Release of persistent and potentially toxic per- and polyfluoroalkyl substances (PFAS) and other halogenated compounds into the aqueous environment is an emerging issue and advanced treatment methods are needed for their removal from contaminated water. Destructive treatment methods for PFAS exist, but there is a risk of incomplete degradation, resulting in creation of transformation products during treatment. This study assessed the potential of electrochemical oxidation (EO) for destruction of PFAS and other halogenated compounds, and their transformation products. Suspect and non-target screening were used to explore the chemical space of these samples and identify compounds present before and after the treatment, including transformation products. In total, 21 PFAS classes and 53 individual PFAS were identified using suspect and non-target screening, with confidence level (CL) 3d or higher. Two new classes of PFAS (FASHN and MeOH-FASA) were discovered for the first time. Suspect screening of PFAS revealed that hydro-substituted and ether PFAS could be formed during EO. A total of 12 chlorinated and two brominated compounds were also detected and confirmed with CL 1–3, with six compounds determined to be transformation products. Formation of ammonium oxidation byproducts was hypothesized as being responsible for most identified transformation products formed during EO.

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Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic contaminants that are present globally in water and are exceptionally difficult to remove during conventional water treatment processes. Here, we demonstrate a practical treatment train that combines foam fractionation to concentrate PFAS from groundwater and landfill leachate, followed by an electrochemical oxidation (EO) step to degrade the PFAS. The study combined an up-scaled experimental approach with thorough characterization strategies, including target analysis, PFAS sum parameters, and toxicity testing. Additionally, the EO kinetics were successfully reproduced by a newly developed coupled numerical model. The mean total PFAS degradation over the designed treatment train reached 50%, with long- and short-chain PFAS degrading up to 86 and 31%, respectively. The treatment resulted in a decrease in the toxic potency of the water, as assessed by transthyretin binding and bacterial bioluminescence bioassays. Moreover, the extractable organofluorine concentration of the water decreased by up to 44%. Together, these findings provide an improved understanding of a promising and practical approach for on-site remediation of PFAS-contaminated water.@en

Foam fractionation has recently attracted attention as a low-cost and environmentally benign treatment technology for water contaminated with per- and polyfluoroalkyl substances (PFAS). However, data on the mass balance over the foam fractionation process are scarce and when available, gaps in the mass balance are often identified. This study verified the high treatment efficiency of a pilot-scale foam fractionation system for removal of PFAS from industrial water contaminated with aqueous film-forming foam. ΣPFAS removal reached up to 84 % and the removal of perfluorooctane sulfonic acid (PFOS) up to 97 %, but the short-chain perfluorobutanoic acid (PFBA) was only removed with a mean efficiency of 1.5 %. In general, mobile short-chain PFAS were removed less efficiently when the perfluorocarbon chain length was below six for carboxylic acids and below five for sulfonic acids. Fluctuations in treatment efficiency due to natural variations in the chemistry of the influent water were minor, confirming the robustness of the technology, but significant positive correlations between PFAS removal and influent metal concentration and conductivity were observed. Over all experiments, the mass balance closure did not differ significantly from 100 %. Nonetheless, PFAS sorption to the walls of the reactor was measured, as well as high PFAS emissions by the air exiting the reactor. PFAS emissions in aerosols correlated positively with mass balance closure. The elevated aerial PFAS concentrations measured in the experimental facility have implications for worker safety and prevention of PFAS-emissions to the atmosphere, and demonstrate the importance of installing appropriate filters on the air outlet of foam fractionation systems.@en

The presence of per- and polyfluoroalkyl substances (PFAS) in the aquatic environment has become a global cause for concern. PFAS are persistent anthropogenic chemicals, and certain PFAS are known to be mobile, bioaccumulative and toxic. PFAS are often found in landfill leachate, effluents from industrial and municipal wastewater treatment plants, and groundwater contaminated with aqueous film-forming foam (AFFF). Conventional wastewater treatment technologies are typically inefficient towards the removal of PFAS. Therefore, this thesis aimed to explore the effectiveness of foam fractionation (FF) and electrochemical oxidation (EO) for PFAS removal and degradation. In FF, PFAS adsorb to rising air bubbles and are separated from the water as a concentrated foam. In this thesis, a continuous pilot-scale FF reactor was optimized for PFAS removal from landfill leachate, reaching ΣPFAS removal efficiencies of 60%. Gaps in the mass balance were identified, so a follow-up study assessed if emissions to air could explain this loss of PFAS. Here, FF could remove up to 84% of ΣPFAS from AFFF-contaminated industrial water. While the measured PFAS emissions to air were high, they did not contribute significantly to the mass balance. EO was tested as a destructive technology for the treatment of fractionated foam produced from groundwater and landfill leachate. Treatment effectiveness was assessed with thorough analysis strategies, including target analysis, PFAS sum parameters and effect-based methods, and a coupled numerical model was developed to describe the PFAS degradation kinetics. While the total degradation was higher with EO only, the energy efficiency of the FF+EO system was higher. Finally, the potential of integrating foam fractionation with existing treatment processes was investigated. Foam was sampled from ten different full-scale water treatment plants, and it was found that the ΣPFAS enrichment relative to the influent reached up to a factor of 105. However, no PFAS removal from influent to effluent was found, possibly because the foam was not actually removed in any of the processes. Altogether, this thesis contributes to an increased understanding of treatment options for PFAS contaminated water, with a particular focus on FF and EO.@en

