UV Technology and One Water Research Around the Globe

IUVA One Water
By corresponding authors Izzy Medeiros and James P. Malley, Jr., Ph.D., Department of Civil and Environmental Engineering, University of New Hampshire

The following represent interesting UV water-related presentations from the last six months.

Developing the United Kingdoms’ First Draft UV Validation Protocol

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

Toward a New Standard for Disinfection of Drinking Water Based on UV-C LEDs – Characteristic LED Parameters and Requirements

Authors Peter Sperfeld, S. Nevas, F. Schröppel, K. Schwind, Th. Gerloff and L. Ulm, PTB; J. Eggers, T. Schwarzenberger and K.-H. Schön, DVGW-Technologiezentrum Wasser; M. Paravia, Opsytec Dr. Gröbel GmbH; S. Einfeldt, J. Rass and J. Ruschel, Ferdinand-Braun-Institut (FBH); C. Bokermann and A. Wilm, Xylem Services GmbH
UV-C LEDs are being considered for the disinfection of public drinking water, prompting the need for defining their characteristics and efficacy. The joint research project “DINoLED” investigates the necessary preconditions for a new German DIN standard that outlines test criteria for LED-based UV disinfection systems in municipal waterworks. The DIN 19294 series of standards in Germany, for instance, sets technical requirements for testing water disinfection equipment using ultraviolet radiation. One requirement is a reduction equivalent fluence of 400 J/m² at 254 nm for UV disinfection. To evaluate this, biodosimetry is conducted during reactor testing, where Bacillus subtilis spores are introduced into the system and their inactivation rate is measured. Within the DINoLED project, a new detailed action spectrum for Bacillus subtilis was determined, showing a fine structure around 270 nm and a steeply descending curve above 280 nm. The main outcome of the project will be a first pre-draft of a test standard similar to existing protocols for mercury lamp-based systems. The shift toward UV-C LED disinfection systems necessitates such new standards and test methods. The properties and microbicidal efficacy of UV-C LED sources have been investigated within the project. The centroid wavelength and spectral distribution of UV-C LED systems was found to play a crucial role in their microbicidal efficacy, with significant higher efficacy values achieved around 270 nm compared to low-pressure mercury lamps. As UV-C LED disinfection systems comprise multiple individual LEDs, variations in their individual performance can alter the resulting spectral distribution of the total system. Therefore, criteria must be established for LED binning tolerances and allowable changes in validated systems. After a short introduction of the DINoLED project, the new action spectrum for Bacillus subtilis will be presented and the microbicidal efficacy factor of LEDs as well as other characteristic parameters will be introduced and discussed.

Large-Scale Water Treatment Case Studies Deploying UV LED Technology

Author Oliver Lawal
The potential to use UV-C LEDs in the treatment of water has long promised all the benefits of UV disinfection; absence of chemicals, ease of use, pathogen specific targeting. All without the drawbacks of mercury-lamp technology; warm-up time, on/off cycling limitations, heavy metal contamination risk. The commercialization of this technology has been documented at a Point-Of-Use and Point-Of-Entry scale applications over the past few years and continues to show growth. A number of these smaller commercial UV-C LED system are listed under NSF-55 certification and other national standards in the UK, France, etc. The question therefore arises, is when and how will this technology scale to larger industrial and municipal applications? Is it possible to overcome the barriers of relatively high-cost/low-efficiency LED devices, new UV system engineered solutions and regulatory barriers for these larger flow applications. This paper will give an overview of some of the UV-C LED technology projects currently in progress within the larger flow rate ranges. It will provide application goals and performance results as far as possible. It also will outline the challenges and advantages that have been seen. The case studies include: United Utilities – Typhon Treatment -Municipal Drinking Water, United Kingdom -28 MLD (5,072 USGPM) Southern Nevada Water/Las Vegas Valley Water – AquiSense Technologies -Municipal Drinking Water, USA -6 installations with flow rates 315 m3/hr to 1,500 m3/hr Metawater Pilot -Drinking Water, Japan -55 gpm to 300 gpm HDR -Potable Reuse, USA -Goal to improve long-term water supply resiliency & water quality using UV Disinfection with comparison of conventional and LED UV technology CU Boulder -Mobile Trailer, USA -Compare LP UV & UV LED system for disinfection of pathogens and viruses. Operate as an AOP by injecting either hydrogen peroxide (H2O2) or free chlorine into the water upstream of the UV unit Halifax Water -Water Discharge, Canada -To compare existing LP UV system with LED UV system.

