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Bieker, Jill M. "Chemical inactivation of viruses." Diss., Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/226.
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Velez, Rivera Edwin. "A review of chemical disinfection methods for minimally processed leafy vegetables." Thesis, Manhattan, Kan. : Kansas State University, 2005. http://hdl.handle.net/2097/103.
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Emanuele, Sozzi. "Low-cost physico-chemical disinfection of human excreta in emergency settings." Thesis, University of Brighton, 2016. https://research.brighton.ac.uk/en/studentTheses/1d15b231-f0bc-4251-bf5c-7d7912073d84.
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The operation of a health-care facility, such as a cholera or Ebola treatment centre in an emergency setting, results in the production of pathogen-laden wastewaters that may potentially lead to onward transmission of the disease. The research presented here outlines the results of field and laboratory studies devised to inform the design and operation of a novel full-scale treatment protocol to disinfect pathogen-laden hospital wastewaters in situ, thereby eliminating the need for potentially hazardous road haulage and disposal of human excreta or wastewater to poorly-managed waste facilities. The approach investigated has the potential to provide an effective barrier to disease transmission by means of a novel but simple sanitary intervention. During Phase I of this research, a fieldwork study in Haiti focused on the design and operation, at short notice and within a disaster setting, of a new treatment technology that aimed to obviate the transport of untreated human excreta from emergency cholera treatment centres (CTC) to poorly-managed waste facilities. The results of this fieldwork period were validated and further optimised during Phase II: a detailed laboratory-based study in the UK that assessed the performance of the novel treatment technology in order to improve its efficacy. The performance of two physico-chemical protocols was monitored, first in the field (Port-au-Prince, Haiti), by means of both bench-scale and full-scale batch treatment of real highly-contaminated faecal waste from a cholera treatment centre (Phase I), and subsequently during more detailed laboratory studies (Phase II) using a ‘faecal-waste matrix’ that was created by mixing various municipal wastewaters and sludges in a proportion that aimed to mimic the composition of wastewaters produced at health-care facilities in emergency settings. The two investigated protocols achieved coagulation/flocculation and disinfection by exposure to high– or low–pH environments, using thermotolerant coliforms, intestinal enterococci, and somatic coliphages as indices of disinfection efficacy, and several physico-chemical parameters as indicators of treatment performance. In the high–pH treatment protocol, the addition of hydrated lime resulted in wastewater disinfection and coagulation/flocculation of suspended solids. In the low-pH treatment, disinfection (and partial colloidal destabilization followed by sedimentation) was achieved by the addition of hydrochloric acid, followed by pH neutralisation. A potential further step in this 4 second protocol was the coagulation/flocculation of suspended solids using aluminium sulphate. During Phase II, removal rates achieved for the high pH treatment protocol, in terms of physico-chemical parameters, were: COD > 80%; suspended solids > 85%; turbidity > 85%. Removal rates in terms of microbiological parameters were: thermotolerant coliforms > 5 Log10, intestinal enterococci >2 Log10 and somatic coliphage > 2 Log10. Removal rates achieved for the low-pH treatment protocol in terms of physico-chemical and microbiological parameters were: COD > 80%; thermotolerant coliforms between 0.2 and 1.2 Log10, with a mean removal of 0.75 Log10 and > 3 Log10 removal for intestinal enterococci. The removal of somatic coliphage was in excess of 4 Log10. The quantity and density of the sedimented sludge and several other physicochemical parameters (such as total nitrogen, total phosphorous, ammonia and ammonium, etc.) for the analysis of the supernatant were also monitored. This study represented the first known successful attempt to disinfect wastewater in a disease outbreak setting without resorting to the alternative, untested, approach of ‘super-chlorination’ which, it has been suggested, may not consistently achieve adequate disinfection. In addition, a basic costs analysis demonstrated significant savings in the use of reagent compared with super-chlorination. The approach to sanitation for cholera treatment centres and other disease outbreak settings presented here offers a timely response to a UN call for in situ disinfection of wastewaters generated in such emergencies. Further applications of the method to other emergency settings have been actively explored in discussion with the World Health Organization (WHO) in response to the ongoing Ebola outbreak in West Africa, and with the UK-based non-governmental organization (NGO) Oxfam.
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Fuerst, Georgia Brook. "INVESTIGATING PERACETIC ACID AS AN ALTERNATIVE TO SODIUM HYPOCHLORITE DISINFECTION." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1470144930.
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Mirlohi, Susan. "Chemical Identification and Flavor Profile Analysis of Iodinated Phenols Produced From Disinfection of Spacecraft Drinking Water." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/30997.
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The National Aeronautics and Space Administration (NASA) is considering the use of iodine for disinfection of recycled wastewater and potable water in the International Space Station (ISS). Like Chlorine and other halogen compounds, iodine can form disinfection by-products (DBPs) in the presence of organic compounds. Recycled wastewater sources proposed for reuse in the space station include laundry, urine, and humidity condensate. These contain large concentrations of iodine-demanding compounds, including phenol (Barkely et al., 1992). Therefore, the potential for the formation of iodine disinfection by-products (IDBPs) is of concern.
Based on the characteristics of the ISS recycled wastewater sources and potable water treatment system, a series of experiments was designed to evaluate the formation of IDBPs under different experimental conditions. Studies were conducted by reacting various concentrations of iodine with phenol at pH 5.5 and 8.0.Iodine concentrations of 10 and 50 mg/L and phenol concentrations of 5 and 50 mg/L were used. Reactions were monitored for up to 32 days for the formation of IDBPs. All reactions were maintained at 20 C in dark. High Performance Liquid Chromatography (HPLC) and Gas Chromatography/Mass Spectrometry (GC/MS) were used for identification and quantitative analysis of phenolic compounds. Spectrophotometry was used to monitor the iodine concentrations. Falvor Profile analysis (FPA) method was used to evaluate the odor characteristics of the phenolic compounds.
