We previously introduced guv-calcs and Illuminate, an open-source Python library and web application for modeling germicidal UV irradiance and fluence rate in indoor environments [1]. Both components have since undergone substantial development, transforming from a research prototype into an interactive platform for GUV system design.

The web frontend, Illuminate, has been completely rebuilt using SvelteKit and Three.js, providing real-time 3D visualization of rooms, lamps, and calculation results with instant visual feedback. Lamp placement and aiming are handled through point-and-click interaction and quick-placement controls, and room dimensions, positions, and calculation zones can be edited fluidly. Additional tools include a spectrum viewer, design audit panel, and susceptibility data explorer.

Guv-calcs has gained several capabilities for modeling realistic indoor environments. An occlusion module computes soft shadows cast by obstacles, enabling simulation of furnished or partitioned spaces for the first time. Support for non-rectangular room geometries allows modeling of arbitrary polygonal floor plans. Eye dose calculation modes simulate realistic ocular exposure by orienting calculation zone normals toward a defined target point or in a uniform gaze direction, with configurable vertical and horizontal fields of view — enabling analysis of scenarios such as lecture halls, waiting rooms, or spaces with a central focal point. A coarse grid subsampling method improves accuracy in scenarios where lamps are positioned close to calculation grid points, significantly smoothing whole-room fluence estimates. The library also introduces single-point calculation zones for witness point spot-checks, automated batch lamp placement and aiming operations for efficient multi-fixture layouts. The Illuminate application is available at www.illuminate.osluv.org

Diarrheal diseases remain a major global health challenge, with Vibrio cholerae responsible for an estimated 1.3 to 4 million infections and 95,000 deaths annually. Cholera outbreaks are most frequent in regions lacking reliable water treatment infrastructure, where conventional centralized treatment and disinfection methods may be inaccessible or inconsistently used. Among modern water treatment approaches, UV disinfection has emerged as an efficient, chemical-free method capable of inactivating a wide range of microorganisms. However, the inactivation kinetics and underlying mechanisms of V. cholerae inactivation under varying UV wavelengths has not yet been fully characterized.

UV light-emitting diodes (UV-LEDs) have emerged as a promising decentralized treatment technology given their compact size and durability, low power consumption, absence of mercury, instant start-up combined with their efficacy at inactivating waterborne microorganisms and viruses without producing disinfection byproducts. This project aims to evaluate the dose-response kinetics for UV-LED inactivation of V. cholerae and V. harveyi, a potential surrogate microorganism, at 265 and 280 nm as well as synergistic inactivation by UV-A followed by UV-C light. Understanding how V. cholerae responds to these wavelengths will help optimize treatment systems using UV-LEDs for disinfection of drinking water and wastewater in decentralized settings. We hypothesize that applying UV-A prior to UV-C will cause synergistic effects of up to 2-log reduction of V. cholerae, as has been demonstrated in E. coli due to UV-A induced damage of the transfer RNA, which makes the cell more susceptible to subsequent DNA damage induced by UV-C. The goal of this research is to contribute to the development of sustainable, resource-efficient, and broad-spectrum decentralized disinfection systems capable of addressing microbial contamination in potable water, and in wastewater prior to discharge, for areas prone to cholera outbreaks.

Ultraviolet light-emitting diode (UV LED) devices have recently emerged as promising alternatives to low-pressure UV mercury vapor lamps for water disinfection. In contrast to widely used chlorination, UV disinfection does not introduce halogen species associated with the formation of halogenated disinfection byproducts (DBPs). However, some UV LED devices contain surfaces or internal components manufactured from polytetrafluoroethylene (PTFE), commonly known by the brand name Teflon™, through which water passes during treatment. PTFE has been shown to leach per- and polyfluoroalkyl substances (PFAS), a class of persistent environmental contaminants often referred to as “forever chemicals.” Numerous studies have documented the toxicological impacts of PFAS on human and ecological health. The United States Environmental Protection Agency (US EPA) regulates six known PFAS contaminants, and previously considered only individual compounds as candidates for regulation. As of April 2026, the US EPA has proposed a class-based approach, defining PFAS as a chemical group, broadening the number of candidate compounds for regulation. Similarly, Health Canada recently lowered the concentration limit for the sum of 25 PFAS listed in the national drinking water quality guidelines.

To date, no published studies have investigated PFAS leaching from UV LED disinfection devices during operation or stagnation periods. This study investigates both targeted and non-targeted PFAS in the effluent of a commercially available UV LED disinfection reactors under representative operational scenarios, including continuous operation and water stagnation conditions. Preliminary findings suggest that trace PFAS compounds may be detectable following prolonged water contact with PTFE-containing internal components, with higher concentrations potentially observed after stagnation periods. The results will provide important insight into the chemical safety of UV LED drinking water technologies and support future UV reactor material selection, device optimization, and regulatory assessment of UV LED-based water treatment systems.

UV/advanced oxidation process (UV/AOP) is a cornerstone of potable water reuse treatment trains, providing both pathogen inactivation and chemical contaminant reduction. Although highly effective, successful operation requires balancing treatment performance with the electrical and chemical demands of the system. In potable reuse applications, two primary approaches have emerged for monitoring and control of UV/AOP systems: critical control setpoint (CCSP) and log-reduction value (LRV)-based control.

CCSP is a conservative framework in which water quality parameters must remain within fixed, permit-defined limits established through rigorous validation under simulated worst-case water quality conditions. This approach provides a high degree of confidence in treatment reliability; however, it can reduce operational efficiency because it effectively assumes worst-case water quality even when actual conditions are more favorable. In contrast, LRV-based control uses algorithms and real-time water quality measurements to adjust UV dose and oxidant addition, maintaining required treatment performance while improving energy and chemical efficiency. This dynamic approach can enhance operating flexibility and reduce costs, though it may not provide the same margin of conservatism as CCSP.

This presentation will draw on startup and commissioning data from recent UV/AOP installations to compare these two control strategies in terms of treatment efficiency, operational optimization, permitting considerations, and monitoring complexity. The discussion will highlight practical tradeoffs and provide insights for utilities and vendors evaluating control philosophies for future potable reuse projects.

Reduction equivalent dose (RED) is widely used to describe and evaluate UV reactor validation and performance. RED reflects the combined effect of reactor dose distribution and the UV dose response of a target organism or compound. The UV sensitivity of a target is commonly described by D10, defined as dose per log inactivation (mJ/cm2/log). As a result, the same UV reactor operating under identical hydraulic and optical conditions may produce different RED values depending on the target considered. This effect can become more significant in reactors characterized by broad dose distributions. RED bias associated with different D10 values has been recognized in microbial UV validation applications and incorporated into the USEPA UVDGM. However, the implications of this behavior have not been widely explored for chemical compounds with substantially higher D10 values relevant to UV/AOPs, where D10 values can exceed 1000 mJ/cm².

In UV/AOP systems, high-D10 photolytic species such as chloramines, free chlorine, and hydrogen peroxide play important roles in determining hydroxyl radical steady-state concentrations and may respond differently to non-uniform reactor dose distributions. Although RED differences among high-D10 compounds are often assumed to be small, they may still become significant depending on reactor design and dose distribution characteristics. Improved understanding of this behavior is important for interpreting and predicting UV/AOP reactor performance.

This presentation will discuss how RED varies for high-D10 compounds in UV/AOP reactors with different reactor designs and dose distributions. The impact of these differences on UV/AOP performance prediction and interpretation will also be presented.

Accurate prediction of ultraviolet (UV) fluence rate delivered within solar water disinfection systems is crucial for ensuring reliable disinfection performance. This prediction requires optical modeling that captures the effects of solar spectral irradiance, reactor geometry, and the wavelength-dependent optical behavior of reactor materials. This is complicated due to the high variably of solar spectral irradiance on short temporal scales.

In this work, we present an automated simulation framework that integrates spectral irradiance from the Tropospheric Ultraviolet and Visible (TUV) radiation model with the Photopia raytracing model (LTI Optics) to evaluate performance of reactors for solar water disinfection. The model uses python-based automation to systematically iterate through discrete ambient solar UV wavelengths, reactor geometries, and solar input based on location, date, and time of day. Monte Carlo ray tracing is performed through the domain, and the resulting fluence rate distribution within the reactor cross-section at multiple locations is recorded and stored for post-processing. Further, the sensitivity of reactor performance predictions to atmospheric uncertainties was evaluated. This automation substantially reduces manual simulation effort and enables systematic evaluation across large parameter spaces. The effect of TUV input parameters, including the ozone column, aerosol optical depth, and cloud cover, on the resulting fluence field was assessed. Additionally, measured spectral irradiance data from the USDA UVB Monitoring and Research Network were incorporated to benchmark variability in results with measured data. This work is intended to advance the design and optimization of reactors for solar water disinfection under realistic solar and atmospheric conditions.

Abstract: It has been debated since the introduction of Far UV for Whole room disinfection which method of disinfection is more effective to use, whole room or upper room GUV. Upper room GUV has been used for almost 100 years to combat Tuberculosis and other airborne pathogens. The introduction of 222nm Far UV in in the late 2010’s has been considered a safe GUV wavelength for skin and eyes and with the update of the IEC62471 standards in early 2021 it has been deemed even more safe for skin and eyes than initially thought.

Upper room GUV using 254nm mercury source and more recently 265nm LED’s has high output power but is limited in the amount of radiation that can be in the room below head level. This limitation allows for light particle airborne disinfection but does not help with medium size airborne particles in the room that do not circulate upward and tend to land on surfaces to be stirred up again with movement in the space. Upper room GUV requires the pathogen you are trying to mitigate to migrate into its kill zone above the head or requires added help such as a ceiling fan to help the migration.

222nm Far UV does not require the migration of any particles toward the light source since the source can be put on the ceiling or high on a wall and be directed down into the room. The position of the 222nm source will also allow for disinfection of surfaces as well as air. The drawback with Far UV is the limited number of studies on the safety and efficacy of 222nm as well as the generally lower power level of the source. The 2 GUV methods Upper and Whole room can be combined together to achieve better surface and airborne disinfection than just having a single GUV solution. Measuring of the 2 different wavelengths will be a challenge that can be addressed to safely install a fixture combing the 2 GUV sources to prepare for all types of airborne and surface pathogens. Design of the fixture can allow it to be placed on the wall or center of the room and allow for a zone of coverage encompassing most of the room below head height and most of the room above head height without requiring significant mixing

Trifluoroacetic acid (TFA), an ultrashort-chain perfluoroalkyl carboxylic acid, is a known ubiquitous and highly mobile environmental contaminant. TFA’s stability combined with it being a common transformation product of many fluorinated organic compounds, has led to growing concern over the continual accumulation of TFA in the environment. One such reported source of TFA comes from the photolysis of fluorinated agrochemicals and pharmaceuticals, the use and number of which have been increasing. Recently, krypton chloride (KrCl*) excimer lamps emitting far-UVC 222 nm radiation have gained significant attention as a promising novel UV source that is both safer and emits higher energy photons than conventional 254 nm low-pressure mercury UV lamps (LPUV). However, the impact of far-UVC on TFA formation from fluorinated compounds has yet to be characterized. Thus, the objectives of this research are to compare photolysis rates and TFA yields of selected fluorinated agrochemicals and structurally related compounds under far-UVC and LPUV, as well as elucidate how the structure of organofluorides influences the risk of TFA release. To achieve these objectives, we dissolved different model benzotrifluorides and agrochemicals in water and subjected them to UV irradiation using a semi-collimated beam apparatus. Far-UVC enhanced both fluence normalized photolysis rates and TFA yields compared to LPUV. Trifluralin yielded 1.1% TFA under far-UVC compared to 0.2% under LPUV after 8 J*cm of irradiation. When it came to structural trends, the addition of electron-withdrawing groups to the aromatic ring of benzotrifluorides suppressed photolysis rates while enhancing TFA yields. The molar TFA yields of 4-trifluoromethylaniline, 4-Amino-3-nitrobenzotrifluoride, and 4-Amino-3,5-dinitrobenzotrifluoride were 0.7, 3.1, and 5.0% respectively under far-UVC and negligible for all three compounds under LPUV. Finally, the higher photolysis rates under far-UVC were driven by higher molar absobtivity coefficients, while more electron withdrawing substituents reduced photolysis rates by lowing quantum yields.

Biofilms can persist on intermittently dry surfaces in water storage and distribution systems, creating microenvironments that protect microorganisms from environmental stress and disinfection. While UV irradiation is widely used for microbial inactivation, its performance against viruses embedded within or shielded by dry biofilm matrices remains poorly understood. This study investigates the protective effect of dry biofilms on MS2 bacteriophage, a conservative viral surrogate, on materials representative of internal water reservoir surfaces, including stainless steel, borosilicate glass, and polycarbonate. Biofilms were grown on each material, dried under controlled conditions, inoculated with MS2, and exposed to calibrated UV irradiation. Viral infectivity was quantified following UV treatment to estimate dose-response kinetics, log10 reduction values, and biofilm-associated protection factors compared with MS2 deposited directly on clean surfaces.

The study evaluates how UV wavelength and dose as well as surface material and biofilm structure influence biofilm-protected MS2 persistence and inactivation, which is important since extracellular polymeric substances within the biofilm can attenuate UV through increased optical path length, light scattering, UV-absorbing components, and reactive oxygen species scavenging. Biofilm UV susceptibility varies by wavelength, surface properties, and biofilm composition, with biofilms requiring higher fluence than planktonic organisms and showing dose-response tailing due to resistant subpopulations.

By focusing on dry biofilm-virus systems, this study addresses a critical knowledge gap for UV disinfection design in indoor spaces, water storage devices, reservoirs, and reusable containers. The findings will support improved UV fluence targets for biofilm-associated viral contamination and help determine whether surface-specific UV validation is needed for reservoir and point-of-use water applications.

Monkeypox virus (MPXV), an Orthopoxvirus of continuing global public health concern, can persist on contaminated materials and may contribute to indirect transmission in healthcare, household, and outbreak-response settings. Although chemical and laundry-based decontamination approaches have recently been evaluated for MPXV, there remains limited comparative evidence on ultraviolet (UV) inactivation across MPXV clades and emerging UV wavelengths. Our study quantifies wavelength-specific UV dose-response kinetics for MPXV clades Ia, Ib, IIa, and IIb using four irradiation sources: far-UVC at 222 nm, conventional low-pressure UV-C at 254 nm, and UV-LEDs at 265 and 278 nm. MPXV will be exposed to calibrated UV doses under in a BSL-3 laboratory for human pathogens, and residual infectivity will be measured using standard viral enumeration assays. Dose-response models will be fitted to estimate inactivation rate constants, D90 values, and the fluence required to achieve at least 3 log10 reductions or viable but non infectious state. Wavelength performance will be compared across clades and benchmarked against related poxviruses and viral surrogates, including Borealpox, and MS2 coliphage. The study is designed to clarify whether MPXV clades differ in UV susceptibility and whether far-UVC or UV-LED technologies provide practical advantages over standard 254 nm UV-C for environmental decontamination. Findings will support evidence-based UV design criteria for infection prevention and control, particularly for high-touch surfaces, air/surface disinfection systems, settings where chemical disinfectant supply is limited or where reduction of chemical use is targeted, or settings where human occupancy constraints limit existing approaches. By integrating pathogen-specific UV kinetics with emerging UV technologies, this work will help advance safe, validated, and fit-for-purpose UV applications for mpox outbreak preparedness and response.

Controlling In-Room Pathogen Exposure with a UV222 Robot Author: Sherylinn Hoang Phone: (951) 454-1270 Email: sherylinn@h7tech.com Respiratory infectious diseases, emerging viral threats, and antimicrobial-resistant microorganisms continue to expose critical limitations in traditional environmental hygiene practices, particularly in occupied shared spaces where microbial transmission often occur. Existing conventional ultraviolet germicidal irradiation (UVGI) technologies require unoccupied environments due to photobiological safety constraints, limiting operational flexibility and preventing continuous environmental decontamination in populated settings. Recent research utilizing 222 nm irradiation from KrCl lamps has demonstrated safe operation around humans while maintaining high efficacy against airborne respiratory pathogens, enabling UV disinfection in occupied spaces.

This project evaluated a patent-pending Far-UVC system engineered to continuously reduce airborne and surface-borne microbial contamination in occupied environments using filtered Far-UVC technology. Research findings demonstrated equivalent rapid inactivation of airborne viruses such as SARS-CoV-2, influenza, and tuberculosis, using a virus surrogate, while maintaining compatibility with safe operations in occupied-spaces. Three testing phases were conducted to optimize system performance and operational efficiency: irradiance distribution and emission spectrum characterization, surface disinfection across complex geometries with T1 phage virus, and bioaerosol chamber efficacy testing utilizing MS2 coliphage. Results from these studies were utilized toward system engineering and performance optimization of a new product, SURYA II™, a UV222 nm robot designed for use in high disease-burden environments.

The vision for this product integrates portable mobility, advanced algorithms, sensing capabilities, remote operation, and strategically engineered Far-UVC delivery to address persistent barriers associated with conventional UV disinfection systems and fixed-solution systems, including operational downtime, workflow disruption, shadowing, and the inability to support continuous disinfection in occupied-spaces. The ultimate design incorporates twelve Far-UVC modules for multidirectional irradiance distribution, adaptive operational controls, multiple safety features, real-time system monitoring, and targeted-area deployment to enhance environmental hygiene across high-traffic public settings.

This presentation will present the research results, engineering optimization, and translational development of an advanced UV-enabled technology for public health protection.

Trace organic contaminants (TrOCs) pose a significant economic and technical challenge for potable reuse, often requiring energy-intensive advanced treatment. This research investigates whether wavelength-tailored UV-LED technology can optimize Ultraviolet Advanced Oxidation Processes (UV/AOP), specifically using a novel combination, UVLED/Cl2, comparing against conventional LPUV/H2O2 in carbon-based advanced treatment (CBAT) trains.

The study utilizes a novel 282 nm UV-LED reactor housed in a DPR mobile demonstration pilot research trailer to evaluate performance. Unlike conventional systems, the UVLEDs, specifically peaking at 282 nm, align more effectively with the absorption characteristics of free chlorine at neutral to basic pH. This alignment potentially accelerates photolysis rates and may enhance the production of hydroxyl radicals and reactive chlorine species (RCS), and subsequent removal of trace organic contaminants.

Removal efficiency is quantified via Electrical Energy per Order (EE/O), providing a direct comparison of the power required for unit contaminant degradation. Additionally, a kinetic model is being developed to predict the complex photochemistry of the UVLED/Cl2 process. This work investigates how wavelength-specific LEDs might improve the efficiency, cost-effectiveness, and reliability of advanced oxidation in full-scale potable reuse applications. Preliminary results demonstrate that in CBAT reuse scenarios, UVLED/Cl2 can meet 0.5-log 1,4-dioxane removal under low flows and high chlorine concentrations but does not yet outperform LPUV/H2O2.

In direct potable reuse (DPR), reverse osmosis permeate (ROP) is the standard influent for Ultraviolet Advanced Oxidation Processes (UVAOP). While ROP is characterized by low concentrations of organic and inorganic constituents, resulting in extremely low hydroxyl radical (HO*) scavenging demand, the extent of scavenging variability across diverse, full-scale DPR matrices remains poorly understood. Furthermore, the low-matrix nature of ROP introduces analytical challenges, as the sensitivity of scavenging measurements can be influenced by experimental parameters.

This study performed a comprehensive characterization of over a dozen real-world DPR ROP samples to evaluate HO* scavenging demand using a LPUV/H2O2. Samples taken vary spatially and temporally, lending context to changes over time within a system, and between systems. Nitrobenzene was employed as a HO* probe to assess how operational variables, including irradiance, initial probe concentration, and oxidant dose, impact the accuracy and reproducibility of scavenging measurements. Recent work examining a similar water quality under LPUV/Cl2 will be compared.

Results indicate that irradiance and probe concentration can contribute to 50% variance in measured scavenging, and these outcomes are able to be modeled. These findings provide critical insights into AOP design, demonstrating that minor changes in ROP scavenging procedure led to significant changes measured scavenging, potentially resulting in full-scale adjustments in UV dose or chemical delivery to ensure consistent contaminant degradation and energy efficiency.

The USEPA’s Innovative Approaches document specifies using UV dose algorithms that predicted log reduction (LR) as a function of UV absorbance (UVA) and a combined variable, RLO/Q/DL, where RLO is the relative lamp output, Q is the flow, and DL is the UV sensitivity of the pathogen whose log inactivation is predicted. A typical equation has the form:

LR=10^a*UVA^b*(RLO/Q/DL)^(c+d*UVA+e*UVA²)

Such equations provide good fits to validation data measured using two microbes (e.g., MS2 and T1UV) and can provide accurate pathogen inactivation and RED predictions.

Such equations can also be used to predict NDMA and AOP REDs by setting the DL to a value based on NDMA photolysis or the advanced oxidation of a target compound such as 1,4-dioxane. However, while the maximum RED delivered by a UV reactor is limited by the average UV dose of the UV dose distribution, the RED predicted by the combined variable equation cited above increases above the average UV dose of the UV dose distribution as DL increases, which is not physically possible. This can result in a significant over prediction of NDMA or UV AOP RED.

This issue can be addressed using UV dose algorithms that predict UV dose distributions. Such algorithms can be fitted to validation data and used to provide better predictions of NDMA and UV AOP REDs. This work compares the two approaches for analyzing validation data using a pilot flow through reactor used for UV research conducted for Cal Val.

Growing demand for drinking water—combined with climate driven supply variability—is accelerating the adoption of potable reuse and, with it, the expanded use of UV advanced oxidation processes (UV/AOP). California has taken a leading role in defining performance goals for indirect potable reuse treatment trains, requiring 12 log virus inactivation and 10 log inactivation of Cryptosporidium and Giardia, with UV/AOP systems allowed to claim up to 6 log inactivation credit for each pathogen. As a result, the Portland validation facility is increasingly conducting testing at the 6 log level. While validation approaches for achieving 6 log credit are now well established, demonstrating equivalent performance in the field remains challenging, particularly if validation does not extend to 6 log or the UV system installation piping is not compliant with UVDGM requirements and CFD cannot be validated per recommendations of WRF 4376.

Ongoing research through CalVal (WRF Project 5277) is developing technology specific guidance for potable reuse projects in California. A key focus is evaluating whether spot check bioassays—like those used by NWRI for non potable reuse—can feasibly show 6 log pathogen removal in full scale UV/AOP installations.

This presentation examines the limitations of using traditional surrogates such as MS2 bacteriophage in reverse osmosis (RO) permeate, where low ionic strength and other water quality characteristics complicate achieving and measuring high levels of inactivation. It will summarize recent field testing at three California UV/AOP facilities and review prior work on bioassay performance in RO permeate. As noted in the document, the goal is to “demonstrate the feasibility of conducting spot check bioassay to demonstrate 6 log pathogen removal of installed systems,” while addressing the practical challenges that arise in real world operating environments.

Mercury lamps have long been the standard light source for wafer edge exposure (WEE) in KrF lithography processes, but they present persistent challenges, including high thermal load, spectral instability, and frequent maintenance. In this study, we evaluate high-power, high-density UV-C LED arrays, based on advanced 3-PAD architecture, as a direct replacement for conventional 248 nm mercury lamps in a production WEE system.

