology. It aims to achieve the one-time elimination of pathogenic microorganisms, preventing cross-contamination of microorganisms across different areas. Additionally, it rapidly reduces the concentration of pathogenic microorganisms in enclosed spaces and minimizes the possibility of cross-infection among occupants. Low-pressure UV lamps have been partially utilized in central air conditioning ventilation systems and air purification disinfection devices for air disinfection. However, achieving the goal of the one-time elimination of pathogenic microorganisms has been challenging. The efficiency of low-pressure UV lamps varies significantly due to changes in air temperature, airflow speed, pipe wall temperature, and mercury vapor pressure inside the lamps. The output efficiency and power of 254 nm UV radiation vary greatly with these factors. Traditional low-pressure UV lamps designed for static radiation disinfection exhibit low UV output efficiency and unstable disinfection effects in ventilation systems, hindering their application in ventilation disinfection. This paper focuses on the application of low-pressure UV lamps for disinfection in ventilation systems, optimizing the lamp design and conducting tests on the variation of UV output under constant current operation with changing air temperature and airflow velocity. Two arrangements of low-pressure UV lamps were investigated: parallel and perpendicular to the axis of airflow. The concept of an environmental coefficient for low-pressure UV lamps in ventilation disinfection was proposed. Matching the UV light and airflow fields is important for applying low-pressure UV lamps in ventilation disinfection. This study aims to improve the UV output efficiency of low-pressure UV lamps in ventilation disinfection, achieve stable disinfection effects, and reduce the construction cost and operational energy consumption of the disinfection system.

Co-Authors: Amy Hedrick, other work referenced

It is important to understand that UVC’s effectiveness at eradicating a contagion on surfaces without damaging materials or humans is dependent on: 1. The form factor in which UVC is generated; 2. Nanometer wavelength; 3. Intensity; 4. Distance from surface; 5. Radius of coverage; 6. Length of exposure; and 7. Substance being decontaminated (air, water, surface).

There are a large variety of reflective surfaces, which vary in effectiveness. Mirrors are one of the least effective reflective surfaces because they reflect the light too precisely. Other materials (like aluminum) bounce light in a more distributed pattern, which makes them more likely to fill an area with light, making them more useful. The trade-off is often evaluating how much light the reflective surface actually absorbs and finding a material that reflects all or most of the light while dispersing it outward in all directions. These reflective materials do exist, but because of their cost, most UVC devices currently on the market do not utilize them.

Non-precise application of reflectivity for UVC decontamination applications is generally ineffective. However, reflectivity can be used to great purpose with: a) short distances, and; b) the correct reflective materials. (11)

The premise is to discuss how UVC LEDs can be utilized for a better targeted surface decontamination for multiple types of materials including semi-porous and non-hard, or non-continuous surfaces.

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

Micropollutants, even at trace concentrations, have raised great concerns because of their harmful impacts on ecological safety and human health. In recent years, UV-AOPs have drawn increasing attention because they can produce highly reactive radicals to quickly degrade most micropollutants. In typical UV-AOPs, the selection of a proper process (e.g., UV/hydrogen peroxide, UV/chlorine and UV/peroxydisulfate) and optimization of treatment conditions (e.g., UV fluence and reagent dose) are crucial for improving efficiency and saving costs.

This study developed a facilitated prediction method of photon fluence-based rate constant for micropollutant degradation (k′p,MP) in various UV-AOPs by combining model simulation with portable measurement. The simulation involved photochemical, quantitative structure-activity relationship, and radical concentration steady-state approximation models. Portable measurement was employed to quantify the scavenging capacities of principal reactive radicals (RRSCs) involved in UV-AOPs (i.e., HO•, SO4• and Cl•) by using a mini-fluidic photoreaction system (MFPS). The RRSCs of eight test waters were determined, which exhibited a good correlation with water matrices and reaction selectivities of reactive radicals. We then used sulfamethazine, caffeine, and carbamazepine as model micropollutants. Their k′p,MP values in various UV-AOPs were predicted and further verified experimentally.

Besides the removal efficiency of micropollutants, the cost should be also considered for the selection and optimization of UV-AOPs. We developed an electrical energy consumption per order (EEO) prediction method for multi-scale UV-AOP reactors for micropollutant removal in water. The method utilizes the rate constants determined in a reference reactor (e.g., MFPS) to facilitatively predict the EEO of a full-scale reactor by a scale-up method that describes the dependence of EEO on reactor properties (e.g., the lamp power, incident UV photon flux, and effective optical path-length). The developed method presents acceptable accuracy, convenience, and low cost, which facilitates the process selection and optimization of UV-AOPs and essential for increasing efficiency and cost-effectiveness in practical UV-AOP applications for water treatment.

Co-Authors: Dr. Ulf Meiners1*, Shigeharu Yamauchi2, Takeshi Tanaka2, Jonatan Klee1, Menno Schake l1, Masaaki Tsunano1

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: Tatiana Koutchma, Agriculture and Agri-Food Canada Michael D. Tiberi, Deep Light Photonics, CA, USA Vladimir Popovic, Agriculture and Agri-Food Canada Asma Rahman, Agriculture and Agri-Food Canada

Cathode ray or electron UV tubes are the next generation of pulsed light UVC (eUVC) technology that uses luminescent phosphors to produce germicidal UVC photons. eUVC® tubes use an electron beam in a vacuum glass envelope to excite a proprietary mixture of phosphors that produce polychromatic, pulsed UVC emission with peaks at 232, 242, 261, and 272 nm. Electron pulsed UV lamps have potential advantages for mitigating the risk of microbial and chemical contamination in food applications because of combined action of at least 4 wavelengths, shorter treatment time, low energy consumption and cost. The efficacy of the eUV-7p lamps was measured for two cases: ability to inactivate UV resistant Escherichia coli P36 strain and degrade deoxynivalenol (DON) mycotoxin with an absorption maximum at 221 nm.

The eUVC efficacy was compared with continuous UVC treatments at 222 nm (excimer lamp), 254 nm (low pressure mercury) and 275 nm (UV-LED) via evaluation of kinetic inactivation parameters and photoreactivation of E. coli P36 after exposure to equivalent fluence conditions in saline. The treatment of DON was performed after spiking 100 ppm of DON on the surface of filter paper. From the four tested UV sources, the lowest fluence required to achieve 1-log and 5-log reductions of E. coli was observed using the eUVC lamps (0.9 and 1.4 mJ/cm2, respectively) followed by 277, 253.7, and 222 nm wavelengths. The lowest photo-reactivation of UV inactivated cells was observed following a 3 h treatment using 222 nm light followed by eUVC, 253.7, and 277 nm. In the case of DON reduction on filter paper, eUVC was the most effective followed by 222, 253.7, and 277 nm. Testing of eUVC lamps continues in continuous treatment mode using UV processing conveyor and will be presented in details

Co-Authors: Maksym Bazhal, National University of Food Technologies (NUFT), Ukraine Tatiana Koutchma, Agriculture and Agri-Food Canada Richard M. Mariita, Crystal IS, an Asahi Kasei Company, USA

The ongoing war in Ukraine has left millions of civilians without access to safe drinking water and power. Destruction and restricted access to water had led people to drink water from lakes, rivers, old wells, and other unsafe water sources. In this crisis, applying germicidal Ultraviolet (UVC) light generated by light-emitting diodes (LEDs) that is highly effective against general microflora and water-borne pathogenic organisms can be a simple solution. UV LEDs disinfection units can be easily installed as plug-and-play water treatment systems for point-of-use applications.

Crystal IS (NY, USA) donated ten Klaran UVC LEDs systems and supported the NUFT of Ukraine for assessment of design solutions and requirements for water treatment from unconventional water sources. A mobile UVC LED 265 nm kit for individuals and small groups has been developed and tested in Ukraine. The kit consists of the manual water sprayer, three filters (mechanical – carbon - mechanical), UVC LED system and a power supply unit. Three types of power supplies were trialed: standard 220 VAC, universal unit (battery 12 VDC, 24 VDC), power bank (15 W at 5, 9, 12 VDC). The throughput of the kit is 1-2 l/min. The basic set-up can be easily changed according to the customer's specific requirements.

The initial tests validated microbiological efficacy against Irpen River microflora with initial turbidity levels of 1.6 NTU. The succession of filters greatly affected the turbidity of water entering the UVC LED reactor and, consequently, the microbial reduction. The most favorable conditions were observed when combining a standard mechanical filter (1 μm) followed by the carbon filter (5 μm) and mechanical filter (1 μm) that resulted in a reduction of the initial total microbial count of ~ 5.9 logs up to 2.4 logs after treatment. Approaches to reduce turbidity from 1.6 NTU followed by more tests are currently being conducted to determine the most effective solution design to achieve drinking water quality equivalent to the quality of water recognized by Ukraine regulations.

Co-Authors: none

Infection Prevention and Ultraviolet Air Disinfection Technologies: Performance and Economics Air disinfection is the focus of much current research in the wake of the COVID pandemic. Ultraviolet (UV) technologies provide the most cost-effective solution to the transmission of respiratory and other diseases in the indoor environment. These UV technologies include In-duct air disinfection, Upper Room air disinfection, portable recirculation units, and whole room (Far-UV) disinfection systems. The performance of these air cleaning systems can be placed on a common basis for comparison using equivalent air changes (EACs). Standardized performance tests from AHAM, ASTM, ASHRAE, ISO and EPA are available for evaluating air cleaners and their performance is measured in terms of disinfection efficiency and airflow. The EAC is computed directly from the measured performance parameters and is based on a model room in which the air is completely mixed. The amount of outside air, or non-infectious air, brought into a room establishes the removal rate of airborne contaminants. The performance of a UV air cleaner is defined by the removal rate of outside air at an ACH equal to the air cleaner EAC. Two types of test results are evaluated, 1) In-duct testing and, 2) testing in a model room under steady state conditions. Once the EAC is defined for each type of UV air cleaner, the cost of implementation per unit EAC can be compared. Quantitative risk assessment is performed by evaluating the risk reduction of each technology compared to a baseline of outside airflow under natural ventilation, or 0.35 ACH, using the Wells-Riley model. Results indicate the highest performance levels are achieved by In-duct UV air disinfection and that this technology has the lowest possible costs. Combinations of In-duct UV and filtration are also shown to be the most cost-effective approach for the broadest range of pathogens.

Co-Authors: No

Infection Prevention and Ultraviolet Air Disinfection Technologies: Performance and Economics Air disinfection is the focus of much current research in the wake of the COVID pandemic. Ultraviolet (UV) technologies provide the most cost-effective solution to the transmission of respiratory and other diseases in the indoor environment. These UV technologies include In-duct air disinfection, Upper Room air disinfection, portable recirculation units, and whole room (Far-UV) disinfection systems. The performance of these air cleaning systems can be placed on a common basis for comparison using equivalent air changes (EACs). Standardized performance tests from AHAM, ASTM, ASHRAE, ISO and EPA are available for evaluating air cleaners and their performance is measured in terms of disinfection efficiency and airflow. The EAC is computed directly from the measured performance parameters and is based on a model room in which the air is completely mixed. The amount of outside air, or non-infectious air, brought into a room establishes the removal rate of airborne contaminants. The performance of a UV air cleaner is defined by the removal rate of outside air at an ACH equal to the air cleaner EAC. Two types of test results are evaluated, 1) In-duct testing and, 2) testing in a model room under steady state conditions. Once the EAC is defined for each type of UV air cleaner, the cost of implementation per unit EAC can be compared. Quantitative risk assessment is performed by evaluating the risk reduction of each technology compared to a baseline of outside airflow under natural ventilation, or 0.35 ACH, using the Wells-Riley model. Results indicate the highest performance levels are achieved by In-duct UV air disinfection and that this technology has the lowest possible costs. Combinations of In-duct UV and filtration are also shown to be the most cost-effective approach for the broadest range of pathogens.

Co-Authors: N/A

The potential to use UV-C LEDs in the treatment of water has long promised all the benefits of UV disinfection; absence of chemicals, ease of use, pathogen specific targeting. All without the drawbacks of mercury-lamp technology; warm-up time, on/off cycling limitations, heavy metal contamination risk. The commercialization of this technology has been documented at a Point-Of-Use and Point-Of-Entry scale applications over the past few years and continues to show growth. A number of these smaller commercial UV-C LED system are listed under NSF-55 certification and other national standards in the UK, France, etc.

The question therefore arises, is when and how will this technology scale to larger industrial and municipal applications? Is it possible to overcome the barriers of relatively high-cost/low-efficiency LED devices, new UV system engineered solutions and regulatory barriers for these larger flow applications.

This paper will give an overview of some of the UV-C LED technology projects currently in progress within the larger flow rate ranges. It will provide application goals and performance results as far as possible. It will also outline the challenges and advantages that have been seen. The case studies include:

United Utilities – Typhon Treatment -Municipal Drinking Water, United Kingdom -28 MLD (5,072 USGPM)

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

Metawater Pilot -Drinking Water, Japan -55 gpm to 300 gpm

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

CU 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 -Water Discharge, Canada -To compare existing LP UV system with LED UV system

Co-Authors: None

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. Previously, I presented an overview of the theoretical merits of the CV approach, including aspects related to non-linear microbial kinetics and the theory associated with putting reactors in series. In this presentation I will focus on the merits of the CV equation itself. While the CV model was developed heuristically rather than analytically, here I use mathematical approximations and numerically generated data to provide justification for the CV model. Furthermore, I explore scenarios where the approach is not valid and show that these “non-performing” cases are identified with current protocols of USEPA UV disinfection guidelines.

Co-Authors: TAEJOON CHOI, JIHAN KIM, SEUNGMOON BAEK

Recently, as interest in air sterilization and water treatment using UV-C ultraviolet light sources increases, the need for new light sources with high power and high efficiency characteristics is increasing.

