• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 146
  • 47
  • 29
  • 14
  • 13
  • 13
  • 4
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 347
  • 347
  • 104
  • 72
  • 53
  • 42
  • 41
  • 37
  • 29
  • 29
  • 27
  • 26
  • 26
  • 23
  • 22
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

Quantificação do risco à saúde humana pela exposição a poluentes químicos e potencial carcinogênico às comunidades adjacentes ao Rio Pardo, Brasil / Human health risk quantification from exposure to chemical pollutants and carcinogenic potential to communities adjacent to the Pardo River, Brazil

Carolina Sampaio Machado 07 December 2016 (has links)
Compostos químicos de origem natural e artificial são incorporados aos seres humanos por diversas vias, sendo elas ingestão, inalação e contato dérmico. O presente estudo tem como objetivo quantificar o risco para a saúde humana pela exposição a pesticidas e metais detectados no Rio Pardo, Brasil. Foram realizadas campanhas de coleta de dados em 6 pontos ao longo do Rio Pardo durante períodos chuvosos e secos entre os anos de 2014 e 2015. Três espécimes de peixes do Rio Pardo foram adquiridos com pescadores e outros três espécimes foram adquiridos em mercado no município de Ribeirão Preto, SP. Foram analisados os inseticidas organoclorados pp\'-DDE, pp\'-TDE, pp\'-DDT, ?- BHC, ?-BHC, ?-BHC, heptacloro, heptacloro epóxido, aldrin, dieldrin, endrin, ?- endossulfan, ?-endossulfan e endossulfan sulfato. Os herbicidas nitrogenados quantificados na água foram ametrina, atrazina, desetilatrazina, diuron, hexazinona, metribuzim, simazina e tebutiuron. Os metais quantificados nas amostras de água, sedimento e peixes foram Al, As, Be, Cd, Cr, Cu, Pb, Mn, Hg, Ni, Tl, Sn, V e Zn. Realizou-se amostragem passiva pelo método DGT para quantificação da fração biodisponível dos metais na água. A avaliação de risco para saúde humana por meio da exposição aos metais e herbicidas foi realizada considerando o cenário residencial. Foram detectados metabólitos de DDT e DDD em níveis inferiores aos limites permitidos pela legislação internacional. Os herbicidas nitrogenados foram detectados em cinco dos seis pontos de coleta analisados no Rio Pardo, sendo que para atrazina as concentrações variaram de 0,16 a 0,32 µg/L, acima dos valores permitidos pela União Europeia (0,1 µg/L). As análises de metais na água indicaram que Al, Cd, Cu, Hg, Mn, Pb e Zn apresentaram concentrações acima dos limites recomendados pela legislação brasileira. O pH da água variou de 5,7 a 7,8. Os níveis de alguns metais nos sedimentos foram maiores no ponto 1, sugerindo fonte de poluição pontual provavelmente relacionada a afluente contaminado. A determinação de metais em peixes indicou que a espécie P. glauca apresentou concentração acima dos limites estabelecidos pela legislação brasileira para As (7,23 µg/g). A avaliação de risco não carcinogênico pela ingestão de água indicou que os níveis de herbicidas não representaram risco. Já para metais, todos os pontos de coleta tanto no período seco quanto chuvoso apresentaram HI>1, sendo que o metal que mais contribuiu com os resultados foi o Al. A avaliação de risco carcinogênico indicou que para As os seis pontos de coleta avaliados estavam acima dos valores considerados aceitáveis (<10-6 ) no período chuvoso. A avaliação de risco não carcinogênico associado à ingestão de peixes indicou que as espécies Salmo spp. e P. glauca apresentaram HIs acima dos níveis considerados seguros. Risco carcinogênico associado à exposição ao As para adultos pela ingestão de peixes destacou as espécies P. glauca, Salmo spp. e S. brasiliensis como potenciais causadoras de risco carcinogênico. A PCA mostrou que 94,31% da variação dos dados foram explicadas pelos cinco primeiros componentes principais. As contaminações determinadas no Rio Pardo indicam que medidas devem ser adotadas pelas autoridades competentes, visando minimizar os riscos às saúde humana / Chemical compounds of natural and artificial origin are incorporated to human body in different ways, they are ingestion, inhalation and dermal contact. This study aims to quantify the risk to human health from exposure to pesticides and metals detected in Pardo River, Brazil. Data collection campaigns were conducted in 6 points along the Pardo River during rainy and dry periods between 2014 and 2015. Three fish specimens from Pardo River were acquired with fishermen and three specimens were acquired on a Ribeirão Preto, SP, market. The organochlorine insecticides analyzed were pp\'-DDE, pp\'-TDE, pp\'-DDT, ?-BHC, ?-BHC, ?-BHC, heptachlor, heptachlor epoxide, aldrin, dieldrin, endrin, ?-endosulfan, ?-endosulfan and endosulfan sulfate. Herbicides quantified in the water were ametrin, atrazine, deethylatrazine, diuron, hexazinone, metribuzin, simazine and tebuthiuron. Metals quantified in water, sediment and fish were Al, As, Be, Cd, Cr, Cu, Pb, Mn, Hg, Ni, Tl, Sn, V and Zn. Passive sampling was performed with DGT method, for the bioavailable fraction quantification of metals in water. The risk assessment through the exposure to metals and herbicides were considering the residential scenario. DDT and DDD metabolites were detected at levels below to the limits permitted by international thresholds. Herbicides were detected in five of the six sampling points analyzed in the Pardo River, and for atrazine concentrations ranged from 0.16 to 0.32 µg/L, above the levels allowed by the European Union (0.1 µg/L). Metal analyses in water indicated that Al, Cd, Cu, Hg, Mn, Pb and Zn showed concentrations above the limits recommended by Brazilian legislation. The water pH ranged from 5.7 to 7.8. The levels of some metals in sediments were higher in sampling point #1, suggesting punctual source of pollution, probably related to contaminated tributary. The determination of metals in fish indicated that P. glauca showed concentrations above the limits established by Brazilian legislation (7.23 µg/L). Non-carcinogenic risk assessment for water intake indicated that the herbicide levels did not represent risk. For metals, all sampling points both rainy and dry season showed HI>1, and the metal that contributed to the results was Al. The evaluation of carcinogenic risk indicated that all of the six sampling points assessed were above the levels considered acceptable (<10-6 ) during the rainy season. The non-carcinogenic risk assessment associated with fish intake indicated that the species Salmo spp. and P. glauca showed HIs above to the levels considered safe. Carcinogenic risk associated to fish intake indicate that the species P. glauca, Salmo spp. and S. brasiliensis represented potential carcinogenic risk. The PCA showed that 94.3% of the data variation was explained by five main components. Contaminations determined in the Pardo River indicate that measures should be taken by the competent authorities in order to minimize the human health risks
242