A direct comparison was conducted under production-relevant conditions against both a mercury lamp baseline and a 265 nm LED alternative. Key performance metrics include dose-to-clear response, edge profile behavior (fringe angle), and operational characteristics. The 255 nm LED array demonstrated equivalent or improved resist activation in comparison with the mercury source, with enhanced response at low doses and no loss of process window. In addition, the LED source maintained superior edge profile stability across increasing dose levels, indicating improved control of lateral energy distribution.

Beyond lithographic performance, the UV LED arrays delivered substantial operational advantages. These include instant-on capability, reduced power consumption (70 W for LEDs vs. 500 W for mercury), and significantly lower thermal load. The narrow spectral bandwidth of the LED further contributes to improved process repeatability by minimizing out-of-band exposure.

These results confirm that high-density 255 nm UV LED arrays are a viable, production-ready alternative to mercury lamps for wafer edge exposure. The transition to UV LED sources enables improved process stability, reduced cost of ownership, and a clear pathway toward mercury-free semiconductor manufacturing.

RadBox is a novel sterilization system leveraging a dual-modality, solid-state platform that uses multi-spectrum Light Emitting Diodes (LEDs) for rapid instrument reprocessing. Unlike traditional steam autoclaves, RadBox operates at atmospheric pressure, eliminates water consumption, and reduces energy usage by over 95%. The system achieves terminal sterilization (6-log reduction) in approximately 6 minutes, offering a 3x increase in clinical productivity. In this presentation, we will present the results of microbial resistance and the latest design updates of RadBox. RadBox core design features a highly reflective polished aluminum chamber that recycles photons, ensuring uniform delivery of germicidal and thermal energy. The device utilizes a proximal architecture, positioning light sources ~10mm from instruments to maximize intensity. Tools are held in a custom, multi-spectrum transparent tray. Using the current design, we have performed microbial resistance studies and will present latest results on the specific Decimal Reduction times (D-values) across an extensive panel of representative organisms, including Bacillus pumilus, Geobacillus stearothermophilus, and Bacillus atrophaeus. By eliminating high-pressure saturated steam, RadBox preserves instrument integrity—extending tool life up to 4x—while removing the risk of burns or tray ejections. Having secured De Novo designation in July 2024, Lumaegis anticipates RadBox will be a sustainable, rapid alternative to century-old autoclave technology.

Water disinfection often encounters the hurdle of fouling which may inhibit reactor performance over time. Fouling phenomena may differ across different water matrices treated, and as such it is important to understand the role it pertains to in disinfection systems. Across various studies and literature there is ongoing discussion on how fouling occurs and how it differs between UVLED and low pressure UV (LPUV) reactors. One major theme is the narrative that UVLED reactors foul less than LPUV reactors because they run cooler due to lower heat radiation emission. We built an experimental system to test this narrative using UV reactors fitted with UVLEDs, LPUV lamps, heated sleeves and unheated sleeves, and measured fouling in a specialized optical reader as well as with bioassays. We will present our results from experiments using secondary treated wastewater.

This work presents the results of laboratory-scale Advanced Oxidation Process (AOP) tests applied to an industrial effluent generated by a manufacturing facility dedicated to technologies and equipment for life sciences applications in Puerto Rico, developed through a collaboration between Instapura and Nalco an Ecolab Company. The primary objective was to evaluate the efficiency of a combined UV/O₃/H₂O₂ system for the degradation of refractory organic compounds present in the effluent, using ultraviolet radiation at 254 nm and vacuum ultraviolet (VUV) radiation at 185 nm. During the first experimental phase, only UV irradiation at 254 nm was evaluated. In a second stage, ozone generation, 185 nm VUV radiation, and hydrogen peroxide dosing were integrated in order to promote intensive hydroxyl radical (•OH) formation. The tests were performed under recirculation conditions using a 10 L sample volume, a flow rate of 750 mL/min, and contact times of up to 50 minutes. The evaluated operating conditions included ozone concentrations of approximately 25 mg/L, H₂O₂ dosing at 25 mg/L, and cumulative VUV doses close to 2200 mJ/cm².

The results demonstrated that the combined UV185/O₃/H₂O₂ configuration significantly enhanced the oxidation of dissolved organic matter compared to conventional UV irradiation alone. The operating condition identified as 2C achieved the best overall performance, reaching nearly 96% reduction in Total Organic Carbon (TOC), along with an approximate 29% reduction in Chemical Oxygen Demand (COD). These findings suggest that the integration of VUV technologies with chemical oxidants can induce highly efficient partial mineralization processes for the treatment of complex pharmaceutical effluents.

Finally, the study established preliminary design criteria for a continuous industrial-scale treatment system with a capacity between 7.5 and 15 gpm, integrating ozone generation, VUV reactors, H₂O₂ dosing, and activated carbon polishing stages.

The CalVal initiative, led by the National Water Research Institute with support from industry stakeholders, is developing guidance for the implementation of membrane filtration, reverse osmosis, and ultraviolet advanced oxidation (UV AOP). The first phase (Water Research Foundation Project No. 5277) reviewed how treatment barrier validation for indirect potable reuse (IPR) has been implemented across California. A key finding was that while the science behind UV AOP is strong, approaches to validation, operation, and reporting vary considerably across projects.

To address this inconsistency, CalVal conducted a focused workshop series engaging UV AOP technical experts, utility advisors, and regulatory staff. Two rounds of workshops gave each group multiple opportunities to share insights and provide feedback on the proposed UV AOP guidance framework. Outcomes from these discussions will be presented in this talk.

In addition to the workshops, research was identified to strengthen the industry's fundamental understanding of UV AOP systems. Led by Carollo Engineers and Trussell Technologies, the work is currently underway at Orange County Water District, Monterey One Water, and the City of San Diego's North City Pure Water Demonstration Facility. The research addresses five topics:

1. Spot-check bioassays: a potential tool for demonstrating 6-log inactivation with UVDGM-validated reactors, particularly for installations with non-standard inlet piping or incomplete validation.
2. NDMA UV dose-response: examining how water quality and test methods affect results to improve Reduction Equivalent Dose (RED) algorithm accuracy for full-scale design.
3. UV AOP breakpoint chemistry: evaluating published models to guide UV/chlorine AOP system design, instrumentation, and operation.
4. Scavenging demand testing: assessing how measured background scavenging demand can inform design, operation, and regulatory enforcement.
5. 1,4-Dioxane AOP modeling: calibrating a non-proprietary tool by comparing measured and predicted log removal values to better define UV AOP challenge test conditions.

UVLEDs are more expensive in both capital and operating costs than conventional low pressure UV (LPUV) lamps, creating a large economical barrier to adoption in water treatment applications. However, the calculus changes if UVLEDs produce more inactivation than LPUV lamps, as recently reported for 280nm UVLEDs on coliform bacteria in wastewater. Given that action spectra indicate that UV at 280 nm should be less effective than UV at 254nm, we made comparisons on secondary wastewater collected from two local wastewater treatment plants, using collimated beams fitted with LPUV and 280nm UVLED light sources to produce dose-response curves. We repeated this on two occasions for both waters, and found LPUV to inactivate more coliforms than 280nm UV. In case there was something very beneficial to 280nm UVLEDs in certain waters, we ran comparisons from samples collected from the same waste water treatment plants in the other studies, on two occasions, and again found LPUV to be more effective than 280nm UV on coliforms. The next year we ran additional comparisons on five occasions from both of our local waste water plants and repeatedly found LPUV to be more effective than 280 nm UV on coliforms. This presentation will discuss the results and other investigations to examine sources of error.

UV/AOP reactors are commonly monitored by a single optical sensor reporting transmitted intensity. This signal is averaged into a slowly-varying mean used to verify dose delivery. However, the underlying signal carries short-timescale fluctuations about reactor mixing, fouling onset, and chemistry that are discounted when only the mean is reported. The consequence is that the true variability of dose delivery is unknown: operators cannot tell whether observed deviations from the mean reflect normal operation or concerning shifts in reactor state.

We address this gap on a bench-scale UV-LED reactor (ASG5910 cylindrical vessel, 140 mL, 265 nm UV-LED at 0.54 mW/cm^2, 2 mL/min flow) instrumented with a visible-light LED and photodiode pair across the 63 mm reactor diameter, sampled at 5 s intervals. The signal yielded a time delay of 70 samples (350 s) and an embedding dimension of 4, determined by average mutual information and false nearest neighbors (FNN) analysis. Windowed maximum Lyapunov exponent estimates centered near zero, consistent with a low-variance baseline. We extend this analysis to UV/H2O2 operation under controlled non-stationarity, applying a surrogate-data test to confirm that detected structure reflects real reactor dynamics.

Initial results show that the FNN segment diagnostic distinguishes a controlled pump-stop disturbance from stable baseline and post-recovery conditions, identifying it as an abrupt regime change. The planned extension tests whether nonlinear features respond to operationally relevant state changes that scalar transmittance does not resolve, and quantifies the threshold at which they add diagnostic information beyond mean-level monitoring.

If successful, time-series analysis recovers diagnostic information from the photodiode signal that mean-level monitoring discounts, providing a low-cost continuous indicator that flags reactor-state changes earlier than scalar metrics. For regulators, this offers a real-time signal of monitoring reliability and further insights into uncertainty around UV dose consistency.

The development of biotechnological treatments for agricultural health is crucial to minimize reliance on conventional chemical treatments, whose residual effects represent a latent risk for human health and ecological balance. For these biotechnological treatments to be effective, it is necessary to optimize the growth of the microorganisms used as control agents. Among them, the bacterium Bacillus subtilis is of vital importance as a sustainable alternative to conventional chemical fungicides, specifically for the control of high-impact phytopathogens such as Sclerotium cepivorum Berk., which represents one of the main threats in garlic crops.

However, maintaining optimal conditions of asepsis in industrial production tanks continues to be a critical challenge due to the risk of competitor contamination. This work presents the design, structural modeling, and experimental validation of a specialized UV-C irradiation device equipped with a dual low-pressure mercury lamp system operating at 254 nm. This system was developed specifically for the microbiological decontamination of the internal surfaces of industrial tanks destined for the cultivation of B. subtilis.

System characterization consisted of measuring the incident irradiance at different geometric points inside the tank using an ILT950 spectroradiometer, yielding an average irradiance distribution comparable to the standard Petri factor. With the objective of determining the efficiency of the germicidal effect, three distinct doses of UV-C radiation were evaluated in an experiment. The results demonstrated that the system is capable of reaching a microbiological inactivation superior to 2 Log, validating the technical viability of the device to assure the required conditions of asepsis and scale-up safety.

Proponents of mercury-free UVLED technology have been vilifying conventional low pressure mercury lamps (LPUV) for water disinfection devices, pointing out the Minamata Convention that aims to protect human health and the environment from anthropogenic emissions and releases of mercury and mercury compounds. Ironically, the massive difference in energy efficiency results in UVLEDs consuming 4.5-fold more electrical energy than LPUV lamps to produce an equivalent amount of UVC light (albeit at higher UV wavelengths of lower germicidal efficiency for UVLEDs). The mercury emissions from electricity production, mainly from the fraction of supply generated by coal fired power plants, would thus elevate the amount of mercury released to the environment by 17- to 60-fold for UVLEDs compared to LPUV, depending upon the region of energy production. Meanwhile, 2 columns over and 4 rows up in the periodic table from mercury is the element carbon, a different environmental poison. Analagous to the Minimata Convention for mercury control, the Paris Agreement is an international treaty that aims to limit global temperature increases in part by reducing greenhouse gas emissions. Replacing LPUV lamps with UVLEDs, due to the electrical efficiency penalty, would result in 4.5-fold energy increases, 60-fold mercury emission increases, and 4.5-fold carbon emission increases. This presentation will discuss all of these important pollution aspects for UV disinfection systems.

CalVal is an effort to develop treatment technology-specific guidance documents for potable reuse projects in California. Through WRF Project 5277, the CalVal team identified five knowledge gaps requiring research to support guidance development for Ultraviolet Advanced Oxidation Process (UV/AOP) systems. One research area focuses on the UV dose-response of NDMA.

With indirect potable reuse (IPR) treatment trains, UV AOP is often located after reverse osmosis (RO) and used for 6 log pathogen reduction, NDMA photolysis, and 1,4-dioxane oxidation. Past studies indicate that the UV dose per log reduction (DL) of NDMA with RO permeates can range from 600 to 1,200 mJ/cm2. While the literature reports that the UV dose required for NDMA photolysis varies with pH and oxygen, the range observed with RO permeates has not been explained. The UV dose per log reduction of NDMA impacts UV system sizing and operation with some UV systems sized and operated based on conservative UV dose values for NDMA photolysis even though demo or startup testing may indicate a lower value. Hence, research was recommended to measure NDMA UV dose-response and understand how water quality and/or measurement methods impact that UV dose response.

This presentation will summarize NDMA UV dose-response measured at three IPR facilities using a high-power collimated beam device and a validated flow-through UV reactor with RO permeate representing design and ambient conditions. Preliminary results show NDMA DLs ranging from ~690 to 800 mJ/cm2 per log without hydrogen peroxide as an oxidant and ~620 to 760 mJ/cm2 with hydrogen peroxide. Differences were observed with the collimated beam and flow through reactor that were addressed in part by modifying the UV dose calculations with both devices. For example, UV dose equations based on predicted UV dose distributions provide notably better predictions of NDMA REDs than equations typically developed through UV validation.

Today, advanced oxidation processes (AOPs) play a critical role in various applications, including the removal of NDMA and 1,4-dioxane for potable reuse, taste and odor control during drinking water production from surface water, or the removal of industrial chemicals from groundwater. However, selecting the most suitable AOP—whether UV-based or non-UV-based—remains a challenge for water authorities due to the wide range of available technologies and influencing factors.

Drawing on laboratory, pilot-scale, and full-scale data, this work aims to provide practical guidance for AOP selection based on e.g. water matrix characteristics, treatment objectives, flow conditions, spatial constraints, retrofit potential, and lamp technology. While UV-based AOPs (UV/chlorine or UV/H2O2) are typically favored for potable reuse applications, ozonation and ozone-based AOPs tend to be more efficient in impaired water sources such as tertiary filtered effluent. This study focuses on AOP selection for applications in groundwater and surface waters. We apply chemical reaction kinetics modeling to determine optimum operational parameters, capital and operational costs for UV/H2O2 and O3/H2O2 applications and perform sensitivity analyses to estimate effect of relevant parameters on process selection.

Furthermore, the study will expand to alternative treatment solutions including emerging lamp technologies and photolytic ozonation. Lab-scale experiments in tap water indicated that photolytic ozonation can significantly reduce bromate formation in bromide containing waters—e.g. in one experiment, from 5.4 µg/L to below quantifiable levels at UV doses under 50 mJ/cm²—compared to ozonation alone. While the application of UV-LEDs provides a promising approach for photolytic ozonation, efficiency of UV/H₂O₂ declines when using currently available UV-LEDs due to the low molar absorption coefficient of hydrogen peroxide at higher wavelengths.

The development of biotechnological treatments for agricultural health is crucial to minimize dependence on conventional chemical treatments, whose residual effects represent a latent risk for human health and the ecological balance. For these biotechnological treatments to be effective, it is necessary to optimize the growth of the microorganisms used as control agents. Among them, the bacterium Bacillus subtilis is of vital importance as a sustainable alternative to conventional chemical fungicides, specifically for the control of high-impact phytopathogens such as Sclerotium cepivorum Berk., which represents one of the main threats in garlic crops. However, maintaining optimal conditions of asepsis in industrial production tanks continues to be a critical challenge. This work presents the design and validation of a UV-C irradiation device of a double mercury lamp, developed specifically for the microbiological decontamination of industrial tanks destined for the cultivation of B. subtilis. The characterization of the system allowed to evaluate the distribution of the irradiance on the inner layer of the container. With the objective of determining the efficiency of the germicidal effect, three doses of UV-C radiation were evaluated in an experimental manner. The results demonstrated that the system is capable of reaching a microbiological inactivation superior to 2 Log, validating the viability of the device to assure the required conditions of asepsis.

In food processing facilities, airborne viral aerosols can serve as vectors for microbial cross-contamination, settling on food contact surfaces, equipment, and products leading to spoilage and contamination of food. This study evaluates the effectiveness of UV-C treatment as a non-chemical approach for inactivating viral aerosols in air. Model microorganisms included bacteriophages (MS2, Qβ and T1UV) at a concentration of 1010 or 1011 PFU·mL⁻¹ as viral surrogates. Aerosols were generated using a 4-jet Blaustein Atomizing Module atomizer. The bacteriophage aerosols were exposed to UV-C using a 4-lamp orientation with low-pressure mercury lamps mounted outside of quartz sleeves. Aerosols passed through the sleeve, with UV dose controlled by airflow-modulated residence time. The bacteriophages were collected via impinger in CM buffer and enumerated by spot plate overlay agar assay using their respective Escherichia coli hosts. Following aerosolization, the recovered concentration of the different bacteriophages was MS2 6.72 ± 0.23 log PFU·mL⁻¹, 5.59 ± 0.35 log PFU·mL⁻¹ and Qβ 7.27 log PFU·mL⁻¹. UV-C treatment achieved inactivation of aerosols at varying levels and showed a maximum log reduction of 4.01 ± 0.44 log PFU·mL⁻¹ (delivered fluence 83.93 mJ/cm²) for MS2, 5.04 ± 0.35 log PFU·mL⁻¹ (delivered fluence 25.21 mJ/cm²) for T1UV and Qβ 4.37 log PFU·mL⁻¹ (45.9 mJ/cm²). These outcomes demonstrate the system's robust capacity to eliminate airborne pathogens. This study addresses critical needs in food safety by validating scalable UV-C air disinfection to reduce bacterial and viral aerosols in processing environments, preventing cross-contamination and minimizing risks of foodborne outbreaks.

Human rotavirus is a leading cause of severe gastroenteritis in young children. As a waterborne virus of public health concern, rotavirus serves as the basis for National Sanitation Foundation (NSF) certifications of UV-LED reactors, while Q-beta bacteriophage is recommended as the test surrogate due to similar UV inactivation kinetics at 254nm. Although action spectra for Q-beta have been published, UV inactivation kinetics for rotavirus at LED wavelengths have not.

We measured action spectra for two strains of rotavirus: human Wa and simian SA11, the former the most relevant for humans, the latter the most used due to its ability to titre to higher concentrations. We generated UV dose-response curves from 200 – 282 nm using collimated beams equipped with low-pressure (254nm) lamps, polychromatic medium-pressure lamps together with band-pass filters, and various UV-LED arrays at different wavelengths. Infectious rotavirus was quantified using a 50% tissue culture infectious dose (TCID50) assay in MA-104 cells. At 254 nm, the UV sensitivity of SA11 was 8.4 mJ/cm²/log, while that of Wa was 11.8 mJ/cm²/log, which were both aligned with previous studies. However, the normalized germicidal factor for Q-beta is higher than both rotavirus strains at LED wavelengths (265 - 282 nm), and lower for low UVC wavelengths (220 - 240 nm). We used this data together with actual bioassay data from residential UV-LED reactors to determine that Q-beta would produce conservative results in NSF testing.

The application of ultraviolet germicidal irradiation (UVGI) within an HVAC system is an effective strategy for mitigating biofilm on cooling coils, filters, drain pans, and duct surfaces. A UVGI system can improve the heat transfer efficiency of a cooling coil, decrease fan energy, and enhance indoor environmental quality. However, the performance of a UVGI system in real world conditions is almost always assumed to produce outcomes based on testing in controlled spaces. Actual HVAC conditions can be very different from those in controlled environments.

This presentation examines a structured approach to verify UVGI performance using the deployment of GUV sensors operating in real-time or scheduled monitoring modes. The presentation will focus on using UV-C irradiance data, plus data from other measured HVAC environmental parameters to verify that an installed UVGI system can realistically achieve specified outcomes.

Key components of the proposed methodology involve calibrated sensors (fixed-position and portable) and an automated analytics solution that uses sensor data to identify equipment performance issues, optimize energy use, improve equipment efficiency and increase operational cost savings.

Special emphasis will be given to distinguishing between lamp operation and required disinfection efficacy. While UV lamps may appear energized, only direct irradiance and accumulated dose measurements confirm that sufficient energy is reaching targeted surfaces.

Attendees will gain practical guidance on sensor placement, measurement intervals, integration with building automation systems, and analytics strategies for quantifying the operational effectiveness of UVGI systems to prevent biofilm growth and improve HVAC equipment efficiency.

Micropollutants are important issues in water treatment because some of them pose health risks to humans and the environment. Ultraviolet-based advanced oxidation processes (AOPs) have emerged to be effective in micropollutant control, which rely on UV photons to split oxidants into radical species that can destroy micropollutants. However, the photon utilization efficiency in most UV-based advanced oxidation processes (AOPs) is usually low, and the fundamental reason is that the UV photons travel too short a path length in the water before they hit and be absorbed by the reactor walls and other accessories (i.e., be wasted). To address this issue, this study integrated microbubbles into the system to “trap” photons in the water. The surfaces of numerous microbubbles scatter or reflect photons, changing the photons’ pathways from straight to torturous. This will keep the photons in the water long enough to interact with oxidants and less likely to reach the walls, resulting in performance enhancement.

This study is designed to compare two widely used AOPs, UV/H2O2 and UV/chlorine, in micropollutant control at bench scale, with and without microbubbles (10-100 µm). Nitrobenzene, benzoic acid, and caffeine are selected as representative micropollutants. The impact of microbubbles on AOP performance is evaluated under different conditions by monitoring the kinetics of oxidant (i.e., H2O2 or chlorine) and micropollutant decay. The different test conditions are achieved by varying oxidant doses, reactor sizes (short vs long path lengths), water matrices (low transmittance vs high transmittance), and lamp types (medium pressure, low pressure). For each test condition, the optimal microbubble concentration for enhancing photon utilization will be identified experimentally.

Our preliminary data has shown that the photon utilization at the optimal bubble concentration is significantly higher than that without microbubbles, as reflected by accelerated oxidant and micropollutant decay—under certain conditions, the decay rates were doubled with the addition of microbubbles. It is expected that complete results will be presented, along with discussion on implications for full-scale and point-of-use applications.

Upper-room germicidal ultraviolet (UR-GUV) systems have a strong evidence base for reducing airborne pathogen transmission in shared indoor spaces, yet deployment remains limited relative to their technical potential and cost-effectiveness. UR-GUV is often perceived as a niche option, overshadowed by ventilation upgrades and portable air cleaners in offices, schools, healthcare, and other public and commercial buildings. This presentation examines the main barriers that inhibit wider adoption and proposes practical solutions and strategies to overcome them.

Barriers are grouped into three categories: (1) awareness and perception, (2) technical and design complexity, and (3) regulatory and liability concerns. Awareness barriers include limited familiarity among facility managers, infection preventionists, engineers, and owners with contemporary upper-room designs, safety data, and performance benchmarks. Technical barriers include constraints related to ceiling height, room geometry, air mixing, and uncertainty about integration with existing HVAC systems, particularly in older buildings. Regulatory and liability concerns encompass confusion over applicable standards and guidelines and perceived risk of UV overexposure.