We developed a 1.3-inch vacuum sealing lamp system using cathodoluminescence(CL)-based UV-C light emitting phosphor synthesis technology and carbon nanotube (CNT) field emission source manufacturing technology.

The anode has a 1 mm-thick sapphire substrate and a 20 µm-thick UV-C layer(YLaPO4:Pr) and an 300 nm-thick aluminum (Al) electrode.

Field emitters were prepared through a simple and cost-effective screen-printing process. The CNT paste was synthesized by mixing the arc-discharged MWCNT powder.

A screen printing machine was used to print the mechanically well-dispersed CNT paste over the surface of 1-inch metal substrate by forcing it through a patterned stencil in order to form the desired arrays of CNT dots with a diameter of 350 µm. A flat 1.3 inch UV-light-source tube-based triode structure operating at 273 nm with a DC voltage operating mode was achieved by integrating the UV-C light emitting phosphor as a CL layer and CNT field emitters. In addition, high voltage driving power development and insulation molding and instrument design development were carried out for empirical commercialization.

In the future, we will focus on developing sterilization clinical tests and mass production technologies for actual product testing in various spaces.

Co-Authors: Karl G. Linden, Sara Hayoune, Emma Payne

UV - based advanced oxidation processes (UV/AOPs) have high potential in treating many recalcitrant organic water contaminants. However, to realize its full potential, the technology must overcome some key mechanistic drawbacks, principally the low concentration of the main active oxidant - •OH radical. A possible solution is the use of a new UV source: krypton chloride (KrCl*) excimer lamp, which emits narrow-band UV light at 222 nm. This wavelength strongly overlaps absorption spectra of common •OH promoters, potentially enhancing radicals’ formation and improving contaminants removal.

The goal of this study was to determine the effectiveness of UV/H2O2, based on KrCl* excimer 222 nm UV lamp, for treating 1,4 – dioxane, a notorious groundwater contaminant, frequently detected in sites impacted by industrial wastewater. Results showed that UV/H2O2 degradation of the contaminant in DI, using KrCl*, was up to ninefold faster than its degradation with both low-pressure and medium pressure Hg lamps, commonly used for water treatment. However, degradation was highly affected by non-target light absorbing water constituents, specifically natural organic matter and nitrate (while marginally affected by carbonates). For example, addition of up to 5 mg/L-N nitrate to the water decreased 1,4 – dioxane degradation rate by one order of magnitude. Considering other important factors such as the enhanced formation of nitrite under short wavelength, lead to the conclusion that KrCl*/H2O2 can be an attractive alternative to Hg UV lamps mostly for treating water with low levels of nitrate and organic matter.

Co-Authors: Mengkai Li, Jiale Wang, Xingjia Gao, 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. The performance of a UV reactor depends on the UV fluence (or UV dose). The combination of a spatial photon fluence rate (PFR) distribution (i.e., Optical field) and computational fluid dynamics is necessary to obtain the UV fluence of a UV reactor[1], as well as the configuration of a UV reactor for optimal efficiency (e.g., increase the reflection of the reactor inner-wall). Therefore, an accurate quantification of the spatial PFR distribution is significant. However, this work has not been well studied for UV-LED reactor.

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 [2]. 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. At first, the PFR distribution of a single UV-LED chip was measured in the air, which not only validated the PFR distribution model of UV-LED, but also measured the output power of a single UV-LED chip. Then, the PFR distribution of a UV-LED reactor filled with water with various UV transmittances were measured. The impact of water UVT and inner wall reflection were examined. This work provides significant results for the optimal design and high-efficacy operation of a UV reactor.

References

[1]J. R. Bolton, Water Research, 34(13), 3315-3324 (2000)

[2]M.K. Li, Z.M. Qiang, T.G. Li, J.R. Bolton, C.L. Liu, Environmental Science & Technology, 45(7), 3034-3039 (2011)

[3]M.K. Li, Z.M. Qiang, C. Wang, J.R. Bolton, E.R. Blatchley III, Environmental Science & Technology, 51(6), 3453-3460 (2017)

[4]M.K. Li, Z.M. Qiang, J.R. Bolton, W.W. Ben, Water Research, 46(11), 3595-3602 (2012)

[5]M.K. Li, Z.M. Qiang, J.R. Bolton, Chemical Engineering Journal, 214, 55-62 (2013)

Co-Authors: Lauren Mullen, E. Michael Thurman, Imma Ferrer, Emma Payne, Karl G. Linden

KrCl* excimer lamps, emitting UV in the far-UVC range (200-222 nm) has been shown to effectively kill pathogens in air and water while remaining relatively harmless to human skin and eyes. However, limited studies have investigated the use of KrCl* excimer lamps for UV/advanced oxidation processes (AOPs) in comparison to conventional mercury-based lamps.

Here, we compared contaminant degradation between LPUV and KrCl* excimer lamps for both carbamazepine (CBZ) and NDMA. The compounds were chosen based on their distinct quantum yield (Φ_CBZ=6×10^(-4) mol/Es,Φ_NDMA=0.25 mol/Es) at 254 nm and 2nd order reaction rate constants with •OH (k_(•OH/CBZ)=8.02×10^9 M^(-1) s^(-1),k_(•OH/NDMA)=3.30×10^8 M^(-1) s^(-1) ). Results illustrated that direct photolysis by KrCl* excimer lamps significantly improves the photolysis 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 upon addition of hydrogen peroxide, was able to further improve carbamazepine degradation compared to KrCl* excimer direct photolysis but didn’t improve the degradation of NDMA.

The degradation pathway of carbamazepine through direct photolysis of KrCl* excimer lamps in lab grade water was investigated utilizing high-resolution liquid chromatography mass spectrometry (LC/MS). Despite the absence of any radical promoters (i.e., hydrogen peroxide) present in the water, results demonstrated that both direct photolysis and hydroxyl radical-driven decay are involved in the degradation process as evidenced by •OH addition as part of the CBZ transformation. This indicates that a de facto AOP may occur when utilizing KrCl* excimer lamps for degradation of contaminants in water and can potentially be a cost-saving alternative to conventional LPUV.

Co-Authors: Dr.Natalie Hull

Nontuberculous mycobacteria (NTM) infection is a severe waterborne infectious disease. NTM have been found in municipally-treated water. Distinct colony morphotypes of NTM have different cell structure properties and therefore different resistance to disinfectants, which has given rise to the need to further explore mechanisms that underlie mycobacterial damage by ultraviolet (UV) radiation. This study is investigating the treatment efficiency of different UV wavelengths (222 nm emitted by a KrCl excimer lamp and 254 nm emitted by a low pressure Hg lamp) on inactivating and damaging genes of different NTM species and morphotypes. We are investigating non-pathogenic Mycobacterium smegmatis (ATCC 19420 and 14468) and morphotypes of pathogenic Mycobacterium avium-intracellulare (MAC) (smooth, rough and parent with mixed morphotypes). Efficacy of inactivation across UV doses is determined by plating. Long amplicon quantitative polymerase chain reaction (qPCR) is used to quantify the damage of hsp65 genes and rpoB genes. For growth patterns, M. Smegmatis grows faster than pathogenic MAC, and rough morphotypes of MAC grow slower than smooth and mixed morphotypes of MAC. For UV inactivation, pathogenic MAC species are more resistant than nonpathogenic M.Smegmatis. Preliminary results indicate that 254 nm wavelength results in less tailing than 222 nm at higher doses for inactivating of M. Smegmatis. Across both wavelengths, smooth morphotypes of MAC which have cell surface-associated glycopeptide lipids (GPL) were more sensitive than parent and rough morphotypes of MAC which lack GPL. The rate constants for the linear regions between M.Smegmatis and morphotypes of MAC are similar. DNA damage for M. Smegmatis increased with increasing doses for both wavelengths, and there was a significant increase from 16 mJ/cm2 to 40 mJ/cm2. This work will provide mechanistic knowledge on impact of UV wavelengths on NTM at cellular and molecular levels to address the challenge of waterborne opportunistic pathogens residing in water systems to inform UV treatment strategies.

Co-Authors: Asbjorn Husby, Duncan Colquhoun

Pasteurellosis in cold-water fish is a systemic infection caused by several different species and strains of bacteria belonging to the family Pasteurellaceae. Disease results in loss and reduced welfare in farmed salmon in Norway and Scotland, but has so far not been proven in salmon farming in other countries. Pasteurellosis is also a serious disease of farmed lumpfish in several countries.

Objective of the project is to obtain new knowledge about Pasteurella's sensitivity to various disinfectants and UV irradiation, and to suggest best-practice recommendations on disinfection as a key activity in the field of biosecurity measures in combating pasteurellosis in salmon production in the sea.

The aim of the work will be to determine optimal conditions for the implementation, operation and management of existing methods to prevent the introduction/reintroduction or effective removal of Pasteurella from salmon farming. It is important to determine the combination of disinfection methods and what doses are required to have the full effect of inactivation of Pasteurella in water and environment and the study will investigate the effect of different disinfection methods under different test conditions (temperature, particles, organic load).

Most of the UV systems used in Norway today are sized according to the requirements specified in Norwegian aquaculture regulations about disinfection of intake water to and wastewater from aquaculture facilities. These requirements are sufficient for the elimination of most bacteria and viruses in water, while higher doses are required for others. To find out more about Pasteurella's sensitivity to UV, we will use a Collimated Beam Device, for irradiation of Pasteurella suspensions with a variety of UV doses, with subsequent quantification by cultivation.

Co-Authors: Natalie Hull

UV LEDs hold great potential for distributed UV water disinfection. Hydropower from pressurized water systems can be harnessed to enable UV systems to operate off-grid, such as in water distribution systems or rural settings. Multi-wavelength UV can decrease electrical consumption and suppress bacterial regrowth. To inform implementing hydropower and multi-wavelength UV, collimated beam and flow through disinfection tests were performed with combinations of ~monochromatic (222 nm KrCl and 254 nm LP Hg lamps) and polychromatic (255, 265, 285 nm LEDs) UV sources. Synergistic disinfection of MS2 was observed with sequentially exposures by 222 nm or 254 nm followed by 285 nm when compared to predicted disinfection. However, synergistic disinfection of MS2 was not observed with sequential exposures of 255 nm followed by 265 nm or 285 nm. Calculated electrical energy per order (EEO) was lower for sequential exposures of MS2 by 222 or 254 nm with LEDs (<0.5 kWh/m3) than with dual LED wavelength (2-7 kWh/m3) and comparable to EEO for ~monochromatic UV disinfection (<0.2 kWh/m3). Synergistic disinfection was also observed for E. coli with 222 nm and UV LEDs were observed, indicating previous wavelength synergies with MS2 can be translated to E. coli. Hydropower UV may be feasible due to targeted wavelength disinfection and reduced power consumption. At point-of-use (POU) scale (<10 lpm), underperforming and inefficient water turbines did not supply adequate hydropower for UV LED disinfection. However, successful disinfection after incorporating a battery for energy storage indicates feasibility for intermittent disinfection. At point-of-entry (POE) scale (15-30 gpm), currently available hydropower turbines are efficient enough to power some UV LED and low-pressure UV systems. These studies provide vital information toward optimizing sequential UV to maximize disinfection efficiency and make the pipedream of hydropowered UV for POU/POE disinfection and biofilm control in water distribution systems a reality.

Co-Authors: None

Reliable monitoring of drinking water quality is necessary for achieving SDG 6. Still, standard monitoring approaches are too expensive to provide relevant data at the frequency and scale required in low- and middle-income countries (LMIC). Community-based monitoring (CBM), facilitated by advances in water quality sensor technology and information and communication technologies, offers promising prospects for a more cost-effective approach. Water quality information can improve water-related decision-making and increase demand for more effective water treatment at the household level. Evaluating UV LED disinfection systems' efficiency in rural areas is challenging due to infrequent monitoring efforts by government agencies and the community. These monitoring efforts typically involve collecting water samples and conducting expensive laboratory tests. We examined the prevalence of the different water treatment methods at the household practiced by the households. We asked the respondents to report whether and how they treat the water they obtain from the primary household source. Surprisingly the cases where E. coli was present in the water and unsafe to drink were not correlated to the respondent’s perception of their drinking water safety, emphasizing the importance of testing water and education in these settings. Implementing UV disinfection technologies necessitates a thorough understanding of the knowledge, attitudes, and practices associated with the technology before its implementation.

Co-Authors: John Barker and Rora Wisby

The use of viral surrogates has been a backbone for quantification of UV fluence in many of the global validation approaches. This is achieved by the calculation of Reduction Equivalent Fluence (REF) produced by comparing measured log reduction of surrogate using a Collimated Beam (where a UV Fluence can be calculated) to that of a measured log reduction that occurs through a reactor. Viral surrogates (generally bacteriophage) are often favoured as a surrogate or biodosimeter for many reasons including being able to propagate to a high concentration and a range of bacteriophages with differing UV sensitivity among numerous other reasons. Arguably however, the most desirable characteristic is that repeatable and nominally linear kinetics can be produced when plotted at a log scale. There are occasions published in literature whereby this is not the case and consequently might be undesirable for the validation of UV reactors. Findings into the study of well utilised bacteriophage T1, T1UV and MS2 and thier potential variability and non-linear kinetics are presented. The aim of study being to elucidate the cause for such responses as well as the impact on considerations for future UV validations.