Ämnestransport med grundvatten i hydrogeologiska typmiljöer

Winnerstam, Björn January 2005 (has links)
Certain types of waste, e.g. bottom ash originating from municipal solid waste incineration (MSWI bottom ash) can be used as road construction materials. A potential problem is the possibility of substances leaching out of the road and spreading in the surrounding groundwater. The aim of this master’s thesis is to conclude whether hydrogeological type settings can be employed to, based on local conditions, provide an estimate of the probable spreading of these substances in the surrounding groundwater, and whether certain types of soils can be identified as being less suitable for the localization of a MSWI bottom ash road. A hydrogeological type setting is defined as a mappable unit with similar hydrogeological properties. An advantage of this approach would be that mainly existing maps and surveys could form the basis for the assessment. The work has been performed by placing a hypothetical road construction in different hydrogeological type settings. The expected patterns of spreading has then been evaluated using theoretical reasoning and analytical and numerical models. The method can be used. In the report various type settings are defined. In several cases further information will be required to render possible a more exact estimate of the spreading. By locating the road on less permeable soils to reduce the local spreading of substances in groundwater, a greater proportion of the water will be drained as surface water. Thus it becomes important to take into account surface water transport aswell. In the report a procedure to estimate the maximum concentrations in groundwater at locations situated downstream the road is presented. This estimate could be used as basis for a more balanced valuation of appropriateness, e.g. by relating the estimated concentrations to background values. / Vissa typer av avfall, exempelvis slaggrus (sorterad bottenaska från avfallsförbränning), kan användas som vägbyggnadsmaterial. Ett potentiellt problem är möjligheten att ämnen lakas ut ur vägen och sprids i omgivande grundvatten. Syftet med detta examensarbete är att avgöra om hydrogeologiska typmiljöer kan användas för att, utifrån omgivningens förutsättningar, ge en bild av hur den vidare spridningen av dessa ämnen i omgivande grundvatten sannolikt ser ut, och om vissa typer av mark kan pekas ut som mindre lämpade för lokalisering av en slaggrusväg. En hydrogeologisk typmiljö definieras som ett område möjligt att avgränsa med avseende på karakteristiska hydrogeologiska förhållanden. En fördel med angreppssättet skulle vara att underlagsmaterialet till bedömningen då kan utgöras av i huvudsak befintligt kartmaterial. Studien har utförts genom att en hypotetisk vägkonstruktion placerats in i olika hydrogeologiska typmiljöer. De troliga spridningsscenarierna har sedan utvärderats genom teoretiska resonemang, samt genom användande av analytiska och numeriska modeller. Metodiken går att använda och i rapporten definieras olika typmiljöer. I flera fall kommer platsspecifik kunskap behöva inhämtas för en närmare beskrivning av spridningsbilden. Genom placering av vägen på tätare mark för att minska lokal spridning av ämnen i grundvatten kommer en större andel av vattnet att avledas som ytvatten. Därmed blir det viktigt att även inhämta kunskap om transport med ytvatten. I rapporten presenteras också en metod för uppskattning av maximala halter i grundvatten nedströms en väg. Denna metod kan användas som underlag för en mer nyanserad värdering av lämplighet, genom att de uppskattade halterna relateras till bakgrundsvärden eller lämpliga riktvärden.
243

