Som en följd av global uppvärmning blir det allt viktigare med resiliens mot klimatkrisens konsekvenser, däribland mer frekventa skogsbränder. Då våtmarker kan behålla vatten och ge resiliens mot torka och bränder är det intressant att undersöka relationen mellan våtmarker och skogsbränder. Syftet med detta arbete är att undersöka våtmarkers påverkan på skogsbränder i boreala skogsmiljöer, där frågeställningarna berör antändningsrisk, intensitet, brandskador, areell spridning och utdikning. Arbetet genomförs som litteraturstudie och GIS-analys med fokus på brandspridning. I GIS genomfördes först en multikriterieanalys och sedan en modellering av brandförlopp, i två områden i Hälsingland. Enligt analys och tolkning av resultat är fuktighet, grundvattennivå, vegetation, ytstruktur och storlek de viktigaste faktorerna i våtmarkers relation till skogsbränder. Sannolikhet för antändning, brandintensitet och brandskador minskar alla med ökad fuktighet, ökad grundvattennivå, gott om vitmossa och mindre av annan vegetation. Dessa faktorer gör även våtmarker till bättre brandbarriärer, speciellt i kombination med ökad storlek och heterogen ytstruktur. I motsats är våtmarker med lägre fuktighet och grundvattennivå, större bränsletillgång och träd sämre som barriärer mot skogsbrand och upplever intensivare bränder. Under extrem torka riskerar dock alla våtmarker, i olika utsträckning, att torka ut till den grad att bränder sprider sig över dem.GIS-analysen visar en koppling mellan sankmarker och områden med långsam brandspridning under normala förhållanden, och en stor lokal variation i förutsättningarna för brandspridning. Utdikning av våtmarker försämrar våtmarkernas resiliens mot skogsbränder, och skapar en risk för torvbränder, med allvarliga konsekvenser. En återvätning av utdikade våtmarker skulle förbättra deras brandresiliens. / As a result of global warming, it is ever more important with resilience towards the consequences of the climate crisis, including more frequent wildfires. Since wetlands can retain water and give resilience towards drought and fires, it is interesting to explore the relation between wetlands and wildfires. This study aims to research the influence of wetlands on wildfires in boreal forest environments, with research questions regarding risk of ignition, fire intensity, fire damage severity, areal spread and wetland drainage. The work consists of a literature review and GIS analysis focusing on fire spread. The GIS analysis is done through a multi-criteria analysis and afterwards a modeling of fire development, in two areas in Hälsingland, Sweden. According to analysis and interpretation of the result, the most important factors in the relation between wetlands and wildfires are moisture, water table level, vegetation, surface structure and wetland size. Probability of ignition, fire intensity and fire damage are all reduced with increased moisture, higher water table, plenty of sphagnum moss and less other vegetation. These factors also improve wetland efficiency as barriers against fire, especially in combination with increased size and a heterogeneous surface structure. On the contrary, wetlands with a lower moisture level and water table, larger fuel availability and trees function less efficiently as fire barriers and experience more intense fires. During extreme drought, however, all wetlands to a different extent risk drying out to the point where fire can spread over them. The GIS analysis displays a connection between fens and areas with slow fire propagation under normal conditions, as well as a large local variation in the factors influencing wildfire propagation. Wetland drainage deteriorates wetland resilience against wildfires, and creates a risk of peat fires, with severe consequences. Rewetting of drained wetlands would improve their fire resilience.

