Norrvatten is a municipal association which owns a water treatment plant capable of supplying good quality drinking water to the consumers in the associated neighbouring municipalities. After preliminary investigations for the future year of 2050, there were estimates which suggest a potential water quality degradation in the lake which supplies the raw water for treatment due to uncertain future climatic conditions and other forms of pollutions from the surrounding. There is also a forecast of future population increase in the respective neighbouring municipalities of Stockholm county, which consequently increases the demand for additional quantity of supplied drinking water. The supplied drinking water, which even though is currently acceptable by the standards set by Swedish Food Agency, still requires additional advanced treatment techniques in order to provide an upscale to its quality. This increase in water quality can be achieved by increasing the natural organic matter removal treatment techniques in the water treatment plant by implementing more chemical and microbiological barriers. Norrvatten has proposed several alternative water purification methods, out of which one of them can be implemented in the water treatment plant, after an expansion in the capacity of the plant to achieve all the above-mentioned requirements.  A case study has been performed at Norrvatten in Stockholm, Sweden for evaluating the environmental performance of the proposed treatment alternatives. This study adopts a cradle-to-gate life cycle assessment methodology to analyze the alternatives using stand-alone and comparative assessment methods. An explicit focus is given with the selection of 15 different environmental categories to assess the related environmental burdens. The various hotspots identified from the analysis is investigated and identified to find the associated trade-offs with the alternatives under study. Additional parameter changes have been made in the alternatives to apprehend how the impacts change accordingly.  The various hotspots identified from the results of the study were, the utilization of granular activated carbons for filtration, the consumption of aluminium sulphate for coagulation, the consumption of soda if iron chloride is selected as the main coagulant, the consumption of electricity in the WTP by nanofiltration process, hydropower from pumped storage and the use of heavy trucks for transporting chemicals from suppliers to the site. Other aspects and assumptions from conducting a sensitivity analysis indicated that there are possibilities to decrease the impacts through the following changes. By switching the main coagulant from aluminium sulphate to iron chloride to decrease the major resource depletion and human health impacts with a trade-off increase in impacts from an increased production of soda for chemical consumption. By switching the current purchase of electricity, from a green energy mix to the Swedish grid mix, to greatly improve the environmental performance of the treatment plant. This energy change was observed to result in the reduction of global warming potential from CO2 emissions. Other changes which can be implemented to reduce the overall environmental impacts are switching from fuel- based transportation trucks to electric trucks and switching chemical suppliers from outside Sweden to suppliers located near or within Sweden, closer to the water treatment plant. / Norrvatten är en kommunförening som äger en vattenreningsanläggning som kan leverera dricksvatten av god kvalitet till konsumenterna i de angränsande grannkommunerna. Efter preliminära undersökningar för det kommande året 2050 fanns det uppskattningar som tyder på en potentiell nedbrytning av vattenkvaliteten i sjön som ger råvattnet för behandling på grund av osäkra framtida klimatförhållanden och andra former av föroreningar från omgivningen. Det finns också en prognos om framtida befolkningsökning i respektive grannkommuner i Stockholms län, vilket följaktligen ökar efterfrågan på ytterligare mängd levererat dricksvatten. För närvarande levererat Dricksvatten, som trots att det är acceptabelt enligt de standarder som fastställts av Livsmedelsverket, kräver ytterligare avancerade behandlingstekniker för att ge en förbättring av dess kvalitet. Denna ökning av vattenkvaliteten kan uppnås genom att öka de tekniska behandlingsteknikerna för avlägsnande av organiskt material i vattenreningsverket genom att implementera fler kemiska och mikrobiologiska barriärer. Norrvatten har föreslagit flera alternativa vattenreningsmetoder, varav en av dem kan implementeras i vattenreningsverket, efter en utvidgning av anläggningens kapacitet att uppnå alla ovannämnda krav.  