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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Radiosynthesis of Perfluoroalkyl Substances : Chemical analysis, uptake, distribution, and partitioning studies

Sundström, Maria January 2012 (has links)
Perfluoroalkyl substances (PFASs) are widely utilized manmade chemicals. Their properties have made them highly appreciated in a variety of industrial and consumer product applications, including fire-fighting foams, hydraulic fluids, as well as in cookware and food contact papers. However, some of the PFASs are highly persistent in the environment and their toxicological profiles are of concern. Voluntary and regulatory efforts have been taken to reduce the environmental levels of PFASs. These actions have resulted in a reduction of PFASs in human milk from Stockholm as presented in this thesis. The radiosyntheses of 35S-PFOS, 35S-PFBS, and 14C-PFOA presented herein were applied for distribution studies in mice but also for solubility and adhesion experiments of common laboratory solvents and buffers. The radiosynthesis employed reactive Grignard reagents, perfluoroalkyliodides, and 35S-sulfur dioxide or 14C-carbon dioxide. The distribution studies were performed with 35S-PFOS on both pregnant mice and their offspring as well as on male mice. The mice were subjected to whole-body autoradiography and the tissues were analyzed by liquid scintillation counting. Liver and lungs were the target organs for 35S-PFOS in the dams. The fetuses and pups had remarkable high levels of 35S-PFOS in their lungs as well as in the brain. The male mice were given a high dose and a more environmental relevant dose of 35S-PFOS. PFOS was transferred from the blood to the tissues as the dose increased. In another study the distribution pattern of the shorter homologue PFBS was compared to PFOS. 35S-PFBS was utilized and demonstrated a 5-40 fold lower tissue levels in comparison to PFOS. The pharmacokinetic parameters determined for PFHxS in mice, rats, and monkeys will provide valuable insight in establishing a proper risk assessment for this compound. The study confirms the common species differences in serum elimination half-life that are associated with PFASs. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Manuscript.</p>
2

Effects of perfluorinated compounds on hepatic fatty acid oxidation in avian embryos using a tritium release assay

Westman, Ola January 2009 (has links)
The large use of perfluorinated compounds (PFCs) to produce fluoropolymers in consumer and industrial applications, including insecticides, plastics, non-stick surfaces and fire fighting foams has led to a well known widespread occurrence and high concentrations are found in wild life including avian species. For instance, concentrations of perfluorooctane sulfonate (PFOS) in eggs from the common guillemot in the Baltic Sea are among the highest in the Nordic environment. In our laboratory studies, PFOS has caused early mortality in chicken at doses close to concentrations found in eggs of the Baltic guillemot. The mechanisms behind the avian toxicity are unclear but many studies suggest mechanisms including lipid homeostasis. We have designed a method in which hepatic embryonic tissue from chicken (Gallus domesticus) is used to investigate the effects of PFCs on the β-oxidation of fatty acids.  The purpose of this project was to assess the effects of PFOS, perfluorooctanoic acid (PFOA) or perfluorobutane sulfonate (PFBS) on the hepatic fatty acid oxidation using an egg injection technique followed by the use of a tritium release assay with palmitate (16:0) as substrate. The embryos were exposed in ovo and on day 10 of incubation embryo livers are incubated in vitro with tritiated fatty acids. The β-oxidation was significantly induced after exposed to 1 mg/kg PFOS (p = 0.003) and 10 mg/kg PFOS (p = 0.04), and difference in oxidation values was 39% and 34% respectively compared to control. The oxidation effect was not significant (p &gt; 0.05) in samples exposed to PFOA (4 mg/kg) or PFBS (20 mg/kg), however noted, the difference in oxidation values was 18% and 30.5% respectively, compared to control calculated on current average. The results show that in ovo exposure in combination with an in vitro method, using a tritium release assay to detect effects on the β-oxidation of fatty acids in avian embryo hepatic tissue could be a useful method to elucidate possible mechanisms behind avian developmental toxicity.
3

Bränder som aldrig riktigt slocknat : En rumslig undersökning huruvida brandsläckningsinsatser (2001–2015) kan kopplas till förhöjda halter PFAS i ytvatten, fisk och sediment i Stockholm, Solna och Sundbybergs kommuner