Development of a transitioning approach to reduce surface water volumes in combined sewer systems

Smith, Kerry W. S. January 2016 (has links)
The overarching goal of this research is to establish a successful forum for a transition from the existing paradigm of managing wastewater infrastructure to a more sustainable paradigm that achieves a more efficient utilisation of wastewater assets. A transitioning approach to support a more efficient utilisation of surface water and wastewater assets and infrastructure is proposed and developed. The determined transitioning approach possesses key stages namely developing the arena, developing the agenda, case study, and monitoring. The case study stage investigates a drainage utility identifying their improvement drivers, the removal of surface water through detailed drainage modelling and the financial examination of the costs incurred under the various scenarios conducted. Understanding the implications of removing/attenuating surface water from the network is improved through obtaining data by detailed drainage modelling. Infoworks software is used to investigate and assess the current and future operational scenarios of a wastewater system operating over one calendar year. Modelling scenarios were conducted removing surface water from selected areas focusing on the volumes requiring pumping and durations of pumping station(s) operation prior to treatment during storm conditions. The financial implication of removing surface water in combined sewer systems is examined in three main components. Firstly the costs of electricity incurred at the single sewage pumping station (SPS) investigated during the various scenarios modelled require to be addressed. Secondly the costs to retrofit sustainable urban drainage system (SUDS) solutions needs to be identified. Thirdly the implications of removing surface water for the drainage utility at the national level and the potential saving for householder’s committing to a surface water disconnection rebate scheme. When addressed at the macro level i.e., with over 2,100 pumping stations, some operating in sequence and contained within one drainage utility annually treating 315,360 megalitres the significance of the same multiple quantifiable and intangible benefits becomes amplified. The research aims, objectives and findings are presented to the identified and convened stakeholders. The transitioning approach developed encourages positive discourse between stakeholders. The level of success of the transitioning approach determined is then tested using a quantitative methodology through the completion of questionnaires. From the questionnaires completed the respondents unanimously agreed that surface water flows should be removed as well as reduced from the combined sewer system. The respondents agreed that the removal of surface water from a typical combined sewer system is justified by applying a transitioning approach focusing on the energy consumption required to pump increased volumes during storm events. This response is significant based upon the economic evidence and is contrary to the respondents previous position that finance was their most influencing factor. When provided with other potentially available benefits the respondents were even more supportive of the justification to remove surface water from the combined sewer system. The combined findings of the work presented in this thesis provide further justification that the transitioning approach applied to the removal of surface water from a typical combined sewer system, as determined in this research has been successful.
244

The Detection of Amazonian Manatees (Trichechus inunguis) Using Side-Scan Sonar and the Effect of Oil Activities on Their Habitats in Eastern Ecuador