Reactions of iodine with phenol resulted in the formation of the following by-products: 2-iodophenol, 4-iodophenol, diiodophenols, and 2,4,6-triiodophenol. Most reaction conditions studied resulted in the formation of all or some of the specified iodophenols. The initial mass ratio of iodine to phenol was the major determining factor in the concentrations and types of by-products formed. The IDBPs were formed within one hour after initiation of the reactions. Extended reaction times did not lead to significant increases in the concentration of IDBPs. Under most reaction conditions, mono-subsituted phenols were detected at significantly higher concentrations than di-substituted phenolic compounds; triiodophenol was the major by-product when iodine:phenol mass ratio was 10:1. The greatest number of IDBPs were formed when reaction solutions consisted of 1:1 mass ratio of iodine to phenol. FPA panel indicated the odor threshold concentrations for phenol, 2-iodophenol, and 4-iodophenol were 5 mg/L, less than 1 ug/L, and 1 mg/L respectively. The most common odor descriptions for all these compounds were "chemical", "phenolic", and "medicinal".Master of Science
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Rød, Kaia Kjølbo. "Sori disinfection in cultivation of Saccharina latissima : Evaluation of chemical treatments against diatom contamination." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18724.
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Diatom contamination is a problem in the early cultivation stages of Saccharina latissima. Macro- and microalgae compete for the same abiotic resources, and diatoms may overgrow and eliminate seedlings of S. latissima if introduced to the macroalgae cultivation system. Germanium dioxide (GeO2), which blocks the cell division in diatoms, has been used as a diatom controller in the growth medium in cultivation of macroalgae. However, the chemical is very expensive and it has been suggested that the chemical inhibit growth of S. latissima seedlings. In the present study, it was desirable to establish a sori disinfection method for large-scale cultivation systems that eliminate diatoms prior to S. latissima spore release. It that was called for a purely chemical disinfection method as mechanical removal of contamination is labour-intensive and costly. Five chemicals, including 130 different trials, were tested on diatoms in free suspension. Acetic acid, sodium hypochlorite and ethanol eliminated diatom growth independent of concentration, exposure time and exposure temperature. Formaldehyde and Lugol’s solution revealed surviving diatoms in the weaker treatments. GeO2 eliminated growth of Chaetoceros muelleri and Skeletonema costatum, but monocultures of Phaeodactylum tricornutum were found at both concentrations (0.1mL L-1 and 0.5mL L-1) eleven days after inoculation. Acetic acid, Lugol’s solution and sodium hypochlorite were tested as sori disinfectants, and GeO2 was used as a negative control for diatom growth. Acetic acid treatments were lethal to both diatoms and S. latissima spores, and GeO2 treatments appeared to have negative influence on fertility and growth of young seedlings of S. latissima. Disinfection with 600ppm sodium hypochlorite or 2% Lugol’s solution, with an exposure time of 2 minutes and exposure temperature of 10°C, followed by two rinsing baths of sterile seawater, gave total elimination of diatoms. No notable effects on spore release, sporophyte growth or early development of young seedling were seen. This implies that disinfection of sori can be done safely by use of these treatments, without concern about reduced quality or quantity of cultivated seaweeds. Sori disinfection was done on disks cut from ripe sori in a disinfecting bath, and no mechanical removal of sori contamination was performed. Sodium hypochlorite was suggested as a new sori disinfectant based on an apparently good safety margin between lethal doses to diatoms and a harmful dose for S. latissima. The chemical also appears to be a widespread disinfectant in aquaculture systems, and can easily be neutralized with thiosulphate.
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LLoyd-Evans, Nellie. "Studies on the survival and chemical disinfection of human rotavirus (Wa) on inanimate surfaces." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4711.
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Horne, William Jeffrey. "Evaluation and Optimization of Control Strategies for Management of Disinfection Byproduct Precursors Within the Northeast Mississippi Water District." MSSTATE, 2005. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04282005-155220/.
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As a result of the EPA?s Disinfection Byproduct Rule, the Northeast Mississippi Regional Water Supply District requested that the Environmental Technology and Applications Laboratory at Mississippi State University conduct a study to develop techniques to comply with new TOC regulations. This study involved the use of jar testing and Enhanced Coagulation in a laboratory setting over a period of twelve months to optimize the various coagulants evaluated in this study. Iron (III) sulfate, aluminum sulfate, aluminum chloride, aluminum chlorohydrate, and a number of polyaluminum chlorides were evaluated in this study. Coagulants were evaluated on both a treatment effectiveness and economical basis. It was determined that an acidified alum solution performed best at meeting EPA standards for total organic carbon reduction, as well as being economically feasible.
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Walczak, Katarzyna, Jessica Thiele, Daniel Geisler, Klaus Boening, and Mieszko Wieckiewicz. "Effect of Chemical Disinfection on Chitosan Coated PMMA and PETG Surfaces—An In Vitro Study." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-236913.
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In oral sciences, chitosan application is of interest due to its antimicrobial and hemostatic activity. Chitosan coating of dentures and other intraoral devices could be beneficial for treatment of denture stomatitis or in the management of postoperative bleeding. Disinfection of dentures and prosthodontic materials is crucial before their use in patients. This study investigated the influence of chemical disinfectants on chitosan-coated surfaces. A total of 100 specimens were made: 50 of PMMA (polymethyl methacrylate), and 50 of PETG (polyethylene terephthalate glycol-modified) material and coated with 2% chitosan acetate solution. In each material, 5 groups (10 specimens each) were established and disinfected with Printosept-ID (L1), MD 520 (L2), Silosept (L3), or Dentavon (L4), or stored in distilled water (L0, control group). After disinfection, all specimens underwent abrasion tests (30,000 cycles in a tooth-brushing simulator). Areas without chitosan coating were measured by digital planimetry both before and after the disinfection/abrasion procedure and a damage-score was calculated. Regarding chitosan coating, the statistical analysis showed a significant influence of the disinfectants tested and significant differences between disinfectants (p < 0.05). Chitosan coating was most stable on PMMA and PETG after disinfection with MD 520 (L2). Otherwise, active oxygen containing disinfectants (L3, L4) led to the greatest alterations in the chitosan coating.