The presentation will outline a practical framework applicable to all indoor spaces, including screening criteria for candidate rooms, simplified sizing and performance estimation tools, and design strategies to enhance air mixing while maintaining safety. It will also highlight emerging standards and guidelines, example implementation pathways, and opportunities for manufacturers, designers, regulators, and building owners to streamline adoption and communicate performance in decision-relevant te

Wastewater matrices are complex and often limit UV disinfection due to wavelength dependent interactions via absorbing and blocking constituents. UV LEDs have been previously tested predominantly at 280 nm however a key benefit to UV LEDs is the tunability of wavelengths. As a result, exploration of treatment efficacy using alternative UV LED wavelengths in various water matrices is largely left unexplored. This work was conducted as part of an interlab study between Dalhousie and the University of Colorado Boulder to avoid variability in reports of a single laboratory. Five different UV sources were used and investigated which included three UV LED sources at wavelengths of 255, 265 and 280 nm as well as two mercury-based UV sources of a low (254 nm) and medium-pressure polychromatic UV lamp for the inactivation of three target organisms. The target organisms include a bacterial (E. coli K12) and two viral challenge organisms (MS2 and T1 Bacteriophage) which were assessed at a range of UV doses to produce UV dose response curves. Each UV source and target organism combination were tested on five different water matrices sampled from across North America which compromised a mix of drinking, ground and wastewater matrices from both small and large capacity water treatment plants. The average performance between laboratory findings indicated 265 nm as the most germicidal UV C source across the tested water matrices. Several of the inactivation kinetics curves for E. coli K12 were comparable between all LED sources and low-pressure disinfection but differed when considering each of the phage inactivation curves. The source of the water matrix did not appear to govern which UV source was most germicidal, but the results point to the need for a better understanding of spectral sensitivity and secondary mechanisms when comparing different sources of UV light. These results provide utilities a framework and dataset to understand how different wavelengths of UV light compare with conventional sources and provide a robust understanding of the effects of water matrix characteristics and importance of UV source selection for target organisms. Furthermore, genomic modeling techniques have been applied to this dataset to understand the genetic vulnerabilities to varying wavelengths of UV light for both bacterial and phage challenge microbes. This approach investigated the possibility of using genetic quantification as a predictive tool for UV efficacy by coupling genetic sequencing, water quality data, and log reduction values into the model dataset.

Since their initial development in the late 20th century, UV C LEDs have proven effective across a range of use cases including air, surface, and water disinfection. Technological advances in wall plug efficiency and power output have resulted in the recent application of UV C LED reactors at scales relevant to municipal disinfection. This trajectory of technological readiness has positioned UV C LEDs as transformative tools that are on course to disrupt conventional water treatment. Here, we discuss recent advances and alternative use cases for UV C LEDs in the water sector. Highlights include application of the first full-scale UV C LED reactor for municipal wastewater disinfection, UV C LED-driven biochemical oxygen demand reduction in municipal wastewater, and use of far-UV C LEDs for destruction of organic contaminants. Several design considerations have been identified through this work to supplement best practices for bench-scale UV experiments.

We also illustrate how the tunable nature of UV LED systems can reduce energy consumption and by-product formation while improving process efficiency – in the case of aqueous 17B-estradiol, we observed a ~10-fold increase in degradation rate (4.04 vs. 0.215 x 10-3 cm2 mJ-1) and ~four-fold reduction of energy requirements (2.66 vs. 11.34 kWh m-3 order-1) when using UV C LEDs as compared to conventional UV systems. Finally, we evaluate the future potential of these devices for the water industry and examine how projected technology advances may affect the next generation of water treatment technologies. UV LEDs offer flexibility in design not currently achievable with traditional systems, and their diversification of light output will be an important feature of future reactor design as more wavelengths of LEDs become commercially viable.

Ultraviolet light-emitting diodes (UV-LEDs) are increasingly used in bench-scale water treatment studies for microbial inactivation and degradation of organic contaminants. Existing bench-scale fluence determination procedures were primarily developed for quasi-collimated mercury UV systems and may not fully represent the unique conditions encountered during UV-LED experiments, particularly their significant beam divergence under near-field exposure conditions. Furthermore, the impact of sample loss during extended irradiation experiments is often overlooked, despite its potential impact on delivered fluence, measured concentrations, and calculated degradation kinetics.

This study presents a revised methodology for fluence determination and sample-loss correction in long-exposure bench-scale UV-LED experiments. The standard divergence factor formula used to account for irradiance loss from beam divergence through sample depth was also updated to better represent non-collimated beam behaviour under near-field bench-scale UV-LED experimental set-ups. The method was validated using a low radiant power bench-scale UV-LED system operating at 235 nm and applied to the degradation of a stable probe compound (caffeine). Results obtained using the revised approach were compared with conventional procedures commonly applied in bench-scale UV studies.

Under the near-field conditions investigated for this study (30 mm displacement between UV-LED source and sample surface), the standard divergence factor formula was found to overestimate beam divergence by 25%. Furthermore, accounting for sample loss resulted in up to a 9% difference in calculated delivered fluence (3629 mJ cm-2 compared to 3307 mJ cm-2) and up to a 98.7% difference in fluence-based degradation rate constants (5.61×10-5 cm2 mJ-1 compared to 1.65×10-4 cm2 mJ-1) during long exposure experiments. These findings demonstrate that beam geometry and sample loss can substantially affect interpretation of low-power bench-scale UV-LED photodegradation experiments, especially during longer-exposure experiments.

Hydroxyl radical scavenging capacity (HRSC) is a useful parameter in advanced oxidation processes (AOPs) to quantify the consumption rate of hydroxyl radicals (·OH) by the various species in the water matrices. Its measurement usually relies on monitoring the decay of a probe compound such as methylene blue (MB) in the water samples under a constant ·OH flux, followed by an algorithm to convert the probe decay rate into HRSC. Using MB as the probe compound significantly simplifies the analytical procedure, requiring primarily spectrometers rather than more complex chromatography-based analytical instruments. However, no study has been conducted to test MB’s suitability as a probe over a broad range of pH (e.g., 4-10), in spite of pH’s potential impact on its molecular structure and UV-vis spectrum. Therefore, the first objective of this study is to address this knowledge gap by comparing the color decay rates of MB in standard HRSC solutions (e.g., synthetic solutions containing isopropyl alcohol at known concentrations) under different pH conditions. The result will reveal whether the response of MB toward ·OH oxidation is pH dependent.

Meanwhile, in real water samples such as those acquired from drinking water treatment plants or wastewater treatment plants, changes in pH affect the speciation of common inorganic scavengers (e.g., bicarbonate and carbonate) as well as the protonated, neutral, and deprotonated forms of organic functional groups, thereby influencing the HRSC of water samples. Therefore, the second objective of this study is to investigate how the HRSC of water samples changes with pH, thereby deepening our understanding of the pH dependence of AOP performance.

Keywords: Advanced Oxidation Process, Ultraviolet, Hydroxyl Radical, pH Effect, Scavenging Capacity Corresponding Author: Chengjin Wang, Department of Civil Engineering, University of Manitoba.

Email: chengjin.wang@umanitoba.ca, Phone: 204-474-8381

UVC LEDs are gaining rapidly increasing importance across decentralized disinfection and sterilization applications. Their ability to generate light instantly, operate in compact and toxin-free systems, and deliver low power consumption makes them strong contenders to replace conventional mercury-based UV lamps. While the overall wall-plug efficiency (WPE) of UVC LEDs is still generally lower than that of established lamp technologies, the effective performance strongly depends on the application and, in particular, on how efficiently the generated light is extracted and utilized. Leveraging this principle, L has introduced and commercialized optimized reflector-based package architectures that significantly enhance useable optical power.

Building on this established reflector platform, we present a novel multi-chip UVC LED package that achieves up to 50% higher optical output at comparable electrical input power. In contrast to the prevailing trend toward larger UVC dies to boost absolute power, our approach utilizes smaller LEDs that inherently exhibit superior internal quantum efficiencies. Although each die has a lower individual optical output and a higher ratio of sidewall to top emission—typically a disadvantage in standard packages—we capitalize on this characteristic. By integrating micro-scale reflectors, we effectively recover side emission and redirect it to the optical aperture, yielding a measurable increase in overall package efficiency.

We demonstrate a 3535-format package incorporating four small emitters, achieving optical output levels exceeding 150 mW and WPEs above 7% at 275 nm. Finally, we provide an outlook on scaling this concept to larger footprints with high power densities and its applicability to additional wavelength ranges.

Nitrate photolysis at short wavelengths (200 – 240 nm) can produce nitrite, which is a strong hydroxyl radical scavenger and has a low drinking water limit (1 mg/N/L) in many jurisdictions. This implies that medium pressure UV (MPUV) for advanced oxidation (AO) could be at a disadvantage due to the risk of nitrite formation. However, most natural water has a strong inherent absorption from 200 – 240 nm, potentially limiting nitrite formation potential. This subject has not been quantitatively reported in the literature. It is hypothesized that, in a full-scale MPUV AO reactor, nitrite formation will be limited to a small region near the lamp sleeves, leading to very little overall formation in the bulk flow. A mechanistic chemical analysis was first conducted in MATLAB under collimated-beam conditions to examine nitrite formation in a water depth-dependent basis, demonstrating minimal nitrite formation beyond the first 1 cm of fluid layer. A full-scale MPUV reactor was then modelled using computational fluid dynamics (CFD), with different water quality matrices modelled (e.g., RO permeate and wastewater) to assess the extent, spatial distribution, and overall significance of nitrite formation (work being completed in May 2026 and results to be reported). Beyond exploring the specific question of nitrite formation in MPUV reactors, this work demonstrates a new working framework for resolving wavelength-dependent reaction kinetics within CFD that can be extended to other UV AOP applications involving other chemical transformation pathways and byproducts.

Ultraviolet (UV) light is an alternative to chlorine disinfection for water treatment due to its effective disinfection mechanism which is chemical and byproduct free. Essential to evaluating UV effectiveness is development of UV dose-response relationships that will inform the UV dose to achieve a target log reduction. Interestingly, UV disinfection inactivation curves are commonly limited by a phenomenon called ‘tailing’. Tailing is the physical plateau in disinfection kinetics where, as UV doses increase, inactivation rates decrease, eventually reaching a plateau region where there is no additional inactivation as UV dose increases. This phenomenon is primarily attributed to microbial aggregation, where clusters of bacteria shield internal cells from UV penetration, preventing complete inactivation of the population of cells. Other research suggests that these microbial clumps form as a mechanistic stress response from UV exposure, providing protection for other nearby cells. This research investigates non-chemical approaches which may reveal the mechanism behind the UV disinfection tailing phase, to better understand dose-response relationships and suggest alternatives for bench UV inactivation studies.

We investigate various sonication scenarios coupled with detailed microscopy to isolate and understand the impact of aggregation on tailing. We also examine methodological practices such as starting concentration and sample volumes to understand biases that may be introduced that impact bacteria clumping. We examined 3 different bacteria including Methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and E. coli. Findings indicate sonication at a frequency of 40 MHz increases microbial log reduction values by over 1.5 logs, corresponding to a decrease in bacterial concentration of more than 2 log CFU/mL. Microscopy and flow cytometry suggest that more clumps are formed after the presence of UV but less clumps after the addition of sonication. These results indicate that tailing occurs due to microbial stress responses due to UV exposure.

Ultraviolet-C (UV-C) light at 254 nm offers a promising non-chemical approach to eliminate airborne microbial contamination in food processing facilities. This study evaluated UV-C disinfection effectiveness against aerosolized bacterial pathogens and used computational fluid dynamics (CFD) modeling to map UV dose distribution in a treatment reactor.

Researchers used a laboratory-scale continuous-flow reactor (1.2 m long, 0.07 m diameter) equipped with four UV-C lamps to treat aerosolized Salmonella typhimurium at three flow rates (2.5, 5.0, and 7.0 m/s), producing UV doses between 25 and 105 mJ·cm⁻². Bacterial samples were analyzed at 0-, 24-, and 48-hours post-treatment.

The results showed complete inactivation (>5 log reduction) of all pathogens at medium and high UV doses. However, CFD simulations revealed uneven UV dose distribution across the reactor. Analysis indicated that Salmonella typhimurium in aerosol form required an average UV dose of 9.48 mJ/cm², substantially higher than the 3.8 mJ/cm² needed for bacteria in aqueous solutions. This difference reflects the enhanced UV resistance of aerosolized bacteria, attributed to the single-pass flow conditions and non-uniform dose distribution in the experimental setup.

The researchers implemented error-correction procedures to ensure accurate kinetic measurements despite systematic measurement variations.

This research establishes UV inactivation rates for aerosolized bacteria and provides design recommendations for UVGI systems in air disinfection applications. By combining experimental data with CFD modeling, the study enables optimized UVGI system design, offering food processors an energy-efficient, chemical-free solution to reduce airborne contamination risks.

Ultraviolet light-emitting diode (UV-LED) systems have been identified as promising treatment methods in decentralized water systems due to their compact design, low energy requirements, durability, and compatibility with off-grid applications. This study evaluated ten UV-LED systems deployed in household and school mixed rainwater and grid harvesting systems over 2.5 years through longitudinal microbial and physicochemical monitoring, MS2 validation testing, cleaning experiments, and SEM–EDS fouling characterization.

Longitudinal monitoring demonstrated progressive deterioration in microbial reduction, with elevated heterotrophic plate count (HPC) concentrations (median up to 4150 CFU/mL) and recurrent total coliform breakthrough occurring as early as 100 days into operation. Newly installed UV-LED systems achieved approximately 2.42–2.57 log MS2 reduction, whereas harvested field-aged reactors declined to as low as 0.008–1.45 log reduction. While other water quality indicators were unable to diagnose performance of the UV-LED reactors, a simple, field HPC test (IDEXX Easy Disc) of the aged reactors was well correlated with lab-based MS2 validation tests performance (p = 0.039).

Cleaning experiments showed that deterioration was partially reversible but strongly dependent on fouling chemistry. Acetic acid cleaning restored MS2 reduction from 0.17 ± 0.09 log to 1.72 ± 0.09 log and increased UV transmittance of the quartz window at 282 nm from ~45% to ~75%, whereas hydraulic flushing and chlorine cleaning produced limited recovery. SEM–EDS analysis of the quartz revealed heterogeneous organic, mineral, salt-associated, and possibly corrosion-derived fouling. Cleaning significantly reduced Zn, Na, Cl, and Ca associated deposits, while Fe, Cr, Ni, and organic-rich residues remained affixed to the quartz. The results demonstrate that decentralized UV-LED systems can experience faster-than-expected deterioration characteristics under a variety of field conditions with different pre-treatment and source water characteristics. This research highlights the importance of a systems-design approach to pretreatment, maintenance, and fouling management for reliable long-term operation.

Upper-room GUV is more accepted in healthcare than many experts believe, but the current level of acceptance still falls far short of what it should be for a solution with such great potential.

This presentation will share some of healthcare success stories (domestic and international) and discuss what where the keys to the technology being implemented in an environment where it is not often promoted.

The presentation will also look at the difficulties experienced during these success stories and will discuss how adopting industry standards such as ASHRAE GPC37 might lead to a stronger and more unified application of GUV in healthcare.

The healthcare industry is tightly controlled and compliance with industry standards and guidance documents is critical. Vendors who supply these GUV solutions should be required to have their staff complete training on GPC37 or other thorough guidelines to show that their system designs, installation procedures and safety measurements are in compliance with these standards. The presenter will recommend that the industry adopt NALMCO GUV training (and other similar, rigorous and unbiased programs) to certify industry influencers, designers and technicians are competent and able to deliver compliant solutions.

Finally, the speaker will suggest that a parallel path for 222nm GUV should be followed to help protect it’s acceptance, adoption and proper application.

Mechanical filtration remains a widely adopted strategy for indoor air quality management; however, high-efficiency filtration systems are associated with increased energy demand, frequent maintenance interventions, and operational challenges related to handling and disposal of contaminated filters. The accumulation of biological material within filters may also present occupational exposure risks during replacement and cleaning procedures. Emerging germicidal ultraviolet (GUV) technologies offer a potential alternative or complementary approach, with claims of lower energy consumption, broader antimicrobial efficacy, and compatibility with lower-grade mechanical filtration systems while maintaining effective air disinfection performance.

This study evaluates the efficacy of a UV air disinfection device against a spectrum of airborne biological contaminants using the ASHRAE Standard 185.1 test methodology. Testing will be conducted against representative viral, bacterial, and fungal microorganisms, including Influenza A virus (H1N1), Staphylococcus epidermidis, and Aspergillus niger. The study aims to provide a comprehensive assessment of the device’s microbial reduction performance across multiple contaminant classes under controlled environmental conditions.

By applying a recognised consensus standard, this work seeks to generate robust validation data for emerging UV technologies and contribute to the standardisation and harmonisation of GUV performance evaluation. The findings will support improved comparisons among air-cleaning technologies and inform the development of energy-efficient, safe, and effective strategies for indoor environmental control in healthcare, commercial, and public settings.

Surface disinfection is critical in shared spaces, as surfaces may act as reservoirs for microbial contaminants and vectors for disease transmission. High-touch surfaces create persistent and variable transmission pathways in both commercial and communal settings. This study investigates the inactivation of surface-bound A. brasiliensis and B. subtilis across a variety of material types (Glass, Plexiglass, Stainless Steel, Epoxy paint), which are relevant to the disinfection of shared surfaces (manufacturing, shared public spaces, healthcare, industrial biology) using 280 nm UV-C irradiation and compared to in-solution disinfection kinetics. These pathogens have limited previously published 280 nm disinfection data, and no published findings on surface-bound inactivation. A. brasiliensis (in solution) demonstrated a 3-log reduction value (LRV) at a fluence of 120 mJ cm-2 (k = 0.0147 mJ cm-2) while a 3-LRV was attained on surfaces at fluences ranging from 150 to 200 mJ/cm2 with k-values ranging from 0.0093 mJ cm-2 (Epoxy A) to 0.0213 mJ cm-2 (Stainless Steel). B. subtilis demonstrated similar responses, with in-solution samples attaining a 3-LRV at a fluence of ≈12 mJcm-2 (k = 0.318 mJcm-2). In contrast, a 2-LRV was attained on surfaces at fluences ranging from 10 to 25 mJ cm-2 with k-values ranging from 0.178 mJ cm-2 (Epoxy A) to 0.216 mJ cm-2 (Stainless Steel).

This work fills several gaps in research on the use of 280 nm UV LEDs as a disinfection tool for pathogenic species, and it demonstrates that 280 nm UV LED disinfection can achieve outcomes comparable to conventional 254 nm irradiation. By addressing these research gaps, future work focusing on how challenging microbes behave when inoculated on surfaces, reflecting real-world exposure in practical settings, can be undertaken, highlighting novel use-cases for UV LEDs outside of the drinking and wastewater space.

Pittsburgh Water’s (PgH2O) Clearwell Replacement is the finale of its over $500 million Water Reliability Plan series of projects to bolster water system reliability to over 520,000 residents for the next 100 years. PgH2O serves its residents from a 100 million gallons per day (MGD), 378.5 megaliters per day (ML/d), surface water treatment plant with an existing single-cell, 44 MG (166.5 ML) Clearwell constructed in 1906. It is being replaced due to no redundancy and age. The existing Clearwell is sandwiched between two gatehouses, a railroad, the Allegheny River, and several large underground utilities. NaOCl is used for primary and secondary disinfection to satisfy regulatory requirements for inactivation of pathogens. PgH2O’s long-term vision opened up opportunities for alternative disinfection resulting in a project that: 1.Replaces the existing clearwell with a three-cell 8.2 MG (32.9 ML) Clearwell.

2.Adds UV disinfection to satisfy Pennsylvania DEP’s requirements for 1-log inactivation of Giardia while the new Clearwell with NaOCl achieves 4-log inactivation of viruses. The new UV system is compact and uses 3 duty + 1 standby 48-inch (1.2-meter) diameter UV reactors that fit within the plant’s hydraulic profile. This disinfection change leverages the effectiveness of UV to inactivate Giardia and free chlorine to inactivate viruses with these benefits:<

1. Reduces NaOCl use and costs.
2. Reduces DBPs.
3. Reduces construction cost.
4. Works within site constraints.
5. Improves disinfection redundancy since the new Clearwell with free chlorine achieves 1-log inactivation of Giardia up to 45 MGD (170 ML/d) without UV.

Conventional UV reactor validations rely on microbial indicators with relatively low D10 values, limiting applicability for high-dose UV systems used in advanced water reuse. This study addresses this gap by developing a surrogate-based framework using high-D10 chemicals to extend performance evaluation beyond standard validation dose ranges.

Five chemical surrogates were selected to span a broad D10 range (~300–11,000 mJ/cm2/log), ensuring coverage of the high-dose regime. Selection criteria also included relevance to UV-absorbing compounds in treatment trains and practical considerations such as stability, solubility, and analytical feasibility, with emphasis on compounds undergoing direct UV photolysis.

High-dose validation was conducted on the TrojanUV AOP Demonstration Reactors across a wide matrix of flow rates (10–60 gpm), UV transmittance (79–99%), and power settings (30–100%). A computational model, integrating hydrodynamics, radiation transport, and kinetics, was used to design the test matrix and predict log removal values (LRVs). Collimated beam testing provided surrogate-specific dose–response relationships for conversion of reactor data to reduction equivalent doses (REDs). All experiments were performed in a controlled facility where treated water was captured and further processed prior to discharge, enabling surrogate use at bench- and real-scales.

A dataset comprising 79 reactor tests demonstrated strong agreement between measured and regression-modeled performance across the operating envelope, with slopes and R-squares of 0.9946 and 0.9956 for two-lamp reactor and 0.9899 and 0.9907 for four-lamp reactor, respectively. Overall, the results demonstrate that high-dose UV performance can be reliably characterized using chemical surrogates. Although it may not be possible to use this approach outside a controlled facility, we validated our core predictive model that could be applied to larger reactors.

UV/H₂O₂ treatment performance is governed by the steady-state •OH concentration, determined by •OH production and quenching by scavengers in the matrix. The IUVA Hydroxyl Radical Scavenging Task Force is developing a standard protocol to quantify this matrix scavenging, reported as the •OH scavenging term in the protocol. This parameter, defined as a pseudo-first-order rate constant for •OH quenching (s-1), is a key input for UV-advanced oxidation design and benchmarking. This presentation provides an update on the IUVA protocol work.

The scavenging term is typically measured from the decay rate of a probe compound that reacts selectively with •OH at a known rate constant. However, some probes may also react with non-•OH species, biasing the measurement. This study evaluates probe-related bias for para-chlorobenzoic acid (pCBA), nitrobenzene (NB), carbamazepine (CBZ), and methylene blue (MB), including their susceptibility to nitrate and carbonate interferences, to identify suitable probes for the IUVA protocol.

Experiments included two stages: synthetic-water challenge tests and validation in real water matrices. Synthetic water tests used elevated H₂O₂ to exaggerate potential interferences, with additional tests evaluating potential matrix-driven bias by adding nitrate or bicarbonate. Current results show that pCBA undergoes substantial non-•OH decay and may underestimate the scavenging term by >5% under challenging conditions. In contrast, NB, CBZ, and MB showed minimal bias and are recommended as more reliable alternatives. Validation tests are currently being conducted under typical UV/H₂O₂ conditions in real matrices (e.g., ultrapure water, surface water), with completion expected in the summer of 2026.