En fallstudie har utförts vid Norrvatten i Stockholm för att utvärdera miljöprestanda för de föreslagna behandlingsalternativen. Denna studie använder livscykelanalys för att analysera alternativen. Ett uttryckligt fokus ges med valet av 15 olika miljökategorier för att bedöma relaterade miljöbördor. De olika hotspots som identifierats från analysen undersöks och identifieras för att hitta tillhörande avvägningar med alternativen som studeras. Ytterligare parameterändringar har gjorts i alternativen för att förstå hur effekterna förändras i enlighet därmed.  De olika hotspots som identifierats från resultaten av studien var användningen av grandulerat aktivt kol för filtrering, konsumtionen av aluminiumsulfat för koagulering, konsumtionen av läsk om järnklorid väljs som huvudkoaguleringsmedel, förbrukningen av el i vattenreningsverket genom nanofiltreringsprocessen , vattenkraft från pumplagring och användning av tunga lastbilar för transport av kemikalier från leverantörer till anläggningen. Andra aspekter och antaganden från att genomföra en känslighetsanalys visade att det finns möjligheter att minska effekterna genom följande förändringar. Genom att byta huvudkoaguleringsmedlet från aluminiumsulfat till järnklorid för att minska den största resursutarmningen och människors hälsoeffekter med en avvägning av effekterna från en ökad produktion av natriumkarbonat. Genom att byta det aktuella inköpet av el, från en grön energimix till den svenska nätmixen, för att kraftigt förbättra reningsverkets miljöprestanda. Denna energiförändring observerades leda till en minskning av den globala uppvärmningspotentialen från koldioxidutsläpp. Andra förändringar som kan genomföras för att minska den totala miljöpåverkan är att byta från bränslebaserade transportbilar till elektriska lastbilar och byta kemikalieleverantörer från utanför Sverige till leverantörer nära eller inom Sverige, närmare vattenreningen växt.

In this work, fluorous metal organic framework 1 (FMOF-1) and its isomorphic structures are investigated for both sensing and filtration applications. In chapter 2 both FMOF-1 and its acetone derivative, aFMOF-1, are shown to exhibit an unusual photoluminescent behavior by having a "turn-on" emission when exposed to vacuum. This baroluminescence occurs at different rates depending on specific gas, allowing FMOF-1 and aFMOF-1 to not only act as vacuum gauges, but also potentially act as sensors for gas identification. Chapter 3 focuses on chemical sensing properties (chemosensing) of the newly discovered second methanol derivative of FMOF-1, mFMOF-2. mFMOF-2 has been shown to be air and water stable, however exposure to volatile organic compounds (VOCs) will cause quenching or shifts in emission. Finally, chapter 4 investigates the ability of combining MOFs with more traditional sorbents to investigate the possibility of a hybrid material that takes advantage of both materials. MOFs have long been investigated for their filtration properties, however the high cost of synthesis of MOFs compared to the cost-efficient common filters hamstrings their real-world implementations. Combining a small percentage of FMOF-1 with activated carbon is seen to improve the filtration efficiency and to increase the hydrophobic properties. This hybrid filtration material avoids the problems associated with the cost of synthetic filtration materials since only 0.1% mass additive is shown to yield significantly improved results.

Le biogaz doit être purifié pour devenir un combustible renouvelable. De nombreux traitements actuels ne sont pas satisfaisants car, pour des raisons de coûts les procédés de séparation privilégiés aboutissent souvent au rejet direct ou indirect du sulfure d'hydrogène (H2S) à l’atmosphère, c’est le cas de la séparation à l’eau sous pression. Les objectifs de la thèse portent d’abord sur l’étude et la modélisation des méthodes connues de séparation de l'hydrogène sulfuré du méthane. Les concentrations typiques varient de 200 à 5000 ppm, et la séparation devra réduire la teneur résiduelle en H2S à moins de 1 ppm. Parallèlement seront étudiées les méthodes de traitement de H2S. Une fois la (ou les) méthode(s) de séparation sélectionnée(s), des essais de validation seront effectués sur un système traitant de l’ordre de 85 Nm3/h de méthane où seront injectées des quantités de H2S variant entre 1 et 100 ppm.Cette thèse requiert des modélisations réalistes sous Aspen Plus® ou sous un code équivalent pour établir a priori des efficacités de séparation selon différentes conditions opératoires et en prenant en compte le paramètre température. L’énergie dépensée pour la séparation