Nyholm, Niclas January 2021 (has links)
Poly- och perfluorerade alkylsubstanser (PFAS) är ett paraplybegrepp för tusentals kemikalier som delar starka kol-fluorbindningar (C-F bindningar). C-F bindningen gör ämnena mycket persistenta och har påvisat skadliga effekter hos både människor och miljö. Sedan 1980-talet har PFAS använts i samband med brandsläckning (Aqeuous Film Forming Foam (AFFF)) (Kemikalieinspektionen, 2013, s. 8), på grund av dess filmbildande förmåga och motståndskraft mot höga temperaturer. Användningen av AFFF anses vara den största källan för spridning av PFAS i svensk miljö över tid (Naturvårdsverket, 2016, s. 48). Människor/miljö som befinner sig i anslutning till flyg- eller brandövningsplatser löper störst risk att exponeras av förhöjda halter av PFAS (Naturvårdsverket, 2016, s. 80).  Syftet med denna studie var att identifiera eventuella spatiala samband mellan individuella släckningsinsatser och förhöjda halter i PFAS i ytvatten, sediment och i fiskvävnad (matriser).  Studien har beaktat samtliga släckningsinsatser med skum mellan åren (2001–2015) i tre Stockholms kommuner, där halter av i PFAS har utvärderats i respektive matris. Med hjälp av miljöövervakningsdata och andra centrala dataunderlag har databearbetning i GIS (geografiska informationssystem) möjliggjorts.   Resultaten av metodiken påvisade inga tydliga korrelationer mellan brandsläckningsinsats/brandövningsplats och förhöjda halter PFOS i respektive matris. Däremot kan ett områdes lokala förutsättningar styra viktiga faktorer som bestämmer huruvida punktutsläppet av PFAS från en brandsläckningsinsats/brandövningsplats blir kvar, eller transporteras bort från platsen. Kunskap över de lokala hydrologiska förhållandena kan vara viktigt för att kunna förutsäga hur PFAS har rört sig i yt- och grundvatten samt mark. Detta kan i sin tur leda till bättre motivering av utredning och insats av specifika områden.
4

Environmental Interactions of Phyllosilicates: Microbial Habitation, Respiration, and Organomodified Photoreductive Scaffolding

Kugler, Alex 23 July 2020 (has links)
No description available.
5

Rening av PFOS från lakvatten på Tveta avfallsanläggning / Removal of PFOS from leachate at Tveta waste treatment plant

Säving, Nils January 2018 (has links)
Telge Återvinnings avfallsanläggning Tveta, har gamla deponiområden och verksamhetsytor som genererar lakvatten och processvatten. Lakvattnet pumpas kontinuerligt till Himmerfjärdsverkets reningsverk, Syvab. Himmerfjärdsverket är REVAQ-certifierat sedan 2009 och kraven för certifieringen har nu skärpts. Perfluoroktansulfonat (PFOS) är ett av de ämnen som finns i lakvattnet och gränsvärdet för det har nu sänkts till 15 ng/l i inkommande flöde vilket Telge Återvinning måste förhålla sig till. För att de ska kunna göra det behövde reningsgraden av PFOS vara 90% av dagens halt. Lakvattnet innehöll dessutom en hög halt partiklar vilket behövde behandlas för att uppnå önskad reningsgrad. PFOS är ett stabilt, bioackumulerande ämne som dessutom är toxiskt. På grund av sin stabilitet kan endast ett fåtal reningsmetoder användas för att avskilja ämnet ur vattenlösningar. Målet med den här rapporten har varit att ta fram dessa reningsmetoder och även värdera dess tillämpningsmöjligheter för reningen av lakvattnet på Tveta. Sammanställningen av informationen har skett genom intervjuer och litteraturstudier. De reningsmetoder som kunde uppnå den eftersökta reningsgraden var omvänd osmos, nanofilter, jonbytare, granulerat aktivt kolfilter och pulveriserat aktivt kol. Utav dessa var granulerat aktivt kolfilter mest lämpat för Tveta avfallsanläggnings lakvattensammansättning vilket avgjordes utifrån ett kostnad- och erfarenhetsperspektiv. Utformningen på partikelavskiljningsprocessen kunde inte fastslås utan praktiska undersökningar men flockning av partiklarna kan ses som ett försteg i processen. / The waste treatment plant of Telge Återvinning in Tveta have old landfills which produces leachate and processwater. The leachate is transported with pumps to the water treatment plant Himmerfärdsverket, Syvab. The water treatment plant has a REVAQ-certificate since 2009 and the requirements to keep the certificate have become tougher. Perfluorooctanesulfonate (PFOS) is one of the substances in the produced leachate. The content limit for that substance has now been decreased to 15 ng/l which means that Telge Återvinning must lower their PFOS content in their leachate. To do so they’ll need a PFOS removal efficiency of 90% based on their current content value. The leachate also contains lots of particles which needs to be removed if the desired removal efficiency is to be reached. PFOS is a none-reactive, bio-accumulative, substance which is also toxic. There’s only a few treatment methods that can be used for the removal of this substance in liquid matrixes because of its none-reactive nature. The point of this report has been to highlight these methods and evaluate them based on their possible usage as a treatment method for the leachate at the waste treatment plant. The information for these methods have been gathered through literature studies and interviews. The available methods which were able to achieve the desired removal efficiency were the reverse osmosis and the nanofiltration, the ion exchanger, the granular active carbon filter and powdered active carbon. From these available methods the granular active carbon filter was thought to be the most suited method for treating the leachate. The most suited method was decided based on its operation cost and familiarity with prior PFOS treatment plant. The treatment process for the particle removal couldn’t be fully decided without field studies. Although flocculation was decided to be the primary step in the treatment process.
6

