Black liquors are presently combusted in recovery boilers where the inorganic cooking chemicals are recovered and the energy in the organic material is converted to steam and electricity. A new technology, developed by Chemrec AB, is black liquor gasification (BLG). BLG has more to offer compared to the recovery boiler process, in terms of on-site generation of electric power, liquid fuel and process chemicals. A prerequisite for both optimization of existing processes and the commercialization of BLG is better understanding of the physical and chemical processes involved including interactions with the refractory lining. The chemistry in the BLG process is very complex and to minimize extensive and expensive time-consuming studies otherwise required accurate and reliable model descriptions are needed for a full understanding of most chemical and physical processes as well as for up-scaling of the new BLG processes. However, by using these calculated model results in practice, the errors in the state of the art thermochemical data have to be considered. An extensive literature review was therefore performed to update the data needed for unary, binary and higher order systems. The results from the review reviled that there is a significant range of uncertainty for several condensed phases and a few gas species. This resulted in experimental re-determinations of the binary phase diagrams sodium carbonate-sodium sulfide (Na2CO3-Na2S) and sodium sulfate-sodium sulfide (Na2SO4-Na2S) using High Temperature Microscopy (HTM), High Temperature X-ray Diffraction (HT-XRD) and Differential Thermal Analysis (DTA). For the Na2CO3-Na2S system, measurements were carried out in dry inert atmosphere at temperatures from 25 to 1200 °C. To examine the influence of pure CO2 atmosphere on the melting behavior, HTM experiments in the same temperature interval were made. The results include re-determination of liquidus curves, in the Na2CO3 rich area, melting points of the pure components as well as determination of the extent of the solid solution, Na2CO3(ss), area. The thermal stability of Na2SO3 was studied and the binary phase diagram Na2SO4-Na2S was re-determined. The results indicate that Na2SO3 can exist for a short time up to 750 °C, before it melts. It was also proved that a solid/solid transformation, not reported earlier, occurs at 675 ± 10 °C. At around 700 °C, Na2SO3 gradually breaks down within a few hours, to finally form the solid phases Na2SO4 and Na2S. From HTM measurements a metastable phase diagram including Na2SO3, as well as an equilibrium phase diagram have been constructed for the binary system Na2SO4-Na2S. Improved data on Na2S was experimentally obtained by using solid-state EMF measurements. The equilibrium constant for Na2S(s) was determined to be log Kf(Na2S(s)) (± 0.05) = 216.28 – 4750(T/K)–1 – 28.28878 ln (T/K). Gibbs energy of formation for Na2S(s) was obtained as ΔfG°(Na2S(s))/(kJ mol–1) (± 1.0) = 90.9 – 4.1407(T/K) + 0.5415849(T/K) ln (T/K). The standard enthalpy of formation of Na2S(s) was evaluated to be ΔfH°(Na2S(s), 298.15 K)/(kJ mol–1) (± 1.0) = – 369.0. The standard entropy was evaluated to be S°(Na2S(s), 298.15 K)/(J mol–1 K–1) (± 2.0) = 97.0. Analyses of used refractory material from the Chemrec gasifier were also performed in order to elucidate the stability of the refractory lining. Scanning electron microscopy (SEM) analysis revealed that the chemical attack was limited to 250-300 μm, of the surface directly exposed to the gasification atmosphere and the smelt. From XRD analysis it was found that the phases in this surface layer of the refractory were dominated by sodiumaluminosilicates, mainly Na1.55Al1.55Si0.45O4.