This presentation provides an overview of a Water Research Foundation program (WRF Project 5173) that investigated the feasibility of UV LEDs for municipal use using a One Water approach. UV LEDs have progressed substantially as a technology over the last decade and are now capable of being used in the design of full-scale UV reactors at flow relevant to municipalities. This project spanned from bench to full-scale and included the use of a pilot-scale 280nm UV LED system operating at a flow rate of 20 L min-1 which received raw lake water and a full-scale 280qnm UV LED system that treated secondary wastewater at a maximum flow rate of 2,725 m3 day-1. This work identified that 280nm LEDs disinfect both drinking water and wastewater at average UVTs as low as 55%. The full-scale wastewater installation reduced BOD5 of influent wastewater by 17% using only 280nm light as the driver for degradation. Outcomes from bench-scale work comparing different UV LED wavelengths suggests that tailoring of LED output to a target water matrix may be an important consideration as non-280nm LEDs become economically feasible for full-scale use. Additionally, the LEDs used in this work are from 2023 and there has been a notable increase in power and efficiency since the commissioning of these systems. Fouling of LED systems is another important consideration when understanding novel reactor design - it was identified that the composition of inorganics within a water matrix (such as iron or manganese) have a significant influence on fouling of quartz surfaces. This fouling differs from conventional UV systems as the observed inorganic deposition could be easily wiped away rather than requiring scale removal techniques. Overall, this work identified the range of water matrix conditions where 280nm UV LEDs can perform comparably to conventional UV systems and signal that LED systems are a viable treatment technology that water providers should consider.

This presentation will map the compliance landscape, summarise the state of readiness of the industry to accept UV-LED systems, and chart the path towards complete acceptance as LED systems supplant legacy mercury-based products.

The UV water disinfection market is not monolithic with regional and technological variation in standards and regulations. As such there is no consensus on the best approach to validate performance of UV LED systems. Advances have been made in recent years to build the framework supporting LED system adoption and performance validation; whilst many issues have been resolved, there remain several legitimate questions, particularly at the complex scale of high-flow system validation and maintenance. A non-exhaustive list of these questions could be:

• Action spectra correction for polychromatic sources,
• LED failure and fault tolerance of the system,
• Sensor type, location, and representativeness,
• UVT monitoring,
• Lamp replacement, upgrade, and comparability.

By examining the range of approaches either in place or pending finalisation we shall assess the state of readiness, summarise the points already resolved, and collate the outstanding questions to focus attention where it is needed.

Primary disinfection using ultraviolet (UV) light is well-established across scales, from municipal supplies to cistern-supplied homes. However, current practices emphasize the necessity of chemical residuals (e.g., chlorine) when water is not immediately consumed. The use of chlorine introduces significant challenges, including carcinogenic byproduct formation, intensive monitoring requirements, and rapid residual decay. These operational complexities are particularly acute in small, stored water systems, such as those in cistern-dependent Indigenous communities, where maintaining chemical residuals is often impractical and poses elevated health risks.

There is a clear need for chemical-free alternatives to maintain water safety after primary treatment. Periodic application of UV via low-cost, monochromatic UV-LED devices presents an opportunity for distributed disinfection schemes. However, critical knowledge gaps remain regarding application frequency, microbial behavior at low cell counts, and the potential for UV-resistance. This presentation outlines results from a collaborative study involving UV-LED manufacturers, Indigenous water system consultants, and academia to mitigate risks in cistern-based systems. Findings demonstrate that repeated application of low-fluence UV-C (~5 mJ/cm²) effectively controls planktonic cell populations. Furthermore, this study utilizes flow cytometry to quantify system performance at low background organism counts and assesses the potential for induced UV-resistance within the microbial community.

By providing high-resolution data on microbial response to periodic, low-dose UV exposure, this work establishes a framework for evaluating when UV can safely replace or supplement traditional secondary disinfectants. These results help define the operational boundaries for distributed UV disinfection and provide the context necessary to implement UV-based solutions for ensuring water safety in vulnerable and decentralized infrastructure.

UV LEDs offer reactor design flexibility, and their tuneable UVC emission spectrum enables wavelength selection for specific microbial targets; however, this flexibility creates a large design space that requires numerical analysis to quantify how LED array geometry impacts fluence delivery for flow-through UV reactor chambers. This presentation demonstrates how flow distribution and UV LED placement interact to determine fluence development and dose-effectiveness in planar flow-through reactor geometries. An Eulerian framework—developed by coupling fluence rate fields from Ansys Speos with velocity fields from Ansys Fluent using R—was applied to examine ninety-six configurations across two domain aspect ratios, six velocity profiles, three UV LED source configurations, and four emission power levels. The ordering of velocity profiles for fluence uniformity was consistent across all experimental combinations. The parabolic velocity profile yielded the greatest non-uniformity, while a split velocity profile (low and high flow coupled with high irradiance) achieved the highest reduction equivalent fluence. The results of this work show that fluence uniformity and dose-effectiveness are governed by the alignment of longer residence-time areas with higher-irradiance regions. These findings demonstrate the value of a coupled Eulerian hydraulic-optical model as a practical design tool for evaluating how UV LED placement and velocity structure shape fluence development in flow-through reactors.

Access to safe drinking water remains an increasing concern across many regions of the United States due to aging infrastructure, changing water quality conditions, and challenges within premise plumbing systems. While municipal treatment commonly relies on a multi-barrier approach, building-level water treatment strategies remain limited in most residential properties, despite growing interest in point-of-entry (PoE) systems for additional protection and water quality management.

This work presents field data and operational observations from residential PoE UV water treatment deployments utilizing low-pressure (LP), medium-pressure (MP), and UV-LED technologies across diverse building applications in North America. Remote monitoring platforms and field testing were used to evaluate operational trends including flow behavior, UV transmittance (UVT), environmental and water temperature conditions, system usage patterns, and maintenance considerations over extended operation periods.

Three residential case studies are presented to compare deployment experiences across different UV technologies and infrastructure conditions. The presentation discusses real-world operational data collected from installed systems, including residential flow demand patterns, environmental variations, monitoring behavior, commissioning observations, and long-term operational trends. Field observations related to retrofit integration, installation constraints, maintenance accessibility, alarm management, monitoring integration, and operation under varying environmental conditions are also discussed. The findings demonstrate the value of operational field data in optimizing future residential UV deployments and highlight opportunities for future product development aimed at improving deployability, monitoring integration, serviceability, and long-term operational feasibility for installation and service providers.

Point-of-use (PoU) water filters are widely used in residential and commercial settings; however, field evidence increasingly suggests that neglected or improperly maintained filters may become reservoirs for biofilm-associated bacteria and opportunistic pathogens. While upstream disinfection is commonly recommended by manufacturers, it is rarely implemented in practice.

This work presents expanded field observations evaluating the role of point-of-entry (PoE) UV disinfection in supporting safer operation of distributed PoU filtration systems in residential and commercial environments. Comparative microbiological testing was conducted across filtered and unfiltered water lines in multiple buildings in the United States and Canada.

Across investigated sites, 90% of filtered water lines tested positive for bacteria, compared to 43% of corresponding unfiltered lines. In residential case studies, filtered fixtures showed bacterial loads exceeding 80,000 CFU/mL, including *Pseudomonas aeruginosa*, while corresponding unfiltered lines remained below detectable limits. In a commercial property, filtered lines initially tested positive for iron-related bacteria and *Legionella*; following PoE UV implementation and filter replacement, bacterial levels remained non-detectable over a six-month monitoring period. Additional side-by-side comparisons demonstrated consistently lower heterotrophic plate count trends in systems incorporating UV pretreatment upstream of filtration.

The findings support the role of PoE UV systems as a practical upstream microbial load management strategy within multi-barrier residential water treatment approaches, particularly in multiplex or commercial buildings where centralized filtration may be operationally challenging for end users and installers.

Low-resource communities without reliable drinking water treatment continue to face high risks of waterborne disease, particularly in schools with limited sanitation infrastructure. In 2024, a solar-powered UV LED rainwater treatment system was implemented at Rianyabayo Memorial Academy in Kenya through a collaboration among researchers and industry partners, supported by funding from Mitacs and contributions from CLEAR Inc. and MW Technologies. After 1.5 years of operation, the system demonstrated the reliability of integrating ultraviolet (UV) LED disinfection with photovoltaic energy to provide safe off-grid drinking water to ~350 elementary school students, highlighting the potential of decentralized UV water treatment technologies in underserved communities. Despite their promise, decentralized UV systems often face challenges related to long-term implementation and expansion due to limited public awareness, insufficient community engagement, and lack of sustainable funding. To address these barriers, The Student Water Project, a Canada-based non-profit organization, was established to investigate whether data-driven youth engagement strategies can strengthen support for decentralized UV water treatment projects. Early outreach demonstrated significant engagement, with digital media campaigns receiving over 40,000 views within the first three weeks of launch. The study investigates whether peer-to-peer campaigns, student-led outreach, and localized storytelling can improve community engagement and financial support for decentralized UV water treatment initiatives. Quantitative analyses are conducted using social media metrics, fundraising records, website traffic, participant data, and survey responses to assess audience reach, volunteer retention, fundraising outcomes, and changes in awareness of water accessibility and UV treatment technologies. A case study examines the “12,000 KM Run Challenge,” a student-led campaign supporting advanced UV LED water treatment systems and sanitation upgrades at Rianyabayo Memorial Academy. This work is expected to identify effective youth-driven engagement and fundraising strategies and develop a scalable framework to support the long-term sustainability of decentralized UV water treatment systems in underserved regions.

Photochemical degradation of perfluoroalkyl substances (PFAS) using vacuum-UV (VUV) has gain increasing attention in recent years. Compared with conventional photochemical remediation approach, such as UV 254 treatment, VUV technology offers the advantage of reagent-free operation. In VUV systems, two highly reactive species are primarily responsible for PFAS degradation: high energy photon and reactive radical hydrated electron (eaq-) generated during the water photolysis. However, the detailed mechanisms of PFAS degradation under VUV irradiation remain unclear. In this study, the degradation of selected long-chain and short-chain sulfonate and carboxylate under VUV was systematically investigated under different pH and dissolved oxygen conditions. Both degradation efficiency and defluorination rate were evaluated. Results showed that in-situ generated radical hydrated electron (eaq-) is capable of degrading both carboxylate and sulfonate compounds, whereas direct photolysis by 185 nm photons was effective only for carboxylate compounds. Defluorination efficiencies exceeded 80% was achieved during eaq- mediated reduction for all PFAS examined, while direct photon photolysis resulted in less than 20% defluorination. The study further revealed distinct degradation pathways for PFAS under direct high-energy photon irradiation and hydrated electron reduction. Transformation intermediates were identified using QTOF-MS and MS scan analyses, and corresponding degradation mechanisms were proposed. Kinetic analysis enabled the determination of quantum yields for carboxylate degradation under 185 nm photolysis, steady-state concentrations of hydrated electrons, and second-order reaction rate constants between PFAS and eaq⁻. In addition, a plug-flow VUV reactor was developed in the laboratory, and the electrical energy per order (EE/O) values were evaluated under varying initial PFAS concentrations, flow rates, and water matrix conditions.

UV systems for advanced wastewater treatment facilities (AWTF) have high UV dose requirements for 6-log adenovirus reduction. There are 3 relevant guidance documents: the USEPA Innovative Approaches (2020) specifies a required reduction equivalent dose (RED) of 276 mJ/cm² for 6-log virus inactivation; the NWRI UVAOP Guidelines (2025) recommend an RED of 1200 mJ/cm² for NDMA at UVT ≥ 95%/cm would achieve 6-log adenovirus inactivation; and the California State Water Resources Control Board Direct Potable Reuse Regulations SBDDW-23-001 (2024) requires a UV dose at least 300 mJ/cm².

Achieving these high-dose and high-dose per log (DL) demonstrations can be operationally challenging, but new high-DL test microbes and validation approaches like the combined variable (CV) approach from the 2020 Innovative Approaches document, can be employed.

We designed and built a pilot-scale UV reactor to be used in high-dose and high-DL AWTF and UVAOP demonstration projects. The performance was validated with T1UV, MS2 and Aspergillus brasiliensis spores with UV resistance from 4 - 433 mJ/cm2/log, over a range of flows (10 - 60 USgpm), UV transmittances (79 - 99 %/cm) and power settings (40 - 100 %). Equations were developed for measured performance as a function of tested variables. We compared approaches for obtaining 6-log virus credit by calculating the validated ranges (flow, UVT, power): a) using MS2 only where RED > 300mJ/cm2 (MS2 DL < virus DL); b) using T1UV and MS2 in a CV approach targeting virus DL, and c) using T1UV, MS2 and A. brasilliensis where virus DL is bracketed.

This presentation will cover the lifecycle of Loudoun Water’s TRWTF UV system design in Leesburg, Virginia. The original design was completed in 2018. The recent influx of data centers to Loudoun County has dramatically increased the water demand in the surrounding area, requiring plant expansion. The treatment plant expansion will occur in two phases, to bring the design flow up to 40 MGD. The Trap Rock Water Treatment Facility currently uses UV inactivation as a secondary disinfection mechanism. The design for the next phase utilizes almost a decade of real-world performance data to refine operational needs and utility preferences.

In addition to the County’s increasing water demands, several operational parameters have shifted since the conception of the original design. Data collected from nearby utilities indicate that a shift to stricter disinfection requirements may be required in the future. Additionally, the UVT of the influent water has increased since 2018. The new UV system is designed to offer better turndown to meet current and future needs without compromising dose reliability.

Finally, the UV system has historically been susceptible to power brownouts. To mitigate these problems, the system was backed up by an uninterrupted power supply (UPS) to ensure system reliability. The new UV system design provides simpler operation and maintenance and more intuitive system controls. The new system is designed to accommodate the peak flows for the next two phases of expansion. This UV system design focused on design evolution, system adaptability, and futureproofing.

The European Union RoHS Directive restricts the use of mercury in electrical and electronic equipment unless a technical exemption is granted. Within ultraviolet technologies, Annex III Exemptions 4(a)-I and 4(f)-IV currently permit the continued use of mercury-containing low-pressure and medium-pressure UV lamps across applications including water treatment, air and surface disinfection, curing, photochemical processing, and advanced manufacturing. These exemptions are currently under regulatory review, with the European Commission decision process expected to conclude in 2027. Although RoHS is an EU directive, its impact extends globally through electronics manufacturing, OEM product design, supply chains, and environmental compliance frameworks, including among North American UV technology manufacturers and end users.

This presentation provides an educational overview of how the EU RoHS exemption framework is structured for ultraviolet technologies, including how exemptions are reviewed, renewed, amended, or revoked within the European regulatory system. The session will discuss the scope and intent of Exemptions 4(a)-I and 4(f)-IV, the role of the European Commission and Öko-Institut, stakeholder consultation processes, and expected regulatory timelines. The presentation will further discuss the status of UV-LED technologies across UV-A, UV-B, and UV-C applications, including where mercury-free alternatives are commercially mature and where technical limitations still remain, particularly for applications relying on sub-240 nm emissions or very high-power broadband ultraviolet sources. Finally, the session will summarize the position of UV SAFE (UV Solutions for a Mercury-Free Earth) and the technical rationale behind its proposed amendment language for these exemptions, including alignment with broader Minamata Convention objectives and evolving global sustainability initiatives.

Driven by rising environmental awareness and the growing demand for ultraviolet-based disinfection, UV LED technology has advanced to a point where return on investment (ROI) calculated. Improvements in efficiency, optical output, and reliability now allow UV LEDs to function as practical replacements for UV mercury lamps. This presentation examines the current economic case for UV LEDs, with a focus on real-world replacement examples using Nichia’s commercially available UV LEDs.

While UV LED systems typically require higher upfront capital expenditure (CapEx) compared to mercury-based solutions, they offer compelling operational expenditure (OpEx) advantages. Quantitative ROI drivers discussed include reduced energy consumption through improved wall plug efficiency, extended operational lifetimes exceeding 10,000–20,000 hours, and significant reductions in maintenance frequency, downtime, and light source replacement labor. Additional cost savings are realized through instant on/off operation, elimination of warmup, and avoidance of mercury handling, disposal, and regulatory compliance costs.

Case studies are presented evaluating CapEx versus OpEx tradeoffs and total cost of ownership over system lifetime. These examples highlight applications where UV LEDs already deliver compelling ROI compared to mercury lamps and identify operational conditions that accelerate payback. The discussion demonstrates how continued performance improvements are making UV LED systems not only environmentally advantageous, but economically compelling today and into the future.

This presentation highlights Nichia’s commercially available UV LED portfolio spanning wavelengths from 270 nm to 405 nm, supporting a broad range of disinfection, curing, sensing, and analytical applications. Nichia’s vertically integrated approach encompassing materials science, epitaxial growth, device design, packaging, and high-volume manufacturing enables precise wavelength control, high source density, and reliable performance across the UV spectrum.

A direct comparison is presented between medium pressure mercury lamps and Nichia UV LEDs, focusing on source density, wall plug efficiency, and system level performance considerations. While mercury lamps provide high radiant output across a broad spectrum, UV LEDs offer narrowband emission, directional output, scalable source density, and wavelength selectivity that can be optimized for specific applications.

The presentation further discusses the UV wavelengths currently produced in volume manufacturing and the applications in which they are deployed, including water and air disinfection, surface treatment, medical and life science instrumentation, and industrial processes. Leveraging decades of optoelectronic manufacturing experience, Nichia continues to advance UV LED performance and scalability, enabling new system architectures and accelerating the transition from legacy mercury based UV sources to solid state solutions

The reliable performance of UV C LED systems is critical for public health applications; however, the lack of standardized reliability testing continues to limit the understanding of and confidence in lifetime claims and system design. This presentation reviews current challenges in UV C LED reliability testing and examines potential paths toward industry-wide standardization. While the Microbicidal Maintenance Method previously introduced by Nichia provides a valuable framework for accounting for wavelength effects and maintaining system efficacy, its effectiveness is constrained by inconsistent lifetime data from LED manufacturers and the absence of universally accepted test standards.

Existing reliability tests including Room Temperature Operating Life Test (RTOLT), High Temperature Operating Life Test, Wet High Temperature Operating Life Test, Low Temperature Operating Life Test, and Temperature Cycling are evaluated with respect to their ability to produce realistic, application-relevant performance data. Limitations of these methods, particularly when adapted from visible LED standards such as LM 80, are discussed.

The presentation proposes an expansion and refinement of LM 80-style testing specifically tailored to UV C LEDs, with emphasis on third party or certified laboratory testing to ensure repeatability and comparability. As a call to action, this work advocates the formation of a formal IUVA working group to develop best practices and advance a coordinated submission toward an IES technical report, enabling consistent, credible reliability metrics for UV C LED systems.

Background: Respiratory viral infections such as COVID-19 and influenza spread readily in long-term care (LTC) homes, where residents are at increased risk of severe outcomes [1-3] Far-UVC light has demonstrated viricidal effects in laboratory settings [4-5] and has been proposed as a supplementary intervention to reduce transmission in LTC.

Methods: We conducted a pragmatic, cluster-randomized controlled trial across three LTC homes in Nova Scotia, Canada. Resident neighbourhoods were randomized to receive active far-UVC lamps or placebo lamps in common spaces. Residents were followed from November 2021 to May 2025. The primary outcome was laboratory-confirmed infection (COVID-19, influenza, and RSV). We evaluated infection rate (Andersen–Gill), risk of first infection (Fine–Gray competing-risk), and cumulative infection burden (mean cumulative function). We evaluated indoor air quality and far-UVC irradiance to characterize fluence. Monitoring included ultrafine particles, ozone (O₃), and formaldehyde. Group labels are reported as Exposure 1 and Exposure 2 due to blinding.

Results: Among 509 residents, 234 infections occurred in 197 individuals. There was no clear difference between groups. The adjusted hazard ratio for recurrent infection was 1.04 (95% CI 0.67–2.07), and the subdistribution hazard ratio for first infection was 1.15 (95% CI 0.62–2.14). Mean cumulative infection burden was similar (1.30 vs 1.26 infections per resident). Confidence intervals were wide, and moderate benefit or harm cannot be ruled out. Intervention floors experienced low fluence rates (0.14–0.50 μW/cm²) and intermittent operation (~34% duty cycle). Ozone and formaldehyde levels were similar between groups (14.1 vs 12.9 ppb; 5.8 vs 5.9 µg/m³) and well below Health Canada guidelines [6]. Ultrafine particle concentrations were higher in control neighbourhoods.

Discussion: In this real-world LTC setting, no measurable difference in infections was observed. These findings highlight the importance of sufficient dosing and consistent operation in evaluating far-UVC in complex care environments. This study represents one of the earliest randomized evaluations of far-UVC in long-term care, integrating clinical and environmental data to inform future implementation and research.

References:

1. Canadian Institute for Health Information. “COVID-19’s impact on long-term care”, CIHI.ca.
2. Fisman DN, Bogoch I, Lapointe-Shaw L, McCready J, Tuite AR. Risk Factors Associated With Mortality Among Residents With Coronavirus Disease 2019 (COVID-19) in Long-term Care Facilities in Ontario, Canada. JAMA Netw Open. 2020;3(7):e2015957. doi:10.1001/jamanetworkopen.2020.15957
3. Centers for Disease Control and Prevention. “Viral Respiratory Pathogens Toolkit for Nursing Homes”, CDC.gov.
4. Buonanno, M., Welch, D., Shuryak, I. et al. Far-UVC light (222 nm) efficiently and safely inactivates airborne human coronaviruses. Sci Rep 10, 10285 (2020). https://doi.org/10.1038/s41598-020-67211-2
5. Eadie, E., Hiwar, W., Fletcher, L. et al. Far-UVC (222 nm) efficiently inactivates an airborne pathogen in a room-sized chamber. Sci Rep 12, 4373 (2022). https://doi.org/10.1038/s41598-022-08462-z
6. Health Canada. Residential indoor air quality guidelines, Indoor air quality resources for professionals - Canada.ca

This presentation will provide the UV community with an update on key considerations and emerging solutions for large-scale UV-LED treatment systems, with a focus on customer operation, regulatory compliance, and long-term system performance. Topics will include system validation, monitoring strategies, maintenance practices, in addition to addressing LED lamp replacement.

Conversations with industry experts indicate there is lack of clarity on how system performance is ensured when replacement of LED lamps may introduce shifts in emission wavelength, potentially affecting UV sensor response and dose verification. Beyond sensor spectral sensitivity, broader questions remain regarding effective monitoring methodologies for large UV-LED installations.

UV-LED systems represent a fundamentally different technology from conventional mercury vapor systems. Whereas mercury systems are dominated by component-level variance among a relatively small number of linear lamps, UV-LED systems rely on thousands of discrete emitters whose collective performance is governed by statistical averaging and array-level behavior. In short, mercury systems are dominated by component-level variance while LED arrays are dominated by the law of large numbers. The implications of these differences for optical and electrical monitoring strategies will be examined, including the advantages and limitations of various monitoring architectures. Finally, while mercury lamp replacement and maintenance practices are well established within the industry, the servicing of UV-LED arrays introduces new operational and maintenance considerations. The presentation will address practical approaches to maintaining UV-LED systems and their associated components to ensure reliable long-term performance.