New possibilities of nutrients removal by additions of magnesium compounds were studied in primary treatment and supernatant of side stream in wastewater treatment. The precipitation product from this method is magnesium ammonium phosphate (MAP) socalled struvite. High efficiencies on NH4-N and PO4-P removals have been demonstrated up to over 90 % respectively in side stream from dewatering of digested sludge. In order to find out the nutrient removal efficiency in raw wastewater and the feasibility of MAP recycling in wastewater treatment, the postulations of combining MAP and nitrification-denitrification process, and MAP and partial nitritation-anmmox process were carried out by experimental works in the laboratory at Land and Water Resources Department, KTH. It was found that 92-97 % of PO4-P and 57 % of NH4-N were removed from raw wastewater by Mg2+ addition at pH10 to pH10.5. The research work revealed that recycling of MAP by nitrification-denitrification and partial nitritation-anmmox processes may be a feasibly process combination. In MAP and nitrification -denitrification process, the released ammonium was mostly oxidized to nitrate in nitrification phase and ready for denitrification. Based on presented results on MAP and partial nitritation-anmmox process, it was found that the released ammonium was consumed by anammox bacteria.

Land use/cover has shown significant changes during the past three decades in Ethiopia especially in the highlands of the country. That resulted in changes in streamflows and other hydrological processes. The existing land and water resources system of the area is adversely affected due the rapid growth of population, deforestation, surface erosion and sediment transport. The main objective of this study is to evaluate the impact of land use/cover changes in the hydrology of Beles Basin, Ethiopia. The physically based hydrologic model, SWAT, was developed for the Beles basin, Ethiopia by combining geospatial and climatic data. ArcGIS has been used to process geospatial data which includes the Digital Elevation Model (DEM) which has a resolution of 90 m, land use/cover and soil maps. A simple Interpolation technique has been used to fill in the missing precipitation data. The GIS interface version of SWAT (ArcSWAT) has the capability to utilize ArcGIS to facilitate input data preparation and output data generation. Idrisi Andes in cooperation with ArcGIS 9.2 used to generate landuse/cover maps from Landsat data of three different years. Three SWAT models were set up using the three generated land use/cover maps and used to evaluate the land use/cover change and its impacts on the streamflow of study basin. The primary hydrological model was evaluated through sensitivity analysis, model calibration, and model validation for realistic prediction of the different hydrological components in the basin. Out of twenty six flow parameters sixteen parameters were found to be sensitive. But the most sensitive ten parameters were selected and used for model calibration. The model calibration was carried out using observed streamflow data from 01 January 2001 to 31 December 2002 and a validation period from 01 January 2003 to 31 December 2004. The coefficient of determinations (R2) was 0.74 and the Nash-Sutcliffe simulation efficiency (NSE) was 0.62which indicated that the model was able to predict streamflow with reasonable accuracy. However, the hydrograph of the cumulative hydrographs of the calibration and validation periods showed significant discrepancies between the observed and the simulated data of each period.  The average yearly flow volume of the observed streamflow on the cumulative hydrograph of the calibration period has exceeded the simulated streamflow. On the other hand on the cumulative hydrograph of the validation period the average yearly flow volume of the simulated streamflow was higher than the observed streamflow. The simulated result of the streamflow data from different land use/cover maps revealed that the change in the land use/cover classes of the basin throughout the study periods.

