Co-Authors: Delia Trifi, Jose Carlos Verduras, Javier Climent, Rosario Arnau, Pablo Carratalá, Inés Beltrán, Cristóbal Badenes, Sergio Chiva and Raúl Martínez-Cuenca
UV disinfection is the preferred technology in drinking water treatment plants given its non-formation of disinfection by-products and improved energy consumption. While, in the field of wastewater treatment, they are still not as efficient since the suspended solids absorb and scatter the UV light. Considering also that this concentration changes with time. This work was performed to optimize the commercial UV disinfection channel installed in the WWTP of Castelló, Spain. The analysis of this facility was carried out with Computational Fluid Dynamics (CFD), which is a powerful tool for evaluating the performance of UV systems. In this study, a setup combining Large Eddy Simulation for the description of turbulence and a Lagrangian unsteady model for the tracking of bacteria has been applied. The irradiation field was calculated for several absorption bands with Monte Carlo’s model. This setup was solved using Ansys CFX 2022R1.
Co-Authors: Harold Wright, Richard Joshi, Khalida Hassan
The USEPA’s Long Term 2 Enhanced Surface Water Treatment Rule states that UV systems use validated UV dose algorithms. The USEPA’s 2006 UV Disinfection Guidance Manual provides a UV validation protocol based on biodosimetry conducted using test microbes. The UVDGM states that UV dose algorithms based on Computational Fluid Dynamics (CFD) have potential as an alternate to biodosimetry. However, when the UVDGM was published, approaches for using CFD-based algorithms for UV validation were not well defined. Since then, Water Research Foundation Project 4376 has developed guidance for validating and applying CFD-based UV dose models for developing Action Spectra Correction Factors for UV systems using medium pressure (MP) UV lamps. Evoqua Water Technologies manufactures the WF series of UV reactors. The WF-125-6 UV reactor uses a 6-inch flange and one 2.5 kW MP lamp. The WF-225-8 UV reactor uses an 8-inch flange and two 2.5 kW MP lamps. Both reactors were validated per the UVDGM using biodosimetry. Evoqua also manufacturers the WF-215-6 reactor. The WF-215-6 reactor uses a 6-inch flange and two 1.5 kW MP lamps. With this work, CFD-based UV dose models were used to develop UV dose algorithms for a WF-215-6 reactor. The CFD-based UV dose models were validated by showing that the model, calibrated by comparison of measured and predicted UV sensor readings, accurately predicted log inactivation measured with the WF-125-6 and WF-225-8 reactors. The validated model was then used to simulate a validation data set of log inactivation as a function of flow, UV transmittance and lamp output for the WF-215-6 reactor. The simulated dataset was analyzed to define UV dose algorithms that can be used to design and operate the WF-215-6 reactor. Algorithms that do not use UVT as an input and include the validation factors were developed that directly predicted the validated dose for pathogen inactivation.
Co-Authors: Mahyar Mohaghegh Montazeri, Milad Raeiszadeh, Fariborz Taghipour
Microplasma UV lamps are one of the latest viable excimer-based sources of UV radiation, which received significant attention during the COVID-19 pandemic especially due to their ability to emit human-safe far-UVC (200–240 nm) spectrums. The novel reactor concepts for the implementation of microplasma UV lamps must be designed specifically based on the characteristics of these lamps, and an accurate model to simulate the radiation profile of microplasma UV lamps is of paramount importance to develop efficient reactor systems. Therefore, we developed a 3D numerical model of microplasma UV lamps using the ray optics method and evaluated its results with the experimental irradiance and fluence rate data measured using standard optical radiometry and actinometry, respectively. We applied the model to a fundamental analysis of radiation behavior of a commercially available lamp and suggested potential scenarios for improving the efficiency of these lamps. The model indicated that the current common lamp design can be significantly improved by mitigating the radiation loss and small modifications in the geometrical design of the microcavities resulted in up to three times higher irradiance in front of the lamp. Based on the findings of this study, several virtual design concepts were proposed, and their performances were numerically compared with that of the original design of commercial microplasma lamps. The developed model can potentially be integrated with hydrodynamic and kinetic models for the virtual prototyping of complex photoreactors for water and air treatment applications.
Co-Authors: Jennifer Pagán, Ph.D., Oliver Lawal
UV-C LED technology has sustained rapid development since its emergence in 2003, though this has not been a linear process. With nearly 2 decades of device evolution, it is possible to trace macroscopic trends in the technology, highlighting areas of focus and the factors driving them. This retrospective approach provides context for predictions of wider trends in future characteristics, performance, and pricing. Enhancements in the performance of UV-C LEDs have transitioned the technology from a future interest to a viable alternative in a range of applications. Various applications will be reviewed, including surface, air, and water disinfection. Water treatment will be discussed in depth as this is a primary function of UV-C LED applications. Both industrial and municipal applications will be reviewed and case studies will be provided to showcase the readiness of this technology in it’s current state. This presentation will provide a view of the UV-C LED device and systems market from a system manufacturer perspective and includes current deployment of the technology that may not be presently in the public sphere. The intent is to state plainly, and without hyperbole, what is visible to an active player in UV-C LED technology and to provide a point of reference for wider industry professionals and policy makers.