Foam fractionation is becoming increasingly popular as a treatment technology for water contaminated with per- and polyfluoroalkyl substances (PFAS). At many existing wastewater treatment facilities, particularly in aerated treatment steps, foam formation is frequently observed. This study aimed to investigate if foam fractionation for the removal of PFAS could be integrated with such existing treatment processes. Influent, effluent, water under the foam, and foam were sampled from ten different wastewater treatment facilities where foam formation was observed. These samples were analyzed for the concentration of 29 PFAS, also after the total oxidizable precursor (TOP) assay. Enrichment factors were defined as the PFAS concentration in the foam divided by the PFAS concentration in the influent. Although foam partitioning did not lead to decreased ∑PFAS concentrations from influent to effluent in any of the plants, certain long-chain PFAS were removed with efficiencies up to 76%. Moreover, ∑PFAS enrichment factors in the foam ranged up to 105, and enrichment factors of individual PFAS ranged even up to 106. Moving bed biofilm reactors (MBBRs) were more effective at enriching PFAS in the foam than activated sludge processes. Altogether, these high enrichment factors demonstrate that foam partitioning in existing wastewater treatment plants is a promising option for integrated removal. Promoting foam formation and removing foam from the water surface with skimming devices may improve the removal efficiencies further. These findings have important implications for PFAS removal and sampling strategies at wastewater treatment plants.@en

Per- and polyfluoroalkyl substances (PFAS) are of concern for their ubiquity in the environment combined with their persistent, bioaccumulative, and toxic properties. Landfill leachate is often contaminated with these chemicals, and therefore, the development of cost-efficient water treatment technologies is urgently needed. The present study investigated the applicability of a pilot-scale foam fractionation setup for the removal of PFAS from natural landfill leachate in a novel continuous operating mode. A benchmark batch test was also performed to compare treatment efficiency. The ΣPFAS removal efficiency plateaued around 60% and was shown to decrease for the investigated process variables air flow rate (Qair), collected foam fraction (%foam) and contact time in the column (tc). For individual long-chain PFAS, removal efficiencies above 90% were obtained, whereas the removal for certain short-chain PFAS was low (<30%). Differences in treatment efficiency between enriching mode versus stripping mode as well as between continuous versus batch mode were negligible. Taken together, these findings suggest that continuous foam fractionation is a highly applicable treatment technology for PFAS contaminated water. Coupling the proposed cost- and energy-efficient foam fractionation pretreatment to an energy-intensive degradative technology for the concentrated foam establishes a promising strategy for on-site PFAS remediation.@en

Reversible control over the functionality of biological systems via external triggers may be used in future medicine to reduce the need for invasive procedures. Additionally, externally regulated biomacromolecules are now considered as particularly attractive tools in nanoscience and the design of smart materials, due to their highly programmable nature and complex functionality. Incorporation of photoswitches into biomolecules, such as peptides, antibiotics, and nucleic acids, has generated exciting results in the past few years. Molecular motors offer the potential for new and more precise methods of photoregulation, due to their multistate switching cycle, unidirectionality of rotation, and helicity inversion during the rotational steps. Aided by computational studies, we designed and synthesized a photoswitchable DNA hairpin, in which a molecular motor serves as the bridgehead unit. After it was determined that motor function was not affected by the rigid arms of the linker, solid-phase synthesis was employed to incorporate the motor into an 8-base-pair self-complementary DNA strand. With the photoswitchable bridgehead in place, hairpin formation was unimpaired, while the motor part of this advanced biohybrid system retains excellent photochemical properties. Rotation of the motor generates large changes in structure, and as a consequence the duplex stability of the oligonucleotide could be regulated by UV light irradiation. Additionally, Molecular Dynamics computations were employed to rationalize the observed behavior of the motor-DNA hybrid. The results presented herein establish molecular motors as powerful multistate switches for application in biological environments.

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