Dricksvatten är en grundsten till ett välmående samhälle. Kvaliteten på dricksvatten påverkas av vilken typ av råvattenkällor som används samt hur dricksvattenberedning utförs i ett vattenverk. Om kvaliteten försämras kan det tyda på att dricksvattenberedning inte är optimal eller att kvaliteten i råvattenkällor har förändrats. Sandvikens kommun har haft återkommande problem med bruna och svarta missfärgningar på dricksvatten. Bruna och svarta missfärgningar kan orsakas av järn och mangan som oxideras i distributionsnätet. Vid oxidation av mangan bildas mangandioxid som kan påskynda korrosion. Livsmedelsverket har satt ett gränsvärde för järn och mangan i dricksvatten för att motverka bildande av fällningar i distributionsnätet. Syftet med examensarbetet är att undersöka om missfärgningarna kan bero på höga järn- och manganhalter i dricksvattnet som produceras vid Rökebo vattenverk i Sandvikens kommun. Examensarbetet utfördes med vattenprovtagning samt praktiska studier som involverade analyser av mangan, järn och mangandioxid i dricksvatten från användare samt statistiska analyser. Den statistiska analysen av mangan visade att manganhalter var som högst närmast Rökebo vattenverk. Inga andra statistiska samband har fastställts. Analysen av mangan visade att 20 av 31 vattenprover låg över gränsvärdet för dricksvatten. Gränsvärdet för mangan överskreds redan vid Rökebo vattenverk. För järn låg 2 av 24 vattenprover över gränsvärdet. Analysen av mangandioxid visade förekomst av manganoxiderande mikroorganismer i Sandvikens distributionsnät. Manganet som skickas ut från Rökebo vattenverk kan gynna mikroorganismer och kan öka bildning av mangandioxid som verkar korrosivt på gjutjärnsrör, därmed kan Rökebo vattenverks sammansättning på dricksvattnet påverka eller påskynda korrosion på distributionsnätet. Teoretiskt sätt kan vattenmissfärgningar som har upplevts i Sandvikenskommun bero på de höga manganhalterna. Det går dock inte att utesluta att missfärgningar kan bero på andra faktorer då resultatet inte gav något statistiskt samband mellan missfärgning och järn- och manganhalt. Ytterligare studier krävs för att fastställa alla orsaker bakom missfärgat dricksvatten i Sandvikens kommun. Problematiken med höga manganhalter bör lösas oavsett om det är den främsta orsaken bakom vattenmissfärgning eller inte. Manganhalterna är höga i nuläget och både järn samt mangan kommer troligtvis att öka i råvatten på grund av klimatförändringar. Om vattenverket fortsättningsvis blandar yt- och grundvatten kan problematiken lösas genom att installera en statisk mixer samt införa ett avskiljningssteg för järn och mangan. Vid val av en biologisk avskiljningsmetod kan mikroorganismer från distributionsnätet användas. / Drinking water is a cornerstone to a prosperous society. The quality of drinking water is affected by the type of raw-water sources and how drinking water treatment is carried out in a drinking water treatment plant. If the quality of the drinking water deteriorates, it may indicate that the drinking water treatment is not optimal or that the quality of raw-water sources has changed.The municipality of Sandviken in Sweden has had recurring problems with brown and black discolorations of the drinking water. Brown and black discolorations can be caused by oxidation of iron and manganese in the drinking water distribution system. The oxidation of manganese leads to the formation of manganese dioxide that can accelerate the corrosion processes of cast iron pipes. The Swedish Food Agency has set a limit value for the concentration of iron and manganese in drinking water to prevent the formation of precipitates in the drinking water distribution system. The aim of the study is to investigate whether the discolorations are due to high levels of iron and manganese in the drinking water. Water samples were collected to practically and statistically analyse the concentrations of iron, manganese and the formation of manganese dioxide. The statistical analysis showed that the levels of manganese were at their highest closest to the drinking water treatment plant. No other statistical correlations have been established. The analysis of manganese showed that 20 out of 31 water samples were above the limit value. The limit value for manganese was already exceeded at the drinking water treatment plant. The analysis of iron showed that 2 out of 24 water samples were above the limit value. Results also showed the presence of manganese-oxidizing microorganisms in the drinking water distribution system. Manganese is emitted from the drinking water plant and favors microorganisms as well as increases the formation of manganese dioxide, which may cause corrosion on cast iron pipes. Thus, the composition of the drinking water can affect or accelerate corrosion in the drinking water distribution system.Theoretically, the discolorations that have been experienced by the users may be due to a high concentration of manganese. However, it cannot be excluded that discolorations may be caused by other factors as the result did not provide a statistical relationship between discoloration and the concentration of iron and manganese. Further studies are required to determine all the causes behind discoloured drinking water. The problem of the concentrations of manganese should be solved, whether or not it is the main cause of the water discoloration. The concentrations of iron and manganese are likely to increase in the raw water due to climate change. If the drinking water plant continues to mix surface and groundwater, the problem can be solved by installing a static mixer and introducing a separation step for iron and manganese. When choosing a biological separation method, microorganisms from the drinking water distribution system can be used.