Co-Authors: Ian Mayor-Smith

The development of validation documents has been critical to the application of UV disinfection reactors globally for water treatment. The German (DVGW) and Austrian (ÖNORM) protocols and later the United States EPA UV Disinfection Guidance Manual (UVDGM) guidance were pioneering approaches enabling different approaches for validation but ultimately confidence in end users’ disinfection application performance. The DVGW and ÖNORM protocols provided the initial defined standards specifically for supplementary disinfection with prescriptive details for a focussed application. The UVDGM in contrast provided a prescriptive approach to UV Validation for a wider range of disinfection applications. The majority of international guidance follows the foundations provided in these documents including the UK’s Drinking Water Inspectorate (DWI) guidance first released in 2010 and then updated in 2016. In 2018 the UK had the first UV LED reactor validated and put into service. The presentation will provide an update on the review of international validation approaches and how best practice has been incorporated into the updating of its current UV guidance and the production of a draft validation approach. As part of the draft validation specific approaches for LED reactors will be presented inclusive of fundamental quantification of LED sources providing a basis for a validation protocol for UV plasma lamp technology and LEDs alike.

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 viricidal power, a simple function of output and viricidal effectiveness. Though a good start, this does not address a major advantage and valid expectation of UVC LEDs, lifetime, and prolonged effectiveness.

Mercury lamps have dominated the disinfection market for years. They are cheap, have high optical output, and acceptable lifetime. However, form factors restrict design creativity, and with the global pressure to ban Mercury, including the Minamata Convention, continued global exemptions are uncertain. UVC LED is the solution. However, industries looking to incorporate UVC disinfection technology need LEDs that can replace mercury without taking a step backwards, ultimately exceeding the incumbent technology, as it did in backlighting, automotive, and general illumination applications. UVC LED output is increasing, and costs are decreasing as the technology scales. The missing piece is a metric to evaluate usable life. Enter Viricidal Maintenance. Nichia’s Mr. Todd Mikowski will introduce the subject of viricidal maintenance, the % of maintained viricidal power at a given time & conditions.

The generally accepted failure of an LED is when output reaches 70% of the initial measurement value. Testing has shown vast differences in LED-to-LED reliability, one element contributing to a lack of lifetime modeling not being established. Mr. Mikowski will demonstrate how virucidal maintenance, when paired with the conditions of the test, can provide an apples-to-apples comparison of UVC LEDs, allowing for proper pairing with application lifetime requirements. With UVC LED claims beginning to mimic the mistakes made in general illumination, now is the time for a metric geared toward reliability. Viricidal Maintenance can ensure honest reporting until suitable standardized testing/reporting can be developed.

Co-Authors: Benjamin Barrios and Benjamin Mohrhardt

Environmental water qualities and their impacts to human health present global challenges in addressing water and wastewater treatment strategies. Identifying the intermediates and transformation products induced by UV oxidation and in situ formed radicals in oxidative water treatment processes of micropollutants have been an active area of research. Reactive nitrogen species in UV-based water and wastewater oxidation processes play important roles because of the presence of nitrate and nitrite in source waters. Nitrated and nitrosated transformation products are of serious concerns due to their potential toxic and persistent nature. Toward understanding and predicting the oxidative transformation products in water and wastewater, this talk will emphasize the key progress made concerning the experimental and computational approaches to predict transformation products induced by UV photolysis and reactive nitrogen species. Case studies include UV photolysis of nitrate and nitrite at different wavelengths. Kinetic modeling demonstrates key differences induced by different UV wavelengths and provide mechanistic insight into reaction mechanisms for the formation of transformation products. Knowledge gaps will be identified, and the research required to advance the predictive capability will be further discussed.

Co-Authors: Mahsa Masjoudi

Vacuum-UV (VUV) irradiation at 185 nm generates hydroxyl radicals (•OH) through direct photolysis of water. It is therefore a promising advanced oxidation process (AOP) for water treatment and potable reuse. However, presence of different constituents in the water matrix can significantly influence the efficiency of the VUV AOPs for the treatment of micropollutants by either light attenuation, radical scavenging, or formation of secondary radical species. In potable reuse trains, the composition of the AOP feed water could vary depending on the type of treatment process used upstream of the AOP systems. For instance, in potable reuse treatment trains involving reverse osmosis (RO), the AOP feed water has a relatively clean matrix, but may contain small amounts of bicarbonate alkalinity due to the dissolution of carbon dioxide into the RO permeate. Additionally, the water matrix may contain various concentrations of other ions or organic matter. This study evaluates the impact of bicarbonate and chloride ions, as well as organic carbon, on the removal of 1,4-dioxane by VUV and VUV/Cl2 AOPs. The findings showed that both bicarbonate alkalinity and organic carbon slow down the degradation rates of 1,4-dioxane, while chloride levels below 6 mg/L improve its degradation, particularly when free chlorine and/or chloramines are used as the oxidants. Experiments conducted on an actual RO permeate sample also demonstrated the compatibility of the VUV and VUV/Cl2 AOPs with potable reuse trains. These findings are useful for the design and development of VUV-based AOPs for efficient treatment of micropollutants in potable reuse systems.

Co-Authors: Melisa Avdic, Katrina Fitzpatrick, Mariana Lanzarini-Lopes

* Corresponding author email: marianalopes@umass.edu Abstract There is growing interest in using germicidal ultraviolet (UV) radiation light-emitting diodes (LEDs) for surface disinfection to prevent 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. However, major limitations in using UV-C LEDs for surface disinfection include (1) geometrical restriction of the UV light distribution and (2) minimum irradiance (μW/cm2) required for complete inactivation of the surface. Our group is currently tackling these two limitations. This presentation will discuss results from two separate studies, where we have (1) explored the use of UV-C side emitting optical fibers to inactivate surface-bound bacteria inside tight channels and (2) established the minimum irradiance (μW/cm2) needed to obtain inactivation of surface-bound organisms in a nutrient-rich environment. The UV-C side emitting optical fibers with an irradiance of ~0.15 μW/cm2 to ~18.79 μW/cm2 achieved up to 6 log inactivation of surface-bound Pseudomonas aeruginosa and Methicillin-resistant staphylococcus at 265nm wavelength inside a 1m long PTFE channel (4.2mm internal diameter). The minimum UV irradiance required for complete inactivation of surface-bound Escherichia coli during prolonged exposure was averaged at 0.38 ± 0.11 μW/cm2 and 0.18 ± 0.02 μW/cm2 for 265 nm and 280 nm wavelength, respectively. Both studies help to advance the design and implementation of continuous UV disinfection systems. A minimum irradiance value is essential in ensuring adequate inactivation during prolonged disinfection. Additionally, the UV-C side emitting optical fibers provide an innovative way to remove the geometrical restrictions in UV disinfection systems and irradiate surfaces inaccessible with traditional UV lamps and LEDs.

Co-Authors: IUVA SDG Task Force

This workshop, proposed by the IUVA SDG Task Force, is a session to be run in parallel to the other conference sessions. The proposed 4-hour workshop (exact timing negotiable) brings together a diverse audience of academics, policymakers, and practitioners to understand current needs and chart a path forward for improving the adoption of small-scale UV water disinfection systems in developing settings. The workshop will be divided into 3 parts that are described below. In collaboration with external participants from the WHO, World Bank, and UAE water agencies, this workshop will be used to develop a mapping report of the IUVA membership’s pathways to delivering UV solutions to support the advancement of the UN SDGs.

Part 1: Taking Stock of Initiatives (30 min)

The IUVA SDG Task Force will report the conclusions and recommendations identified from 2 years of work with external partners towards understanding the opportunities and barriers for UV for water treatment in developing settings. The audience will gain an understanding of recent efforts towards improving global water access, current trends of UV in emerging markets, and potential opportunities.

Part 2: Engaging New Perspectives (1 hour)

An interactive panel discussion will be held with implementors, policymakers, and industry stakeholders from the Middle East and North Africa to understand contextual barriers and perspectives towards UV for water disinfection. The audience and the IUVA will come away with new insights and partnerships around sustainable, safe, and practical applications of UV in these contexts.

Part 3: Forging a Path Forward (2 hours)

The audience will participate in a systems-thinking activity (e.g., World Café format) to map key design considerations and institutional and policy frameworks. The outcome of this section will be a report of actionable “next-steps” towards creating enabling environments and fit-for-purpose designs for sustainable UV water treatment in developing settings.

Co-Authors: J. Losco

Environmentally Safe Germicidal Phosphor Lamp D.E.Murnick, Rutgers University and J. Losco, VUV Technologies An effective germicidal band phosphor lamp using 172 nm radiation from efficiently produced xenon excimer molecules was first reported in 2013. (N.M. Masoud and D.E. Murnick, Review of Scientific Instruments 84, 123108 (2013)). The gold standard however is the low pressure mercury lamp radiating at 254 nm with typical power efficiency of 30 to 35%. Issues with mercury lamps include their use of a toxic substance; their need for long warm up times; and their sensitivity to ambient temperature. Recently a 223 nm dielectric barrier KrCl lamp has been proposed as an alternative non- mercury based germicidal lamp with the potential of reduced damage to any exposed human tissue. Such lamps, however, have low intrinsic efficiency, can produce ozone at the dielectric barrier in air, and require the use of a toxic halogen gas.

We have recently produced germicidal lamps using a highly efficient 172 nm lamp internally coated with a VUV to UVC phosphor having 30 to 40% energy conversion efficiency and high power density. The lamps are rapidly switchable, have long projected lifetimes, and are compatible with dimmers. Using 25W tubular 172 nm lamps, coated with a high quantum efficiency phosphor to convert the VUV radiation to longer wavelengths in the UVC region, we have created fluorescent lamps with similar efficiency and output power density to that of existing mercury lamps. The phosphor employed yields UVC radiation covering the entire germicidal band but peaking at the shorter 225 nm region. Limited data are available suggesting that various organisms may respond differently to wavelengths throughout the germicidal band, (Ren Zhuo Chen, Stephen A. Craik and James R. Bolton, Water Research 43 (2009) 5087–5096)) hence broad band radiation may be most suitable for many applications.

Co-Authors: Kriangkrai Pattanapakdee, Manoch Sanluang, and Sumate Naetiladdanon

UV-C mercury vapor lamps are commonly used as a light source in a disinfection chamber. Despite their omnidirectional radiation, the lamps are limited to mounting on one or two sides of the disinfection chamber because of their large size, causing low irradiance uniformity on the object surfaces. Moreover, there is significant difference in the irradiation value of each area of the surfaces. Inefficient light source placement causes decreasing in disinfection efficiency and low irradiance uniformity. Thus, a longer sterilization period, along with more energy consumption, is required. Additionally, deterioration of the object, which results from high-dose or long-term exposure to UV-C, may be found. To eliminate this limitation, the UV-C LEDs with smaller sizes have been used for surround installation.

In this study, a 0.03-m3 (30-liter) UV-C disinfection chamber was developed for high irradiance uniformity over the object surfaces. The UV-C LED was used as the UV-C radiation source. Also, aluminum reflector materials with 55-87 percent UV-C reflection properties, have been installed as a chamber’s reflector. The placement and the number of UV-C-LEDs being used were simulated in Photopia software in a variety of schemes. Irradiance and uniformity on the surfaces of the rectangular prisms in different sizes were evaluated to ensure that the minimum irradiance on each surface of the object is not less than 1 W/m2. Besides, the amount of UV dose used for each microorganism's disinfection is specified for proper exposure time consideration. The irradiance of UV-C LEDs was simulated in Photopia software as well as measured by a UV-C meter in the laboratory to ensure compatibility between the simulation model and the actual prototype model. Subsequently, a variety of UV-C-LED placement schemes were simulated.

The study found that the surround UV-C-LED placement gave higher irradiance uniformity compared to the side-mounted UV-C-LED placement. According to the 16-LEDs simulation, there were 5 schemes, and the result of the simulation showed that all schemes had a minimum irradiance of more than 1 W/m2, which was considered acceptable. However, there is one scheme giving out the highest value of minimum irradiance and irradiance uniformity: 1.26 W/m2 and 0.5, respectively. Then, the limitation on object size for this scheme was observed. The result shows that the volume of the object exceeds 50 percent of the volume of the chamber—the object blocks LEDs’ radiation and affects uniformity.

Co-Authors: Patrick N. Mirindi, Adefolawe A. Adeyeye, Richard M. Mariita, Sara E. Beck

Access to clean water is a significant challenge in sub-Saharan Africa. Marginalized rural communities (MRC) are the most affected as they use contaminated water sources which include streams, rivers, boreholes, wells, humanmade springs and harvested rainwater (HRW). Therefore, such communities perceive rainwater harvesting as an effective mitigation strategy. Although microorganisms and viruses grow in water repositories, most households in such communities use the HRW without disinfecting it, which poses health risks. Boiling is a standard water treatment method; however, it lacks a disinfection residual and results in indoor pollution, causing severe health problems and environmental degradation. Although not 100 % effective, biosand filtration is recommended for point-of-use water treatment, especially in MRC. Also, ultraviolet light-emitting diodes (UV LEDs) have shown potential for water disinfection; however, their efficacy drops when applied to waters with high turbidity, color, and other suspended and dissolved particles. In this study, the effectiveness of biosand/charcoal incorporated with a gravity-driven flow-through UV-C LED treatment system for HRW at Nyamesocho, a MRC in Kisii County, Kenya, was investigated. HRW samples collected before the biosand/charcoal and UV-C LED treatment showed presence of E. coli and total coliforms, whose concentration varied depending on the point and season of collection. Meanwhile, the treatment system effectively removed the E. coli and total coliforms from the HRW. While the biosand/charcoal system helped solving the problem of UV absorbance, smell/odor, and maintaining an optimum pH, the UV-C LED system could play a big role in inactivating microorganisms and viruses in the HRW that may escape from the biosand/charcoal system. In comparison, other water sources such as borehole, stream, and humanmade springs showed high microbial contamination, making them unsafe for domestic use when untreated; while piped water and treated HRW showed low risk/safe results. Finally, the gravity-driven system reduced costs and power requirements.

