Publications

UV light emitting diodes (LEDs) are considered the new frontier of UV water disinfection. As UV technologies continue to evolve, so does the need to understand disinfection mechanisms to ensure that UV treatment continues to adequately protect public health. In this research, two Escherichia coli (E. coli) strains (the wild type K12 MG1655 and K12 SP11 (ThiI E342K)) were irradiated with UV-C at 268 nm both independently and after exposure to UV-A (365 nm). A synergistic effect was found on the viability of the wild type E. coli K12 strain when UV-A irradiation was applied prior to UV-C. Sublethal UV-A doses, which had a negligible effect on cell viability alone, enhanced UV-C inactivation by several orders of magnitude. This indicated a specific cellular response mechanism to UV-A irradiation, which was traced to direct photolysis of the transfer RNA (tRNA), which are critical links in the translation of messenger …

United Nations Sustainable Development Goal 6.3 aims to half the proportion of untreated wastewater and increase recycling and safe water reuse. Therefore, developing robust technologies to achieve these goals, specifically in low- to middle-income countries, is of concern. One such technology, gravity-driven woven-fiber microfiltration (WFMF) has been shown to be a reliable, low-cost, and versatile water treatment process. This study investigated a gravity-driven WFMF system for treating secondary wastewater. Given the significant role of the microbial community in biological treatment processes, this investigation focused on the inter-relationship between the microbiomes of the influent, biofilm, and permeate, while further examining the system's performance regarding microbial activity and permeate water quality. The WFMF system reached a quasi-steady state after approximately 10 days. The microbiome …

Ultraviolet light-emitting diodes (UV LEDs) have shown ability to inactivate microorganisms and viruses in water. The unique characteristic of the UV-LEDs' diversity in wavelengths ranging from UV-C, UV-B, and UV-A, allows for wavelengths to be combined in different manners for polychromatic irradiation. Previous studies reported no synergy from simultaneous or sequential UV-C and UV-B as well as UV-C or UV-B followed by UV-A irradiation. However, synergy was reported for UV-A followed by UV-C or UV-B irradiation on various microorganisms. Nevertheless, no clear ground has been reached on whether to adopt single UV-C wavelengths or UV-A followed by UV-C LED, irradiation on inactivation of microorganisms and viruses in water. Therefore, this work evaluates the disinfection efficacy of single UV-C as well as UV-A followed by UV-C LED irradiation on Escherichia coli, Bacillus spizizenii spores and …

The objective of the Reducing Enteropathy, Undernutrition, and Contamination in the Environment (REDUCE) program is to identify exposure pathways to fecal pathogens that are significant contributors to morbidity among young children in the Democratic Republic of the Congo (DRC), and on developing and evaluating scalable interventions to reduce fecal contamination from these pathways. This prospective cohort study of 270 children under 5 years of age was conducted in rural South Kivu, DRC, to investigate the association between Escherichia coli in hand rinse, soil, food, object, surface, stored water, and water source samples and child developmental outcomes. Child developmental outcomes were assessed by communication, fine motor, gross motor, personal social, problem-solving, and combined scores measured by the Extended Ages and Stages Questionnaire (EASQ) at a 6-month follow-up …

Objective
The Reducing Enteropathy, Undernutrition, and Contamination in the Environment (REDUCE) program focuses on identifying exposure pathways to faecal pathogens for young children in the Democratic Republic of the Congo (DRC) and on developing scalable interventions to reduce faecal contamination from these pathways.
Methods
A prospective cohort study of 690 participants was conducted to investigate the association between hand, food, and environmental faecal contamination and diarrhoeal disease prevalence among young children in Walungu Territory, South Kivu, DRC. A total of 1923 hand rinse, soil, food, object, surface, stored water and water source samples were collected during unannounced spot checks after baseline enrolment and analysed for Escherichia coli. Caregiver reports of diarrhoea were obtained from children < 5 years at a 6‐month follow‐up.
Results
E.coli was …

This study reports the performance of high-frequency ultrasound (US, 1.7 MHz), coupled with a photo-Fenton-like process using persulfate and UV LEDs (UV/PS/Fe2+), for eliminating organic micropollutants and bacteria separately and simultaneously in deionized and natural water. Water matrices, containing atrazine (ATZ)/bisphenol A (BPA) and Escherichia coli/Enterococcus faecalis, were sequentially treated by UV/PS/Fe2+ and UV/US/PS/Fe2+ processes. The highest degradation rates by UV/US/PS/Fe2+ process were found for BPA in both matrices, achieving complete removal and synergistic effects (φ > 1). In terms of inactivation, this process was most efficient in deionized water for reducing E. coli and E. faecalis by 3 and 5 logs, respectively. The addition of bacteria inhibited the degradation in both matrices by decreasing the pseudo first-order rate constants up to one order of magnitude. In turn, the addition …