This thesis deals with the use of electric fields for evaluation and control of chemical systems. An electric field can result in the flow of charge across an interface between a metal and a solution, by means of chemical reactions. This interplay between electricity and chemistry, i.e. electrochemistry, is a field of crucial importance both within research and industry. Applications based on electrochemical principles encompass such diverse areas as batteries and fuel cells, pH electrodes, and the glucose monitor used by people suffering from diabetes.A major part of the present work concerns the use of static electric fields in solutions containing a non-contacted metal surface. In such a setup it is possible to control the extent of electrochemical reactions at different positions on the metal. This allows the formation and evaluation of various types of gradients on electrodes, via indirectly induced electrochemical reactions. This approach is a new and simple way of forming for instance molecular gradients on conducting surfaces. These are very advantageous in biomimetic research, because a gradient contains a huge amount of discrete combinations of for example two molecules. The basis for the technique is the use of bipolar electrochemistry. Briefly, a surface can become a bipolar electrode (an electrode that acts as both anode and cathode) when the electric field in the solution exceeds a certain threshold value, thereby inducing redox reactions at both ends. In our experiments, the driving force for these reactions will vary along the electrode surface. Since the result of an electrochemical reaction can be the deposition or removal of material from an electrode, bipolar electrochemistry can be used to create gradients of that material on a surface. In order to gain a deeper understanding of these processes, the potential and current density distributions at bipolar electrodes were investigated with different methods. Especially the use of imaging techniques was important for the visualization and analysis of the gradients. Using this knowledge, the formation of more complex gradients was facilitated, and the results were further compared to simulations based on simple conductivity models. These simulations also provided us with means to predict the behavior of new and interesting setup geometries for pattering applications.The other major part is more application driven and deals with the use of alternating electric fields for chemical analysis, a technique known as electrochemical impedance spectroscopy (EIS). In this work, EIS has been applied for the analysis of engine oils and industrial cutting fluids. Emphasis was placed on practical aspects of the measurement procedure, and on the evaluation of the results using statistical methods. It was for example shown that it was possible to simultaneously determine the amount of different contaminants in low conducting solutions. Generally, EIS is used to measure the impedance of a solution or a solid, often as a function of the frequency of the alternating electric field. The impedance of a system is closely correlated to its complex dielectric constant, and EIS can therefor be used to examine many chemical and physical processes. It is further well suited for characterizing low conducting media with little or no redox-active species. The evaluation of impedance data is often a quite complex task, which is why we have made use of statistical methods that drastically reduce the effort and quickly reveal significant intrinsic parameters.

Fluctuations in protein structure are vital to function. This contrasts the dominating structure-function paradigm, which connects the well-defined three-dimensional protein structure to its function. However, catalysis is observed in disordered enzymes, which lack a defined structure. Disordered proteins are involved in molecular recognition events as well. The aim of this Thesis is to describe the structural changes occuring in protein structure and to investigate the mechanism of molecular recognition. Protein architecture is classified in a hierarchical manner, that is, it is categorized into primary, secondary, and tertiary levels. One of the major questions in biology today is how proteins fold into a defined three-dimensional structure. Some protein folding models, like the framework model, suggest that the secondary structure, like α-helices, is formed before the tertiary structure. This Thesis raises two questions: First, are structural fluctuations that occur in the protein related to the folding of the protein structure? Second, is the hierarchic classification of the protein architecture useful to describe said structural fluctuations? Kinetic studies of protein folding show that important dynamical processes of the folding occur on the microsecond timescale, which is why time-resolved fluorescence spectroscopy was chosen as the principal method for studying structural fluctuations in the peptides. Time-resolved fluorescence spectroscopy offers a number of experimental advantages and is useful for characterizing typical structural elements of the peptides on the sub-microsecond timescale. By observing the fluorescence lifetime distribution of the fluorescent probe, which is a part of the hydrophobic core of a four-helix bundle, it is shown that the hydrophobic core changes hydration state, from a completely dehydrated to a partly hydrated hydrophobic core. These fluctuations are related to the tertiary structure of the four-helix bundle and constitute structural transitions between the completely folded four-helix bundle and the molten globule version. Equilibrium unfolding of the four-helix bundle, using chemical denaturants or increased temperature, shows that the tertiary structure unfolds before the secondary structure, via the molten globule state, which suggests a hierarchic folding mechanism of the four-helix bundle. Fluctuations of a 12 amino acid long helical segment, without tertiary structure, involve a conformational search of different helical organizations of the backbone. Binding and recognition of a helix-loop-helix to carbonic anhydrase occurs through a partly folded intermediate before the final tertiary and bimolecular structure is formed between the two biomolecules. This confirms the latest established theory of recognition that the binding and the folding processes are coupled for the binding molecules.

