Article

Fluence (UV Dose) Required to Achieve Incremental Log Inactivation of Bacteria, Protozoa, Viruses and Algae

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... The 265 nm kinetic data for E. coli (ATCC 11229) were obtained following the method proposed by Kheyrandish et al. [15], and the 275 nm kinetic data for E. coli were adapted from values reported in the literature [22] (Fig. 4). By analyzing the kinetic data reported for E. coli (ATCC 11229) and MS2 (ATCC 15597-B1) by several researchers [23] using the collimated beam apparatus, the 254-nm fluence-response curves of MS2 were obtained (Fig. 4). For each log-inactivation on the curve, the corresponding fluence, along with its 99 % confidence interval, was calculated. ...
... Since it is assumed that LED's radiation profile is only a function of polar angle, Eq. (3) represents the radiant intensity profile of LED, the show the average of log-inactivation for any given fluence that lies between upper and lower bounds. The upper and lower bounds show the maximum and minimum fluence that lead to a particular inactivation, as reported in the literature [23]. The region between upper and lower limits indicates 99 % confidence interval. ...
... The gray solid line shows E. coli (ATCC 11229) average 254 nm fluenceresponse data which lies between the upper and lower bounds. The upper and lower bounds show the maximum and minimum fluence that lead to a particular inactivation, as reported in the literature [23]. The region between upper and lower limits indicates 99 % confidence interval. ...
Article
The Ultraviolet Light-Emitting Diode (UV-LED) is a new UV source suitable for small to mid-size water disinfection units. The design of a UV-LED reactor entails the integration of hydrodynamics, radiation, and kinetics data. The kinetics of microbial inactivation are necessary for UV-LED reactor design and the determination of kinetic rate constants depends on the accuracy of fluence rate measurement. However, there is not an easy way to measure the fluence rate inside a solution. In this study, a computational method is proposed to calculate irradiance and fluence rate based on the LED’s relative radiation profile and its radiant power, which are two standard pieces of information available in an LED’s datasheet. UV-LED was modeled as a polychromatic point source with a specific radiation profile and the fluence rate was calculated by solving the Radiative Transfer Equation by considering the refraction, reflection, and absorption of the medium. The irradiance and fluence rate predictions on the surface of the water were evaluated successfully by radiometry and actinometry measurements, respectively. The fluence rate imposed by 265-nm UV-LED and 275-nm UV-LED in Petri dishes with internal diameters of 5 cm and 9 cm were measured using biodosimetry with E. coli and MS2, when the UV-LED germicidal factor was obtained by considering the LED emission spectrum and the microorganism action spectra. Biodosimetry experiments using E. coli and MS2 at exposure times over 200 s indicated a close agreement between the simulation and experimental data. Such results are indicating the kinetic rate constants of a microorganism can be estimated without performing kinetic study using the action spectrum of microorganisms. Further, the results showed the proposed method can be applied for fluence rate determination for any LED’s radiation profile, LED position, and the experimental apparatus’s regardless of the availability of the action spectrum of microorganisms.
... In the electromagnetic spectrum, UV light falls between visible light and X-rays. UV light is categorized as: Far UV from 100 to 200 nm, UV-C from 200 to 280 nm, UV-B from 280 to 315 nm, and UV-A from 315 to 400 nm (Hijnen et al. 2006;She et al. 2020;Malayeri et al. 2016). Previous research has shown that when microorganisms are exposed to UV-C, the absorption by DNA or RNA prevents cell multiplication and reproduction (Hijnen et al. 2006;She et al. 2020;Malayeri et al. 2016). ...
... UV light is categorized as: Far UV from 100 to 200 nm, UV-C from 200 to 280 nm, UV-B from 280 to 315 nm, and UV-A from 315 to 400 nm (Hijnen et al. 2006;She et al. 2020;Malayeri et al. 2016). Previous research has shown that when microorganisms are exposed to UV-C, the absorption by DNA or RNA prevents cell multiplication and reproduction (Hijnen et al. 2006;She et al. 2020;Malayeri et al. 2016). ...
... Non-virus strain (Table 2) was used for validation because of Biosafety Level 3 (BSL-3) requirements (Mourya et al. 2014). The UV-C dose required for disinfection based on previous research was shown in Table 2 (Malayeri et al. 2016). The chosen nonvirus strains for validation had similar UV-C resistance as that of most of the viruses (Malayeri et al. 2016). ...
Article
Used face masks are hazardous waste and must be discarded immediately upon removal. Instead of throwing used masks into the disposal bin, disinfecting the masks is essential to break the chain of infection spread. The development of this device was attempted for COVID-19 management, with the following focus: (1) solution which have sufficient science background established so that extensive experimental validation need not be attempted during the lockdown period in India. (2) Provide solution which could be replicated with local resources and minimum material movement. Therefore, in response to the pressing societal demand we designed, prototyped, verified and validated an UV-C-based multipurpose disinfection device. The device after safety and efficacy evaluation as per the Indian Council of Medical Research (ICMR) guidelines for novel COVID-19 solutions, received Central Drugs Control Standard Organization (CDSCO) registration as non-notified medical device for commercialization.
... The minimum dose required for pathogen inactivation depends on both the irradiation wavelength and the specific pathogen, with some pathogens requiring much higher UV-C doses for inactivation that others (e.g., certain bacterial spores compared to enveloped, singlestranded RNA viruses). 12 A pathogen's ''action spectrum'' describes relative inactivation efficacy as a function of wavelength, and action spectra typically have a peak near 260 nm (the maximum absorption of nucleic acids). 13 The minimum dose required for inactivation also depends upon the material on or in which pathogens are present (e.g., air, surfaces, or aqueous media). ...
... The UV-C dose required to inactivate pathogens in air, water, and on surfaces is organismdependent, due to organism-to-organism differences in nucleic acid structure and nucleotide content, as well as varying amounts of UV-absorbing proteins and other photoprotective components. 12 Higher UV-C doses are generally required to inactivate bacterial and fungal spores, compared to viruses and vegetative bacteria. 7 Among viruses, *3 · higher UV-C doses are required to inactivate viruses with double-stranded RNA or DNA on surfaces, compared to single-stranded viruses; higher dose requirements in double-stranded viruses are attributable to more robust repair mechanisms, as the second strand can serve as a template for repair. ...
... UV-C susceptibility of different pathogens on N95 FFRs and textiles. The minimum UV-C dose required to inactivate both enveloped and nonenveloped viruses on N95 FFRs is several hundred-fold higher than doses typically used for decontamination of similar pathogens on nonporous surfaces, 12 in air, and in solution (Table 1), because UV-C light is attenuated upon passing through the N95 FFR layers. UV-C irradiances that reach the internal N95 filtering media are *3-400 · lower than the irradiance at the FFR surface, depending on the FFR model. ...
Article
Full-text available
Introduction: The COVID-19 pandemic has led to critical shortages of single-use N95 filtering facepiece respirators. The US Centers for Disease Control and Prevention has identified ultraviolet-C (UV-C) irradiation as one of the most promising decontamination methods during crisis-capacity surges; however, understanding the mechanism of pathogen inactivation and post-treatment respirator performance is central to effective UV-C decontamination. Objective: We summarize the UV-C N95 decontamination evidence and identify key metrics. Methods: We evaluate the peer-reviewed literature on UV-C decontamination to inactivate SARS-CoV-2, viral analogues, and other microorganisms inoculated on N95s, as well as the resulting effect on respirator fit and filtration. Where peer-reviewed studies are absent, we discuss outstanding questions and ongoing work. Key Findings: Evidence supports that UV-C exposure of ≥1.0 J/cm2 inactivates SARS-CoV-2 analogues (≥3-log reduction) on the majority of tested N95 models. The literature cautions that (1) viral inactivation is N95 model-dependent and impeded by shadowing, (2) N95 straps require secondary decontamination, (3) higher doses may be necessary to inactivate other pathogens (e.g., some bacterial spores), and (4) while N95 fit and filtration appear to be preserved for 10-20 cycles of 1.0 J/cm2, donning and doffing may degrade fit to unacceptable levels within fewer cycles. Results and Discussion: Effective N95 UV-C treatment for emergency reuse requires both (1) inactivation of the SARS-CoV-2 virus, achieved through application of UV-C irradiation at an appropriate wavelength and effective dose, and (2) maintenance of the fit and filtration efficiency of the N95. Conclusions: UV-C treatment is a risk-mitigation process that should be implemented only under crisis-capacity conditions and with proper engineering, industrial hygiene, and biosafety controls.
... 25 mJ/cm 2 dose of UVC (254 nm: mercury lamp) for a log inactivation of 3 (Kowalski, 2010). In contrast, for the same amount of log inactivation, adenoviruses require 140 mJ/cm 2 of UVC irradiation (Malayeri et al., 2016). The relationship between the incremental log inactivation of various pathogens (including viruses) and UV irradiation doses using different UVC sources was also studied (Chevrefils et al., 2006). ...
... • At close distances, the radiation produces a higher destructive effect. (Chevrefils et al., 2006;Heßling et al., 2020;Malayeri et al., 2016) 3. ...
Article
Full-text available
The ongoing COVID-19 pandemic made us re-realize the importance of environmental disinfection and sanitation in indoor areas, hospitals, and clinical rooms. UVC irradiation of high energy and short wavelengths, especially in the 200–290-nm range possesses the great potential for germicidal disinfection. These properties of UVC allow to damage or destruct the nucleic acids (DNA/RNA) in diverse microbes (e.g., bacteria, fungi, and viruses). UVC light can be used as a promising tool for prevention and control of their infection or transmission. The present review offers insights into the historical perspective, mode of action, and recent advancements in the application of UVC-based antiviral therapy against coronaviruses (including SARS CoV-2). Moreover, the application of UVC lights in the sanitization of healthcare units, public places, medical instruments, respirators, and personal protective equipment (PPE) is also discussed. This article, therefore, is expected to deliver a new path for the developments of UVC-based viricidal approach in the context of the UVC susceptibility against the coronaviruses.
... The germicidal range in the UV-C region (l < 280 nm) is mostly applied in water treatment systems by low and medium pressure mercury lamps as a UV-C source. The efficacy of these UV-C sources is well known, and the UV doses needed to inactivate several pathogens (including bacteria, viruses, etc.) are well established (Malayeri et al., 2016). However, the potential toxicity of mercury from the lamps, their high cost, low efficiency and relatively short lifetime appears as the main concerns of this traditional source of UV-C (Song et al., 2016). ...
... mJ cm À2 . It agrees with values obtained for the same bacterial groups under traditional mercury lamps (UV 254nm ) (Malayeri et al., 2016). This also agrees with a previous study in which 4 mJ cm À2 (l 265 ) achieved approximately 2 LRV for other opportunistic bacteria, such as Pseudomonas aeruginosa (Rattanakul and Oguma, 2018). ...
Article
The development of technologically advanced recirculation aquaculture systems (RAS) implies the reuse of water in a high recirculation rate (>90%). One of the most important phases for water management in RAS involves water disinfection in order to avoid proliferation of potential pathogens and related fish diseases. Accordingly, different approaches have been assessed in this study by performing a comparison of photolytic (UV-LEDs) at different wavelengths (λ = 262, 268 and 262 + 268 nm), photochemical (UV-LEDs/H2O2, UV-LEDs/HSO5⁻ and UV-LEDs/S2O8²⁻) and photocatalytic (TiO2/SiO2/UV-LEDs and ZnO/SiO2/UV-LEDs) processes for the disinfection of water in RAS streams. Different laboratory tests were performed in batch scale with real RAS stream water and naturally occurring bacteria (Aeromonas hydrophyla and Citrobacter gillenii) as target microorganisms. Regarding photolytic processes, higher inactivation rates were obtained by combining λ262+268 in front of single wavelengths. Photochemical processes showed higher efficiencies by comparison with a single UV-C process, especially at 10 mg L⁻¹ of initial oxidant dose. The inactivation kinetic rate constant was improved in the range of 15–38%, with major efficiency for UV/H2O2 ∼ UV/HSO5⁻ > UV/S2O8²⁻. According to photocatalytic tests, higher efficiencies were obtained by improving the inactivation kinetic rate constant up to 55% in comparison with a single UV-C process. Preliminary cost estimation was conducted for all tested disinfection methods. Those results suggest the potential application of UV-LEDs as promoter of different photochemical and photocatalytic processes, which are able to enhance disinfection in particular cases, such as the aquaculture industry.
... where K F, Microplasma (cm 2 mJ − 1 ) is the fluence-based first-order rate constant of log removal for each microplasma UV source and K F, LPMVL (cm 2 mJ − 1 ) is the corresponding value for LPMVL. Here, the K F, LPMVL values for studied microorganisms were collected and averaged from the data in the literature [44]. In a collimated and uniform irradiance assured experimental condition, theoretical and action GE values should be equal. ...