effective sera un des critères fort de la comparaison, de même que l’économie de matière.Une approche système est indispensable pour étudier la rétroaction de la méthode de valorisation du H2S sur la ou les méthodes séparatives. A priori c’est aussi l’outil Aspen Plus® ou équivalent qui permettra cette approche système.L’étude du procédé sera menée selon la double approche modélisation et expérimentation, pour l’étude expérimentale des méthodes séparatives, l’échelle du banc sera semi-industrielle et le banc permettra d’étudier les méthodes de séparation jusqu’à -90°C. / Biogas must be purified for becoming a renewable fuel. At now, the most part of the purification techniques are not satisfactory because they imply hydrogen sulfides (H2S) rejection to the atmosphere. One example of these methods is the treatment with high pressure water. The first objective of the thesis is modeling the conventional methods for separating H2S from methane. Typical concentrations of H2S in methane vary from 200 to 5000 pm. Separation methods must decrease the concentration of H2S in methane to less than 1 ppm. At the same time, methods for H2S treatment will be studied.Once the most appropriated separation methods will be selected, some test will be carried out on a pilot plant capable of treating 85 Nm3/h of methane, where quantities of H2S ranging from 1 and 100 ppm will be injected. These tests will allow validating the modeling of the separation process. On the basis of the obtained results, a specific test bench will be conceived and constructed for validating the selected process.The thesis work requires simulating the separation process using the software Aspen Plus® or an equivalent one. The effectiveness of different operative conditions will be tested, varying also the parameter temperature. The energy necessary for the separation will be one of the most important criteria for the comparison, as well as the mass consumption of the different fluids involved in the process.A system approach is fundamental for evaluating the backward effect of the H2S valorization method on the separation techniques. The process simulator (Aspen Plus® or equivalent) will allow the system approach.The study will involve modeling and experimental parts. The experimental part will be carried out taking advantage of a semi-industrial size test bench, allowing studying the separation methods down to -90°C.

El objetivo de esta tesis ha sido el tratamiento de un residuo (lodo de fundición) procedente del lavado húmedo de los gases del horno fusor. Para ello, se ha evaluado la peligrosidad del residuo y, posteriormente, se han estudiado diferentes tratamientos previos al vertido y se ha realizado su evaluación ambiental. El lodo de fundición es un residuo ecotóxico, debido principalmente a la alta concentración de cinc y a la carga orgánica (fenoles) del mismo, pudiéndose establecer relaciones matemáticas entre la ecotoxicidad y la concentración de cinc y fenoles, tanto en el residuo original como en los productos finales. Entre las diferentes tecnologías de tratamiento, destacan los procesos de estabilización/solidificación con cal o cemento como agente aglomerante, por su elevado interés en residuos de carácter tóxico mixto: orgánico e inorgánico. Se ha llevado a cabo un estudio exhaustivo de los diferentes aditivos utilizados en dichos procesos y se han desarrollado diferentes formulaciones cal o cemento y aditivos/residuo con el fin de cumplir los parámetros ambientales, concluyéndose con la relación existente entre formulación y evaluación ambiental y obteniendo una patente de invención. / The aim of this work has been the study of the treatment of foundry sludge coming from after wet cleaning of gases of the furnace in foundry activities. Previously, the hazardous of the waste material has been evaluated. Later, different treatments have been studied and the environmental evaluation have been conducted. Foundry sludge is an ecotoxical waste due to inorganic (basically zinc) and organic (phenols) pollutants, being able to establish mathematical relationships between the ecotoxicity and the concentration of zinc and phenols, both in waste and end-products. Among the different technologies for the treatment, stabilisation/solidification processes with lime or cement as binders are very interesting technologies for waste of mixed character (organic and inorganic). An exhaustive study of different additives used in these processes has been carried out and different formulations have been developed in order to inertise the waste materials, concluding with the relationships between formulation and environmental evaluation and obtaining a patent.