Brice, Caitlin E. 01 May 2014 (has links)
Substantial hunting pressure and habitat destruction caused by oil extraction has critically endangered the Amazonian manatee in Ecuador. The current population status is unknown because an effective method to observe them in the wild has yet to be developed. This study explored whether the Amazonian manatee persists or has been extirpated in the eastern Ecuadorian Amazon utilizing side-scan sonar to increase odds of detection. Spatial differences in probability of detection were quantified if manatees were observed. The level of chemical contamination was determined and compared spatially and temporally against historical data. Data were collected using opportunistic transect surveys and grab sampling of surface water in Yasuni National Park, Lagartococha, and Cuyabeno Wildlife Reserve. Surveys confirmed that the manatee population is extant. Manatees were encountered more often in Cuyabeno Wildlife Reserve than in Lagartococha and Yasuni. Side-scan sonar detected more manatees than previously reported in 1996-1999. Side-scan sonar is a viable method for detection of manatees in the Ecuadorian Amazon system and resulted in greater detection as a function of effort. All future population studies should incorporate side-scan sonar. Lead, arsenic, mercury, polynuclear aromatic hydrocarbons [PAHs], and volatile organic compounds [VOCs] were not detected in the waters of the study region. High total petroleum hydrocarbon [TPH] levels were measured in 7 samples from Yasuni National Park. The concentrations of TPH were higher in Yasuni National Park than in Lagartococha and Cuyabeno. TPHs were detected only in the study region with a recent oil spill; there was no evidence that TPHs were higher near oil production wells and pipelines. The concentrations of TPH were significantly different than those measured in 1998 (z =3.01710, p=0.0026). A dedicated study should be performed to develop a protocol for monitoring persistent oil contaminants in the Ecuadorian Amazon and determine their sink.
245

Porovnání vlivu různé délky inkubační doby na hodnotu BSK / Influence of the various incubation time on the value of BOD

Debnárová, Andrea January 2010 (has links)
Biochemical Oxygen Demand (BOD) is commonly used for determining how fast biological organisms use up oxygen in a body of water. It is one of the essential methods used in water quality management and assessment. BOD could be considered as a quality level indicator of biologically treated water. This process is very time-dependent but most common period of incubation is five days - BOD(5). In this thesis different periods of incubation are compared - for BOD(5) with five days incubation period and BOD(2+5) with five days incubation period but also placed for two days to lowered temperature environment. These comparative tests were made for different types of water (surface water, waste water - water from mechanical level and biological level of treatment) For all kinds of determination of BOD the dilution method was used (ČSN EN 1899).
246

Dynamique de la contamination virale dans un environnement hydrique urbain / Dynamics of viral contamination in an urban water environment