A new NOx sensor for high-temperature applications has been developed and thouroghly characterised. The sensor layers are a mixed oxide of CoO, MgO and MgO2 deposited by thermal evaporation with a porous platinum gate on top, deposited by thermal evaporation or sputtering. The sensitivity and selectivity of the sensor is promising and is shown to depend upon the ratio between Co and Mg in the film and a number of competing mechanisms are shown to take place on the sensor surface. Response and recovery of the device is still slow and there are some drift, which are suggested to be due to a restructuring sensor surface during operation that was found by SEM-studies. Finally,the oxide surface has been characterized by XPS and a novel process for deposition of the sensor layers by lift-off technique has been developed.

<p>Car exhaust catalysts were introduced in the early 1980’s, to limit the release of pollutants such as hydrocarbons, carbon monoxides and nitrogen oxides. These catalysts contain noble metals such as palladium (Pd), platinum (Pt) and rhodium (Rh) and are able to simultaneously abate all three of the above-mentioned pollutants, hence the name three-way catalyst (TWC). The exposure to high temperatures (800-1000 °C) during operation and the presence of additives in petrol such as lead, calcium, silicon, magnesium, manganese, chromium, sulphur and phosphorus will after a certain time start to lower the overall effectiveness of the catalyst. These effects are either of a mechanical or a chemical nature. High temperatures reduce the active area by causing the noble metals to agglomerate and sinter whereas the additives alter the activity by either fouling the pores of the support material (phosphorus) or by interacting with the metals (sulphur and lead).</p><p>The main objective of this work was to develop a method to redisperse the catalytically active sites, comprising Pd, Pt and Rh on the washcoat surface, in an effort to regain lost catalyst activity. For this purpose, a wide spectrum of different commercial car exhaust catalysts containing varying noble metal loadings, aged under various driving conditions and with mileages ranging from 30 to 100 000 km were evaluated.</p><p>The influence of a thermal treatment in a controlled gas atmosphere, such as oxygen or hydrogen and a redispersing agent, e.g. chlorine, on the activity of TWC was investigated by means of laboratory-scale activity measurements. Several complementary characterisation methods such as SEM/TEM, XRD, BET and TPR were used to verify the effects of the regeneration treatments on the catalyst morphology (Paper I). Partial regeneration of catalyst activity and noble metal dispersion was achieved after thermal treatment in an oxygen-chlorine rich atmosphere at temperatures below 500 °C.</p><p>Finally, an investigation of the effects of an oxy-chlorine thermal treatment for regeneration of a ‘full-scale’ commercial automotive three-way catalyst was performed. Catalyst activity and performance prior to and after the oxy-chlorine thermal treatment was measured on a test vehicle in accordance with the European driving cycle (EC2000). The catalyst surface was further characterised using XRD and EDX (Paper II). Improved catalyst activity for a high mileage catalyst could be observed, with emissions lowered by approximately 30 to 40 vol% over the EC2000 driving cycle</p>

Photoinduced electron transfer is involved in a number of photochemical and photobiological processes. One example of this is photosynthesis, where the absorption of sunlight leads to the formation of charge-separated states by electron transfer. The redox equivalents built up by successive photoabsorption and electron transfer is further used for the oxidation of water and reduction of carbon dioxide to sugars. The work presented in this thesis is part of an interdisciplinary effort aiming at a functional mimic of photosynthesis. The goal of this project is to utilize sunlight to produce renewable fuels from sun and water. Specifically, this thesis concerns photoinduced electron transfer in donor(D)-photosensitizer(P)-acceptor(A) systems, in mimic of the primary events of photosynthesis. The absorption of a photon typically leads to transfer of a single electron, i.e., charge separation to produce a single electron-hole pair. This fundamental process was studied in several molecular systems. The purpose of these studies was optimization of single electron transfer as to obtain charge separation in high yields, with minimum losses to competing photoreactions such as energy transfer.Also, the lifetime of the charge separated state and the confinement of the electron and hole in three-dimensional space are important in practical applications. This led us to explore molecular motifs for linear arrays based on Ru(II)bis-tridentate and Ru(II)tris-bidentate complexes. The target multi-electron catalytic reactions of water-splitting and fuel production require a build-up of redox equivalents upon successive photoexcitation and electron transfer events. The possibilities and challenges associated with such processes in molecular systems were investigated. One of the studied systems was shown to accumulate two electrons and two holes upon two successive excitations, without sacrificial redox agents and with minimum yield losses. From these studies, we have gained better understanding of the obstacles associated with step-wise photoaccumulation of charge and how to overcome them.