When a tunnel is built in rock, a type of water is formed as a residual product. This tunnel wateris formed due to construction processes such as drilling requiring water and groundwater thatinfiltrates into the tunnel. The water can cause environmental damage if it is released directlyinto nature and needs to be treated. Usually, therefore, the water is purified regardingconcentrations of suspended matter, oil, metals, nitrogen and basic pH values. In this degree project water analysis data, after a local purification in the tunnel area, has beenobtained from 17 different tunnel projects and processed to look into the water quality in theseprojects. The parameters from the analysis data processed are the concentrations of nitrogen,arsenic, lead, cadmium, chromium, mercury, nickel, zinc, chloride, and suspended matter aswell as pH value and conductivity. The results show a large variation in the average valuesbetween the projects and also that a flocculation step in the purification lowers the averageconcentrations for most metals. An analysis of the suitability of using tunnel water for irrigation and fertilization purposes hasalso been carried out by examining the differences in the characteristics of tunnel watercompared to irrigation and fertilizer sources. The result shows that the average concentrationsof the metals chromium and nickel exceed the average concentrations found in groundwaterand surface water in several projects. This means that the tunnel water with respect to thesetwo metals differs from natural sources of irrigation water. According to FAO's guidelines forirrigation water, the average chloride content and average conductivity of the tunnel water isalso elevated and means that the use of the water for irrigation may need to be partly limited.However, this influence needs to be investigated more for Swedish conditions / När en tunnel byggs i berg uppkommer länshållningsvatten, vilket är en restprodukt som måsteomhändertas. Länshållningsvattnet bildas med anledning av att processer som exempelvisborrning kräver vatten samt att grundvatten tränger in i tunneln. Länshållningsvattnet behöverrenas då det kan påverka miljön negativt om det släpps ut direkt i naturen. Vanligtvis renasdärför vattnet med avseende på suspenderat material, olja, metallhalter, basiska pH-värden ochkvävehalter. I arbetet har vattenanalysdata, efter en lokal rening i tunnelområdet, inhämtats från 17 olikatunnelprojekt och bearbetats för att utreda vattnets innehåll i dessa projekt. De parametrarfrån analysdatan som behandlats är koncentrationerna av kväve, arsenik, bly, kadmium, krom,kvicksilver, nickel, zink, klorid och suspenderat material samt pH-värde och konduktivitet. Iresultatet ses en stor variation i medelvärdena mellan projekten och även att ett flockningssteg ireningen sänker medelhalterna för de flesta metaller. En utredning av lämpligheten att använda länshållningsvatten i bevattnings- och gödslingssyftehar också utförts. Detta gjordes genom att klargöra vilka skillnader som finns i halterna avmetaller, kväve och klorid samt i pH-värdet och konduktiviteten hos länshållningsvatten, jämförtmed befintliga bevattnings- och gödselkällor. Resultatet visar att medelhalterna av metallernakrom och nickel överskrider medelhalterna som finns i grundvatten och ytvatten i flera projekt.Detta innebär att länshållningsvattnet med avseende på dessa två metaller skiljer sig från naturligakällor av bevattningsvatten. Enligt FAO:s riktvärden för bevattningsvatten är länshållningsvattnetsmedelkloridhalt och medelkonduktivitet dessutom förhöjd och innebär att användningen avvattnet till bevattning kan behöva begränsas. Denna påverkan behöver dock utredas mer försvenska förhållanden.