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Dodd, Jennifer Peters. "Chemical Identification and Organoleptic Evaluation of Iodine and Iodinated Disinfection By-Products Associated with Treated Spacecraft Drinking Water." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36642.
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Aboard the International Space Station, potable water will likely be produced from recycled wastewater. The National Aeronautic and Space Administration (NASA) plans to use iodine as a disinfectant, and, consequently, the formation of iodinated disinfection by-products (IDBPs) requires investigation. Objectives of this research were to determine possible precursors of IDBPs, identify IDBPs formed, and apply flavor profile analysis (FPA) as a tool to evaluate water qaulity. Experiments were performed by separately reacting iodine with each of the following organic compounds: methanol, ethanol, 1-propanol, 2-propanol, 1-methoxy-2-propanol, acetone, and formaldehyde. NASA previously identified all of these compounds in wastewater sources under consideration for recycling into potable water. Experiments were performed at pH 5.5 and 8, iodine concentrations of 10 and 50 mg/L, and organic concentrations of 5 and 50 mg/L. Gas chromatography/mass spectrometry was used to identify and monitor the concentrations of organic species. Spectrophotometry was used to monitor the iodine concentration. Acetone was the only compound identified as an IDBP precursor and it reacted to produce iodoacetone and iodoform. Concentrations of iodoform from 0.34 mg/L to 8.637 mg/L were produced at conditions that included each pH level, iodine concentration, and acetone concentration. The greatest iodoform concentration was produced at pH 8 from 50 mg/L of iodine and acetone. FPA indicated that the odor threshold concentration (OTC) of iodoform was 1.5 ug/L, and the OTC of iodine was 500 ug/L. Both iodine and iodoform have medicinal odors, making it difficult to distinguish each compound when present in a mixture.Master of Science
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Khan, Mohd Yahya. "Identification and Correlation of Disinfection Byproducts and Total Organic Halogen Precursors in a Biofilm Matrix." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1404662994.
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Wang, Fang. "Chlorine Contribution to Quantitative Structure and Activity Relationship Models of Disinfection By-Products' Quantum Chemical Descriptors and Toxicities." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/174.
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Quantitative Structure-Activity Relationship (QSAR) has been applied extensively in predicting toxicity of Disinfection By-Products (DBPs) in drinking water. Among many toxicological properties, acute and chronic toxicities of DBPs have been widely used in health risk assessment of DBPs. These toxicities are correlated with molecular properties, which are usually correlated with molecular descriptors. The primary goals of this thesis are: 1) to investigate the effects of molecular descriptors (e.g., chlorine number) on molecular properties such as energy of the lowest unoccupied molecular orbital (ELUMO) via QSAR modelling and analysis; 2) to validate the models by using internal and external cross-validation techniques; 3) to quantify the model uncertainties through Taylor and Monte Carlo Simulation. One of the very important ways to predict molecular properties such as ELUMO is using QSAR analysis. In this study, number of chlorine (NCl) and number of carbon (NC) as well as energy of the highest occupied molecular orbital (EHOMO) are used as molecular descriptors. There are typically three approaches used in QSAR model development: 1) Linear or Multi-linear Regression (MLR); 2) Partial Least Squares (PLS); and 3) Principle Component Regression (PCR). In QSAR analysis, a very critical step is model validation after QSAR models are established and before applying them to toxicity prediction. The DBPs to be studied include five chemical classes: chlorinated alkanes, alkenes, and aromatics. In addition, validated QSARs are developed to describe the toxicity of selected groups (i.e., chloro-alkane and aromatic compounds with a nitro- or cyano group) of DBP chemicals to three types of organisms (e.g., Fish, T. pyriformis, and P.pyosphoreum) based on experimental toxicity data from the literature. The results show that: 1) QSAR models to predict molecular property built by MLR, PLS or PCR can be used either to select valid data points or to eliminate outliers; 2) The Leave-One-Out Cross-Validation procedure by itself is not enough to give a reliable representation of the predictive ability of the QSAR models, however, Leave-Many-Out/K-fold cross-validation and external validation can be applied together to achieve more reliable results; 3) ELUMO are shown to correlate highly with the NCl for several classes of DBPs; and 4) According to uncertainty analysis using Taylor method, the uncertainty of QSAR models is contributed mostly from NCl for all DBP classes.
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Mbithi, John J. Nzyoka. "Studies on the role of inanimate surfaces and hands in the spread of hepatitis A virus and their chemical disinfection." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6618.
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Hepatitis A (HAV) continues to be a serious problem for human health. The present study was designed to (a) assess the vehicular role of human hands and environmental surfaces in the spread of HAV; (b) evaluate the efficacy of chemical disinfectants and handwashing agents to eliminate HAV from inanimate and animate surfaces; and (c) determine the efficacy of alkaline glutaraldehyde reuse against HAV and other microorganisms. Pressure and friction were found to significantly affect HAV transfer between hands and inanimate surfaces (F = 33.98; p 0.05) irrespective of the mode of transfer used. No statistically significant interaction was observed between mode of transfer and pressure or friction. The findings of this phase of the study suggest that human hands and inanimate surfaces may play an important role in the direct as well as indirect spread of HAV. HAV disinfection was assessed on experimentally-contaminated metal disks. No virus was transferred from disks treated with a 3% solution of Virkon. None of the eleven handwashing agents examined, however, was able to reduce the infectivity titer of HAV and PV to an undetectable level. The least reduction in HAV titer was shown by an unmedicated soap (77.96 $\pm$ 7.17%), while the highest level of reduction was given by Bacti-Stat Medicated Soap (92.04 $\pm$ 4.02%). Samples of 2% alkaline glutaraldehyde were collected over the 14-day reuse period from two manual and one automatic bath used for the disinfection of flexible bronchoscopes and gastrointestinal endoscopes at a neighboring hospital. The number of instruments put through each bath during the 14-day cycle was recorded. The broad-spectrum germicidal activity of the disinfectant lasted only up to six days. This suggests a review of alkaline glutaraldehyde reuse in the disinfection of semi-critical instruments such as flexible fiberoptic endoscopes. These findings should help in understanding the genesis of HAV outbreaks more clearly and in designing better measures for their prevention and control. (Abstract shortened by UMI.)