Co-Authors: Not applicable

UV-LED can be a good-fit option for small and decentralized water treatment facilities in remote locations due to its tiny size, physical robustness, relatively long life time (10,000 hours+, depending on the product) and mercury-free components. UV-LED modules designed for such applications are commercially available, but their performance are pre-validated mostly in a lab-scale with pure-cultured challenge microorganisms, not in the field. To promote the data-driven implementation of UV-LED systems while understanding the challenges in practice, it is inevitable to conduct field testing in a long-term to evaluate the performance against indigenous microorganisms.

Demonstration studies of a UV-LED flow-through module were conducted at three water treatment facilities located in remote areas in Japan. A UV-LED flow-through module was tested for 1-2 years at each location, and its performance was monitored in the inactivation of indigenous bacteria including Escherichia coli (E. coli), total coliforms, standard plate count bacteria and heterotrophic plate count bacteria. The source water quality in the physical-chemical parameters, such as turbidity and UV transmittance, were also monitored to understand the natural fluctuation of such parameters and their impacts on the inactivation efficiency.

Overall, the results demonstrated that the UV-LED module is effective and stable enough for practical applications. For example, at a test site sourcing a river running through a mountain valley, the source water was 100% positive with E. coli while the treated water was negative or contained a trace level of E. coli. All monitoring data were shared with the local government and community residents, which eventually resulted in the implementation of the module in some locations. Such “demonstration-to-implementation” scheme would be a good approach to promote UV-LED technologies and applications.

Co-Authors: Richard Simons, Matt Kavanaugh, Zeyanna Al-Saifi

This presentation will provide an update to data presented at the 2023 iCulta conference in Berlin. UVC LED reliability has been touted as a technology differentiator to traditional ultraviolet sources with lifetimes extending more than ten thousand hours [1]. However, this often includes assumptions about the processes using LEDs, factoring in the ability of UVC LEDs to turn on and off instantly in extending the functional product lifetime. While this is indeed a benefit of UV LEDs, recent applications such as air disinfection and municipal water disinfection often operate with near perpetual use. In addition, these applications require output powers of the best in class UVC LEDs and are often operated above the manufacturer rated drive current.

The purpose of this presentation is to examine operational data of high power UVC LEDs with wavelengths between 265nm and 280nm operated at different current densities and solder point temperatures. Impacts on the lifetime, forward voltage, and wavelength versus operating time will be presented. A comparison of these results with other reported performance data will be considered.

Details of the experimental setup will be provided, one aspect of the test is that photodiodes were used in lieu of a spectrometer to continuously monitor LED output power, although a spectrometer was used to verify initial and final output powers. In the experimental design, single LED chip drive currents range from 350mA to 700mA with solder point temperatures from 40C to 80C. One outcome from the previous testing was current density has a larger impact than temperature on LED lifetime. New data will be presented that further explores this. Multiple manufacturers were evaluated with models chosen only from single SMD packaged options.

References

[1]Trivellin, N.; Fiorimonte, D.; Piva, F.; Buffolo, M.; De Santi, C.; Meneghesso, G.; Zanoni, E.; Meneghini, M. Reliability of Commercial UVC LEDs: 2022 State-of-the-Art. Electronics 2022, 11, 728.

[2]U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Lighting R&D Program, (2002), Operating Lifetime Study of Ultraviolet (UV) Light-Emitting Diode (LED) Products, https://www.energy.gov/sites/default/files/2022-09/ssl-rti_uv-leds-lifetime_apr2022.pdf

Co-Authors: De Palma I., Amodeo D., Puccio A., Cevenini G., Messina G.

Background:

The COVID-19 pandemic has emphasized the importance of airborne pathogen transmission. Air disinfection is crucial for reducing transmission risks in various settings. UV-C rays have proven effective in deactivating bacteria and viruses. While UV-C systems are gaining popularity for air purification, their performance in occupied indoor environments is understudied. This investigation aimed to evaluate the effectiveness of a UV-C air purifier system in reducing microbial air contamination in an office setting.

Methods:

The study was carried out from December 2020 to February 2021 at the University of Siena, Italy. The UV-C air purifier system had an air disinfection capacity of 210 m3/h and was equipped with 12 UV-C lamps (254 nm). The experiments were set in an office of 65 m3. The experiments were carried out in 4 stages: in the first stage, contamination was assessed in the absence of people; in the second, 3-5 were occupants present and the device switched off; in the third stage, the device was switched on in presence of subjects; in the fourth stage, the device was switched off while subjects were still present. Real-time air samples on Petri dishes were periodically collected within the 4 phases and then incubated at temperatures of 36°C and 22°C. Statistical analysis using Stata 16 software was performed with a significance level of 95%. Interpolating models were used to describe the contamination fluctuation dynamics during the several phases. Results:

In the preliminary tests, a significant reduction of 62.5% in Colony-Forming Units (CFUs) was observed after incubation at 36 °C. In the main test, a comparison of CFU data during the device-on phase (90 minutes) and the subsequent device-off phase (60 minutes) revealed a statistically significant increase (p = 0.001) in environmental contamination. The mean CFU/m3 rose from 86.6 (65.8–107.4) to 171.1 (143.9–198.3), representing an approximately 100% increase. The interpolating models displayed a good fit for the trends of CFU reduction and increase, respectively, when the device was on and off. Conclusions:

The UV-C lamp-based system effectively reduced environmental and human contamination. When the device was switched off after a minimum of 30 minutes of operation, air quality rapidly deteriorated within 10 minutes, resulting in airborne microbial contamination levels exceeding 100% of the previous value observed when the device was active.

Co-Authors: Peter Sperfeld, Jutta Eggers, Tim Schwarzenberger, Karl-Heinz Schön, Sven Einfeldt, Jens Rass, Christian Bokermann and Alexander Wilm PTB, Braunschweig, Germany, DVGW-Technologiezentrum Wasser, Karls

The use of ultraviolet light for disinfection has a long history dating back to the 19th century. In recent decades, UV disinfection has generally gained in importance. With new-developed short wavelength UV-LEDs on the one hand and filtered KrCl excimer lamps on the other, two new distinct trends are developing in the field of low wavelengths disinfection.

The presentation will address the measurement and calibration uncertainties in the field of disinfection for UV-LEDs and FAR-UVC applications. These are also compared with the uncertainties of UVA LEDs, which are well known from applications like UV curing.

For this purpose, the calibration uncertainty must be separated from systematic influences in the application, such as the sensors spectral weighting function and the microbicidal efficacy of the light source. Therefore, the results of a national comparison of different accredited laboratories for measuring the irradiance of UV LEDs are presented. Some steps to reduce calibration uncertainties for laboratories will be shown.

In addition, data from the funded joint project DINoLED will be shown and discussed. In this project, test criteria for LED-based UV disinfection systems in municipal waterworks are being developed which will result in a DRAFT for a future DIN standard. The focus of this presentation is on the so-called spectral mismatch of UV sensors and measures to reduce it. In summary, the expected uncertainties for irradiance measurements in UV disinfection are shown and discussed.

Co-Authors: None

Far UV-C technology has emerged as a promising airborne disinfection, particularly suitable for public and multi-user locations. While laboratory results have shown promise, there is limited information available on its practical application in real-world public spaces during and post-COVID-19 pandemic. This study aims to enhance awareness and understanding of far UV-C technology, which is currently in its early adoption stage, focusing on its potential applications in user environments where airborne pathogenic transmission poses a higher risk to public health. To achieve this objective, we have assembled a diverse and collaborative team of scientists and engineers. Our collective effort is directed towards validating the effectiveness of far UV-C technology in actual installation environments, both in current and potential applications. Ongoing assessment of safety considerations is also an integral part of our research. It is important to note that the efficacy of far UV-C technology in real-world installations is strongly influenced by operational conditions, environmental factors, and user comprehension of the technology. Numerous field tests utilizing 222nm KrCl microplasma lamps have been conducted across various operational settings, spanning from a few months up to two years. The focus of these long-term field tests has been on sustained reduction of viral concentrations within spaces equipped with standard indoor ventilation systems. The insights gained from these installations serve as a foundation for proposing new, futuristic applications of far UV-C technology, which will be discussed in this study. Additionally, we will explore the new applications while emphasizing the need to strike a balance between disinfection efficacy and safety considerations. These findings suggest that far UV-C technology holds significant potential for effective implementation in various new indoor applications aimed at public health preservation, particularly in the post-pandemic period.

Co-Authors: Po-Shun Chan

There is much optimism around the promise of UV LED reactors. However, in striking contrast to the situation for visible lighting applications, UV LEDs have significantly lower electrical conversion efficiency than legacy UV sources, and are more expensive, even with recent improvements. Despite these disadvantages, there are narratives that because LED light sources can be applied in different form factors than conventional lamps, innovative reactor designs will improve disinfection performance and compensate for lower electrical efficiency. With the recent availability of residential scale UV LED reactors, it is now possible to evaluate these narratives by testing these reactors with bioassays. Bioassays in residential certification testing evaluate performance at one condition. In contrast the USEPA UVDGM and USEPA UV Compendium provide an excellent framework for testing the performance of UV reactors, and for understanding performance fundamentals via the RED Bias, a term that accounts for differences in microbial resistance between test microbes and target pathogens. Although the UVDGM and UV Compendium were developed for UV treatment of municipal drinking water from filtered surface water sources, their testing approaches are universal and can be applied to any UV reactor in any disinfection application. We conducted these state of the art multi-organism bioassay tests and data analyses on a suite of commercially available UV LED reactors and conventional LP UV reactors. We tested them over a range of flows, UV transmittances, powers, and microbe resistances, allowing us to make normalized performance comparisons regardless of the sizes of the reactors. As a different measure of reactor performance, we determined the RED Bias values for these reactors in relation to various common target pathogen inactivation cases. The magnitude of the RED Bias for given pairs of challenge microbe and target pathogen resistances, is indicative of the dose distribution of the reactor and thus how close to ideal the reactor is. These concepts will be explained and UV LED and conventional UV reactor performance comparisons will be presented.

Co-Authors: All members of the IUVA Education Committee

The Education Committee has developed a new concept for Education for UV practitioners and those considering being involved in the industry. This session will explain the concept and showcase the Center and get participant feedback on how we can promote its use. This session will also be the official launch of the ERC

Co-Authors: Eric Prast, Christopher Bowers, Chris Jones, Ernest R. Blatchley III, Karl G. Linden, Joel Ducoste and Richard A. Rasansky

The COVID-19 pandemic has demonstrated that respiration protection is paramount for airborne biological threats introduced by nature, accident, or weaponized means. Thus, more effective, re-usable, and scalable PPE is needed both for military biodefense against specific threats as well as protection for civilian public health.

Informed by data previously shared in this three-part presentation, a novel form of PPE is under development that integrates germicidal UVC (200-280 nm) into a safe, battery powered, wearable device to disinfect air during both inhalation and exhalation leveraging XCMR’s Symmetrical Flow Disinfection (SFD) process. Utilizing an enclosed reactor allows a greater selection of UVC sources, eliminating the risk of human exposure, while allowing effective pathogen inactivation under dynamic environmental conditions.

A number of reactor configurations were produced, each with different types of UVC radiation sources (e.g., LED and Low Pressure Mercury Lamps) at various irradiance levels. A microporous diffuse highly reflective material lining was used in the reactors to produce a near perfect Lambertian reflectance. This resulted in internal irradiance that was significantly amplified, yielding effective inactivation of biological agents.

Laboratory testing of the prototype, bench-top reactors included optical characterization and biological analysis using T1 phage which yielded results that aligned favorably with computer simulated models. Utilizing advanced modeling and simulation techniques for performance optimization, a conceptualized device design was realized through rapid digital prototyping.

Further engineering development resulted in the development of a highly efficient battery operated light engine, microprocessor-based controller with mesh-network connectivity, battery charger, and modular sensor feedback bus integrated into the desired form factor. Essential key characteristics based on core principles of human factor design included improved ergonomics and comfort resulting from wearability studies and anthropometric analysis to enable a greater likelihood of user adoption.

Together these data demonstrate feasibility of UVC disinfection systems incorporated into a wearable, reusable, device to inactivate airborne pathogens and achieve equivalent or greater protection to an N95 mask. Relying on enhanced treatment through continuous inactivation of pathogens as opposed to mechanical filtration alone offers (i) superior protection to both users and bystanders alike, (ii) reduced breathing resistance and comfort, (iii) reduced ecological footprint by mitigating biohazard waste of disposable masks, and (iv) adaptability to future biological threats. Prototypes have been successfully created which demonstrate this functionality. Several iterations of these devices are being evaluated against computer modeled simulations and undergoing field testing as part of federally funded research by the US government.

Co-Authors: Jason A. Randall, Karl G. Linden, Christopher Bowers, Joel Ducoste, Chris Jones, Deborah Mosca, Eric Prast, Richard A. Rasansky, and Ernest R. Blatchley III

A project was initiated to develop an affordable, mobile, biodefense solution that is on-demand, reusable, and will increase mobility, ease of communication, and mission effectiveness for military personnel; this device will also have civilian applications. Development of this device has involved an integrated team effort based on laboratory experiments, numerical simulations, and prototype design. This three-part presentation will address these components of design and development, as well as the links among these components. Many of the principles of the performance of this system and its design will translate to other UVC-based applications.

The device is built around conventional low-pressure mercury (LP-Hg) lamps and UVC LEDs. The device also involves the use of materials that are highly reflective in the UVC range, with reported diffuse reflectance of greater than 90% at the wavelengths of emission of the LP-Hg lamps and UVC LEDs used in this research (254 nm and nominally 280 nm, respectively). A micropositioning device and a microfluorescent silica detector (MFSD) were used to conduct detailed measurements of the fluence rate field within the irradiated zone of the device. These measurements compared well with numerical simulations based on ray tracing (see Part 2). Measurements and simulations indicated that the inclusion of the reflective surfaces on the interior walls of the irradiated zone resulted in considerable amplification of local and average fluence rate. Moreover, the fluence rate field indicated a strong positive correlation between regions of high fluence rate and high velocity. This correlation promotes uniformity of the dose distribution delivered by the device, which in turn leads to high disinfection efficacy. This behavior is fundamentally different than most UV-based devices, for which the fluence rate field and velocity fields tend to be strongly anti-correlated, resulting in broad dose distributions.

