Wentao Li, RCEES, Chinese Academy of Sciences (CAS)
Authors: Wentao Li, Mengkai Li, Zhimin Qiang
11:00-11:20 AM

Ultraviolet (UV) based advanced oxidation processes have been widely investigated and evaluated for micropollutant removal in water and wastewater treatment. Among them, setting up a kinetic model that can predict accurately the process efficiency in practical application is critical. Previous studies on micropollutant removal kinetic modeling were mainly conducted with lab-scale batch UV reactors, employing the pseudo-steady-state (PSS) approximation that assuming a steady state concentration of radicals, and only a few were conducted with closed conduit UV reactors using computational fluid dynamics (CFD) simulation. In this study, the atrazine (ATZ) removal in a closed conduit UV reactor (L-shape, mono-lamp) by UV/H2O2 and UV/persulfate processes, respectively, were analyzed with both PSS and CFD models. The effects of influent water matrix (e.g., dissolved organic matter (DOM) and alkalinity) and flow rate on ATZ removal efficiency were evaluated. Results show that the PSS model predicted identical results for the UV/H2O2 process as compared to the CFD model, but underestimated the UV/persulfate efficiency significantly. This indicates that the UV/persulfate process in the closed conduit UV reactor, which had complex radical-involving reactions together with a non-ideal-mixing flow, could not be well accounted for by the PSS model. In fact, the UV/persulfate reactor had heterogeneous radical concentrations along the UV lamp as evidenced by the CFD simulation. The UV/persulfate process was manifested to be more efficient in ATZ removal, accounting for that 0.1 mM persulfate achieved a higher removal efficiency than 0.5 mM H2O2 (84.2% vs 74.6%). The DOM concentration had a significant impact on the ATZ removal efficiency for both processes while the influence of alkalinity was minor. This ongoing study is the first report on CFD modeling of UV/persulfate process based on the authors’ knowledge, and more results on model verification and analysis will be obtained soon.

Shannon Roback, CSUDH
Authors: Shannon Roback, Ken Ishida, Megan H. Plumlee, Yi-Hsueh Chuang, Zhong Zhang, William Mitch
11:20-11:50 AM

N-nitrosodimethylamine (NDMA) is a disinfection byproduct of public health concern in potable waters. It is well removed by UV treatment due to its absorption bands at 230 and 330 nm. However, NDMA precursors comprise a diverse range of organic compounds some of which may not be photo-sensitive. UV/advanced oxidation process (AOP) pilot tests were conducted at an advanced water treatment facility that treats municipal secondary effluent for potable reuse. Sodium hypochlorite (NaOCl), monochloramine (NH2Cl) and hydrogen peroxide (H2O2) were dosed into reverse osmosis (RO) permeate prior to entry into a UV/AOP pilot reactor with an approximate UV dose of 800–900 mJ/cm2. Residual oxidant concentrations of 1 or 4 mg/L as Cl2 NaOCl and 3 or 6 mg/L as Cl2 NH2Cl and H2O2 were investigated. Resultant destruction of NDMA and NDMA precursors was evaluated. NDMA was removed below the 1.2 ng/L detection limit by both doses of H2O2 and NH2Cl, as well as by UV with no oxidant addition. However, NDMA destruction by UV/AOP was suppressed by the 4 mg/L free chlorine to only 87% removal, and to a lesser extent by the 1 mg/L free chlorine to 95% removal. Precursor removal was less efficient with only 7% of NDMA precursors removed by UV alone, 58% and 30% by UV/H2O2 (3 mg/L and 6 mg/L, respectively) and 61% and 48% by UV/NH2Cl (3 mg/L and 6 mg/L, respectively). Suppressed removal at higher dosing of these two oxidants suggests that scavenging may reduce the degradation rate of NDMA precursors. Four mg/L free chlorine addition removed all NDMA precursors prior to exposure to UV light, highlighting its effectiveness in NDMA precursor destruction. Post-UV/AOP, there was a slight increase in NDMA precursors suggesting possible formation by UV/free chlorine, to be confirmed in future studies.