Prevost, Benoit 28 September 2015 (has links)
Les virus entériques sont l'une des principales causes d'épidémies de gastroentérites chez l'Homme. Ces virus sont essentiellement excrétés dans les selles et sont donc observés en grande quantité au sein des eaux usées. L'abattement viral est très variable en fonction des types de traitements mis en place dans les stations d'épurations (STEP). Malgré ces traitements, la grande majorité des STEP rejettent d'importantes quantités de virus entériques dans l'environnement. L'objectif de ce travail a été d'apporter des éléments de réponse concernant la circulation des virus entériques humains dans un environnement hydrique urbain. Pour cela, des méthodes d'analyse ont été mises au point afin de permettre la détection d'un large panel de virus entériques dans différentes matrices hydriques susceptibles d'être étudiées dans l'environnement. Trois contrôles ont été développés afin de vérifier le bon déroulement de cette méthode et donc de valider les résultats obtenus. Une campagne d'échantillonnage a été réalisée au niveau d'un tronçon de la Seine impacté par les affluents naturels et des effluents de STEP. La prise en compte des débits au niveau des différents points de prélèvement a permis de calculer les flux viraux qui correspondent à la quantité de virus circulant en un point au cours d'une unité de temps. Cette approche a permis de démontrer la contribution majeure des effluents de STEP dans la contamination virale du milieu récepteur. Parmi l'ensemble des virus entériques recherchés, les adénovirus, les norovirus, les astrovirus et les rotavirus présentaient les charges virales les plus importantes dans les effluents de STEP et dans les eaux de surface. Leurs quantités au sein de ces matrices d'eau étaient les plus importantes durant la période hivernale ce qui était cohérent avec les données épidémiologiques. Un lien étroit entre l'état sanitaire de la population humaine reliée au réseau d'assainissement et la concentration en virus entériques des effluents de STEP et des eaux de surface a pu être établi. Sur ces mêmes prélèvements, l'étude de la diversité des astrovirus et des norovirus de génogroupes I et II a été réalisée par pyroséquençage. Cette approche a permis d'établir un profil des différents génotypes circulant dans les effluents de STEP. Au regard des données épidémiologiques recueillies sur la même période par le Centre National de Référence des virus entériques, un grand nombre de génotypes communs ont pu être observés entre ces deux jeux de données. Ce constat met en évidence le caractère informatif de l'analyse des effluents de STEP qui fournit un profil relativement pertinent des virus entériques circulant dans l'environnement mais aussi dans la population humaine. La présence de virus entériques présente dans les eaux de surface, ressources utilisées pour la potabilisation, est un réel problème de santé publique. C'est pourquoi la dernière partie de ce travail s'intéresse à évaluer leur persistance dans l'eau de surface et l'eau destinée à la consommation humaine, mais aussi face à des traitements de désinfection, fréquemment utilisés dans les usines de potabilisation et parfois en sortie de STEP. L'absence de modèle cellulaire pour la plupart de ces virus nous a conduit à développer une approche basée sur l'emploi d'agents intercalants permettant d'évaluer l'intégrité de la capside des particules virales détectées par PCR en temps réel. L'utilisation de ces agents intercalants s'est avérée pertinente à partir du moment où les conditions conduisent à une dégradation des capsides virales. Par conséquent, leur emploi sur des échantillons d'eau potabilisée a permis une meilleure estimation du risque sanitaire associé à la consommation de l'eau produite. En conclusion, ce travail propose des méthodes d'analyse qui ont permis de mettre en exergue les relations existantes entre la circulation des virus entériques dans l'environnement et l'état sanitaire de la population humaine / Enteric viruses are a major cause of gastroenteritis outbreaks in humans. These viruses are mainly excreted in the faeces and are therefore observed in large amounts in wastewater. Depending on the types of treatments, virus removal from effluent may vary from one wastewater treatment plants (WWTP) to another. Despite these treatments, most of the WWTP releases significant quantities of enteric viruses in the environment. The aim of this study was to better understand the circulation of human enteric viruses in urban rivers. For this purpose methods have been developed to enable the detection of a broad panel of enteric viruses in various water matrices that may be collected from the environment. Since there is important inhibition observed in this type of water samples, three controls were developed to verify the success of this method, from the sample concentration to the PCR quantification, and thus to validate the results. A sampling campaign was carried out at the Seine River section (Paris area) affected by its natural tributaries and WWTP effluents. The river and effluent flows at the different sampling points were used to calculate the viral flows as the amount of virus circulating at a point during a time unit. This approach has demonstrated the major implication WWTP effluents in the viral contamination of the Seine River. Among all the targeted enteric viruses, adenoviruses, norovirus, astrovirus and rotavirus showed the most significant viral loads in WWTP effluents and consequently in river waters. Their quantities in WWTP effluents and surface water were the most important during the winter period which was consistent with the epidemiological data from the French Reference Center for enteric viruses. A close connection between the health status of the Parisian population and enteric virus concentration in WWTP effluents and in the Seine River could be established. The study of the diversity of astrovirus and norovirus of genogroups I and II was carried out by pyrosequencing on WWTP effluent and Seine river samples to develop a profile of the different genotypes circulating in the environment. Many common genotypes were observed between the effluent dataset and the epidemiological data collected over the same period by the French Reference Center. These results highlight the complementarity of the two datasets, and the fact that WWTP effluents provide a relevant profile of enteric viruses circulating in the environment but also in the human population. The amount of enteric viruses present in drinking water resources such as surface waters is a real public health problem. Therefore, it is important to evaluate viral persistence in surface waters during tertiary treatment and in drinking water, but also the viral persistence after usual disinfection treatments such chlorination and ultraviolet treatment. The absence of cell model for culture of most enteric viruses, has led us to develop a method using intercalating dyes to assess the capsid integrity of the viral particles quantified by real time PCR. The use of these intercalating agents was relevant when the environmental conditions and disinfection treatments caused a degradation of the viral capsid. Consequently, their use for the analysis of water samples from drinking water plants allowed to prevent an overestimation of the risk of transmission to humans by the consumption of tap water. In conclusion, this work provides development of analysis methods highlighting the relationships between the circulation of infectious enteric viruses in the environment and the health status of the human population
247

Distribution d'estrogènes et de bêtabloquants dans les stations d'épuration des eaux résiduaires et dans l'eau de surface / Fate of estrogens and beta blockers in wastewater treatment plants and surface waters