Photon ‘recycling’ that resulted from efficient reflection also led to effective inactivation of aerosolized viral challenge agents. Specifically, an aerosolized suspension of T1 phage was introduced to the system using a single-port Collison nebulizer; T1 was used as a challenge agent in these experiments because it is slightly more UV-resistant than common viral pathogens (e.g., coronaviruses and influenza viruses). Air samples were collected from the exhaust of the device using a bioaerosol sampler; liquid samples from the samplers were then subjected to a plaque assay to quantify infective phage concentration with and without treatment. The results of these measurements demonstrated effective inactivation of the viruses in early and final prototype devices.

Co-Authors: Patrick Aigeldinger

Keywords: Light-emitting diodes; disinfection, UVC, Aluminum Nitride (AlN), Water Treatment, Water Disinfection Access to clean drinking water continues to be a focus as climate change and population growth continue to exacerbate access for over 2 billion people. The adoption of UV disinfection as a practical means to deliver microbial-safe water has grown, with many water suppliers developing new products or modifying existing ones to incorporate UV disinfection. For areas or OEMs without a well-established maintenance infrastructure, traditional UV sources can present a challenge around annual service and disposal. UVC LEDs have reached a point where they meet performance goals for maintenance-free point-of-use disinfection.

UVC LEDs coupled with effective product design can eliminate the regular and unplanned maintenance required with current UV products. Removing this burdensome maintenance enables the deployment of UVC water treatment in regions with limited maintenance infrastructure or a highly distributed consumer base. This will allow water manufacturers to develop UVC products for markets like India and South America that struggle with large populations without established service networks.

UVC LEDs based on Aluminum Nitride (AlN) can deliver power and lifetime in the germicidal wavelength range of 260 - 270 nm at a level that is feasible for many point-of-use and lower flow point-of-entry systems. However, incorporating UVC LEDs in water disinfection systems requires substantial rethinking in the arrangement of UVC radiation sources to achieve an efficient system. This talk will discuss considerations when designing with these light sources and outline how manufacturers can use the design flexibility of UVC LEDs to deliver a reliable, maintenance-free design.

Co-Authors: Rolf Ziegler Ph.D., Karin Ziegler, Uwe Ziegler

In most systems using UV-C, monitoring of UV-C irradiance is essential to ensure disinfection performance or to ensure the effect on photochemical processes. The well-known Austrian national standard ÖNORM M 5873-1:2001 defines requirements for reference and duty sensors used in drinking water disinfection systems using low pressure UV-C lamps. However, due to high sensitivity and measurement accuracy, ÖNORM sensors are widely used for other applications as well.

In 2020 this standard was replaced by a new edition: ÖNORM M5873-1:2020 and ÖNORM M5873-3:2020, further refining requirements and adding detailed description on calibration. This includes source- and detector-based calibration and modern radiometer designs with enhanced functionality are considered.

All components of a UV-C radiometer must be compliant – the UV-C sensitive detector and all signal processing, including amplifiers or analog-digital converters. All these components shall be checked on a regular basis with a certified reference radiometer. However, the new edition now explicitly addresses designs with digital, internal signal processing, thus just the UV-C sensor itself needs to be calibrated. The new edition also describes the use of a correction factor to adjust a sensor to the reference sensor value.

ZED produces a family of UV-C sensors including ÖNORM plant sensors and ÖNORM reference sensors which are certified according to the new editions, taking advantage of the new possibilities in ÖNORM M 5873. The all-digital design and the integration with advanced tools even allows for on-site calibration.

Co-Authors: CA Mahesh Rathi

Upper air ultraviolet germicidal irradiation (UVGI) systems, particularly utilizing UVC, have recently gained acceptance among major institutional decision-makers. Despite its century-long research history, limited advancements have been made in designing efficient fixtures for use in occupied spaces. This study aims to develop innovative, high-efficacy UVC fixtures by employing multi-physics simulations and advanced reflector design tools to maximize UVC in the upper region while keeping lower room UVC within threshold limit values (TLV).

To address the limitations of current technology, we consulted stakeholders, including doctors, administrative staff, engineers, and government representatives. A creative exploration process was conducted to rethink UVC delivery in the upper air of a room, resulting in a curation of technically feasible ideas based on predefined constraints. This was followed by CAD modeling, simulation using real material optical datasets, and iterative design refinements to optimize UVC irradiance distribution. Prototypes were then built and tested using a grid-based measurement strategy with high-resolution, calibrated UVC meters.

Low-pressure mercury lamps were chosen as the primary light source due to their favorable cost-to-UVC density ratio, particularly for developing economies like India. The application of design thinking in the redesign of upper room UVGI fixtures led to a significant increase in efficiency, ranging from 7% to 32%, compared to traditional 1-3% efficiencies, while maintaining minimal human exposure and safety. This study demonstrates the potential of leveraging advanced design tools and simulation techniques to develop innovative UVC fixtures for improved air disinfection in occupied spaces.

Co-Authors: None

Since the usage of UV light is an invisible process and the importance of the accurate dose repeatedly emitted is of utmost importance, and needs to be calculated and measured, how can you make sure you have reached your targets no matter if its about disinfection, infection prevention, curing or any kind of area where UV is essential?

With the new measurement system from Intellego Technologies you can. The system includes measurement tools - dosimeters - and a cell phone app. The system closes the loop between randomly applying UV light and verbal promises about what the actual UV equipment in use is capable of doing to getting visible and accurate evidence of which dose has been applied and where, has the UV light reached all areas that it was supposed to (e g all parts of a room) so that the result can be measured stable over time.

The new thing with our dosimeters are that they are now coming with an app for your cell phone. This software can also be installed e g in a line PC on a production line or in a autonomous robot. With the app you have a quality control system that will allow you read the color differences on the dosimeters (different colors correlates to different energy levels in mJ) accurately and tell you the value. The app will also allow you to save every image of the dosimeters together with time stamp, name of the operator, location etc. The images can then be stored in the phone, in the cloud or at an external hard disc.

By doing so you have a quality control system where you can monitor, control and follow the results over time, and you have closed the loop from applying-seeing-believing-monitoring to storing.

Co-Authors: none

Microorganisms present a significant challenge within the food and beverage industry, leading to substantial food loss. While these microorganisms play a crucial role in food production, facilitating the creation of diverse products such as bread, beer, wine, vinegar, and yogurt through the involvement of yeasts, molds, and bacteria, their growth and activities also contribute to food spoilage and contamination. These adverse effects have wide-ranging implications for the food and beverage industry, encompassing economic losses, damage to reputation, and potential legal consequences.

In the realm of the food and beverage industry, gas discharge lamps have found extensive use in disinfection applications for food packaging. However, traditional light sources face limitations in certain scenarios, notably when disinfecting bottles with narrow openings. This situation often forces bottlers to resort to wet disinfection techniques, resulting in significant volumes of wastewater and an increased environmental burden. While UVC disinfection cannot entirely replace certain wet disinfection methods, it can effectively reduce wastewater generation. UVC LEDs, with their smaller size, enhanced durability, and greater design flexibility, represent a promising light source for addressing this particular application.

This presentation aims to provide an overview of the design and development of a UVC LED bottle disinfection prototype. The primary focus will be on exploring the various design aspects of an LED-based fixture, along with comprehensive device testing and microbial evaluation results.

Co-Authors: federico mastrocola

The disinfection of transport means has become imperative since the onset of the Covid-19 pandemic, and is set to remain so going forward. Numerous guidelines highlight the importance of systems to contain the spread of diseases in the public transport sector to guarantee the health and safety of those traveling and those who work in this high-risk industry.

Numerous scientific studies and guidelines on using UV-C to sanitize buses, trains, airplanes, metros, etc., have been conducted for many years.

We have developed specific products for this industry, obtaining the necessary certification for the rail sector and positive tests in natural environments thanks to our numerous pilot projects.

We want to present an overview of the necessary tests to obtain “Fire Protection UNI EN 45545,” the antivibration shock and bump test, “EN 50155:2017,” and “EN 61373:2010” and what are the limits to be able to install UV-C technology inside an environment as challenging as railways.

Co-Authors: Fabrizio Morelli

Upper-room UV systems can be safely and effectively deployed to disinfect large volumes of air in occupied spaces, reducing the transmission of airborne microbes.

ASHRAE GPC 37 committee is developing guidelines to provide minimum requirements for the safe and effective implementation of upper-room UV-C systems for air disinfection.

The guidelines describe best practices for assessing needs in the context of other airborne infection control measures and understanding what is necessary for commissioning, design, installation and maintenance, and operation.

The Commissioning process verifies and documents that a project is “planned, designed, installed, tested, operated and maintained to meet Requirements.” The decision to install interventions such as UV “Upper Air” is based on a desire to reduce the risk of transmission of airborne infectious microbes by lowering their concentration in space. Risk is determined by the microorganism of concern and the population in the area.

In our presentation, we will analyze an actual case where we will use the ASHRAE GPC 37 FLOW CHART to present the activity to identify spaces that would be eligible for a practical application of upper air UV.

We will showcase how to use the flow chart to identify the best location for a meaningful application of UV devices; once the spaces are identified, we will talk about how to use CAD software together with field measurements to verify sizing and installation.

Both the locations described in the presentation have been candidates for the PNNL study on behalf of the Department of Energy (DOE), “Nationwide field evaluation study on Germicidal Ultraviolet (GUV) air disinfection system installations.”

Co-Authors: Steve McDermid, Allan Archer, Mari Burgess

Primary wastewater is particularly challenging to disinfect due to high concentration of suspended solids, dissolved organic matter, nutrients, and inorganics species. For numerous reasons, chemical disinfectants such as chlorine and ozone are not well suited for the disinfection of primary treated wastewater. On the other hand, the application of UV light for the disinfection of primary treated wastewater has been practiced for a few decades with the proven ability to produce safely treated effluent. Yet, the arrival of next generation UV reactors and advanced methodologies for determining required UV doses has enabled Trojan Technologies to be apply UV to even lower quality effluents while not only reducing capital and operating costs but also meeting ever more stringent microbial limits

In this presentation, Trojan will highlight recent TrojanUVSigna® systems that have been installed at facilities following primary treatment and present data and analyses from detailed site performance testing done to demonstrate the efficacy of UV for disinfection of primary effluent wastewater.

One such facility has relied on UV disinfection to treat the primary effluent for many years and recently installed the more energy efficient TrojanUVSigna system with the goal of saving costs through reduced electrical power consumption and equipment maintenance. The newly installed system TrojanUVSigna 6-row reactor is comprised of three UV banks, each with 81 lamps. The 1 kW Solo Lamp® uses 253.7nm monochromatic UV light with low pressure high output technology, in contrast to the older TrojanUV4000® UV system that uses 3 kW medium pressure polychromatic UV lamps. The Solo Lamps are contained within quartz lamp sleeves, which are kept clean from fouling using a chemical/mechanical wiping system. Trojan Technologies completed on-site performance testing of the new UV system under the observation of third-party industry experts.

A second facility recently adopted UV light as disinfection technology to treat enhanced primary wastewater effluent. The TrojanUVSigna system is configured in 5 channels, with 3 duty channels. Each channel has three UV banks that house lamps that emit light at 253.7nm. Trojan Technologies completed on-site performance testing of the UV system in 2021. The goal of the performance tests was to determine disinfection performance over a range of operating conditions.

Co-Authors: Gonzalo Narvaez

Sustainable low cost water disinfection using UV-Light and Sonochemical degradation systems: Making drinking water accessible for dessert indigenous communities at Colombia.

A synergistic effect between membrane ultrafilter UV light 254.5 nm and Ultrasound increased the degradation of organic matter from 30 to 98% in 2 minutes. Removes of 99.999% of parasites, bacterias, viruses, microplastics and good phisicochemical properties was reached in the drinking water. The device prototipe can reach NSF/ANSI P231, standars and produce up to 18000 Litters before to change the system i sun and eolic powered.

The low quality and availability of water in the indigenous communities of the Guajira desert in Colombia affects 95% of the population called wayuu. In many cases they have to drink and share with the animals the water from the jagüeyes (a kind of open-air reservoirs where they collect rainwater). The presence of parasites, protozoa, bacteria, microplastic viruses, among other chemical contaminants due to the presence of saline environments in the desert, will destroy the health of the most vulnerable population, such as the elderly and children.

The interventions carried out, many of a temporary nature, have been inadequate and are not adequately articulated with the particularities of the Wayuu community, solutions based on the use of chemical substances, have the problem of accessibility and chemical risks in the communities. Sustainable alternatives must be designed, from the economic and environmental point of view, and framed in the social context of the Wayuu community, which guarantee access to drinking water without the need for chemical products or non-alternative energy sources. In the present investigation, the scientific results of the validation of a low-cost device that filters, purifies and sterilizes water with high-efficiency membranes and inactivation of the microbiological load by the synergistic effect of ultraviolet light and advanced oxidation processes are shown. by ultrasound that uses sunlight and wind energy as energy sources. A synergistic effect between the 254.5 nm UV light membrane ultrafilter and ultrasound increased organic matter degradation from 30 to 98% in 2 minutes. A 99.999% elimination of parasites, bacteria, viruses, microplastics and good physicochemical properties in drinking water was achieved. The device prototype can meet NSF/ANSI P231 standards and produce up to 18,000 liters before switching. The system is powered by sun and wind power.

