The water and sewage system is classified as a necessary social function in Sweden. In order to obtain a functional system with acceptable amounts of malfunctions, continuous maintenance and renewal by replacing existing pipes where life expectancy is considered exhausted. The rate of change can be defined as the renewal. The majority of Sweden's pipeline networks were built in the 60s and 70s, and the renewal pace has remained low since then, in relation to the service life of the pipeline. If the renewal pace is too low for a long period of time, future difficulties can arise because pipes ages faster than the renewal pace. Many municipalities in Sweden have maintenance and renewal plans to achieve goals such as increasing/maintaining customer service for water and sewage system. At the renewal planning for each municipality, a tool published by Svenskt Vatten can be used to estimate the general renewal need for the entire municipality. The tool is for instance based on year of installation, pipe material and length of the pipe length in the system. A general renewal need provides a good overall measure of the municipality's need, but it does not make it easier to prioritize internal renewal. The purpose of this thesis was to provide a method for determining where the resources in a municipality should be placed in order to maintain or increase customer service regarding water services connected to wiring networks. The method is based on a prioritization that was carried out by combining customer service and the water management system's condition. In this study, the method of prioritization was applied in a case study at the municipality of Boden. To identify the condition of the pipe network, several different influencing factors have been analysed to identify critical areas. An area-based valuation model has been developed based on a Swedish valuation model from 2007. The results showed correlation between leakage frequency on the water pipeline network and various influencing factors such as soil types, pipe materials and construction year. A method has been developed to help municipalities to compile the influencing factors that are critical to that particular municipality based on the information available in the municipality. A methodology for how municipalities can compile operational disturbances and illustrate these with a map-based independent database have also been developed. An area-based valuation model was developed to enable assessment of customer service independent municipality and its resources. In this tool, the municipality itself is able to determine the importance of parameters. The valuation of customer service was based on the number of customers affected, building, length of the pipes and malfunctions reports. However, these parameters are not linked to synergy or critical wires based on a social perspective. The valuation model should therefore be supplemented with an assessment of the consequences of interference. A conclusion from the case study was that the entire municipality's main management network showed increased trends in leakage rates. Trends also showed that customer satisfaction in the majority of areas is falling over time, based on results from site evaluation. A recommendation was made to the municipality in the case study in which areas renewal should be prioritized over the coming five years based on the valuation of customer service and management condition. / Vatten- och avloppssystemet klassas som en nödvändig samhällsfunktion i Sverige. För att erhålla ett funktionellt system med acceptabla mängder driftstörningar krävs kontinuerligt underhåll och förnyelse i form av utskiftning av befintliga ledningar där livslängden anses förbrukad. Takten utskiftning kan definieras som förnyelsetakten. Majoriteten av Sveriges ledningsnät byggdes under 60–70 -talet och förnyelsetakten har förblivit låg sedan dess, i förhållande till ledningsnätets livslängd. Om förnyelsetakten är för låg under en för lång tid kan framtida svårigheter uppstå eftersom ledningar åldras snabbare än förnyelsetakten. Många kommuner i Sverige har underhåll- och förnyelseplaner för att uppnå mål som exempelvis att öka/bibehålla kundservice för vatten och avloppsledningsnätet. Vid förnyelseplaneringen för respektive kommun kan ett verktyg användas som publicerats av branschorganisationen Svenskt Vatten för