Decentralized wastewater treatment systems enable wastewater to be treated at the source for cleaner discharge into the environment, protecting public health while allowing for reuse for agricultural and other purposes. This study, conducted in Thailand, investigated a decentralized wastewater treatment system incorporating a physical and photochemical process. Domestic wastewater from a university campus and conventional septic tank effluent from a small community were filtered through a woven-fiber microfiltration (WFMF) membrane as pretreatment for ultraviolet (UV) disinfection. In domestic wastewater, WFMF reduced TSS (by 79.8%), turbidity (76.5%), COD (38.5%), and NO3 (41.4%), meeting Thailand irrigation standards for every parameter except BOD. In septic tank effluent, it did not meet Thailand irrigation standards, but reduced TSS (by 77.9%), COD (37.6%), and TKN (13.5%). Bacteria (total coliform and Escherichia coli) and viruses (MS2 bacteriophage) passing through the membrane were disinfected by flow-through UV reactors containing either a low-pressure mercury lamp or light-emitting diodes (LEDs) emitting an average peak wavelength of 276 nm. Despite challenging and variable water quality conditions (2% < UVT < 88%), disinfection was predictable across water types and flow rates for both UV sources using combined variable modeling, which enabled us to estimate log inactivation of other microorganisms. Following UV disinfection, wastewater quality met the WHO standards for unrestricted irrigation.

In many low-income countries, the poor conditions of sanitation systems have been a significant cause of mortality since they accelerate waterborne disease transmission. Developing sanitation systems in these countries is a pressing concern in both the public and private sectors.
This research investigated a decentralized domestic wastewater treatment system using ultraviolet light-emitting diodes (UV-LEDs). Although UV-LED disinfection has become more widespread in recent years, it is a novel approach for domestic wastewater treatment. Domestic wastewater was pretreated by a low-cost pretreatment system with an inclined settler and a sand filter prior to feeding a novel flow-through UV LED reactor. At an inlet flow rate of 30 L/h, the COD, TSS, and turbidity of the effluent were 17.7 mg/L, 3.0 mg/L, and 3.9 NTU, respectively. UV transmittance at 285 nm was enhanced from 29.1% to 70.4%, improving the …

The efficacy of germicidal ultraviolet (UV-C) light emitting diodes (LEDs) was evaluated for inactivating human enteroviruses included on the United States Environmental Protection Agency (EPA)’s Contaminant Candidate List (CCL). A UV-C LED device, emitting at peaks of 260 nm and 280 nm and the combination of 260/280 nm together, was used to measure and compare potential synergistic effects of dual wavelengths for disinfecting viral organisms. The 260 nm LED proved to be the most effective at inactivating the CCL enteroviruses tested. To obtain 2-log10 inactivation credit for the 260 nm LED, the fluences (UV doses) required are approximately 8 mJ/cm2 for coxsackievirus A10 and poliovirus 1, 10 mJ/cm2 for enterovirus 70, and 13 mJ/cm2 for echovirus 30. No synergistic effect was detected when evaluating the log inactivation of enteroviruses irradiated by the dual-wavelength UV-C LEDs.

Adenovirus, a waterborne pathogen responsible for causing bronchitis, pneumonia, and gastrointestinal infections, is highly resistant to UV disinfection and therefore drives the virus disinfection regulations set by the U.S. Environmental Protection Agency. Polychromatic UV irradiation has been shown to be more effective at inactivating adenovirus and other viruses than traditional monochromatic irradiation emitted at 254 nm; the enhanced efficacy has been attributed to UV-induced damage to viral proteins. This research shows UV-induced damage to adenoviral proteins across the germicidal UV spectrum at wavelength intervals between 200 and 300 nm. A deuterium lamp with bandpass filters and UV light-emitting diodes (UV LEDs) isolated wavelengths in approximate 10 nm intervals. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and image densitometry were used to detect signatures for the …

A dual-wavelength UV-C LED unit, emitting at peaks of 260 nm, 280 nm, and the combination of 260|280 nm together was evaluated for its inactivation efficacy and energy efficiency at disinfecting Escherichia coli, MS2 coliphage, human adenovirus type 2 (HAdV2), and Bacillus pumilus spores, compared to conventional low-pressure and medium-pressure UV mercury vapor lamps. The dual-wavelength unit was also used to measure potential synergistic effects of multiple wavelengths on bacterial and viral inactivation and DNA and RNA damage.
All five UV sources demonstrated similar inactivation of E. coli. For MS2, the 260 nm LED was most effective. For HAdV2 and B. pumilus, the MP UV lamp was most effective. When measuring electrical energy per order of reduction, the LP UV lamp was most efficient for inactivating E. coli and MS2; the LP UV and MP UV mercury lamps were equally efficient for HAdV2 and …