Co-Authors: Jennifer Pagan, Oliver Lawal

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 particular area 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) 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 these data in combination with our wider 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: Georg Hirschmann, Alois Schmalwieser, Karl-Heinz Schön, Tim Schwarzenberger, Jutta Eggers

The quality standards for testing UV devices for drinking water disinfection with low pressure lamps as well as the requirements for reference UV radiometer are now harmonized by Austria and Germany in Europe. The increased acceptance of UV drinking water disinfection is attributed, amongst other reasons, to the better understanding of the process and the higher quality assurance of the UV disinfection devices. Establishment of quality standards on the requirements, including validation testing and certification of commercial UV devices, have provided the basis for the safe application of UV irradiation as primary disinfection for drinking water supply.

After careful consideration and negotiations over several years, a harmonization between the Austrian and German regulations has recently been achieved. This facilitates from now on the tasks of manufacturers of UV devices, waterworks operators, and authorities for the benefit of the drinking water consumers. Based on a standardized reference radiometer, objectively characterized UV lamps and a well-defined biodosimetric test procedure UV devices validated by the ÖNORM/DIN standard provide a guaranteed Reduction Equivalent Fluence (REF) of at least 400 J/m² during operation. This target REF was chosen, since data of manifold studies show that this fluence results in 4 to 6 log inactivation of the most relevant water-borne pathogens. On the other hand, the application of a REF below 400 J/m² is not permitted, as this is not sufficient to overcome the photoreactivation of bacteria. Repair of UV damages and regaining infectivity of bacterial pathogens would be the consequences.

References 

ÖNORM M 5873-1:2020 / DIN 19294-1:2020: Devices for the disinfection of water using ultraviolet radiation
Part 1: Devices equipped with UV low pressure lamps - Requirements and testing

ÖNORM M 5873-3:2020 / DIN 19294-3:2020:
Part 3: Reference radiometers for devices equipped with UV low pressure lamps - Requirements and testing

Co-Authors: S. Nevas 1, F. Schröppel 1, K. Schwind 1, Th. Gerloff 1, L. Ulm 1, J. Eggers 2, T. Schwarzenberger 2, K.-H. Schön 2, M. Paravia 3, S. Einfeldt 4, J. Rass 4, J. Ruschel 4, C. Bokermann 5, A. Wilm 5

UV-C LEDs are being considered for the disinfection of public drinking water, prompting the need for defining their characteristics and efficacy. The joint research project “DINoLED” investigates the necessary preconditions for a new German DIN standard that outlines test criteria for LED-based UV disinfection systems in municipal waterworks. The DIN 19294 series of standards in Germany, for instance, sets technical requirements for testing water disinfection equipment using ultraviolet radiation. One requirement is a reduction equivalent fluence of 400 J/m² at 254 nm for UV disinfection. To evaluate this, biodosimetry is conducted during reactor testing, where Bacillus subtilis spores are introduced into the system and their inactivation rate is measured. Within the DINoLED project a new detailed action spectrum for Bacillus subtilis was determined showing a fine structure around 270 nm and and a steeply descending curve above 280 nm. The main outcome of the project will be a first pre-draft of a test standard similar to existing protocols for mercury lamp-based systems.

The shift towards UV-C LED disinfection systems necessitates such new standards and test methods. The properties and microbicidal efficacy of UV-C LED sources have been investigated within the project. The centroid wavelength and spectral distribution of UV-C LED systems was found to play a crucial role in their microbicidal efficacy, with significant higher efficacy values achieved around 270 nm compared to low-pressure mercury lamps.

As UV-C LED disinfection systems comprise multiple individual LEDs, variations in their individual performance can alter the resulting spectral distribution of the total system. Therefore, criteria must be established for LED binning tolerances and allowable changes in validated systems.

After a short introduction of the DINoLED project, the new action spectrum for Bacillus subtilis will be presented and the microbicidal efficacy factor of LEDs as well as other characteristic parameters will be introduced and discussed. Co-authors affiliation: 1PTB, Braunschweig, Germany 2 DVGW-Technologiezentrum Wasser, Karlsruhe, Germany, 3Opsytec Dr. Gröbel GmbH, Ettlingen, Germany, 4 Ferdinand-Braun-Institut (FBH), Berlin, Germany, 5 Xylem Services GmbH, Herford, Germany, 6 ams-OSRAM International GmbH, Regensburg, Germany

Co-Authors: Zhe Sun, Mengkai Li, Zhimin Qiang

Conventional UV light sources, such as low-pressure and medium-pressure mercury lamps, are commonly used for drinking water disinfection, but face challenges due to mercury content and fixed output spectra. Emerging UV sources such as the KrCl excimer lamp and UV-C LEDs are mercury-free and offer varied output wavelengths, making them promising alternatives. Moreover, the combination of KrCl excimer lamp and UV-C LEDs could induce simultaneous damage to proteins and nucleic acids in pathogens, potentially enhancing disinfection effectiveness. Therefore, it is beneficial to investigate the synergistic effects of KrCl excimer lamp and UV-C LEDs in water disinfection.

In this study, a mini-fluidic photoreaction system equipped with both KrCl excimer lamp and 275 nm UV-C LEDs was applied to investigate the potential synergy on the inactivation of two challenge microorganisms, Escherichia coli (E. coli) as a representative bacteria and bacteriophage PR772 as a representative virus. We investigated the UV dose-response and reactivation behaviors of both microorganisms to monochromatic UV radiation at 222 and 275 nm, as well as coupled wavelengths. Additionally, the UVC-induced DNA damage and subsequent photo and dark DNA repair were evaluated by a real-time quantitative PCR.

The results show that combining 222 and 275 nm UV radiation at a fluence rate ratio of 1:1 and up to 14 mJ/cm2 for each wavelength, could improve the inactivation of E. coli by over 50% relative to the sum of inactivation yielded by each UV wavelength separately. However, no synergistic effect was observed for the inactivation of PR772 bacteriophage. Photoreactivation of E. coli was observed in the samples exposed to UV275 and UV222+275, while no dark repair was observed. The qPCR results show that UV275 is more effective in inducing DNA damage in E. coli and PR772 respectively, without any noticeable synergy in DNA damage. Agreed with the reactivation results, the repair of DNA damage were observed in the samples exposed to UV275 and UV222+275. These findings provide useful information for the development of efficient, mercury-free UV disinfection technology based on the combination of KrCl excimer lamp and UV-C LEDs.

Co-Authors: Xiuwei Ao, Weibo Wang

Antibiotics contamination is an emerging environmental concern, owing to its potential risks to ecosystems and human health. With the development of detection technology, antibiotics have been frequently detected in aquatic environment worldwide, and thus how to remove antibiotics from drinking water has gradually become an important challenge for the water supply industry. In this study, an emerging advanced oxidation process, i.e., the Medium-Pressure Ultraviolet/Peracetic Acid (MPUV/PAA) process was used to degrade norfloxacin (NOR), which is a typical fluoroquinolone antibiotic. Compared with the MPUV/H2O2 process, the PAA process alone and the MPUV process alone, the MPUV/PAA process significantly promoted degradation of NOR due to the considerable contribution of reactive radicals. In this study the effects of the PAA dosage, the initial concentration of the target compound, the pH of the solution, and the co-exiting carbonate (CO32-) and chloride (Cl-) contents on the MPUV/PAA process were investigated. The results obtained showed that the MPUV/PAA process could effectively degrade NOR (pH =5~9), and the degradation efficiency was significantly enhanced at pH 7 and 9 compared with that at pH 5. Increasing the PAA dosage positively influenced NOR degradation. This work provides a new approach for the removal of NOR in the municipal water treatment system in the future.

Co-Authors: Zhiru Lin, Wenjun Sun

Advanced Oxidation Technology (AOP) based on Ultraviolet (UV) as an enhanced water treatment process combination is being widely discussed in water treatment area in recent years. Worldwide, eutrophication in freshwater bodies is generally severe, and outbreaks of blue-green algae blooms occur frequently. Some studies have also shown that global warming may increase the frequency and duration of algal blooms. Hence, pollution control measures for algal toxins deserve more attention. Microcystins (MCs) are one of the most common algal toxins. The natural degradation rate of MCs is quite low and can remain stable in water for several weeks. At present, there are few research reports on the removal effect of microcystins by the combination of ultraviolet and peracetic acid, and the degradation pathway and mechanism are still unclear, making it difficult to provide sufficient scientific basis for practical engineering applications. This study has developed a new UV/peroxyacetic acid (UV/PAA) advanced oxidation technology to control microcystins in water. Using microcystin-LR (MC-LR) as a typical representative of cyanotoxins in water, this study investigated the degradation efficiency of UV/PAA with different UV wavelengths on MC-LR, the effects of water quality conditions and process parameters on degradation, the contribution of different active species to the degradation reaction through probe methods. This study aims to comprehensively investigate the characteristics and mechanisms of UV/PAA technology for degrading MC-LR, providing basic data and a scientific basis for future research and applications.

Co-Authors: Yuanna Zhang, Sarathy, Siva, Wenxuan Yin, Yongheng Huang, Bingqi Lyu, Yingru Song, Jumo He, Siyuan He, Aishan Feng

When producing quality stable water, the pollutants are generally controlled by multiple strategies. Especially for micropollutants in water, advanced treatment technologies are crucial in the treatment process. Recalcitrant pollutants in environmental matrices can be effectively treated by UV/H2O2. UV/H2O2 can convert contaminants into biodegradable intermediates or result in the complete/ultimate mineralization of contaminants, but they also have some drawbacks, such as forming more stable and toxic intermediates, using energy and chemicals, and increasing treatment time and cost. Considering the water quality objectives, water source quality, and process combinations of different water treatment companies, there has been a lack of comprehensive and systematic methods to address the complexity of water treatment process. In view of the characteristics of abundant algae and high organic micro pollution in the Pearl River water source in Guangzhou, this research developed a comprehensive pilot plant of UV/H2O2 advanced oxidation combination process, in which ceramic membrane was used as pretreatment process and activated carbon was used as post-treatment process. The synergy between UV/H2O2 process and upstream and downstream processes and the optimization of integrated process were systematically evaluated. The results demonstrate the effectiveness of the optimized combination of UV/H2O2 processes. This provides a research foundation for the large-scale application of UV/H2O2 combination processes with low chemical consumption, low energy consumption, and low cost in the future.

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

UV-C room disinfection devices are reduced in efficacy on distant, angled, and shadowed surfaces. New autonomous UV-C device placement strategies may be less impacted by these limitations than non-autonomous strategies; however there is limited data for direct comparison.

An experiment was conducted with a modified remote-controlled UV-C emitter (254 nm) to compare the dosages achieved on surfaces using competing UV-C room disinfection emitter position strategies: whole-room, spot, and autonomous. Ten commercially-available electronic radiometers were placed in an approximate grid configuration throughout real-world hospital challenge settings which included a patient room, an operating room, and an emergency room bay. The radiometers’ distance, angle, and exposure relative to the UV-C emitter positions were measured, and environmental variables that may have impacted UV-C irradiance, including temperature and humidity, were recorded.

A triplicate of 10-minute disinfections were performed in the challenge settings using each competing placement strategy. A secondary analysis of a commercially-available autonomous UV-C device was compared to the modified emitter’s autonomous placement.

The autonomous strategy achieved significantly higher overall UV-C dosages than whole-room and spot placement strategies. Further, all sensors received a measurable amount of UV-C dosage using the autonomous strategy. In our secondary analysis, the modified emitter performed similarly to the commercially available device using the autonomous placement strategy.

Our results demonstrate an autonomous UV-C placement strategy reduced the distance and improved exposure to radiometers within the challenge settings, leading to higher overall UV-C dosages and fewer shadowed surfaces compared to non-autonomous placement strategies.

Co-Authors: Aadi Gannavaram

Approximately two billion people in the world today lack access to safe drinking water, and many countries, including the US, struggle to meet safety standards for drinking water. The lack of safe drinking water leads to 485,000 child deaths annually, primarily affecting rural, low-income populations. The increasing use of bottled water as an alternative causes excessive plastic pollution. Current water purification devices use physicochemical methods and UVC irradiation, which is conventionally produced by low-pressure arc lamps that use mercury, a known health and environmental hazard. The use of UVC is limited due to high costs and lower device lifetime. By leveraging the synergistic effects of heat and UVA (not UVC) radiation and utilizing the UVA's unique strengths, we have developed an innovative, efficient, and inexpensive water purification device that achieves high throughput. A higher UVA energy output of 2.5J/cm2/sec is obtained by applying a higher current to the LEDs. The heat byproduct from overdriving the LEDs is extracted by the water, raising its temperature to 35oC. The synergy between intense UVA radiation and heat is used to disinfect the contaminated water to the same efficacy as UVC irradiation. Our prototype has demonstrated up to 1 Liter/min of water purification and > 5 log reduction in microbial load. A point-of-use water disinfection device based on UVA LEDs has the potential to provide safe drinking water to millions globally and to eliminate plastic waste towards achieving sustainability goals.

Co-Authors: Dr. Avinash D. Kulkarni

Ultra-Violet Germicidal Irradiation (UVGI), a technology for inactivation of microbes in air by exposing it to UVC radiation, is well established. The pandemic of Covid 19 has led to a keen interest in this technology as this technology can prevent the spread of the microbes to a great extent through a resulted air or surface disinfection. The limitation of UVGI technology is that due to harmful nature of the radiation many times it cannot be used during human occupancy. The current device under study addresses both these source problems with the dual mode application of air and surface disinfection. In the first mode of operation, it can disinfect surfaces and the air volume exposed during non-occupancy in the room whereas in the second mode it can disinfect air even during human occupancy. The system has demonstrated >log 1 reduction when operated in air disinfection mode and >log 3 reduction when in surface disinfection mode. Detailed results will be presented in this paper.