Ultraviolet light-emitting diodes (UV-LEDs) are an emerging, mercury-free technology proven to be effective for disinfection of municipal water and wastewater. As with any developing technology, the UV industry and regulatory community continue to examine how key UV-LED characteristics affect system evaluation, validation, and full-scale application. Conventional low pressure mercury UV emits radiation with a single peak at 254 nm and a full width half maximum (FWHM) < 1nm. In contrast, UV-LEDs emit narrow band radiation with FWHMs of 10–12 nm. The peak broadness of UV-LEDs makes precise emission at a nominal wavelength (e.g., 280 nm) inherently variable, and as UV-LED systems become more prevalent and multiple manufacturers enter the market, LEDs marketed as a single wavelength may exhibit peak emissions ± 5 nm. LEDs can be “binned” to define reactor emission more narrowly. This, however, raises important questions regarding the necessity of binning and the appropriate bin resolution. Therefore, a key area of UV-LED research is understanding how small spectral shifts influence UV-LED dose delivery, microbial inactivation, and full-scale reactor validation. In this presentation, collimated beam results will be presented which investigated the effect of small changes in peak spectral output (278.3 vs. 280.6 vs. 284.1 nm) on microbial (MS2, T1UV, Legionella pneumophila) inactivation and subsequent validated RED values of a full-scale UV-LED reactor. These findings provide insight into the implications of spectral variability on UV-LED system evaluation and validation.

Collimated beam (CB) testing quantifies the UV dose delivered by a controlled UV light source and the resulting microbial inactivation, enabling development of organism-specific UV dose-response curves. It is also an integral part of UV reactor validation where CB results are used to interpret full scale performance. Established CB protocols require precise measurement of key parameters (e.g., sample depth, distance from the light, diameter of sample container) to calculate correction factors (petri, divergence, water, reflection) and subsequent delivered UV dose. While guidance has defined limits for certain parameters (e.g., petri factor > 0.9 indicating an adequate setup), other aspects remain convention-based (e.g., use of a petri dish) rather than strictly required. In practice, applications may necessitate tailored configurations, for example larger sample volumes to support microbial enumeration or lower petri factors to achieve sufficient exposure times. The impacts of such modifications on dose-response curves and on reactor validation outcomes are not well characterized. This presentation summarizes how variations in CB setup and correction factors affect measured inactivation and validation metrics. Using a UV-LED collimated beam, common test parameters including sample volume, sample container, water matrix, reflection control, distance from the light, and organism stock age were systematically varied, and the inactivation of MS2 and T1UV was evaluated. Resulting effects on dose-response behavior and on the validated reduction equivalent dose (RED) of a full-scale UV-LED reactor will be presented.

The main objective of this study was to investigate ultraviolet (UV) light treatment as an alternative to conventional disinfection methods for controlling biofilms in secondary drinking water storage containers used in humanitarian settings. A ray tracing model was developed using TracePro to predict UV irradiance at various points within a container similar to those used in humanitarian contexts. To verify the accuracy of the model, validation experiments were conducted in the laboratory while maintaining consistent conditions from the digital twin. These steps led to the identification of two locations of interest inside the jerry can: a moderate-irradiance location (MIL) and a low-irradiance location (LIL). Escherichia coli ATCC 25922 biofilms were grown on polycarbonate coupons to represent the naturally forming biofilms reported in literature. Coupons were installed in the experimental jerry can setup at the previously identified locations and treated at a UVC wavelength of 254 nm. Biofilm-bound cell inactivation was measured through plate counts and quantified using log reduction value (LRV). At a UV dose of 16 mJ/cm2, a LRV of 2.47 ± 0.75 (average ± standard deviation) was achieved at MIL while 2.99 ± 0.07 was achieved at LIL. Experimental data were fitted to the Geeraerd model and a log-linear model. The Geeraerd model was found to capture the dose-response relationship reasonably well (R² = 0.75). The results of this study suggest that UV light devices may be a viable technology for biofilm control in secondary drinking water storage containers in humanitarian settings. Future work should extend this approach to water storage structures relevant to Canada, including domestic storage used in rural, remote, and decentralized drinking water systems, to evaluate performance across a broader range of real world conditions.

UV C LEDs offer strong germicidal efficacy for rapid disinfection of surfaces, air, and water, positioning them as a promising next-generation technology. However, widespread adoption remains limited. From a development perspective when compared to blue LEDs AlGaN-based UV C devices face fundamental barriers in epitaxial crystal quality, light-extraction efficiency, and resistance to degradation of package materials.

This presentation highlights Nichia Corporation’s integrated approach to overcoming these barriers. Advances in epitaxial growth have improved material quality, while optimized device structures enhance light extraction and output performance. In parallel, the development of robust, UV resistant packaging technologies enables improved reliability and longer operational lifetimes.

By addressing these interdependent challenges simultaneously, Nichia is paving a path toward high-performance UV C LEDs. These advancements are expected to accelerate the of UV C LED technology across a wide range of applications enabling the transition from legacy Hg sources.

As aging ultraviolet (UV) disinfection systems approach the end of their service life, utilities and facility operators face increasing maintenance costs, energy inefficiencies, and compliance challenges. This presentation explores the benefits and practical considerations of retrofitting conventional quartz-sleeved UV systems with modern non-contact UV (NONCONUV) technology. Unlike traditional systems that require frequent quartz sleeve cleaning and lamp maintenance, NONCON UV systems utilize advanced designs that eliminate direct contact between UV lamps and process water, significantly reducing fouling, improving hydraulic performance, and enhancing dose delivery. Key topics include a comparison of lifecycle costs, retrofit feasibility, dose modeling, performance validation, and lessons learned from real-world installations. The session will provide attendees with a decision-making framework for evaluating retrofits, highlighting how NONCON UV systems can extend infrastructure life while improving regulatory reliability and reducing operational burden.

Speaker Name: Romeo Vela M.E, MBA

Speaker Bio: Formerly G.M Sunlight Systems UV Disinfection company. Formerly Operations Manager, Engineering Manager Siemens A.G. UV division. Currently Director of Engineering Glasco UV. UV Geek with 25 years’ experience designing, building, and selling UV disinfection systems for the municipal market.

Whole milk (WM) is a low UV transmittance fluid which limits the UV-C dose delivery due to its high optical attenuation coefficients. WM had an absorption coefficient of 30.72 ± 0.01 cm⁻¹ (UV Transmittance of 1.91 × 10⁻²⁹ %·cm⁻¹) and scattering coefficient of 53.57 cm⁻¹. A novel double helix UV-C system was designed with centrally positioned low pressure mercury vapor lamps, and its performance was evaluated for microbial inactivation in WM. The system was operated at 46 L·h⁻¹ with Reynolds number of 1167; Dean number 296 and residence time of 20.97 s per pass. WM was co-inoculated with MS2 bacteriophage, Escherichia coli O157:H7, and Salmonella Muenchen, and microbial survivors were enumerated using selective chromogenic media after each pass. Biodosimetry using MS2 bacteriophage determined reduction equivalent fluence (REF) values of 13.34 ± 2.95 mJ·cm⁻² for a single pass and 23.27 ± 1.28 mJ·cm⁻² for two passes. Challenge studies with Escherichia coli O157:H7 and Salmonella Muenchen achieved log reductions of 5.68 ± 0.20 and 6.10 ± 0.12, demonstrating pasteurization-equivalent pathogen inactivation and exhibited linear microbial inactivation kinetics (R² > 0.99). CFD simulations at 46 L·h⁻¹ demonstrated strong Dean vortex-induced secondary flow at the sinusoidal bends, reducing the Vmax/Vavg ratio to 1.48 and confirming stable counter-rotating vortices. Further proteomic analysis using LC-MS/MS revealed that the WM native proteins were better preserved after UV treatment compared to pasteurization. This indicates that this next-generation UV-C system effectively achieves regulatory-relevant microbial inactivation while preserving the nutritional quality and sensory attributes of milk.

UV‑C LEDs have made significant progress in recent years with respect to efficiency, output power, lifetime, and overall price-performance, enabling their increasing adoption in a wide range of disinfection systems. In contrast to conventional UV sources, UV‑C LEDs allow rapid and frequent switching without detrimental effects on lifetime, making them particularly well suited for dynamically operated applications. Their instant on/off capability and continuous adjustability of the driving current enable real‑time adaptation of radiant output to changing process conditions and treatment demand.

When combined with UV‑C sensors, this flexibility allows direct monitoring of the delivered UV dose and active adjustment of operating conditions, supporting dose compliance while minimizing unnecessary energy consumption. In this contribution, experimental results are presented that evaluate the impact of different operating modes - such as continuous operation at different current levels, pulsed operation, and dynamic current adjustment - on UV‑C LED lifetime. Furthermore, the lifetime behavior of LEDs operated under closed‑loop control, including compensation of optical aging by incremental increases in the driving current, is investigated and discussed.

In addition, a newly developed photodiode specifically designed for monitoring UV‑C radiation is introduced, demonstrating its suitability for integration into feedback‑controlled UV‑C LED water reactors. The results highlight the potential of UV‑C LED systems for adaptive, energy‑efficient, and sensor‑controlled water disinfection.

High-Density (HD) LED modules have been heavily demanded by the water treatment industry and semiconductor processing industry due to its feasibility to achieve better uniformity and higher photon density. HD ultraviolet (UV-C) LED chip-on-board (COB) architectures are therefore developed to enabling a new class of compact and high-power illumination systems. However, the efficiency of system performance is severely dominated by the LED packaging methods and the associated thermal solutions. This work presents a comparative evaluation of conventional 2-Pad (Cathode and Anode) flip chip and patented 3-Pad (Cathode, Anode and Thermal Pad) flip chip configurations for HD COB arrays, highlighting their impact on power density, thermal behavior, and integration limits.

A representative HD COB consisting of 90 UVC LED flip chips packed within a 14.8mm x 13.3mm footprint demonstrates the scalability of the flip chip platform, enabling the most compact system design with UVC LED. Integrating with an active cooling solution of 2LPM and 25C-Inlet, a thermal simulation shows that the 3-Pad configuration sustains drive currents up to 600mA per die and achieves overall optical output exceeding 10W while the maximum junction temperature is maintained below 85C. In contrast, the HD COB of conventional 2-Pad flip chip is restricted to 245mA per die while the maximum junction temperature reaches 85C, and outputs only 5W of optical power. Thermal imaging from experiments agrees with the simulation results and also confirms the improved heat extraction and reduced hotspot formation.

These results establish 3-Pad HD COB technology as a scalable platform enabling significantly higher photon density, and a much smaller footprint to achieve the same desired optical power.

Ultraviolet (UV) LED technology is increasingly utilized in applications such as disinfection, sensing, curing, and advanced manufacturing. However, many systems still rely on simple LED arrangements, with bare dies or flat lenses, that do not fully optimize the spatial distribution of UV energy at the target surface. Efficient delivery of photons is vital for applications where irradiance uniformity, energy efficiency, and system compactness can directly affect performance. This work presents an optical engineering approach to UV LED system design that uses beam shaping techniques to achieve targeted irradiance profiles.

Using advanced optical modelling and ray-tracing tools, including Zemax-based simulations, we analyze how optical components such as narrow beam lenses, wide area batwing lenses, and reflectors, can be integrated with UV LED sources to control angular emission and irradiance distribution. The study examines trade-offs between optical efficiency, uniformity, and system sizes while addressing practical constraints such as thermal management, LED spacing restrictions, and UV-transmitting optical materials.

Beyond improving optical performance, beam-shaping elements can significantly influence overall system design. By directing light more efficiently to the target, the required number of LEDs can often be reduced, which directly impacts system cost, bill-of-materials (BOM), and thermal management requirements. Lower LED counts can reduce thermal loads and simplify heat-sink design while maintaining or improving delivered dose.

The findings highlight the importance of optical design early in the UV LED system design process and provide practical guidelines for developing high-performance UV illumination systems tailored to specific application requirements. Case study examples will be shared.

Far-UVC (222 nm)-based advanced oxidation process (AOP) is one of the promising technologies for the removal of organic micropollutants (OMPs) from water. This study evaluated the performance of a UV222/ozone treatment for the degradation of atrazine (ATR), bisphenol A (BPA), and 4-nitrophenol (4-NP). For all three compounds, UV222/ozone showed substantially enhanced degradation compared with ozone and UV222 alone, demonstrating the synergistic effect of simultaneous UV222 irradiation and ozonation. Among the OMPs, ATR showed the highest decay rate (1.14 × 10-2 cm2/mJ), followed by BPA (6.29 × 10-3 cm2/mJ) and 4-NP (1.66 × 10-3 cm2/mJ). UV222/ozone exhibited removal efficiencies comparable to UV222/H2O2. The influence of background water chemistry was also investigated using nitrate-containing water, varying pH conditions (pH 5, 7, and 9), and real surface water. Nitrate enhanced OMP degradation, with the highest decay rates observed at 5 mg-N/L nitrate, where fluence-rate-normalized decay constants reached 2.37 × 10-2 cm2/mJ for ATR, 1.49 × 10-2 cm2/mJ BPA, and 2.55 × 10-3 cm2/mJ 4-NP. These results suggest additional reactive species generation and indirect photolysis in UV/nitrate system. Increasing pH improved degradation rates for the OMPs, likely due to accelerated ozone decomposition and .OH generation. At pH 9, decay rates reached 1.54 × 10-2 cm2/mJ, 8.46 × 10-3 cm2/mJ, and 1.81 × 10-3 cm2/mJ for ATR, BPA, and 4-NP, respectively. UV222/ozone treatment also achieved measurable degradation in real surface water samples, although lower than those observed in DI water. These findings demonstrate that UV222/ozone is a promising treatment strategy for OMP removal.

The persistence of organic micropollutants (OMPs) such as carbamazepine (CBZ), diethyltoluamide (DEET), and caffeine (CAF) in wastewater recycling streams poses challenges to water safety. These compounds often accumulate in reverse osmosis concentrate (ROC) at high concentrations, causing challenges in disposal. In recent years, far-UVC technology has emerged as a promising technology for water treatment. In this study, we evaluated the potential advantage of using far UVC to remove OMPs from ROC. Three oxidants (H2O2, NH2Cl, and Cl2 at 100 μM each) were tested in ROC. The addition of H2O2 showed enhanced removal, increasing decay rates by 10-14 times for CBZ (1.7 × 10-2 cm2/mJ), DEET (1.3 × 10-2 cm2/mJ), and CAF (2.1 × 10-2 cm2/mJ), compared with UV254. NH2Cl and Cl2 also showed similar performance trends. Despite the high abundance of nitrate, organic matter, and other background constituents that typically cause light screening and limit the effectiveness of AOP, substantial removal was achieved in ROC. In ROC, the addition of oxidants maintained about 70% removal performance compared with buffered DI. Study revealed that presence of nitrate enhanced H2O2 decay. Mechanistic investigations showed minimal contribution from •OH, •NO2, and ONOO-, generated from nitrate photolysis, to H2O2 decay. Quenching experiments using tert-butanol and sensitization experiments with acetophenone suggested that nitrate excited-state generated from photolysis contributes in sensitizing H2O2 decay leading to higher OMP removal. These results highlight far-UVC/AOPs as a sustainable and energy-efficient strategy for controlling persistent OMPs to achieve safer disposal of RO concentrate.

Far-UVC irradiation at 222 nm has been gaining attention as a promising technology for the inactivation of airborne pathogens in indoor spaces. Although several experimental and CFD studies have shown its efficacy, the high computational cost of CFD makes it difficult to use for design optimization and parametric studies. The aim of this work is therefore to develop and validate a ROM that can predict the steady-state pathogen inactivation in mechanically ventilated rooms.

The proposed ROM is built in three levels. The first level is an analytical well-mixed model that takes into account the main loss mechanisms in the room (ventilation, wall deposition, settling, biological decay) together with a UV inactivation term that is calibrated from the lamp emission profile. The second level adds a Green's function correction to capture the concentration gradient near the source. The third level is a hybrid approach where a Gaussian process is trained on CFD data to learn a correction factor on top of the analytical model. This way we keep the physical meaning of the equations and at the same time benefit from the spatial accuracy of the CFD. The training data is produced from a high-fidelity CFD simulations in OpenFOAM. The model gives a good agreement with the published experimental data, especially for the multi-lamps cases where the UV field is more uniform. In the end, the developed ROM can be evaluated in only a few milliseconds, which makes it suitable for rapid design exploration and parametric studies.

UV radiation is measured using various photodiodes (Si, AlGaN, or SiC) or discharge tubes. Due to their design, discharge tubes have a limited life time. Si and AlGaN photodiodes degrade under UV radiation, which can be explained by their low atomic binding energy. SiC photodiodes show no degradation under UV radiation. The assembly process of the photodiodes also plays an important role. The inexpensive epoxy bonding process can lead to reduced sensitivity of the photodiode while exposed to high temperatures together with high radiation levels. The reason for this is the condensation of decomposed epoxy material on the inside of the photodiode window. In these applications, the use of organic-free bonding processes results in the desired resistance to degradation. SiC has limited sensitivity in the UVA range and a relatively high temperature coefficient in the UVA range. Accordingly SiC is no ideal solution for UVA measurement. For UV measurement in the boundary region between UVA and visible light, novel UV photodiodes based on InGaP are used. These are not as radiation-hard as SiC but are significantly more robust than photodiodes made of Si or AlGaN.

In Japan, ultraviolet (UV) treatment is utilized at water treatment plants as a measure against chlorine-resistant pathogens such as Cryptosporidium. Since UV treatment equipment is highly compatible with existing water purification facilities, its adoption has been steadily increasing.

To further expand the application of this technology, the Japan Water Research Center (JWRC) launched the second phase of the UV-ACE Project, which is based on industry-government-academia collaboration. The project aimed to clarify the application procedure for the Modification of Water Treatment Facilities and conduct case studies to show references to water utilities considering adopting UV treatment. Additionally, the project conducted experimental evaluations of UV treatment’s impact on bromate formation potential, which had been a primary concern regarding the installation of UV systems.

Furthermore, JWRC is updating its certification standards to introduce screening criteria for simulation results generated by the ray-tracing method.

Following the May 2019 partial revision of the Guidelines for Countermeasures against Cryptosporidium etc. in Water Supplies by the Ministry of Health, Labour and Welfare, the scope of application for UV treatment was expanded to facilities using surface water as their raw water source. Consequently, the adoption of UV treatment equipment is expected to grow even further. By promoting and disseminating these initiatives, the JWRC continues to contribute to the improvement of water quality in Japan's water supply systems.

Empirical combined-variable (CV) equations are widely used in ultraviolet (UV) reactor validation to predict microbial inactivation as a function of hydraulic and optical conditions. Despite their widespread application in regulatory frameworks and engineering practice, these equations remain fundamentally empirical. In this work, a theoretical framework is developed linking stochastic dose distributions to reactor-scale inactivation performance under monochromatic UV irradiation. Starting from first-order microbial kinetics and dose distributions, reactor performance is expressed as a Laplace functional. Using asymptotic analysis, it is shown that inactivation follows a power-law dependence on a combined variable. The exponent is controlled by the lower tail of the dose distribution, which is governed by Beer--Lambert attenuation and hydrodynamics. Numerical simulations confirm the emergence of this scaling. The results provide a theoretical basis for the empirical CV equation used in UV reactor validation.

Computational fluid dynamics (CFD) modelling of UV disinfection reactors typically relies on commercial codes or in-house tools, limiting reproducibility and extensibility for the UV community. We present an open-source framework for OpenFOAM 13 that couples a discrete-ordinates radiation transport solver with a Lagrangian dose-tracking post-processor, targeted at UV reactor design and validation.

The radiation library solves the radiative transfer equation with multi-band spectral support, anisotropic phase functions (Henyey-Greenstein, Schlick, Rayleigh, Mie), and refractive interfaces. Extinction models cover constant coefficients, species-linear absorption, Rayleigh and Mie scattering, and per-band molecular absorption from user-supplied cross-sections, enabling spectrally-resolved 222 nm modelling with explicit O₂/O₃ absorber chemistry. Boundary conditions include Lambertian emitters, specular/diffuse reflectors, collimated beams, and real luminaires via IES LM-63 photometric files. The library can run standalone, embedded as an fvModel in a host flow solver, or as a solver module in multi-region cases with refractive coupling between fluid and quartz domains.

The dose-tracking library integrates D = ∫G·dt along particle trajectories using OpenFOAM's barycentric-tet tracker, with selectable seeding (patch injection, point injection), turbulent dispersion (Gosman-Ioannides discrete random walk), inertial motion (Ornstein-Uhlenbeck drag with optional gravity and Brownian motion), and specular wall reflection. Outputs include per-particle dose CSVs, summary statistics with log-reduction reporting at user-supplied inactivation kinetics, and VTK trajectory files for visualisation.

The framework reproduces the Sozzi & Taghipour (2006) annular L-shape reactor benchmark at 25 GPM to within 3.4% on mean dose (70.3 vs 68 mJ/cm²). Twenty-one regression tests with analytical references run on every code update to ensure continued accuracy. The code is released under an open-source license to support reproducible UV reactor design across the community.

URL: https://github.com/DeGrootResearchGroup/of-optical-radiation

The ultraviolet-hexagonal boron nitride photocatalytic treatment process (hBN+UVC/VUV) has recently been recognized as one of the most energy-efficient methods for destructive treatment of water contaminated by poly-/perfluoroalkyl substances (PFAS) at ppb-range concentrations, comprising hBN particulate suspension irradiated by low-pressure mercury (LP-Hg) lamps (254/185 nm). Uniquely, in addition to effective destruction of perfluorocarboxylic acids, the process also achieves oxidative photocatalytic degradation perfluorooctance sulfonate (PFOS), with the latter showing greater reliance on the 185 nm vacuum UV (VUV) irradiation component. Herein, the synergism induced by combined UVC/VUV irradiation of PFOS/hBN was investigated further and hypothesized to rely on both: (1) photogeneration of hBN charge carriers by UVC, and (2) direct HOMO->LUMO+n photoexcitation of adsorbed PFOS by VUV, promoting it to a more reactive excitation state. Comparisons across various irradiation configurations involving monochromatic and dichromatic LP-Hg lamps and a xenon excimer lamp showed that efficient PFOS degradation was predicated on simultaneous and congruent excitation by both UVC and VUV photons. In contrast, degradation of perfluorooctanoic acid was more efficient and did not share such requirement or demonstrate observable synergism. Pulse VUV irradiation experiments with varied waveform characteristics showed that PFOS degradation by hBN was more efficient with sharper/intense pulses, compared to broader/weaker pulses at the same average intensity, thus indicating a multi-photon excitation mechanism.

Water Research Foundation 5173: Feasibility of Full-Scale Implementation of UV LED Disinfection aims to perform a quantitative assessment of the feasibility of full-scale ultraviolet light emitting diode (UV LED) water disinfection reactors for drinking water and wastewater treatment applications. Led by Dalhousie University, Southern Nevada Water Authority and Black & Veatch this project has evaluated various regulatory and technical aspects of UV LED implementation for disinfection. UV LEDs are an emerging disinfection technology which offer numerous advantages compared to conventional UV systems including instantaneous start/stop, selectable wavelength, and are mercury-free. This presentation will provide an overview of the advancement of full-scale UV LED treatment technologies, a review of current UV LED technology, novel research on UV LED disinfection efficacy, and share preliminary outcomes relevant to wastewater applications that could employ UV LED systems.