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Matias, Fernando M. G. "Studies on the influence of chemical disinfection, ultraviolet irradiation and pipe matrix on biofilm composition in drinking water distribution systems." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27887.
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There has recently been a shift in water treatment practices in Canada to a source-to-tap approach on water quality. With this approach comes the understanding that our water distribution systems are covered in biofilms which could contain potentially hazardous opportunistic pathogens. Meanwhile, regulations on control of disinfection byproducts in drinking water have also induced the phase-out of chlorine and its replacement with either chlorine dioxide or monochloramine in conjunction with UV treatment. These changes are based solely on the reduction of known disinfection byproducts and have not considered the impact of changing the disinfection regime on the ecology of biofilms within the distribution system. The objective of this study was to determine what, if any, influence changes in water disinfection would have on the mix of bacterial species in the distribution system biofilms with particular reference to cast iron and polycarbonate as pipe substrata.
Classical culture-based methods can reveal only a fraction of the bacterial content of biofilms because of our rudimentary understanding of the nutritional requirements of the organisms present and their inter-dependency. In contrast, newer techniques in molecular biology have become the norm for studying microbial ecology as they are not subject to the limitations of the culture methods, and thus can provide a much better profile of bacterial populations in biofilms. Although these methods have their own biases, PCR-DGGE was selected to monitor any changes in the profiles of the biofilms obtained under different disinfectant regimes and identify similarities and differences. Identification of the bacterial species would then be obtained by the sequencing of cloned bands, and matching them to the online databases, BLAST and RDP II.
Clear differences were observed in the biofilms from the two pipe materials tested. Aquabacterium parvum, Escherichia coli, Dechloromonas sp., Methylobacillus flagellatus, Phyllobacterium sp., Rhodocyclus sp., and Sphingomonas sp., were only identified in biofilms from cast iron coupons, while Chitinophaga sp., was found in biofilms from only polycarbonate coupons. This confirms that the pipe material can influence the types of organisms growing on its surface.
In general, the bacterial profiles were similar in the presence or absence of upstream UV treatment, except for the uncultivable Flavobacterium spp., which was detected only in the absence of UV treatment. This indicated that UV treatment has a relatively minor impact on altering the biofilm composition.
While a direct comparison between the impacts of the chemical disinfectants was not possible due to the design of the experimental set-up, the data obtained showed that several aspects of the bacterial profiles remained similar irrespective of the dosage levels of chlorine, chlorine dioxide, and monochloramine used.
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Verdugo, Edgard Manuel. "Reaction of carbon nanotubes with chemical disinfectants: Byproduct formation and implications for nanotube environmental fate and transport." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1922.
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Nanomaterials (materials which have at least one dimensional feature with length less than 100 nanometers), and carbon nanotubes (CNTs) specifically, have exhibited great potential in water treatment. CNTs are cylindrical structures comprising single or multiple concentric graphene sheets and have diameters from less than 1 nanometer (nm) up to 50 nm (one nm is one millionth of a millimeter). Due to their unique and tunable structural, physical, and chemical properties, CNTs are used in environmental remediation as absorbents, catalysts or catalyst supports, membranes, and electrodes. However, a poorly understood determinant of the role of CNTs in water treatment is their interaction with chemical disinfectants (e.g., chlorine, chloramine, and ozone). To address these existing gaps in the environmental fate and reactivity of CNTs, this work establishes whether CNTs represent precursors for halogen and nitrogen containing disinfection byproducts (DBPs), which are products that form during a reaction of a disinfectant with organic matter in the water. In addition, we seek to understand how reaction with disinfectants alters CNT surface chemistry, and in turn impacts their environmental mobility and cytotoxicity. Finally, we determine how NOM and other aquatic variables known to impact DBP formation (e.g., Br−, NOM, and pH) influence the rate and products of CNT reaction with disinfectants. Outcomes of this work contribute to the current understanding of the role of carbon-based species as DBP precursors in disinfection and provide new context as to the environmental significance and implications of CNTs in natural and engineered aquatic systems.
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Afreh, Isaac K. "A Non-Biological Inhibition Based Sensing Technique (NIBS) for the Detection of Halogenated Disinfection By-Products in Water." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1366068222.
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Santana, Soraia Veloso Silva. "Avaliação da desinfecção do canal radicular frente ao preparo químico-cirúrgico por meio rotatório associado ou não a tratamento químico complementar." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/23/23145/tde-10072008-152331/.