Changes in precipitation patterns, temperature, and other climatic variables have been shown to modify thehydrological cycle and hydrological systems, potentially resulting in a shift in river runoff behavior and an increasedrisk of floods. There have been several instances of devastating floods throughout Europe’s history, which haveresulted in devastation and enormous economic losses. As a result of the effects of climate change, floods areoccurring more frequently in Sweden as well as across Europe. Research on the subject of flood prediction has beengoing on for decades, where particularly data-driven models have advanced in recent years. This study examinedtwo different machine learning (data-driven) models for forecasting river discharge in the Nissan River: Linearregression and Random Forrest regression (RFR), with the use of ECMWF Reanalysis v5 ( ERA5 ) data and historicaldischarge data. The Linear regression model yielded a r2 score of 0.45 and could not be considered an acceptablemodel. The RFR model had a r2 score of 0.71. This implies, given ERA5 reanalysis data, that one might generatea moderately performing machine learning model for Nissan river. An additional investigation was carried out,to see if the trained model could be used with EC-EARTH CMIP6 future projection. The findings resulting fromapplying the EC-EARTH CMIP6 future data on the trained RFR indicated too many uncertainties, necessitatingmore investigation before any conclusions can be drawn.

The impact of climate change on drinking water is one of the fastest-growing challenges within the water sector. Microbial contamination of drinking water has been a serious issue for decades now and will exacerbate in the coming future. Until recently the impact of climate change was only evaluated qualitatively and there has been a growing need for a quantitative risk assessment. This review covers different ways of incorporating the effects of climate change into the risk assessment framework. A comprehensive search through two databases was conducted resulting in 596 citations being screened for relevance, of which 23 were confirmed as relevant. Ten risk assessment frameworks and 3 tools obtained from this review were used for the comparative study with the Swedish QMRA tool. Data from multiple frameworks and tools were extracted to identify potential additions required for the improvement of the Swedish tool. Two approaches, i.e. data-driven and process-based, were identified and the foundation for a new framework was set up. Two pathways to implement these approaches were laid out with the first being the addition of new modules to the existing tool and the second being the use of hydrodynamic and water quality models to predict the impact of climate change on infection risks.

The increasing frequency of Cyanobacterial blooms in freshwater bodies raise concerns around the globe. The consequences of this phenomenon impact not only human health but the entire surrounding ecosystem. During the past decades, numerical modelling has been increasingly used to investigate and study aquatic systems. Hydrodynamic and Ecological models are developed in parallel to simulate processes, evaluate potential remedies, and investigate future scenarios. This project aimed at developing a 3D hydrodynamic and water quality (ecological) model to assess the eutrophication conditions of Lake Vomb under current and future scenarios. MIKE 3 FM software was used in the analysis with meteorological, hydrological, and water quality data. The hydrodynamic model performance was satisfactory in terms of water temperature simulation with root-mean-square-error (RMSE) ranging between 0.38-1.2 oC. In the ecological model, Chlorophyll-a (Chl-a) was simulated as a surrogate for Cyanobacteria. The model was adequate in simulating Chl-a concentrations with a Nash-Sutcliffe efficiency (NSE) of 0.94 during calibration and 0.84 after validation. The results showed that Lake Vomb’s nutrient concentrations are highly influenced by external nitrogen loading and internal phosphorus loading. The results also showed that Chl-a levels are correlated with the total phosphorus levels in the lake. Future water quality projections were attempted through two Representative Concentration Pathways (RCPs) for the year 2050. The projections utilized only changes in air temperatures and precipitations and suggested significant increase in Cyanobacteria biomass independence of changes in external nutrient loading.