Salvador Dominguez, Xylem
Authors: Salvador Dominguez, Slavica Hammond, Lance Thibodeaux
11:40-12:00 PM

The Terminal Island Water Reclamation Facility (TIWRF) was the first utility in the world that decided to implement the UV + Hypochlorite AOP for potable reuse in accordance with the California Ground Water Recharge Rule. (CGWRR) The design of this novel process was based on an extensive 12 month pilot period leading to the selection of an inline UV AOP reactor with a design UV dose of 920 mJ/cm² and 2-4 ppm of free chlorine prior to the irradiation chamber. As this process has not been implemented in full scale bevor the design team was challenged to develop new control philosophies and critical control points using state of the art online instruments to assure full compliance of the treatment system even under varying water qualities. To demonstrate the proper design and control of the system in full scale a 2 month performance test was set-up to deeply investigate the performance but also the impact of changing water conditions and varying chemical feed concentrations with regards to the removal of NDMA and 1,4-Dioxane which are regulated by the CGWRR. The paper will provide detailed results of the performance tests, conclusions and observation from the first year of full scale operation and next steps.

Mark Donhowe, W. L. GORE & ASSOCIATES
Authors: Mark Donhowe, John Squeri
11:00 - 11:20

UVC LEDs are gaining traction in the market for point of use (POU) water disinfection due to their advantages over UV-lamps such as small size, instant turn-on, and higher robustness. But commercially available UVC LEDs suffer from low efficiencies of less than 5% compared to the 30% efficiencies posted by low pressure mercury lamp sources. To overcome this a high efficiency reactor design is desired to achieve a reasonable system-level efficiency. An ideal high efficiency reactor would have uniform photon density or more precisely fluence rate such that no dark spots (i.e., volumes) exist. Since the minimum optical power level required to inactivate the targeted pathogens is determined by the darkest volumes within the reactor the excess power in the bright spots is “wasted” thus reducing efficiency. This is particularly problematic for UVC LED sources as lower efficiencies lead to higher heat dissipation and shorter lifetimes. To overcome this, a high efficiency UVC LED reactor was designed, modeled, and built using an integrating sphere design concept which approaches the ideal for uniform photon density. Expanded PTFE, a material used in some integrating spheres, was used for the reactor chamber walls. Reactor chambers were built and modeled with various diffuse reflectance (50 to 100%) walls. Visible LEDs, of varying far field patterns, were mounted at various LED to LED spacings along the chamber wall, to evaluate the sensitivity of the reactor design. Finally, a UVC LED reactor tube was built and a biodosimetry study was performed to validate the efficacy.

Ron Hofmann, University of Toronto
Authors: Hadas Mamane, Dana Pousty and Ron Hofmann
11:20 - 11:40

UV disinfection efficiency depends on the UV-dose, which is defined as the product of average incident irradiance (fluence rate) and exposure time, corrected by water absorbance, petri factor and reflection factor. It has been reported that the same time-dose reciprocity may not apply to microorganisms when exposed to different light intensities. Sommer et al. 1996, reported that E.coli showed higher UV inactivation when applying a high UV intensity over short exposure times. UV light-emitting diodes (LEDs) are considered as alternatives to UV mercury lamps in water treatment. These UV sources allow flexible design of reactors, and enable tuning the wavelength; require no lamp warm-up time; can be operated by intermittent flow and at ambient temperature to avoid fouling; and can use a DC voltage.

However, LED technology is currently limited to low power input and radiant flux (output). Such low irradiances might affect the expected time-dose reciprocity as described above. The goal of this research was to examine the time-dose reciprocity on E. coli using UV-LEDs at different wavelengths and irradiances, and compare the results to the time dose reciprocity in low-pressure (LP) lamps.

The following results were observed: (1) LP - high average intensity over long exposure times result in higher inactivation. (2) LED at 265 nm - no significant differences were observed between the low average intensity and the high average intensity. (3) LED at 275 nm - minor differences were observed between the low average intensity and the high average intensity. (4) LED at 295 and 285 nm - significant differences were observed - low average intensity over long exposure times resulted in higher inactivation.

The literature does not provide any explanation for the inactivation kinetic differences between the wavelengths and the intensities. Ongoing research is being conducted to examine whether metabolic mechanisms are affected differently by the different wavelengths and intensities.

