A cylindrical electrochemical reactor with a 3 in diameter copper or nickel metal foam cathode and a concentric carbon cloth anode was used to destroy aqueous phase carbon tetrachloride (CT). The results show that a high CT conversion can be achieved in regions of the cathode near the anode, but a low CT conversion is obtained in the region around the center of the cathode. This CT conversion distribution in the radial current-conducting direction suggests that a portion of the cathode worked inefficiently even though the overall CT conversion is still adequate. Further research by changing the solution pH and conductivity suggests that the radial conversion distribution is due to radial variations in cathode surface availability. The inherent difficulties that these results imply with regards to reactor scale up suggested a new approach to the design. An annular reactor, consisting of a thin (3.2 mm) nickel foam cathode wrapped around an inert Plexiglas core and separated for an external concentric anode by a semi-permeable membrane was adopted. Under compatible operating conditions, the annular reactor showed a high overall effluent CT conversion. However, experiments at low pH (2.25) yielded higher conversions than under neutral pH conditions. This result suggests that CT conversion is favored by a relatively high proton concentration. This reactor can be simulated by a one dimensional model. The annular reactor was used to destroy PCE and TCE successfully, which suggests that this technique can be employed to treat groundwater contaminated with complex mixtures of chlorinated hydrocarbons.A multi-layer reactor based on the principle of the annular reactor was developed as an option for the scale up of the system. This reactor exhibited high and uniform radial CT conversion.

Grundvattenmodellering av föroreningstransport   – Ett uppdragsanpassat beräkningsverktyg Emil Friberg Målet för detta arbeta var att bygga upp en modell i modelleringsprogrammet MODFLOW för spridning av förorenande ämnen i grundvattnet. Syftet med modellen var att finna en balans mellan den mycket enkla modellen som Naturvårdsverket har satt upp för förorenad mark och en fullskalig platsspecifik modell. Utgångspunkten var att studera litteraturen för att finna lämpliga generella parametrar som beskriver föroreningstransport i grundvattnet. Tre genomförda uppdrag med förorenad mark användes som referenskälla, men även för att evaluera den framtagna modellen. Föroreningarna som förekom i dessa uppdrag och som studerades i detta arbete är bensen, PCE och arsenik. Att finna lämpliga parametrar för beskrivning av transporten visade sig vara ganska enkelt, det finns en god förståelse för vilka faktorer som har betydelse. Däremot var det svårare att finna generella värden till dessa parametrar. Sammanställningar gjorda av Naturvårdsverket var en god källa. Den uppbyggda modellen döptes till ESM. Alla valda parametrar analyserades och modellen känslighetsanalyserades. Resultatet visade att vissa parametrar ger större känslighet än andra. Samtidigt visade analyserna att känsligheten varierar beroende på vilket intervall en viss parameter studeras samt att modellens känslighet även är beroende på värdena på de andra parametrarna. Bland annat visade det sig att dispersion alltid är en känslig parameter inom vissa intervall. Sorption och grundvattenflödets gradient visade sig enbart vara känsliga i vissa fall. ESM jämfördes med analytiska lösningsmetoder, Naturvårdsverkets riktlinjesmodell samt de tre utvalda uppdragen. Resultatet var blandat. I jämförelsen med den enklaste analytiska lösningsmetoden med enbart advektion och dispersion överensstämde inte resultaten . Då även sorption användes blev resultatet mycket bra med en hög överensstämmelse. Det gick inte att jämföra Naturvårdsverkets modell rakt av med ESM då förutsättningarna var ganska skilda. Däremot visade jämförelsen i ett större perspektiv att ESM ger en bättre bild av föroreningsspridningen än vad Naturvårdsverkets riktlinjesmodell ger.  Även jämförelsen mellan ESM och de utvalda uppdragen gav blandat resultat, vissa fall blev resultatet mycket bra medan andra mindre. Generellt gav ESM en bra bild av föroreningssituationen och dess karaktär men den har svårigheter att återspegla verkligheten beträffande uppmätta halter och andra mer specifika parametrar. Slutsatsen blev att ESM kan användas initialt för att få en bild av situationen och att modellen är enkel att förändra men kan inte återspegla alla aspekter på föroreningstransporten. Nyckelord: MODFLOW, MT3DMS, föroreningstransport, PCE, bensen, arsenik, riktvärde för förorenad mark Institutionen för geovetenskaper; luft-, vatten- och landskapslära. Uppsala universitet Villavägen 16, Se-752 36 UPPSALA

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No description available.