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A desinfecção dos canais radiculares figura como constante preocupação clínica. Esta pesquisa teve a proposta de verificar o nível de desinfecção alcançado pela instrumentação mecanizada utilizando o sistema K3 em relação ao uso desse mesmo sistema associado a um tratamento químico dentinário complementar. Foram utilizados 16 caninos inferiores unirradiculares, que foram aleatoriamente divididos em dois grupos. Foram realizados 2 ensaios em dias diferentes, cada ensaio formado por 8 dentes em cada grupo. As coroas dos dentes foram cortadas e o tamanho das raízes padronizado em 15 mm. Os canais foram esvaziados com auxilio de limas tipo K de números 10 ou 15 com hipoclorito de sódio a 1% seguido de 20 mL de tiosulfato de sódio a 5%. Seguiu-se então a odontometria. Os dentes foram impermeabilizados externamente por duas camadas de cianoacrilato de etila e montados em tubos Eppendorf a expensas de adesivo epóxico. Os conjuntos (raiz + Eppendorf) foram esterilizados em autoclave por 20 min a 134 °C. Os espécimes foram inoculados com uma da suspensão correspondente à concentração bacteriana 0,5 da escala de Mc Farland (1,5 x 108 UFC). A primeira coleta microbiológica foi realizada imediatamente após o tempo de incubação para estabelecer o número de unidades formadoras de colônias. O preparo químicocirúrgico dos canais radiculares do grupo 1 foi realizado apenas por meio do sistema rotatório K3. Cones de papel absorvente esterilizados foram inseridos no canal radicular para nova coleta. Os dentes do Grupo 2 também tiveram os canais radiculares preparados com sistema rotatório K3 até a fase de irrigação-aspiração final com hipoclorito de sódio a 0,5% e EDTA-T a 17%. Após essa etapa foi realizado o tratamento químico da dentina que correspondeu à inserção de solução de hipoclorito de sódio a 1% no interior da cavidade pulpar e com uma lima tipo K de número 25 a solução foi agitada durante um minuto. Esse procedimento foi repetido 5 vezes num total de 10 mL dessa substância e somando um tempo de 10 minutos. A irrigação final foi efetuada com 10 mL de solução de hipoclorito de sódio a 0,5% seguidas de 20 mL de solução de EDTA- T a 17% (pH 7,0). Nova coleta para exame microbiológico foi realizada. Essas suspensões sofreram diluições seriadas de 10-1 a 10-7 em água peptonada antes do preparo químico-cirúrgico e de10-1 a 10-5 após o mesmo As diluições foram então semeadas em triplicata em placas contendo TSA. Após o período de 24 h de incubação as placas que apresentaram crescimento bacteriano tiveram o número de unidades formadoras de colônias (UFCs) determinado. Embora houvesse redução da população bacteriana em ambos os grupos no que se refere ao pré e pós-operatório, os resultados demonstraram que não houve diferença estatística significante entre os grupos de estudo (p>0,05).The effective disinfection of root canals represents a constant clinical concern. This research aimed at verifying the level of disinfection achieved by mechanical instrumentation using the K3 system when compared to the associated use of the same system and a complementary chemical dentinal treatment. Sixteen singlerooted lower canines were randomly divided into two groups. Two experiments, each using 8 teeth per group, were conducted on different days. The dental crowns were sectioned and the root length was standardized to 15 mm. The canals were instrumented using #10 or 15 K-files with 1% sodium hypochlorite, followed by 5% sodium thiosulfate. The root canals were measured. The teeth were made externally impermeable by two layers of ethyl cyanoacrylate and placed in Eppendorf tubes using epoxy resin. The compounds (root + Eppendorf) were sterilized in an autoclave for 20 min at 134oC. A suspension that corresponds to the bacterial concentration of 0.5 on the McFarland scale (1.5 x 108 CFU) was inoculated onto the specimens. The first microbiological sample collection was done immediately after incubation in order to determine the number of colony-forming units. Chemical preparation of the root canals of group 1 was done using the K3 rotatory system exclusively. Sterile paper cones were inserted into the canal for a new collection. Teeth from group 2 also had their root canals prepared using the K3 rotatory system up to the phase of final irrigation with 0.5% sodium hypochlorite and 17% EDTA-T. Next, chemical dentinal treatment was done by inserting a 1% sodium hypochlorite solution into the pulp cavity and agitating for one minute with the aid of a #25 K-file. This step was repeated 5 times using a total of 10 ml of the solution for a total duration of 10 minutes. Final irrigation was done using 10 ml of 0.5% sodium hypochlorite solution followed by 20 ml of 17% EDTA-T (pH 7.0). A new collection for microbiological examination was done. These suspensions underwent serial dilutions from 10-1 to 10- 7 using peptone water before preparation and from 10-1 to 10-5 afterwards. The dilutions were then inoculated thrice onto TSA plates. After an incubation period of 24h, the number of colony-forming units (CFU) was determined for the plates which presented with bacterial growth. Although there was a reduction of the bacterial population in both experimental groups when pre and post-operative counts were compared, results demonstrated that there was no statistically significant difference between the two study groups (p>0.05).
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Cubas, Gloria Beatriz de Azevedo. "Efetividade da antissepsia bucal prévia com clorexidina na prevenção da contaminação da moldagem com alginato e sua influência na distorção do material." Universidade Federal de Pelotas, 2012. http://repositorio.ufpel.edu.br/handle/ri/2270.
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Previous issue date: 2012-12-07The aims of this randomised controlled trial were to evaluate the influence of a preprocedural 0.12% chlorhexidine mouthrinse on the microbial contamination of dental impressions, subsequently disinfected with sodium hypoclorite or water (control). The second objective was to evaluate if aqueous solution of 0.12% chlorhexidine mixed with irreversible hydrocolloid powder would decrease microbial contamination of dental impressions. Forty subjects underwent maxillary dental impressions with irreversible hydrocolloid and were randomly divided into two groups (n=20) according to the preprocedural mouthrinse (0.12% chlorhexidine or placebo).The dental impressions were then divided into two subgroups and disinfected with sodium hypochlorite or water (control). In the second part, 20 subjects underwent maxillary dental impressions with irreversible hydrocolloid and randomly assigned into two groups according to the mixed agent used (0.12% chlorhexidine or water). Saliva and alginate samples were assessed for microbiological counts of total micro-organisms, total streptococci and Candida species. Surface roughness of the impressions and dimensional stability of the casts were also evaluated. Chlorhexidine preprocedural mouthrinse significantly reduced (p<0.05) microbial contamination. Small but significant alterations were produced on dimensional stability and surface quality when sodium hypochlorite was used as disinfectant after the impression (p=0.005). The results also showed that the use of aqueous 0.12% chlorhexidine mixed with the powder of irreversible hydrocolloid decreased the percentage of total micro-organisms and total Streptococci counts (p<0.001), without producing alterations in surface quality and dimensional stability. It can be concluded that 0.12% chlorhexidine used as preprocedural mouthrinse, or mixed with irreversible hydrocolloid powder, are effective methods in reducing microbial contamination of alginate impressions, without causing damage to the physical and mechanical properties of the material