Karl Linden, University of Colorado Boulder
Authors: Natalie Hull, William Herold, and Karl Linden
11:40 - 12:00

A UV LED flow-through reactor was validated for disinfection performance using MS2 coliphage as a surrogate, over a range of UV transmittance (UVT) levels and flow rates and then installed in the field at a water utility to demonstrate sustainability, robustness, and water disinfection performance over time. The reactor pilot site was at a small drinking water treatment plant, downstream of slow sand filtration. UVT in the UV reactor influent was measured daily, along with temperature, pH, and turbidity. ATP, total coliform, E. coli, and total organic carbon (TOC) were measured bi-weekly in the treatment plant influent, slow sand filter effluent, UV LED effluent, and compared to similar parameters in the chlorine effluent from a parallel disinfection train using chlorination. Disinfection performance in the field was measured by MS2 challenge testing immediately after installation, followed by quarterly measurements to monitor UV performance over time and during each season. Data on electrical and maintenance requirements were collected for life cycle sustainability analyses. Additionally, biofilm development in pipes was compared upstream and downstream of UV and chlorine disinfection processes. DNA was extracted and analyzed from biofilm that developed on 1-inch pipe sections to compare effects of each disinfection process on formation of attached microbial communities. The field challenge testing with MS2 in the small system filter effluent aligned with modeled results from the validation bench testing with MS2, indicating no detrimental effects from the water matrix in the field upon installation. The reactor was resilient and maintained bacterial and viral disinfection performance with no maintenance, and cost an estimated < $25 in electricity to treat 0.5 lpm running continuously for one year. This is the first longitudinal pilot investigation of the first commercially available flow-through UV LED disinfection reactor at a drinking water treatment plant.

Kumiko Oguma, University of Tokyo
Authors: Kumiko Oguma
12:00 - 12:20

Ultraviolet light-emitting diodes (UV-LEDs) can bring innovation to water treatment systems and broaden the application of UV-based technologies. In this study, UV-LEDs with peak emission wavelengths at 265, 280 and 300 nm were used to inactivate human pathogens including Pseudomonas aeruginosa and Legionella pneumophila which can transmit via water and healthcare facilities, Vibrio parahaemolyticus which is important in food safety and aquaculture industry, and Feline Calicivirus which is known a traditional human norovirus surrogate as well as a pathogen to felids. For comparison, indicator/surrogate species including Escherichia coli, bacteriophage Qβ, MS2 and Bacillus subtilis spores were also tested. It was indicated that, in general, the 265 nm UV-LED was most efficient among tested in the fluence-based inactivation rate constant k (cm2/mJ). Result of this study provides the k values for all species tested, which would eventually contribute to develop a database on UV-LED inactivation of various microorganisms that can serve as a fundamental knowledgebase to promote and expand UV-LED applications.

Rich Simons, AquiSense Technologies
Authors: Rich Simons, Jennifer Pagan
11:00 - 11:20 PM

Determination of reactor efficiency has been traditionally made using the EEO (electrical energy per order). This measure describes the electrical energy requirement to reduce the number of a given challenge organism by a factor of 10, per unit flow rate through a disinfection system. When considering large-scale installations, where operating costs are the main driver, this is a reasonable method and has proven utility.

However, in the developing market of low-power micro UV systems the cost of energy consumption is not a key driver and so the EEO loses impact. To a systems integrator new to UV disinfection the industry terminology around wavelength, log reduction, germicidal weighting factors, UVT, fluence/dose, etc. can be confusing and prohibitive to acceptance. A new quantitative measure is therefore required to allow for an objective comparison of UV water disinfection systems.

A method is presented for the determination of a universal efficiency factor, capable of use as a comparative measure for UV disinfection systems of different designs operating at different flow rates, wavelengths, output powers, and on different challenge organisms. This allows for an objective measure of the quality of a reactor design. This efficiency is considered against the fundamental limit for the average fluence rate for an input UV power, thus giving an absolute reference scale (0 – 100%). This fundamental limit to the average fluence rate is new to the industry literature.

Kanako Tajima, Ritsumeikan University
Authors: Naoyuki KAMIKO
11:20 - 11:40 PM

Pathogenic viruses are commonly detected from water and threatening human lives. As an alternative to usual chlorination, ultraviolet (UV) disinfection of water is attracting attention. Although experiments using various wavelength UV have been conducted, research with vacuum UV (VUV) and comparison of detection methods is limited.

Objective of this study is to compare the effect of various VUV (147 and 172 nm) and UVC (222, 254, and 282 nm) to DNA phage inactivation evaluated by infectivity (plaque assay) and DNA detection (real time PCR) to investigate the inactivation mechanisms of each wavelength.

DNA phage strain phi-X 174 was used in the experiments. For PCR detection, real time PCR system (Thermal Cycler Dice Real Time System II, Takara Bio companies) was used with the primer set to detect target sequence of 153 bp among the whole 5386 bp. Light sources used were LP lamp for 254nm and excimer lamps for other wavelengths.