... E. coli is known as a highly photoreactive but UV-sensitive ERM with a relatively weak DNA protection mechanism (during UV exposure) compared with other ERMs [54]. A short UV-resistant shoulder region (<5 mJ.cm − 2 ) and easy 4-log-inactivation (<10 mJ.cm − 2 ) were reported for E. coli even under 254 nm irradiation [44]. Therefore, the DNA damage has been the dominant phenomenon, and the effect of reducing the shoulder region is not outstanding. ...
Article
Pathogenic microbes are becoming one of the biggest health-threatening challenges leading to a global need for sustainable solutions. Ultraviolet (UV) radiation enables the control of microorganismal replication. However, microbes with protected and/or repairable nucleic acids have challenged the inactivation efficacy of current UV sources. Targeting proteins responsible for nucleic acid protection and repair or microbial infection can be game-changing. Here, we identified and kinetic-modelled the efficiency of a new mercury-free radiation technology: microplasma UV, which radiates around proteins' UV-absorption and decomposition peak with unique spectral power distributions. Surrogates for challenging microorganisms were studied: Escherichia coli (E. coli) bacterium that contains nucleic acid reactivation proteins, and bacteriophage-MS2 virus that possesses viral proteins responsible for protecting nucleic acid (capsid) and initiating infection (maturation). The microplasma UV lamp photons, at wavelengths below 240 nm, induced nucleic acid repair-deficiency disorder and enhanced inactivation of viral infectivity. Both studied microplasma UV sources presented higher germicidal efficiency for MS2 and significantly lower repair for E. coli compared with the standard values reported for mercury UVC lamps and UVC light emitting diodes (UVC-LEDs) in the literature. The reactive oxygen 2 species were found to not play a role in this enhancement. The present results introduce promising UV sources for efficient and long-lasting microbial inactivation, thereby paving the way toward sustainable disinfection systems.
... E. coli P36 is a non-pathogenic and kanamycin resistant strain that was isolated from spinach (Warriner, Ibrahim, Dickinson, Wright, & Waites, 2003) and selected due to its slightly higher resistance to UV-C light at 253.7 nm (D value in saline = 4.8 mJ cm − 2 ; data not shown) compared to pathogenic E. coli O157:H7 (D values in water = 0.4 -3.5 mJ cm − 2 ) (Haji Malayeri, Mohseni, Cairns, & Bolton, 2016). The bacterium was stored in glycerol stock for long term storage at -80 • C. Subsequent growth in 45 mL of TSB at 37 • C overnight was seeded using loop inoculation. ...
... The effect of food matrices on the stability of microorganisms during UV treatment is another possible factor. For similar reason, the delivered fluence (23.2 mJ cm − 2 ) reported to achieve a > 5 log reduction of E. coli P36 was also slightly higher than those previously reported for other E. coli strains, including O157:H7, in other media which ranges from 1.5 to 17 mJ cm − 2 (Haji Malayeri et al., 2016;Sommer, Lhotsky, Haider, & Cabaj, 2000;Yaun, Sumner, Eifert, & Marcy, 2003). Overall, the D-value for E. coli P36 in kale juice (4.0 mJ cm − 2 ) was within the range of most other reported E. coli strains (1 to 7 mJ cm − 2 ) (Chevrefils, Caron, Wright, & Sakamoto, 2006). ...
Article
Ultraviolet–C (UV–C) light is a non–thermal method for improving the safety and shelf-life of cold–pressed juices with minimal impact on quality and nutrition. Most previous studies have investigated fruit juices as opposed to particulate dense leafy green juices with very low UV transmittance (UVT). Pure kale juice is a common juice ingredient and represents the worst-case scenario in terms of low UVT green juices. This study validated the use of continuous benchtop UV–C treatment at 253.7 nm for 5-log reduction of non–pathogenic Escherichia coli P36 in kale juice. An average absorbed fluence of 108.3 mJ cm–2 resulted in a 5.8 log reduction of E. coli P36. At a fluence comparable to that reported for commercial juice processing (74.0 mJ cm–2), kale juice exhibited a decrease in absorption coefficient, while sedimentation, supernatant browning and pectin methylesterase activity increased with no effect on the chlorophyll content, colour, viscosity or antioxidant content.
... Due to these absorption features by proteins, other types of damage can occur, such as the disruption of the cell membrane and consequently cell death or the denaturation of the capsid proteins in viruses with the infection prevention. Although it is known that this kind of UVC radiation has an inactivating effect on all microorganisms and viruses, all pathogens require different UVC irradiation doses for successful inactivation [15,23]. Anyway the inactivation rate seems to be independent of the pathogen concentration [24]. ...
... There is often some discrepancy among the inactivation doses for the same pathogen since methods and test set-ups are not standardized. Some works list the constant rates [85] but more often the measurements report the doses for one or more logarithmic inactivation rates [23] and the "k" constant must be retrieved. Regarding the case of SARS-Cov 2, a review on coronavirus family inactivation doses and experimental data comparisons on SARS-Cov 2 [42,88,89] agree that about 3-4 / 2 are sufficient to produce at least a log3 inactivation rate. ...
Preprint
Full-text available
The transmission of airborne pathogens represents a major issue to worldwide public health. Ultraviolet light irradiation can contribute to the sanification of air to reduce the pathogen transmission. This study concerns the design of a compact filter for airborne pathogen inactivation by means of UV-C LED sources, whose effective irradiance is enhanced thanks to high reflective surfaces. Ray-tracing and computational fluid dynamic simulations are both used to model the device and to maximize the performance inside the filter volume. Simulations foresee the inhibition of SARS-Cov 2 also in the case of high air fluxes. This study demonstrates that current available LED technology is effective for air sanification purposes.
... Different reviews of the history of UVGI [14,15] report on the available UV sources; moreover, the mechanisms of pathogen inactivation by UV light have been investigated in detail [16][17][18][19][20]. Although it is known that this kind of UVC radiation has an inactivating effect on all microorganisms and viruses, all pathogens require different UVC irradiation doses for successful inactivation [14,21] and the inactivation rate depends on the irradiation wavelength [22]. ...
... There is often some discrepancy between the inactivation doses for the same pathogen since methods and test set-ups are not standardized. Some studies list the constant rates k [77] but more often the measurements report the doses for one or more logarithmic inactivation rates [21] and the "k" constant must be retrieved. Regarding the case of SARS-Cov 2, a review of coronavirus family inactivation doses and experimental data comparisons on SARS-Cov 2 [36,80,81] agree that about 3-4 mJ/cm 2 are sufficient to produce at least a log3 inactivation rate. ...
Article
Full-text available
The transmission of airborne pathogens represents a major threat to worldwide public health. Ultraviolet light irradiation can contribute to the sanification of air to reduce the pathogen transmission. We have designed a compact filter for airborne pathogen inactivation by means of UVC LED sources, whose effective irradiance is enhanced thanks to high reflective surfaces. We used ray-tracing and computational fluid dynamic simulations to model the device and to maximize the performance inside the filter volume. Simulations also show the inhibition of SARS-Cov-2 in the case of high air fluxes. This study demonstrates that current available LED technology is effective for air sanification purposes.
... As mudanças no ambiente de trabalho e a revolução tecnológica impõem às organizações a necessidade de se tornarem de forma sustentável, aperfeiçoando a qualidade do seu funcionamento, com o objetivo de melhoria contínua (Perdigoto, 2012). A radiação ultravioleta (UV) tipo C é um conhecido desinfetante do ar, das superfícies e da água, que pode ajudar a atenuar o risco de contrair uma infeção (Malayeri, Mohseni, Cairns, & Bolton, 2018) e tem sido amplamente utilizado há mais de 40 anos (Persily, et al., 2017). Todas as bactérias e vírus testados até à data respondem à desinfeção por UV-C (Malayeri, Mohseni, Cairns, & Bolton, 2018), e recentemente, em plena Pandemia COVID-19, a eficácia desta gama de radiação foi testada em laboratório, tendo sido desativada uma grande percentagem de vírus SARS-CoV-2, numa superfície com um determinado tempo de exposição. ...
... A radiação ultravioleta (UV) tipo C é um conhecido desinfetante do ar, das superfícies e da água, que pode ajudar a atenuar o risco de contrair uma infeção (Malayeri, Mohseni, Cairns, & Bolton, 2018) e tem sido amplamente utilizado há mais de 40 anos (Persily, et al., 2017). Todas as bactérias e vírus testados até à data respondem à desinfeção por UV-C (Malayeri, Mohseni, Cairns, & Bolton, 2018), e recentemente, em plena Pandemia COVID-19, a eficácia desta gama de radiação foi testada em laboratório, tendo sido desativada uma grande percentagem de vírus SARS-CoV-2, numa superfície com um determinado tempo de exposição. Assim, a radiação UV-C pode desempenhar um papel importante na estratégia de proteção do ambiente e pessoas . ...
... As there is no generally accepted protocol to assess the UV-C doses needed to inactivate different bacteria in aerosols, data on the necessary dose for inactivation varies quite drastically, even for E. coli K-12 one of the most used model organisms. For example Malayeri et al. lists the UV-C dose needed for 1 log reduction in K-12 E. coli as between 1.1 and 7.8 mJ cm -2 , derived from multiple sources [21] . Generally again, such data is not available for aerosolized bacteria which will most likely be more vulnerable given that less water is surrounding and protecting them by absorbing UVlight. ...
... The copyright holder for this this version posted December 17, 2021. ; safely inactivate spores of Aspergillus spp. or Bacillus spp. as those are described to generally require doses >20 mJ cm -2 to be inactivated by at least one order of magnitude [21] . ...
Preprint
Full-text available
Background: The SARS-CoV-2 pandemic demonstrated the vulnerability of our societies to aerosol transmitted pathogens. With no less than 260mio known cases and >5mio deaths, SARS-CoV-2 is a global catastrophe leading to human and economic losses unprecedented in recent history. Thus, effective methods to limit the spread of aerosol transmitted pathogens are needed. Universal masking and curfew laws are effective but no permanent solution. Methods: A mass producible LED light source emitting homogeneous parallel UV-C light was used as a light-barrier to block the spread of infectious aerosols. In an aerosol test channel, Gram-negative and Gram-positive bacteria as well as coronavirus were nebulized and inactivation rates were determined. Findings: With air speeds of 0.1ms-1 an exposure time of 1s in the UV-C light is obtained. Reduction in CFU for E. coli was >3log10 and for S. aureus ~2.8log10. Plug-forming-units of the murine coronavirus (Mouse Hepatitis Virus, MHV) were reduced by about 3log10. Interpretation: The concept of a UV-C light barrier to ward off infectious aerosols if feasible and possible with a light element as described here. Coupled with sensor based activation/deactivation, such a technology could greatly reduce the transmission rates of aerosol transmitted pathogens while not disturbing natural human behaviour. This is an interesting technology allowing a new normal in societies after/with SARS-CoV-2.
... The results of the present study demonstrated that Biosept Home© UV-C is effective in reducing microorganisms both in vitro conditions and in healthcare environments. To reduce 99.99% of the bacteria used in the experiment, a light dose between 8 and 13 mJ/cm 2 is required [23], or much lower than the one used (0.912 J/cm 2 ). However, the dose used was not sufficient to completely reduce the yeast Candida albicans. ...
Article
Background Surface decontamination of hospital environments is essential to ensure the safety of health professionals and patients. This process is usually performed through active chemicals substances with high toxicity, and new decontamination technologies that do not leave residues have been currently used, such as UV-C light. Thus, the objective of the present study is to evaluate the effectiveness of a portable UV-C light device on the viability of standard pathogenic strains and other microorganisms isolated from different surfaces of a public health hospital. Methods In vitro decontamination was performed by applying Biosept Home© UV-C to Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica and Candida albicans. In real conditions, the application was made on different surfaces of a hospital. The device used in the experiment haa a 254 nm UV-C light and a radiation intensity of 45.6 mW/cm² over a distance of 1 cm from the surfaces. The light dose was 0.912 J/cm² for 20 seconds of application in both conditions (in vitro and hospital). Results After in vitro decontamination with UV-C light no bacterial growth was observed, demonstrating 100% of bacterial inactivation under the conditions tested. Additionally, there was a reduction of approximately 4 logs for the yeast C. albicans. In all hospital surfaces, the number of colonies of microorganisms was significantly reduced after the procedure. Conclusion The results suggest that Biosept Home© UV-C is efficient and constitutes a promosing alternative for implementing disinfection protocols in hospitals and clinics.
... The fluences required to reduce the viable counts by 1, 2 or 3 orders of magnitude at the start of the irradiation were estimated to be 62, 76 and 89 J m − 2 , respectively. Comparing these values with data reported for E. coli irradiated with low pressure mercury lamps [11] , bacterial inactivation resembles the effects described for the strains ATCC 25922 [12] , ATCC 11229 [13] , O26 [14] and ATCC 15597 [15] . Conversely, inactivation of other strains such as ATCC 11775 [15] and K12 (DSM498) [16] seems to require considerably lower fluences, probably due to the characteristics of these strains and/or the physiological conditions of the cells during the assays. ...