Co-Authors: Kyle D Rauch, Xuedongzi Jiang, Amina K Stoddart, Graham A Gagnon
Surface waters in Atlantic Canada have been experiencing the outcomes of climate change via brownification processes. Brownification causes increases in organic matter, changes in water chemistry, and can lead to drinking water treatment facilities being pushed to their design limits. Increases in organic matter necessitates the increased use of chlorine as a primary disinfectant, which in turn, causes enhanced disinfection byproduct (DBP) formation. UV LEDs can potentially alleviate this issue by providing a chemical-free disinfection treatment technology for primary disinfection. T1 phage was used as a surrogate challenge organism and 280nm UV LEDs were used as the light source. THM and HAAs samples were collected simultaneously with disinfection samples, and to the authors’ knowledge, this is the first known study which has paired DBP formation and disinfection data. UV, chlorine, UV-chlorine, and chlorine-UV sequences of disinfection were all investigated as part of this study. UV fluences of 10, 20 and 40 mJ cm-2 were used for dose response modelling of T1 in a natural water matrix. Chlorine was added in accordance with current plant conditions to mimic full-scale operations. Disinfection results indicate that 280nm UV disinfection outperforms chlorine disinfection at every observed fluence and achieved a 4-7 log reduction value for 10 and 40 mJ cm-2 respectively. Additionally, UV-chlorine sequenced disinfection was additive in terms of log reduction, whereas chlorine-UV sequenced samples indicated a synergistic effect beginning at a fluence of 40 mJ cm-2. In summary, the utilization of 280nm-based UV LED disinfection shows promise for use in full-scale facilities whose source water quality has deteriorated because of climate change. This work also highlights the importance of the natural organic matter profiles when considering UV LED disinfection for full-scale applications.
Co-Authors: James H. Davis, Rajul V. Randive
There is increasing interest in UVC LED based disinfection of water in households and dispenser systems, especially in the hotel, restaurant, and catering (HoReCa) industry, as well as in using nozzles with UVC for prevention of retrograde contamination. This study investigates if UVC disinfection at the higher flowrates required by some households as well as retrograde contamination prevention is feasible. Klaran UVC LED reactors were used in the study. Further, UVC capable nozzles were designed, prototyped, and tested for feasibility. The performance of 5 Klaran rectors fitted with two UVC LEDs after running for 500-650 hours of lifetime (end of life) against stationary phase Pseudomonas aeruginosa ATCC 15442. Water flowed through the reactor at 6 LPM (1.6 GPM) and was sampled 3 times for each reactor. Then 6 nozzles were deliberately contaminated for the study and 3 were exposed to 10 mJ/cm2 of UVC applied per given period in the nozzle chamber, and then 24 hours later a swab was taken of the nozzle and processed for quantitative analysis. The disinfection performance at 1.6 GPM was > 4 LRV (99.99%). There was a statistically significant difference in growth for the treatment nozzles compared to the control nozzles. Retrograde contamination was preventable by using the process of UVC periodic dosing. Dispensers for the household and HoReCa market where the nozzle is exposed to multiple users and the propensity of retrograde contamination. Purpose of prevention of biofilm using UVC-nozzles is to protect the 'Last Mile' while dispensing water. Thus, UVC LED water disinfection is feasible in households with the mentioned flow rate regimes, and UVC LEDs are suitable for preventing retrograde contamination.
Co-Authors: Richard Lin, Kim Shust, and Renjie Li, Carollo Engineers, Inc. Mina Abdelshehid and Frank He, Los Angeles Department of Water and Power
The Los Angeles Department of Water and Power (LADWP) is reevaluating its corrosion control strategy at the Los Angeles Aqueduct Filtration UV Plant (LAAFP-UV). The LAAFP-UV treats a blend of waters from the Los Angeles Aqueduct and the California State Water Project using fourteen, 48-inch Calgon Sentinel medium pressure UV reactors. Prior corrosion control research recommended that LADWP initiate the addition of NaOH to achieve a pH between 8.0 and 8.5 and maintain a slightly positive Langelier Saturation Index (LSI) and Calcium Carbonate Precipitation Potential (CCPP). To evaluate the impact of NaOH addition, LADWP initiated a two-phase study to evaluate the potential adverse effects on UV quartz sleeve fouling and the performance of the UV system wipers on two different blends of water. One of the UV reactors was isolated from the rest of the treatment facility and used as the test reactor. Sodium hydroxide was injected through a chemical mixing nozzle located approximately 6.5 pipe diameters upstream of the UV reactor using a side-stream injection system. The flow rate through the test train was maintained at 5 MGD. The test UV reactor had wiper brushes removed on 2 of the 5 quartz sleeves to evaluate fouling potential, while the remaining wipers were used to monitor wiper performance. Fouling was monitored in real-time using a combined aging and fouling (CAF) index defined as S/Sp, where S is the measured UV intensity and Sp a predicted sensor intensity determined from validation testing. The CAF index was calculated daily for each of the 5 UV lamps. At the end of each phase of testing, a direct measurement of the quartz sleeve fouling was made using a custom optics bench that measured quartz sleeve transmittance. This presentation will discuss the impacts of NaOH addition and water quality on fouling of quartz sleeves and the performance of the UV system wipers.
Co-Authors: Sean A. MacIsaac, Amina K. Stoddart & Graham A. Gagnon
The use of UV light as a disinfectant in wastewater treatment facilities is a well-accepted and increasingly popular option due to ease of operation and efficacy of treatment. A common limitation for UV technologies is high organic and inorganic contaminant loading in wastewater matrices reducing the UV transmittance. Reductions in transmission can reduce the efficacy of UV treatment processes. Furthermore, increased total suspended solids indicate increased particulate matter loading in a wastewater matrix which can decrease inactivation of microorganisms due to the absorption of UV radiation by the particles and physical blocking of the UV radiation. It is important to characterize such water quality parameters to understand the complex nature of wastewater matrices impact on UV inactivation performance. This work characterized wastewater matrices collected from multiple wastewater treatment facilities in Nova Scotia, Canada to understand the impacts of water quality parameters on E.coli inactivation performance. These data were paired with a bench-scale collimated beam study to quantify UV system limitations at the facility versus wastewater matrix limitations This work found that that UV audits determined that two of the plants were limited by the wastewater matrix and two plants were limited by the system operations. For the system limited facilities, it was determined that the UV systems were under design for the current flows and water qualities at the facilities. Following these findings, an audit was conducted at an additional facility to compare the efficacy of 280 nm UVLEDs to a LP system to assess if the plant matrix was suitable for UVLED treatment. Early findings show an increased efficacy from the 280 nm UVLED treatment.