Result of plaque assay showed that 172 nm was more effective than 147 nm evaluated with surface UV dose for VUV. Among the UVC light sources, 222 nm was most effective, 254 nm was less and 282 nm was the weakest for both infectivity and DNA detection as many researchers already reported. Log DNA residual detected by PCR divided by log inactivation of each wavelength were calculated. For VUV, the value was more than 0.03 which was the ratio of target region to the whole genome. For UVC, due to the tailing of PCR results, value was not decided. But the three wavelengths revealed the similar value less than 0.03 and significantly differed with the VUV results. This observation suggested that the inactivation of phi-X 174 by UVC was associated with the genomic injury as reported and inactivation induced by VUV seemed completely different from that caused by UVC.

Bernardo Vazquez-Bravo, Greeley and Hansen
Authors: Bernardo Vazquez-Bravo, Kelley Goncalves, Joanna L. Shisler, Benito J. Marinas
11:40 - 12:00 PM

Human adenovirus (HAdV) is a waterborne pathogen highly resistant to monochromatic low-pressure (LP) ultraviolet (UV) light inactivation, and this aspect has determined the requirements for water disinfection by UV in the current USEPA regulations. Polychromatic medium-pressure (MP) UV light is found more effective at inactivating HAdV than LP UV light, but the fundamentals of this enhanced inactivation are not fully understood. Quantitative polymerase chain reaction (qPCR) and reverse transcriptase qPCR assays were used to elucidate the step in the HAdV replication cycle that was disrupted after exposure to low, intermediate, and high UV wavelengths within what is considered the germicidal range (200-300 nm). Bandpass filters were used to isolate 3 narrow polychromatic UV light emissions, with bandwidth of 20 nm, from a MP UV source. The low wavelength range, with peak emission at 224 nm, was the most effective at inactivating HAdV; increasing fluences at this range inhibited DNA replication, and early and late gene transcription consistently with the decrease in virus infectivity, measured by plaque assay, up to a viral inactivation efficiency greater than 99.99%. Additionally, indication of a structural modification of the viral capsid was observed by the effect of low wavelengths, and little impact on the viral genome integrity was detected. In contrast, the intermediate and high wavelength ranges (with peak emissions at 254 and 280 nm, respectively) did not inhibit early and late gene transcription consistently with the decrease in viral infectivity; greater genome damage was observed at these wavelengths, and indication of genome repair was detected. Furthermore, these wavelengths did not produce the conformational change of the viral capsid that the low wavelengths caused. The results of this work contribute to the fundamental understanding of the disinfection mechanisms at different UV wavelengths to help establish future guidelines and regulations, and implement alternative sources like UV-LEDs.

Kireev Sergey, Scientific and Production Enterprise "Melitta", Lt
Authors: Shashkovsky S.G., Deshevaya E.A., Fialkina S.V., Guridov A.A., Zhelayev I.A., Kireev S.G
12:00 - 12:20 PM

In accordance with the recommendations of the Committee on Space Research (COSPAR), the ExoMars-2020 robotic spacecraft, to be landed on Mars, shall not contain more than 300 microorganisms per 1 sq. meter to prevent interplanetary pollution. Taking into account that structural elements, containing semiconductor elements, it cannot be sterilized by traditional methods (thermal or radiation methods, or using liquid or gaseous oxidants), which may cause damage. A deep decontamination method for open surfaces joint treatment by high-intensity continuous-spectrum UV radiation fluxes and ethanol vapors was proposed and experimentally substantiated.

The efficiency of decontamination of open surfaces of materials, used in the landing module design, was studied at their preliminary contamination to 105-106 CFU/cm2 with sporous microorganisms, which are most resistant to continuous-spectrum UV radiation exposure. A pulse xenon lamp of the Yanex-2M unit was used as a source of continuous-spectrum UV radiation. The efficiency of decontamination of contaminated samples, preliminarily packed in a transparent and hermetically sealed film, was also studied.

The efficiency achieved in the experiments was demonstrated to correspond to the planetary protection requirements regardless of the type of materials used in the landing module design, except for porous materials. Required decontamination efficiency persisted while complex-shaped structural parts were irradiated with a reflected or scattered light.

Surface UV doses, time intervals and sequence of irradiation of structural element surfaces were defined. Recommendations on the procedure and modes of treating the landing module as a whole and its design elements were developed. Procedures for making large-volume “clean rooms” with high microbiological requirements as well as for maintaining cleanliness of the surfaces and air were worked out.