Article
Full-text available
Survival curves for bacteria exposed to germicidal radiation (254 nm) usually exhibit a decreased slope at high doses, because bacterial populations contain a small proportion of cells able to tolerate the effects of the radiation. These cells could survive due to external shielding by aggregation or association with inert particles. However, it has been proposed that transient and reversible phenotypic changes modifying UV susceptibility also occur and lead to a phenomenon of persistence. Using Escherichia coli as a model organism, and comparing the effects of continuous exposures to those of irradiations separated by incubations in the dark, we found that in most of the survivors to high UV doses, the condition conferring tolerance (possibly self-aggregation) is transient and reversible, as would be expected in a persistent sub-population. Splitting the irradiations into two exposures reduced viable counts to the detection limit (6.32 orders of magnitude) under conditions in which continuous irradiations produced a reduction no greater than 4 orders of magnitude. In those processes where it is feasible, UV dose fractionation could improve the effectiveness of disinfection by ultraviolet radiation.
... Por ejemplo, los huevos de gusanos parásitos poseen una alta capacidad de resistir a la radiación UV, en cambio los protozoos como Giardia y Cryptosporidium son altamente susceptibles al UV (Hijnen et al, 2006). El bacteriófago T4 es el virus con mayor susceptibilidad conocida hasta ahora, el cual es alrededor de 75 veces más susceptible que el virus más resistente conocido (Infectious Pancreatic Necrosis Virus, IPNV), ambos bajo radiación UV de 254 nm (Malayeri et al. 2016). Típicamente las bacterias son altamente susceptibles a la radiación UV, aunque extremófilos como el D. radiodurans pueden ser unos cuantos ordenes de magnitud más resistentes (Pogoda 2005). ...
Article
Full-text available
La luz ultravioleta (UV) puede ser producida de manera natural y artificial. • El UV puede ser subdividido en varias categorías, incluyendo UV-A, UV-B, UV-C, y Vacuum UV (UV de vacío). Cuanto menor es la longitud de onda, mayor es la energía del fotón UV. • La luz UV es un desinfectante efectivo, que rompe los enlaces que forman la estructura del genoma de los microorganismos. Este daño inhibe los procesos normales de replicación y reparación, esto hace posible que las infecciones puedan ser prevenidas. • La capacidad de la luz UV para inactivar microorganismos (incluyendo virus) depende de: la intensidad (irradiancia) de la fuente de luz UV, la distancia entre la fuente de luz y el objetivo a desinfectar, el tiempo de exposición, la influencia del aire, agua o entidad en el ambiente que pueda disminuir la propagación de la energía UV, la susceptibilidad de los microorganismos a la radiación UV y la longitud de onda aplicada.
... For instance, a 254 nm UV dose of 10 mJ cm −2 can lead to more than 99.99% (4-log) elimination of E. coli bacteria yet less than 70% reduction of MS2 virus (0.5log). 82 Hence, scientifically speaking, the performance of a UV disinfector, either for air or surface, should be claimed based on benchmark microbes, and a general claim such as "99.99% of all germs" is meaningless. ...
Article
Full-text available
The global health-threatening crisis from the COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), highlights the scientific and engineering potentials of applying ultraviolet (UV) disinfection technologies for biocontaminated air and surfaces as the major media for disease transmission. Nowadays, various environmental public settings worldwide, from hospitals and health care facilities to shopping malls and airports, are considering implementation of UV disinfection devices for disinfection of frequently touched surfaces and circulating air streams. Moreover, the general public utilizes UV sterilization devices for various surfaces, from doorknobs and keypads to personal protective equipment, or air purification devices with an integrated UV disinfection technology. However, limited understanding of critical UV disinfection aspects can lead to improper use of this promising technology. In this work, fundamentals of UV disinfection phenomena are addressed; furthermore, the essential parameters and protocols to guarantee the efficacy of the UV sterilization process in a human-safe manner are systematically elaborated. In addition, the latest updates from the open literature on UV dose requirements for incremental log removal of SARS-CoV-2 are reviewed remarking the advancements and existing knowledge gaps. This study, along with the provided illustrations, will play an essential role in the design and fabrication of effective, reliable, and safe UV disinfection systems applicable to preventing viral contagion in the current COVID-19 pandemic, as well as potential future epidemics.
... UV inactivates a broad spectrum of microorganisms by damaging the DNA or RNA and thereby prevents and/or alters cellular functions and replication . UV-C inactivation of various microorganisms such as pathogenic bacteria, spores, protozoa, algae and viruses has been reported (Malayeri et al., 2016;Bhullar et al., 2019;Gopisetty et al., 2019;Pendyala et al., 2019Pendyala et al., , 2020Patras et al., 2020). Because UV inactivation studies with SARS-CoV-2 requires specifically trained and skilled personnel working under biosafety level 3 (BSL-3) laboratory containment conditions, the use of surrogate coronaviruses has the potential to cross these hurdles for experimental validation of designed UV systems. ...
Article
Full-text available
Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2) is responsible for the COVID-19 pandemic that continues to pose significant public health concerns. While research to deliver vaccines and antivirals are being pursued, various effective technologies to control its environmental spread are also being targeted. Ultraviolet light (UV-C) technologies are effective against a broad spectrum of microorganisms when used even on large surface areas. In this study, we developed a pyrimidine dinucleotide frequency based genomic model to predict the sensitivity of select enveloped and non-enveloped viruses to UV-C treatments in order to identify potential SARS-CoV-2 and human norovirus surrogates. The results revealed that this model was best fitted using linear regression with r 2 = 0.90. The predicted UV-C sensitivity (D 90-dose for 90% inactivation) for SARS-CoV-2 and MERS-CoV was found to be 21.5 and 28 J/m 2 , respectively (with an estimated 18 J/m 2 obtained from published experimental data for SARS-CoV-1), suggesting that coronaviruses are highly sensitive to UV-C light compared to other ssRNA viruses used in this modeling study. Murine hepatitis virus (MHV) A59 strain with a D 90 of 21 J/m 2 close to that of SARS-CoV-2 was identified as a suitable surrogate to validate SARS-CoV-2 inactivation by UV-C treatment. Furthermore, the non-enveloped human noroviruses (HuNoVs), had predicted D 90 values of 69.1, 89, and 77.6 J/m 2 for genogroups GI, GII, and GIV, respectively. Murine norovirus (MNV-1) of GV with a D 90 = 100 J/m 2 was identified as a potential conservative surrogate for UV-C inactivation of these HuNoVs. This study provides useful insights for the identification of potential non-pathogenic (to humans) surrogates to understand inactivation kinetics and their use in experimental validation of UV-C disinfection systems. This approach can be used to narrow the number of surrogates used in testing UV-C inactivation of other human and animal ssRNA viral pathogens for experimental validation that can save cost, labor and time.
... However, exposure to these lamps has been associated with health risks, which mainly involve damage to the eyes and skin [81,82]. Nevertheless, recent evidences suggested that UV-C at 222 nm exhibited germicidal activity [83][84][85], but inflicted no damage on the eyes and skin of mice [86][87][88]. These data are still preliminary and further research is needed to ascertain the safety of UV light at 222 nm, especially its potential long-term effects on human health. ...
Article
Full-text available
SARS-CoV-2 is a single-stranded RNA virus classified in the family Coronaviridae. In this review, we summarize the literature on light-based (UV, blue, and red lights) sanitization methods for the inactivation of ssRNA viruses in different matrixes (air, liquid, and solid). The rate of inactivation of ssRNA viruses in liquid was higher than in air, whereas inactivation on solid surfaces varied with the type of surface. The efficacy of light-based inactivation was reduced by the presence of absorptive materials. Several technologies can be used to deliver light, including mercury lamp (conventional UV), excimer lamp (UV), pulsed-light, and light-emitting diode (LED). Pulsed-light technologies could inactivate viruses more quickly than conventional UV-C lamps. Large-scale use of germicidal LED is dependent on future improvements in their energy efficiency. Blue light possesses virucidal potential in the presence of exogenous photosensitizers, although femtosecond laser (ultrashort pulses) can be used to circumvent the need for photosensitizers. Red light can be combined with methylene blue for application in medical settings, especially for sanitization of blood products. Future modelling studies are required to establish clearer parameters for assessing susceptibility of viruses to light-based inactivation. There is considerable scope for improvement in the current germicidal light-based technologies and practices.
... Hasta el momento, se conoce que en sistemas con agua existe una atenuación de la radiación UV, por lo que la dosificación para desinfección requiere niveles 10 veces más altos de lo que se necesita para desinfección del aire. Lo que hace que los parámetros de desinfección de aire, sea experimental y un tema de importante estudio y parametrización para futuras aplicaciones, ya que es difícil estimar la eficiencia de esta técnica en un ambiente no controlado [18][19]. ...
Article
En este trabajo se presentan criterios que permiten estimar parámetros de desinfección mediante el uso de luz ultravioleta UV-C de onda corta, en agua, aire y superficies. Se indican métodos para evaluar la dosificación en función de la potencia de la lámpara empleada. Este tipo de estrategia permiten resultados de hasta 99.9% de desinfección, inactivando diferentes tipos de microorganismos. Estas referencias sirven de base para el diseño de dispositivos de utilidad en la presente emergencia por COVID-19, cuyo origen, al ser viral, es susceptible al mismo método de desinfección debido al proceso de dimerización del ADN, donde el daño producido en la estructura celular, afecta la capacidad de reproducción y de funcionalidad. Palabras Clave: luz UV-C o germicida, desinfección UV, dimerización del ADN. Referencias [1]R. Wallace, M. Ouellette and J. Jean, "Effect of UV‐C light or hydrogen peroxide wipes on the inactivation of methicillin resistant Staphylococcus aureus , Clostridium difficile spores and norovirus surrogate", Journal of Applied Microbiology, vol. 127, no. 2, pp. 586-597, 2019. [2]J. Vargas, "Efecto de la radiación gamma sobre las características físico - químicas, sensoriales y microbiológicas en páprika en polvo (Capsicum annuum L.)", Revista ECIPeru, pp. 68-71, 2019. [3]M. Ángeles García y P. Fernández, "Luz ultravioleta e inmunidad", Piel, vol. 21, no. 8, pp. 367-368, 2016. [4]W. Pachuau y R. Tiwari, "(Invited) Deep Ultraviolet Light Emitting Diodes: Physics, Performance, and Applications", ECS Meeting Abstracts, 2014. [5]W. Kowalski, Ultraviolet Germicidal Irradiation Handbook, 5th ed. Berlin: Springer Berlin, 2014, pp. 1-13. [6]W. Kowalski, Ultraviolet Germicidal Irradiation Handbook, 5th ed. Berlin: Springer Berlin, 2014, pp. 17-47. [7]"Germicidal Ultraviolet (GUV)", Media.ies.org, 2020. [En línea]. Disponible en: https://media.ies.org/docs/standards/IES%20CR-2-20-V1a-20200507.pdf. [Último acceso: 16 de junio de 2020]. [8]J. Bolton y C. Cotton, The ultraviolet disinfection handbook, 3rd ed. Denver, Colo.: American Water Works Association, 2008, pp. 13-33. [9]W. Kowalski, Ultraviolet Germicidal Irradiation Handbook, 5th ed. Berlin: Springer Berlin, 2014, pp. 8-9. [10]P. Aguirre, J. García y R. Mujeriego Sahuquillo, "Desinfección con cloro y luz UV en un proceso convencional de regeneración de agua", Ingeniería del agua, vol. 11, no. 1, p. 75, 2004.
... In recent years, experimental studies have been performed to analyze the effect of UV-LEDs on various microorganisms [9,15,[20][21][22]. Due to the high cost and long time associated with conducting experiments, the computational fluid dynamics (CFD) can be an excellent alternative to study this emerging technology. ...
Article
Chlorination has been the traditional method of water disinfection. With the advent of new technologies and significant issues encountered in chlorination, physical methods gradually prevailed. Ultraviolet (UV) radiation technology is a physical disinfection method that has been improved rapidly in recent years. This technology, mainly based on UV mercury lamps, has excellent potential to inactivate microorganisms in water. However, UV lamps are fragile and may cause the leakage of mercury into the environment. As the extension of visible light emitting diodes (LED) progress in solid-state physics, the nature-friendly technology of UV-LEDs has emerged. This paper analyzes the performance of cylindrical water disinfection UV-LED photoreactors made of UV reflective materials using computational fluid dynamics (CFD). The response surface methodology (RSM) is used for shape optimization of the photoreactors working with one UV-LED at the flow rate of liter per minute (LPM). Typical configurations including the U-, L-, and S-shaped are examined. The analyses provide the optimal radius and length of the photoreactors for different configurations. The performance of photoreactors can be enhanced by more than 1-Log of E. Coli by choosing the appropriate length and radius for each configuration. Also, the choice of configuration and LED location may affect the performance up to 2-Log of E. Coli. Our results show that the U- and S-shaped photoreactors can outperform the L-shaped for photoreactors made of UV reflective materials. The right choice of length, radius, and LED location can lead to 4-Log of E. Coli for a S-shaped photoreactor with a single 25 mW UVC-LED.