This work evaluated the feasibility of a photo-Fenton-like process using persulfate (PS) and ferrous iron (Fe2+) under simulated solar radiation for degrading the herbicide atrazine (ATZ, 6-Chloro-N-ethyl-N′-isopropyl-1,3,5-triazine-2,4-diamine) and inactivating E. coli. Milli Q water, lake water, and diluted wastewater effluents were spiked both simultaneously and separately with ATZ (4 mg/L) and E. coli (105 CFU/mL), and exposed to treatment. A method for determining the average irradiance throughout the water media in the UV(A+B) range of the Xe lamp emission was developed for bench-scale experiments. These values were used to calculate the UV(A+B) fluences and the solar UV(A+B) energy doses per unit of volume (QUV(A+B), kJ/L). The obtained kinetic data were presented versus energy dose. Treatment of lake water at near-neutral pH was ineffective via the photo-Fenton-like process, attaining only 20 …

Polychromatic UV irradiation is a common method of pathogen inactivation in the water treatment industry. To improve its disinfection efficacy, more information on the mechanisms of UV inactivation on microorganisms at wavelengths throughout the germicidal UV spectrum, particularly at below 240 nm, is necessary. This work examined UV inactivation of bacteriophage MS2, a common surrogate for enteric pathogens, as a function of wavelength. The bacteriophage was exposed to monochromatic UV irradiation from a tunable laser at wavelengths of between 210 nm and 290 nm. To evaluate the mechanisms of UV inactivation throughout this wavelength range, RT-qPCR (reverse transcription-quantitative PCR) was performed to measure genomic damage for comparison with genomic damage at 253.7 nm. The results indicate that the rates of RNA damage closely mirror the loss of viral infectivity across the …

This Protocol is based on the paper by Bolton and Linden (2003), but it is set out in a step-by-step manner to make it easier to follow for experimental measurements. The reader should first read the Bolton and Linden (2003) paper to understand the background for this Protocol. Also, convenient Excel spreadsheets are available either from the authors or in the Member Zone of the web site of the International Ultraviolet Association (www. iuva. org). The users of this Protocol should also consult Appendix C of the USEPA Ultraviolet Disinfection Guidance Manual (UVDGM, 2006), which is largely based on the Bolton and Linden (2003) paper. This Protocol provides more detail than does the UVDGM. However, the UVDGM also provides an excellent analysis of uncertainties in collimated beam testing. At various points in this Protocol, reference will be made to UVDGM (2006) where this Protocol differs from or expands on the protocol in the UVDGM.

ブンケン ショウロク チュウアツ シガイセン (UV) セツビ ニ ヨル ビョウゲンタイ ショウドク ニ オケル ケンショウ ノ タメ ノ サヨウ スペクトル

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Ultraviolet (UV) reactors used for disinfecting water and wastewater must be validated and monitored over time. The validation process requires understanding the photochemical properties of the pathogens of concern and the challenge microorganisms used to represent them. Specifically for polychromatic UV systems, the organisms' dose responses to UV light and their sensitivity across the UV spectrum must be known. This research measured the UV spectral sensitivity, called action spectra, of Cryptosporidium parvum, and MS2, T1UV, Q Beta, T7, and T7m Coliphages, as well as Bacillus pumilus spores. A tunable laser from the National Institute of Standards and Technology was used to isolate single UV wavelengths at 10 nm intervals between 210 and 290 nm. Above 240 nm, all bacteria and viruses tested exhibited a relative peak sensitivity between 260 and 270 nm. Of the coliphage, MS2 exhibited the …

Ultraviolet (UV) disinfection relies on the principal that DNA exposure to UV irradiation leads to the formation of cytotoxic lesions resulting in the inactivation of microorganisms. Cyclobutane pyrimdine dimers (CPDs) account for the majority of DNA lesions upon UV exposure. Past research has demonstrated reversal of CPDs in extracted DNA formed at high UV-C wavelength irradiation (280 nm) upon subsequent irradiation at lower UVC wavelengths (230–240 nm). Medium-pressure (MP) UV lamps produce a polychromatic emission giving rise to the possibility that cellular DNA in a target pathogen may undergo simultaneous damage and repair when exposed to multiple wavelengths during the disinfection process, decreasing the efficiency of MP UV lamp disinfection. Culture techniques and a quantitative polymerase chain reaction (qPCR) assay were used to examine cell viability and DNA damage reversal …