Nathan Moore, University of Toronto
Authors: Nathan Moore, Matias Attene Ramos, Katherine Bell, Nicole McLellan, Yanping Zhu, Shelir Ebrahimi, Liz Taylor-Edmonds, Susan Andrews, Ron Hofmann
13:40 - 14:00 PM

The UV/chlorine advanced oxidation processes (AOPs) applies a relatively high chlorine dose as a component of the AOP (4-5 mg/L). Although this chlorine is only in contact with water for a few seconds before being photolyzed by UV light, it has the potential to react with natural organic matter in the water to form a myriad of known and unknown disinfection by-products (DBPs). Little information exists, however, on the extent of by-product formation during UV/chlorine. This project aims to assess the amount and types of DBPs formed during UV/chlorine, and to investigate the impacts of chlorine and UV dose, LP vs. MP lamps, pH, and bromide on the overall toxicity of the samples.

In this work, laboratory- and full-scale UV/chlorine, UV/H2O2, chlorine, and UV treatments are applied to waters from several full-scale water treatment plants, chosen to represent two common applications for UV-based AOPs: (1) controlling taste and odour causing compounds in conventional drinking water treatment, and (2) treating RO-permeate in advanced treatment trains for potable reuse. Analyses for a comprehensive suite of over 30 regulated and emerging DBPs are performed to understand the occurrence and speciation of DBPs formed during UV/chlorine under different operational and water quality parameters. In addition, each water sample is assessed using a battery of bioassays for genotoxicity, overall cytotoxicity, and bioassays to detect p53 and ARE activation, to determine whether UV/chlorine leads to an increase in toxicity compared to UV/H2O2, or chlorine or UV alone. The results suggest that AOX and regulated by-product formation from chlorine alone may be greater than from UV/chlorine, but that more genotoxic by-products form during MP UV/chlorine, particularly at low pH. Ultimately, the goal of this work is to provide the water industry with needed information on the suitability of this novel treatment technology.

Min-Yong Lee, Tsinghua University
Authors: Min-Yong Lee, Ye Du, Wen-Long Wang, Hong-Ying Hu, Qian-Yuan Wu
13:40 - 14:00 PM

Reverse osmosis (RO) used in municipal wastewater reclamation system, on one way, can efficiently provide reclaimed water with high quality, on another way, also resulted in the discharge of RO concentrate that contains elevated toxic and recalcitrant organics. In this study, it was observed that UV/H2O2 and UV/PS could degrade the dissolved organic carbon (9.8% and 21.6%), chemical oxygen demand (41.2% and 49.8%), UV absorbance (53.7% and 59.3%) of ROC, respectively. To deep understand the oxidation mechanism in these two UV–AOPs, the performances of UV/H2O2 and UV/PS were systematically compared and discussed for changes of the fluorophore, molecular weight (MW) fractions, and electron–donating moiety, functional groups based on XPS. UV photolysis can only degrade a small amount of aromatic protein–like fluorophore (25–41%) (I and II), humic and fulvic acid–like, soluble microbial products, whereas UV/H2O2 and UV/PS system can efficiently degrade most fluorophores with removals of 67–76% and 80–96%, respectively. The reduction in MW fractions suggested that UV/H2O2 preferentially degraded high MW fractions, while UV/PS could decompose both high and medium MW fractions. This can be attributed to the different reactivities between ⦁OH and SO⦁4− that were generated in UV/H2O2 and UV/PS, respectively, which can be proved by the different changes of electron donating moieties in DOM. Especially, the XPS results revealed that the dominant electron–donating moieties of phenolic hydroxyl moieties were reduced to different lower extents by UV/PS than by UV/H2O2.