Os objetivos deste ensaio clínico randomizado foram (I) avaliar a influência de um bochecho, com solução de clorexidina 0,12% e placebo, previamente a realização de moldagens bucais, posteriormente desinfetadas com hipoclorito de sódio ou água (controle) na contaminação de moldagens de alginato; e (II) avaliar se solução aquosa de clorexidina 0,12% misturada com o pó de hidrocolóide irreversível reduziria a contaminação microbiana de moldagens bucais.Quarenta voluntários foram submetidos a moldagens bucais com hidrocolóide irreversível e foram divididos de forma randomizada em 2 grupos (n=20) de acordo com a solução bucal (0,12% clorexidina ou placebo). As moldagens bucais foram divididas em 2 grupos e desinfetadas com hipoclorito de sódio ou água (controle). Na segunda parte do ensaio clinico, 20 voluntários foram submetidos a moldagens bucais com hidrocolóide irreversível e foram divididos em 2 grupos de acordo com a solução usada no preparo do alginato (0,12% clorexidina ou água).Amostras de saliva e alginato foram avaliados quanto a contagem microbiana de microrganismos totais, estreptococos totais e espécies de Candida. Rugosidade de superfície e estabilidade dimensional de modelos de gesso também foram avaliados. Bochecho com solução bucal de clorexidina reduziu de forma significativamente (p<0,005) a contaminação microbiana. Pequenas mais significativas alterações dimensionais e de rugosidade de superfície foram produzidas quando hipoclorito de sódio foi utilizado como agente desinfetante pós-moldagem (p=0,005). Os resultados também demonstraram que o uso de solução de clorexidina 0,12% misturada ao pó de hidrocolóide irreversível reduziu a percentagem de microrganismos totais e estreptococos (p<0.001), sem causar alterações de rugosidade de superfície e estabilidade dimensional. Pode ser concluído que o uso de solução de clorexidina 0,12% usada como bochecho bucal ou misturada ao pó de hidrocolóide irreversível são métodos eficientes na redução microbiana de moldagens de alginato, sem causarem danos as propriedades físicas e mecânicas do material
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Dehghan, Abnavi Mohammadreza Dehghan. "CHLORINE DECAY AND PATHOGEN CROSS CONTAMINATION DYNAMICS IN FRESH PRODUCE WASHING PROCESS." Cleveland State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=csu1624196282479244.
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Comäir, Christian B. "Disinfection of physico-chemically treated wastewater using medium pressure ultraviolet lamps." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56806.
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An ultraviolet pilot plant was installed at the Montreal Urban Community Wastewater Treatment Plant (MUCWTP) to assess the feasibility of employing a full scale UV disinfection system. Wastewater characteristics such as suspended solids (SS), turbidity, iron content, transmittance at 254 nm, and dissolved organic carbon were monitored to assess their effect on UV disinfection. Fecal coliforms were used as indicators to measure disinfection performance. UV disinfection was capable of reducing the fecal coliform counts from typical values of 0.2-3 million CFU/100ml (depending on the process and season) to thousands, hundreds or tens per 100 ml, depending on the dose applied, the process used for phosphorus removal, and wastewater quality. High turbidity values yielded higher surviving microbial counts; disinfection effectiveness decreased by 10% for each NTU of turbidity increase. SS in the wastewater scattered the UV light, leading to dose underestimations and the illusion that higher SS would yield better disinfection effectiveness. A photoreactivation increase of 8.1 and 11.7 fold was observed for iron-treated and alum-treated effluents respectively. Dark repair increases were very different for iron-treated and alum-treated effluents; however, in terms of dark repaired fraction, both effluents had values within the same range. UV disinfection was not found to cause any additional toxicity in the wastewater.
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Trozell, Oskar, Daniel Wiman, Elis Wiggins, Elin Stigenberg, Alva Bergström, and Emilia Andersson. "Sustainable water treatment processes : Scenarios for a better environment in Håbo municipality." Thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448625.
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Clean drinking water is a vital part of our society and a basic human right. With an ever growing population and a decreasing quality of raw water, new methods need to be introduced to keep up with the demand for clean, biostable, and sustainable production of drinking water. The aim of this study is to evaluate Håbo municipality’s increasing usage of chemicals in their water treatment process and to investigate current and future possible technologies for water treatment for Håbo to make their process more sustainable. In this study four scenarios of different cost and change of today’s water treatment plants are presented, while our overall recommendation is to build a new facility. A new plant with new treatment methods such as ultrafiltration is most in line with Håbo municipality’s vision of decreasing chemical usage and sustainability, all while maintaining the water quality. Due to Håbo’s growing population and today’s water plants running close to maximum capacity, a new facility with a larger capacity should be considered.
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Kfouri, Claire A. 1980, and Hyo Jin 1978 Kweon. "Seawater as coagulant substitute and the effects on disinfection in chemically enhanced primary wastewater treatment : a case study of Paraty, Brazil and the Deer Island wastewater treatment plant, Boston." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29565.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (leaves [133]-[135]).
Paraty is a small touristic city on the South Eastern coast of Brazil plagued with public health problems inherently linked to its poor water and sanitation practices. This thesis centers on the design of an appropriate wastewater treatment facility for the City. The new and interesting use of seawater as a wastewater treatment tool and its effect on the disinfection potential of the treated effluent is also reviewed and tested in a series of jar tests and laboratory experiments Chemically Enhanced Primary Treatment (CEPT) is a wastewater treatment method that serves as an attractive alternative to conventional primary treatment and can also be used as an efficient preliminary step to biological secondary treatment processes. CEPT adopts coagulation and flocculation and accomplishes remarkable increases in the removals of common pollutants and contaminants from the influent. CEPT was chosen as the most favorable treatment alternative for Paraty as it is an expandable, economic and highly efficient system. The main advantage to CEPT is to generate an effluent that can be efficiently and economically disinfected at a low cost compared to secondary treatment. The most optimal dose of FeCl3, polymer and seawater to treat the Paraty sewage were estimated at 40mg/L, 0.1 mg/L and 5% seawater by volume respectively. Jar tests were also conducted at the Boston Deer Island WWTP to check the efficiency of using seawater as a coagulation enhancement mechanism on saline influents. CEPT effluents treated with FeCl3 were also tested for disinfection with both Paracetic acid (PAA) and Chlorine. Although PAA is an effective disinfectant, it was not included due to its high cost. The optimal chlorine dose for Paraty was estimated at 3 mg/L. Additional tests were conducted to test for the disinfectability of the Deer Island effluent treated with CEPT. These tests helped show that the sensitivity of disinfection in the presence of seawater is limited by low seawater concentrations. This thesis concludes with a detailed design of the treatment plant sedimentation tanks, chlorination/dechlorination chambers, and grit removal facility dimensions and draws general encouraging conclusions on the suggested use of seawater as a coagulation catalyst in chemically enhanced primary wastewater treatment.
by Claire A. Kfouri and Hyo Jin Kweon.