Laboratory microcosm experiments were conducted to assess the potential for biostimulation and bioaugmentation as source reduction measures in support of a monitored natural attenuation remedial strategy at Naval Amphibious Base (NAB) Little Creek. Previous work with laboratory microcosms conducted under simulated natural (unamended) conditions has demonstrated that indigenous dehalorespirators were capable of partial dechlorination of tetrachloroethene (PCE) to cis-dichloroethene (cis-DCE). This study attempts to achieve complete reductive dechlorination with amendments to static microcosms to test the hypotheses that nutrient-limited or microorganism-limited conditions exist in aquifer sediments obtained from the site. The enhanced bioremediation experiments were comprised of nutrient-amended microcosms receiving additions of electron donors, mineral medium, or anaerobic digester supernatant, and dechlorinating culture-amended microcosms were inoculated with a culture capable of transforming PCE to ethene. Reductive dechlorination in the nutrient-amended microcosms proceeded to cis-DCE over a 260-day study period, at slightly higher rates than in experiments conducted with aquifer sediments from the same location under natural conditions. Inoculation of aquifer sediments with a small amount of dechlorinating culture initiated rapid transformation of PCE to vinyl chloride (VC) by day 18 of the study. Zero-order rates of PCE dechlorination in unamended, propionate-, formate-, mineral medium-, digester supernatant-, and dechlorinating culture-amended microcosms were 0.24, 0.750, 1.30, 0.339, 0.177, and 1.75 µM/day, respectively. The results of this study suggest that an engineered biostimulation approach alone may not be as beneficial for PCE source reduction at NAB Little Creek, than bioaugmentation with competent dehalorespirators, along with the inclusion of supplemental nutrients which would be available to stimulate dechlorination activity of both indigenous and introduced microorganisms. / Master of Science

Microcosms were constructed from aquifer sediment samples taken from an actively degrading chlorinated solvent contaminated site located in Virginia Beach, Virginia. The objective of this study was to determine if and how the addition of cyclodextrin (CD) affects reductive dechlorination of chlorinated ethenes. After chlorinated solvent degradation rates were established in anaerobic and aerobic microcosms, 100 mg/L of CD solution was added for a period of 21 days. CD was then removed after 26 days to simulate the degradation response of the aquifer in a post CD injection environment. Degradation rates were determined by analyzing PCE, TCE, and cis-DCE concentration data over the various phases of the experiment. Results from this study indicated that chlorinated solvent degradation could be either impaired or facilitated by the addition of CD. CD appeared to stimulate one anaerobic microcosm (IY-2c) where daughter production had not previously occurred. The activity of this microcosm was greatly enhanced by the addition of CD (0 uM/day to 13.89 uM/day). However, biotransformation of PCE in another anaerobic microcosm in which reductive dechlorination was occurring, ceased after the addition of CD (IY-1a). In a third group of microcosms the rate and extent of reductive dechlorination was greatly enhanced by the addition of CD. The effect of adding CD was also found to be highly dependent on the redox conditions in the microcosm, specifically if the conditions were strongly reducing. The most active microcosms, found in the Aerobic Group, also had the lowest ferrous iron concentrations (3.57 mg/L for BY-1a, 2.25 mg/L for BY-1b, and 0.41 mg/L for BY-1c). The microcosm (IY-2b) that showed no daughter production had the highest level of ferrous iron (44.22 mg/L). This study presents a qualitative approach to the affect of CD on MNA. / Master of Science

This work focused on using a microbubble dispersion to deliver hydrogen and carbon dioxide to anaerobic consortia to stimulate their ability to reductively dehalogenate tetrachloroethylene all the way to ethene and ethane. A continuous flow system, consisting of six anaerobic soil column bioreactors, inoculated with sediments from Virginia Tech's Duck Pond, was used for this study. Two columns received microbubbles containing hydrogen and carbon dioxide, two received sodium propionate, and two were not fed a substrate. A 30 micromolar PCE solution was delivered to the consortia at 3 ml/min. Microbubbles containing a mixture of 90% hydrogen and 10% carbon dioxide were effectively produced in a closed spinning disk generator, and were acceptable for delivering the gases to the columns. After the biodegradation study was completed, the microbubbles were found to have a pH of 4.4, due to the carbon dioxide. Microbubbles amended with NaOH