Sydney Ulliman, University of Colorado Boulder
Authors: Charles M. Sharpless, James S. Rosenblum, Karl G. Linden
13:40 - 14:00 PM

Regarding the effect of nitrate on UV/H2O2 efficacy, conflicting results have been reported within the literature and consequently it remains unclear if nitrate in the presence of organic matter has a positive, negative or neutral impact on radical production, especially at higher fluences (> 2000 mJ/cm2) of full-spectrum medium pressure UV (MPUV). The aim of this study was to determine if nitrate is an indirect source or sink of radicals with and without added H2O2 and to assess the role of nitrite formation during UV exposure. Because the behavior of nitrate has been shown to be influenced by organic matter, nitrate concentration, pH and water depth during UV photolysis, we developed an experimental design to systematically evaluate these parameters. Hydroxyl radical production, nitrite formation and degradation of low molecular weight compounds 1,4 dioxane and n-nitrosodimethylamine during bench-scale UV irradiation (up to 4000 mJ/cm2) of ground water, tertiary-treated wastewater, and activated-carbon treated source water containing nitrate (3 and 10 mg/L NO3-N) and hydrogen peroxide (0 and 10 mg/L) at different water depths (3 and 8 cm) were investigated. MPUV fluences were determined and reported using three methods (H2O2-weighted, germicidal-weighted, and unweighted), and MPUV results are currently being compared to those of low-pressure UV (LPUV).  Preliminary results show that hydroxyl radical production with MPUV is comparable to LPUV during irradiation of groundwater with nitrate and H2O2 addition at UV fluences  2000 mJ/cm2), which was attributed to a 67% increase in nitrite production. Additional experiments are underway to determine whether these observations hold for other water matrices.

Jennifer Pagan, AquiSense Technologies
Authors: Jennifer Pagan, Oliver Lawal, Rich Simons, Steve Pugh, Gary Hunter
13:40 - 14:00

There can be no uncertainty about the reality of UV-C LED-based water disinfection systems. Though young, LED technology has been deployed commercially in water disinfection systems by numerous corporations worldwide (e.g. AquiSense Technologies, Acuva Technologies, Crystal IS, HCEN, Stanley Electric, Watersprint, etc.) and will doubtless grow substantially in the coming years.

Much of the current focus lies around low-flowrate systems targeting point-of-use applications. However, within industry forums there is also much anticipation and discussion surrounding municipal-scale systems (e.g. those demonstrated by Typhon Treatment and MetaWater), though this is less mature than the point-of-use sector, operating pilot systems are underway.

Throughout the early development phase of UV-C LED-based reactors (2009 – 2015) advocates stressed the importance of developing new approaches to reactor design which maximise the opportunities of this radically different source geometry: despite this, significant effort was, and still is, being expended in an attempt to retrofit LEDs into traditional reactor designs, bearing little fruit in return.

The leading UV-C LED systems of today work with the nature of the LED source, rather than attempting to force a square peg into a round hole. One of the greatest strengths of LEDs as UV sources is their optical power density, leading designers towards smaller sources to maximise treatment efficiency. And herein lies the problem: LED systems are best suited to small footprint, low power, low flow applications, a perfect contrast to the large-scale municipal systems which currently dominate the UV disinfection sector.

This paper will discuss the inherent power density advantage of UV-C LEDs, its impact on reactor design and sizing, and provide experimental data which begins to bridge the gap between small systems and large-scale installations.

Jianchang Yan, Institute of Semiconductors, CAS
Authors: Jianchang Yan, Junxi Wang, Jinmin Li
14:00 - 14:20

We report the novel research work of AlN material and AlGaN-based deep ultraviolet light emitting diodes (DUV LEDs) fabricated on 2-D hexagonal boron nitride (hBN). High-quality AlN films on sapphire with 2-D hBN overlayer was grown by metal-organic chemical vapor deposition (MOCVD). DUV LED structure with strong light emission on hBN/sapphire was achieved. To facilitate the nucleation of AlN on hBN/sapphire, we introduced artificial dangling bonds for hBN by O2 plasma treatment (hBN-O2). The change of atoms connective structure of hBN materials after the O2 plasma treatment has been inferred according to the results of Raman spectroscopy and X-ray photoelectron spectroscopy. The reduced threading dislocation density of AlN on hBN-O2/sapphire compared to that of AlN on hBN/sapphire evidenced the effect of the O2 treatment. Moreover, the electroluminescence results of the DUV LED structures have exhibited strong emissions with a peak wavelength around 290 nm, which further confirms the high quality of the AlN. As the efficient DUV LEDs can be fabricated on hBN/sapphire, the DUV LEDs on unconventional substrates are expected to be fabricated by mechanical transfer or other methods. This work provides a possible solution for further developing efficient DUV LEDs on 2-D materials as well as other unconventional substrates.