This presentation will provide an overview of the study, a review of current UV LED technology, and the preliminary outcomes relevant to the wastewater disinfection and reuse applications that could employ UV LED disinfection. The presentation will include results of a regulatory survey, incorporating input gathered from over 15 members of the study’s Regulatory Committee from the US and Canada, relating to gaining regulatory acceptance in municipal disinfection applications. These results will help inform regulatory perspectives on the knowledge gaps and concerns related to UV LED implementation. Results from a literature review on UV LEDs as a one water disinfection technology (published 2024) prepared as a part of the interlaboratory study will be presented to compare UV LED disinfection efficacy. In addition, a performance and economic evaluation, including operating cost comparisons, will be presented for UV LED and low-pressure wastewater disinfection systems. Advancements in UV LED system monitoring and validation will be also discussed as the complexities of UV LED emission spectra and UV Dose calculation require modification to existing regulatory frameworks. Overall, this presentation will provide an introduction to UV LED technology for disinfection, regulatory considerations as determined from a diverse group of regulators, and summarize a performance and economic evaluation for the technology to support the feasibility of full-scale UV LED installations.

Far-UVC irradiation has proven to be an efficient technique for inactivating viruses, successfully destroying their nucleic acids while posing little risk to mammalian tissues. This study evaluates the effectiveness of a 235 nm Far-UVC LED Proximity Module in inactivating two strains of avian influenza H5N1 — A/Indonesia/5/2005 WT and A/Texas/37/2024 genotype b3.13 — under controlled laboratory conditions. The aim was to quantify the reduction in viral infectivity following brief, defined exposure intervals.

1 mL of viral suspension was placed in the center of a six-well plate and irradiated at a fixed distance of 10 cm for 20, 40 or 90 seconds. After irradiation, each treated sample was subjected to 1-log₁₀ serial dilutions and inoculated onto MDCK cell monolayers. The plates were then incubated for five days at 37 °C in a 5% CO₂ environment. Residual infectivity was evaluated using the TCID₅₀ method based on observation of cytopathic effects and colorimetric analysis. Log₁₀ reductions were calculated using the Spearman–Kärber technique.

The device demonstrated a notable time-dependent antiviral effect. Log₁₀ reductions of 3.39, 4.66 and 6.54 were observed for the A/Indonesia strain after 20, 40 and 90 seconds, respectively. The A/Texas strain exhibited reductions of 4.15, 5.16 and 6.17 log₁₀ under the same exposure conditions. This study confirms the device's strong virucidal effectiveness, with significant inactivation achieved over short exposure periods.

In conclusion, the 235 nm Far-UVC LED Proximity Module achieved rapid and substantial reductions in the infectivity of both examined H5N1 strains. These results validate its potential application in biosafety and infection control settings that require the efficient reduction of viral loads in liquid suspensions.

Hydrogen peroxide (H₂O₂) is an attractive oxidant for advanced oxidation processes and decentralized water treatment because it produces minimal harmful byproducts and can be generated on-site. This study presents a scalable visible-light photocatalytic reactor platform that integrates bismuth vanadate (BVO)-coated side-emitting polymeric optical fibers with oxygen delivery systems to achieve energy-efficient H₂O₂ production. The reactor uses low-power 400–440 nm LEDs to directly irradiate immobilized photocatalysts along the optical fiber surface, improving photon utilization while minimizing light attenuation and catalyst recovery challenges associated with slurry systems.

Phase I scale-up studies expanded reactor volume from 40 mL laboratory reactors to 1.1 L continuous-flow systems containing bundled optical fibers. Multiple oxygen delivery approaches, including hollow-fiber membrane aeration and oxygen nanobubbles, successfully achieved H₂O₂ concentrations exceeding 100 mg/L while maintaining energy demands below NASA targets of 5 kWh per 10 L treated water. Optimized fiber packing density, light coupling, and porous dip-coated catalyst layers improved mass transfer and reactor efficiency. Long-duration testing demonstrated stable H₂O₂ production over hundreds of operational hours with negligible catalyst degradation. Results demonstrate a modular and scalable pathway for decentralized H₂O₂ generation with potential applications in UV/H₂O₂ advanced oxidation, point-of-use water treatment, and autonomous water systems in remote or resource-constrained environments.

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A reactor system titled BLUCIFRR (BLueprint Uniform Cylindrical Integrating Fluence Rate Reactor) was developed to allow quantification of challenge agent UV inactivation kinetics in the aerosol phase. A physical prototype was designed based on numerical (ray tracing) simulations of the fluence rate field and the deterministic fluid mechanics for the system operating in the laminar regime. A prototype BLUCIFRR was 3D-printed, then interior surfaces were lined with highly-reflective and highly-diffusing materials.

Physical measurements of the fluence rate field were conducted using a radiometer with a spherical detector as well as a micro-fluorescent silica detector, both of which were designed and built to collect measurements that mimic the literal definition of fluence rate. In addition, gas-phase actinometry experiments were conducted on the reactor based on ozone (O3) formation and photodecay of carbon tetrabromide (CBr4). Together with ray tracing simulations, these efforts provide comprehensive, complementary descriptions of the fluence rate field delivered by BLUCIFRR. Moreover, because these measurements and simulations were all conducted in the near-field, they add to the general knowledge base regarding fluence rate quantification in the immediate vicinity of UV-C lamps.

The primary goal for development of BLUCIFRR was to provide a device and methods to quantify UV-C fluence-response behavior for challenge agents in the aerosol phase. For these experiments, coliphages MS2 and T1 were examined. Inactivation responses for these challenge agents were quantified over a range of operating conditions, defined by gas flow rate, the number of operating lamps, and lamp output power. Because the fluence distribution could be accurately calculated for each operating condition, the intrinsic kinetics of inactivation (i.e., fluence-response behavior) could be accurately calculated. Similar experiments were conducted to quantify the kinetics of photochemical damage to UV-sensitive DNA amplicons (SafeTraces).

The results of these experiments demonstrate the performance of a device and method for quantification of UV-C disinfection kinetics for aerosolized challenge agents. We anticipate that this device can be applied for accurate quantification of these kinetics for human pathogens and other agents.

Germicidal Ultraviolet (GUV) systems can be effective for reducing transmission of respiratory illnesses, including influenza, the common cold, measles, COVID-19, and tuberculosis. However, several important information gaps exist that are needed to inform GUV system designs. Among these are reliable, quantitative descriptions of UV-C inactivation kinetics (i.e., “UV dose-response behavior”) for aerosol-phase pathogens and challenge agents. Several reports of devices and methods for characterizing these kinetics have been presented in the literature, but most (if not all) of these previous efforts have had notable flaws, often related to errors in quantification of the UV fluence distribution delivered to challenge agents.

To address this need, a project was initiated to develop devices that deliver quantifiable fluence distributions to aerosolized challenge agents. The first prototype involves a cylindrical chamber with highly-reflective interior surfaces and four independently-controlled, dimmable Far UV-C lamps. The output of the lamps is imposed onto internal reflective surfaces and ultimately to the interior of a cylindrical quartz tube. This configuration yields a fluence rate field within the cylindrical quartz tube that is highly uniform and quantifiable. Challenge agents are introduced to the reactor using a Collison nebulizer, with sample collection by a condensation-based bioaerosol sampler. Aerosol-laden air flows through the system at a constant flow rate that falls within the laminar regime. This combination of attributes allows accurate quantification of the fluence distribution by an analytical solution. As such, the kinetics of inactivation can be estimated by an inverse calculation.

This presentation, which is intended as the first of a two-part series, will provide a summary of the theoretical foundation for development of the BLueprint Uniform Cylindrical Integrating Fluence Rate Reactor (BLUCIFRR). Details of prototype design will be presented, including calculations of the fluence rate field and definition of fluid mechanics. The interplay between these features dictates the fluence distribution delivered by BLUCIFRR as a function of its operating conditions (lamp power and flow rate). In turn, these calculations inform design of experiments that were conducted on the system (presentation part 2).

Background: Healthcare-associated infections(HAIs) and antimicrobial resistance(AMR) remain significant challenges in healthcare, posing risks to patients and staff. Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp. and E. coli, the ESKAPEE pathogens, are a class of bacteria which are common causes of HAIs and at high risk of becoming more resistant to drug treatments. Hospital disinfection and hygiene protocols are not always effective. Sinks are known to be a reservoir and amplifier of AMR bacteria. Far-UVC is promising for continuous disinfection of surfaces and air in occupied rooms. We implemented a sink-targeted far-UVC trial in two fully operational hospitals in Bolivia, where ESKAPEE pathogens have been detected.

Methods: We are conducting a multi-site sink-targeted two-arm, double-blinded, cluster randomized control trial in two hospitals where the intervention arm receives functional far-UVC lamps while the control receives shams. The primary trial endpoint presence or absence of culturable ESKAPEE pathogens from sink surface swabs. From baseline samples taken in May 2025, a sample size calculation resulted in 40 clusters(sinks), 10 lamps per study arm, per hospital. Secondary endpoints include quantification of ESKAPEE pathogens in swabs and air samples, air chemical concentrations(ozone, CO2, PM2.5, RT/H, irradiance) and far-UVC acceptability amongst hospital staff. We hypothesize that the positivity rate for presence of ESKAPEE pathogens amongst intervention surface swabs will be significantly lower than that of the control arm.

Results: The study period is ongoing, we expect to complete data collection in August 2026.

Conclusions: It is known that far-UVC disinfection is efficacious against ESKAPEE pathogens in laboratory settings. This is the first study which examines the use of far-UVC against ESKAPEE pathogens in occupied hospitals. Our trial aims to demonstrate that far-UVC is an effective way to reduce the number of ESKAPEE pathogens in a hospital setting.

Pacific Northwest National Laboratory has been conducting research and development on germicidal ultraviolet (GUV) technologies to evaluate their potential to reduce building heating, cooling, and construction costs. This work spans field studies of real world GUV installations, laboratory testing to characterize performance and indoor air quality (IAQ) impacts, and advanced simulations to quantify energy outcomes. A central finding is that GUV systems can deliver equivalent clean air performance while using up to 90% less energy and achieving 30–60% lower lifetime costs (energy, construction, and maintenance) compared with traditional HVAC only approaches. This presentation will highlight recent results, including two new GUV field evaluations, product level testing to quantify IAQ impacts, and a life cycle cost analysis comparing GUV with alternative air cleaning and ventilation strategies. The session will also introduce an emerging project that applies AI based surrogate modeling to optimize GUV system design.

Recent advances in UV LED technology are enabling increasingly complex and scalable UV systems across disinfection, healthcare, industrial processing, and environmental applications. However, traditional centralized constant-current architectures can create significant challenges in large or modular UV platforms due to forward voltage variation, thermal imbalance, scalability limitations, and system integration complexity. This presentation explores board-level regulation strategies that improve the flexibility, reliability, and intelligence of modern UV systems.

By distributing current regulation and protection functions to the PCB level, UV modules can operate independently while sharing a common constant-voltage power distribution architecture. This approach reduces the effects of LED forward-voltage variation and junction temperature differences that commonly lead to current imbalance and accelerated degradation in parallel LED arrays. Board-level regulation also enables simplified system expansion, modular replacement, and improved consistency across large-scale installations.

The presentation further examines how embedded sensing and onboard control features can enhance overall system capability. Thermal monitoring, fault protection, dimming control, and integration with standard industrial control platforms can be implemented directly at the module level using readily available components and communication interfaces. These strategies allow UV systems to become more adaptive, serviceable, and application-specific without requiring major changes to the central power architecture.

Practical design considerations related to power distribution, PCB implementation, thermal behavior, and system integration will be discussed using real-world UV LED examples. The presentation highlights how distributed regulation and embedded controls can support the next generation of scalable and intelligent UV systems while improving operational reliability, maintainability, and long-term performance.

This study provides a comprehensive viability assessment, or stress-test, of UV LED systems across five critical domains to determine their readiness for full-scale adoption.

•Technical Feasibility. Showing clear evidence of being past the proof-of-concept stage (does it do what it claims in a controlled environment), this assessment criteria has a stronger focus on scalability and reliability. Recent advancements have significantly improved wall-plug efficiency and optical power, with 10% / 200mW+ UVC LEDs now available. Covering also how wavelength-specific pathogen targeting can be used to optimize the inactivation of specific pathogens.

•Economic Factors. Cost-benefit analysis case studies show a mixed picture of where capital expenditure is often higher than traditional low-pressure lamp systems, but a closer match to medium-pressure lamp systems. Additionally, it will be shown that the total cost of ownership is rapidly reaching parity. The stress-test here looks at justification for the cost of switching technology and related infrastructure implications. •Regulatory and Legal: A seemingly simple question of does UV LED technology meet current industry safety performance standards, shows a nuanced picture. Compliance frameworks are evolving to accommodate non-mercury sources, but this presentation will outline specific assumptions that need to be documented to provide widespread acceptance. There is a key underlying driver that cannot be ignored in relation to the global consensus to eliminate mercury products under the Minamata Convention on Mercury – the assessment will review implications.

•Operational and Social: UV LEDs offer operational flexibility through instant on-off switching, eliminating warm-up times, broader temperature range tolerance and potentially more precise dose pacing. These characteristics have been proven in decentralized and intermittent flow applications. More broadly, an assessment of how hard it is for users to learn/use this new technology and how social perception plays a role in technology viability. •Environmental: From a sustainability standpoint, UV LEDs align with global mercury-free initiatives. Further consideration should be given to life cycle assessments also that indicate the lack of hazardous waste and potential for renewable energy integration offer a lower long-term environmental footprint.

This assessment concludes that UV LED technology viability shows very strong correlation across a broad range of small-scale and decentralized systems, in addition to select cases in full-scale industrial and municipal applications. It suggests that ongoing improvements in power density and standardization will broaden the viability gap for wider adoption in large-scale municipal implementation and this can be supported by more quantification in economic and environmental evidence.

Indoor air disinfection technologies such as germicidal ultraviolet (GUV) are gaining attention as tools for reducing airborne infection risk in shared indoor environments. However, successful implementation depends not only on technical performance, but also on whether occupants understand, trust, and accept these systems in practice. This study examined how non-expert community members interpret indoor air quality (IAQ), shared-air infection risk, and GUV systems, with the goal of identifying communication and verification needs relevant to real-world deployment.

Using a community-engaged qualitative design, we conducted focus groups with 53 participants and interviews with 16 key informants in rural and suburban communities. Data were analyzed using Braun and Clarke’s thematic analysis framework, with attention to perceived risk, safety concerns, and expectations for system accountability.

Five themes emerged. First, IAQ awareness was largely reactive and sensory rather than preventive or measurement based. Second, responsibility for protecting family members shifted IAQ from a comfort issue to a health protection issue. Third, participants recognized shared indoor air as a pathway for infection but reported limited personal control over that risk. Fourth, acceptance of GUV followed a safety-first hierarchy: reassurance regarding exposure safety was needed before participants engaged with potential germicidal benefits. Fifth, participants emphasized institutional accountability, including verified performance, ongoing maintenance, and visible point-of-entry signage.

These findings suggest that an important barrier to GUV implementation is not only efficacy, but the translation of system operation into credible forms of occupant assurance. We propose an Indoor Air Verification framework linking institutional responsibility, verification practices, and visible disclosure to support public trust in shared indoor spaces.

Photocatalytic advanced oxidation processes (AOPs) offer a sustainable pathway for degrading emerging contaminants, yet industrial adoption remains limited by three primary engineering hurdles: (1) the prohibitive cost of recovering nanoscale catalysts from treated effluent (2) low quantum efficiency and (3) gradual decrease in photocatalytic activity due to a reduction in active sites on the photocatalyst surface, resulting in limited reusability of the photocatalyst. This study addresses these challenges by developing graphitic carbon nitride/titanium dioxide (g-C₃N₄/TiO₂) heterostructure nanorods optimized for high-efficiency UV-LED photocatalysis and facile [SG2.1]physical separation.

Unlike conventional spherical nanoparticles that require energy-intensive ultra- or nano-filtration, the synthesized TiO₂ nanorods, which are hundreds of nanometers to microns in length, leveraging an anisotropic morphology to facilitate recovery. These 1D structures exhibit superior sedimentation and filtration dynamics, allowing for easy separation via gravity or low energy filtration. To enhance photocatalytic performance, an S-scheme heterojunction was engineered through in-situ precursor polymerization of thiourea to form g-C₃N₄, establishing a chemically bridged interface that minimizes charge recombination. Testing under 365 nm UV-LED irradiation showed that the 20 wt% g-C₃N₄/TiO₂ achieved a kinetic rate constant three times higher than unmodified TiO₂, demonstrating high intrinsic photocatalytic activity[SG3.1]. Current research activities in this project are focused on the regeneration of used catalyst to clean surface using chemical washing (H₂O₂ and Cl) combined with UV to restore active sites and maintain long-term performance of the material. By integrating high-efficiency interfacial engineering with a practically separable morphology and robust regeneration protocols, this research provides a scalable solution for integrating advanced photocatalysts into existing municipal and industrial water treatment infrastructure.

The permitted use of UV disinfection devices in Germany is defined by the §20 list of the German Environment Agency (UBA). To date, UV-LED–based systems are not yet included in this list. Following a brief overview of the German regulatory framework, this presentation provides insights into the ongoing development of the German draft standard for UV-LED systems (working title E DIN 19294-5). The project was initiated within the WIPANO program and funded by the German Federal Ministry for Economic Affairs and Energy (BMWE). The resulting concepts and findings have been submitted to the responsible standardization committee for UV disinfection systems (NA 119-07-15-02) and form the basis for further normative development.

From the perspective of an accredited testing body, key elements of the proposed validation approach are discussed, including biodosimetric testing, the integration of CFD-based worst-case analyses, and technical characterization of UV sources.

In addition, the test concept and first results from a large-scale UV-LED pilot reactor are presented. The reactor follows the layout of a conventional UV system and allows a direct comparison of different UV-LED generations with respect to disinfection performance and electrical efficiency. Installed at a German waterworks and operated with drinking water–quality test water, the system was investigated over a wide operating range, covering UVT₁₀ values between 97.5% and 80% and flow rates from 250 to 800 m³/h. The results provide practical insights into the applicability of the current normative framework and the performance of UV-LED technology under realistic operating conditions.

Computational fluid dynamics (CFD) has become an important tool for UV disinfection research, design, validation, and performance assessment in both water and air applications. At a fundamental level, these systems share the same physical basis: fluid flow governs microorganism transport, the UV field determines local irradiance, and exposure history together with inactivation kinetics determines delivered dose and disinfection outcome. In practice, however, UV-CFD workflows have diverged because the engineering objectives, system configurations, dominant uncertainties, and performance metrics differ across application domains.

This presentation examines how those differences appear in practice and why they matter for model development, simplification, validation, and interpretation. In water applications, UV-CFD commonly supports validated reactor performance assessment, including prediction of RED or log inactivation, evaluation of dose non-uniformity, UV sensor and dose-monitoring behavior, installation-versus-validation comparisons, and troubleshooting of issues such as lamp failure, short-circuiting, and open-channel free-surface effects. In air applications, especially upper-room and room-scale disinfection, CFD more often focuses on ventilation-driven transport, exchange between irradiated and non-irradiated zones, aerosol trajectories, occupancy effects, and spatially complex environments that influence microorganism transport and exposure. In-duct air systems represent an intermediate case, sharing several features with reactor-type water applications while retaining aerosol-specific considerations.

By synthesizing literature and application experience, this presentation compares modeling strategies, validation expectations, and practical output metrics across the two fields. The goal is to provide a unified framework for understanding where UV-CFD methods can be transferred across water and air applications, where domain-specific priorities are required, and how practitioners can more effectively select modeling strategies for different UV disinfection problems.

The New York City Department of Environmental Protection (NYCDEP) operates one of the world's largest ultraviolet disinfection plants. The Catskill-Delaware UV Facility (CATDELUV) has the ability to treat 2,400 billion gallons per day as part of the NYCDEP's treatment of its unfiltered supply. This facility uses 56 Trojan reactors that each contain 710 low pressure - high output lamps (LPHO), for a total of 11,760 lamps in use at any time. With a cost of $215 per lamp, and a mandated limit of 15,000 hours of lamp operation, our facility can expect to spend $2.5 million on lamps alone every 1.7 years.

The use of LPHO lamps in UV facilities relies upon 1 UV intensity sensor for every 15 lamps. To comply with the Ultraviolet Disinfection Design Guidance Manual (UVDGM), a water supply has two choices for evaluating lamp output. The City's regulator, the New York State Department of Health (NYSDOH) requires that the NYCDEP use one of these two choices. As a result, over the past three years, the NYCDEP has implemented lamp output variability (LOV) testing, whereby the output of one quarter of all of the lamps is tested quarterly. The data generated by this testing has provided a great deal of information on the output variability of trojan lamps and has provided NYCDEP with the ability to set a minimum lamp output threshold. Based on data collected to date, this threshold will result in approximately 4% of new lamps to be discarded as too inefficient but will also allow treatment to take place with fewer sections of lamps on-line at one time. This change in operations will allow us to optimize plant treatment and efficiency.

This study quantifies radical generation in 280nm UV-LEDs/H₂O₂ and UV-LEDs/HClO advanced oxidation processes (AOPs) for drinking water treatment, using pCBA as a selective probe to determine the RCT parameter (~10-14 M·cm²/mJ) under systematically varied conditions.

Oxidant dose was the dominant driver of •OH production in the UV-LEDs/H₂O₂ system. pH exerted a moderate effect (pH 5 > 7 > 9) via radical speciation shifts: at elevated pH, •OH conversion to less reactive superoxide species suppressed RCT (the radical exposure parameter) by 30–40%. Lower temperature showed minimal influence over 4–20°C (6–14% RCT variation), confirming cold-climate operational resilience. Among water matrix constituents, humic acid was the predominant inhibitor (~37% RCT reduction at 5 mg L-1 as TOC ≈ 2.5 mg-C L-1) via combined UV attenuation and radical scavenging, followed by bromide (>30% at 0.1 mM) with additional risks of brominated byproducts. Bicarbonate showed a negligible impact (<6%).

Building on these findings, the UV-LEDs/HClO system was evaluated for geosmin (GSM) and 2-methylisoborneol (2-MIB) degradation. Both followed first-order kinetics with rate constants k = 2.38 × 10-3 and 1.86 × 10-3 cm²/mJ for GSM and 2-MIB (pH 6.0, 20°C). The temperature-induced rate reduction (20–30%) was substantially smaller than that for ozone-based processes (30–50%), demonstrating the superior low-temperature stability of UV-LEDs/HClO AOP.

To our knowledge, this is the first systematic evaluation of radical generation and its governing factors in 280 nm UV-LEDs-based AOPs, providing a mechanistic basis for optimizing UV-LED AOP performance under realistic drinking water conditions.

Growing water scarcity is increasing reliance on impaired source waters, including contaminated groundwater, impacted surface water, and advanced treated wastewater, to support sustainable municipal and industrial water supplies. In these applications, conventional treatment alone is often insufficient to address the combined risks posed by pathogens and trace chemical micropollutants such as industrial solvents and pharmaceuticals. Ultraviolet advanced oxidation processes (UV AOP) have emerged as a robust advanced treatment solution capable of simultaneously providing disinfection and the oxidative destruction of recalcitrant organic contaminants.