The provision of clean drinking water typically involves treatment processes to remove contaminants. The conventional process involves coagulation with hydrolysing metal salts, typically of aluminium (‘alum’) or trivalent iron (‘ferric’). Along with the product water this also produces a waste by-product, or sludge. The fact of increasing sludge production — due to higher levels of treatment and greater volume of water supply — conflicts with modern demands for environmental best practice, leading to higher financial costs. A further issue is the significant quantity of water that is held up in the sludge, and wasted. / One means of dealing with these problems is to dewater the sludge further. This reduces the volume of waste to be disposed of. The consistency is also improved (e.g. for the purpose of landfilling). And a significant amount of water can be recovered. The efficiency, and efficacy, of this process depends on the dewaterability of the sludge.In fact, good dewaterability is vital to the operation of conventional drinking water treatment plants (WTP’s). The usual process of separating the particulates, formed from a blend of contaminants and coagulated precipitate, relies on ‘clarification’ and ‘thickening’, which are essentially settling operations of solid–liquid separation.WTP operators — and researchers — do attempt to measure sludge dewaterability, but usually rely on empirical characterisation techniques that do not tell the full story and can even mislead. Understanding of the physical and chemical nature of the sludge is also surprisingly rudimentary, considering the long history of these processes. / The present work begins by reviewing the current state of knowledge on raw water and sludge composition, with special focus on solid aluminium and iron phases and on fractal aggregate structure. Next the theory of dewatering is examined, with the adopted phenomenological theory contrasted with empirical techniques and other theories.The foundation for subsequent analyses is laid by experimental work which establishes the solid phase density of WTP sludges. Additionally, alum sludges are found to contain pseudoböhmite, while 2-line ferrihydrite and goethite are identified in ferric sludges. / A key hypothesis is that dewaterability is partly determined by the treatment conditions. To investigate this, numerous WTP sludges were studied that had been generated under diverse conditions: some plant samples were obtained, and the remainder were generated in the laboratory (results were consistent). Dewaterability was characterised for each sludge in concentration ranges relevant to settling, centrifugation and filtration using models developed by LANDMAN and WHITE inter alia; it is expressed in terms of both equilibrium and kinetic parameters, py(φ) and R(φ) respectively.This work confirmed that dewaterability is significantly influenced by treatment conditions.The strongest correlations were observed when varying coagulation pH and coagulant dose. At high doses precipitated coagulant controls the sludge behaviour, and dewaterability is poor. Dewaterability deteriorates as pH is increased for high-dose alum sludges; other sludges are less sensitive to pH. These findings can be linked to the faster coagulation dynamics prevailing at high coagulant and alkali dose.Alum and ferric sludges in general had comparable dewaterabilities, and the characteristics of a magnesium sludge were similar too.Small effects on dewaterability were observed in response to variations in raw water organic content and shearing. Polymer flocculation and conditioning appeared mainly to affect dewaterability at low sludge concentrations. Ageing did not produce clear changes in dewaterability.Dense, compact particles are known to dewater better than ‘fluffy’ aggregates or flocs usually encountered in drinking water treatment. This explains the superior dewaterability of a sludge containing powdered activated carbon (PAC). Even greater improvements were observed following a cycle of sludge freezing and thawing for a wide range of WTP sludges. / Further aspects considered in the present work include deviations from simplifying assumptions that are usually made. Specifically: investigation of long-time dewatering behaviour, wall effects, non-isotropic stresses, and reversibility of dewatering (or ‘elasticity’).Several other results and conclusions, of both theoretical and experimental nature, are presented on topics of subsidiary or peripheral interest that are nonetheless important for establishing a reliable basis for research in this area. / This work has proposed links between industrial drinking water coagulation conditions, sludge dewaterability from settling to filtration, and the microstructure of the aggregates making up that sludge. This information can be used when considering the operation or design of a WTP in order to optimise sludge dewaterability, within the constraints of producing drinking water of acceptable quality.

No description available.