Advancing Advanced Oxidation using Low Wavelength UV

Authors: Bryan Liu, Lauren Mullen, E. Michael Thurman, Imma Ferrer, Emma Payne, Karl G. Linden
KrCl* excimer lamps, emitting UV in the far UV-C range (200-222 nm) has been shown to effectively kill pathogens in air and water while remaining relatively harmless to human skin and eyes. However, limited studies have investigated the use of KrCl* excimer lamps for UV/advanced oxidation processes (AOPs) in comparison to conventional mercury-based lamps. Here, we compared contaminant degradation between LPUV and KrCl* excimer lamps for both carbamazepine (CBZ) and NDMA. The compounds were chosen based on their distinct quantum yield (Φ_CBZ=6×10^(-4) mol/Es,Φ_NDMA=0.25 mol/Es) at 254 nm and 2nd order reaction rate constants with •OH (k_(•OH/CBZ)=8.02×10^9 M^(-1) s^(-1),k_(•OH/NDMA)=3.30×10^8 M^(-1) s^(-1) ). Results illustrated that direct photolysis by KrCl* excimer lamps significantly improves the photolysis rate constants of both carbamazepine and NDMA compared to LPUV, likely due to a higher molar absorption coefficient at 222 nm compared to 254 nm. KrCl*/AOP upon addition of hydrogen peroxide, was able to further improve carbamazepine degradation compared to KrCl* excimer direct photolysis but didn’t improve the degradation of NDMA. The degradation pathway of carbamazepine through direct photolysis of KrCl* excimer lamps in lab grade water was investigated utilizing high-resolution liquid chromatography mass spectrometry (LC/MS). Despite the absence of any radical promoters (i.e., hydrogen peroxide) present in the water, results demonstrated that both direct photolysis and hydroxyl radical-driven decay are involved in the degradation process as evidenced by •OH addition as part of the CBZ transformation. This indicates that a de facto AOP may occur when utilizing KrCl* excimer lamps for degradation of contaminants in water and can potentially be a cost-saving alternative to conventional LPUV.

Effective Advanced Oxidation of 1,4 – Dioxane Utilizing 222 nm UV Light

Authors Yaal Lester, Karl G. Linden, Sara Hayoune, Emma Payne
UV – based advanced oxidation processes (UV/AOPs) have high potential in treating many recalcitrant organic water contaminants. However, to realize its full potential, the technology must overcome some key mechanistic drawbacks, principally the low concentration of the main active oxidant – •OH radical. A possible solution is the use of a new UV source: krypton chloride (KrCl*) excimer lamp, which emits narrow-band UV light at 222 nm. This wavelength strongly overlaps absorption spectra of common •OH promoters, potentially enhancing radicals’ formation and improving contaminants removal. The goal of this study was to determine the effectiveness of UV/H2O2, based on KrCl* excimer 222 nm UV lamp, for treating 1,4 – dioxane, a notorious groundwater contaminant, frequently detected in sites impacted by industrial wastewater. Results showed that UV/H2O2 degradation of the contaminant in DI, using KrCl*, was up to ninefold faster than its degradation with both low-pressure and medium pressure Hg lamps, commonly used for water treatment. However, degradation was highly affected by non-target light absorbing water constituents, specifically natural organic matter and nitrate (while marginally affected by carbonates). For example, addition of up to 5 mg/L-N nitrate to the water decreased 1,4 – dioxane degradation rate by one order of magnitude. Considering other important factors such as the enhanced formation of nitrite under short wavelength, lead to the conclusion that KrCl*/H2O2 can be an attractive alternative to Hg UV lamps mostly for treating water with low levels of nitrate and organic matter.

