UV Inactivation of Viruses in Natural Waters PDF Download
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Author: Gregory A. Snicer
Publisher: American Water Works Association
ISBN: 1583210059
Category : Water
Languages : en
Pages : 132
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Book Description
Author: Gregory A. Snicer
Publisher: American Water Works Association
ISBN: 1583210059
Category : Water
Languages : en
Pages : 132
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Book Description
Author:
Publisher: American Water Works Association
ISBN: 9781583213414
Category : Medical
Languages : en
Pages : 112
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Book Description
This research studied low pressure(LP), low pressure-high-output (LPHO, medium pressure(MP) and pulsed (PUV) UV Systems and their effects on various pathogens. Among the findings were: bacteria is more susceptible to UV light than viruses; some strains of E.coli had different dose responses without explanation; adenovirus serotypes 40 and 41 are highly resistant to UV inactivation and a residual disinfection process is recommended to follow UV disinfection. All details of the study and models are discussed thoroughly.
Author: Stephanie Leah Molloy
Publisher:
ISBN:
Category : Enteroviruses
Languages : en
Pages : 150
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Book Description
Author: Shiao Huei Lo
Publisher:
ISBN:
Category : Silicate minerals
Languages : en
Pages : 102
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Book Description
Author: Stephen De Mora
Publisher: Cambridge University Press
ISBN: 1139429515
Category : Science
Languages : en
Pages : 338
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Book Description
This book, first published in 2000, provides a comprehensive, multidisciplinary review of UV radiation effects in the marine environment. It is aimed at researchers and graduate students in photobiology, photochemistry and environmental science. It will also be useful as a supplementary text for courses in oceanography, climatology and ecology.
Author: Andrea Idette Silverman
Publisher:
ISBN:
Category :
Languages : en
Pages : 111
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Book Description
Sunlight inactivation of microorganisms is a natural process that can occur in any sunlit water and has implications for microbial ecology, the fate of microbial contaminants in the environment, and natural wastewater treatment systems. This work focuses on sunlight inactivation of waterborne viruses, which present a special challenge in health-related water microbiology given that waterborne human viruses are important etiologies of disease, and are difficult to remove and inactivate in water. The research presented in this dissertation builds upon previous research by determining the mechanisms and rates of sunlight inactivation of human viruses in natural waters; these data were used to build predictive inactivation rate models that account for virus type, sunlight irradiance and water quality. Additionally, two applications of sunlight inactivation - the differential stability of indicator organisms and human viruses in the environment, and disinfection of irrigation water in wastewater-irrigated agriculture - were investigated. There are three proposed sunlight inactivation mechanisms for viruses: the direct- and indirect-endogenous mechanisms, which require absorption of photons by virus components, and the exogenous mechanism, which involves reaction between the virus and exogenously produced reactive intermediates formed by photochemical reactions. All three mechanisms are affected by water quality. Natural organic matter, for example, is found in most aquatic environments and is capable of both attenuating sunlight - which would decrease sunlight exposure and therefore inactivation rates - and photosensitizing production of reactive intermediates - which could increase inactivation rates of viruses susceptible to the exogenous mechanism. The first goal of this dissertation was to better understand the mechanisms of sunlight inactivation of select bacteriophage and human viruses in surface waters containing natural organic matter. Given the two main modes by which damage is delivered to viruses in sunlit surface waters - through direct absorption of photons (the direct- and indirect-endogenous mechanisms) and contact with reactive molecules formed by sensitizers in the water column (the exogenous mechanism) - a better understanding of sunlight inactivation mechanisms can help us predict how environmental conditions (e.g., sunlight irradiance, light attenuation, water quality, depth, mixing) can affect observed inactivation rates. Through laboratory experiments using simulated sunlight and natural organic matter-containing waters collected from the environment, we determined that the sunlight inactivation rates of human poliovirus type 3 and bacteriophage PRD1 mainly involved endogenous inactivation mechanisms, while MS2 and human adenovirus type 2 were also affected by the exogenous mechanism. Different virus types were found to have different rates of inactivation, and inactivation rates differed among water types depending on light attenuation and natural organic matter in the water source; this finding made it clear that water quality conditions and virus type must be taken into account when predicting inactivation rates. Additionally, MS2 was inactivated at the slowest rate in all waters, and PV3 the fastest, at the water depth that was studied (i.e., 5 cm). The data obtained in the initial virus inactivation study, along with findings from other researchers, were used to develop and test models that predict the sunlight inactivation rates of viruses in surface waters containing light-attenuating photosensitizers. Models were developed for poliovirus type 3 and MS2. Inactivation rates were modeled and measured in reactors containing different, well-mixed depths of water collected from an open-water wastewater treatment system; the models performed well in predicting