Co-Authors: Seyyed Arman Hejazi

Advanced oxidation processes (AOPs) are based on the oxidation of organic molecules with strong oxidants, typically hydroxyl radical (·OH), in order to degrade organic contaminants, present in water. UV radiation in combination with hydrogen peroxide (H2O2) can result in the generation of reactive species, such as hydroxyl radicals (HO•) in water, and lead to advanced oxidation decomposition of organic pollutants. We developed a new electrochemical photoreactor to electrochemically produce H2O2, using the oxygen of ambient air, hydrogen from water, and electricity. We then coupled the electrochemical cell with UV-LEDs and Microplasma UV radiation sources to convert the in situ generated H2O2 to ·OH.

The systems were characterized based on the applied current density and the water flow rate. The reactors exhibited Faraday efficiency values of 80–90% over a wide range of charge densities. A UV-LED array and three microplasma lamps, two with monochromatic wavelengths of 172 nm and 222 nm, and a polychromatic pattern of 220–280 nm, were studied. The degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and methylene blue (MB) was investigated as models of organic contaminants. A 2,4-D degradation of >70% was obtained at a UV-LED output of 900 mW and a MB removal of >30% was achieved with a microplasma UV output of about 300 mW. A higher degradation of organic contaminants will be obtained with the devices by reactor design optimization and utilizing more powerful UV-LEDs and microplasma UV lamps. The results suggest that these systems can successfully degrade low concentrations of organic contaminants, which indicates their suitability for a POU water treatment system.

Co-Authors: Muersha Wusiman

Recent advances in a new UV source, the ultraviolet light-emitting diode (UV-LED), create the opportunity for the development of novel UV-based technologies and devices, such as developing novel sensors. UV-LEDs can be applied as the excitation source of a photo-activated sensing layer for gas and liquid detection. This is significant, because there is an unmet demand for real-time frequent monitoring of water quality in many industries, including the drinking water, wastewater, agriculture, and aquaculture industries. We met this demand by shifting the time-consuming and expensive laboratory-based analysis to onsite, rapid detection of water contaminants via a UV-LED activated water quality sensor.

In our study, the first of its kind, a solid-phase fluorescence sensing platform was developed to detect chemical contaminants in water. ZnO quantum dots (QDs) were combined with molecularly imprinted polymers (MIPs) to form fluorescence sensing materials. The fluorescence light emission from the UV-activated sensing layer was quenched in the presence of contaminants that absorbs the excited state of the emissive electrons. By analyzing the colour intensity of the images using a portable fluorescence detector, the concentration of contaminants was estimated. The solid sensing platform was tested with 2,4-dichlorophenoxyacetic acid (2,4-D) and algae toxin Microcystin-LR (MCLR) as model contaminants, which demonstrated a high sensor sensitivity of the sensing platform. The results showed the capability of the proposed sensors to detect water contaminants with good sensitivity and selectivity, thus opening new opportunities for portable UV-LED activated sensor development. The high performance, target flexibility, and ease of use of the developed platform can be the basis for developing lab-on-chip image-based sensing devices for environmental applications.

Co-Authors: None

Excitation of luminescent material by electrons is a well understood technology with a low-cost and scalable approach to generating photons. Deep Light Photonics. Inc has developed a proprietary formulation of phosphors that produces polychromatic emission in the UV-C regime with four peak wavelengths at 232nm, 242nm, 261nm and 272nm without the use of mercury or other toxic materials. Additionally, 190nm devices to produce ozone have been developed for AOP based disinfection devices.

The eUV® device operates in high-current pulse mode with a 100us pulse width and a repetition rate of up to 1.25kHz across a 20 cm^2 emission area. Optical output greater than 400mW has been measured. Lamps can also be combined into arrays for even greater area coverage and optical power. Biological testing comparing four different UVC light sources, 222nm excimer, 277nm LED, and low-pressure mercury has demonstrated that the eUV requires almost ten times less optical power for equivalent log reduction.

With polychromatic emission there are multiple ways to inactivate pathogens affecting DNA, RNA or protein structure with different UV-C wavelengths. Every microorganism has a different vulnerability to wavelengths in the UV-C spectrum – the pathogen’s particular action spectrum.

In the surface disinfection market, the device can be used for UV curing, food processing, cannabis growing facilities and surface cleaning. Air flow applications include odor control, sterilization and food preservation. There are many potential applications for water, including pools and spas, aquaculture, life sciences, wastewater, drinking water and water reclamation. All without the risk of leaking toxic materials into the environment; clean and green.

Co-Authors: .

UV technology is established in many areas from industrial processes to the treatment of water or air. There is always a lot of attention when new technologies are discussed. However, improvements in technologies that are already established on the market, such as the use of UV mercury lamp technology, should be viewed far more inconspicuously but not less attentively.

The talk’s aim is on the one hand to introduce a new Synthetic fused silica – undoped and ozone free doped – on the other hand how this material behaves in UV lamps (185nm/254nm and only 254nm).

Synthetic fused silica is the purest available quartz quality to build UV lamps. Undoped versions allow high transmissivity of light in the VUV region. Ti-doped quartz glass allows ozone free lamps (transmission only above 220 nm), with very high transmission at 254 nm (no absorption, only reflections losses). We present Purasil V, which was developed to reduce costs, while the production process was optimized for OH content >100 ppm despite electric fusion in inert atmosphere. We explain the related aging mechanisms for low and high OH content with respect to aging of the material under permanent UV irradiation in a UV lamp.

Low-pressure mercury lamps are used for many decades in UV disinfection systems for air and water treatment. Recent increases in energy prices put a new emphasis on total cost of ownership calculations and will increasingly so in the future. Therefore, the new undoped Purasil V was validated for the use in ozone generating lamps – with immediate cost benefits. Additionally, the Ti-doped quartz was applied for ozone free disinfection lamps. Improvements in quartz glass degradation result in a higher UV quantum yield for each lamp with less radiation losses in the quartz glass. Higher material cost of purer synthetic quartz glass can be overcompensated by energy savings. This leads to lower total costs of ownership for synthetic Ti-doped UV disinfection lamps by energy savings, reduced number of bulbs in reactor design and less service cost due to longer lifetime.

User’s benefit:

• Higher UV Output, new x %, increasing with operation time by x %
• Expected increased lifetime (EOLL) by +xxxx h
• Energy savings

Co-Authors: Takeshi Tanaka,

Microbial inactivation using ultraviolet (UV) light has been actively studied using mercury vapor lamps, variable wavelength lasers, and light-emitting diodes (LEDs). In recent years, ultraviolet LEDs (UV LEDs) have been developed with various wavelengths and have attracted attention of many designs due to the numerous benefits solid state technology, like UV LEDs, offer vs. traditional technologies. However, since no evaluation system or method suitable for UV LED evaluation has been established, irradiation conditions vary from study to study.

This variability of existing research makes the results less conclusive and less useful for regulatory bodies building standards or companies seeking to develop UVC technology.

In particular, differences in optical characteristics, wavelengths, and irradiation doses between different wavelength LEDs and conventional light sources prevented proper evaluation and comparison. To clarify the effects of UVC LED irradiation on microorganisms, comparative studies using standardized light emitting devices and methods to evaluate the UV LED sensitivity of microorganisms were needed.

To fill this need, Nichia prepared LEDs with various wavelengths from 250nm to 365nm (250, 253, 257, 260, 263, 267, 270, 275, 280, 290, 300, 308, 365nm), and a new UV irradiation system was developed by strictly considering LED electrical temperature characteristics, UV irradiation, irradiation uniformity, irradiation time, light irradiation angle, reflection of surrounding materials, and sample temperature.

In addition to presenting the above, Nichia will also outline the impact of these thirteen UV LEDs using the irradiation system on the disinfection efficiency of several bacteria, viruses, and fungi. This is the first comprehensive study focused solely on UVC LED devices and will provide the industry with a solid foundation on which a standard for evaluating the inactivation of UVC LEDs as an alternative to mercury can be built.

Co-Authors: Bruno Ferran, Antoine Eid

The water treatment plant has been using bioassay dose (MS2 dose of 30mJ/cm2) and the effluent count (less than 126 MPN/100 ml 30-day Geo. mean) as the design criteria for many decades. However, the target microorganism effluent count cannot be estimated from those data because the bioassay uses nearly linear dose response curve (such as T1/MS2) and the bacteria (Fecal or E-coli ) is having a tailing effect from the presence of suspended solid in the field. The CFD modeling simulations from this study will fill the gap and calculate the UV dose, log inactivation and Influent/ effluent count based on the MS2/T1, E-coli and Fecal coliform log inactivation curve, with the objective to provide useful information to optimize UV system designs in the field.

A common approach to measure the performance of a UV reactor is to conduct a bioassay test under worst-case approach hydraulics, with various flows, UVTs, lamp power settings using test microorganisms (MS/T1). However, bioassay testing only yields a log inactivation and then convert to a Reduction Equivalent Dose with the specific UV dose-response curve that was derived through collimated beam testing for a given test microbe (MS2/T1).

CFD modeling will use the same method as bioassay to simulate the UV module with the Collimated beam test curve from real water treatment plant and deliver the effluent count data. CFD modeling resolves both flow and intensity field and generates a dose distribution via a Lagrangian particle dose tracking, and then couple it with microorganism log inactivation curve to obtain the overall dose. It is a well-known tool that has been proven to accurately simulate the disinfection performance of UV reactors. It can reveal some hidden details from the bioassay and gives insight into the mechanism for flow and microorganism interactions with the UV field.

This paper will analyze different microorganisms with different sensitivity characteristics to UV-C irradiation and calculate the log inactivation and effluent count with dose response curve from real water treatment plant, especially those of bacteria’s having a tailing effect from the presence of suspended solids in the field. The target microorganism effluent count at 30mJ/cm of MS2 bioassay dose will be discussed with various water quality and influent count. Also, the required MS2 bioassay dose to meet the target microorganism effluent limit (less than 126 MPN/100 ml 30-day Geo. mean) will also be calculated.

Co-Authors: William A. Anderson, Valerie Ward

Presenter: Nazanin Yasoubi, MSc. Student in Chemical Engineering of University of Waterloo (Waterloo, Ontario, Canada) Email: nyasoubi@uwaterloo.ca

In this project, the impact of different operational parameters of PX-UV on the inactivation of L. monocytogenes, the main cause of listeriosis which could be a fatal food-borne disease, on stainless-steel (SS) was investigated. To address the lack of information concerning the effect of frequency on disinfection efficacy of PX-UV, a study of the effects of frequency, exposure time, and light angle was undertaken. Developing a mathematical expression to quantify disinfection can be helpful for sizing the device for various applications or to determine the minimum dosage needed to achieve a certain level of disinfection for a specific process and specific microorganism. Therefore, the UV disinfection kinetics for the PX-UV lamp and L. monocytogenes was quantified.

The results of the study proved that the log reduction of 5 (99.999%) was achieved by UV dosage of ~100 mJ/cm2 which is much lower than 12 J/cm2, the approved value by FDA. The study on various radiation angles and frequencies at constant dosage showed that the total dosage received at the surface was the most significant factor in achieving the desired disinfection and highlighted the importance of using radiometry on site to determine the actual fluence being applied at the specified location. However, as it was expected, increasing exposure time or frequency can increase the inactivation rate. It should be noted that at high frequencies, the dose per pulse was lower than at low frequencies when designing a device for a specific application. It has been proved that PX-UV could achieve the required dosage for L. monocytogenes inactivation much faster than other UV methods and PX-UV lamps do not experience the same heat dissipation issues.

Note: This project is sponsored by Solaris robots (mississauga, ON, CA). However, it is still s scientific project. So, I was not sure what to answer the last question.

Co-Authors: Jing Zhao, Emma M. Payne, Bryan Liu, Chii Shang, Ernest R. Blatchley III, William A. Mitch

Concerns over human health risks associated with chemical contaminants (micropollutants) in drinking waters are rising due to the increased use of reclaimed water or water supplies impacted by upstream wastewater discharges. Ultraviolet (UV)-driven advanced oxidation processes (UV-AOPs) using radiation sources that emit at 254 nm have been developed as advanced treatments to degrade contaminants, while those UV-AOPs can be improved towards higher radical yields and lower byproduct formation. Several previous studies have suggested that Far-UVC radiation (200–230 nm) is a promising radiance source to drive UV-AOPs because the direct photolysis of micropollutants and production of reactive species from oxidant precursors can both be improved. In this study, we summarize from the literature the photodecay rate constants of five micropollutants by direct UV photolysis, which are higher at 222 nm than 254 nm. We experimentally determine the molar absorption coefficients at 222 nm and 254 nm of eight oxidants commonly used in water treatment and present the quantum yields of the oxidant photodecay. Our experimental results also show that the concentrations of HO•, Cl•, and ClO• generated in the UV/chlorine AOP can be increased by 5.15-, 15.76-, and 2.86-fold, respectively, by switching the UV wavelength from 254 nm to 222 nm. We also point out the challenges of applying Far-UVC for micropollutant abatement in water treatment, including the strong light screening effect of matrix components (e.g., carbonate, nitrate, bromide, and dissolved organic matter), the formation of byproducts via new reaction pathways, and the needs to improve the energy efficiency of the Far-UVC radiation sources.