Per and polyfluoroalkyl substances (PFAS) are found ubiquitously in the environment across the globe.These substances have high persistence due to the strong carbon and fluorine bond. In the aquaticenvironment, due to high persistence, these substances don’t decay easily and are detected on the surfaceas well as in groundwater sources. Human exposure to PFAS has been observed due to ingestion of PFAScontaminated food and water which has an adverse effect on the human health. High concentrations ofPerfluoroalkyl Octanoic Sulphonate (PFOS) and Perfluoroalkyl Hexanoic Sulphonate (PFHxS) wereobserved in Lake Ekoln. The main aim of this study was to analyze the spread of PFOS and PFHxS in thelake. Hydrodynamic modelling of flow and water quality modelling in the lake was performed usingMIKE 3 FM software for the evaluation of the spread pattern of PFOS and PFHxS in the lake. Twoscenarios with the different mass fluxes of PFOS and PFHxS for Fyrisån were assumed for investigatingthe uncertainties and influence of contribution from Fyrisån. Additionally, conductivity from differentinflows was modelled as a passive tracer for understanding the water quality and the circulation in thelake. The results of the simulation showed that Fyrisån and Kungsängsverket are major contributors of PFOSand PFHxS to the lake. Similarly, the analysis of the current spread of PFOS and PFHxS shows that theuncertainty in the model is high and is dependent mainly on the assumption of mass flux from theFyrisån. Due to the lack of sampling data on the concentration of PFOS and PFHxS, it was difficult to geta reliable assumption for the mass flux from the Fyrisån. From the study, it was identified that thesampled concentration of PFOS and PFHxS also had certain variations which might be due to theinfluence of concentration from different sources and processes. Likewise, the simulation result of PFOSand PFHxS was observed to have a similar pattern of spread. Although PFOS is a long-chain PFAS andPFHxS is a short-chain PFAS and they have different physio-chemical properties, the spread patternswere observed to be similar. As only the hydrodynamic processes were influencing the simulation for thespread of PFOS and PFHxS in the lake and other physiochemical processes such as sedimentation andbioaccumulation were not included in the model, the simulated PFAS results were found similar. To conclude, the study shows that the spread of PFOS and PFHxS is mainly influenced by the flow andconcentration in Fyrisån. Also, higher uncertainty in the model performance was observed due to theissue of reliable mass flux estimation from Fyrisån. Similarly, the influence of processes such assedimentation and bio accumulation are necessary to be included in the model for analysis of spread ofPFAS with different physio-chemical properties.

Sveriges miljömål och FN:s globala miljömål pekar båda på att en god vattenkvalité samt ett hållbart uttag av sötvatten är önskvärt. När allt fler människor flyttar ut permanent till skärgården så ökar också uttaget av grundvatten, speciellt under sommarhalvåret då även sommargäster är på besök. Runmarö är en ö i Värmdö skärgård, där det i nuläget endast finns enskilda brunnar och avlopp. Runmarö är mer beroende av sitt grundvatten än fastlandet och om en grundvattenbrist uppstår drabbas de med enskilda brunnar hårdast.  Ett alternativ till grundvattnet är eventuellt ytvatten från någon av öns insjöar. Den största sjön är belägen på södra delen av ön och heter Viträsket. Det är mer lämpligt att använda sjövatten under sommarhalvåret, då vattenledningarna blir negativt påverkade av frost under vinterhalvåret. I denna studie undersöks det huruvida sjövatten kan användas som vattentäkt på Runmarö samt om sjön Viträsket är lämpligt som vattentäkt. För att använda sjövatten på ön så är det en förutsättning att de boende ingår i en gemensamhetsanläggning.  Genom litteraturstudier bildades en uppfattning kring de rådande förutsättningarna på ön samt vad som kunde studeras vidare på. En fältstudie utfördes där boende på ön intervjuades kring den rådande vattensituationen på Runmarö samt deras tankar kring sjövatten och gemensamt VA. Hos de intervjuade togs även vattenprover på dricksvattnet från vattenkranen. Ett vattenprov togs också från sjön Viträsket för att få en uppfattning kring dess vattenkvalité. Bo Olofsson och Erni Bergenstråhle bistod med befintlig brunnsdata från tidigare provtagningar från några av öns brunnar. Under fältstudien intervjuades även Bergenstråhle kring om det är rimligt med en omställning från enskilda brunnar till sjövatten på ön.  