Adenovirus is regarded as the most resistant pathogen to ultraviolet (UV) disinfection due to its demonstrated resistance to monochromatic, low-pressure (LP) UV irradiation at 254 nm. This resistance has resulted in high UV dose requirements for all viruses in regulations set by the United States Environmental Protection Agency. Polychromatic, medium-pressure (MP) UV irradiation has been shown to be much more effective than 254 nm, although the mechanisms of polychromatic UV inactivation are not completely understood. This research analyzes the wavelength-specific effects of UV light on adenovirus type 2 by analyzing in parallel the reduction in viral infectivity and damage to the viral genome. A tunable laser from the National Institute of Standards and Technology was used to isolate single UV wavelengths. Cell culture infectivity and PCR were employed to quantify the adenoviral inactivation rates using …

The use of bioassays to determine reduction equivalent doses delivered by UV reactors is recognized as an effective measure of UV disinfection systems. Low pressure (LP) UV delivered in controlled collimated beam systems provides dose response curves which are then compared against reactor performance to quantify the delivered dose. It is recognized that the appropriateness of monochromatic LP dose curves for validating polychromatic medium pressure depends on knowledge of the action spectra of the bioassay surrogate and the target pathogen. Further complicating the relationship between REDs generated during validation and effective dose delivered by a medium pressure UV system at an installation is the absorbance spectrum of the validation water vs that at the utility. Other factors that affect the dependability of bioassay results for medium pressure systems include quartz sleeve absorbance …

This research was performed as part of the San Francisco Public Utilities Commission’s search for more sustainable water resources. Disinfection methods were evaluated for treating light graywater to California drinking water standards for unrestricted, direct nonpotable water use, indoors. Graywater originating from sinks and showers in a commercial office building in southern California was collected in grab samples over 4 weeks. Samples were filtered and tested for disinfection efficacy toward indigenous total coliforms and Enterococci as well as seeded male-specific 2 (MS2) coliphage. The filtered samples were exposed to monochromatic (253.7 nm) ultraviolet (UV) light, chlorination with sodium hypochlorite, and ozonation. A UV dose of 100 mJ/cm2 completely inactivated Enterococci and inactivated total coliforms to California drinking water standards required levels and achieved 5-log reduction of MS2 in half of the …

Water disinfection using ultraviolet (UV) light, while proven and well established in high income settings, is an emerging tool for improving access to safely managed drinking water in rural areas, humanitarian relief settings and low and middle-income regions. However, there is little information comparing existing UV systems in those contexts, towards improving the effectiveness and reliability of future UV systems. In this work, 19 case studies of small (most≤ 10 LPM, and all cases< 50 LPM), decentralized UV water disinfection systems being used during the last 30 years to improve water access are presented. The case studies cover a wide range of project types, including schools, hospitals, communities, households and healthcare facilities, spanning across five continents: Asia, Africa, Oceania, Europe and North America. Moreover, the studies demonstrate a variety of UV-based systems, energy sources, water sources and social environments. Each case study describes the background objectives and motivations, water treatment systems, and, most importantly, the outcomes and lessons learned. An interactive web-based map has been created to illustrate the case studies and to catalogue future examples. In general, the use of UV immediately improved the microbiological quality of the water and health outcomes among users; however, long-term (eg, multiple years) tracking of system performance and sustainability is largely missing. UV system effectiveness was limited by several factors, including the potential for recontamination after UV disinfection, insufficient maintenance, and the absence of regulatory frameworks that allow the more …

In the face of challenges posed by limited freshwater resources, drought, growing populations, and climate change, achieving Sustainable Development Goal 6 (SDG6) proves particularly daunting, especially for low-income and less-developed countries, especially those in inland areas with restricted access to freshwater. Reverse osmosis (RO) systems offer a viable solution for treating brackish water (BW), a common but underutilized water resource. However, the energy-intensive nature of brackish water reverse osmosis (BWRO) systems poses affordability challenges to water supply, necessitating a focus on minimizing their energy consumption to support SDG6's goal of providing safe and affordable drinking water for all. This study addresses the critical need to reduce the specific energy consumption (SEC) of a typical BWRO system, defined as the energy consumed per unit of water recovered, while also identifying the key operating factors and their priority levels, along with their interactive effects. Notably, no prior study has comprehensively discussed the significance and interaction of these factors on BWRO system SEC. Employing a full factorial experimental design with mixed levels of operating parameters, including feed flow rate, salinity, pressure, temperature, and membrane permeability, the study develops regression models that elucidate the mechanistic interaction between these parameters and system performance. Validation of the models with a new dataset demonstrates their accuracy and reliability, achieving an R2 of over 93%. ANOVA statistical analysis identifies pressure, feed flow rate, salinity, feed flow rate× pressure …