Gabet-Giraud, Virginie 14 December 2009 (has links)
Les estrogènes et les bêtabloquants transitent quotidiennement par les réseaux d’assainissement et les stations d’épuration des eaux résiduaires urbaines. Une première partie de ce travail a consisté à développer des méthodes pour analyser ces micropolluants émergents dans les boues de station d’épuration et les matières en suspension. L’efficacité des traitements épuratoires a ensuite été évaluée vis-à-vis de l’élimination de ces molécules. En règle générale, les 5 estrogènes étudiés (estrone, 17α- et 17β-estradiol, estriol, 17α-éthinylestradiol) sont plutôt bien éliminés par les stations d’épuration avec des efficacités d’élimination généralement supérieures à 90%. Pour les 10bêtabloquants analysés (acébutolol, aténolol, bêtaxolol, bisoprolol, métoprolol, nadolol, oxprénolol,propranolol, sotalol et timolol), des comportements différents ont été observés. Alors que l’acébutololet le nadolol sont éliminés (abattements moyens supérieurs à 80%), d’autres molécules comme lesotalol et le propranolol ne sont que peu impactées par les traitements épuratoires (abattements moyens inférieurs à 20%). Pour les autres bêtabloquants étudiés, des abattements intermédiaires (entre 40 et 70%) sont observés. Excepté le propranolol, qui est le plus hydrophobe des bêtabloquants étudiés, les molécules ciblées dans cette étude s’adsorbent peu sur les matières en suspension (en moyenne 90% des molécules se trouvent dans la phase dissoute) et ne sont pas concentrées dans les boues ; les abattements mesurés correspondent donc, sauf pour le propranolol,à une biodégradation et pas à un transfert des micropolluants vers les boues. Les molécules résiduelles non éliminées par le traitement épuratoire rejoignent le milieu aquatique récepteur. Les rejets de station d’épuration représentent en effet une source de contamination pour les milieux aquatiques et l’impact de ces rejets est visible, notamment en termes d’augmentation des concentrations de micropolluants mesurées dans le milieu. Néanmoins, les faibles concentrations mesurées ne semblent pas individuellement représenter de risque environnemental majeur ; seul le propranolol a présenté sur 4 des 15 sites étudiés un quotient de risque supérieur à 1 ce qui indique un risque environnemental probable. Cependant, même si le risque associé à une molécule est faible,chaque molécule présente dans l’environnement contribue au potentiel toxique global des substances présentes dans l’environnement. / Estrogens and beta blockers are daily excreted by human beings and wastewater treatmentplants are recognised as the main pathway of these emerging micropollutants to the aquaticenvironment. This study aims at analyzing 5 estrogens (estrone, 17α- and 17β-estradiol, estriol, 17α-ethynylestradiol) and 10 beta blockers (acebutolol, atenolol, betaxolol, bisoprolol, metoprolol, nadolol, oxprenolol, propranolol, sotalol et timolol) in urban wastewater treatment plants and surface waters.First of all, methods were developed for the analysis of target molecules in sewage sludge and suspended particulate matters. Then, estrogens and beta blockers were studied in urban wastewater treatment plants. Generally, wastewater treatments are efficients to remove estrogens fromwastewater with mean removal rates above 90%. For beta blockers, acebutolol and nadolol areefficiently removed (mean removal rates of about 80%), while sotalol and propranolol are hardlyimpacted by wastewater treatment (mean removal rates below 20%). Other studied beta blockerspresent intermediate removal rates (between 40 and 70%). Except propranolol which is the lesshydrophilic molecule among the different studied beta blockers, target molecules are not adsorbed onsuspended particulate matters (mean proportion of 90% of the target molecules are present in the dissolved phase) and are not concentrated into sludge. So, calculated removal rates correspond,except for propranolol, to biodegradation and not to transfer into sludge. Residual molecules which are not removed by wastewater treatment reach the aquatic environment. The impact of wastewater treatment plants on the receiving rivers was studied showing a clear increase of target molecules concentrations near the wastewater treatment plants outfall. However, only propranolol presented an environmental risk ratio in the range or above 1 showing a possible environmental risk in 4 studied receiving waters out of 15. Never the less, even if no specific toxic effects are pointed out, each molecule contributes to the overall toxic potential of the substances present in the aquatic environment.
248

Surface Water and Groundwater Hydrology of Borrow-Pit Wetlands and Surrounding Areas of the Lewisville Lake Environmental Learning Area, Lewisville, Texas