Despite its effectiveness, UV AOP remains a comparatively unconventional technology for many utilities, necessitating well-structured pilot and demonstration programs to confirm site-specific treatability, inform full-scale design, and build confidence among owners, regulators, and operators. Purpose-built, pre-assembled UV AOP demonstration systems address this need by enabling controlled piloting under representative hydraulic and water quality conditions. These systems allow utilities to characterize contaminant degradation kinetics, assess oxidant demand driven by matrix constituents, and evaluate operational considerations such as UV dose delivery, hydrogen peroxide control, and process monitoring.

This presentation reviews the key engineering and operational features of a pre-assembled UV AOP demonstration platform, including UV reactor configuration, oxidant dosing and quenching systems, automation and data acquisition, and performance validation tools. The role of these systems in accelerating project development—from water quality screening and pilot testing through operator training and full-scale system design—is highlighted. Collectively, UV AOP demonstration systems represent a critical bridge between emerging treatment needs and reliable, scalable advanced treatment solutions for water reuse and remediation applications.

Increasing clean airflow in buildings through ventilation or other means can help reduce the transmission of airborne diseases; however, achieving this improvement may pose challenges if HVAC systems are not designed for increased ventilation. In-room germicidal ultraviolet (GUV) technology offers a promising and energy-efficient approach for providing additional equivalent clean airflow. This presentation provides findings from a study assessing GUV systems’ contributions to equivalent clean airflow in two real-world installations: an office building and an elementary school.

The contributions of in-room GUV systems were evaluated by radiometric measurements of the average fluence rate and assuming multiple challenge agents that vary in UV-C susceptibility (MS2, M. tuberculosis, and human coronavirus HCoV-OC43). Additionally, DNA-tagged tracers were used in the school to quantify equivalent clean airflow. The radiometric and tracer methods were compared, and first cost estimates were calculated for each space considering multiple challenge agents.

The results show that the GUV systems provided significant contributions ranging from 13–125 cfm/person in the offices to the 28–252 cfm/person in the classroom when considering a range of susceptibility values for bacteriophage [FC2.1]MS2. The DNA tracer test in the classroom provided a measurement of 31 cfm/p, aligned with the lower end of the range using the radiometric method. These contributions enable meeting clean airflow goals without increasing ventilation. The findings demonstrate that designing for more common, higher-susceptibility pathogens can significantly reduce GUV system size and cost, enhancing feasibility. Additionally, the study demonstrates the utility of radiometric and air tracer methods for verifying GUV performance.

Far UV-C is a promising technology for inactivating airborne pathogens with minimal risk to human skin and eyes. However, its interaction with indoor air produces ozone and other byproducts, which must be considered in system design. A test method for measuring ozone, UL 867, was developed for electrostatic air cleaners and is now used to test far UV-C luminaires for compliance with UL 2998 (zero ozone emissions validation) used by manufacturers and referenced by ASHRAE 62.1 and 241. This presentation reviews findings of an interlaboratory comparison study of two far UV-C luminaires using the UL 867 test method. Ozone concentration is measured by two laboratories, allowing comparison of results between the devices and laboratories.

While reported environmental conditions in both laboratories complied with UL 867, the results revealed significant variability. Maximum ozone concentrations from one lab were consistently higher than the other, with differences between laboratories ranging from 1.5–2.5 ppbv for one luminaire and 56 ppbv for the second. The results suggest refinements may be needed to test methods to reduce measurement variability with far UV-C luminaires. Additionally, we propose that a test method to measure the ozone generation rate, rather than concentration, would be more informative and reliable metric for designing far UV-C installations.

The measurement of 254nm radiant power output from low-pressure mercury vapor lamps is routinely performed using calibrated radiometers and standardized protocols, providing reliable measurements. By contrast, there is no standardized method to quantify the 185nm output power of commercial-scale UV lamps, despite their widespread industrial use. Although 185nm radiometers are available, their measurement uncertainty is higher than that of 254nm radiometers, and their use is challenging due to strong optical absorption by oxygen and water vapor. To address this issue, investigators have used nitrogen blanketing or fiber-optic probes placed on the lamp or sleeve surface. However, these methods suffer from significant variability due to lamp temperature, water temperature, fiber optic acceptance angle, and absorption by oxygen and water vapor. Moreover, even when successful, they do not measure lamp output under actual operating conditions where the lamp is enclosed within a quartz sleeve submerged in water (conditions that greatly affect lamp output by altering lamp temperature and mercury vapor pressure). Therefore, a standard method to accurately quantify 185nm output under realistic application conditions would be highly advantageous.

This work presents an actinometric method, based on the Nash protocol, capable of measuring the 185nm output of a lamp under representative conditions. While the fundamental actinometric approach is not novel, its application in this work is highly relevant and impactful: the method is implemented in a flow-through UV system, enabling measurement of 185nm output from a commercial-scale lamp in water, as opposed to bench-scale lamps or configurations commonly found in scientific literature. The approach quantifies the 185nm output by measuring formaldehyde production during irradiation of a methanol-containing aqueous solution flowing through a reactor containing the lamp. The underlying mechanism involves vacuum-UV (<190nm) induced homolysis of water molecules, generating H• and HO• radicals. The hydroxyl radical subsequently reacts with methanol to yield formaldehyde, which is quantified spectroscopically. The rate of formaldehyde formation is directly proportional to the lamp's 185nm power output, enabling absolute or relative actinometric measurement.

We demonstrate the application of this method to a VUV lamp designed for industrial total organic carbon (TOC) destruction in ultrapure water. This method allows engineers and system designers to directly and accurately quantify the portion of the UV spectrum responsible for TOC destruction. Our results illustrate the feasibility and reproducibility of the actinometric approach as a practical alternative to radiometric method for 185nm characterization, providing accurate measurement of VUV output under relevant industrial conditions. The method offers a practical and reliable tool for validating performance, optimizing operation, and ensuring consistent TOC removal in high-purity applications.

Advances in UV source technology create the potential for improvements to UV-based processes for disinfection of pathogens, transformation of chemical contaminants and destruction of organic matter through photolysis and oxidation, in water, air and on surfaces. Krypton chloride (KrCl*) excimer lamps emit UV irradiation at 222 nm and are of growing interest for inactivation of viruses and oxidation of organic contaminants. This presentation will focus on research generated through irradiation of water with Far-UVC. Applications of UV in water treatment and reuse of impaired water include disinfection, photolysis, and oxidation and use of 222 nm UV has been shown to accelerate disinfection and oxidation processes. However, much of the fundamental photochemistry at 222 nm remains largely unknown, including the effect of 222 nm irradiation on organic matter transformation. This talk will review recent results from studies on water reuse and reclamation in the field of municipal water treatment including use of Far UVC and 172 nm excimer sources for treatment of water harvested from humidity condensate on space missions to meet water recycling goals in extreme environments. The focus will be on the role of different oxidative radical species that form in the presence of water matrix constituents such as nitrate, chloride and carbonate. These findings position far-UVC irradiation as a potentially valuable tool for water treatment applications where high virus log reductions and organic contaminant degradation are required.

Indoor Air Quality has moved from a niche engineering topic to a central public-health priority. The pandemic made it impossible to ignore that respiratory pathogens travel through the air we share. The question is no longer whether indoor air matters, but who is accountable for its quality.

UV-C is arguably the most mature and versatile air-treatment technology available today. Seventy years of evidence — from early tuberculosis wards to modern Far-UVC and UV-LED research — show that properly designed UV-C inactivates airborne viruses, bacteria, molds and bioaerosols across healthcare, animal husbandry, food processing, cleanrooms, public transport and odor control.

And yet UV-C air treatment remains dramatically under-adopted. The reason is not technological — it is normative. Existing documents are test methods, safety standards, or advisory guidelines. None tells a buyer what to look at, and none gives regulators the confidence to require UV-C where it could save lives and protect products. The contrast with UV water treatment — where indicator organisms, reference doses and certification schemes make the technology mandatory in many jurisdictions — is striking.

This presentation covers three things: what exists today, mapping the regulatory landscape alongside the extensive scientific literature already proving UV-C efficacy in air; what is still needed to move UV-C air from recommended to required; and how manufacturers bridge the gap today, through real client cases solved with engineering judgment and common sense.

The science is ready. The market is waiting. The standard is missing.

Quartz sleeve fouling is a primary factor limiting the efficiency of ultraviolet (UV) water purification systems, as mineral scaling, biofilm formation, and organic deposition reduce UV transmittance and increase maintenance frequency. This presentation discusses how a timed infusion of chemically initiated nanobubbles (CINBs) can be a non-chemical, low-energy strategy to prevent fouling on quartz sleeves.

CINBs are generated through vapor-phase interfacial conditioning of a carrier gas, which lowers surface tension and promotes rapid formation of sub-200 nm bubbles exhibiting high negative zeta potential (−30 to −60 mV). When introduced into the water stream in short, periodic dosing cycles (e.g., 2–3 minutes every 25–30 minutes), these nanobubbles disperse uniformly and persist due to electrostatic stabilization.

The high surface charge and nanoscale size of CINBs enable strong interfacial interactions with suspended particles, dissolved ions, and microbial communities. Electrostatic repulsion and disruption of cation bridging (e.g., Ca²⁺, Mg²⁺) inhibit nucleation and adhesion of mineral scale, while localized interfacial forces destabilize early-stage biofilms and organic conditioning layers.

Additionally, nanobubble-induced microstreaming and Brownian motion enhance boundary layer mixing at the quartz interface, reducing concentration polarization and deposit accumulation. The result is sustained UV transmittance, improved system efficiency, and extended cleaning intervals without reliance on harsh chemicals. This approach offers a scalable, retrofit-compatible solution for maintaining quartz sleeve performance in municipal, industrial, and decentralized UV purification systems. Decades of successful use in robust industrial heat exchanger systems provides clear evidence for use.

Krypton chloride excimer (KrCl*) lamps have recently emerged for applications to UV water treatment. These lamps promote superior disinfection and contaminant degradation during advanced oxidation processes (AOP), largely driven by greater absorbance of many water constituents at 222 nm, the wavelength emitted by KrCl* lamps, compared to 254 nm, the wavelength emitted by low-pressure UV (LPUV) lamps. In particular, nitrate absorbs light very strongly at 222 nm, and nitrate photolysis generates reactive species including hydroxyl radicals. Our earlier work demonstrated that 222 nm UV irradiation of environmentally relevant nitrate concentrations leads to highly effective de facto AOP. However, no previous studies have compared the efficacy of KrCl*/nitrate and conventional LPUV/AOP (LPUV/H2O2) in authentic water matrices.

In this study, we compare the abatement of two key organic micropollutants – 1,4-dioxane and N-nitrosodimethylamine – by UV222 (without added oxidant) and UV254/H2O2 directly in authentic wastewater effluent and water reuse sources containing varying nitrate concentrations (2-9 mg-N/L). UV222 achieves 2.8-3.9 higher 1,4-dioxane degradation rates, yielding an estimated electrical demand comparable to UV254/H2O2 (0.89-1.3x), even though LPUV lamps are at least 3.5x more electrically efficient than KrCl* excimer sources. Accounting for the added cost of oxidant addition for LPUV, UV222 is projected to reduce treatment operational costs by 12.4-21.8% compared to UV254/H2O2. In additional, although the waters exhibit low UV transmittance (<30% UVT at 222 nm), UV222 still provides 1.5-3.2 faster NDMA removal than UV254. Modeling work also suggests that removal of other micropollutants may be further enhanced due to generation of carbonate radicals and reactive nitrogen species. Lastly, nitrite – a product of nitrate photolysis – was found to form at significant concentrations (up to 1.2 mg-N/L), decreasing AOP performance and posing a risk for increased toxicity and challenges for regulatory compliance. These results illustrate that UV222 treatment of wastewater and drinking water containing native levels of nitrate can be an effective and cost-competitive UV/AOP.

The transition from free chlorine to chloramine in municipal water supplies has created challenges for pharmaceutical water systems due to chloramine’s stability and resistance to conventional dechlorination. Granular activated carbon (GAC), while widely used, often requires increased footprint, frequent maintenance, and careful operation to effectively remove chloramine, particularly under variable feed conditions.

A combined ultraviolet (UV) and GAC treatment approach provides a synergistic and robust solution. Low-pressure high-output (LPHO) UV systems emitting at 254 nm effectively destroy monochloramine via photolysis, reducing concentrations from ppm levels to below 0.02 mg/L. This upstream reduction significantly lowers the chloramine load on downstream GAC, allowing carbon to operate as a polishing step rather than the primary removal barrier. This integration delivers key operational benefits, including reduced biogrowth within GAC vessels, extended carbon life, and decreased maintenance requirements such as backwashing, sanitization, and carbon replacement - by a factor of 2 to 4x. UV treatment also provides simultaneous >3-log microbial inactivation, further mitigating biofouling risks and improving system reliability.

A pharmaceutical case study demonstrated the effectiveness of this approach. Following a municipal switch to chloramine, a facility experienced elevated TOC and THMs, resulting in production downtime. Pilot testing with a UV system achieved up to 99% chloramine reduction and an improvement in organic removal.

The validated solution enabled scale-up to a full UV system with GAC polishing, providing a reliable, cost-effective strategy for chloramine control and improved water quality in pharmaceutical applications.

Human activity remains a key challenge in maintaining contamination control in healthcare environments and cleanrooms. Despite specialized garments, strict protocols, extensive training, and advanced air filtration systems, human-generated contamination persists as a critical risk factor.

Far-UVC technology (200–230 nm), particularly at 222 nm using krypton-chloride excimer lamps, has emerged as a complementary approach to existing contamination control strategies. Its ability to inactivate microorganisms while being suitable for use in occupied spaces under controlled conditions enables continuous disinfection without disrupting operations.

This presentation focuses on the practical implementation of Far-UVC in real-world settings. Case studies from healthcare facilities and pharmaceutical cleanrooms will be presented, highlighting system integration, deployment strategies, and operational considerations. Key aspects include installation approaches, validation methods, interaction with existing protocols, and user adoption.

Performance data and observations from these implementations will be discussed, illustrating how continuous environmental decontamination can reduce microbial burden and support existing contamination control measures. Lessons learned, challenges encountered, and best practices will also be shared.

These case studies demonstrate how Far-UVC can be effectively integrated into critical environments, contributing to enhanced contamination control and supporting the evolution of healthcare and cleanroom standards toward continuous risk mitigation.

In an era marked by escalating humanitarian crises, driven by conflicts, natural disasters, and climate change, access to safe drinking water remains one of the most pressing challenges. According to the World Health Organization (WHO), over 2 billion people globally lack access to safe and reliable drinking water services, with humanitarian emergencies exacerbating this issue. In conflict zones like Ukraine or the Middle East, disaster-struck regions in Africa, Asia, and America, centralized water infrastructure often collapses, leaving communities vulnerable to waterborne diseases such as cholera, dysentery, and typhoid. In marginalized rural communities within developing countries such as Kenya, water and sanitation systems often depend on contaminated water sources, which are further compromised by inadequate sanitation and heightened climate vulnerability. Traditional purification and disinfection methods, including chlorination and boiling, face limitations in scalability, sustainability, and efficacy under such conditions. UVC LED technology, a proven in water dispensing applications, compact, mercury-free, and energy-efficient solution, is now revolutionizing decentralized water purification. Robust, mobile, Field deployed units, are achieving high inactivation rates of pathogens such as E. coli (4-log or 99.99% reduction) while consuming as little as 0.032-0.053 kWh/m³ of solar power with storage battery generated energy overcoming the limitations of mercury lamp-based systems in such applications. This talk explores the transformative potential of UVC LED systems in building resilience during humanitarian crises. The technology's mechanisms, advantages over conventional methods, real-world case studies, and the role of organizations like UV4Good in deploying these innovations where they are needed will be presented. By leveraging UVC LEDs, we can shift from reactive emergency responses to proactive, scalable, impactful strategies that empower local communities. UVC LED technology with sensing and AI capabilities represents a paradigm shift in decentralized water purification by offering resilient, sustainable, scalable, and portable solutions. These essential characteristics empower communities to thrive amid adversity and provide a pathway toward local control over precious water resources. UV4Good is at the forefront, bridging innovation and impact. As global challenges intensify, investing in UVC LEDs is not just a technological choice, it's a humanitarian imperative.

The climate emergency is a health emergency. Yet healthcare systems around the world continue to make major contributions to carbon emissions through single-use medical devices that are needlessly thrown away. This is forcing governments to take action demanding that a switch is made to reusable devices, such as the ‘Design for Life’ policy in the UK.

In this presentation we will show how UVC LEDs are enabling reuse of devices that were previously considered impossible to reprocess, thanks to the latest generation of UVC LEDs and optical materials. Examples of real-world adoption in the NHS will be given, in the fields of anaesthesia, outpatient clinics and community health.

All equipment and applications have been evidenced via testing to the BS8628:2022 standard, and this will be discussed as part of the presentation.

We will conclude by making a strong case that there is no longer a need to continue the exemption for mercury vapour lamps in this application, as our evidence clearly demonstrates that a viable, more sustainable alternative now exists with UVC LEDs.

Conventional UV Advanced Oxidation Processes remain the dominant treatment pathway for recalcitrating organic contaminants and micropollutants. However, their dependence on mercury based lamps and continuous chemical oxidant feed generates high annual costs at scale, introduce secondary contamination risk, and create regulatory burden associated with oxidizer storage and handling. No current single-unit process simultaneously addresses disinfection, micropollutant destruction, and emerging contaminants such as PFAS without chemical inputs.

Pulsed light (PL) technology offers a chemical-free, mercury-free alternative with a broadband, high-intensity xenon flashlamp emission (200–1,100 nm) delivered through stored-energy discharge at instantaneous photon fluxes orders of magnitude greater than continuous-wave UV systems. The broadband spectral output activates three simultaneous oxidation pathways: (a) direct photolysis, (b) in-situ hydroxyl radical generation via VUV water photodissociation, and (c) multiphoton absorption at peak power without chemical oxidant addition. This multi-mechanism architecture enables contaminant destruction across treatment timescales under 15 seconds in continuous flow-through configurations.

Triton UV's TRL-5 pilot-scale PL reactor has demonstrated 95.3% 1,4-dioxane destruction at an EE/O of 0.18 kWh/m³/order, approximately 80% below the conventional UV/H₂O₂ benchmark, with zero chemical inputs, independently validated. EPA field trials confirmed Log-1.4 E. coli reduction in 80% UVT secondary municipal effluent.

The literature base across seventeen peer-reviewed studies demonstrates greater than 99% degradation across pesticides, pharmaceuticals, PAHs, and algal toxins in analogous PL-AOP configurations. PFAS destruction via multiphoton C-F bond cleavage (BDE: 460–546 kJ/mol) is theoretically supported by the peak power regime. Scale-up toward 200+ GPM TRL-6 capacity is the primary development priority.

Airborne infectious disease transmission remains a primary driver of increased healthcare costs in senior living environments, underscoring the need for validated engineering controls. Beyond clinical impacts, outbreaks significantly increase operational expenses through staffing shortages, overtime, isolation procedures, and higher resource consumption, while also affecting energy use due to intensified ventilation and air treatment requirements.

A comparative, real-world analysis was conducted between Cardigan Ridge—where germicidal ultraviolet (GUV) was deployed in common areas—and matched control facilities without UV intervention. The implementation combined upper-room GUV for direct air disinfection in occupied spaces with in-duct UV-C solutions and portable air purifiers, creating a layered approach to indoor air quality (IAQ) management as prescribed by ASHRAE Standard 241. System performance and delivery were validated through NALMCO commissioning protocols, while infection risk reduction and equivalent clean air delivery were assessed in alignment with ASHRAE 241.

Results demonstrate a significant impact of UVGI deployment, with Cardigan Ridge showing approximately an 80% reduction in infection rates compared to control facilities. These outcomes confirm the effectiveness of upper-room GUV in continuously inactivating airborne pathogens within shared spaces, complemented by HVAC-based UV-C treatment. Importantly, the intervention was implemented within existing building systems, enabling retrofit without major infrastructure modifications and avoiding the energy penalties associated with increased ventilation rates alone.

The findings highlight GUV as a robust, scalable, and energy-efficient strategy for infection control. By reducing reliance on ventilation-driven dilution and mitigating outbreak-related costs, UV technologies support a transition from reactive management to proactive environmental control, improving both economic sustainability and healthcare resilience.

Far UV air disinfection has been shown to work well against artificial test aerosols in laboratories. The limited penetration of Far-UV compared to 254 nm UV could reduce its efficacy under real-life conditions. For the rational application of this novel technology, a dose-response curve against human-generated aerosols with prevention of infection as an endpoint is essential.

Methods: Using the same South African Airborne Infections Research (AIR) facility, and the same experimental methods used to test 254 nm upper room UV efficacy. Output from 4 dimmable corner mounted Far UV fixtures were designed to achieve 3.0, 1.5, and 0.75 W/cm2 avg room fluence rates in the patient rooms, corridor, and day room. Occupant exposures are within ACGIH safety limits in this setting. A series of 8 pre-treatment TB patients were the sources of natural infectious aerosol. Immunologically naïve guinea pigs (GPs) serve as quantitative air samplers for infectious aerosol. GP infection is detected by tuberculin skin testing. One 90 guinea pig chamber receives air only on days when UV is on (intervention days) while a second identical chamber receives air on alternate control days when UV is off. RESULTS: Of 89 guinea pigs breathing air on days when room Far UV was on, only 10 became infected compared to 68 of 90 guinea pigs breathing air from the patient rooms when UV was off. After applying the standard air sampling Feller “positive hole” correction, the estimated efficacy of Far UV at approximately 3 uW/cm2 was 91%. Remaining dose levels pending.

Biofilm formation in drinking water distribution systems promotes the persistence of opportunistic pathogens and contributes to pipe corrosion and biofouling, ultimately affecting water quality and infrastructure integrity. Although ultraviolet (UV) disinfection effectively inactivates planktonic microorganisms, its effectiveness against established biofilms is limited due to shielding by extracellular polymeric substances (EPS). UV-based advanced oxidation processes (UV-AOPs), which combine UV irradiation with chemical oxidants to generate highly reactive radicals, have emerged as a promising strategy for enhanced biofilm control.

Few studies have systematically compared the effectiveness of different UV-AOP chemistries for biofilm inactivation under consistent experimental conditions. This study used a standardized experimental framework to evaluate and compare the performance of selected UV-AOPs, including UV/H₂O₂, UV/HOCl, UV/NH₂Cl, and UV-only treatment. Biofilms were cultivated under controlled hydraulic conditions using a CDC reactor to ensure reproducible growth. Established biofilms were then exposed to UV irradiation at germicidal wavelengths (254 and 280 nm), with and without oxidants at operationally relevant doses. Biofilm response was quantified using multiple indicators, including culturable cell counts (CFU), biofilm surface coverage, and EPS composition.

In addition to disinfection performance, this study evaluated the engineering feasibility of using UV-AOPs for biofilm treatment and/or prevention through a self-developed Electrical Energy per Order–Surface (EE/O-Surface) model to compare operational energy requirements across different UV-AOPs. Results from this ongoing work will provide comparative and energy-informed insights to support the evaluation and optimization of UV-AOPs for biofilm control in various water and wastewater applications.