Mass balance of perfluoroalkyl acids in the Baltic Sea

Filipovic, Marko January 2013 (has links)
Perfluoroalkyl acids (PFAAs) are man-made chemicals. Their unique properties make them beneficial for a wide range of industrial and consumer applications, such as constituents in fire fighting foams, hydraulic oils and food packaging materials.PFAAs have shown to be highly persistent in the environment, and the toxicological potential of long chain PFAA homologues is of a concern. International regulation and voluntary actions by the industry have been implemented and led to reduced primary emissions of PFAAs to the environment. However, the concentrations of some PFAAs in e.g. birds from the Baltic Sea are still very high and of ecotoxicological concern. Measures to reduce the PFAA contamination require an understanding of the sources and how the PFAAs are being transported in the environment.In this licentiate thesis a mass balance was assembled for perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorodecanoic acid (PFDA) and perfluorooctane sulfonic acid (PFOS) in the Baltic Sea. A one-box model was used including the input pathways river inflow, atmospheric deposition, wastewater discharges and inflow from the North Sea via the Danish Straits, while the loss processes considered were sediment burial, transformation of the chemicals and outflow to the North Sea via the Danish Straits. Additionally, the inventories of the four target PFAAs in the Baltic Sea were estimated. Both chemical fluxes and inventories were estimated using recently published monitoring data (2005-2010).In order to obtain a detailed perspective on the current knowledge regarding PFAAs in the Baltic Sea, challenges and uncertainties in data selection were discussed for the most dominant input pathways. This included WWTP emissions and calculation of emission factors (EFs), atmospheric deposition and riverine inflow.River inflow and atmospheric deposition were the dominant inputs, while wastewater treatment plant (WWTP) effluents made a minor contribution. The input to the Baltic Sea exceeded the output for all 4 PFAAs, suggesting that inputs were higher during 2005-2010 than during the previous 20 years despite efforts to reduce emissions of PFAAs. Comparing the difference between PFAA input and output with the PFAA inventory, the doubling time for the concentration in the Baltic Sea was estimated to be 8-94 yr for PFHxA, 12-16 yr for PFOA, 3-5 yr for PFDA and 4 yr for PFOS. The surplus of the input can be an effect of retention and delayed release of PFAAs from atmospheric deposition in the soils and groundwater of the watershed.The licentiate thesis contributes to a holistic understanding of the major input and output pathways and inventories of PFAAs in the Baltic Sea. Furthermore, it points out current knowledge gaps in our understanding of sources and fate of PFAAs in the aquatic environment. / <p>At the time of the defence the following papers were unpublished and had a status as follows: Paper 1: Manuscript</p>
7

PFOS i Igelbäcken : kartläggning av potentiella föroreningskällor och förslag till vidare provtagning och åtgärder / PFOS in Igelbäcken : mapping of potential sources and suggestions for further sampling and corrective actions