Wood is a complex material and the mechanical properties are influencedby a number of structural parameters. The objective of this study has been toinvestigate the relationship between the structure and the mechanical propertiesof hardwood. Two levels were of special interest, viz. the cellular structureand morphology of the wood, and the ultra-structure of the cell wall. In thenext step, it was of interest to examine how the mechanical properties ofhardwood change with spontaneous/induced changes in morphology and/orchemical composition beyond the natural variation found in nature. Together, this constituted the framework and basis for two larger projects,one on European aspen (Populus tremula) and hybrid aspen (Populus tremulax Populus tremuloides), and one on European oak (Quercus robur). Amethodology was developed where the concept of relative density and compositemechanics rules served as two useful tools to assess the properties ofthe cell wall. Tensile testing in the longitudinal direction was combined withchemical examination of the material. This approach made it possible to revealthe mechanical role of the lignin in the cell wall of transgenic aspen trees,and investigate the consequences of holocellulose degradation in archaeologicaloak from the Vasa ship. The study on transgenic aspen showed that a major reduction in lignin inPopulus leads to a small but significant reduction in the longitudinal stiffness.The longitudinal tensile strength was not reduced. The results are explainableby the fact that the load-bearing cellulose in the transgenic aspen retained itscrystallinity, aggregate size, microfibril angle, and absolute content per unitvolume. The results can contribute to the ongoing task of investigating andpinpointing the precise function of lignin in the cell wall of trees. The mechanical property study on Vasa oak showed that the longitudinaltensile strength is severely reduced in several regions of the ship, andthat the reduction correlates with reduced average molecular weight of theholocellulose. This could not have been foreseen without a thorough mechanicaland chemical investigation, since the Vasa wood (with exception fromthe bacterially degraded surface regions) is morphologically intact and witha micro-structure comparable to that of recent oak. The results can be usedin the ongoing task of mapping the condition of the Vasa wood. / QC 20110420

A balanced supply of micronutrients, including metals such as iron (Fe), cobalt (Co), and nickel (Ni), is required for the efficient and stable production of biogas. During biogas formation, the uptake of micronutrient metals by microorganisms is controlled by a complex network of biological and chemical reactions, in which reduced sulfur (S) compounds play a central role. This thesis addresses the interrelationship between the overall chemical speciation of S, Fe, Co, and Ni in relation to the metals bio-uptake processes. Laboratory continuous stirred tank biogas reactors (CSTBR) treating S-rich grain stillage, as well as a number full-scale CSTBRs treating sewage sludge and various combinations of organic wastes, termed co-digestion, were considered. Sulfur speciation was evaluated using acid volatile sulfide (AVS) extraction and S X-ray absorption near edge structure (XANES). The chemical speciation of Fe, Co, and Ni was evaluated through the determination of aqueous metals and metal fractions pertaining to solid phases, as well as kinetic and thermodynamic analyses (chemical speciation modelling). The relative Fe to S content in biogas reactors, which in practice is regulated through the addition of Fe for the purpose of sulfide removal or prior to the anaerobic digestion of sewage sludge, is identified as a critical factor for the chemical speciation and bio-uptake of metals. In the reactors treating sewage sludge, the quantity of Fe exceeds that of S, inducing Fe(II)-dominated conditions under anaerobic conditions, while sulfide dominates in the co-digestion