... Various strains of coronavirus, such as MERS-CoV and SARS-CoV, are also inactivated effectively by UV-C. [78,79] Since the emergence of COVID pandemic, there has been an immediate interest in experimenting the efficacy of using UV-C for preventing the spread of the COVID. The SARS-CoV-2 remains viable in aerosols for various durations on different surfaces. ...
Article
Artificial intelligence (AI) has a great impact on our daily living and makes our lives more efficient and productive. Especially during the coronavirus disease (COVID-19) pandemic, AI has played a key role in response to the global health crisis. There has been a boom in AI innovation and its use since the pandemic. However, despite its widespread adoption and great potential, most people have little knowledge of AI concepts and realization of its potential. The objective of this white paper is to communicate the importance of AI and its benefits to society. The report covers AI applications in six different topics from medicine (AI deployment in clinical settings, imaging and diagnostics, and acceleration of drug discovery) to more social aspects (support older adults in long-term care homes, and AI in supporting small and medium enterprises. The report ends with nine steps to consider for moving forward with AI implementation during and post pandemic period. These include legal and ethical data collection and storage, greater data access, multidisciplinary collaboration, and policy reform.
... De plus, il est connu que la sensibilité au rayonnement UV-C (et les capacités de réparation) est variable suivant les espèces/souches (Malayeri et al. 2016). ...
Thesis
Les biofilms bactériens posent de nombreux problèmes dans les domaines de la santé, de l'agro-alimentaire et de différents secteurs industriels. Un biofilm est une communauté de microorganismes fixés à une surface, maintenus et protégés par une matrice extracellulaire constituée de différents polymères. L'éradication de ces biofilms passe traditionnellement par l'utilisation de traitements chimiques ou thermiques. Récemment, des techniques physiques à faible impact environnemental tels que les jets de plasma froid et les diodes électroluminescentes (LED) émettant dans les UV ont été étudiées pour la décontamination/stérilisation de surfaces. Du fait de la complexité structurale des biofilms et de la diversité des paramètres physiques de ces dispositifs, l'essor de ces technologies innovantes et durables pour des applications anti-biofilms demandent de nombreuses améliorations méthodologiques permettant la quantification ou la qualification de leurs effets biologiques. Lors de cette étude, deux souches bactériennes ayant des caractéristiques pariétale et matricielle différentes ont été choisies : Leuconostoc citreum NRRL B-1299 (Gram+, production contrôlable d'une matrice exopolysaccharidique) et Pseudomonas aeruginosa ATCC 15442 (Gram-, matrice complexe riche en protéines et ADN). Les systèmes physiques utilisés correspondent à un prototype de jet de plasma froid qui génère des espèces réactives de l'azote (RNS) et de l'oxygène (ROS) et à un dispositif LED émettant dans les UV-C à 280 nm. Dans un premier temps, une méthodologie a été définie afin d'obtenir des biofilms aériens (sur des membranes) de façon reproductible et standardisée en termes de densité cellulaire et de matrice extracellulaire. L'effet biocide des traitements LED UV-C et jet de plasma appliqués, évalué par dénombrement bactérien classique, a été comparé entre des cellules déposées sur membrane et des biofilms de 24 heures. Les résultats du traitement au jet de plasma ont permis d'émettre l'hypothèse d'un rôle protecteur de la matrice extracellulaire, en lien avec sa composition (quantité et nature des polymères). Dans le cas du traitement LED UV-C, et en lien avec les propriétés d'absorbance des composants matriciels, l'effet protecteur de la matrice a été démontré pour P. aeruginosa. Un autre aspect de ces travaux a concerné l'exploitation de méthodes permettant d'évaluer de façon plus précise les effets des traitements physiques sur la composante cellulaire des biofilms. La méthode qPCR de viabilité (ou PMA/EMA-qPCR) n'a pas permis d'aboutir à une quantification satisfaisante des cellules de P. aeruginosa ou de L. citreum. En revanche, une méthode basée sur la réduction métabolique de la résazurine par les cellules a pu être proposée. Ces études contribuent à renseigner sur l'importance du paramètre de densité cellulaire et de caractérisation de la matrice extracellulaire dans l'évaluation de méthodes physiques d'éradication des biofilms bactériens et soulignent la nécessité de continuer à développer des outils d'analyses adaptés à cette problématique.
... These treatment acts by causing damage on DNA replication [69]. Inactivation with UV is determined by the energy per unit area on a period of time exposure and it is commonly expressed in mJ/cm 2 [70]. UV treatment at doses of 250 to 300 mJ/cm 2 has demonstrated the ability to eliminate >95% of Pythium spp. in hydroponics [71]. ...
Article
Full-text available
Aquaponics is an alternative method of food production that confers advantages of biological and economic resource preservations. Nonetheless, one of the main difficulties related to aquaponics systems could be the outbreak and dissemination of pathogens. Conventional treatments need to be administrated carefully because they could be harmful to human, fish, plants and beneficial microorganisms. Aquaponics practitioners are relatively helpless against plant diseases when they occur, especially in the case of root pathogens. Biological control agents (BCAs) may be an effective alternative to chemical inputs for dealing with pathogens of plants under aquaponics systems. Research of BCAs on aquaponics systems is limited, but there are numerous publications on the use of BCAs to control plant pathogens under soilless systems which confirm its potential use on aquaponics systems. The present review summarized the principal plant pathogens, the conventional and alternative BCA treatments on aquaponics systems, while considering related research on aquaculture and soilless systems (i.e., hydroponic) for its applicability to aquaponics and future perspectives related to biological control. Finally, we emphasized the case that aquaponics systems provide relatively untapped potential for research on plant biological control agents. Biological control has the potential to reduce the perturbation effects of conventional treatments on microbial communities, fish and plant physiology, and the whole function of the aquaponics system.
... Though the virus survives as aerosols and on environmental surfaces for various durations of time, it can easily be inactivated by several types of physical and chemical disinfection methods (Mackenzie 2020) including UVC disinfection (Malayeri et al. 2020), dry-heat sterilization (Rutala and Weber 2019) and using biocidal agents (Lei Liao 2020). The Centre for Disease Control and Prevention (CDC) has also recommended these disinfection methods for bacteria and viruses involving protein denaturation and DNA/RNA disruption (Guideline for disinfection and sterilization in healthcare facilities 2008). ...
Article
COVID-19 (SARS-CoV-2) is causing a huge concern to the global population due to its highly contagious properties. The SARS-CoV-2 is a new variant in the coronavirus family. The world is focussing on several methods to battle against this novel corona virus, including control of its spread. In this context, ARCI has quickly made efforts to develop disinfection systems including a UVC-based disinfection trolley, honeycomb air heater and a fogging chamber using UVC germicidal lamps, dry heat sterilization and HOCl-based chemical disinfectant to provide rapid and effective inactivation of microorganisms causing the pandemic. These systems have been successfully deployed at different hospitals for their validation.
... Non-pathogenic and kanamycin-resistant E. coli P36 [20] was used as a model organism to inoculate saline as well as juices and beverages in order to measure log count reduction following treatment. This strain was selected due to a slightly higher overall resistance to UV-C light at 253.7 nm (1-log 10 reduction in saline = 4.8 mJ cm −2 ; data not shown) in comparison to pathogenic E. coli O157:H7 (1-log 10 reduction in water = 0.4-3.5 mJ cm −2 ) (Adel Haji [21]). Growth and enumeration of E. coli P36 were previously described by Pierscianowski et al. [22]. ...
Article
Full-text available
Recent advancements in ultraviolet light-emitting diodes (UV-LEDs) have allowed for their successful integration into continuous disinfection reactors including small-scale systems designed for low UV transmission (UVT) applications. This study characterized the performance of the first commercially available benchtop continuous-flow multiple-wavelength UV-LED system used for the treatment of juices and beverages in thin film. Three beverages (coconut water, blue lemonade, and pink lemonade), two juices (green juice blend and beet juice blend), and saline solution were inoculated with a non-pathogenic Escherichia coli indicator organism and treated at 281 nm. The volume averaged fluence delivered to the samples per pass ranged between 1.6 and 11.6 mJ cm−2 and was dependent on their absorption coefficients which ranged from 0.67 to 26.9 cm−1. Microbial inactivation ranging from 4.2 to 7.2 log10 was achieved within a reasonable number of passes or treatment time in pinkand blue lemonade, coconut water, and saline solution which corresponded to an absorption coefficient below 6 cm−1 (UVT = 0.3%). Other than in beet juice blend, which had the highest absorption coefficient, a 1-log10 reduction fluence value in the range of other E. coli strains (previously reported in water) was reported (1.9–5.8 mJ cm−2). These results also suggest that the continuous-flow UV-LED system can be used to investigate inactivation kinetics and effects on nutritional and quality parameters at multiple wavelengths following treatment of low UVT water samples and highUVT juices and beverages with absorption coefficients up to 10–12 cm−1 (4.6e−3 to 6.3e−6% UVT).
... Dentre essas tecnologias a exposição à luz ultravioleta (UV-C) tem se mostrado eficiente contra diferentes vírus, bactérias e fungos (Haji Malayeri, et al., 2016;Buonanno, et al., 2020). Este método não utiliza produtos químicos, é altamente eficiente no controle de micro-organismos (Raeiszadeh & Adeli, 2020). ...
Article
Full-text available
A Pandemia COVID-19, causada pelo vírus SARS-COV-2,evidenciou a necessidade de desenvolvimento de métodos seguros e economicamente viáveis para a realização de desinfecções em escala comercial e doméstica. Os coronavírus são mais suscetíveis à radiação UV-C do que fungos e bactérias e diversos estudos relacionados à eficiência da UVC contra o vírus causador da COVID-19 já foram realizados utilizando micro-organismos substitutos. Desta forma, este estudo buscou o desenvolvimento de um dispositivo acessível a usuários leigos para utilização em materiais que não podem ser submetidos a métodos convencionais de eliminação de micro-organismos (desinfecção química ou térmica). Esta pesquisa propôs a produção e validação de um dispositivo emissor de radiação UV-C portátil para a desinfeção de substratos suscetíveis a contaminação por bactérias, fungos e vírus patogênicos. O dispositivo foi desenvolvido a partir de materiais acessíveis a grande parte das empresas e população. Em seguida foi realizada a validação da eficiência do dispositivo através da exposição de culturas microbianas (bactéria Gram positiva, negativa e levedura) em diferentes intervalos de tempo. O dispositivo foi desenvolvido plenamente a partir de materiais de baixo custo e acessíveis. Todos os micro-organismos testados (Candida albicans, Staphylococcus aureus e Escherichia coli) foram eliminados do meio de cultura com menos de 20 min. de exposição. O dispositivo desenvolvido neste estudo pode ser construído por boa parte das empresas e população. O dispositivo se mostrou eficaz para reduzir o risco de contágio de diferentes micro-organismos patogênicos, sugerindo sua efetividade contra SARS-COV-2 causador da pandemia COVID-19.
... Dentre essas tecnologias a exposição à luz ultravioleta (UV-C) tem se mostrado eficiente contra diferentes vírus, bactérias e fungos (Haji Malayeri, et al., 2016;Buonanno, et al., 2020). Este método não utiliza produtos químicos, é altamente eficiente no controle de micro-organismos (Raeiszadeh & Adeli, 2020). ...
Article
Full-text available
A Pandemia COVID-19, causada pelo vírus SARS-COV-2, evidenciou a necessidade de desenvolvimento de métodos seguros e economicamente viáveis para a realização de desinfecções em escala comercial e doméstica. Os coronavírus são mais suscetíveis à radiação UV-C do que fungos e bactérias e diversos estudos relacionados à eficiência da UVC contra o vírus causador da COVID-19 já foram realizados utilizando micro-organismos substitutos. Desta forma, este estudo buscou o desenvolvimento de um dispositivo acessível a usuários leigos para utilização em materiais que não podem ser submetidos a métodos convencionais de eliminação de micro-organismos (desinfecção química ou térmica). Esta pesquisa propôs a produção e validação de um dispositivo emissor de radiação UV-C portátil para a desinfeção de substratos suscetíveis a contaminação por bactérias, fungos e vírus patogênicos. O dispositivo foi desenvolvido a partir de materiais acessíveis a grande parte das empresas e população. Em seguida foi realizada a validação da eficiência do dispositivo através da exposição de culturas microbianas (bactéria Gram positiva, negativa e levedura) em diferentes intervalos de tempo. O dispositivo foi desenvolvido plenamente a partir de materiais de baixo custo e acessíveis. Todos os micro-organismos testados (Candida albicans, Staphylococcus aureus e Escherichia coli) foram eliminados do meio de cultura com menos de 20 min. de exposição. O dispositivo desenvolvido neste estudo pode ser construído por boa parte das empresas e população. O dispositivo se mostrou eficaz para reduzir o risco de contágio de diferentes micro-organismos patogênicos, sugerindo sua efetividade contra SARS- COV-2 causador da pandemia COVID-19.
