| Summary: | PFAS is a relatively new group of contaminants with unique characteristics, which in the early 21st century was understood being dangerous for both humans and the environment. In 2008, EFSA published a report on guidelines for human intake of PFAS. Target and limit values for ground and surface water around the world has been based on the information in the EFSA report. In the end of 2018, EFSA published a new preliminary report with new target values for PFAS, well below the target values published in 2008. Frösö Park in Östersund, Sweden, is polluted by PFAS from the time that the Swedish Armed Forces were active in the area. While the Swedish Armed Forces exercised their activities at Frösö Park, large amounts of aqueous fire-fighting foams were used, mainly for training purposes. AFFF at that time contained a mixture of many highly fluorinated chemicals known as PFAS, a collective name of more than 4,700 chemicals consisting of carbon-fluorine bonds. PFAS are, more or less, persistent, bioaccumulative and toxic. This study focuses on PFAS11, which Sweden has target and limit values for in respect of ground water and surface water (lake and sea). PFOS is the most common PFAS chemical and the most commonly occurring PFAS chemical at the Frösö Park area. Today, there is a combined urban runoff and waste water network at the Frösö Park area. The internal water conduit system is currently being examined in order to, eventually, disconnect the urban runoff from the waste water network in order to instead release the urban runoff to Storsjön in the immediate area. As the urban runoff has high levels of PFAS, it must be purified before it is discharged to the recipient. High levels of PFAS has been found in the sewage treatment plant. The sewage treatment plant is not able to purify the water from PFAS, which means that the pollution is discharged into Östersund’s drinking water source, Storsjön. The Municipality of Östersund wanted this thesis as the study will include newsworthy information and provide the municipality more knowledge about the PFAS issues in the Frösö Park area. The aim of this thesis is to examine how the urban runoff from the Frösö Park area can be handled to prevent PFAS leaking out in Östersund’s drinking water source, Storsjön. The thesis describes in a comprehensive way how different purification methods work and the function of the different methods based on the conditions that exist in the Frösö Park area. The purification methods for urban runoff are sedimentation methods, biofilters, and how additives with chemicals can affect the purification of urban runoff. After the urban runoff purification, the purification steps focused on PFAS are sorption methods, chemical redox methods, membrane methods and excavation methods. Based on previous reports for the Frösö Park area, existing data has been compiled into maps, figures and diagrams in order to clearly describe the current PFAS situation. The scientific literature presented herein has been selected by specific keywords in databases. The literature has been supplemented with materials provided by the municipality, tips from researchers and personal contact with other industry-related actors. In the purification steps focused on purifying particles, organic materials and metals in urban runoff, a barrier that restricts the flow of water is proposed, tentatively a dam, wetland or lamellar sedimentation, followed by sand filtration. A large advantage with a barrier restricting the flow of water is the possibility to control the water flow to the next purification step. In the purification steps focused on purifying the water from PFAS, purification with activated carbon, nanofiltration, ion exchange method or sonochemical oxidation are proposed. The purification methods are proposed because of the existing knowledge of the methods and the pollution situation for the Frösö Park area. The research for PFAS with new purification methods, target and limit values for humans and the nature as well as future costs for decontamination and health-related costs means that PFAS currently is a priority contaminant taken seriously. Advantages and disadvantages of the purification methods are presented herein, however, the issues with PFAS are very complex and the purification methods work differently depending on the conditions they are exposed to. In this thesis, the most interesting new information regarding PFAS has been compiled to show the current knowledge situation in order to facilitate for relevant actors to continue their work with the PFAS issues in the future.
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