and laboratory reactors due to an excess of S over Fe. Under sulfide-dominated conditions, chemical speciation of the metals is regulated by hydrogen sulfide and the formation of metal sulfide precipitates, which in turn restrict the availability of metals for microorganisms. However, despite the limitations set by sulfide, aqueous concentrations of different Co and Ni species were shown to be sufficient to support metal acquisition by the microorganisms under sulfidic conditions. Comparatively, the concentrations of free metal ions and labile metal-phosphate and -carbonate complexes in aqueous phase, which directly participate in bio-uptake processes, are higher under Fe-dominated conditions. This results in an enhanced metal adsorption on cell surfaces and faster bio-uptake rates. It is therefore suggested that the chemical speciation and potential bioavailability of metals may be controlled through adjustments of the influent Fe concentration in relation to S content. The results also indicated that the pool of metal sulfides in the biogas reactors could be regarded as a source of metals for microbial activities. Thus, the recovery and utilisation of this fraction of metals may be considered as a measure with which to minimise the metal dosing concentrations to CSTBRs. / För att en effektiv och stabil biogasproduktion från organiskt avfall skall uppnås, behöver mikroorganismer i biogasreaktorer ha tillgång till näringsämnen inklusive spårmetaller såsom järn (Fe), kobolt (Co), och nickel (Ni). Mikroorganismernas upptag av spårmetaller styrs av biologiska och kemiska reaktioner som påverkar metallernas tillgänglighet, där framför allt interaktioner mellan metaller och reducerat svavel (S) spelar en viktig roll. Avhandlingen analyserar sambandet mellan kemisk speciering av S, Fe, Co, och Ni i relation till metallernas biologiska upptagsprocesser. Omrörda tankreaktorer (CSTBR) i lab.- och fullskala för produktion av biogas från spannmålsdrank, avloppsslam, och olika kombinationer av organiska avfall (samrötning) har utgjort basen för studierna. Svavelspeciering analyserades med hjälp av AVS (acid volatile sulfide) extraktion och S XANES (sulfur X-ray absorption near edge structure). Speciering av Fe, Co, och Ni utvärderades med hjälp av sekventiell extraktion, mätning av metall koncentrationer i löst och fast faser samt genom kinetiska och termodynamiska analyser (kemisk specieringsmodellering). Biogasreaktorers relativa mängder av Fe och S, identifierades som en central faktor för kemisk speciering och bio-upptag av metaller. Järn-mängden regleras bl a genom tillsats av Fe för att rena biogasen från vätesulfid eller vid diverse fällningsreaktioner i reningsverk före rötningsstegen av avloppsslam. Därför är järnhalterna högre än S-halterna i reaktorer, som behandlar avloppsslam. Detta leder till en Fe(II)-dominerande miljö. Däremot dominerade vätesulfid i de samrötnings- och laboratoriereaktorer, som ingick i studien. Under dessa förhållande styrs den kemiska metallspecieringen av sulfid och fr a genom fällning av metallsulfider, som då begränsar tillgängligheten av metaller för mikroorganismerna. Trots begränsningarna via sulfidfällningen var koncentrationen av de lösta Co och Ni formerna tillräckliga för bio-upptag av dessa metaller. Vid de Fe-dominerade förhållandena var koncentrationer av fria metalljoner och labila komplex (t.ex. med fosfat och karbonat), som direkt deltar i bio-upptagsprocesser, relativt höga, vilket medför relativt goda möjligheter för metalladsorption till cellytor och bio-upptag. Resultaten visar att den kemiska specieringen och därmed biotillgängligheten av metaller skulle kunna regleras genom justering av inflödet Fe i förhållande till S. Resultaten visade också att metallsulfider i fast fas sannolikt utnyttjas av mikroorganismer som en källa till metaller. Det innebär att en återanvändning av denna metallfraktion skulle kunna utnyttjas som en del i att minimera metalldoseringskoncentrationer.