... 48,49 Furthermore, the UV fluence needed to achieve a 4-log 10 reduction in PV as obtained by our linear regression analysis is still within the range of 17−37 mJ/cm 2 reported by IUVA news. 105 This critical review did not provide distinct linear regressions for each individual paper, as was presented in the Hijnen review. 102 However, a statistical analysis using ANCOVA was performed to establish factors that might affect the inactivation rates and therefore the suggested doses required for a 4-log 10 reduction of specific viruses. ...
Article
Full-text available
Ultraviolet (UV) radiation alone or in combination with other oxidation processes is increasingly being considered for water disinfection because of stringent regulatory requirements for pathogen inactivation. To fulfill this requirement, an appropriate UV dose or fluence (mJ/cm²) is applied to combat enteric viruses in surface or treated water. There is a need for a cumulative review on the effectiveness of current and emerging UV technologies against various types of human enteric viruses. We extracted the kinetics data from 52 selected experimental studies on enteric virus inactivation using low pressure (LP-UV), medium pressure (MP-UV), UV-LED, and advanced oxidation processes (AOPs) and applied a simple linear regression analysis to calculate the range of UV fluence (mJ/cm²) needed for 4-log10 inactivation. The inactivation of adenoviruses with LP-UV, MP-UV, and UV/H2O2 (10 mg/L) required the highest fluence, which ranged from 159 to 337, 45, and 115 mJ/cm², respectively. By contrast, when using LP-UV, the inactivation of other enteric viruses, such as the Caliciviridae and Picornaviridae family and rotavirus, required fluence that ranged from 19 to 69, 18 to 43, and 38 mJ/cm², respectively. ssRNA viruses exhibit higher sensitivity to UV radiation than dsRNA and DNA viruses. In general, as an upgrade to LP-UV, MP-UV is a more promising strategy for eliminating enteric viruses compared to AOP involving LP-UV with added H2O2 or TiO2. The UV-LED technology showed potential because a lower UV fluence (at 260 and/or 280 nm wavelength) was required for 4-log10 inactivation compared to that of LP-UV for most strains examined in this critical review. However, more studies evaluating the inactivation of enteric viruses by means of UV-LEDs and UV-AOP are needed to ascertain these observations.
... Therefore, UVC light is just as novel to SARS-CoV2 as the virus is to humans. According to the International Ultraviolet Association, it is generally accepted that a dose of 40 millijoules per square centimeter of 254-nm light will kill at least 99.99% of "any pathogenic microorganism" [6,7]. ...
... For example, the relation between the quantity of the absorbed energy and the biological effect (survival, mutation frequency) is already defined for the UV light in the range of 254-320; this range is effective in destroying the molecules essential for the metabolic processes of pathogens' DNA. Regarding inactivation of Legionellae by UV-C, it was previously reported by some authors (Antopol and Ellner, 1979;Cervero-Aragó et al., 2014;Malayeri et al., 2006;Rozenberg and Lowentahl, n.d.). ...
Article
Full-text available
Legionella species are the etiological agent of Legionnaires' disease, a pathology easily contracted from water circuits and by the inhalation of aerosol droplets. This bacterium mainly proliferates in water: Legionella pneumophila is the most commonly isolated specie in water environments and consequently in water system, although further Legionella species have frequently been isolated, including Legionella dumoffii. The simultaneous presence of the two species in the water system can therefore lead to the simultaneous infection of several people, giving rise to harmful outbreaks. Ultraviolet inactivation of waterborne microorganisms offers a rapid and effective treatment technique and recently is getting more attention mostly to eliminate unsafe level of contamination. To tackle the issue, the inactivation of the two species of Legionella spp., namely L. pneumophila and L. dumoffii, by means of UV-A light emitting diodes (UV-A LED) system is explored. We used a commercially available UV-A LED at 365nm wavelength, and the UV-A dose is given incrementally to the Legionellae with a concentration of 10⁶ CFU/mL in 0.9% NaCl (aq) solution. In this study, with a UV-A-dose of 1700 mJ/cm², the log-reduction of 3-log (99.9% inactivation) for L. pneumophila and 2.1-log (99.1% inactivation) for L. dumoffii of the contaminated water are achieved. The Electrical Energy per Order (EEO) is evaluated and showed this system is more economic and efficient in comparison with UV-C and UV-B LEDs. Following the support of this preliminary study with additional tests, aiming to validate the technology, we expect this device may be installed in water plants such as cooling systems or any water purification station in either industrial or home scales to reduce the risk of this infectious disease, preventing consumers' health.
... Under irradiation with the monochromatic LED of characteristic emission at λ = 365 nm (see Fig. 3a) no inactivation was observed. Note that only UVC radiation with λ ranging at 100-280 nm has reported germicidal activity of E. coli, attaining 3-log inactivation under fluences of 9 mJ cm −2 (Malayeri et al., 2006). On the other hand, when a nano-enabled photo-anode of TiO 2 nanotubes is used, a slight inactivation of 0.4-log was observed after 5 min of irradiation. ...
Article
Portable water purification devices are needed to provide safe drinking water in rural communities, developing communities with low quality centralized water distribution, and military or recreational applications. Filtration, ultraviolet light, or chemical additives provide a spectrum of alternatives to remove pathogens from water. For the first time, we design, fabricate and demonstrate the performance of a small portable photoelectric point-of-use device, and document its performance on pathogen inactivation. The device utilizes a commercial teacup from which TiO2 nanotube photoanodes were produced in-situ and, with a small rechargeable battery powered 365 nm light emitting diode, was able to achieve 5-log inactivation of Escherichia coli in 10 s and 2.6-log of Legionella in 60 s of treatment in model water samples. Treatment of natural water achieved a 1-log bacteria inactivation after 30 s due to matrix effects. The electro-photocatalytic disinfection reactor in a kup (e-DRINK) can provide a feasible and affordable solution to ensure access to clean water. More broadly, this work demonstrates the potential for illumination to improve the efficiency of electrocatalytic surfaces.
... It was also found that direct solar illumination was much more effective for PEC due to its greater UV intensity (see Table 1). It is important to remark that UVC sources can also attain disinfection given certain doses of high-energy photons that can damage the genetic material of bacteria [66]. Thus, blank experiments are required to evaluate the bacteria inactivation of the light sources employed. ...
Article
Full-text available
Photoelectrocatalysis is a hybrid photon/electron-driven process that benefits from the synergistic effects of both processes to enhance and stabilize the generation of disinfecting oxidants. Photoelectrocatalysis is an easy to operate technology that can be scaled-up or scaled-down for various water treatment applications as low-cost decentralized systems. This review article describes the fundamentals of photoelectrocatalysis, applied to water disinfection to ensure access to clean water for all as a sustainable development goal. Advances in reactor engineering design that integrate light-delivery and electrochemical system requirements are presented, with a description of photo-electrode material advances, including doping, nano-decoration, and nanostructure control. Disinfection and cell inactivation are described using different model microorganisms such as E. coli, Mycobacteria, Legionella, etc., as well the fungus Candida parapsilosis, with relevant figures of merit. The key advances in the elucidation of bacterial inactivation mechanisms by photoelectrocatalytic treatments are presented and knowledge gaps identified. Finally, prospects and further research needs are outlined, to define the pathway towards the future of photoelectrocatalytic disinfection technologies.
... The dosage required to achieve a certain reduction in pathogen concentration, typically expressed in J/m 2 or mJ/cm 2 , is the ultraviolet fluence, or integral of irradiance with respect to time. UV-C fluence dosages have been catalogued for SARS-CoV-2 (Arguelles, 2020;Lim, 2020) and other pathogens (Malayeri, et al., 2016). The low reflectivity of most building materials in the UV-C band may protect occupants from harmful long-term exposure to ultraviolet radiation . ...
Conference Paper
Full-text available
Ultraviolet Germicidal Irradiance (UVGI) is the effective technique of inactivating disease-causing bacteria, mould spores, fungi, and viruses using ultraviolet radiation. In this study, we seek to quantify the efficacy and COVID-19 infection risk reduction achieved by UVGI in the upper unoccupied zone of a room so that we may specify the type and placement of UVGI emitters optimally. We present a computational fluid dynamics (CFD) based approach to model disinfection of aerosolized pathogens in a non-uniform ultraviolet field with mixing driven by air exchange and temperature gradients. We validate our CFD against simple calculation methods for UVGI effectiveness in well mixed spaces, and we integrate it with the Wells-Riley model of airborne infection risk to assess the relative benefit of UVGI with and against other measures. We demonstrate an order of magnitude reduction in infection risk as a result of applying UVGI, as well as the ability to quantify infection risk in non-well-mixed settings where simplified calculations methods do not apply.
... The disinfection dose-response and reaction rates for many pathogens (figure 3) have been summarized by Kowalski [12], and more recently by Gerchman et al [21] and are tabulated by the International Ultraviolet Association (IUVA) [22]. There are many sources of uncertainty in both GUV irradiance and disinfection quantification, so figure 3 does not compare absolute GUV sensitivity; rather, we include only reports in which more than one wavelength was tested, and normalize the data to a reference value at 254 nm. ...
Article
Ultraviolet light emitting diodes (UV LEDs) are one of the most promising technologies for preventing future pandemics, improving health outcomes, and disinfecting water sources. Currently available UV LEDs emitting in the conventional germicidal wavelength range (254–285 nm) have efficiencies below 5% and cost about 100 times more (per watt) than mercury vapor lamps. On the other hand, germicidal UV LEDs provide many advantages over vapor lamps including instant-on and dimmable functionality, wavelength tunability, miniaturization, and durability, and are already in widespread use for certain applications. It is expected that III-nitride based UV LEDs will soon have similar cost and efficiency to white LEDs and will become the dominant germicidal light source within this decade. Unlike vapor discharge lamps, LEDs have theoretical efficiency limits approaching 100%; the challenges to improving UV LED efficiency are not fundamental, but technological. Improvements in material quality, chemical purity, electrical conductivity, optical transparency, and fabrication technologies are needed. In this review, we outline the major challenges in each of these areas and summarize the recent advances that have enabled rapid improvements in UV LED efficiency within the past 5 years. We discuss the physical principles underlying the mechanisms of improved efficiency, and comment on likely future trends in UV LED design and commercialization.
... The original compilation was an internal document of Trojan Technologies [1]. The first revision was published in 2006 [2], and the second revision was published in 2016 [3]. Data from the previous reviews have been included here. ...
Article
Full-text available
Data concerning the sensitivity of various organisms to ultraviolet (UV) radiation exposure are very important in the design of UV disinfection equipment. This review analyzes fluence data from almost 250 studies and organizes the data into a set of recommended fluence values for specific log reductions and an appendix containing all the collected data. © 2021 National Institute of Standards and Technology. All rights reserved.
Chapter
Coronavirus disease 2019 (COVID-19) is primarily a respiratory illness, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The pandemic outbreak of SARS-CoV-2 across the world has been responsible for high morbidity and mortality, which emphasizes the role of the environment on virus persistence and propagation to the human population. Since environmental factors may play important roles in viral outbreaks, and the severity of the resulting diseases, it is essential to take into account the role of the environment in the COVID-19 pandemic. The SARS-CoV-2 may survive outside the human body from a few hours to a few days, depending upon environmental conditions, probably due to the relatively fragile envelope of the virus. The shedding and persistence of SARS-CoV-2 in the environment on animate and inanimate objects contributes to the risk of indirect transmission of the virus to healthy individuals, emphasizing the importance of various disinfectants in reducing the viral load on environmental surface and subsequently control of SARS-CoV-2 in the human population.
Article
Objective/Method : Endocavitary probes are semi-critical devices and must undergo, at least, high level disinfection (HLD) between uses. Therefore, they should be high level disinfected between uses (i.e., with a product/process that kills all forms of microbial life; bacteria, fungi, mycobacteria and virus and, in some countries, a demonstrated potential for sporicidal activity). In this study, the sporicidal activity of three common FDA cleared sterilants (CIDEX OPA Solution, SPOROX II Sterilizing & Disinfection Solution and CIDEX Activated Dialdehyde Solution) was compared with the sporicidal activity of an ultraviolet disinfection technology (Hypernova Chronos, Germitec) against Bacillus subtilis ATCC 19659 spores spread on silicone flat carriers in the presence of inorganic and organic soil. Results : The results indicate that the UV disinfection process presented within a 35 second exposure time a sporicidal efficacy substantially higher than the chemical sterilants used according to manufacturer instructions for HLD. Conclusion : This study demonstrated that even if it cannot be tested/approved as a sterilant according to AOAC 966.04, the UV unit is much more effective than usual FDA approved chemical HLD products to kill spores in real use conditions. This finding questions the relevancy of evaluating product efficacy within extended conditions giving results that could mislead users to select the most effective HLD product/process for the reprocessing of their medical devices.