Co-Authors: Chii Shang, Ran Yin

Refractory halogenated contaminants (e.g., chlorinated industrial solvents, brominated flame retardants, and perfluorinated compounds) are resistant towards conventional water treatment processes and pose threats to eco-systems and human health. Advanced reduction processes (ARPs) are promising alternatives for dehalogenation of those contaminants in water. In this study, we developed a novel ARP by integrating Far-UVC radiation at 222 nm with sulfite (UV222/sulfite ARP) for rapid dehalogenation of five representative halogenated contaminants (2,2-bis(bromomethyl)-1,3-propanediol, fluroxypyr, 2,4,6-trichlorophenol, trichloroethylene, and perfluorooctanoic acid) in both deionized and real water matrix. Compared to direct photolysis by Far-UVC radiation, addition of 1 mM of sulfite enhanced the degradation efficacy of the contaminants by 1.5–8.9-fold in deionized water. The enhancement was attributed to the generation of hydrated electrons from Far-UVC photolysis of sulfite. The steady-state concentration of the hydrated electrons in the UV222/sulfite ARP (1 mM of sulfite at a UV fluence of 774 mJ/cm2) was determined to be 8.31 × 10-13 M at pH 7.0. The values was 51 times higher than those generated in the well-documented UV254/sulfite ARP under the comparable conditions. Increasing initial sulfite concentration (0.1–2 mM) and pH (pH 7.0–9.2) enhanced the generation of hydrated electrons. The quantum yield of hydrated electron generation from Far-UVC photolysis of sulfite was determined to be 0.123 mole/Einstein. It was incorporated into a kinetic model for prediction of hydrated electron generation and contaminant degradation in the UV222/sulfite ARP under varied environmental and operational conditions. This study discloses the fundamental photochemistry of sulfite at 222 nm and offers a novel strategy for rapid dehalogenation of refractory contaminants in water.

Co-Authors: Yihao Luo, Bruce Rittmann, Pedro Alvarez, Francois Perreault, Paul Westerhoff

Biofilms cause over $3 trillion annually in damage ranging from harboring pathogens, biocorrosion to medical infection. As an alternative to chemical control strategies, germicidal UV-C irradiation using LEDs presents new opportunities for inhibiting biofilm on surfaces. UV-C light launched from LEDs into flexible, thin side emitting optical fibers (SEOFs) can deliver germicidal light to nearly any surface geometry from basins to small diameter tubing. Using fully submerged surfaces in flowing water spiked with Pseudomonas aeruginosa, a SEOF delivered a UV-C gradient to the surface. Biofilm growth over time was monitored in-situ using optical conference tomography. Biofilm formation was inhibited to below 0.05 mm3/mm2 everywhere the 275 nm UV-C intensity was above 9 μW/cm2. Biofilm samples were collected from multiple regions on the surface: 1) inhibition zone where biofilm formation gets inhibited, 2) low intensity zone where biofilm inhibition failed, 3) control area without UV-C irradiation, and 4) thick biofilm area followed with excessive (400 mJ/cm2) UV-C irradiation. RNA sequencing of these samples observed that excessive UV-C intensities inhibit functional genes expression related to general metabolism, DNA repairing, mobility and biofilm formation compared to dark control. However, with non-lethal UV-C exposure, the SOS response and quorum sensing related genes are upregulated to defend the stress. And the transcriptional responses reveal that Pseudomonas aeruginosa behaves unique survival strategies (e.g., DNA repairing, increasing mobility and biofilm formation) at places where inhibition failed with relatively lower UV-C stress. These results imply the importance of maintaining enough UV-C exposure onto surface for microbial control in many scenarios.

Co-Authors: Jiangyong Hu

Water reuse is becoming an increasingly vital strategy for managing scarce water resources worldwide. A multi-barrier advanced treatment process consisting of ozonation (O3), biological activated carbon (BAC) and ultraviolet/chlorine (UV/Cl2) has been reported to be an effective process that can realize considerable organics removal, resistant contaminants abatement, and pathogens inactivation. The presence of micropollutants (MPs) in the reused water has been recognized as risks to environment and human beings, which makes the removal of micropollutants significant issues to ensure water safety. UV light-emitting diode (UV-LED) lights at different wavelength have been reported to have various impacts on micropollutants mitigation. This study investigated the removal of selected MPs in an effluent treated with O3/BAC/UV/Cl2 process and the associated toxicity of treated water. Two wavelengths of UV light resources (254 and 285 nm) and two oxidants (chlorine and chloramine) were used in advanced oxidation process (AOP) treatment. The removal efficiency of the MPs in O3/BAC/UV-LED/Cl2 treatment chain and the degradation kinetics of the MPs in UV-LED/chlor(am)ine AOP was studied. This study also evaluated the effects of various operating conditions such as pH, UV exposure, water matrix and oxidant dosages on MPs’ removal. The results indicated that the O3/BAC/UV-LED/Cl2 treatment chain was effective in removing MPs, and the degradation kinetics of the MPs in UV-LED/chlor(am)ine AOP were dependent on the wavelength of the UV light resources and the oxidant used.

Co-Authors: Karin Ziegler, Thomas Rathgen

In recent years, the sustainability of systems has become an increasingly important focus of industrial and domestic applications. A decisive factor in the evaluation of sustainability is the system efficiency including the power factor, the increase of which guarantees energy savings. The performance and UV-output of UV-systems are well known to be linked to the temperature of the water surrounding the lamp body. In an attempt to stabilize lamp behaviour throughout a wide temperature range, ZED GmbH has developed an On-Lamp, maintenance-free temperature driver for use in new and existing UV-systems. This so called Perfect Performance Tool (PPT) not only offers a higher power efficiency than common systems, but also stabilizes the UV Output of Out-Of-Arc-Lamps. ZED PPT-Lamps have the same dimensions as regular low-pressure amalgam lamps and no need for additional wires for operation.

Co-Authors: Greg Wetterau, Anna Ness

As potable reuse becomes an increasingly important component of water portfolios worldwide, design and operational challenges of piloting UV-AOP systems should be shared. In this presentation, we will present recent UV-AOP piloting data, challenge testing data and lessons learned from at least two large potable reuse pilot facilities in Florida and California. In Florida, data and learnings from the Palm Beach County Green Cay pilot will be presented. The California case studies will be present data from a large MBR-RO-UV/AOP demonstration facility in Southern California as well as a 0.5 MGD pilot facility that is currently under construction. Additional facilities in the states of New Mexico and Colorado will be referenced as we compare our lessons learned over the past 5 years while designing, piloting and troubleshooting UV/AOP approaches for potable reuse. Recent challenge testing data for NDMA and 1,4-dioxane will be presented as well as adjustments made to manage UVT.

Our presentation will be organized as follows:

• Design learnings 
• Data presentation and learnings 
• Operational learnings 
•  Implications to full-scale facilities

Refractory halogenated contaminants (e.g., chlorinated industrial solvents, brominated flame retardants, and perfluorinated compounds) are resistant towards conventional water treatment processes and pose threats to eco-systems and human health. Advanced reduction processes (ARPs) are promising alternatives for dehalogenation of those contaminants in water. In this study, we developed a novel ARP by integrating Far-UVC radiation at 222 nm with sulfite (UV222/sulfite ARP) for rapid dehalogenation of five representative halogenated contaminants (2,2-bis(bromomethyl)-1,3-propanediol, fluroxypyr, 2,4,6-trichlorophenol, trichloroethylene, and perfluorooctanoic acid) in both deionized and real water matrix. Compared to direct photolysis by Far-UVC radiation, addition of 1 mM of sulfite enhanced the degradation efficacy of the contaminants by 1.5–8.9-fold in deionized water. The enhancement was attributed to the generation of hydrated electrons from Far-UVC photolysis of sulfite. The steady-state concentration of the hydrated electrons in the UV222/sulfite ARP (1 mM of sulfite at a UV fluence of 774 mJ/cm2) was determined to be 8.31 × 10-13 M at pH 7.0. The values was 51 times higher than those generated in the well-documented UV254/sulfite ARP under the comparable conditions. Increasing initial sulfite concentration (0.1–2 mM) and pH (pH 7.0–9.2) enhanced the generation of hydrated electrons. The quantum yield of hydrated electron generation from Far-UVC photolysis of sulfite was determined to be 0.123 mole/Einstein. It was incorporated into a kinetic model for prediction of hydrated electron generation and contaminant degradation in the UV222/sulfite ARP under varied environmental and operational conditions. This study discloses the fundamental photochemistry of sulfite at 222 nm and offers a novel strategy for rapid dehalogenation of refractory contaminants in water.

The potential of using short wavelength ultraviolet (UV-C) rays for disinfecting coronavirus were explored by firms as governments relaxed certification requirements during the COVID 19 pandemic. Before the pandemic UV-C sterilizers were largely used at laboratories by trained personnel, which is now permitted to be sold as a consumer appliance. Most e-commerce portals allow buyers to submit consumer reviews of an item purchased from their website. For UVC sterilizers sold in e-commerce platforms, these reviews provide reliable data directly from customers who are the end-users on how the device was operated, used and performed. The underlying motivation for this research are 1) customers cannot judge the sterilization efficacy of UV-C sterilizer, as the virus cannot be perceived by the naked eye, and requires laboratory test; 2) the potential hazards to untrained users during operation of UVC sterilizers. Combining sentiment analysis with categorical tagging of the 503 customer reviews of 75 UV-C sterilizers from e-commerce platform Amazon, the authors critically assessed its use by untrained users. Supervised classification algorithms were used to predict safety issues from customer reviews. The outcome of this research can help governments and agencies monitor emergency products permitted without certifications to address health situations like the pandemic.

Cronobacter spp. is highly tolerant to desiccation and are capable of surviving in very dry environments and thus poses a significant food safety challenge in dried and desiccated foods. UV-C has been used to inactivate pathogens in air and on high contact surfaces. However, fluences required to inactivate desiccated Cronobacter spp. on surfaces is not know. Determine the fluences required for incremental inactivation of Cronobacter sakazakii desiccated on polystyrene surfaces. Three dairy isolates of C. sakazakii (CS1212, CS1214, CS1216) were individually desiccated on polystyrene surfaces and treated with UV-C doses of 0 to 30 mJ/cm2 using a collimated beam device emitting UV-C at 253.7 (LPM), 265 (LED), or 285 (LED) nm. Exposure time for each UV dose was calculated using IUVA approved methods. All experiments were performed in triplicate. The log reduction from each treatment was identified using the plate count method and plotted against UV-C dose. The UV-C dose required for incremental inactivation for each isolate (non-desiccated and desiccated) was determined using linear and nonlinear regression. All results were analyzed using ANOVA, followed by a Tukey’s test at a 95% confidence level to determine significant differences in log reductions between non-desiccated and desiccated cells for each UV-C dose and strain.

UV doses required to inactivate non-desiccated and desiccated cells of Cronobacter spp. were not significantly different. However, doses required to inactivate Cronobacter spp. on surface were three time higher than those required to achieve similar inactivation of cells in suspension. For instance, 8.55 mJ/cm2 (253.7 nm) was required to achieve a 4-log inactivation of CS1214 cells in suspension, while doses >30 mJ/cm2 was required to achive similar inactivation of cells on surface.

Desiccation does not enhance UV-tolerance of C. sakazakii. Significantly higher UV doses are required to inactivate C. sakazakii on surfaces. The presentation will provide details on fluences at 265 and 285 nm required to inactivate C. sakazakii on surfaces.

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.

This presentation will showcase the outcomes of our experimental analysis, where we compare the disinfection performance of UVC with alternative methods like photocatalysis, and filtration against E. coli. Additionally, we will showcase the test results of our technology as evaluated by an independent laboratory against SARS-CoV-2. We will demonstrate how our patented collimation technology, IntenseBeam, enables precise adjustment of UV-LED radiation through a series of optical lenses, resulting in significant advantages for the design of air disinfection units. Furthermore, using 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. 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).

Ultraviolet light emitting diodes (UV-LEDs) offer low energy consumption and maintenance-free operation, making them an advantageous solution for water disinfection systems from point of use (PoU) to point of entry (PoE). Same as any state-of-the-art technology, UV-LEDs as an alternative to conventional UV lamps need to be proved as (I) effective, (II) reliable, (III) eco-friendly, (IV) compact, (V) user-friendly, (VI) easy to integrate, and (VII) cost-effective to be able to be introduced and established into the current market. All mentioned specifications can be addressed through a careful system design and validation strategy for various application from PoU to PoE which will be discussed in this study. To name a few, the effectiveness of UV-LED devices to reach high log reduction values (+6-log) is demonstrated through case studies of various PoU and PoE devices at range of flow rates involving heavily contaminated water with various benchmark microorganisms, including E. coli, Pseudomonas, Legionella, Q-beta, and MS2. It is found that precise design of radiation pattern and hydrodynamics inside the reactor is crucial for maintaining robust performance, as inadequate practices can lead to varying disinfection regimes within a single system. Reliability and performance consistency over product lifetime is shown to be crucially dependent on the precise optical and hydrodynamics design of the reactor for End-of-Life (EoL) considering water dissolved minerals. Inherent nature of UV-LED solid state enables application of various Internet of things (IoT) integration to use matrix of data to monitor the device health and performance. These findings offer valuable insights for configuring viable water treatment solutions for off-grid applications and remote communities.

UV disinfection has by now become an established Cryptosporidium and Giardia barrier for today’s potable water suppliers and forms part of every multi-barrier disinfection concept. However, when existing waterworks seek for installing a UV system within their treatment train, they often face issues on how to fit it into existing pipe works. As the UV system is supposed to be located after the filter gallery, space limitations were in the past typically driving the need for a new building to accommodate the UV equipment. Significant pipework adjustments become necessary to feed the flow to the UV systems after the filter collection pond along with additional pumping stations whenever sufficient head is not available. Overall this made the integration of a UV system into existing waterworks quite a complex project with significant time, costs and risk associated.

Research on alternative UV reactor concepts have now led to an innovative new reactor design that allows to fit UV equipment even into space constraint areas. An ultra-compact reactor design equipped with powerful medium pressure UV lamps requires as little as 30 to 50 cm pipe length to fit in. This makes the new reactors suitable for integration into almost every filter gallery directly after the individual filters. While medium pressure UV lamp systems are known to be less energy efficient as compared to low pressure high output amalgam lamp systems, the overall benefits and cost savings for waterworks associated with this alternate UV system integration are significant and easily compensate the differences in lamp power consumption.

The presentation will share more insight of this innovative approach, which will help waterworks to easily integrate UV disinfection within their multi-barrier approach. Based on a recent case story, benefits during planning, construction and operation will be discussed and illustrated.