Babak Adeli, Acuva Technologies Inc.
Authors: B. Adeli, A. Babaie
14:20 - 14:40

Ultraviolet (UV) radiation is known as the most effective water disinfection route. However, utilization of conventional UV-lamp can be limited for point-of-use (PoU) disinfection applications, due to their high energy consumption, frequent maintenance, warm-up time. Water disinfection systems based on germicidal ultraviolet light emitting diodes (UV-C LEDs) is emerged as an alternative UV source, offering enormous potentials for design and manufacturing of highly efficient PoU disinfection devices.

Despite its numerous advantages, commercial UV-C LEDs emerged in the last decade; thus, their characteristics and reliability are not well-documented. Uncertainties on the key characteristics of commercial UV-C LEDs, against those reported in manufacturer’s datasheet, such as total radiant flux, emission spectrum, radiation pattern, thermal stability, heat dissipation, and lone-term performance have incurred challenges on UV-LED water disinfection system designers and developers.

Here, we present a comprehensive study on optical, electrical and thermal characterization of UV-C LEDs. In addition, the importance of UV-C LEDs characteristics corresponding to the microbial performance of LED-based water disinfection application will be evaluated, and a guideline will be proposed to examine the reliability of UV-C LEDs through highly accelerated life test (HALT). The presented data will be compared to those provided in manufacturers datasheet, and the discrepancies will be elaborated. Finally, an insight on the reliability of UV-C LEDs, with focus on water disinfection application, will be proposed.

Pierrick Boulay, YOLE Developpement
14:40 - 15:00

The UVA LED market was the first to witness the UV LED industrial evolution, experiencing strong price reductions that have further accelerated the technology's penetration. UV curing is the main application, representing more than 80% of the UV LED market. With UVA LEDs being increasingly commoditized, the interest is now on UVC LEDs that are used for purification/disinfection applications.

Contrary to the UVA LED market, the UVC LED market has been less impacted by the flood of new entrants due to a technology being much more difficult to access than UVA LEDs. Despite devices being good enough today at a performance and cost level, the UVC LED market is still slow moving as systems implementing these LEDs require extended developments to fully benefit from the technology, which is taking more time than for UVA LED-based systems.

Regarding performances of UVC LEDs, EQE has improved but is still below 10% for commercial devices and each additional 1% seems harder and harder to achieve, but manufacturers continue to improve device power output from 10mW in 2014 to 100mW in 2017 at 280nm. This has already enabled the integration of UVC LEDs into small water reactors for point of use applications. But things are about to accelerate as UVC LED cost is decreasing drastically and as some UVC LED manufacturers are developing 150-200mW packages. Players are developing a strong know-how at the reactor level to integrate LEDs into mid-high power applications reaching high flow rates up to 2,000m3/day.

The combination of price reduction and performance increase will enable the integration of UV LEDs in totally new applications and in this domain, the consumer market could be a strong growth driver in the future.

In this presentation, we are going to highlight status of the UVC LED industry and recent trends but also discuss recent technology and market highlights in the UVC LED field.

Henry Bilinsky, MicroTau
Authors: Henry Bilinskyr
13:40 - 14:00

This paper reports on the successful proof of concept demonstration of the MicroTau Direct Contactless Microfabrication (DCM) technology for the application functional microstructures. The DCM process uses UV-cure technology to directly print 3D microstructure designs into UV coatings onto a surface in a manner that is fast, low-cost and scalable. MicroTau has been developing this process to print drag-reducing “shark skin” microstructures for military transport aircraft with the US Air Force Research Laboratory. Panels produced using the DCM method reliably exhibited a 6-7% viscous drag reduction in wind tunnel testing. MicroTau also fabricated novel 3D microstructure designs demonstrating the ‘single exposure 3D printing’ capability of the DCM technology. The DCM process has produced not only drag-reducing properties but also microstructures with optical, tactile and directional wetting effects. Other functional microstructure that may be possible to print with this technology include self-cleaning, microfluidic and anti-bacterial properties. Potential applications range from improving the efficiency of aircraft, marine vessels and wind turbines; anti-fouling surfaces and industrial production line applications.