att uppskatta behovet av generell förnyelsetakt för hela kommunen. Verktyget är bland annat baserat på anläggningsår, ledningsmaterial och längd på ledningarna i systemet. En generell förnyelsetakt ger ett bra helhetsmått över kommunens behov av insatser men det underlättar inte hur den interna förnyelsen skall prioriteras. Syftet med detta examensarbete var att ta fram en metod för hur man kan bestämma var resurserna i en kommun ska placeras för att bibehålla eller öka kundservice rörande vattentjänster kopplade till ledningsnät. Metoden baseras på en prioritering som utfördes genom att kombinera kundservice och vattenledningsnätets kondition. I denna studie tillämpades prioriteringsmetoden i en fallstudie på Boden kommun. För att identifiera ledningsnätets kondition har flera olika påverkande faktorer analyserats för att identifiera kritiska områden. En områdesvis värderingsmodell har utvecklats baserad på en svensk värderingsmodell från 2007. Resultaten visade korrelation mellan läckfrekvens på vattenledningsnätet och olika påverkande faktorer såsom jordart, ledningsmaterial samt anläggningsår. En metod har framtagits för att hjälpa kommuner att sammanställa vilka påverkande faktorer som är kritiska för just den kommunen baserat på den informationen kommunen kan tillgå. En metodik för hur kommuner kan sammanställa driftstörningar och illustrera dessa med ett kartverktyg oberoende databas har även framtagits. En områdesvis värderingsmodell utvecklades för att möjliggöra bedömning av kundservice oberoende kommun och dess resurser. I detta verktyg har kommunen själv möjlighet att bestämma parametrars vikt. Värderingen av kundservice baserades på antal kunder som påverkas, fastigheter, ledningslängd och driftstörningsrapporter. Dessa parametrar är dock inte kopplade till samordningsvinster eller kritiska ledningar utifrån ett samhällsperspektiv. Värderingsmodellen bör därför kompletteras med bedömning av konsekvens av störningar. En slutsats från fallstudien var att hela kommunens huvudledningsnät visade på ökande trender avseende läckfrekvens. Trenderna visade även att kundnöjdheten i majoriteten av områdena sjunker över tid, baserat på resultat från områdesvärderingen. En rekommendation togs fram för kommunen i fallstudien för i vilka områden förnyelse bör prioriteras de kommande fem åren baserad på värderingen av kundservice samt ledningskonditionen.

Argon oxygen decarburization slag (AOD) was tested in batch and column experiments to investigate its phosphorus (P) removal performance. The effects of factors such as AOD dose, initial P concentration of the feeding solution, and aging on the P removal ability of the slags were analyzed. In a column experiment, electric arc furnace slag (EAF), blast furnace slag (BFS) and AOD were combined in five different ways to determine optimal conditions for P removal. In another column experiment, the three types of slag were modified with polyethylene glycol (PEG) and NaOH to adjust their dissolution properties and the effect on P removal performance was examined. In the batch experiments, AOD exhibited very promising P removal ability. It removed 94.8% of P from 6.5 mg P L-1 synthetic solution in 4 hours with a dose of 5 g L-1. Maximum P removal capacity of 27.5 mg P g-1 was achieved. In the dual-filter column experiment, the column packed with only EAF had the best P removal performance (consistently above 93%). Amorphous calcium phosphate (ACP) was identified as the main P species in the five slag samples collected from the outlet chambers. The contributions from crystalline calcium phosphate (Ca-P) and P adsorbed on iron/aluminum (hydr)oxides were greater in samples from the inlet chambers. The P speciation results revealed that P was predominantly removed by the slags through formation of ACP. The second column experiment showed that modification with PEG and NaOH solution only enhanced short-term P removal by the slags. However, exhaustion of the modified slags occurred much earlier, indicating that the modification process had shortened the lifespan of the slags. Untreated AOD showed better P removal than untreated EAF until pore volume 244, probably due to faster dissolution rate of gamma dicalcium silicate (dominating in AOD according to the XRD results) than of beta dicalcium silicate (dominating in EAF). / <p>QC 20170830</p>