Water is used every day in society and to be able to recycle this water we depend upon efficient wastewater treatment. It is vital to test the wastewater based on different parameters. One parameter is the Chemical Oxygen Demand (COD), which defines the amount of organic substances that can be chemically oxidized within the water. The Swedish standardized analytical method for COD (SS-028142), COD(Cr) is dependent on mercury, a substance which was banned according to Swedish regulations in year 2009 but is still used due to time limited dispensations. This report is a part of a pre-procurement innovative project initiated by the Swedish Water and Wastewater Association (SWWA) in order to bring forward and evaluate mercury free analytical methods for COD for municipal wastewater. The aim was to validate three analytical methods for COD: Chloride Determination, Chloride Elimination and PeCOD and compare the analytical results to the standardized COD(Cr). Three laboratories, Käppala (Stockholm), Gryaab (Gothenburg) and Komlab (Örnsköldsvik) were included in the validation process by providing analytical data. The validation was conducted using the data as input for the statistical methods regression, correlation and analysis of variance to investigate the performance of the individual methods. As a complement to the statistical results, comments regarding the methods brought up by the laboratory staff were compiled in order to reflect on the usability and robustness of the methods.  The results indicated that the method Chloride Determination was the method most similar to the COD(Cr) method, when investigating obtained COD concentrations, required analytical time and implementation steps needed to obtain a final COD value. This result was evident by high coefficient of determination values for influent wastewater samples. The PeCOD method, which was submitted in two versions, one manual and one automatic was only able to analyze soluble COD. It was found that the PeCOD methods obtained lower COD concentrations compared to the standardized method when analyzing filtered samples. Due to highly variable correlation coefficients between the PeCOD and COD(Cr) for various types of samples indicated that no uniform linear relation between the methods was present. Analysis with the Chloride Elimination method was halted early in the validation process, but was found to receive approximately 50 percent lower COD values than the reference method  COD(Cr). Finally it can be said that the input data for conducting the statistical test were limited and further analysis should be recommended in order to validate the results with a higher certainty. / Varje dag produceras avloppsvatten i samhället och för att kunna återanvända detta vatten krävs en tillförlitlig reningsprocess. För att rena avloppsvatten effektivt är det betydelsefullt att kontinuerligt testa avloppsvattnet utifrån ett antal viktiga parametrar. En av dessa är kemisk syreförbrukning, COD, som definieras av den mängd syre som förbrukas genom fullständig kemisk oxidation av organiskt material. Den svenska standardiserade analysmetoden för COD (SS-028142) , COD(Cr) är beroende av kvicksilver för att erhålla ett korrekt analysresultat utan påverkan av kloridjoner. Kvicksilver är enligt Svensk lag förbjudet sedan år 2009, men analysmetoden är dock vanligt använd på svenska avloppsreningsverk tack vare årliga dispenser. Detta examensarbete är en del av en förkommersiell innovationsupphandling som initierats av Svenskt Vatten med mål att undersöka och validera kvicksilverfria analysmetoder för COD tillgängliga på den internationella marknaden. Projektets syfte var att utföra en validering av tre analysmetoder: Klorid Determination, Klorid Elimination och PeCOD och jämföra dess resultat med referens metoden COD(Cr). Tre olika laboratorier, Käppala (Stockholm), Gryaab (Göteborg) och Komlab (Örnsköldsvik) medverkade i projektet. Valideringen genomfördes med de statistiska metoderna regression, korrelation och variansanalys, utifrån insamlade mätdata i syfte att undersöka de givna metodernas prestanda. Som ett komplement till det statistiska testerna sammanställdes synpunkter som framkommit under analysarbetet av laboratoriepersonal, för bedömning av metodernas användarvänlighet och robusthet.  Utifrån valideringen var det tydligt att metoden Klorid Determination hade störst likhet med COD(Cr) metoden utifrån givna analysresultat, analystid samt utförda analyssteg. Detta resultat styrktes av höga värden för determinationskoefficients för inkommande avloppsvatten mellan innovatios metoden och referense metoden COD(Cr). Analysmetoden PeCOD bestod av två olika versioner, skildrade den lösliga COD innehållet i provet istället för den total COD koncentrationen som hos COD(Cr). Oavsett vilken version av PeCOD som används erhålls ett lägre COD resultat jämfört med referens metoden COD(Cr) då filtrerade prover analyserades. De framtagna varierande korrelations koefficienter mellan PeCOD och COD(Cr) indikerade att ingen enhetlig korrelation gick att finna mellan metoderna hos de olika laboratorierna. Analysmetoden COD Elimination pausades tidigt i processen men de tidiga testerna visade på halverade COD koncentrationer jämfört med referens metoden.  Slutligen kan det nämnas att mätdata som användes som indata till de beskrivna statistiska testerna var begränsade och att vidare analyser rekommenderas för att kunna bevisa givna resultat med ökad sannolikhet.