Om de vattenprover som samlades in från Viträsket och vattenkranarna hade en högre halt av ett ämne, än vad Livsmedelsverket rekommenderar, så anses det tjänligt men med anmärkning. Av de provresultat som erhölls var endast två stycken tjänliga, övriga var tjänliga med anmärkning, där även Viträsket är inkluderat på grund av dess höga halt av odlingsbara mikroorganismer. Dessa mikroorganismer är ej lämpliga att konsumera under en längre tid.  Utifrån de intervjuer som genomförts verkar de boende öppna för att ansluta sig till en gemensamhetsanläggning, dock ser de gärna att någon annan driver frågan. Ett alternativ kan vara Runmarös intresseförening som dels har hand om infrastrukturfrågor på ön. Sjövattnet från Viträsket skulle kunna användas till funktioner som tvättmaskin, diskmaskin, dusch och toalett samt bevattning utan att renas. För att användas som dricksvatten måste det renas och kylas ner, annars kan det påverka individens hälsa negativt. Ur ett tekniskt perspektiv är det mer rimligt att de boende runtomkring Viträsket använder dess vatten. Vidare är det även viktigt att se över hur vattenledningar från sjön påverkar djur och natur i området. Det behövs dessutom räknas på hur många hushåll som Viträsket kan förse med vatten. / According to the UN and Sweden’s environmental objectives it is important to attain a high water quality and a sustainable use of freshwater. More and more people are currently moving out to the archipelago, which increases the use of freshwater on the islands, especially during summer when guests tend to visit as well. Runmarö is an island in Värmdö archipelago where the residents currently only have individual wells and sewage systems. Runmarö is more vulnerable to disruption of the freshwater, compared to the mainland, and if a groundwater shortage were to happen during the summer, it would be a big concern.  Using the surface water from one of the island’s lakes could be an alternative to the use of water. The largest lake on the island is named Viträsket and is located on the southern part of Runmarö. Since cold temperatures might affect the water pipes negatively, it is more appropriate to use the seawater from the lake during the summer. In this report it is examined whether seawater can be used as a water supply on Runmarö and if Viträsket is an appropriate water source. For the seawater to be used on the island, the residents will have to form a community facility.  Literature studies were conducted to understand the prerequisites on the island and what further investigations could be carried out in this report. A field study was also carried out on the island where residents were interviewed about Runmarö’s current water situation and their thoughts about seawater and community facilities. The tap water was also tested at the interviewee’s homes. A test from Viträsket was collected as well to get a grip of its water quality. Bo Olofsson and Erni Bergenstråhle contributed with existing data of different wells on Runmarö. During the field study, Bergenstråhle was also interviewed about whether it is reasonable to use community facilities and seawater on Runmarö.  If the water samples collected from Viträsket and the water taps has a higher percentage than Livsmedelsverket recommends for a certain substance, it could be possible to drink the water, but one should be observant. Only two of the tap water tests had a percentage lower than Livsmedelsverket’s limits. The other tests had at least one substance that exceeded the limit. Lake Viträsket had a high percentage of culturable microbes that exceeded Livsmedelsverket’s limit. These microbes are not suitable to consume over a longer period of time.  The interviewed residents were all open to join a community facility, they do however prefer it if someone else brings up the question and organizes the start of the process. Runmarö’s interest group handles the infrastructure issue on the island among other things. They might therefore be able to organize the process of creating and building a community facility. The seawater from Viträsket can be used for things such as the laundry machine, dishwasher, shower, toilet and irrigation without further cleaning. To be used as drinking water, it needs to be cleaned and cooled down, otherwise it might affect a person’s health negatively. From a technical point of view, it is more reasonable for the residents living close to Viträsket to use the seawater from Viträsket. Also, it is important to investigate how the water pipes would affect the wildlife around Viträsket. Furthermore, calculations on how much water Viträsket can supply and how many households that can use Viträsket as a source of water needs to be conducted.