Co-Authors: Christy McCarthy; Justin T. Waid
The City has been working on upgrades to aging infrastructure and expansions of water and wastewater treatment capacity. As part of these ongoing projects, Jacobs investigated the causes of decreased disinfection performance and evaluated disinfection technologies for short-term and long-term solutions. This presentation will discuss the City’s short and long-term disinfection challenges, investigation of the causes, and alternatives analyses for short and long-term solutions. Wapakoneta’s UV disinfection system has been operating since 2004. The relatively recent decrease in disinfection performance may be attributable to multiple factors, including decreased UV transmittance (UVT) in the WWTP effluent, interference with the UV process by iron salt fed for chemical phosphorus removal, UV system malfunction, UV lamp outages, and ineffective cleaning of lamp sleeves. Short-term solutions considered included source reduction, modification of the existing UV disinfection system, chlorine disinfection, and peracetic acid disinfection. This presentation will compare the pros and cons to each short-term solution and described the preferred approach for implementation.
Co-Authors: Zuzana Bohrerova, Natalie Hull
Water treatment plants are required to remove or inactivate pathogenic organisms such as Cryptosporidium and Giardia to a regulated degree. Ultraviolet (UV) disinfection efficiently inactivates the chlorine-resistant (oo)cysts, but water quality impacts how much UV light reaches the microbes for disinfection. Particles can scatter or block UV light, but they could also cause absorbance measurements to appear artificially high, leading to overdesign of an UV system. Studies have shown partial inactivation when turbidities are higher than 0.3 and 1 NTU. Three water types were collected from a drinking water treatment plant to test worst-case scenarios for UV disinfection. UV inactivation kinetics from the Geeraerd-tail model were compared to water quality characteristics affecting UV disinfection, such as turbidity, UV absorbance (measured direct and through integrating sphere), and particle size distribution. Results showed that indigenous spores in unsettled softened water had a better dose response than in unsettled flocculated water. Softened water had higher turbidity than flocculated water. The Pearson correlation coefficient between the cumulative number of flocculated particles present at a certain size range and the Geeraerd-model residual population density parameter showed that particles larger than 20 microns had a stronger effect on tailing, leading to a negative impact on UV disinfection. Particle size distribution is a better indicator for quality of UV disinfection than turbidity. Due to extreme weather events occurring more often, more frequent high turbidity events may occur. Updating turbidity regulations could be helpful for UV design for smaller utilities that are more likely to have filter upset.
Co-Authors: Natalie Hull
UV disinfection applications for remote, developing, building, and distributed water system contexts are still limited by electrical requirements. UV LEDs combined with hydropower generators provide a potential solution for disinfecting water in energy independent systems and where sufficient water pressure already exists (e.g. rainwater tanks, pressurized water supplies, hand pump systems). For the first time, hydropowered UV LED systems were constructed using AquiSense Technologies Pearl Aqua Micro units combined with 12V, 10 W output miniature turbines for between $150-$250. Microbial disinfection performance using MS2 bacteriophage as the test organism. Challenge testing was performed across various flow rates for UV LEDs powered by 12V versus hydropower supplies to compare disinfection efficacy between different power sources. The prototype hydropowered UV LEDs demonstrated a maximum of ~0.5 log10 inactivation of MS2 at flow rates of 4-5 liters per minute, or the reduction equivalent of 5 mJ/cm2 for low pressure UV lamps. Following redesign of electrical components to improve power delivery, further tests will be performed to characterize disinfection performance of the hydropowered UV LEDs using other test organisms and to optimize flow rate for disinfection and power generation. Once optimized, hydropower UV LED technology can eliminate the need for an external power supply in certain disinfection applications.
Co-Authors: Sara E. Beck
UV LEDs have shown high effectiveness in inactivation of various microbes in water. The UV LED’s unique diversity in wavelengths ranging from UV-C, UV-B, and UV-A, allow for single or combined wavelength radiation. Previous studies reported no synergy from simultaneous or sequential UV-C and UV-B, and UV-C followed by UV-A, and synergy from UV-A followed by UV-C/B irradiation on microbes in water. However, no clear ground has been reached on adopting either single UV-C or UV-A followed by UV-C irradiation; hence this work answers such a question. E. coli, Bacillus spizizenii spores and MS2 bacteriophage were used as test microbes. Meanwhile, UV-C and UV-A wavelength(s) were represented by 267 and 278, and 368 nm UV LEDs, respectively. Results showed E. coli being susceptible to the UV radiation followed by B. Spizizenii spores, then MS2, as expected. B. Spizizenii spores’ resistance to UV is attributed to the photochemistry of DNA within the spores, spore coating, and DNA repair systems. The submicroscopic, non-envelop, and protective icosahedral protein capsid make MS2 more resistant to UV. Only E. coli underwent repair after UV inactivation. The repair enzyme of B. Spizizenii spores is light-independent, hence the exposure to UV could have destroyed the enzyme. Synergistic effects were found in both E. coli and B. Spizizenii, which is attributed to the different inactivation mechanisms of UV-C and UV-A wavelengths. Single 267 nm UV-C LED showed higher inactivation efficiency. Meanwhile, single 278 nm UV-C LED showed higher efficiency in repair/regrowth suppression and electrical energy consumption. From an energy and time perspective, single UV-C is a better option than UV-A followed by UV-C LED. We believe that this finding will be beneficial in the design and implementation of UV LED systems for drinking water disinfection.