inactivation rates in laboratory experiments. Given the tradeoff between decreased endogenous inactivation due to light attenuation and increased exogenous inactivation due to the presence of photosensitizers in natural organic matter-containing water, we compared the measured and modeled inactivation rates of poliovirus type 3 (which is reliant on endogenous mechanisms) and MS2 (which is susceptible to the exogenous mechanism) at different well-mixed depths. The inactivation rate of poliovirus type 3 was found to be lower than that of MS2 at deeper well-mixed depths, indicating that MS2 cannot be considered a conservative indicator of poliovirus sunlight inactivation under all conditions. Some research gaps - including the development of models that take into account the solar zenith angle, annual and diurnal variation in irradiance, and water body hydraulics - must be filled to successfully translate the models to environmental waters and natural sunlight. Many viruses are not culturable, making them difficult to study in general, let alone their inactivation rates. To better understand factors that dictate differences in sunlight inactivation rates between viruses, which could help in predicting inactivation rates of non-culturable viruses, we investigated whether sunlight inactivation of poliovirus type 3 is caused by damage to the protein capsid of the virus. More specifically, this research focused on the inhibition of viral `life' processes that depend on an intact capsid. Comparing data from assays that quantify host cell attachment and infectivity, we found that although sunlight exposure leads to an inhibition of poliovirus type 3 attachment to host cells (which is the first step in the infection process), this damage mechanism plays a minor role in total inactivation. The second part of this dissertation focuses on a case study of wastewater irrigation practiced in Accra, Ghana, with goals to better understand the health risks associated with wastewater irrigation in Accra, and to determine whether small, farmer-dug ponds can contribute to disinfection of irrigation water. To provide data that can be used to refine quantitative microbial risk assessment models of wastewater-fed agriculture in Accra, irrigation water samples were analyzed for concentrations of fecal indicator microorganisms (human-specific Bacteroidales, E. coli, enterococci, thermotolerant coliform, and F+ and somatic coliphages) and two human viruses (adenovirus and norovirus genogroup II). E. coli concentrations in all samples exceeded recommended limits set by the World Health Organization, human viruses were detected in 75% of samples analyzed, and virus concentrations were quantified in 60% of samples. Indicator organism and virus concentrations were compared as part of an analysis of differential stability of fecal indicator organisms and pathogens in the environment, and the appropriateness of assumptions used in quantitative microbial risk assessment to relate indicator organism concentrations to those of pathogens. After determining indicator organism and pathogen concentrations in Accra irrigation water, we investigated the ability of a farmer-developed intervention (small, on-farm ponds) to disinfect wastewater before use in vegetable irrigation. Results indicated that sunlight inactivation dominated the removal of two bacteria (E. coli and enterococci) and two bacteriophages (F+ and somatic coliphages) in these ponds, and that the ponds can contribute to the multi-barrier approach to reducing health risks related to wastewater irrigation. On-farm pond design and management recommendations, as well as challenges, are also discussed.
Author: Majid Nikougoftar Zarif
Publisher:
ISBN:
Category : Oxidation
Languages : en
Pages : 87
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Book Description
Adenoviruses cause gastrointestinal illnesses and have been listed on the U.S. EPA's Contaminant Candidate Lists (CCL). They are highly resistant to ultraviolet (UV) inactivation. Advanced oxidation processes (AOPs) are known to improve inactivation of microorganisms and simultaneously oxidize organics. The bacteriophage P22 was selected as a surrogate for adenoviruses due to their physical and genetic similarities. The main objective of this study was to compare the synergic disinfection potential of titanium dioxide (TiO2) or peracetic acid (PAA) with UV for viruses and bacteria in water. Both bench-scale and pilot-scale evaluation was done. A bench-scale collimated beam was included to evaluate the inactivation of P22 and E. coli by UV with and without TiO2 or PAA. A Purifics Photo-Cat system which is an integrated UV/ceramic membrane reactor was used for the pilot-scale TiO2-UV AOP experiments. For pilot-scale PAA-UV AOP experiments, an in-line D222 UV reactor unit provided by NeoTech Aqua Solutions, Inc. was used. TiO2 doses of 1, 10, and 40 mg/L were applied in the collimated beam and the Photo-Cat system. Higher TiO2 doses resulted in a higher inactivation in the Photo-Cat and lower inactivation in the collimated beam apparatus. Adding 40 mg/L of TiO2 in the photo-Cat system improved P22 inactivation by 25% while it slightly decreased P22 inactivation in collimated beam apparatus. PAA doses of 0.25 or 0.5 ppm were continuously injected upstream of the UV light and a 53% or 90% increase in inactivation was observed for E. coli, respectively, as compared to UV alone. However, P22 required higher dose with PAA-UV AOP and PAA concentrations of 1 or 10 ppm resulted in an 18% and 70% increase in the inactivation respectively, as compared to UV alone. Interestingly, when the same condition was applied to water with more organics (UVT 79%), E. coli exhibited the same level of susceptibility to PAA-UV AOP while P22 inactivation decreased. The results provide new insight on the effectiveness and applicability of adding AOP to UV for microbial inactivation in water. PAA-UV AOP can potentially enhance existing UV disinfection systems with minimal chemical addition, and a simple retrofit to existing UV units.