One of the Government's environmental quality objectives is to achieve a poison free environment, meaning that the presence of anthropogenic substances in the environment should not pose a threat to human health or biodiversity. Such a substance is chlorinated aliphatic hydrocarbons which have been used historically in dry cleaning and as degreasing agents within industrial processes. In recent years, negative effects on human health have been found since exposure to chlorinated solvents is associated with toxic and carcinogen effects, which has resulted in constrictions against such substances today.At the former Whirlpool industry in Himmelstalund, in Norrköping, the chlorinated solvents perchlorethylene (PCE) and trichlorethylene (TCE) have been used historically during production. Concentrations of PCE and TCE and their degradation products cis–1,2–dichloroethylene (cis–1,2–DCE) and vinyl chloride (VC) have been detected in groundwater at the site. This Master´s thesis aimed to develop a site–specific groundwater flow model and a mass transport model to simulate the spread of these compounds through the saturated zone after 10, 30 and 75 years. The groundwater model was developed in MODFLOW and calibrated based on known hydrological and geological conditions after which a sensitivity analysis was performed regarding hydraulic conductivity and effective porosity. It was found that the flow model generated flows which corresponded to measured ones when hydraulic conductivity was employed within the range 10–5–10–2 m/s and effective porosity in the range 5–25%.It was found that PCE, TCE and cis–1,2–DCE did not reach the surface water recipient Motala river within 75 years, the compounds traveled 500 meters west of the source zone as furthest. However, VC reached Motala river within ten years, depending on which initial concentration were applied. The plume of VC remained in the aquifer after 75 years containing concentrations exceeding the guideline values in groundwater. This is considered severe since chlorinated solvents are toxic and cancerogenic to humans.A sensitivity analysis with regard to adsorption and reaction parameters was performed where it was found that the adsorption greatly affected the spread of the plumes and was more influencing than how the reaction parameters were applied. When maximum adsorption was employed, PCE, TCE and cis–1,2–DCE remained adjacent to the source zone while VC moved about 500 meters. It was seen that the mobile properties of the compounds were considerably larger for all components when minimal adsorption was applied. Hydraulic conductivity had a major impact on transport times where higher hydraulic conductivity resulted in faster transportation through the aquifer.As the spread through the aquifer was largely affected by which parameters were chosen, it was assessed relevant to measure hydraulic conductivity, adsorption constants and measure groundwater levels in more points spread in the model area in order to improve the reliability of the mass transport model.

Havs- och vattenmyndigheten har tagit fram bedömningsgrunder för ekologisk status av ytvatten. Vid bedömning av ekologisk ytvattenstatus tas hänsyn till så kallade särskilt förorenade ämnen (SFÄ), ett av dessa ämnen är uran. Enligt Miljöbalkens andra kapitel om allmänna hänsynsregler ska en verksamhetsutövare motverka att verksamheten medför skada eller olägenhet för människors hälsa eller för miljön. LKAB är ett statligt ägt gruvbolag som bedriver brytning och förädling av järnmalm i Kiruna, Malmberget och Svappavaara. Denna studie gäller LKABs verksamhet i Kiruna. Gruvbrytningen och förädlingen av järnmalm är vattenkrävande processer. Vatten som pumpas upp från gruvan går till processen och huvuddelen av vattnet recirkulerar inom verken. Utgående vatten från verk går till dammarna och vidare till klarningsmagasin. Från klarningsmagasinet returpumpas sedan delar av vattnet tillbaka till processen. Överskottsvatten bräddas efter sedimentering och klarning. Bräddningen sker till sjön Mettä Rakkurijärvi och vidare till Kalix älv via Rakkurisystemet. Det vatten som bräddas har uranhalter överskridande gällande bedömningsgrunder för särskilt förorenade ämnen (SFÄ). På grund av detta ligger det i LKABs intresse att undersöka uran i LKABs process, detta för att i förlängningen eventuellt kunna minska de förhöjda halterna i recipienten. Uran är ett