Please meet with our poster presenters during the breaks on Monday and Tuesday.
Contamination of mobile devices is an often under-appreciated source of healthcare-acquired infections (HAIs) in the hospital environment. Mobile devices often cannot stand up to hospital grade disinfectants without damage, but many traditional UV-C sources have the potential to damage microelectronic devices through degraded polymeric materials or etched screen glass. To avoid these issues , we present a UV-C LED cabinet system with well-characterized dosimetry and efficacy for 6 microorganisms at different disinfection cycle times in vitro, with discussion of biological testing methodology and further implications for healthcare.
In this study, we attempted to evaluate the feasibility of using ultraviolet (UV) light emitting diodes (LEDs) for the disinfection of municipal wastewater effluent. Multiple wavelength UV-LEDs, organic reflective materials, and innovative hydraulic designs for better performance of UV disinfection were employed. The on-site evaluation was conducted over 6 months using secondary treated wastewater from a local wastewater treatment plant in Seoul, Korea. The UV transmittance of the wastewater was constant (83±1%) during the evaluation period. Modularized UV-LED plates and custom reactors were designed and constructed. The active power draw required for UV-LEDs was 107 W, and the operating flow rate varied up to 100 m3/d. A dramatically improved performance was achieved with patented devices and designs for the UV-LED water treatment systems. Our results show a robust inactivation of total coliforms by 97‒99%, which successfully complies with discharge permit standards of 1,000 CFU/mL total coliforms in the effluent. The calculated energy consumption of UV-LEDs in the on-site evaluation was 0.025 kWh/m3, which was comparable to the lowest value of conventional low‐pressure lamps (0.026 to 0.066 kWh/m3) and was much lower than that of medium-pressure lamps (0.122 to 0.148 kWh/m3). Our observation reveals the high adaptability of UV-LEDs as a game changer for compliance with bio-stability goals. The results with practical applications provide information that will be useful to the water and wastewater industries and for practitioners in UV disinfection science and engineering.
For decades, ultraviolet disinfection has been used to treat water and wastewater effluents. Given the emergence of light-emitting diodes (LED) technology, there is an opportunity to further explore the parameters that govern bacterial repair methods after UV disinfection. Previous studies highlight the significance of disinfection conditions and attempt to model bacterial behavior according to disinfection dosing parameters. However, it is necessary to consider post-disinfection conditions to model the regrowth patterns of bacterial organisms more accurately. By varying dissolved organic matter content as well as reactivation wavelengths, and their respective intensities, experiments using Escherichia coli ATCC 15597 revealed how different parameters impact reactivation effects in E. coli. Photoreactivation outcompeted dark repair mechanisms in terms of log recovery rates, with UV395 resulting in higher log repair rates compared to UV365. The intensity of reactivation light played a role in how E. coli recovered from UV damage, with higher intensities resulting in higher regrowth rates. The dosage of UV278 for disinfection conditions also contributed significantly to the organisms’ ability to conduct photorepair mechanisms. Statistical analysis showed that there is a statistical significance in the difference between regrowth rates at the varying intensities utilized for each wavelength. Accurately characterizing the regrowth parameters reduces the chances of overestimating pathogen removal rates at wastewater treatment plants, since factoring in different effluent conditions results in more accurate modeling techniques that can help calculate actual disinfection rates.
Ultraviolet Germicidal Irradiation (UVGI) is a proven method of disinfection for both bacterial and viral pathogens. Since the acceleration of the COVID-19 pandemic caused by SARS-CoV-2, the industry has witnessed significant technological innovation and an influx of new light source technologies, devices, and disinfectant enclosures. To increase knowledge of germicidal efficacy for UV irradiation methods, a digital validation of performance can provide confidence from an accurate assessment of in-situ irradiance and dose measurements. When UV-C sources are installed in enclosures and rooms, challenges arise that should be digitally monitored to ensure germicidal efficacy is sustained. These challenges include 1) under and over-dosing due to non-uniformities of UV-C distribution, 2) poorly understood room/chamber dynamics and reflectance, 3) shadowing, and 4) sensor, material, and source degradation. Labsphere has introduced a series of smart UV-C irradiance sensors and meters for R&D and OEM applications that specifically address these issues. In this talk, we discuss our approach to reducing common errors contributing to sensor measurement uncertainty including sensor directional response, calibration, degradation, and application modeling. With a unique near cosine reception approach, these detectors include an exceptional f2 directional response making them ideal for deployment in rooms, chambers, and duct systems.
Introduction: Edible coating is a thin layer that acts as a protective coating on foods and can be infused with antimicrobial compounds to inactivate food pathogens. Gallic acid (GA), a polyphenol compound naturally present in plants, has enhanced antimicrobial efficacy after UV-C treatment. This study aims to develop an edible antimicrobial coating formulation prepared with UV-C treated GA added in chitosan solution for the inactivation of Salmonella Typhimurium.
Method: Two different treatment methods were performed. GA (0.5% w/v) was treated with UV-C for 10, 20, and 30 minutes before adding to chitosan (1.5% w/v) (in 1:1 ratio) solution in the first method. In the second method, chitosan (0.75% w/v) and GA (0.25% w/v) solution were mixed and then subjected to UV-C for 10 min, 20 min, and 30 min. Later, S. Typhimurium was incubated in coating solutions for 15 minutes, and enumeration was performed to understand the inactivation. DI water and non-UV treated solution were used as a control.