Com o crescimento das atividades industriais e da população, aumentam também a quantidade de resíduos gerados que ocasiona problemas ambientais. No Brasil, produtor de bens na agroindústria, os problemas causados pelo acúmulo e destinação inadequada dos resíduos sólidos é de grande porte. A partir dessa problemática são criados mecanismos que incentivam a reutilização e reciclagem dos resíduos. É buscando desenvolver tecnologia inédita de matérias-primas alternativas que se produziu carvão ativado a partir de resíduos de coco, acerola e caju. Primeiramente coletou-se a fibra-de-coco seco e bagaços/cascas de acerola e do caju para posterior preparação desse material através da impregnação com ZnCl2, da ativação química e da realização de um teste de avaliação da eficiência do carvão. Foi produzido carvão ativado com todas as amostras, onde a aplicação na amostra de água coletada no rio Capibaribe (perto do túnel Chico Science), Recife, Pernambuco, apresentou redução da turbidez em 97,3 % usando o tratamento com 25 % de fibra-de-coco + 75 % de caju. / With the growth of industrial activities and population, also increases the amount of generated waste which causes environmental problems. In Brazil, a major producer of goods in the agricultural industry, the problems caused by the accumulation and improper disposal of solid waste are large. From this problematic, mechanisms that encourage the reuse and recycling of waste are created. It is seeking to develop new technology of alternative raw materials that are produced activated carbon from coconut waste, barbados cherry and cashew. Primarily, the collection of fiber-to-dry coconut and cake/shells from barbados cherry and cashew for later preparation of this material by impregnation with ZnCl2, chemical activation and conducting an evaluation test coal efficiency. The result, within all samples, was an activated carbon where the application in the water sample collected from the Capibaribe River (near Chico Science tunnel), Recife, presented a decrease in turbidity in 97.3% using treatment with 25% fiber- coconut + 75% cashew.

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2018-07-13T19:29:17Z No. of bitstreams: 2 Dissertação - Maria Carolina de Almeida - 2017.pdf: 6786764 bytes, checksum: 4574a29178a9cb373e63d3280e95024e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-07-17T13:38:02Z (GMT) No. of bitstreams: 2 Dissertação - Maria Carolina de Almeida - 2017.pdf: 6786764 bytes, checksum: 4574a29178a9cb373e63d3280e95024e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-07-17T13:38:02Z (GMT). No. of bitstreams: 2 Dissertação - Maria Carolina de Almeida - 2017.pdf: 6786764 bytes, checksum: 4574a29178a9cb373e63d3280e95024e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-05-05 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / The objective of this work was to compare the efficiency of conventional treatments such as activated carbon (AC) Adsorption and the advanced oxidation process (AOP), UV-C/H2O2, for degradation of diethyl phthalete (DEP) and coupling UV-C/H2O2/AC in laboratory effluent, ultrapure water and faucet water doped with DEP and laboratory effluent with multicomponents (DEP and phenol). The chemical characterization (Boehm method, pHPZC, IRTF, elemental analysis) and physical (volume of micropores and mesopores, mean micropore width by the Dubini-Radushkevich method were used as a predecessor to the kinetic adsorption study, Surface area and microporous specific volume by the alpha method, microporous and total surface, BET surface area by BET method, cumulative mesopore distribution and pore volume, cumulative area and surface area and pore size by BJH method) of AC. The factorial design with eleven tests and three independent variables (AC mass, temperature and pH) was applied, resulting in response surfaces for adsorption capacity, DEP elimination rate and equilibrium time without significant difference between the studied variables. Mathematical modeling of adsorption kinetics using the pseudo-first, pseudo-second order and intraparticle models was performed and the pseudo-second order model was fitted to the experimental kinetic adsorption data. It was followed by the study of the adsorption isotherms for the lower, intermediate and longer equilibrium experimental conditions. It was performed the mathematical modeling of the adsorption isotherms using the Langmuir and Freundlinch models, and adjusted to the Freundlinch model to the experimental data of the adsorption isotherms with higher determination coefficients (R2), confirming the predominant chemorandomization adsorption phenomenon. The treatment of AOP UV-C/H2O2 was then applied alone. The factorial design with eleven tests and three independent variables (H2O2 concentration, temperature