radioaktivt metalliskt grundämne som tillhör gruppen aktiniderna i periodiska systemet och ett redoxelement på grund av dess förmåga att byta oxidationstal. De vanligaste förekommande oxidationstalen för uran i kemiska föreningar är (IV) och (VI). Ett ämnes biotillgänglighet och egenskaper i ett vatten styrs till viss del av vilken speciering ämnet har, partikulär, kolloidal eller löst fas. I oxiderade miljöer kontrolleras den totala urankoncentrationen av U(VI) och mobiliteten relateras till kolloidala fraktionerna. I vatten med högt karbonatinnehåll förekommer uran ofta som uran-karbonatkomplex vilket gör uran mer mobilt och minskar dess förmåga att adsorberas på andra partiklar. Komplexbildning och sorption därmed två viktiga processer som påverkar urans mobilitet och biotillgänglighet. Tidigare utredningar har visat på att uranyljonerna som finns i processvattnet främst förekommer som de lösta komplexen Ca2UO2(CO3)3(aq) och CaUO2(CO3)32- och att den höga halten av karbonater och kalcium i LKABs processvatten påverkar den kemiska specieringen. Syftet med detta examensarbete är att undersöka hur halten uran i vattnet förändras i processen från gruva till dammar. För att uppnå målet har studien strukturerats utifrån följande frågeställningar: • På vilka platser i processen syns förändringar i uranhalten och kan det förklaras av den teori som finns om urans biogeokemi i vatten? • Ses samband mellan uranhalten och andra ämnen eller parametrar i processen och kan dessa förklaras av den teori som finns om urans biogeokemi i vatten? Denna studie är en sammanställning och utvärdering av befintliga mätdata som LKAB insamlat under tidsperioden 2015-2019. Förslag på fortsatt arbete är att utföra adsorptionsmodelleringar för uran i processvattnet. Vidare skulle en ytterligare avgränsning av detta arbete kunna utföras, till exempel att enbart kolla på anrikningsverk eller dammar där det enligt denna studie sker förändringar i uranhalten / Waterface-Environmental Forensics

Blue-green infrastructure have been more lucrative during the last 30 years, since urbanizationbrings more impervious surfaces that increases stormwater runoff volumes. Amongst thedifferent blue-green infrastructures there are e.g., constructed wetlands and swales. Blue-greeninfrastructure means more natural management of the stormwater, such as infiltration. Forinfiltration of water, the hydraulic conductivity is an important parameter, but also the abilityto remove dissolved pollutants. In literature, various studies of filter materials are only testedfor single dissolved pollutants, which might be a disadvantage as this does not represent fieldconditions where metals usually co-exist. Economic costs are also an important parameter,unfortunately not always targeted in research. In this thesis, the efficiency of five different material mixtures for removing typical dissolvedstormwater pollutants: chromium (Cr), copper (Cu), nickel (Ni), phosphorus (P), lead (Pb) andzinc (Zn) were studied. The mixtures were following: 1) crushed rock + soil (RO_SO) 2)crushed rock + soil + LECA 4/10 + biochar (RO_SO_BC_LC4). 3) crushed rock + soil + LECA10/20 + biochar (RO_SO_BC_LC10). 4) Soil (SO). 5) crushed rock + soil + biochar(RO_SO_BC). This study was a part of blue-green investments that is being made in Östersundmunicipality and the use of low-cost materials for stormwater treatment are examined. The study was made using batch equilibrium tests, to determine the sorption capacity fordifferent material mixtures, using dissolved metal- and P-solutions. The measured data werefitted to Freundlich, Langmuir, Temkin, Dubinin-Radushkevich and Redlich-Petersonisotherms. Economic feasibility has also been compared between the material mixtures.Results showed that SO had the best sorption capacity for all metals and P, with rankingPb &gt; Cr &gt; Cu &gt; Ni &gt; Zn for the metals. All material mixtures showed a removal efficiency of79-99%, at the lowest concentration (1mg/L) for the metals and 31-62% for the lowestconcentration of P-single solution (1mg/L). Using additional materials in the mixtures, such asbiochar, slightly improved the sorption capacities of Pb and P. Redlich-Peterson isothermsprovided the best fits to the data. An economic evaluation of the ingoing materials shows thatSO and RO_SO are undoubtedly the most feasible alternatives for removal of targeted metalsand P.