Article
Full-text available
This covid pandemic has taught us the core survival instincts & foresee technological need balance while spotlighting on the ways of garbage being handled manually in countries like India by local municipality workers and not using properly sealed and hygienic practices towards waste disposal have shown significant trouble and damage. Generally, people put waste materials in dustbins that are not treated. Many hazardous and pandemic-causing diseases can be mitigated and checked by proper treating of garbage and infected sewage. Used face masks, hand gloves, Diapers, and medical waste materials which are thrown in the dustbins are hazardous and while transferring this waste to dumping yards there are possibilities of germs and viruses to spread, mutate, contract disease to the garbage handler or people working in garbage Handling section. This must be discarded immediately upon throwing in the dustbin so that the first person at the base who handles the Garbage is also mitigated from the risk of contracting the virus. Instead of Discarding used Hygienic Products or Garbage into the disposal bin, disinfecting the Garbage seems significant in breaking the chain of contamination. This paper discusses an easy-to-manufacture or modified and easy-to-use Automated UV Sterilizing Dustbin is one of the solutions to attenuate the viruses/bacteria in the initial stage of garbage handling where waste management involves manual labor in countries like India. The dustbin neutralizes all the pathogens in it and makes it safe to handle by the sanitation workers, unchecked which involves many children who live in slums and are below poverty lines.
Article
Modeling of a UV-C LED air treatment duct showed that use of highly reflective duct surfaces significantly increased microbial inactivation and minimized the impact of LED positions on inactivation levels. This result was independent of the number of LEDs used. Four wall reflection resulted in higher inactivation rates than solely side-side or top–bottom surface reflection, but beyond three reflections of intensity the number of LEDs controlled the maximum inactivation. The model consisted of a radiation routine which calculated fluence rate from LED intensities and specular surface reflection, integrated with a fluid flow routine which determined air residence time and an inactivation routine which combined microbe inactivation rate constants with fluence levels. Model predictions compared well with data from a 2-cm square test treatment system that achieved 99.9% inactivation of Staphylococcus aureus at low flow rates. These results can guide treatment system designs and expand modeling capabilities for such systems.
Article
Relevance . For over 30 years, ultraviolet bactericidal radiation has been widely used to disinfect water, air and surfaces. Currently, UV technologies are being dynamically introduced into various spheres of the national economy – industry, medicine, utilities, energy, transport, agriculture, etc. Aims of this message to present the possibilities of UV radiation for the disinfection of water, air, and surfaces. Conclusions . The task of disinfecting natural and waste waters was the driver of the development of UV technologies in the last 30 years. The scale of this task forced the world's leading institutions and lighting companies to raise the development and production of UV radiation sources (UV lamps) to a new level. In recent years, is in the usage of UV radiation for disinfection of air and air conditioning systems of buildings as a whole. Global migrations and communications of the population around the planet have aggravated the situation with the spread of infectious diseases transmitted by airborne droplets. In last decades, epidemics have ceased to be a local territorial phenomenon. A prime example is the current global COVID-19 pandemic caused by the SARS-CoV-2 coronavirus. In medicine, the highest requirements are imposed on the disinfection of air and surfaces with a high degree of disinfection. To solve this problem, it is necessary to pay special attention to modern developments in the application of UV technologies, taking into account the effective UV doses in relation to various types of microorganisms.
Article
The efficacy of UV-C light for inactivating bacteria and endospores in an opaque fluid (diluted humic acid at pH 7.2, absorbance = 13.1/cm) using an annular pilot ultra-thin film (1 mm thickness) UV system was investigated in this study. The effect of fluid flow conditions on UV dose distribution was also assessed. UV dose delivery under experimental conditions was verified and validated by a bio-dosimetry method. The results revealed that efficient UV dose distribution was achieved at turbulent flow (Re > 3960) with superior (>2.6 times) microbial inactivation efficiency compared to laminar flow (Re = 1980). Verified reduction equivalent fluence correlated well with calculated UV dose. Microbial inactivation studies at commercial relevant flow-rates (159 gal/h) showed > 5 log reduction of vegetative bacteria (E. coli ATCC 25922, S. Typhimurium ATCC 13311, L. monocytogenes ATCC 19115) and >4 log reduction of endospores (B. cereus ATCC 14579) at UV-C reduction equivalent fluence (REF) of 26 and 34 mJ/cm², respectively. Comparative operational cost analysis indicated that UV-C pasteurization was 1.3 and 14 times less costly than reported heat and HPP pasteurization, respectively.
Article
The design of efficient ultraviolet light emitting diode (UV-LED) reactors is of paramount importance for delivering a high UV dose (fluence). This is particularly critical to the disinfection of UV-resistant organisms, such as adenovirus, in continuous UV systems, given the low wall plug efficiency of UV-LEDs. The UV-LED offers reactor design flexibility, allowing to conform the reactor fluence rate to its hydrodynamics to a high degree, leading to improved design efficiency. In this study, we designed and fabricated a flow-through multi-baffle UV-LED reactor containing 18 UV-LEDs for delivering high UV fluence to a flow of water. Further, we developed a computational model for simulating the reactor performance, to fine-tune the fluence rate and hydrodynamics conformity through exploring several design concepts. The model was evaluated by experimental studies using male-specific-2 (MS2) bacteriophage and adenovirus as the model UV resistance microorganisms. The radiant field was adjusted through the LED arrangement and radiation profile modification. The reactor performance was studied under six different LED arrangements, three irradiation modes, and flow rates of 0.75, 1, and 2 L min⁻¹. Adenovirus inactivation at 1 L min⁻¹ from 1.6 logs increased to 4.1 logs through radiant field modification and enhancing the design efficiency. It was observed that the flexibility offered by UV-LEDs in adjusting the radiation pattern and hydrodynamics could lead to the design of highly-efficient reactors through positively correlating the UV fluence rate profile with the velocity filed. This study presents a detailed discussion concerning irradiation methods and provides insights applicable to UV-LED reactor design.
Research
Full-text available
This paper scrutinizes an innovative method used to sterilize the garbage with microbes on it by treating it with UV rays for a determined duration and intensities. We discussed an easy-to-manufacture or modified and easy-to-use automated UV Sterilizing Dustbin in this. It is one of the solutions to attenuate the viruses/bacteria in the initial stage of garbage handling where waste management involves manual labour in many countries. The dustbin neutralizes all the pathogens in it and makes it safe to handle by the sanitation workers or garbage collectors.
Article
UV-C processing of whole milk (WM) using a designed novel serpentine coil Dean flow system was demonstrated at flow rates of 11.88, 23.77, and 47.55 gph. Computational fluid dynamics (CFD) and biodosimetry studies were conducted to assess the flow field and fluence delivered at selected experimental flow rates. The CFD results revealed that as the flow rate increases, the ratio between average velocity to maximum velocity (Vavg/Vmax) increases from 0.58 to 0.72 and enhanced Dean effects of the fluid domain at serpentine bend locations. Delivered UV fluence rate (REF rate) was 1.54 times higher at 47.88 gph than 11.88 gph. Microbial inactivation studies showed 2.75 and 4.29 log reduction (CFU/mL) of B. cereus endospores and T1UV phage after three and two passes of WM through the system at a flow rate of 47.88 gph. UV-C irradiated WM quality analysis revealed no significant effect on lipid peroxidation and volatiles profile at REF of 60 mJ/cm². Lower electrical energy per order (EEO) value also signifies the higher electrical efficiency of the system at a flow rate of 47.88 gph.
Chapter
Surfaces contaminated with SARS-CoV-2 or other such viruses pose a grave threat to the safety of individuals. Mobile robots mounted with ultraviolet (UV) light attachments are ideal for disinfecting hospital rooms, shopping centers and other public spaces. This paper mainly discusses the steps involved in making an autonomous UV Disinfectant robot and its functionalities. The UV Disinfectant robot initially maps the environment with the help of a user and subsequently localizes itself in the map and is able to autonomously navigate to a selected location in the map. The user must select waypoints in the generated map determining the locations where disinfection is required. After the waypoint generation of a map, the robot can autonomously navigate through the map disinfecting given locations. The robot is equipped with 6 UVC lights around a central column, which is fixed to a mobile robotic platform that has required sensors. The robot can be used as a part of the regular cleaning crew and it aids in reducing the spread of infectious diseases, viruses, bacteria, and other types of harmful microorganisms in the environment. ROS framework is used to program the robot.
Article
Ultraviolet (UV) is a green and effective technique that has been widely applied in water disinfection. The reliability of UV disinfection is an important issue, in which the aim is to ensure the delivery of adequate real-time fluence in a UV reactor. Unlike chemical disinfection systems whose disinfection dose can be directly measured with disinfectant residuals, UV is a physical process and the determination of fluence is complicated in practical reactors. To date, several fluence determination methods have been developed, including conventional methods such as biodosimetry and model simulation, as well as emerging methods such as dyed microsphere method and the model-detector method. However, a systematic and comprehensive review of these methods is still needed to discuss the attributes and application scenarios of each method. In this review, we summarized the principal theories, procedures, applications, and pros/cons of these fluence determination methods. Further, the selection and application of appropriate fluence determination methods were discussed based on different purposes (e.g., feedbacks for reactor design, evidence for third-party validation, as well as on-site determination and long-term monitoring of fluence). Overall, this review could provide useful information and new insights regarding the application of current fluence determination methods to ensure the reliability of UV disinfection.
Article
The inactivation of pathogenic microorganisms in water and high transmittance liquid foods has been studied extensively. The efficiency of the process is relatively low for treating opaque liquid foods using traditional UV systems. This study evaluated the ability of UV-C light to inactivate foodborne pathogens in a simulated opaque fluid (6.5 to 17 cm⁻¹) at commercial relevant flow rates (31.70, 63.40, 95.10 gph) using a pilot-scale Dean Flow UV system. In this study, a mathematical model for the prediction of delivered fluence was developed by the biodosimetry method. The results revealed that increased Reduction equivalent fluence (REF) rates were observed with increased flow rates due to additional turbulence. The experimental and calculated REF were well correlated with the UV-C absorption coefficient range of 6.5 to 17 cm⁻¹ indicating efficient mixing in the reactor. REF scaled up linearly at experimental conditions as an inverse function of flow rate and absorption coefficient, and a linear mathematical model (R² > 0.99, p < 0.05) to predict delivered REF was developed. The model was tested and validated against independent experiments using Salmonella Typhimurium and Bacillus cereus endospores. The predicted and experimental REF values were in close agreement (p > 0.05). It is demonstrated that the developed model can predict the REF, thus microbial inactivation of microbial suspensions in simulated fluid with the absorption coefficient of 6.5 - 17 cm⁻¹ and flow rates of 31.70 - 95.10 gph. The pilot system will be field-tested against microorganisms in highly absorbing and scattering fluids.
Article
Background: The COVID-19 pandemic urges for cheap, reliable, and rapid technologies for disinfection and decontamination. One frequently proposed method is ultraviolet (UV)-C irradiation. UV-C doses necessary to achieve inactivation of high-titre SARS-CoV-2 are poorly defined. Aim: We investigated whether short exposure of SARS-CoV-2 to UV-C irradiation sufficiently reduces viral infectivity and doses necessary to achieve an at least 6-log reduction in viral titres. Methods: Using a box and two handheld systems designed to decontaminate objects and surfaces, we evaluated the efficacy of 254 nm UV-C treatment to inactivate surface dried high-titre SARS-CoV-2. Results: Drying for 2 hours did not have a major impact on the infectivity of SARS-CoV-2, indicating that exhaled virus in droplets or aerosols stays infectious on surfaces for at least a certain amount of time. Short exposure of high titre surface dried virus (3–5*10^6 IU/ml) with UV-C light (16 mJ/cm ² ) resulted in a total inactivation of SARS-CoV-2. Dose-dependency experiments revealed that 3.5 mJ/cm ² were still effective to achieve a > 6-log reduction in viral titres, whereas 1.75 mJ/cm ² lowered infectivity only by one order of magnitude. Conclusions: SARS-CoV-2 is rapidly inactivated by relatively low doses of UV-C irradiation and the relationship between UV-C dose and log-viral titre reduction of surface residing SARS-CoV-2 is nonlinear. Our findings emphasize that it is necessary to assure sufficient and complete exposure of all relevant areas by integrated UV-C doses of at least 3.5 mJ/cm ² at 254 nm. Altogether, UV-C treatment is an effective non-chemical option to decontaminate surfaces from high-titre infectious SARS-CoV-2.