From domestic and industrial waste water will have to be cleaned before it can be released into lakes and streams again. This purification takes place through various stages of treatment plants. Wastewater contains many substances that are harmful to the environment as well as human and animal health, so it is important that the purification that is done is done in an efficient and thoughtful manner. The steps that are common in Swedish cleaning plants are mechanical, biological and chemical purification. These purification steps ensure that larger particles do not come out to the open water, convert nitrogen into nitrogen through the activation process, and that by chemical treatment, the emission of phosphorus is reduced. All of these purification steps can be designed differently and vary from purification plants to purification plants. Therefore, the degree of purification and emissions can distinguish between different treatment plants. Because there are many factors involved in the processes at Swedish waste treatment plants, it is important to carry out annual audits to detect problems that can lead to environmental damage.If cleaning does not work, exercise can increase in lakes and seas, which causes people and animals to suffer. Bottom dead and acid deficiency are already a major problem for the Baltic Sea. In order to reduce the negative environmental effects, emissions of nutrients are drastically reduced. This concerns the release of nutrients from all countries around the Baltic Sea.This study focuses on nitrogen and phosphorus purification from 5 wastewater treatment plants, Henriksdal's purification plant (Stockholm), Ryaverket (Gothenburg), Sjölunda purification plant (Malmö), Kungssängsverket (Uppsala) and Duvbacken purification plant (Gävle). Information about its activities has been obtained through interviews and works own reports.The purification plants use different technical solutions, and all treatment plants meet today's requirements for purification. The biggest difference is the degree of nitrogen purification. All wastewater treatment plants have a history of changes in technical solutions to improve treatment. Cleaning wastewater from households and industries costs a lot of money for the treatment plants, so it's always a challenge for the wastewater treatment plants to clean the water in the best possible way without costing too much.It is expected that the cleaning requirements will be tightened and all treatment plants should continue to develop to increase efficiency. Current purification requirements are designed to suit the recipient's sensitivity. If the EU's idea of ​​the same degree of purification across the country is transformed into requirements, Duvbacken will need to significantly improve the nitrogen treatment at the waste water treatment plant. / Från hushåll och industri kommer det avloppsvatten som måste renas innan det kan släppas ut i sjöar och vattendrag igen. Denna rening sker genom olika steg i reningsverk. Avloppsvattnet innehåller många ämnen som är skadliga för miljön samt människors och djurs hälsa, därför är det viktigt att reningen som sker görs på ett effektivt och genomtänkt sätt. De steg som är vanliga i de svenska reningsverken är mekanisk, biologisk och kemisk rening. Dessa reningssteg ser till att större partiklar inte följer med ut till det öppna vattnet, omvandlar kväve till kvävgas genom aktivtslamprocessen, samt att genom kemisk rening minskar man utsläppen av fosfor. Alla dessa reningssteg kan utformas på olika sätt och variera från reningsverk till reningsverk. Därför kan reningsgraden och utsläppsmängderna skilja mellan olika reningsverk. Eftersom det är många faktorer som spelar in när det gäller processerna på svenska reningsverk är det viktigt med årliga granskningar för att upptäcka problem som kan leda till miljöskador.   Fungerar inte reningen kan bland annat övergödningen öka i sjöar och hav vilket leder till att människor och djur drabbas. Bottendöd och syrebrist är redan ett stort problem för Östersjön. För att minska de negativa miljöeffekterna gäller det att utsläppen av näringsämnen minskar drastiskt. Detta gäller utsläpp av näringsämnen från alla länder runt om Östersjön.   Denna studie fokuserar på kväve och fosforrening från 5 st avloppsreningsverk, Henriksdals reningsverk (Stockholm), Ryaverket (Göteborg), Sjölunda reningsverk (Malmö), Kungssängsverket (Uppsala) och Duvbackens reningsverk (Gävle). Information om dessas verksamheter har erhållits genom interjuver och verkens egna rapporter.   Reningsverken använder olika tekniska lösningar, och samtliga reningsverk uppfyller dagens krav på rening. Största skillnad är reningsgraden för kväve. Samtliga reningsverk har en historia av förändringar av tekniska lösningar för att förbättra reningen. Att rena avloppsvattnet från hushåll och industrier kostar mycket pengar för reningsverken, därför är det hela tiden en utmaning för reningsverken att rena vattnet på bästa möjliga sätt utan att det kostar för mycket.   Man kan förvänta sig att reningskraven skärps och alla reningsverk bör fortsätta att utvecklas för att öka effektiviteten. Nuvarande krav på reningsgrad är så utformad att de är anpassad till recipientens känslighet. Om EU:s ide om samma reningsgrad över hela landet omvandlas till krav, kommer Duvbacken behöva förbättra kvävereningen vid reningsverket avsevärt