Dodd-Williams, Lynde L. 08 1900 (has links)
The focus of this study was to characterize the surface water and groundwater hydrology of borrow-pit wetlands located within the borders of the Lewisville Lake Environmental Learning Area (LLELA), east of the Elm Fork of the Trinity River. The wetlands were excavated into alluvial deposits downstream of the Lewisville Lake Dam. Both surface water and groundwater contribute to the hydro-period of the borrow-pit wetlands. Nearby marshes exhibit characteristics of groundwater discharge. Salinity in groundwater-fed wetlands could affect establishment of vegetation, as suggested from plant surveys. Surface water input from storm events dilutes salinity levels. Management of LLELA wetlands should include long-term evaluation of hydrology and plantings to enhance habitat. Plans for additional wetlands should consider both surface water and groundwater inputs.
249

ENABLING LARGE-SCALE HYDROLOGIC AND HYDRAULIC MODELING THROUGH IMPROVED TOPOGRAPHIC REPRESENTATION

Sayan Dey (7444328) 19 December 2021 (has links)
<p>Topography is one of the primary drivers of physical processes in the rivers and floodplains. Advances in remote-sensing and survey techniques have provided high-resolution representation of the floodplains but information regarding the 3D representation of river channels (commonly known as river bathymetry) is sparsely available. Field surveys along an entire river network in a watershed remains infeasible and algorithms for estimating simple but effective characterization of river channel geometry are hindered by an incomplete understanding of the role of river bathymetry in surface and subsurface processes. </p> <p> The first objective of this dissertation develops an automated framework – System for Producing RIver Network Geometry (SPRING) for improving the geospatial descriptors of a river network. The tool takes as input the DEM and erroneous river centerline to produce spatially consistent river centerlines, banks, and an improved representation of river channel geometry. SPRING can process entire river networks and is not limited single reach applications. The proposed framework is flexible in terms of data requirements, resolution of output datasets and user preferences. It has a user-friendly graphic user interface (GUI) and is appropriate for large-scale applications since it requires minimal user input.</p> <p> A better understanding of the role of bathymetric characteristics in surface-subsurface hydrology and hydrodynamics can facilitate an efficient incorporation of river bathymetry in large river networks. The second objective explores the level of bathymetric detail required for accurately simulating surface and subsurface processes by developing four bathymetric representations using SPRING with reducing level of detail. These bathymetric configurations are simulated using a physically based tightly coupled hydrologic and hydrodynamic model to estimate surface and subsurface fluxes in the floodplains. Comparison of fluxes for the four bathymetric configurations show that the impact of river bathymetry extends beyond surface routing to surface water – groundwater interactions. Channel conveyance capacity and thalweg elevation are the most important characteristics controlling these interactions followed by channel side slope and channel asymmetry. </p> <p> The final objective aims to develop benchmarks for bathymetric characteristics for accurately simulating flooding related physical processes. The sensitivity of surface and subsurface fluxes to error in channel conveyance capacity is investigated across reaches with varying geomorphological characteristics. SPRING is used to create six bathymetric configurations with varying range of error in channel conveyance capacity (ranging from 25% to 300%). They are simulated using a tightly coupled physically distributed model for a flood event and the estimates of water surface elevation, infiltration and lateral seepage are compared. Results show that incorporating channel conveyance capacity with an error of within 25% significantly improves the estimates of surface and subsurface fluxes as compared to those not having any bathymetric correction. For certain reaches, such as those with high drainage area (>1000km<sup>2</sup>) or low sinuosity (< 1.25), errors of up to 100% in channel conveyance capacity can still improve H&H modeling.</p>
250

Studie úpravny vody z povrchového zdroje / Study of water treatment plant from surface source

Inwald, Petr January 2021 (has links)
The first part of the thesis deals with water sources and methods of drinkable water treatment. This section describes the technologies used for two-stage water treatment from a surface source. The second part deals with study of the new drinking water treatment plant from a surface source for Adamov town. The work documents the current state of the existing water treatment plant and describes used technology with a design flow Q = 30 l s-1. In the next part of thesis is design of two variations of new technological line with a design flow Q = 10 l s-1. The first variation is one-stage water treatment with pressure filters as the main separation stage. Two-stage water treatment is designed for the second variation, in which the first stage of separation are clarifiers and the second stage are pressure filters. Thesis includes drawing documentation of designed pressure filters and clarifiers, technological and height scheme of both variations.

Page generated in 0.2565 seconds