to 0.01 molar yielded pH neutral microbubbles with improved stability. Methane was measured in all six columns throughout the experiment, verifying that methanogens were present. Methane levels were highest in the propionate columns, showing the the methanogens there were more active. Methane levels in the microbubble columns were similar to those in the control columns. Propionate and acetate were not detected in the columns where propionate was fed, showing that proton reducers and acetoclastic methanogens were both active. Recovery of PCE and the degradation products was almost 90% in the microbubble and control columns where most of the PCE was recovered in the effluent. The predominant product in both systems was TCE, although some ethene was detected in all four columns. The control consortia produced TCE averaging about five micromolar while the microbubble columns averaged about two micromolar TCE. One of the components of the microbubbles probably caused the lowered amounts of PCE reduction. That some ethene was seen in the microbubble columns suggests different conditions can be found to stimulate the further reduction of PCE with hydrogen and carbon dioxide microbubbles. The product recovery in the propionate columns was about 64%. Over half of the injected PCE was dechlorinated to ethene and ethane. / Ph. D.

La majorité des grands opérateurs utilise la technologie MPLS pour gérer leur réseau via des protocoles de signalisation et de distributions de labels. Or, ces protocoles sont complexes à déployer, à maintenir et la résolution des pannes est souvent très difficile. L'IETF a initié la standardisation d'une architecture de routage par segments (Segment Routing) s'appuyant sur un plan de contrôle simple, léger, facile à gérer et instanciée sur MPLS ou IPv6. Cette architecture repose sur le concept de routage à la source, dans lequel l'en-tête des paquets transporte les indications du chemin à suivre pour atteindre sa destination. Adapté aux cas d'usages simples et offrant nativement une résistance aux pannes, les cas d'usages plus complexes exigent de résoudre des verrous technologiques pour lesquels nous proposons plusieurs solutions. Dans cette thèse effectuée au sein d'Orange Labs, nous nous sommes intéressés à l'instanciation de l'architecture Segment Routing sur le plan de transfert MPLS et plus particulièrement à l'ingénierie de trafic, notamment avec réservation de ressources. Nous avons proposé des solutions aux problèmes liés à la limitation matérielle des routeurs actuels ne permettant pas l'expression de tous les chemins contraints. Ce travail est divisé en deux parties : (i) la proposition d'algorithmes de calcul et d'encodage de chemins de routage par segment afin de contourner les limitations matérielles. (ii) la définition des exigences architecturales et la construction d'une preuve de concept fonctionnelle. Enfin, cette thèse propose de nouvelles pistes d'études afin de consolider les outils d'ingénierie de trafic pour le routage par segment. / Most major operators use MPLS technology to manage their network via signalling and label distribution protocols. However, these protocols are complex to deploy, maintain and troubleshooting is often very difficult. The IETF has initiated the standardization of a segment routing architecture based on a simple control plane, lightweight, easyto-manage and instantiated on MPLS or IPv6. This architecture is based on the concept of source routing, in which the packet header carries the indications of the path to follow to reach its destination. Suitable for simple use cases and natively resistant to failure, more complex use cases require the resolution of technological issues for which we offer several solutions.In this thesis carried out within Orange Labs, we were interested in the instantiation of the Segment Routing architecture on the MPLS transfer plan and more particularly in traffic engineering, particularly with resource reservation. We have proposed solutions to the problems related to the hardware limitation of current routers that do not allow the expression of all constrained paths. This work is divided into two parts : (i) the proposal of algorithms for computing and encoding segment routing paths in order to bypass hardware limitations. (ii) the definition of architectural requirements and the construction of a functional proof of concept. Finally, this thesis proposes new research issues to consolidate traffic engineering tools for segment routing.