Rapid Dehalogenation of Refractory Organic Contaminants in Water by Far UV-C Photolysis of Sulfite

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

Degradation of Norfloxacin in Water by Medium-Pressure Ultraviolet/Peracetic Acid Process

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

Considerations for Implementing UV Disinfection Technologies in Rural Areas

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

Demonstration and Implementation of a UV LED Module at Water Treatment Facilities in Remote Locations

Author Kumiko Oguma
UV LED can be a good-fit option for small and decentralized water treatment facilities in remote locations due to its tiny size, physical robustness, relatively long lifetime (10,000 hours+, depending on the product) and mercury-free components. UV LED modules designed for such applications are commercially available, but their performance is pre-validated mostly in a lab-scale with pure-cultured challenge microorganisms, not in the field. To promote the data-driven implementation of UV LED systems while understanding the challenges in practice, it is inevitable to conduct field testing in a long-term to evaluate the performance against indigenous microorganisms. Demonstration studies of a UV LED flow-through module were conducted at three water treatment facilities located in remote areas in Japan. A UV LED flow-through module was tested for 1-2 years at each location, and its performance was monitored in the inactivation of indigenous bacteria including Escherichia coli (E. coli), total coliforms, standard plate count bacteria and heterotrophic plate count bacteria. The source water quality in the physical-chemical parameters, such as turbidity and UV transmittance, also were monitored to understand the natural fluctuation of such parameters and their impacts on the inactivation efficiency. Overall, the results demonstrated that the UV LED module is effective and stable enough for practical applications. For example, at a test site sourcing a river running through a mountain valley, the source water was 100% positive with E. coli while the treated water was negative or contained a trace level of E. coli. All monitoring data were shared with the local government and community residents, which eventually resulted in the implementation of the module in some locations. Such “demonstration-to-implementation” scheme would be a good approach to promote UV LED technologies and applications.

Evaluation of Scaling and Fouling in Low Pressure and UV LED Systems for Use in Rural Communities.

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

Design and Field-Testing of a Biosand/Charcoal and Gravity-Driven Flow-Through UV-C LED System for Treating Harvested Rainwater in a Marginalized Rural Community, Kenya

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

Understanding the Causes of Variability and Impact of Viral Surrogates on UV Validation

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

Disinfection and Damage of Nontuberculous Mycobacteria by Different UV Wavelengths

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

Application of UV LEDs in Chlorine-Based Advanced Oxidation Processes for Removal of Pesticides from Drinking Water

Authors Priya Dharwadkar, Irene Carra, Peter Jarvis, Olivier Autin, Emma Goslan, Pablo Campo Moreno
The UV/chlorine advanced oxidation process (AOP) is a promising alternative to the conventional UV/hydrogen peroxide (UV/H2O2) process due to the availability of chlorine disinfectants, like hypochlorite (HOCl), at water treatment works. Chlorine photolysis also generates reactive chlorine species (RCS) in addition to hydroxyl radicals (HO●). UV/chlorine also is compatible for use with UV LEDs as these can be configured to emit light at wavelengths compatible for photolysis of chlorine. UV LEDs allow for flexible reactor design and operation compared to conventional mercury lamps. However, chlorine photolysis also is influenced by pH since aqueous chlorine dissociates into HClO or ClO-, depending on pH and each of these species has different absorption properties. There is lack of studies that account for the synergistic impact of wavelength of irradiation and pH on radical composition and yield when comparing UV/HOCl and UV/H2O2 AOPs. How these AOPs differ in terms of transformation pathways and by-products of pesticide degradation is yet to be studied. Bench scale AOP tests were conducted to compare the degradation of five persistent pesticides in the UV/chlorine and the UV/H2O2 processes. Pesticides were selected based on occurrence and for representation of different reactivities toward the various radicals produced. Operating conditions such as choice of oxidant, wavelength of irradiation and pH, were varied to evaluate their impact on radical production and pesticide degradation. The transformation products were identified, and transformation pathways were compared between the AOPs. The results of this study will provide a detailed comparison of UV/Chlorine and UV/H2O2 technologies and allow for a better understanding of the upstream and downstream processes required for the successful application of UV/chlorine AOPs for drinking water treatment.