Article
Pulsed UV (PUV) technology is accepted commercially for disinfection within the food packaging industry, but has yet to be deployed by the water/wastewater sector. This is partly due to a lack of robust, independently validated data for submerged or flow-through treatment applications. This study evaluated the efficacy of PUV for water disinfection under flow-through conditions. Bacterial pathogens of interest in the food and water/wastewater sector, namely Escherichia coli, Staphylococcus aureus and Listeria innocua (surrogate for L. monocytogenes) were used to investigate the potential for photoreactivation and/or dark repair post PUV flow-through disinfection. A continuous-flow low-pressure UV was also analysed under similar experimental conditions. Bacterial inactivation via flow-through PUV was dependant on energy output with E. coli exhibiting greatest sensitivity to PUV treatment (5.3 log 10 inactivation after treatment at 1539 mJ/cm ² - output in UV range < 300 nm); L. innocua exhibited the highest PUV resistance (3.0 log 10 inactivation after treatment at 1539 mJ/cm ² – output in UV range < 300 nm) under similar treatment conditions. Greater photoreactivation occurred at lower PUV outputs for both S. aureus and E. coli after flow-through PUV treatment. Thus exposure of treated bacteria to natural light, immediately post flow-through PUV treatment, should be avoided to minimise photoreactivation. The LPUV demonstrated inactivation of all bacteria below the limit of detection (1 CFU/mL) and inhibited the occurrence of photoreactivation. This study highlights the importance of considering bacterial repair potential and the need for further development of PUV technology for such applications.
Article
Full-text available
Ultraviolet (UV) Light Emitting Diodes (LEDs) emitting at 260 nm were evaluated to determine the inactivation kinetics of bacteria, viruses, and spores compared to low-pressure (LP) UV irradiation. Test microbes were E. coli B, a non-enveloped virus (MS-2), and a bacterial spore (Bacillus atrophaeus). For LP UV, 4-log10 reduction doses were: E. coli B, 6.5 mJ/cm(2); MS-2, 59.3 mJ/cm(2); and B. atrophaeus, 30.0 mJ/cm(2). For UV LEDs, the 4-log10 reduction doses were E. coli B, 6.2 mJ/cm(2); MS-2, 58 mJ/cm(2); and B. atrophaeus, 18.7 mJ/cm(2). Microbial inactivation kinetics of the two UV technologies were not significantly different for E. coli B and MS-2, but were different for B. atrophaeus spores. UV LEDs at 260 nm are at least as effective for inactivating microbes in water as conventional LP UV sources and should undergo further development in treatment systems to disinfect drinking water.
Article
Full-text available
Polychromatic ultraviolet (UV) irradiation is a common method of pathogen inactivation in the water treatment industry. To improve its disinfection efficacy, more information is necessary on the mechanisms of ultraviolet inactivation on microorganisms at wavelengths throughout the germicidal UV spectrum, particularly below 240 nm. This work examined UV inactivation of the 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 between 210 nm and 290 nm. To evaluate the mechanisms of UV inactivation throughout this wavelength range, RT-qPCR (Reverse Transcription quantitative Polymerase Chain Reaction) 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 germicidal UV spectrum. This demonstrates that genomic damage is the dominant cause of MS2 inactivation from exposure to germicidal UV irradiation. These findings contrast those of adenovirus, for which MS2 is used as a viral surrogate when validating polychromatic UV reactors.
Article
Full-text available
Aims: To investigate the medium-pressure (MP) and low-pressure (LP) Ultraviolet (UV) susceptibility and the repair potential of Enterococcus faecalis (DSM 20478) after UV treatment. Methods and results: A range of UV doses from 4 to 19 mJ cm(-2) was selected in this study. Photoreactivation and dark repair performance were investigated under fluorescent light or in the dark respectively. The inactivation and repair performance of UV disinfection under a range of salinities (0, 1%, 3%) and temperature (4 and 25 °C) were compared. Results indicated that MP UV exposure resulted in higher inactivation efficiency against E. faecalis than LP UV exposure. For repair potential, LP UV resulted in a greater level of light repair than MP UV. Effect of salinity on the inactivation and repair of E. faecalis was correlated with UV sources, whereas low temperature generally adversely affected the inactivation efficiency and final repair levels after both MP and LP UV exposure. Conclusions: Both salinity and temperature demonstrated to play an important role in the inactivation and repair capability when UV light was used to treat ballast water. Significance and impact of the study: Considering that UV-treated ballast water is exposed or discharged to marine water environment in many countries with various temperature and salinity conditions, results of this study provide significant implications for the management of public health associated with ballast water treatment and discharge. This article is protected by copyright. All rights reserved.
Article
Full-text available
Organic micro-pollutants in drinking water treatment, including soluble microbial products (SMP) can affect the disinfection process of pathogens. This work studied the effect of sodium alginate (SA), a natural polysaccharide and model SMP, on UV inactivation of coliphage MS2 as an entric virus surrogate. SA could enhance UV inactivation, and the effect might be related to reactive oxygen species (ROS) generated from the SA solution. Calculated by UV dose requirement for a 4 log MS2 inactivation, 50 mg L−1 SA increased the inactivation efficiency by approximately 50%. Scavengers of possible reactive species were applied, and t-BuOH and NaN3 reduced the enhancing effect, indicating the production and contribution of hydroxyl radical and singlet oxygen, respectively. The former was not produced in the absence of SA, while the latter was generated by both the test medium and SA. The overall mechanism of virus disinfection by UV in the presence of SA was proposed to include direct UV damage, singlet oxygen produced from the test medium and SA, and hydroxyl radical from SA.
Article
Full-text available
Practical difficulties of the traditional adenovirus infectivity assay such as intensive labor requirements and longer turnaround period limit the direct use of adenovirus as a testing microorganism for systematic, comprehensive disinfection studies. In this study, we attempted to validate the applicability of integrated cell culture quantitative PCR (ICC-qPCR) as an alternative to the traditional cell culture method with human adenovirus type 2 (HAdV2) in a low-pressure UV disinfection study and to further optimize the procedures of ICC-qPCR for 24-well plate format. The relatively high stability of the hexon gene of HAdV2 was observed after exposure to UV radiation, resulting in a maximum gene copy reduction of 0.5 log10 at 280 mJ cm(-2). Two-day post-inoculation incubation period and a maximum spiking level of 10(5) MPN mL(-1) were selected as optimum conditions of ICC-qPCR with the tested HAdV2. An approximate 1:1 correlation of virus quantities by the traditional and ICC-qPCR cell culture based methods suggested that ICC-qPCR is a satisfactory alternative for practical application in HAdV2 disinfection studies. ICC-qPCR results, coupled with a first-order kinetic model (i.e., the inactivation rate constant of 0.0232 cm(2) mJ(-1)), showed that an UV dose of 172 mJ cm(-2) achieved a 4-log inactivation credit for HAdV2. This estimate is comparable to other studies with HAdV2 and other adenovirus respiratory types. The newly optimized ICC-qPCR shows much promise for further study on its applicability of other slow replicating viruses in disinfection studies.
Article
Full-text available
Disinfection of microbes is of importance to prevent the spread of pathogens and non-indigenous species in the environment. Here we test the applicability of using flow cytometry (FCM) to evaluate inactivation of the phytoplankter Tetraselmis suecica after UV irradiation and labeling with the esterase substrate 5-carboxyfluorescein diacetate acetoxymethyl ester (CFDA-AM). Non-irradiated and UV irradiated samples were analyzed with the plate count technique and FCM for 24days. The numbers of colony forming units were used as a standard to develop a FCM protocol. Our protocol readily distinguishes live and dead cells, but challenges were encountered when determining whether UV damaged cells are dying or repairable. As damaged cells can represent a risk to aquatic organisms and/or humans, this was taken into account when developing the FCM protocol. In spite of the above mentioned challenges we argue that FCM represents an accurate and rapid method to analyze T. suecica samples. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
Article
Full-text available
Disinfection of bacterial viruses MS2, Q, and X174 in water was successfully carried out using deep ultraviolet light-emitting diodes (DUV-LEDs) operated at 280nm and 255nm. It was shown that the 280-nm DUV-LEDs are much more suitable than the 255-nm DUV-LEDs for the disinfection of water because, even though the disinfection efficiency of the former DUV-LEDs is only half that of the latter ones, the production of high-power 280-nm DUV-LEDs is much easier than that of the 255-nm ones because the external quantum efficiency of the 280-nm DUV-LEDs is more than ten times that of the 255-nm DUV-LEDs. We propose the use of vertical emitting DUV-LEDs for the design of an efficient DUV-LED disinfection chamber. This disinfection technique using DUV-LEDs will open new avenues for water purification.
Article
Full-text available
The use of Aspergillus niger (A. niger) fungal spores as challenge organism for UV reactor validation studies is attractive due to their high UV-resistance and non-pathogenic nature. However A. niger spores UV dose-response was dependent upon sporulation conditions and did not follow the Bunsen-Roscoe Principle of time-dose reciprocity. Exposure to 8 h of natural sunlight for 10 consecutive days increased UV resistance when compared to spores grown solely in dark conditions. Application of 250 mJ cm(-2) at high irradiance (0.11 mW cm(-2)) resulted in a 2-log inactivation; however, at low irradiance (0.022 mW cm(-2)) a 1-log inactivation was achieved. In addition, surface electron microscopy (SEM) images revealed morphological changes between the control and UV exposed spores in contrast to other well accepted UV calibrated test organisms, which show no morphological difference with UV exposure.
Article
Full-text available
Adenoviruses, the most UV resistant microorganism currently known, are posing concerns in UV treated drinking water. To reduce the risk from adenovirus infection, combination processes of UV and chlorination are attractive. Bacteriophage MS2 and adenovirus 5 (AdV5) were used in this study, and inactivated by low-pressure UV (LPUV) lamp, chlorination, sequential processes (UV-Cl 2 and Cl 2 -UV) and a simultaneous process (UV/Cl 2). MS2 was more resistant against chlorine than AdV5, and CT values for 2 log reduction of MS2 and AdV5 were 0.77 and 0.033 mg-min/L, respectively. However, AdV5 was more resistant to UV than MS2 and required a 101 mJ/cm 2 of fluence for 2 log reduction. Compared to the application of UV or chlorine separately, an increasing trend of MS2 inactivation rate was found in the sequential processes, which was statistically significant (p < 0.05, ANCOVA). The simultaneous process of UV/Cl 2 for MS2 provided about 2.3 times higher inactivation rate than a summation of inactivation rates by the separate application of either chlorine or UV, even at the same UV fluence rate and the same initial chlorine concentration. The combination processes of UV and chlorine, either sequential or simultaneous application, seemed to be more effective than a standalone process in viral inactivation.
Article
Full-text available
Disinfection by low-pressure monochromatic ultraviolet (UVC) radiation (253.7 nm) became an important technique to sanitize drinking water and also wastewater in tertiary treatments. In order to prevent the transmission of waterborne viral diseases, the analysis of the disinfection kinetics and the quantification of infectious viral pathogens and indicators are highly relevant and need to be addressed. The families Adenoviridae and Polyomaviridae comprise human and animal pathogenic viruses that have been also proposed as indicators of fecal contamination in water and as Microbial Source Tracking tools. While it has been previously suggested that dsDNA viruses may be highly resistant to UVC radiation compared to other viruses or bacteria, no information is available on the stability of polyomavirus toward UV irradiation. Here, the inactivation of dsDNA (HAdV2 and JCPyV) and ssRNA (MS2 bacteriophage) viruses was analyzed at increasing UVC fluences. A minor decay of 2-logs was achieved for both infectious JC polyomaviruses (JCPyV) and human adenoviruses 2 (HAdV2) exposed to a UVC fluence of 1,400 J/m2, while a decay of 4-log was observed for MS2 bacteriophages (ssRNA). The present study reveals the high UVC resistance of dsDNA viruses, and the UV fluences needed to efficiently inactivate JCPyV and HAdV2 are predicted. Furthermore, we show that in conjunction with appropriate mathematical models, qPCR data may be used to accurately estimate virus infectivity.
Article
Full-text available
We have used integrating-sphere UV spectroscopy to study scattering of radiation from an XeBr exciplex lamp (282 nm) by nanoparticles of a photocatalyst (TiO2) and Escherichia coli CN13 cells. We have demonstrated that we must take into account scattered radiation in calculating the UV doses for disinfection of water in the presence of suspended TiO2 particles. We have established that using the absorption intensities for the water to be disinfected in the dose calculation, obtained without taking into account the intensity of scattering of the radiation, leads to the actual dose exceeding the calculated dose by 5.2% to 69.4%. Total inactivation of the cells (from the absence of colony-forming units (CFU) after incubation of the irradiated aqueous suspension) was achieved at a UV radiation dose of 30 and 40 mJ/cm2 and TiO2 concentration of 0.25 and 0.10 g/L. The optimal concentration of TiO2 in water determined was 0.25 g/L, which corresponds to the maximum concentration of hydroxyl radicals and the rate of their formation.