Climate change, population growth, and uneven water distribution are the leading causes of competition over water resources and poor water quality. Water sources are commonly exposed to organic pollutants as trace organic contaminants. Current water and wastewater treatment plants (WWTPs) are limited in removing and degrading persistent and emerging pollutants - and often involve energy-intensive approaches. Therefore, the water industry is challenged to develop innovative renewable energy-based technologies to reduce its carbon footprint, especially in energy-demanding technologies, while producing high-quality water. Many technologies can be used to breakdown these contaminants, such as ozonation, advanced oxidation processes (AOPs as ultra-violet (UV)/H2O2, photocatalytic membrane reactor); separation by nanofiltration and reverse osmosis or activated carbon. However, there is a lack of technologies with low energy demand for pollutant degradation and consequently polishing treatments to remove OMPs. This project demonstrates a treatment technology for removing organic micropollutants (OMPs) from wastewater effluent by a solar-UVA-photocatalytic membrane reactor. The hybrid flow system reactor combines both low-pressure membrane filtration and photocatalysis powered light-emitting diodes (LEDs) at 365 nm and further at 385 nm and 405 nm in a compact design. Novel heterogeneous nanocatalyst is coated on conductive porous substrates as metal foam using electrophoretic deposition (EPD) with low lifecycle costs and is deployed in eco-efficient processes with low energy demand to reduce the carbon footprint of conventionally energy-intensive water treatment processes. The innovative and unique aspects of this project include (a) Degradation of OMPs using solar-UVA catalytic membranes that cost-effective and eco-efficient process operation for membrane cleaning and reuse of effluent; and (b) Development and application of a new tool for evaluation of the carbon footprint over the life cycle. Our novel design with smart light recycling and reflectance achieved more than 90% reduction in micropollutants such as Carbamazepine and other OMPs. The next phase is designing a pilot-scale system that will be implemented at the largest wastewater treatment plant in Israel, together with Mekorot, the Israeli water company.
Co-Authors: Paul Westerhoff, PhD,PE,BCEE; Kelly Westerhoff; Zhe Zhao
UV-C Light Emitting Diodes (LEDs) are being widely considered in applications previously not suitable for mercury-pressure based lamps. Some of these applications involve research applications or commercial applications where UV-C light is launched from LEDs into flexible optical fibers. Applications may involve simply transmitting light through optical fibers, or side-emitting light (radially) from optical fibers. Numerous vendors offer high-OH solarized glass optical fibers suitable to transmit UV-C light for several meters with little internal lose. These optical fibers range in diameter from highly flexible fibers (0.25 to 0.5 mm in diameter) to more rigid fibers (1 to several mm in diameter). Research-grade optical fibers that side emit have been fabricated in our labs, and are near ready for commercial applications. Optical companies now have several LED drivers designed to launch UV-C light into optical fibers. This presentation will present qualitative data on amounts of transmitted and side-emitted from optical fibers UV-C light (265 to 285 nm) from five LED drivers (Prizmatix Ltd., Thorlabs, Klaran by Crystal IS, Mightex, H2Optic Insights/Aquisense), measured by the Avantes AvaSpec-2048 L radiometer. Additional measurements include thermal heat production and wavelength spectra emitted. Qualitative assessments related to device size, design, ease-of-use, and cost will also be presented. This presentation will be of interest to anyone interested in optical fiber applications related to UV-C LEDs.
Co-Authors: Maciej Slotwinski
UV air disinfection has become a hot topic over the past few years. Designing and maintaining an efficient UV air reaction chamber, however, has received very little attention. Proper design is critical to efficient pathogen reduction and overall energy consumption of the system. In this paper we will review the UV reflectivity of commonly used materials at commonly used UVC wavelengths and how different reflectivity levels can impact the performance of a disinfection reaction chamber. Since reflectivity is an additive function, dramatic increases in overall irradiance is possible with small increases in overall reflectivity at the specific wavelength. This effect (sometimes referred to the Sumpner’s principle) will be quantified in a standard chamber with different linings. Several materials will be evaluated, and their performance documented. The paper will also cover the effects of UV exposure to these materials (i.e. the effects of UV aging) and how this aging effect can impact product performance over time. It is well known that certain common materials will degrade with UV exposure - yet UV reflectivity is typically reported only in the new state. These findings will quantify the expected decrease in performance of UV reflective media after exposure to UVC energy.
Co-Authors: Mark Donhowe, John Squeri, Morgan McNeely, Laura Boczek, Hodon Ryu
Ultraviolet-light emitting diodes (UV-LEDs) are smaller, lighter, and mercury-free while providing effective water disinfection performance, which enables greater flexibility in UV reactor design for water disinfection applications. More recently, we have reported the synergistic effect of UV reflective materials to enhance an efficient UV water treatment system. These studies have led to the creation of a novel UV reactor consisting of a side-mounted UV-LED tubular device made of polytetrafluoroethylene (PTFE) which is a UV reflective material, along with a UV-LED module, which emits at 272 nm, located at the center of the tube. As the UV radiation is applied on the inner wall, the UV light is reflected at the inner surface of the PTFE tube and travels through the inside of the tube. In this study, we investigate the effect of UV reflective materials on microbial inactivation efficiency in drinking water using this side-mounted UV-LED tubular device. Specifically, the effects of length of reflective material, reflectivity of the material, and the flow rate of a feed solution are correlated with the observed E. coli inactivation efficiency. The results reveal there is a limited length of this UV reflective material contributing to the overall inactivation, because the repetitive UV reflection gradually attenuates the intensity. At a flow rate of 2 L/min tested, PTFE results in approximately 4 log credits higher of E. coli inactivation than the identical sample without any reflective material. It is also found that increasing the feed solution flow rate decreases the inactivation performance significantly, suggesting the need for determination of an optimal flow rate to maximize the inactivation efficacy of the device. Overall, the synergistic effects using a UV reflective material combined with UV-LEDs encourages further studies on the development of a low power UV-LED point-of-use device.