M.Eng.
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Carre, Gaëlle. "Compréhension des mécanismes lors de la photocatalyse appliquée à la dégradation des microorganismes : application au traitement de l'air et aux textiles auto-décontaminants." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00998196.
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L'objectif principal de ce travail est d'étudier les mécanismes d'oxydation lors de la photocatalyse (TiO2 irradié sous UV-A) appliquée à la dégradation des microorganismes et leurs effets sur les composants cellulaires. L'étude de l'efficacité antimicrobienne de TiO2 sur un panel de microorganismes (bactéries, spores, champignons) réalisée dans différents milieux (TiO2 en milieu riche, 'sec', en phase liquide) montre l'influence des méthodes d'évaluation, de test et de comptage sur les efficacités d'inactivation. Des études menées en présence de molécules scavengers d'anions superoxydes (O2°-) mettent en évidence l'implication des O2°- dans l'effet antibactérien et dans la peroxydation lipidique. Au niveau protéomique, diverses cibles d'action potentielles du TiO2 sont aussi proposées. Enfin, une partie applicative détermine l'efficacité antimicrobienne de dispositifs photocatalytiques équipés de mousses alvéolaires de β-SiC et de diodes électroluminescentes, et met en avant les propriétés auto-désinfectantes sous lumière solaire de textiles photocatalytiques fonctionnalisés par la technique layer-by-layer.
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Brown, Travis. "Inactivation of Bacteriophage Φ6 on Tyvek Suit Surfaces by Chemical Disinfection." 2015. http://scholarworks.gsu.edu/iph_theses/440.
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The 2014 West Africa Ebola outbreak saw a substantial number of healthcare workers (HCWs) being infected, despite the use of personal protective equipment (PPE). PPE is intended to protect HCWs when caring for patients with Ebola virus disease (EVD), but PPE may play a role in the spread of Ebola in healthcare environments. Before the removal of PPE, chemical disinfection may prevent the transfer of pathogens to HCWs, but the efficacy of common disinfectants against enveloped viruses, such as Ebola, on PPE surfaces is relatively unknown. The purpose of this study is to assess the efficacy of two common disinfectants, chlorine bleach (Clorox® bleach) and quaternary ammonium (Micro-Chem Plus®), used in healthcare settings for inactivation of enveloped viruses on PPE. The virucidal activity of the two disinfectants were tested against bacteriophage Φ6, an enveloped, non-pathogenic surrogate for enveloped viruses, on Tyvek suit surfaces. Virus was dried onto Tyvek suit surface, exposed to the disinfectants at use-dilution for a contact time of one minute, and the surviving virus was quantified using a double agar layer (DAL) assay. The Clorox® bleach and Micro-Chem Plus® produced a >3.21 log10 reduction and >4.33 log10 reduction, respectively, in Φ6 infectivity. The results of this study suggest that chlorine bleach and quaternary ammonium are effective in the inactivation of enveloped viruses on Tyvek suit surfaces. Chemical disinfection of PPE should be considered as a viable method to reduce the spread of pathogenic, enveloped viruses to HCWs, patients, and other environmental surfaces in healthcare settings.
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Malheiro, Joana Filipa Fernandes. "Development of Biocide Formulations Based on Phytochemical Products for Surface Disinfection." Tese, 2020. https://hdl.handle.net/10216/130105.
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Malheiro, Joana Filipa Fernandes. "Development of Biocide Formulations Based on Phytochemical Products for Surface Disinfection." Doctoral thesis, 2020. https://hdl.handle.net/10216/130105.
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Amos, Steve A. "Ultraviolet disinfection kinetics for potable water production." 2008. http://hdl.handle.net/2440/50044.
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Irradiation with ultraviolet (UV) light is used for the disinfection of bacterial contaminants in the production of potable water, and in the treatment of selected wastewaters. However, efficacy of UV disinfection is limited by the combined effect of suspended solids concentration and UV absorbance. Limited published UV disinfection data are available that account for the combined effects of UV dose, suspended solids concentration and UV absorbance. This present lack of a rigorous quantitative understanding of the kinetics of UV disinfection limits process optimisation and wider application of UV treatment. The development and validation of an adequate model to describe UV disinfection kinetics presented in this thesis can therefore be justified by an increased confidence of reliability of design for UV disinfection. Using the published data of Nguyen (1999), four established model forms were assessed to account for the combined effect of suspended solids and/or soluble UV absorbing compounds, and UV dose on the efficacy of disinfection. The four model forms were: a log-linear form, Davey Linear-Arrhenius (DL-A), Square-Root (or Ratkowsky- Belehradek) and a general nth order Polynomial (nOP) form that was limited to a third order. Criteria for assessment of an adequate predictive model were established including: accuracy of predicted against observed values, percent variance accounted for (%V), and; appraisal of residuals. The DL-A model was shown to best fit the data for UV disinfection of Escherichia coli (ATCC 25922); followed by the nOP, log-linear and Square-Root forms. However, the DL-A form must be used in conjunction with a first-order chemical reaction equation, and was shown to predict poorly at high experimental values of UV dose (> 40,000 μWs cm-2). The DL-A model was not amenable to extrapolation beyond the observed UV dose range. To overcome the shortcomings of the Davey Linear-Arrhenius model synthesis of two new, non-linear model forms was undertaken. The two models were a modified exponentially damped polynomial (EDPm) and a form based on the Weibull probability distribution. The EDPm model has three terms: a rate coefficient (k), a damping coefficient (λ), and; a breakpoint dose ([dose]B). The rate coefficient governs the initial rate of disinfection prior to the onset of tailing, whilst