I Stockholms regionala vattenförsörjningsplan har vattenresurser i Stockholmsregionenundersökts och prioriteras utifrån deras betydelse för länets vattenförsörjning nu och i framtiden. Sex av de högprioriterade vattenresurserna i Norrvattens verksamhetsområde har valts ut eftersom de saknar befintligt vattenskydd eller har vattenskydd som behöver revideras. Vid införande eller utökande av vattenskydd kan intressekonflikter uppståmed aktörer som är verksamma inom det tilltänkta vattenskyddsområdet. I detta arbete används Arc-GIS för att undersöka utvalda intressekonflikter. I första hand undersöks åkerarealen inom modellerade vattenskyddsområden och kostnader för att ersätta jordbrukare vid försvårad markanvändning i samband med vattenskydd. Utöver analysen kring jordbruksmark identifieras, utreds och riskklassificeras intressekonflikter med vattenskydd för riskobjekten vägar, järnvägar, industrier och övrig bebyggelse. Naturskyddsområden är inkluderade men ses inte som en intressekonflikt med vattenskydd. Naturskyddsområden innebär ett ytterligare skydd för vattentäkten. Resultatet visar att Röåsen-Bergby i Norrtälje kommun är den vattenresurs i norra Stockholmsregionen med flest enskilda intressekonflikter. Grundvattenmagasinet har både ovanpå och i nära omgivning stora arealer åkermark, tungt trafikerade vägar och betydande bebyggelse med både industrier och bostäder. För de sammankopplade grundvattenmagasinen Uppsalaåsen-Toresta/ Lindormsnäs finns måttliga arealer åkermark nära magasinet och en förhöjd risk från väg, järnväg, industri och övrig bebyggelse. Ytvattentäkten Fysingen har stora arealer omgivande åkermark. Ytvattnet ligger nära E4 och har vältrafikerade järnvägar, men sjön är skyddad till större del av vattenskydd som införts för närliggande åsar och innehar ett naturskydd vilket minskar risken för påverkan från omgivande riskobjekt. Ytvattentäkten Erken har högsta prioritet i Stockholms regionala vattenförsörjningsplan men sammanlagt få riskobjekt. Erken har mindre arealer åkermark närmast sjön samt många naturreservat och ett befintligt vattenskydd. Ytvattentäkten Largen har utifrån avgränsningen endast en mycket liten åkerareal och får lägst rang utifrån valda parametrar men har utöver åkermark stora arealer skogsmark och en närliggande grundvattentäkt som väntas bli påverkade vid införande av eventuellt vattenskydd. Föreslagna vattenskyddsområden, kostnader för ersättning vid försvårad markanvändning, och riskklassificering är framtaget utifrån tillgängliga kartunderlag och modeller utan att mätningar har gjorts. Detta resulterar i att resultatet får ses som en vägledning för att belysa problematiken i samband med införande eller utökande av vattenskydd för dessa områden men där hydrogeologiska undersökningar är rekommenderat för vidare utredning. / The County administrative board in Stockholm has produced a water plan for region Stockholm that contains a prioritization for all water resources in the region based on the reservoir's importance for present and future water production. From the resources with highest or high priority a selection has been made of resources that lack or need to update their water protection area. Three groundwater reservoirs and three surface water reservoirs were selected in the region that Norrvatten provides water for. When a water protection area is established or renewed conflicts of interest occur within the surrounding area. By using Arc-GIS an analysis can be made of the competing interests in the area. This is performed by combining layers provided by swedish institutions such as Länsstyrelsen, SGU, Naturvårdsverket and cutting them down to reasonable shapefiles and extract necessary information. This thesis focuses on the conflict of interest with agriculture and identifying and classifying risk objects as roads, railroads, industries and housing areas around the water resources. Agriculture land area is measured and costs are calculated to get a general overview how expensive it will be to compensate landowners that can't use their land due to restrictions in the suggested water protection area. Identifying and risk classifying risk objects has been done forroads, railroads, industrial and housing areas in the suggested waterprotaction area. The analysis shows that the groundwater reservoir at Röåsen-Bergby is the water resource that has the most conflicts of interest of the selected water reservoirs. Röåsen-Bergby has big areas of land used for agriculture, neerby roads with heavy traffic and large urban areas. A combined analysis has been made for groundwater reservoirs Uppsalaåsen-Toresta and Uppsalaåsen-Lindormsnäs. In this area there are big areas of agricultural land close to the reservoirs and also roads, railroads, industry and housing areas that provide an increased risk for pollution. The surface water Fysingen is protected by nearby water protection areas and a nature protection area but is still subject to conflict of interest with large land areas of agriculture and heavily trafficked roads and railroads that provides increased risk for pollution to the lake. The surface water Erken has the highest priority in the regional water plan but has few risk objects except a heavily trafficked road and some housing areas. Based on the initial analysis Largen only had small areas of housing as conflict of intrest. Suggested water protection areas, cost to compensate landowners, and risk classification has been produced with available maps and models without any new measurements. Which means that the result must be looked at as a guidance that shows that problems can occur when establishing or renewing water protection areas. For the selected areas a hydrogeological investigation has to be done to make it possible to draw better conclusions.