Co-Authors: Ulli Hansen, Simon Maus, Xiaodong Hu, Oliver Gyenge
Semiconductor light-emitting devices like DUV-LEDs are gaining increasing importance in disinfection applications. The efficiency and quality of such devices is developing quickly. Yet, the key to be able to easily employ these semiconductor devices and make efficient use of the generated light is very closely related to their packaging. Conventional packages on glass-metal or ceramic basis often have constraints in dimension, handling, light efficiency or thermal performance. Lithoglas has developed a packaging technology, that allows to integrate miniaturized mirror structures directly into the package to facilitate light extraction - enabling small outline SMD-compatible packages. The mirror materials used exhibit a very good thermal conductivity in order to dissipate heat generated by reflectivity losses quickly from the package. This contribution will show examples and advancements on the use of this technology in the field of DUV-LEDs comparing simulation of the features with actual measurements of the light extraction performance. We will focus on technology and design possibilities and limitations in mirror shape, achievable reflectivity and surface quality. Furthermore, an outlook into future work will be given.
Co-Authors: Hugo Carrisoza-Gaytan , Pedro Cortes
UV disinfection chamber, designed to disinfect objects with UV irradiation. Several designs based on mercury lamps to generate UV radiation are currently available. However, the short lifetime of mercury lamps and the proper disposal of their contaminant residues results in expensive designs. The purpose of this work is to design a portable UVC-LED disinfection cabin with the capability to disinfect the whole surface of an object. The design consists of a cabin with dimensions: 270 x 300 x 330 mm (HxWxD), containing 6 LED cards with 12 UVC-LED each strategically distributed on the inner walls of the cabin, to irradiate 360o of the object’s surface laying on quartz support. The optimal performance of LED devices requires efficient heat transfer. For this purpose, an extruded aluminum heat sink was included. A Junction Temperature (Tj) of 48 oC was calculated considering: specifications of the heat sink, thermal conductivity of the LED joint and heat-grease, air convection at 25oC, LED power at 0.61W. The thermal and electric tests showed a current of 170 mA and voltage of 32.9 DCV; the measured Tj was 50 oC. Comparing with the calculated Tj can conclude a 90% efficiency of UV radiation vs temperature. Optical analysis was performed with a spectrometer avaSpec-2048, the LEDs radiation emitted was 275nm with 70% of transmittance of the quartz support. The system can be programmed with different times of exposure accordingly the pathogens to inactivate. The germicide test on E. coli reduced 99.999% of the colony-forming units on an agarose gel.
Co-Authors: WC Seo
Violeds water reactor (VWR) could resolve problems existing in UVC LED water disinfection technology for home water purifier. Currently, a major hurdle to its implementation in water reactor is lack of UV dose in reactor surface which is far from UV LED, and heat dissipation while operation of UVC LEDs. Although more LEDs are needed inside the reactor, about 97% of electrical power consumed in reactor were transformed to heat without changing to UVC light. Smart structure and heat dissipation of reactor is important. In this presentation, we report the successful design of a water reactor using an efficient water path for both increasing UV dose and heat dissipation. Thus achieving more than 4 log reduction of Q-beta virus at 1.3 LPM water speed with VWR. Thermal and electrical characteristic of UVC LEDs were tested at the conditions of with and without proper heat dissipation method. PTFE was used for high reflectance of UVC light, and quartz window and tube were used for extending exposing time of water to UVC light. SUS ring structure was used for heat dissipation while water was flowing. Various water reactors were tested to optimize design. Finally, microbicidal effect of VWR were tested at TZW in Germany. 9 cm long VWR could disinfect virus with 9W power consumption.
Co-Authors: Pratibha Sharma, Ron Hofmann, Susan Andrews
Ultraviolet light-emitting diodes (UV LEDs) are fast becoming an attractive water treatment tool to disinfect microorganisms and treat micropollutants. Different from conventional mercury lamps, which are currently in use by many water treatment plants, LEDs are compact, mercury-free, and can be turned on and off essentially instantly so they have the potential to replace conventional UV lamps. One of the more novel applications for LEDs in water treatment is advanced oxidation, where UV light is used to split chemicals into reactive radicals that can quickly destroy pollutants in the water. Among the different advanced oxidation processes (AOPs), UV/Cl2, in particular, may be well-suited to using LEDs as the light source, as chlorine shows a high UV absorptivity at the wavelengths where certain UV LEDs produce light more efficiently than conventional mercury lamps. One of the key problems that is currently hindering a more widespread adoption of LEDs for UV/Cl2 is the absence of enough information on the relative performance of UV LEDs and mercury lamps in the context of the generation of disinfection by-products (DBPs) during micropollutant removal. In this study, the UV/Cl2 process was investigated using four light sources emitting UV at different wavelengths: low-pressure mercury lamp (254 nm); LED at 265 nm; LED at 308 nm; and medium pressure mercury lamp. Caffeine and sucralose were selected as model micropollutants to represent those that are either reactive to both ●OH and RCS (caffeine) or reactive to only ●OH (sucralose). The performance of the different light sources employed in the UV/chlorine process at equivalent “effective” doses was compared from two perspectives: (1) micropollutant degradation, and (2) chlorate formation (a major by-product of interest to practitioners). The effects of pH, water matrix, and chlorine dose were also investigated.