Results: UV-C treatment of both 30 minutes and 20 minutes (2.5 log reduction) resulted in a significantly higher inactivation than 10 minutes (2 log reduction) and non-UV (1.8 log reduction). In addition, in method 1, an increase in UV treatment time of GA increased the Salmonella inactivation up to 2.5 log CFU/ml. While in method 2, inactivation decreased with an increase in UV treatment time, but no significant difference was observed. However, there was no significant difference in their inactivation levels between method 1 and method 2.
Significance: This work developed an edible antimicrobial coating formulation using UV-C treated GA and chitosan that is promising to be sprayed on food surfaces to inactivate Salmonella.
The accumulation of biofilm within distribution systems is a common issue for utilities and point of use (POU) systems. Biofilms are robust, protected microbial communities which can be difficult to remove and disinfect once formed. Biofilms are composed of a variety of microorganisms and extracellular polymeric substances. Pseudomonas aeruginosa is a commonly used surrogate as it grows rapidly, and its ultraviolet (UVC) dose response is well characterized and understood. The attachment kinetics and mechanisms of biofilm formation is aided by material chemistry and texture; however, there is a knowledge gap in the understanding of the microbial properties of POU materials.
The prevention, suppression, and disinfection of biofilm growth is key in understanding distributed disinfection systems. The impacts and behaviours of POU materials under UVC at different stages of biofilm development is not well understood. This work explored eight different commonly used materials in POU systems to understand the effects of UVC exposure on Pseudomonas aeruginosa as a challenge organism to mimic natural biofilm communities. This study followed modified EPA methods for growing Pseudomonas aeruginosa in CDC biofilm reactors on 12.8mm diameter coupons of common POU materials. The capacity for biofilm growth on each material type was first quantified in the absence of UVC. Materials which showed no biofilm growth potential were omitted from the study. Suitable materials were exposed to 280nm UV LED light with fluences ranging from 10 to 40 mJ/cm2. The result of work clarifies the knowledge gaps regarding the applicability of distributed disinfection systems and helps manufacturers determine appropriate POU material types.
Critical developments must be made within rural water service delivery models in order to align with SDG 6.1: universal and equitable access to safe, affordable drinking water. To increase access to safely managed drinking water in rural areas, decentralized water treatment approaches focus either at household-level (point-of-use, PoU) or community-level (point-of-collection, PoC). A high level of adherence is required to realize positive health outcomes from water treatment, but household-level practices have low uptake and sustainability in many contexts. This study focuses, therefore, on the implementation environment of PoC water treatment, looking specifically at passive chlorination and UV systems. Both technologies reduce health risk from microbiological contaminants in drinking water; a key difference is the effectiveness of UV against robust pathogens like cryptosporidium versus the ability for chlorine residuals to provide continued protection between treatment and end use. There are also importance differences in the maintenance and financing regimes required to sustain these technologies. We use an implementation science approach to uncover the facilitators and barriers to successfully implementing decentralized water treatment in order to realize positive health outcomes and enhance climate resilience. Specifically, implementation science is becoming increasingly advantageous in filling the gap between efficacy studies (i.e. technological research) and real-world application.
Based on a synthesis of the existing research on passive chlorination and UV technologies, we have constructed a framework for assessing their respective implementation environments. Building from this framework, we interviewed more than 25 researchers and implementers who are involved in international projects to install passive chlorinator systems and UV PoC technologies in rural areas in South America, Africa and Asia. We conducted a thematic analysis of the interviews using versus coding in NVivo to understand key implementation trade-offs and compare findings across different water treatment technologies and management contexts. Our results identify key challenges and opportunities for securing local supply chains, advancing sustainable rural water service delivery models, and ensuring climate resilience. Overall, this research adds to the growing knowledge base of decentralized water treatment implementation, creating increased understanding of key challenges. Simultaneously, facilitators of water treatment are explored in order to produce policy recommendations and practical guidance for implementing PoC water treatment to increase access to safe drinking water in rural environments.
A book with the above title has been written to provide comprehensive coverage of the theory, methods, and common applications of ultraviolet (UV) radiation (expected publication October 2022, Wiley). The first segment of the book addresses the history of photochemistry and UV-based applications, fundamental principles of photochemistry and photochemical reactor theory, and the physics that govern the distribution and spectral characteristics of natural and artificial UV sources. The second segment of the book addresses experimental and numerical (computational) methods that are used to characterize and quantify the behavior of photochemical processes and photochemical reactors. The third segment addresses common and emerging applications, including disinfection of water, direct photolysis, advanced oxidation processes, advanced reduction processes, and disinfection of air and surfaces. An online, graduate-level class has also been developed for presentation of this material. The online class follows the material presented in the book. The class has been developed to target graduate students in engineering and the physical sciences who have interests related to ultraviolet photochemistry and photochemical reactors. The class is also well-suited to professionals who work in this area. The class is presented in a hybrid format with online, recorded lectures as well as real-time discussion among students in the class from all over the world. The real-time sessions are intended to bring together researchers and practitioners from a broad range of backgrounds to promote discussion about course-related materials, and more generally to address common interests among students in the class as related to UV.