Petersson, Johanna January 2019 (has links)
Perfluoroktansulfonsyra och dess derivat (PFOS) har hittats i ökande halter i miljön sedan det började produceras under 40-talet. Syftet med denna studie var att studera PFOS-halten i Igelbäcken i Stockholmsområdet genom att samla in och sammanställa tidigare provdata och att kartlägga föroreningskällor i avrinningsområdet. Halterna befanns vara mycket höga. Den högsta uppmätta halten var 120 ng/l och under perioden 2016-2019 var medelhalten i Slottsallén, i närheten av utloppet, 60 gånger högre än MKN (0,65 ng/l) för inlandsytvatten. Halterna ökar framförallt kring brandövningsplatsen vid Barkarby flygfält, men är fortsatt höga därefter, vilket tyder på att ytterligare källor finns längre nedströms. Ökande vattenstånd och -flöde ger ökad spridning i PFOS-halt. Det finns en positiv, måttlig korrelation mellan vattenstånd och PFOS-halt, vilket skulle kunna bero på högre utlakning. Hela bäckens sträckning bör provtas under samma period för att ge en klarare bild av hur spridningen ser ut. / Perfluorooctane sulfonic acid and its derivatives (PFOS) have been found in increasing levels in the environment since the 40's when it was first produced. The objective of this study was to study PFOS in Igelbäcken in the Stockholm area by compiling previous sampled data and to map pollution sources in the catchment area. The PFOS concentrations were found to be very high. The highest level measured was 120 ng/l and during the period 2016-2019 the mean level in Slottsallén, in the vicinity of the outlet, was 60 times higher than EQS (0.65 ng/l) for inland surface water. The concentrations increases especially around the fire drillsite at Barkarby airfield, but are continuously high thereafter, which indicates additional sources further downstream. Increasing water level and water flow increases the spread in PFOS concentration. There is a positive, moderate correlation between water level and PFOS concentration, which could be due to greater leaching. The entire stretch of the stream should be sampled during the same period to allow a clearer picture of the PFOS distribution.
8

Sonochemical Defluorination of Perfluorinated Compounds by Activated Persulfate Ions

Gray, Kevin M 06 July 2018 (has links)
Polyfluorinated compounds (PFCs) are a class of anthropogenic chemicals that have been found in groundwater and wastewater around the world. Perfluoroctane sulfonate (PFOS) and perfluoroctanoic acid (PFOA) are primarily used for industrial surfactants, and aqueous film forming foams (AFFFs). These PFCs and many of their constituents have been found to be carcinogenic to humans and other animals. A simple method for defluorination of these compounds is needed. Advanced oxidation of PFOS, PFHxS, and PFBS-k was carried out using activated sodium persulfate through ultrasonic irradiation with the following condition; [PFC] = 20 millimolar (mM), [Na2S2O8] = 25 mM, pH = 7, and 25°C. Fluoride concentrations were quantified by ion chromatography (IC). In laboratory experiments, batch reactions of PFBS solutions were conducted in purified water at different pH conditions and N2S¬2O8: PFBS molar ratios of 1:1, 2:1, 10:1, and 100:1 respectively. Solution pH was maintained at 7 using HNO3. Of the three compounds, PFHxS had the greatest defluorination (11%) after 120 minutes reaction time. However, PFBS-K had the greatest increase in defluorination (115%) between the control ultrasound (US) experiment and the combination experiment. When Na2S2O8 was increased, the defluorination ratio of PFBS decreased. This decrease was partly attributed to scavenging reactions between SO4¯• and S2O8²¯. These results show a synergism between ultrasonic irradiation and activated sodium persulfate as a form of advanced oxidation. Recommendations for further research into defluorination of PFOS and its constituents by ultrasonic degradation include: the use of high performance liquid chromatograph with accompanying mass spectrometry (HPLC/MS), the use of an ultrasonic probe with alternate frequencies, and the effects of surface tension on defluorination.
9

Nutidsbeskrivning av PFAS i dagvatten för området Frösö Park : Med fokus mot reningsmetoder och hur PFAS-situationen ser ut för framtiden

Johansson, Tore January 2019 (has links)
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.
10

Removal of Perfluorooctane Sulfonate (PFOS) and Related Compounds From Industrial Effluents