UV light emitting diodes (LEDs) are a novel UV technology which exhibit a compact footprint, can be engineered for specific wavelength emission, and have high potential for improvements in external quantum efficiency and lifetime. Background absorbance of wastewater-influenced waters and low molar absorption by conventional radical promoters have historically limited the efficiency of UV AOPs, allowing for the underutilization of photons in a reactor and leaving harmful residuals to quench. The absorbance of deprotonated free chlorine can be designed to synergize with 280 or 300 nm UV LED emission and optimize the utilization of photons for advanced oxidation. This research compares quantum yields of radical formation from 265, 280, and 300 nm LEDs and evaluates a kinetic model to compare hydroxyl radical and chlorine radical oxidation using Nitrobenzene and Benzoic Acid as probe compounds. pH- and wavelength-dependent reaction rate constants will be experimentally derived and evaluated to determine radical contributions. Reclaimed water, varying in TOC concentration and UV absorbance, will be treated with the UV LED AOP to investigate how photon scavengers affect radical generation and contaminant transformation kinetics. In addition, electrical energy considerations will be assessed, with steady-state radical concentrations and pseudo-first order rate constants normalized to incident photon flux for varying water qualities. This research promotes alternative UV sources in advanced oxidation processes, like LEDs, which can be utilized diversely to treat organic chemical contaminants and increase overall system efficiency
Co-Authors: Lauren Mullen, Karl G. Linden
Low-pressure UV (LPUV) lamps have been widely used advanced oxidation processes (AOPs) for treatment of organic/inorganic contaminants. Excimer lamps have existed for decades but not adopted for water treatment. Krypton Chloride (KrCl*) excimer lamps emit at 222nm which is in the far UV-C range (200-225nm) and the output is more highly absorbed by many chemical contaminants. Target contaminants degrade under UV through two pathways: 1) direct photolysis, and 2) oxidation. Carbamazepine (CBZ) was selected as a target compound. Parallel experiments were conducted under LPUV and excimer 222nm lamps to compare the efficiency of carbamazepine degradation by both oxidation and photolysis pathways. CBZ has a significantly higher absorptivity at 222nm (26422 M^(-1) cm^(-1) ) than 254nm (6419 M^(-1) cm^(-1) ) and higher quantum yield at 222nm (0.045 mol Es^(-1) ) than 254nm (0.002 mol Es^(-1) ). For direct photolysis, CBZ degradation rate was 4.33x10^(-4) cm^2 mJ^(-1) under LPUV and 9.49x10^(-5) cm^2 mJ^(-1) under excimer 222nm. For AOP (10ppm H_2 O_2 ), CBZ degradation rate was 5.24x10^(-3) cm^2 mJ^(-1) under LPUV and 2.58x10^(-2) cm^2 mJ^(-1) under excimer 222nm. To achieve 2-log removal of CBZ by direct photolysis, it would only require a UV dose of 2095 mJ cm^(-2) for excimer 222nm compared to 76,753 mJ cm^(-2) for LPUV. To achieve 2-log removal of CBZ by AOP, it would only require a UV dose of 105 mJ cm^(-2) for excimer 222nm but 1707 mJ cm^(-2) for LPUV. Excimer 222nm lamp technology can potentially significantly improve UV treatment efficiency for contaminant degradation and should be explored further for municipal application.
The study of the interaction of light with photochemical and photobiological systems requires an accurate assessment of the incident photon flux. The determination of photon fluxes for various light sources (monochromatic and polychromatic) has an inherent advantage since the use of standard quantum yields for the actinometer assures that the photon flux has been calculated against accepted standards. Alternatively, if the photon flux is known, chemical actinometry can be used to determine quantum yields. This study illustrates how incident photon fluxes and quantum yields can be estimated for photochemical and photobiological systems. First, an example is developed to calibrate a spectroradiometer using a low-pressure (LP) UV lamp using either the ferrioxalate or iodide/iodate actinometers. The Calibration Factors (CFs) (defined as the ratio between the actinometer and the spectroradiometer) agreed very well, demonstrating the consistency of quantum yields between well-researched actinometers. Second, since UV-LEDs have a bandwidth almost twice that of LP lamps, should UV-LEDs be treated as monochromatic or polychromatic light sources? Results showed no significant differences between the monochromatic analysis and the polychromatic analysis. Third, the uridine quantum yield is 0.025 ± 0.001 over the 254-279 nm wavelength range, independent of these wavelengths.
UV light can be generated by many sources, such as, arc lamps, LEDs, and electrode-less lamps. Electrode-less lamps are the only type of lamps that can produce UV using a household microwave oven. 60 million people in the US and 884 million people in the world don’t drink tap water due to fear of contamination. This research investigates a method for purifying water using UV light generated by household microwave ovens. By leveraging the synergetic effect of heat and UV to purify water, microwave energy was used to simultaneously heat water and generate UV. Two innovative flow-tubes, with integrated UV bulbs, were designed. Two 16 liters of controlled water samples, contaminated with two concentrations of E. coli (100uL and 250uL) were prepared. CFU (Colony Forming Units) counts for each water sample, after incubation at 350C for 24hrs was recorded. Using a flow pump and water pipes, each container was connected to a flow-tube kept inside the microwave oven. As the microwave oven turned on, the pump pushed contaminated water to flow through the flow-tube at rates varying between 100 ml/minute and 533 ml/minute. Water temperature and the CFU count for each water sample after exposure to microwave and UV were recorded. Zero CFU counts for 100 and 200 ml/minute indicated the effectiveness of the proposed approach to produce 8 liters of clean water in 30 minutes, adequate for a family of four, free of biological impurities.