Christian Dreyer, Fraunhofer IAP & University f. Appl. Sci. Wildau
Authors: Christian Dreyer
14:00 - 14:20

Within the last years, UV-LEDs gained more and more attention for various industrial applications. Main reasons are the availability of these relatively new UV-sources at steadily lower prices, by simultaneous increase of their efficiency making high intensities, competitive with established Hg-vapor-bulbs, possible. Furthermore, almost the whole wavelength region from approx. 300 – 420 nm, which is of importance for UV-curing, can be covered now by UV LEDsystems with high light-intensities. The consortium Advanced UV for Life – AUVL, funded by the German Government, Ministery for Education and Research, covers the complete value chain from the crystal growth of the LED-substrates, the LEDs themselves, the light-sources thereof and their use for different fields of application, like medicine, disinfection, environment & life sciences and production. The presentation will give an overview about a number of projects running since 2012 in the application area production of AUVL: The micrometer range is covered by the project OUD-LED, which focusses on the development of inks, optical resins, and photo-resists, which can be processed via UV-Inkjetting to 2.5 dimensional structures, for haptical applications, but also for use in microelectronics for mask-free designs and for permanent microstructures like optical waveguides. The project UV-Endlos is dedicated to roll-to-roll processes. The rapid curing of antiadhesive UVcoatings with a thickness of a few micrometers for release-papers is one goal of this project, while the development of a fast UV-curing process of alternative core-materials, so called nap-cores, for sandwich-panels in light weight construction is the second subject. UV-Co-light is focused on glass-fiber reinforced thermosetting polymers: Materials and processes for UV-LED curing of glass-fiber reinforced laminates with an area of up to 3.30 m x 33 m are developed as well as materials and a hybrid process using thermal and radiation curing for the fast and energy efficient pultrusion of glassfiber profiles. Inno-UV-faser’s subject is the development of UVLED- curable high-performance coatings for optical glass-fibers used in laser material-processing and medical surgery.

Christian Dreyer, Fraunhofer IAP & University f. Appl. Sci. Wildau
Authors: Christian Dreyer, Mathias Koehler, Juergen Rosenkranz
14:20 - 14:40

Glass fibers for optical applications are a large market worldwide. In addition to the narrow-diameter glass fibers commonly used in telecommunications (typically up to 200 μm), via which only light with low intensities is transmitted, glass fibers with diameters up to 2,000 μm are used for transmission of high light intensities in the areas of medical technology (laser surgery and dermatology, as well as dental lasers) and materials processing (laser cutting).

Above all due to their brittleness, glass fibers are usually equipped with polymer coatings. In the case of high power light transmission, these coating materials are often at their limits, so that the lifetime of these high-priced fibers is very limited.

UV curable resins are of special interest for these optical coatings, since the fast curing of resins by UV LEDs allow fast processing of the materials and short production times. Beside the processing properties of the resins also thermal and mechanical properties have to fulfill increasing requirements. In order to enhance the production speed and to safe energy a glass-fibre drawing tower at j-fiber was equipped with UV-LED modules to replace the currently used Mercury vapour lamps.

Fluorinated polymers, especially acrylates and methacrylates, were investigated and the development of a modular system of resins is necessary in order to achieve these properties. The studied thermosetting polymers provide an excellent curing behavior especially for UV LED cure.

Nicole Braun, DermaTronnier, Experimental Institute of Dermatology
Authors: Werner M., Garbe B., Theek C. Tronnier H., Heinrich U., Braun N.
14:40 - 15:00

The use of sunscreens benefits the health and is one of the measures that dermatologists recommend to reduce photo-aging and skin cancer. However, certain ingredients in sunscreen products are confirmed to have anti-inflammatory properties and are considered to suppress light-induced erythema, the biological endpoint for the SPF determination in vivo. In this case the SPF of the sunscreen products might be erroneously labeled too high and misleads the consumer into exposing themselves excessively to the sun. To help address this important issue we analyzed the frequently used ingredients Bisabolol and Panthenol in sunscreens regarding their potential to interfere with the development of the UV-erythema. Our study was specifically designed for the purpose to measure the direct impact of Bisabolol and Panthenol on the SPF in vivo using the international standard EN ISO2444:2010 method. In order to further validate the obtained results, a UV-model with a time course over 48 hours and a repeated application of the formulas after irradiation was used. Here, we found that neither the incorporation of Bisabolol nor Panthenol into sunscreens have an impact on the measured SPF in vivo. Even under a higher application rate no anti-inflammatory effect of the tested antiphlogistics over time could be found. Based on the obtained data we can conclude that the incorporated antiphlogistic ingredients Panthenol and Bisabolol in the tested sunscreen formulas do not interfere with erythema reddening and thus do not affect the SPF value in vivo. However, these findings also imply that there is no need to incorporate antiphlogistic agents in any quantity into active sunscreens, but should be only recommended in after-sun products to alleviate inflammatory instead.