Article
The microbicidal effect of UV light depends on the dose in both, disinfection processes and natural inactivation by the sunlight in surface water. Deviations of the time dose reciprocity are well known from chemical water disinfection whereas no data are available about this effect in UV inactivation in water. In a previous study we found that the UV inactivation behaviour of yeast strains does not follow the time dose reciprocity, insofar that longer exposure led to higher reduction of cultivable cells. In contrast, an earlier study about E coli B/r claimed a higher inactivation with single exposure compared with fractionated UV irradiation. To investigate this question we selected water-relevant microorganisms and studied their UV inactivation behaviour (253.7nm) by means of a specially designed UV irradiation apparatus (a) under standard irradiation conditions (2W/m2) and (b) with three levels of UV dose rate (2, 0.2 and 0.02W/m2). The test organisms were (i) three E coli strains (ATCC 25922, ATCC 11229 and an isolate from sewage) representing the routinely used faecal indicator, (ii) three bacterial viruses (MS2, ϕX174 and B40-8) proposed as indicators for viral contamination in water and (iii) spores of Bacillus subtilis because of their use as a biodosimeter in prototype testing of commercial UV plants for drinking water disinfection. We found, under standard inactivation conditions, that the E coli strains and phage ϕX174 are most UV susceptible, followed by B40-8 and finally MS2 and bacterial spores. The dose protraction experiments revealed for the E coli strains a higher inactivation with high dose rates compared to low dose rates at the same UV doses (difference of about 1 log10 at 80-100J/m2). The other test organisms did not deviate from the time dose reciprocity in the proven range of dose.
Article
Previous bench-scale results demonstrated that polychromatic medium-pressure (MP) ultraviolet (UV) disinfection could achieve 4-log adenovirus inactivation at equivalent UV doses well below those required under the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). These findings were confirmed and extended to a full-scale UV disinfection reactor using a live adenovirus challenge. The MP UV disinfection system was able to measure > 4-log adenovirus disinfection at an MS2 coliphage reduction equivalent dose (RED) of < 100 mJ/cm2. The highest observed adenovirus-based RED achieved, referenced to a low-pressure (LP) UV dose-response, was 233 mJ/cm2; the validated RED, including relevant validation factors, was equivalent to that required by the LT2ESWTR for 4-log virus inactivation credit. These results proved that required virus disinfection doses can be validated and that MP UV is capable of meeting the 4-log virus disinfection standard in the LT2ESWTR at a measurable and achievable UV dose substantially lower than that of LP UV technology.
Article
Previous evaluations of the effect of ultraviolet (UV) light on Cryptosporidium parvum oocysts have been limited to a single strain-the Iowa strain. This study investigated the response of five strains of C. parvum to UV. A collimated beam apparatus was used to apply controlled doses of monochromatic (254 nm) UV to oocysts of the Iowa, Moredun, Texas A&M, Maine, and Glasgow strains. Irradiation was measured using a calibrated radiometer and sensor. Inactivation was quantified through animal infectivity by inoculation of cohorts of CD-1 neonatal mice with UV-treated and untreated control oocysts of each strain followed by examination of intestinal sections for infection using hemotoxylin and eosin staining. A UV light dose of 10 mJ/cm(2) achieved at least 4-log(10) inactivation of all strains evaluated. All five strains of C. parvum were shown to be highly susceptible to low levels of UV light.
Article
Recent studies have shown that ultraviolet (UV) radiation reduces the infectivity of Cryptosporidium parvum oocysts and Giardia spp. Cysts. The objective of this work was to further parvum oocysts and G. muris cysts in the presence of suspended examine UV inactivation of C. particulate matter. Naturally occurring particulate matter consisting of a heterogeneous mixture of biological and non-biological particles, mainly in the 5-25 mu m size range, was concentrated from a lake. Different aliquots of this material were mixed with purified oocyst and cyst and the suspensions were exposed to UV fluences of reparations in aqueous suspensions, p 5 and 40 mJ/cm(2) from a medium-pressure mercury arc lamp using a collimated beam apparatus. Parasite inactivation was determined using mouse infectivity assays. Addition of particulate matter was correlated with statistically significant reductions in C. parvum and G. muris inactivation of 0.8 log(10) and 0.4 log(10), respectively, even after the fluence was adjusted for increased absorbance due to the presence of the particles. The corresponding increases in turbidity were 0.3-20 NTU for C. parvum and 7.5-20 NTU for G. muris. The magnitude of the effect was a function of the final suspension turbidity but was independent of fluence. in this the effect of particles on parasite inactivation at turbidity values of less than 10NTU was study, small and difficult to measure, and would likely be unimportant in practice. Although the mechanism for this reduction was not determined, the results suggest that the particulate matter present in natural surface waters may interact with oocysts and cysts and thereby result in a reduction in UV inactivation over and above that attributable to simple absorbance. The effect of turbidity on inactivation measured in this work may not necessarily apply generally since the characteristics of the particles that compose turbidity may differ considerably between water sources.
Biodosimetry, that is the application of microorganisms for the measurement of radiation, is already in wide use in the field of UV disinfection. The measurement of the mean fluence in flow-through systems with a biodosimeter (microorganisms with calibrated UV sensitivity) results in the Reduction Equivalent Fluence (REF). In the case of quasi monochromatic radiation (mercury low pressure lamp, 253.7 nm), the flow pattern of the water through the inhomogeneous radiation field, together with some other parameters, strongly influences the REF but the spectral sensitivity of the biodosimeter plays no role. If microorganisms with shouldered survival curves are used as biodosimeters two parameters (k and d) are necessary to describe their survival curves. In general, both parameters are wavelength dependent and the functions k(λ) and d(λ) must be known if medium pressure mercury lamps are used, which emit polychromatic UV radiation. The knowledge of k(λ) also is necessary for selecting an appropriate UV sensor which controls the function of the UV lamps during the operation of the disinfection plant. In literature many different spectral sensitivity curves were published but they all differ somehow. The functions k(λ) and d(λ) were measured for spores of Bacillus subtilis ATCC 6633 in using quasi-monochromatic UV radiation and the results were tested in using polychromatic UV radiation.
Article
Ultraviolet irradiation is gaining importance as a disinfection procedure for drinking water and in waste water treatment. Since water is one of the main transmission routes of hepatitis A virus the susceptibility of HAV to UV rays is of special interest. MS-2 coliphage resembles HAV in size and structure, is easy to handle, and might therefore serve as indicator organism for the assessment of water quality and for evaluating the quality of water treatment processes. Hepatitis A virus and MS-2 coliphage were suspended in 0.9% sodium chloride solution and were irradiated in a 20-ml quarz cuvette at 254 nm. For a reduction rate of four log units a three times higher UV dose was required with MS-2 than with HAV.
Article
Abstract: A ring-shaped disinfection apparatus has been developed containing twenty ultraviolet-light-emitting diodes (UV-LEDs) with emission at 285 nm. The apparatus was applied to Escherichia coli, Qβ, MS2, and adenovirus in water. The reduction-equivalent fluence in the apparatus was determined, based on a modification of the protocol for the bench-scale challenge test by low-pressure (LP) UV lamp systems (LPUV). All species demonstrated log-linear inactivation profiles versus the fluence, and the inactivation rate constants for E. coli, Qβ, MS2, and adenovirus were 0.157, 0.037, 0.029, and 0.023 cm2/mJ, respectively. The inactivation rate constant for adenovirus under the UV-LED exposure (k'UV-LED) was higher than that under a LPUV lamp (k'LPUV), and the ratio of k' UV-LED to k'LPUV, which is approximated as a germicidal factor at 285 nm, was 1.15 for adenovirus. To conclude, this study demonstrated a high potential of the 285 nm UV-LEDs to inactivate microorganisms in water. The germicidal factor found for adenovirus implies that the 285 nm UV-LED could be a good option to inactivate adenovirus in water. DOI: 10.1061/(ASCE)EE.1943-7870.0001061. © 2015 American Society of Civil Engineers.
Every year around 3.4 million people die from water-related diseases, mainly amoebiasis and diarrhoea caused by bacteria. The assessment of the efficiency of a UV light disinfection process in the inactivation of indicators, pathogen bacteria and amphizoic amoebae in a secondary treated effluent was carried out. Wastewater was irradiated with different doses of UV light using a collimated-beam reactor. Dose-response results showed that a UV dose of 15 mW·s/cm 2 was enough to inactivate FC to the limit established in Mexican legislation (<1,000 MPN/100 ml) for irrigation reuse, as well as reaching a 2 log inactivation for faecal streptococci. Also, the final concentration reached for Salmonella typhi was <10 3 MPN, which is the minimal concentration for a disease response in humans. The isolation from the secondary effluent and the pathogenicity determination of Acanthamoeba were carried out. Amoebae were concentrated to higher concentrations than those of the effluent for irradiation tests. Radiation tests showed that amoebae required higher doses than bacteria for their total inactivation (60 mW·s/cm 2 for a 2 log reduction). Results showed that UV light is an alternative to inactivate high contents of bacteria and amoebae trophozoites, although higher doses were needed for the high concentrations of amoebae used.
Article
After a critical review of the fundamental equations describing photobiological and photochemical processes occurring in a medium exposed to a quasi-collimated monochromatic UV light beam, the analysis in this review is extended to analogous processes driven by polychromatic UV light, such as that emitted by medium pressure mercury-vapor arc lamps. The analysis is based on the Second Law of Photochemistry, namely that all photochemical events must be independent, and the rate of such events must be proportional to the rate of photon absorption. A consistent application of the Second Law of Photochemistry leads to a concept change; hence it is proposed herein to use photon fluence and photon fluence rate, rather than fluence (UV dose) and fluence rate, respectively, in the analysis and interpretation of photobiological and photochemical processes. As a consequence, many equations that have been used in the past must be revised, and some experimental information (e.g., action spectra) needs to be re-analyzed. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
Article
Ultraviolet (UV) disinfection is being considered for inactivation of pathogens in filtered surface waters across North America. MS2 coliphage is the most commonly used test microbe for UV reactor validation in North America, and the development of UV dose-response data for MS2 at bench scale is an integral part of validation testing. This research evaluated the effect of water quality (e.g., turbidity, particle count, particle size, and absorbance) and sample depth on inactivation of MS2 coliphage in 17 filtered waters. In addition, the inactivation performance of low-pressure (LP) and medium-pressure (MP) lamp types was compared. Results indicated that turbidity, particle count, and absorbance, when factored into the bench-scale dose measurement, did not affect UV inactivation of MS2 coliphage in filtered waters meeting federal regulations. UV light from MP lamps appeared more effective than LP UV for inactivating MS2. These results suggest that water quality should not be considered a major factor in properly designed UV bench-scale tests or in reactor validation challenges that use inactivation kinetics of MS2 coliphage as a dose-measurement tool in filtered surface waters.
Article
Disinfection with UV radiation in the range of 240-290 nm is emerging as an alternative to conventional chemical disinfectants because byproduct formation is negligible with UV radiant exposure of 400 J/m2 (at 253.7 nm) required for a 4 log-reduction of germs and viruses. Prerequisites for disinfection are outlined, and both chemical and UV disinfection are compared. A 4 log-reduction requires a 99.99% homogeneous UV radiant exposure of ≤ 400 J/m2 to all water volume elements passing the UV system and depends on radiation field and flow pattern and cannot be calculated from technical data. Hydraulics may cause severe mismatch between calculation and reality. A performance of 400 J/m2 and a 4 log-reduction has to be verified by biodosimetric testing of prototypes using suspensions of germs with a known UV susceptibility. Safe UV disinfection is ascertained by flow control and monitoring of UV irradiance in W/m2 with standardised UV sensors at defined positions in the UV units. During operation UV irradiance must not fall below a system specific minimum value approved with the biodosimetric test.
Article
Ultraviolet (UV) disinfection is now an accepted technology for inactivation of a variety of waterborne pathogens in wastewater and drinking water. However, the techniques used in much of the previous research aimed at providing information on UV effectiveness have not yet been standardized. Thus in many peer reviewed published literature, it is not clear how the UV irradiations were carried out, nor how the average fluence (or UV dose) given to the microorganisms has been determined. A detailed protocol for the determination of the fluence (UV dose) in a bench scale UV apparatus containing UV lamps emitting either monochromatic or broadband UV light was developed. This protocol includes specifications for the construction of a bench scale UV testing apparatus, methods for determination of the average irradiance in the water, details on UV radiometry, and considerations for microbiological testing. Use of this protocol will aid in standardization of bench scale UV testing and provide increased confidence in data generated during such testing.