Urban runoff is generated by precipitation of rain and snowmelt on impervious surfaces.  The increasing demand of urbanization causes contaminants to accumulate on roads,  roofs and pathways. In turn, as runoff wash off these surfaces, contaminants such as heavy metals, particles and organic pollutants end up in the stormwater. Urban stormwater ponds improve water quality of runoff by facilitating contaminants in form of particles. To preserve the function of a stormwater pond accumulated sediment must periodically be removed.Therefore, upland disposal alternatives should be evaluated. This study examined stormwater sediment and outlet stormwater quality in seven and four ponds respectively in the vicinity of Halmstad. 7 heavy metals and 24 organic contaminants were analysed in both sediments and stormwater. Results showed metal and organic contaminant concentrations in stormwater pond discharge and sediment exceeding concentrations reported in guideline values. From the analysed heavy metals, Zn and Pb was considered the most critical contaminants. Heavier organic compounds were more frequently quantified than lighter ones, where 42 % of the analysed organic contaminants were quantified in at least one sample. Variability between inlets and outlets, between ponds and between sampling occasions was observed. The observed variability suggests that the contamination level is influenced by catchment area characteristics and activities. Significant correlation from Spearman’s rank correlation was found between the individual heavy metals (Cu, Cr, Ni, Pb and Zn), which suggest they originate from similar sources

Wastewater compose an environmental risk as it contains high levels of nutrients, including phosphorus. Wastewater treatment plants (WWTPs) reduce phosphorus by using coagulants that precipitate soluble phosphate into metal phosphate, which is separated by settling. Coagulant flow is regulated by a control strategy, typically feedforward or feedback control. Feedforward is based on incoming wastewater disturbances whereas feedback control uses outgoing process values. Incoming phosphate is hard to measure and can be estimated using soft sensors. Modelling control strategies can help decide which strategy that is most suitable. Models describing phosphorus removal are Activated Sludge Model, ASM2d, and primary clarifier model. ASM2d models phosphorus precipitation and the primary clarifier model settling of particles. Tivoli WWTP faces challenges to reach effluent requirements of phosphorus. The wastewater flows through an equalisation tank, Regnbågen, before being pumped to Tivoli. Particulate matter settles in Regnbågen, which is removed by reducing the water level in Regnbågen. This rapidly increases incoming particulate load to Tivoli.Tivoli’s current control strategy is feedforward proportional to suspended solids. It is suspected, that this strategy overdose coagulant during the emptying of Regnbågen. The purpose of this thesis was to find the optimal control strategy for phosphorus precipitation at Tivoli WWTP, by using a model-based approach. Control strategies modelled are; feedforward, feedback and these two control strategies combined. Additional issues resolved are 1) calibration of a model that predicts the effect of chemical dosage on effluent phosphorus concentration from the primary clarifier, 2) calibrationof a soft sensor, 3) determination of which control strategy that is most suitable. ASM2d and a primary clarifier model were used to create a model describing chemical phosphorus removal. The calibration matches measured phosphate concentration, but underestimate peaks. The primary clarifier model was calibrated by minimising load differences for phosphate and total suspended solids, and was calibrated satisfyingly. A simplified soft sensor was constructed, described by a linear relationship between phosphate and pH. Three disturbances for feedforward control were analysed; measured phosphate, the soft sensors estimation of phosphate and Tivoli’s current controlstrategy. The optimal control strategy was found through a multi-criteria analysis. The optimal control strategy is the combined control strategy, when feedforward is proportional to incoming measured phosphate. The performance of all analysed feedforward disturbances were significantly improved when combined with feedback control. Furthermore, consequential errors are distinct when the soft sensor miss-predictincoming phosphate concentration. If the phosphate concentration cannot be correctly measured/estimated, feedback control alone has the best performance.