and pH) was applied, resulting in surfaces of responses to DEP elimination rate with significant difference between the variables studied for pH, positive effect of H2O2 concentration (p < 0.5). The mathematical modeling of the kinetics of AOP using the first order models was carried out, and the kinetic experimental data of the photodegradation with high coefficients of determination (R2> 0.9) were fitted to the model. The degradation kinetics of DEP by AOP coupling and AC, UV-C/H2O2/AC were followed. The factorial design with eleven tests and three independent variables (H2O2 concentration, temperature and pH) and with 0.4 g of AC, resulting in surfaces of responses to elimination rate of DEP with significant difference between the variables studied for pH, positive effect of H2O2 concentration (p <0.5). The mass of AC was determined in 0.4 g for all eleven tests, because it was the mass applied at the highest rates of elimination of DEP by kinetics of Adsorption, which was confirmed by repeatability at the central points of the factorial design (C9, C10 and C11). The catalytic activity of the carbons for the Adsorption process in the presence of tertbutanol was high, however, after the determination of the kinetic parameters, the contribution was higher for photooxidation of DEP by the action of the AOP (homogeneous system). / O objetivo desse trabalho foi comparar a eficiência de tratamentos convencionais como a adsorção com carvão ativado (CA) e o processo oxidativo avançado (POA), UV-C/H2O2, para degradação de dietil ftlato (DEP) e a acoplagem UV-C/H2O2/CA em efluente de laboratório, água ultrapura e água de torneira dopados com DEP e efluente de laboratório com multicomponentes (DEP e fenol). De modo predecessor ao estudo cinético da adsorção, aplicado isoladamente, realizou-se a caracterização química (método de Boehm, pHPZC, IRTF, análise elementar) e física (volume de microporos e mesoporos, largura média de microporos pelo método de Dubini-Radushkevich, superfície exterior e volume específico microporoso pelo método alfa, superfície microporosa e total, área de superfície de BET pelo método de BET, distribuição dos mesoporos cumulativo e volume do poro, área cumulativa e área superficial e tamanho do poro pelo método BJH) do CA. O delineamento fatorial com onze ensaios e três variáveis independentes (massa de CA, temperatura e pH) foi aplicado, resultando em superfícies de respostas para capacidade de adsorção, taxa de eliminação de DEP e tempo de equilibrio sem diferença significativa entre as variáveis estudadas. Foi realizada a modelagem matemática das cinéticas de adsorção utilizando os modelos de pseudo-primeira, pseudosegunda ordem e intrapartícula, e ajustou-se ao modelo de pseudo-segunda ordem aos dados experimentais cinéticos de adsorção. Seguiu-se com o estudo das isotermas de adsorção paras as condições experimentais de menor, intermediário e de maior tempo de equilíbrio. Foi realizada a modelagem matemática das isotermas de adsorção utilizando os modelos de Langmuir e Freundlinch, e ajustou-se ao modelo de Freundlinch aos dados experimentais das isotermas de adsorção com maior coeficientes de determinação (R2), confirmando o fenômeno de adsorção predominante quimiosorção. Seguiu-se a aplicação do tratamento de POA UVC/ H2O2, isoladamente. O delineamento fatorial com onze ensaios e três variáveis independentes (concentração de H2O2, temperatura e pH) foi aplicado, resultando em superfícies de respostas para taxa de eliminação de DEP com diferença significativa entre as variáveis estudadas para o pH, e efeito positivo da concentração de H2O2 (p<0,5). Foi realizada a modelagem matemática das cinéticas de POA utilizando os modelos de primeira ordem, e ajustaram-se ao modelo os dados experimentais cinéticos da fotodegradação com elevados coeficientes de determinação (R2>0,9). Seguiu-se para o estudo das cinética de degradação de DEP pela acoplagem POA e CA, UV-C/H2O2/CA. O delineamento fatorial com onze ensaios e três variáveis independentes (concentração de H2O2, temperatura e pH) e com 0,4 g de CA, resultando em superfícies de respostas para taxa de eliminação de DEP com diferença significativa entre as variáveis estudadas para o pH, efeito positivo da concentração de H2O2 (p<0,5). A massa de CA foi determinada em 0,4 g para todos os onze ensaios, porque foi a massa aplicada nas maiores taxas de eliminação de DEP pelas cinéticas de adsorção, que se confirmou, pela repetitibilidade, nos pontos centrais do delineamento fatorial (C9, C10 e C11). A atividade catalítica dos carvões para o processo de adsorção em presença de tércio butanol foi elevada, contudo a contribuição, após a determinação das constantes cinéticas, revelou-se maior para foto-oxidaçao de DEP pela ação do POA (sistema homogêneo).