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Schistosomiasis is a major waterborne diseases and environmental degradation , poverty and underdevelopment are key factors for its occurrence . This study aims to perform the mapping of favorable environmental conditions for the development of schistosomiasis involving 23 municipalities that are part of the southern state of Sergipe in the period 2001-2010. Areas were chosen for detaining a history of endemicity of schistosomiasis being used as crowds on weekends. The study was guided by the results of the Schistosomiasis Control Program and visits to the municipalities bordering the river basins Vasa Barris , Real Piauí River and river. To assess the possible relationship between the characteristics of the pattern of occupation of land space and its ability to induce the occurrence of schistosomiasis was prepared a list of inducers (risk factors) that express conditions related to the presence and maintenance of breeding or outbreaks of this disease. For the mapping of favorable conditions a GIS was used, where information Municipal Human Development Index, suitability, sanitation, rainfall, environmental degradation, accessibility localities and inducers of schistosomiasis were spatially suggesting areas of injury to the health of populations with nearby bodies of water. From the acquisition of graphics and descriptive spatial data base map was constructed , georreferenciando the spatial position of the cases the number of snails collected , the road network , the inductors as well as the rate of infection for S. mansoni in the study areas . The program used for connecting the storage of descriptive attributes and spatial data to graphical features allowing visualization of spatial analysis was QGIS , where results were presented through tables and thematic maps . We used the intensity Kernel method, which promoted a statistical smoothing filter allowing the variability of a data set while retaining the essential characteristics of sites. The results fed into the base of the ´Datasus´ in the period 2001-2010 were 49,483 cases of schistosomiasis , referring to municipalities. Thematic maps produced feature regions spatial position of greater intensity of positive cases and number of snails collected . With spatial analysis was allowed to observe the at risk areas, associating the road network and inductors. The results of this study may help preventative measures public intervention, facilitating monitoring of the regions under study. / A esquistossomose é uma das principais doenças de veiculação hídrica e a degradação ambiental, a pobreza e o subdesenvolvimento são fatores determinantes para sua ocorrência. Este trabalho teve como objetivo realizar o mapeamento das condições ambientais favoráveis ao desenvolvimento da esquistossomose envolvendo os 23 municípios que fazem parte da região sul do estado de Sergipe no período de 2001 a 2010. As áreas foram escolhidas por deterem de um histórico de endemicidade de esquistossomose, sendo utilizadas como balneários nos finais de semana. O estudo foi pautado nos resultados do Programa de Controle da Esquistossomose e visita aos municípios banhados pelas bacias hidrográficas do rio Vaza Barris, rio Real e rio Piauí. Para avaliar as possíveis relações entre as características do padrão de ocupação de espaço territorial e sua capacidade de indução à ocorrência da esquistossomose mansônica foi elaborado uma lista de indutores (fatores de risco) que expressam condições relacionadas à presença e manutenção de criadouros ou focos dessa doença. Para o mapeamento das condições favoráveis foi utilizado um SIG, onde, informações do Índice de Desenvolvimento Humano Municipal, adequabilidade ao saneamento básico, pluviometria, degradação ambiental, acessibilidade as localidades e os indutores de esquistossomose foram espacializados sugerindo áreas de agravo à saúde de populações com proximidades das coleções hídricas. A partir da aquisição dos dados espaciais gráficos e descritivos foi construída a base cartográfica, georreferenciando a posição espacial dos casos ao número de caramujos coletados, a malha viária, os indutores, bem como à taxa de infecção para S. mansoni nas áreas de estudo. O programa utilizado para ligação dos atributos e armazenamento dos dados espaciais descritivos às feições gráficas permitindo a visualização da análise espacial foi o QGIS, onde os resultados foram apresentados através de mapas temáticos e tabelas. Utilizou-se o método de Kernel de intensidade, que promoveu uma suavização estatística, o que permitiu filtrar a variabilidade de um conjunto de dados, retendo as características essenciais dos locais. Os resultados alimentados na base do datasus no período de 2001 a 2010 foram 49.483 casos de esquistossomose, referente aos municípios estudados. Os mapas temáticos produzidos apresentam regiões, posição espacial de maior intensidade dos casos positivos e número de caramujos coletados. Com a análise espacial foi permitido observar as áreas expostas ao risco, associando a malha viária e aos indutores. Os resultados desta pesquisa pode auxiliar medidas de intervenção pública preventivas, facilitando o monitoramento das regiões em estudo.