Background: Climate change and the consequences of global warming is probably one of the greatest issues of our time. Among other concerns, global warming is thought to have a great impact on hydrology worldwide. When the atmosphere warms up, river runoff patterns are altered. Nevertheless these future changes are assumed to increase the hydropower potential in some countries. In the public debate it is often referred to a nine year old investigation claiming an increase of 15-20 % in Swedish energy production from hydropower due to the river runoff increase. On the other hand recent research is hinting that the effect of global warming might be masked by climate variability in the nearest future. This study seeks to investigate whether or not the hydropower-intensive company Fortum will benefit from increased future hydropower potential due to climate change. Methods: Using historical data, the impacts of global warming on the future potential power production in different types of hydropower plants are estimated by the statistical approach of probability density functions. Moreover spectral analysis is used to investigate the impacts of climate variability in various Swedish watersheds. The study investigates both the nearest future, represented by the years 2021-2050, and the end of the century, represented by the years 2069-2098. Results: The future hydropower production is shown to be strongly dependent on the geographical location of a power plant and of the specific power plant type. Although all Swedish rivers where Fortum operates is given more river runoff in the future, some hydropower plants might  suffer from lower hydropower potential due to increased runoff variability. However all reservoir-type power plants in the study, with ability to store water, are calculated to benefit from increased river runoff. Only the run-of-river type power plants, operating with unregulated river flow, are not yet proven to benefit from a changing climate. When considering both specific river and type of power plant, this study indicates that the hydropower potential in the rivers where Fortum operates is expected to increase with 4-15 % towards the end of the century. The one exception is the unregulated river Västerdalälven where this study indicates a possibility of decreased hydropower potential due to climate change. The results of the spectral analysis indicates that up to 30 % of the coefficient of variation in the  monthly mean runoff data is explained by low-frequent periodic fluctuations due to natural climate variability, linked to somewhat predictable climate indices. Conclusion: Natural climate variability is likely to be the dominating factor in the nearest future, at least in regulated rivers. Although there are uncertainties about the future potential power production in the run-of-river type power plants, one cannot deny that most of the Swedish rivers where the major hydropower companies operate are strongly regulated. Adding the fact that river runoff will increase as a consequence of global warming, Fortum is likely to gain from an increased hydropower potential. However, this present study highlights the inaccuracies in using the out-of-date estimation of 15-20 % hydropower-potential increase as a forecast of future potential power production in all Fortum-operated hydropower plants.

Seawater flue gas desulphurization (SWFGD) is a reliable and efficient process to re-move sulfur dioxide in flue gases in power plants and industries. The characteristics and applications of seawater treatment plant of three SWFGD process are described firstly. A literatual survey looking at different air injection techniques in shallow water basin applications are investigated, also including best practice from similar applications in other types of industries. A number of promising alternatives is then selected and compared with today’s system. The relevant experimental data of these systems are collected. A rate-based model is developed to simulate and optimize the aeration process in seawater treatment plant after its reliability is verified by the experimental data.