A regional survey of environmentally harmful substances in fish in autumn 2013 revealed elevated levels of polychlorinated biphenyls (PCBs) in perch from Lake Oxundasjön, north of Upplands Väsby in Stockholm County. Follow-up studies have shown that the quantity of PCBs contained in the lake is unique of its kind in Sweden, and that the area of influence also includes downstream Rosersbergsviken, a bay of Lake Mälaren. The elevated concentrations in fish exceed today's market limits and environmental quality standards for PCBs, as of this, responsible authorities discourage from consumption of fish from Lake Oxundasjön and Rosersbergsviken. The aim has been to use statistical analyses and mass-balance modelling to study the current state of the lake system and how it may evolve in the future under different circumstances. There is a statistically significant correlation between PCB levels in sediment and perch from 21 different sites in the Stockholm-Mälaren region, including Lake Oxundasjön and Rosersbergsviken, this was demonstrated with a linear regression model. With the multivariate analysis method principal component analysis (PCA), it was illustrated how the contaminant levels in fish from Lake Oxundasjön and Rosersbergsviken differed on contaminant levels in fish from other sites. The difference mainly concerned the size and composition of PCBs. Mass-balance modelling of quantities and flows of PCBs in Lake Oxundasjön and Rosersbergsviken was made in the simulation program STELLA®. The modelling indicated that the system currently serves as a secondary distribution source of PCBs to the environment. The recovery of PCB levels is slow in the system, it will take more than 25 years for concentrations in fish to reach today’s market limits and environmental quality standards for PCBs. The model was used to evaluate three different treatment methods for Lake Oxundasjön: dredging, capping and activated carbon treatment. Simulations of these treatments led to a substantial improvement of the PCB situation in Lake Oxundasjön. Moreover, they also had a positive impact on the recovery process in the downstream Rosersbergsviken. Future climate changes, with warmer temperatures and higher run off, led to a slightly faster recovery progress of PCBs in the system.

Persistent organic pollutants (POPs) are hydrophobic substances that readily sorb to organic matter in particles and colloids instead of being freely dissolved in the water phase. This sorption affects the bio­availability and environmental transport of the POPs. The major part of this thesis concerns the role of sediments as secondary sources of POPs. As the primary emissions decrease, contaminated sediments where POPs have accumulated can become the main source of contamination. If the contaminated sediment by time becomes covered with cleaner layers, the POPs are buried and no longer in contact with the aquatic environment. Experiments in this thesis showed, however, that new invading species can alter the sediment-water dynamics as a result of their bioturbation, i.e. mixing of sediment particles and pore-water. Marenzelleria spp., invading species in the Baltic Sea that burrow deeper than native species, were found to increase the remobilization of buried contaminants. The sediment-to-water flux was inversely related to the burial depth (2-10 cm) of the POP congeners (polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers) and also inversely related to the hydrophobicity of the congener. The flux was therefore most pronounced for less hydrophobic contaminants, which was linked to the bioirrigating behaviour of these species. Marenzelleria spp. also accumulated the buried POPs and increased concentrations in surface sedi­ment. Contaminants previously considered buried at a ’safe’ depth can thus be remobilized as a result of the invasion of Marenzelleria spp. in the Baltic Sea. One method to decrease the remobilization of contaminants from sediments is ’capping’, i.e. a layer of clean material is placed as a cap on the sediment. By amending the cap with active materials, which sequester the POPs and decrease their availability, thinner layers can be used (’active capping’ or ’thin-layer capping’). Results from an experiment with thin-layer capping using different active materials (activated carbon (AC) and kraft lignin) showed that both the sediment-to-water flux and the bioaccumulation by benthic species of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), hexachlorobenzene (HCB) and octachlorostyrene (OCS) decreased with increased thick­ness of the cap layer (0.5-5 cm). Amendments with active materials further increased the cap efficiency. AC was more efficient than kraft lignin, and a 3 cm cap with 3.3% AC reduced the flux and bioaccumulation with ~90%. The reduction of the sediment-to-water flux was inversely related to the hydrophobicity of the POP, and reductions in the flux had similar magnitudes as reductions in the concentration in deep-burrowing polychaetes, demonstrating the importance of bioturbation for sediment-to-water transport. In a one-year study on the levels of PCDD/Fs, PCBs, and HCB in a coastal area of the Baltic Sea, the correlations between the POP levels and the levels of particles and organic carbon in the water were found to differ for POPs of different structure and hydrophobicity. The levels of PCDD/Fs decreased to one third in May, which could be related to the increased sedimentation, i.e. water-to-sediment transport, during spring bloom.