Author: Michael Richard Templeton
Publisher:
ISBN: 9780494157572
Category :
Languages : en
Pages : 482
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Book Description
Viruses are frequently attached onto or enmeshed within a variety of particles in natural waters and wastewaters, however relatively little is known about the impact of this viral particle-association on water treatment processes. This thesis focuses on the impact of particle-associated viruses on ultraviolet (UV) disinfection, a disinfectant currently gaining widespread popularity in the drinking water industry in North America. Particles smaller than 2 microns (mum) in diameter were shown to be large enough to enmesh and protect bacteriophages MS2 and T4 (model viruses) from UV light. This is smaller than the minimum particle size of 7-10 mum for the shielding of coliform bacteria from the UV disinfection of wastewater reported by earlier studies. In addition, particulate chemical composition, specifically UV-absorbing content such as organic or iron compounds, was a critical factor in the survival of particle-associated bacteriophage exposed to UV light. Particles such as humic acid floc, activated sludge floc, and iron precipitate particles were observed to protect attached phage from UV light. Dual-media filtration, which often precedes UV disinfection in surface water treatment, was shown to be an effective means of reducing the number of particle-associated phage. The breakthrough of particle-associated phage through an anthracite-sand filter was highest during periods of increased particle breakthrough (i.e. filter effluent turbidity> 0.3 NTU), especially at the end of the filter cycle. UV disinfection of phage in the filter effluent was negatively impacted during the end of filter cycle breakthrough conditions in some cases. In addition, it was observed that un-filterable humic acid particles smaller than 0.45 mum and/or humic acid coating of bacteriophage surfaces may have UV-protective effects. The research findings also re-emphasize that viral disinfection studies should account for particle-associated viruses using techniques such as the physico-chemical blending method that was used in this research, since failure to do so can result in significant underestimation of the true virus concentrations. Further, multiple viral surrogates should be used in experimental studies whenever possible, since viruses vary significantly in their sizes, shapes, and surface charges, all of which can influence the adsorption of viruses to particles.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Shamim I. Ahmad
Publisher: Springer
ISBN: 3319560174
Category : Medical
Languages : en
Pages : 367
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Book Description
This book is about the roles and importance of Ultraviolet (UV) light from sun and from man-made UV lamps in our daily life, on health and diseases, also its application in sterilization and treatment. The key words are: reactive oxygen species, DNA damage, UV mutagenicity, skin cancers, polymorphous light eruption, Xeroderma pigmentosum, vitiligo, psoriasis, rheumatoid arthritis, diabetes mellitus, metabolic syndromes, cardiovascular diseases, dermatology, photobiology, photodermatosis, vitamin D synthesis, vitamin D efficiency, water sterilization, blood sterilization, phototherapies, skin tanning and UV dosimeter. The book starts with introduction to UV light and the history of development of UV lamps and its applications. It then moves to describing the interaction of this light with biological components and the production of reactive oxygen species, their roles in cell signaling, cellular defense from foreign invaders, in mutagenesis leading to skin diseases including vitiligo, polymorphous light eruption and various forms of skin cancer. Then it presents the synthesis and importance of UV light and diseases, induced due to the deficiency of vitamin D. Roles of UV light in sterilization, disinfection, phototherapies are depicted in the next part and finally use and abuse of UV light in tanning salon and the availability and importance of use of UV dosimeter are highlighted. The three main focuses of this book are: - Damage to biological systems by UV light leading to certain skin diseases; most importantly skin cancers. - Importance of UV light in the in vivo synthesis of vitamin D when human bodies are exposed to it. - Diseases caused due to the deficiency of vitamin D and the use of UV lamps in phototherapy and sterilization processes. The editor has considerable experience in publishing medical books and has used it critically selecting the matters which will attract the readers from many areas of medical and non-medical fields. It is hoped that the materials presented in this book will give great benefit and will stimulate both novice and expert researchers in the field. The book gives excellent overviews of the current status of research and pointers to the future research achievements. Clinicians, medical general practitioners, technicians and staff working in UV related industries and especially those working in tanning salon should benefit from the information presented in safe handling of this light.