The far-UVC field has made remarkable progress in the laboratory, yet a persistent gap remains between experimental results and the evidence base needed to drive widespread real-world adoption. This talk presents how Blueprint Biosecurity is working to bridge that gap through a coordinated portfolio of research programs designed to enable the large-scale deployment of far-UVC.

Our strategy is built around two complementary and mutually reinforcing pathways to adoption. The first is evidence-driven: we are funding and coordinating research that systematically resolves uncertainties at the intersection of efficacy and safety, producing the caliber of data — including clinical evidence of infection reduction — that bodies such as the CDC, ASHRAE, WHO, and national public health agencies need to formally recommend far-UVC and integrate it into consensus standards, regulatory frameworks, and clinical guidelines. The second is market-driven: we are supporting the organic uptake of far-UVC against endemic respiratory disease in high-burden settings such as healthcare facilities and congregate environments, where reducing infections delivers a clear return on investment. A robust commercial market in these beachhead applications attracts the sustained industry investment needed to drive down costs and increase adoption.

We describe how our active research programs serve both pathways, collectively resolving the central question of how much far-UVC is needed while addressing the principal safety concerns around ocular effects and indoor air chemistry. We close with concrete near-term milestones — including the path toward a definitive cluster-randomized trial — and a roadmap for the programs still needed to carry far-UVC to deployment at pandemic-relevant scale.

Global water scarcity is driving the need for sustainable water reuse, with treated wastewater playing a key role. However, reclaiming wastewater and greywater requires high level disinfection of human pathogenic microorganisms, including bacteria and viruses, that pose significant public health risks. This study systematically compared between different UV sources for the inactivation of Pseudomonas aeruginosa in three wastewater matrices and greywater relevant to reuse applications, evaluating damage mechanisms, post-UV repair behavior, and biofilm formation potential.

The study quantified UV fluence–response relationships, electrical energy requirements, cyclobutane pyrimidine dimer (CPD) formation, intracellular reactive oxygen species (ROS) generation, photoreactivation and dark repair, and subsequent biofilm development on reverse osmosis (RO) membrane surfaces. Complementary virus disinfection experiments evaluated MS2 and T1UV bacteriophages. Across all waters, UV222 exhibited equal or greater log reductions than UV254 or UVC LED wavelengths at comparable fluences. While UVC induced higher CPD yields, UV222 generated substantial intracellular ROS, resulting in multi-target damage that suppressed both photoreactivation and dark repair. At higher UV fluences, UV222 resulted in continued post-irradiation loss of viability. Light penetration into the water matrix strongly governed UV222 performance, with elevated nitrate and organic matter attenuating photon penetration and partially offsetting Far-UVC advantages. Nevertheless, UV222 pretreatment significantly delayed early-stage P. aeruginosa biofilm formation on RO membranes compared to UV254 and untreated controls. Thise study demonstrate that UV technology is a promising disinfection and pretreatment strategy for advanced wastewater and greywater treatment and reuse, provided that reactor design and matrix-dependent limitations are carefully addressed.

The presence of PFAS at trace levels presents significant challenges for drinking water utilities, particularly as potable reuse becomes an important water supply strategy. While the water industry has responded to the new EPA MCLs by implementing GAC, IX and reverse osmosis, these separation methods do not destroy PFAS. Vacuum UV (VUV) is known to destroy organic micropollutants through direct photolysis and reactions with radical species, and there is evidence in scientific literature indicating its potential applicability for PFAS degradation. While laboratory studies have shown promise, there are suite of technical issues that have hindered its scale-up for commercial application at flow capacities relevant to drinking water and potable reuse applications.

VUV provides an alternative for in-situ PFAS destruction, potentially overcoming issues associated with the current two-stage approach of separation, transport and disposal/destruction. However, given the high absorption by pure water at 25C, where than 90% of emitted VUV photons are absorbed within 6 mm (with absorbance in real water matrices even higher), it is important to focus on the radical chemistry responsible for PFAS defluorination. Other key issues of implementation, considering a focus on reductive radical formation, include preferential formation of advanced oxidants under circumneutral pH, and issues of UV scaling in waters at high pH. These technical issues are not insurmountable.

The ability to overcome interactions among reactive species, PFAS, and water matrix is critical to treatment efficacy and efficiency. Thus, this project investigates an innovative VUV system for destruction of PFAS, by optimizing water quality through pretreatment and reactor operating conditions to advance towards a commercially viable system. Results of treatment of PFAS contaminated groundwater in a “first generation system” will be provided; these results have informed the evolution of the concept that overcomes technical issues associated with lamp fouling while promoting formation of hydrated electrons by low-cost pretreatment using dissolved gas management. Building on early demonstrated success of groundwater treatment, additional studies are conducted on membrane reject streams from groundwater sources and potable reuse schemes that include a range of nanofiltration and reverse osmosis treatment. In addition to test results, a conceptual cost estimate will be provided to assess potential sustainability of this novel VUV treatment process as an integrated solution within treatment trains to explore questions about whether VUV is best implemented in mainstream treatment or concentrated side streams.

Far-UVC germicidal lighting has emerged as one of the most promising tools for reducing airborne pathogen transmission in occupied spaces, with growing evidence for rapid inactivation of respiratory viruses at exposure levels currently considered safe for unprotected human skin and eyes. However, commercial 222 nm KrCl excimer luminaires remain prohibitively expensive for many academic groups, public-health programs, and community organizations that would benefit most from deployment and field study.

Aerolamp addresses this barrier by manufacturing and distributing hardware derived from the OSLUV OpenLuminaire Project (github.com/OSLUV), a CERN-OHL-S-licensed open-source far-UVC platform. All hardware schematics, firmware, optical performance data, and bills of materials are publicly available, allowing independent verification of performance claims, cross-laboratory reproducibility, and community-driven improvement of the design.

The Aerolamp DevKit is offered at cost to academic researchers and at an accessible price point to community members, schools, congregations, and small businesses. The platform is intentionally modular: the same lamp assembly can be deployed as a portable unit for pop-up event installations and short-term exposure studies, or integrated into permanent wall- and ceiling-mounted fixtures for ongoing institutional use. The open-hardware approach enables custom integrations — optical accessories, sensor-based dose monitoring, networked control — without the licensing or supply-chain dependencies typical of proprietary far-UVC products.

This presentation will introduce the Aerolamp DevKit and its OSLUV lineage, describe deployment patterns observed across research and community settings, and invite IUVA members to collaborate on, modify, and extend the design. We hope to lower the barrier between far-UVC research and real-world implementation.

Presenting operational data from a groundbreaking full-scale UV-C LED wastewater installation in the UK, treating over 600 m3/h (~4 MGD). Transitioning away from mercury vapor lamps, this pioneering UK facility represents a massive leap forward for sustainable utility infrastructure. This presentation will provide comprehensive project design specifications, alongside performance results demonstrating consistent pathogen inactivation under variable flow rate conditions. Ultimately, this landmark project establishes a new global benchmark, proving in a real-world case study that mercury-free, low maintenance UV-LED technology is fully viable at the largest scale for municipal wastewater treatment infrastructure.

Advanced reduction processes (ARPs) have gained significant traction over the past two decades for treating recalcitrant drinking water contaminants. Nitrate and per- and polyfluoroalkyl substances (PFAS) are two ubiquitous pollutants that resist conventional treatment and face increasingly stringent regulatory limits. This work evaluated their degradative behavior under reducing conditions (sulfite-amended systems) using two UV LED configurations: a bench-scale 254 nm batch reactor for PFAS and a novel high-intensity 275 nm continuous-flow reactor for nitrate. Experiments were conducted in pure water matrices at fluences up to 10,000 mJ/cm². PFAS degradation varied substantially across subclasses, reaching up to ~60% removal, with short-chain species exhibiting higher persistence relative to long-chain counterparts. For nitrate, 275 nm photolysis yielded nitrite as the primary stable product, with yields governed by fluence, operational parameters, and radical scavenger activity. Scavenger experiments resolved two competing influences: hydroxyl radical re-oxidises a fraction of the nitrite formed and hydrated electrons generated under ARP conditions significantly accelerate nitrate-to-nitrite conversion. This accelerated conversion introduces a critical secondary compliance risk for water utilities treating nitrate-bearing waters, as nitrite is subject to strict regulatory thresholds. Collectively, these findings establish UV LED performance for both PFAS destruction and nitrate transformation, providing mechanistic insights critical for municipal drinking water treatment.

Far-UVC irradiation has proven to be an efficient technique for inactivating viruses, successfully destroying their nucleic acids while posing little risk to mammalian tissues. This study evaluates the effectiveness of a 235 nm Far-UVC LED Proximity Module in inactivating two strains of avian influenza H5N1 — A/Indonesia/5/2005 WT and A/Texas/37/2024 genotype b3.13 — under controlled laboratory conditions. The aim was to quantify the reduction in viral infectivity following brief, defined exposure intervals.

1 mL of viral suspension was placed in the center of a six-well plate and irradiated at a fixed distance of 10 cm for 20, 40 or 90 seconds. After irradiation, each treated sample was subjected to 1-log₁₀ serial dilutions and inoculated onto MDCK cell monolayers. The plates were then incubated for five days at 37 °C in a 5% CO₂ environment. Residual infectivity was evaluated using the TCID₅₀ method based on observation of cytopathic effects and colorimetric analysis. Log₁₀ reductions were calculated using the Spearman–Kärber technique.

The device demonstrated a notable time-dependent antiviral effect. Log₁₀ reductions of 3.39, 4.66 and 6.54 were observed for the A/Indonesia strain after 20, 40 and 90 seconds, respectively. The A/Texas strain exhibited reductions of 4.15, 5.16 and 6.17 log₁₀ under the same exposure conditions. This study confirms the device's strong virucidal effectiveness, with significant inactivation achieved over short exposure periods.

In conclusion, the 235 nm Far-UVC LED Proximity Module achieved rapid and substantial reductions in the infectivity of both examined H5N1 strains. These results validate its potential application in biosafety and infection control settings that require the efficient reduction of viral loads in liquid suspensions.

UV LED systems have been proven effective across a range of use cases in water treatment. Their chemical-free nature makes them particularly suited to sensitive applications such as food production systems. 17beta-estradiol (17B-E2) is currently being evaluated as a feed supplement for use in Canadian eel aquaculture. Its use results in the presence of 17B-E2 and its metabolites (estrone (E1) and estriol (E3)) in aquaculture waste streams which require appropriate treatment to minimize potential environmental impacts from discharge water. Traditional estrogen treatment strategies (e.g., advanced oxidation, separation technologies) require the use of added chemicals and/or produce a secondary waste stream, making them suboptimal for use in food-fish production. UV LEDs represent a particularly promising technology for aquaculture as they are inherently chemical-free and thus pose no risk to fish from either lamp breakage (as is the case for conventional lamps) or added chemicals. Here, we discuss the potential of UV LEDs for dual-use disinfection and contaminant destruction within estrogen-containing recirculating aquaculture systems (RAS). Integration of UV LED treatment into RAS could enable simultaneous water disinfection and estrogen mitigation, supporting the development of safer and more sustainable aquaculture practices while minimizing the environmental impacts associated with estrogen-containing waste streams.

Musqueam and Cutthroat Creeks (the Creeks) are important to the Musqueam people for traditional, cultural and recreational reasons. Water quality monitoring activities have been conducted by the Musqueam Indian Band and the City of Vancouver (CoV) since being closed to human use in 2019. Elevated levels of bacterial contaminants (up to 105 CFU/mL) have been found in the Creeks, particularly E. coli. The investigations have indicated that discharge from one of the CoV’s storm sewer outfalls is likely one of multiple sources of this contamination. We believe that the elevated E. coli concentrations at the storm sewer outfall are likely resulting from a combination of sanitary sewer leaks or cross-connections, and surface microbial contaminants washed into the sewer system after rainfall events. Addressing this requires decentralized stormwater treatment. While our literature reviews identify UV LED technology as a top performer with high log removal rates of E. coli, its dependence on an external power source remains a deployment challenge. We are eager to explore the implementation of a decentralized UV-LED system in this project. We invite manufacturers to design an in-pipe solution capable of treating up to 48 L/s with minimal disruption to the flow. Ideally, the system should feature the option to be powered off-grid (e.g., via solar power) and be retrofittable through standard maintenance holes. Reducing the E. coli contamination will return the Creeks to a state which they can be used by the Musqueam people for traditional and cultural activities. This research will further explore applications of decentralized UV-LED systems for the microbial treatment of stormwater.

Ultraviolet light-emitting diodes (UV LEDs) are increasingly used in water treatment, while their application to chemical degradation has emerged more recently. Conventional bench-scale UV set-ups use open Petri-dish configurations and fluence approaches developed for short-duration, quasi-collimated irradiation conditions. These configurations can become limiting for photostable chemical contaminants requiring high fluences, extended irradiation, and near-field operation, as non-collimated irradiation and sample loss may affect fluence determination and degradation kinetics. Here, we evaluate the limitations of traditional bench-scale UV setups for long-exposure UV LED experiments and discuss the potential for alternative bench-scale reactor design. In a case study using estrone, 17α-ethinylestradiol, and caffeine irradiated with a 235 nm multi-chip UV LED source, we demonstrate that accounting for non-collimated irradiation (not accounted for in most bench-scale UV setups) changed the estimated average fluence rate by up to 16%, while sample-loss correction altered fluence-based degradation rate constants by 2.3–98.9%, with greater effects associated with longer exposures (i.e., increased sample loss). These findings motivate reactor designs that reduce reliance on such corrections. A closed, short-path reactor coupled with a well-characterized, high-density UV LED array could reduce sample loss and exposure time while limiting effects of beam divergence and sample absorbance. Closed systems may also improve containment and facilitate easier study design for volatile or hazardous contaminants. Future chemical UV LED research should therefore prioritize reactor designs that improve the reliability and efficiency of bench-scale degradation studies.

Respiratory infectious diseases, emerging viral threats, and antimicrobial-resistant microorganisms continue to expose critical limitations in traditional environmental hygiene practices, particularly in occupied shared spaces where microbial transmission often occur. Existing conventional ultraviolet germicidal irradiation (UVGI) technologies require unoccupied environments due to photobiological safety constraints, limiting operational flexibility and preventing continuous environmental decontamination in populated settings. Recent research utilizing 222 nm irradiation from KrCl lamps has demonstrated safe operation around humans while maintaining high efficacy against airborne respiratory pathogens, enabling UV disinfection in occupied spaces.

This project evaluated a patent-pending Far-UVC system engineered to continuously reduce airborne and surface-borne microbial contamination in occupied environments using filtered Far-UVC technology. Research findings demonstrated equivalent rapid inactivation of airborne viruses such as SARS-CoV-2, influenza, and tuberculosis, using a virus surrogate, while maintaining compatibility with safe operations in occupied-spaces. Three testing phases were conducted to optimize system performance and operational efficiency: irradiance distribution and emission spectrum characterization, surface disinfection across complex geometries with T1 phage virus, and bioaerosol chamber efficacy testing utilizing MS2 coliphage. Results from these studies were utilized toward system engineering and performance optimization of a new product, SURYA II™, a UV222 nm robot designed for use in high disease-burden environments.

The vision for this product integrates portable mobility, advanced algorithms, sensing capabilities, remote operation, and strategically engineered Far-UVC delivery to address persistent barriers associated with conventional UV disinfection systems and fixed-solution systems, including operational downtime, workflow disruption, shadowing, and the inability to support continuous disinfection in occupied-spaces. The ultimate design incorporates twelve Far-UVC modules for multidirectional irradiance distribution, adaptive operational controls, multiple safety features, real-time system monitoring, and targeted-area deployment to enhance environmental hygiene across high-traffic public settings.

This presentation will present the research results, engineering optimization, and translational development of an advanced UV-enabled technology for public health protection.

Trace organic contaminants (TrOCs) pose a significant economic and technical challenge for potable reuse, often requiring energy-intensive advanced treatment. This research investigates whether wavelength-tailored UV-LED technology can optimize Ultraviolet Advanced Oxidation Processes (UV/AOP), specifically using a novel combination, UVLED/Cl2, comparing against conventional LPUV/H2O2 in carbon-based advanced treatment (CBAT) trains.

The study utilizes a novel 282 nm UV-LED reactor housed in a DPR mobile demonstration pilot research trailer to evaluate performance. Unlike conventional systems, the UVLEDs, specifically peaking at 282 nm, align more effectively with the absorption characteristics of free chlorine at neutral to basic pH. This alignment potentially accelerates photolysis rates and may enhance the production of hydroxyl radicals and reactive chlorine species (RCS), and subsequent removal of trace organic contaminants.

Removal efficiency is quantified via Electrical Energy per Order (EE/O), providing a direct comparison of the power required for unit contaminant degradation. Additionally, a kinetic model is being developed to predict the complex photochemistry of the UVLED/Cl2 process. This work investigates how wavelength-specific LEDs might improve the efficiency, cost-effectiveness, and reliability of advanced oxidation in full-scale potable reuse applications. Preliminary results demonstrate that in CBAT reuse scenarios, UVLED/Cl2 can meet 0.5-log 1,4-dioxane removal under low flows and high chlorine concentrations but does not yet outperform LPUV/H2O2.

As ultraviolet light emitting diode (UV LED) technologies for water disinfection become more widely adopted and continue to improve in efficiency, there is an increasing need to validate and accurately assess the efficacy and effectiveness of decentralized water treatment systems. UV field validation methods rely on indicator organisms such as Escherichia coli and viral surrogates including MS2 bacteriophage that are well characterized in terms of UV dose response behavior. MS2 is the widely accepted surrogate for enteric viruses but it requires specialized virology expertise, ongoing host culture maintenance and adherence to biosafety protocols. These requirements can pose as significant barriers particularly in limited resource field-based validation, where logistical constraints can pose a challenge in implementation. This study explores traditional baker’s yeast as a potential surrogate for UV LED dose validation for decentralized systems field measurements, especially in low resource contexts. Previous studies have shown that yeast has thicker walls and is more resistant to UV light, prompting its use as a conservative benchmark. Additionally, yeast is a low-cost, non-pathogenic, and food-safe organism that is widely available and easy to culture. This research will focus on determining the UV dose response characteristics of yeast across different UV-C wavelengths and comparing log inactivation and inactivation kinetics with those reported for pathogens. We will evaluate whether yeast exhibits comparable or more conservative UV resistance than target pathogens, supporting its potential use as a practical surrogate for in situ validations.

Surface fouling and contamination are ever-present in the built environment and pose a risk to community health when left untreated. Limited research has been published on the effects of surface materials on inactivation; however, the potential for a ‘double-pass’ effect, meaning a reflective surface may increase inactivation by allowing the light to be redirected back through the inoculum, has been suggested. The increased inactivation on directly irradiated reflective coupons, when compared to traditional in-solution irradiation, allows for insights into the application of UV LEDs across diverse surface materials.

This study investigated inactivation of solution- and surface-suspended Escherichia coli (E. coli), Bacillus subtilis (B. subtilis) and Aspergillus brasiliensis (A. brasiliensis). Coupons were inoculated and directly irradiated using 235nm and 280nm UV LED collimated beams. In-solution suspensions of all three species were also irradiated with both wavelengths to compare with traditional experimental methods. This work expands upon earlier work which identified the impacts of material surface geometry, reflectance, and texture when using 280nm UV LED for direct irradiation.

This work identifies gaps in understanding of surface inactivation using UV LEDs and provides insights into how surface inactivation could be improved using reflective material across wavelengths.

The Center for Water Resources at Dalhousie University has worked with UV LED technologies for over a decade and over the last few years have been able to expand bench-scale work into pilot operation and the installation of large systems. This work began in 2022 in further developing the UV Auditing approach for LED systems as a tool for scoping and sizing larger systems, which at the time had very little deployment using real wastewater matrices. The development of this approach informed the installation and operation of a full-scale UV LED pilot system at the Eastern Passage Wastewater treatment facility and the development of a low-flow UV LED system in collaboration with the Atlantic First Nations Water Authority. With this work, the team found process steps such as fouling, energy requirements, cleanings and performance capabilities to be among the key learning steps of these systems. Both of these systems involved significant engineering design work to plumb and program the control systems to operate the reactors which spanned between 2023-2025. For each of these systems, there were significant learnings regarding best practices for monitoring reactor operations and how to ensure smooth installation for pilot systems in the future. Furthermore, the assessment and development of implementation techniques and model methodologies in regard to these systems are among the first and therefore introduces key operational insights.

Background: Radiochromic film-badge dosimeters are a low-cost method for measuring personal UVC exposure, but their performance in GUV settings is understudied. To address this gap, we conducted a pilot study to assess the reliability and feasibility of film-badge dosimeters for monitoring occupational UVC exposure.

Methods: UVC irradiance was measured in 3 GUV-equipped rooms using a Gigahertz X1-5 Optometer radiometer. Irradiance measurements were converted to 8-hour doses and compared to the ACGIH eye TLV for 222 nm (161 mJ/cm²) and 254 nm (6 mJ/cm²). OrthoChromic OC-1 film badges were placed on tripods at two points per room for 2.5-3.8 hours. Dosimeter readings were extrapolated to 8 hours and compared against radiometer 8-hour doses at the same points, with agreement assessed through percent difference and TLV classification. To assess their feasibility for occupational monitoring, OC-1 badges were placed on nine clinic staff during their shifts.

Results: Dosimeter doses were lower than radiometer doses (222 nm: 10-21% and 254 nm: 21-57%) at all 6 points (100%). In the 222 nm space, the instruments agreed on TLV classification at both points, but in the two 254 nm spaces, the radiometer and dosimeter disagreed at three of the four points. The greater discrepancy at 254 nm could be due to exposure levels falling near or below the film’s detection limit. No clinic staff exceeded the TLV during their shift (average dose: 1.85 mJ/cm²). Wearing dosimeter badges was feasible for occupational monitoring (less than 1-minute setup per person and minimal participant effort), but administrative burden was identified as a minor limitation.

Conclusions: Film-badge dosimetry is feasible for occupational monitoring in GUV settings, but further validation is needed, especially in 254 nm spaces where low exposure levels may fall under the detection limit.

Ultraviolet (UV254) disinfection is widely used for virus control in drinking water and water reuse and is commonly described using first-order inactivation kinetics. However, many viruses deviate from log-linear behavior at higher UV doses, exhibiting tailing that can lead to inaccurate predictions of treatment performance. Although tailing has been reported across diverse viruses and experimental conditions, its occurrence has not been evaluated systematically, and objective approaches for identifying and characterizing tailing remain limited.

This study combines a systematic evaluation of published UV254 virus inactivation datasets with high-resolution laboratory experiments to better characterize viral inactivation tailing. Literature datasets were analyzed to examine the prevalence of tailing across viruses and experimental conditions. Laboratory experiments were conducted using MS2 and PhiX174 bacteriophages under multiple conditions, including infectivity and molecular assays, encapsidated and purified nucleic acids, and different water matrices. Commonly used kinetic models were compared to evaluate their ability to describe complete inactivation curves and characterize deviations from first-order behavior.

Tailing was observed across both published and experimental datasets, although its onset and magnitude varied among viruses and experimental conditions. Experimental datasets showed differences in tailing behavior between infectivity and molecular measurements, while similar trends were observed across water matrices after accounting for UV attenuation. Together, these findings provide a more consistent basis for evaluating UV254 inactivation tailing and improving prediction of viral disinfection under high-dose treatment conditions.