Co-Authors: Pratibha Sharma
While UVLEDs have drawn significant attention over the past few years, lower optical outputs and shorter lifetimes can pose challenges for their adoption. Novel thermal technologies play an important role in addressing UVLED performance issues, specifically for high-power applications. Higher junction temperatures reduce device lifetimes and present a challenge for development of integrable and affordable thermal solutions.
Packaging technologies for manufacturing UVLEDs can differ significantly and hence the range of performance can be very broad. While many UVLED SMDs on the market today utilize ceramic substrates, others utilize aluminum or copper-based materials to further boost performance, reliability, and heat dissipation abilities. In this work, we look at the impact of packaging structures on thermal performance. We present an advanced integrated thermal management technology (3-PAD) which maximizes heat extraction at the chip and package level with a direct, low thermal resistance path from the LED junction. This allows for an increase in optical output (>50%) and LED lifetimes (>4000 hrs) at high driving currents (>700mA/1.2x1.2mm chip), without increasing the thermal budget. We present comparative thermal modeling results, substantiated through experimental validation, for four different UVC LED structures. Measured junction temperature and relative radiant flux results obtained using the traditional and advanced packaging technologies will be compared to demonstrate the benefit of using advanced thermal management methods. Optical output degradation results will be presented for the first 100 hours of operation for each of these packages. These results can be used to determine device performance and lifetimes for optimal product design.
Co-Authors: Manabu ICHIKAWA , Shigeru ANDO
In May 2019, Japan's Ministry of Health, Labour and Welfare (MHLW) revised its “Guidelines for Cryptosporidium Prevention and Control in Water Supply”. The revision aimed to designate UV disinfection as a preventive measure against Cryptosporidium contamination in the high-risk treatment facilities using surface water sources. The decision to revise the Guidelines was mostly prompted by a research project with a government grant conducted by the Japan Water Research Center (JWRC) with academic researchers that had confirmed that a combined use of filtration and UV disinfection is a more reliable and effective measure against potential Cryptosporidium contamination. Following the revision of the Guidelines, JWRC published in April 2021 the ""Guidance Manual for Introduction and Maintenance of UV Treatment Facilities in Water Supply"" with UV-LEDs included. The manual gives explanations on the characteristics and current technical status of UV irradiation, as well as provides examples of its actual use at water utilities. According to a JWRC’s survey to manufacturers of UV treatment equipment, the number of UV treatment facilities in operation in Japan has been increasing every year, with 425 facilities now in service as of the end of March 2021. More than half of them are small-scale facilities treating less than 1,000 m3 per day, but the use of UV disinfection for surface water treatment is expected to increase.
Co-Authors: Alexander Wilm
LEDs have inherent advantages over UV-C lamps, such as size and instant on/off switching, enabling them to be used in new water disinfection applications. They are also well positioned to replace lamps in existing applications over time. This presentation will discuss the current state of UV-C LED and sensor technology, and the roadmap for the next few years. Several use cases will be presented showing how LEDs can be used in new ways which are not possible with lamps. Additional cases will show how LEDs could be used to replace lamps today and in the near future. Integration of UV-C sensors into these applications will be shown throughout.
Co-Authors: Dan Scharpf, Lorne Loudin
To increase knowledge of germicidal efficacy for UV irradiation methods, a digital validation and records of performance can provide confidence from an accurate assessment of in-situ irradiance and dose measurements. Labsphere has introduced a series of UV-C irradiance sensors and meters for R&D and OEM that specifically address issues associated with poor sensor design and form factors. In this talk, we introduce our SMARTSens solutions. SMARTSens is a series of tethered and integrated UV radiometers, connected and wireless, with a powerful software package for analytics and simple dashboard creation. We’ll discuss our approach to reducing common uncertainties errors contributing to sensor measurement errors as well as use cases and case studies.
1. Carollo Engineers, Boise, ID
2. Las Virgenes Municipal Water District, Calabasas, CA
The Las Virgenes - Triunfo Joint Powers Authority (JPA) Pure Water Demonstration Project is evaluating UV/chlorine AOP as part of an advanced treatment train for surface water augmentation. The UV reactor is a Xylem Spektron 30E sized to deliver a UV dose of 600 mJ/cm2 for NDMA reduction at 20 gpm. Sodium hypochlorite is added upstream of the reactor 0.5-log reduction of 1,4-dioxane. Online instrumentation includes free and total chlorine, UVT, and pH. These parameters and monochloramine were also measured at bench. The evaluation included quantifying UV dose delivery by the reactor using dosimetry and measuring the reduction of spiked NDMA and 1,4-dioxane.
Grab and online UVT was compared to values calculated using measured chlorine species and their extinction coefficients at 254 nm. Dichloramine was calculated as the difference between total chlorine and the sum of free chlorine and monochloramine. The calculated UVTs agreed very well with the measured values, with better agreement using the online measurements. The analysis showed the importance of analyzing RO permeate samples immediately after they are collected, because RO permeate water chemistry is dynamic. The ratio of monochloramine to total chloramine at the UV reactor inlet was highly pH dependent with less dichloramine at lower pH. This was unexpected given the pH dependence of chloramine equilibrium. This observation has important implications for controlling NDMA reformation with downstream water stabilization.