the breakpoint is the UV dose that indicates the onset of tailing. The damping coefficient controls curvature in the survivor curve. The Weibull model has just two terms: a dimensionless scale parameter (β0), and; a shape parameter (β1). The scale parameter represents the level of disinfection in the tail of the survivor curve (as log10 N/N0), whilst the shape parameter governs the degree of curvature of the survivor data. Each model was assessed against the independent and published UV disinfection data of Nelson (2000) for treatment of faecal coliforms in a range of waste stabilisation pond effluents. Both models were found to be well suited to account for tailing in these UV disinfection data. Overall, the EDPm model gave a better fit to the data than the Weibull model form. To rigorously validate the suitability of the new EDPm and Weibull models a series of experimental trials were designed and carried out in a small-scale pilot UV disinfection unit. These trials included data determined specifically at low values of UV dose (<10,000 μWs cm-2) to fill the gap in the experimental data of Nguyen (1999). The experimental trials were carried out using a commercially available, UV disinfection unit (LC5TM from Ultraviolet Technology of Australasia Pty Ltd). Purified water contaminated with Escherichia coli (ATCC 25922) with a range of feed water flow rates (1 to 4 L min-1) was used. E. coli was selected because it is found in sewage, or water contaminated with faecal material, and is used as an indicator for the presence of enteric pathogens. E. coli should not be present in potable water. The hydrodynamics of water flow within the disinfection unit were established using digital video photography of dye trace studies with Methylene Blue. Nominal UV dose (2,700 to 44,200 μWs cm-2) was controlled by manipulating the flow rate of feed water through the UV disinfection unit (i.e. residence time), or by varying the exposed length of the control volume of the disinfection unit. The transmittance of the feed water (at 254 nm) was adjusted by the addition of either a soluble UV absorbing agent (International RoastTM instant coffee powder; 0.001 to 0.07 g L-1), or by addition of suspended matter as diatomaceous earth (Celite 503TM; 0.1 to 0.7 g L-1, with a median particle size of 23 μm). The absorbing agent (instant coffee), when in a comparable concentration, was found to produce a greater reduction in water transmission than the suspended material (Celite 503TM). It therefore contributed to a greater reduction in the initial rate of disinfection. Neither agent was found to produce a systematic reduction in the observed efficacy of disinfection however. Experimental results highlight that in the absence of soluble absorbing agents, or suspended solids, the initial rate of disinfection is higher when fewer viable bacteria are initially present. Both the new EDPm and Weibull forms gave a good fit to the experimental data. The EDPm better fitted the data on the basis of residual sum-of-squares (0.03 to 2.13 for EDPm cf. 0.16 to 4.37 for the Weibull form). These models are both of a form suitable for practical use in modelling UV disinfection data. Results of this research highlight the impact of water quality, as influenced by the combined effect of UV dose, suspended solids concentration and UV absorbance, on small-scale UV disinfection for potable water production. Importantly, results show that the concentration of soluble UV absorbing agents and suspended solids are not in themselves sufficient criteria on which to base assessment of efficacy of UV disinfectionhttp://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1342403
Thesis (M.Eng.Sc.) - University of Adelaide, School of Chemical Engineering, 2008
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"Closed system alkaline biosolids disinfection and the development of activated carbon from municipal and poultry wastes." Tulane University, 2004.
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Νέλος, Δημήτριος. "Αξιολόγηση τεχνολογίας για τη διαχείριση επικίνδυνων ιατρικών αποβλήτων." Thesis, 2009. http://nemertes.lis.upatras.gr/jspui/handle/10889/2817.
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Το πρόβληµα της διαχείρισης των ιατρικών αποβλήτων και ιδιαίτερα αυτών που χαρακτηρίζονται ως επικίνδυνα έχει οξυνθεί τα τελευταία χρόνια στην Ελλάδα. Το 10-25% των παραγόμενων ιατρικών αποβλήτων στις υγειονομικές μονάδες, θεωρούνται επικίνδυνα, με δυνατότητα πρόκλησης μίας σειράς κινδύνων για την υγεία, σε περίπτωση επαφής ή έκθεσης σε αυτά, διότι αποτελούν στις περισσότερες των περιπτώσεων φορείς παθογόνων µικροοργανισµών µε αποτέλεσµα η µη ασφαλής διάθεσή τους να εγκυμονεί σηµαντικότατους κινδύνους, όχι µόνο για το περιβάλλον, αλλά και για τη δηµόσια υγεία.
Αντικείμενο της παρούσας εργασίας αποτελεί η μελέτη και η αξιολόγηση μεθόδων επεξεργασίας των επικίνδυνων ιατρικών απορριμμάτων. Ο όρος αξιολόγηση αναφέρεται στην διαδικασία επιλογής της κατάλληλης τεχνολογίας επεξεργασίας, λαμβάνοντας υπόψιν πληθώρα παραγόντων. Οι πιο διαδεδομένες μέθοδοι που θα εξεταστούν, είναι η αποτέφρωση, η αποστείρωση, η απολύμανση με μικροκύματα και η χημική απολύμανση.
Σκοπός της εργασίας είναι να καταστήσει σαφές το ότι καμία μέθοδος δεν αποτελεί πανάκεια. Αντιθέτως, πρέπει να γίνεται προσεκτική επιλογή της μεθόδου, πάντα με σεβασμό στην υγεία και το περιβάλλον.The problem of medical waste management, and especially of that which is characterized as hazardous, has increased in Greece during the last years. Hazardous medical waste is 10-25% of the total quantity of medical waste that is produced in health units. In most cases, this type of medical waste is carrier of pathogenic microorganisms. Thus, its ineffective way of disposal puts in danger the environment and the public health. This thesis is an assessment of different technologies that can manage hazardous medical waste. The term assessment refers to the choice of the appropriate technology, taking into account many different factors. The most widely used methods are incineration, sterilization, disinfection with microwave irradiation and chemical disinfection. Aim of this thesis is to make clear that there is not any technology that is really effective with all types of hazardous medical waste. Thus, we have to carefully choose the appropriate technology, always with respect to health and the environment.