<p>Chlorinated solvent are volatile organic substances that can be harmful for humans and for the environment. Examples of common chlorinated solvents are perchloroethene, PCE, and trichloroethene, TCE. Chlorinated solvents appear as contaminants in soils primarily where they have been used as washing fluids in dry-cleaning facilities or as degreasers in metal industries. Chlorinated solvents are DNAPLs (dense non-aqueous phase liquids), which means that they are not easily dissolved in water and that they sink to the bottom of the aquifer. Adsorption to soils is low so chlorinated solvents are mobile in soils. Chlorinated solvents can be harmful at low concentrations. Complete degradation can only occur under specific conditions. Because of the properties of these substances, investigation and analysis methodology are extra important for determining transport and risks in a contaminated area.</p><p>In this work, investigation and analysis methods for chlorinated solvents are described. Planning, fieldwork, modeling and risk analysis are described.</p><p>Projects concerning chlorinated solvents completed by Golder Associates AB have been compiled and analysed. Based on the compilation, conclusions have been drawn and statistics have been calculated. Investigations of the relation between concentrations in different media have been made as well as investigations of the relation between degradation products at different distances from the source and at different times after release. The data from the environmental investigations have been compared with theoretical literature values and modelling results.</p><p>The results show that there is a large natural variation in the data and that the differences between different areas are quite large. The results confirm the theory that the percentage of degradation products increases with distance from the source and with time from release. In addition, solvents with a higher degree of chlorination seams to appear to a greater extent in the soil and the more volatile substances seams to appear to a greater extent in the soil air.</p> / <p>Klorerade lösningsmedel är flyktiga klorerade organiska ämnen som kan vara skadliga för människor och miljön. Exempel på vanliga klorerade lösningsmedel är perkloreten, PCE och trikloreten, TCE. Klorerade lösningsmedel förekommer som markföroreningar främst efter användning som tvättvätska i kemtvättar och som avfettningsmedel i metallindustrin. Klorerade lösningsmedel är DNAPLs (dense non-aqueous phase liquids), det innebär att de är svårlösliga i vatten och att de sjunker och lägger sig på botten av akviferen. Fastläggningen i jorden är liten hos klorerade lösningsmedel som därmed är rörliga i marken. De är farliga redan vid små koncentrationer och fullständig nedbrytning sker endast under vissa förutsättningar. Ämnenas egenskaper gör att undersöknings- och analysmetodiken är viktig för att riktigt kunna bestämma deras utbredning och risk på ett förorenat område.</p><p>I detta arbete beskrivs undersöknings- och analysmetodiken för områden förorenade med klorerade lösningsmedel. Upplägg, fältarbete, modellering och riskbedömning beskrivs.</p><p>Projekt som handlar om klorerade lösningsmedel utförda av Golder Associates AB har sammanställts. Sammanställningen har analyserats och utifrån den har olika slutsatser dragits och statistik beräknats. Bland annat har samband mellan halter i olika medier samt samband mellan halter av nedbrytningsprodukter på olika avstånd från källan respektive efter olika lång tid från läckage har undersökts. Data från miljöundersökningarna har även jämförts med teoretiska litteraturvärden samt modelleringsresultat.</p><p>Resultatet visar att den naturliga spridningen av data är stor samt att resultaten skiljer sig åt mellan olika områden. Resultaten bekräftar teorierna att halten nedbrytningsprodukter ökar med avståndet från källan och med tiden samt att ämnen med högre kloreringsgrad finns i större utsträckning i jorden och att flyktigare ämnen finns i större utsträckning i porluften.</p>