The pseudo-steady state model for UV AOP was used to predict the reduction of free chlorine, mono- and dichloramine, the increase in UVT, and the reduction of 1,4-dioxane. 1,4-dioxane reduction was predicted with a slope of 0.9 and an R-squared of 0.996. The model can be used to optimize the required UV and chlorine dose required to meet the 0.5 log reduction of 1,4-dixoane as mono and dichloramine levels fluctuate at the UV inlet.
1. Brown and Caldwell
2. Civil & Mineral Engineering, University of Toronto, Ontario, Canada
Ultraviolet (UV)-chlorine advanced oxidation processes (UV/Cl-AOP) are gaining interest, particularly in potable reuse applications but also potentially in conventional drinking water treatment for control of taste and odor and other regulated and emerging contaminants such as 1,4-dioxane. While UV/Cl is similar to the more conventional UV/hydrogen peroxide (H2O2) AOP, there are differences that deserve attention related to implementation. These factors include different optimum water quality conditions, different efficiencies when using low-pressure high-output (LPHO) and medium-pressure (MP) UV lamps, and the potential formation of by-products. Design and implementation challenges are also different than that of hydrogen peroxide. Monitoring, water quality impacts and potential byproducts are different and more complex.
The information that exists on UV/Cl is still mostly scattered throughout the research literature or present only in lessons learn from staff at utilities that have implemented this technology. This makes it difficult for end users to identify key issues that must be addressed if considering UV/Cl, and the important questions to ask of the UV manufacturers. The goal of WRF 5050 is to consolidate information about the state of the art of UV/Cl AOP in a single reference, ideally with the information formatted such that it is appropriate for utilities, non-expert consultants, and regulators. The project is developing a guidance manual summarizing the basic science, as well as highlight practical issues related to the implementation and operation of UV/Cl-AOP. It will also compare and contrast UV/chlorine-AOP to alternative AOPs in the context of both RO- and ozone/biofiltration-based reuse treatment trains. The project will also highlight current knowledge about by-product formation, and will include experiments to fill DBP data gaps and explore critical areas of unknowns (e.g., unregulated DBPs, and overall toxicity assessment).
The Village of Ossining experienced an unprecedented taste and odor (T&O) event related to 2-Methylisoborneol (MIB) in their primary supply December 2019 through April 2020. As a result of this event, the Village requested additional treatment be added to the recently completed design of a new Indian Brook Water Treatment Plant (IBWTP). To address this new water quality challenge the design team evaluated options to modify the design of the proposed IBWTP to incorporate an Ultraviolet Light (UV) Advanced Oxidation Process (AOP) system (in lieu of the UV Disinfection system) to control MIB if a future event is experienced. In addition to the UV AOP system, the Village intends to include a new powdered activated carbon system (PAC) near the existing Low Lift Pumping Station to control the full magnitude of a potential T&O event.
Hazen collaborated with the University of Toronto to study peroxide and UV doses. The University of Toronto’s work included the following objectives:
The results of this study were used to establish the design criteria for the IBWTP modifications.
1. Chemical Engineering and Applied Chemistry, University of Toronto, Ontario, Canada
2. Civil & Mineral Engineering, University of Toronto, Ontario, Canada
3. Brown and Caldwell
As an essential part of the water reuse treatment process, ultraviolet (UV) advanced oxidation processes (AOPs) utilize UV light and oxidants to decompose contaminants that can pass through the upstream reverse osmosis (RO). For a specific treatment goal, manufacturer(s) or vendor(s) would recommend a UV reactor system design for specified flow conditions. However, it is necessary for the utility to verify the accuracy of the recommended design. In 2021, a field testing study of a pilot-scale reuse system was performed with a UV reactor. The field testing study was conducted by spiking five chemicals into the flow of the pilot-scale reuse system to test their destructions across a UV/H2O2 treatment process. Information on the background water quality, the operating conditions, and the log reductions of five compounds were collected and then analytically analyzed. This work aims to: 1) demonstrate the importance of field testing and highlight the potential RED bias effect; 2) comment on the use of surrogate compounds to predict the log reduction of micropollutants. A thorough analysis was carried out by extracting the information (e.g., the scavenging capacity) from the spiking study results. The limitation of field validation was then addressed, and the benefits and considerations for CFD in reactor validation were proposed.
UV advanced oxidation processes (AOPs) have proven to provide an effective treatment barrier for various recalcitrant contaminants in potable reuse and drinking water applications. A vast amount of experience and knowledge has been gained from the design and operation of existing systems, which continues to further the advancement of UV AOP technologies and the procedures used for their design and operation. This has resulted in a continuously evolving environment as design approaches, control strategies and regulatory requirements are constantly are in a constant state of flux. While encouraging and exciting, the design and implementation of UV AOP systems can be a challenging task in an ever-changing landscape. This is further complicated by a lack of standardized guidance for UV AOP applications resulting in a 'wild-west' atmosphere where various techniques are used by manufacturers for the design and operation of these systems, the details of which are typically not disclosed resulting in a black box approach with little transparency that is in stark contrast to the validated approaches used for drinking water UV disinfection applications. The lack of an industry standard with regards to dose requirements, water quality considerations and testing protocols further complicates the landscape. The cumulative result of these challenges is a landscape that can be difficult to navigate for engineers, utilities, and regulators with significant potential for increased uncertainty and risk for UV AOP applications. Case studies will be presented for several UV AOP installations designed over the past few years, reviewing the advancements and the challenges associated with design of these systems in a continuously evolving environment. In addition, these case studies will demonstrate the challenges associated with a lack of industry standards and highlight the need for the industry to develop standardized guidance for the design, operation, and validation of UV AOP systems.