Ochoa-Herrera, Valeria Lourdes January 2008 (has links)
Perfluorooctane sulfonate (PFOS) and related perfluoroalkyl surfactants (PFAS) are ubiquitous contaminants of increasing public concern due to their environmental persistence, toxicity, and bioaccumulation. These perfluorinated compounds have been used for more than half a century in a wide variety of industrial and consumer products ranging from stain repellents such as Teflon® to aqueous fire-fighting foams and to grease-proof food packing. The public health and environmental risks posed by PFAS have driven environmental agencies and the industry to restrict their use to specific applications where they cannot be replaced by other chemicals. The sources and pathways of PFOS and its derivatives in the environment are not well understood. Analysis of environmental samples is critical to understand the fate, transport and persistence of these emerging contaminants. Techniques based on fluorine nuclear magnetic resonance (¹⁹F NMR) spectroscopy and high performance liquid chromatography (HPLC) with suppressed conductivity detection were successfully developed to monitor the presence of PFAS in water samples. Chromatographic separation of C₄ to C₈ PFAS surfactants was achieved using a C₁₈ reversed-phase column and a mobile phase consisting of a mixture of boric acid and acetonitrile at mixing ratios ranging from 75:25 to 45:55 (v/v). The combination of these two techniques was very effective for characterization and routine quantification of PFOS and related chemicals. Analytical methods based on ¹⁹F NMR, HPLC-suppressed conductivity detection, and liquid chromatography with tandem mass spectrometry (LC-MS/MS) were employed to characterize commercial PFOS samples. Linear and branched PFOS isomers in a percentage ratio of 75:25 were identified. Municipal wastewater treatment systems are one of the major sources of PFAS emissions into the environment. The presence of PFAS in sewage sludge from two wastewater treatment plants in Tucson, Arizona, was investigated. Sludge samples were washed with acetic acid and extracted with a mixture of acetic acid and methanol. The extract was cleaned and concentrated by means of solid phase extraction. LC-MS/MS operating in the selective ion monitoring (SIM) mode was employed to assess the presence of perfluorosulfonates, perfluorosulfonamides, and perfluorocarboxylates in sewage sludge samples. PFOS was the only perfluoroalkyl chemical detected in municipal sludge samples at a concentration of 77 ± 5 g kg⁻¹ sludge dry weight. Cost-effective treatment techniques for removing PFAS from industrial effluents are needed to minimize discharges of these pollutants. Reductive dehalogenation is widely applied to the degradation of highly chlorinated compounds. Hence, the susceptibility of PFOS and related compounds to biological and chemical reductive dehalogenation was evaluated in batch assays. PFAS were not reductively dehalogenated by different microbial consortia even after periods of incubation exceeding 2 y, confirming the high resistance of these compounds to microbial degradation. The anaerobic biodegradability of PFOS and perfluorobutane sulfonate (PFBS) samples exposed to electrochemical pretreatment with boron-doped diamond film electrodes was also investigated. The oxidation decreased the concentration of PFAS and dissolved organic carbon in solution, confirming the destruction of these compounds. However, the oxidative treatment did not enhance the susceptibility of PFAS to microbial degradation even after extended periods of incubation (> 1 y). In contrast, PFOS was reductively dehalogenated with a biomimetic system based on vitamin B12 as the catalyst and Ti(III) citrate as the reducing agent. The optimal treatments conditions of the reaction were 260 μM vitamin B₁₂, 36 mM Ti(III) citrate, 70°C and solution pH 9.0. Interestingly, branched PFOS isomers were more prone to degradation by vitamin B₁₂ catalysis compared to the linear isomer. Removal of 3 mol Fper mol of technical PFOS and 12 mol F- per mol of branched PFOS isomers was achieved. Defluorination of PFOS was also observed at environmental relevant conditions of 30°C and pH 7.0, albeit at lower degradation rates. Fluoride and carbon dioxide were identified as the major products of the chemical defluorination. Traces of partially fluorinated volatile compounds were also detected in the headspace. The feasibility of removing PFAS compounds from aqueous streams by sorption onto granular activated carbon (GAC), zeolite, and wastewater treatment sludge was examined in batch isotherm experiments. The fluorocarbon chain and the functional group influenced sorption of the anionic surfactants, PFOS adsorbed more strongly to GAC than perfluorooctanoic acid (PFOA) and PFBS. Activated carbon showed the highest affinity for PFOS (Freundlich K(F) values of 36.7 to 60.9) followed by the hydrophobic, high-silica zeolite NaY (Si/Al 80, K(F) of 31.8) and lastly anaerobic sludge (K(F) of 0.95 to 1.85). GAC sorption is a suitable treatment for the removal of anionic perfluoroalkyl surfactants when present at low concentrations. Fluoride has been identified as the major product of the reductive dehalogenation of PFOS and derivatives. Thus, the toxicity of inorganic fluoride towards the main microbial populations responsible for the removal of organic constituents and nutrients in wastewater treatment processes was also studied. Fluoride concentrations ranging from 18 to 43 mg L⁻¹ caused 50% inhibition (IC₅₀) of the activity of propionate- and butyratedegrading microorganisms and of acetate-utilization by methanogens evaluated under mesophilic and thermophilic conditions. All other microbial populations evaluated in this study, i.e., glucose fermenters, aerobic glucose-degrading heterotrophs, denitrifying bacteria, and H₂-utilizing methanogens tolerated fluoride at very high concentrations (> 500 mg L⁻¹). In the same manner, H₂-utilizing methanogens also tolerated PFOS and PFBS at concentrations as high as 200 and 500 mg L⁻¹, respectively.

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