Removal of per- and polyfluoroalkyl substances from drinking water using ozonation

Per- and polyfluoroalkyl substances (PFASs) are a broad group of man-made chemicals which are persistent, bioaccumulative and toxic. Due to their unique physicochemical properties PFASs are used in various industrial processes and consumer products. Their environmental persistence and ability to undergo long-range transport have made PFASs compounds of concernastheyhavebeenfoundinvariousmatricesallovertheworld. ConcerningPFASsconcentrationsinblood, breastmilkandorgansarecausedbyseveralexposureroutesi.a. contaminated drinking water. Since PFASs are not affected by conventional drinking water treatment techniques, further research on new approaches for water purification is highly needed. In this study several advanced oxidation processes (AOPs) based on ozonation were tested for their efficiency to degrade PFASs in water. Among other an established method based on heterogeneous catalysis was evaluated in pilot scale. Prior all treatment experiments, adsorption of PFASs to the catalyst surface in MilliQ, tap and water with dissolved organic carbon were evaluated. A fit according to the Freundlich adsorption isotherm model was found. Additional investigations on the adsorption velocity showed that most PFASs adsorb within 10min to the catalyst material, whereby the adsorption process is superimposed by equilibrium adjustment processes that occur slower. In the pilot scale trial drinking water was fortified with 18 different PFASs (1000ngL−1). Removal of more than 98% was found for PFASs with seven to eleven perfluorinated carbon atoms independent of the functional group. All spiked compounds were removed significantly. In a subsequent approach, all possible combinations of ozone (0.3unit), catalyst (5g) and persulfate (1:50 mole ratio spike:ammoniumpersulfate) were evaluated in MilliQ water in a 500mL laboratory scale set-up. The following trends could be observed: Results comparable to the pilot scale experiment were obtained for the combination of ozone and catalyst; ozone and persulfate as well as ozone, persulfate and catalyst. Surprisingly, the treatment with ozone only led to a removal of perfluorinated carboxylic acids (PFCAs) and perfluorooctane sulfonamide (FOSA). Thus, it has been sown, that there is potential for an improvement of already applied AOP treatment via ozone and catalyst by a combination with persulfate. Further research is needed to determine the optimal reaction conditions for this new approach

Removal of per- and polyfluoroalkyl substances (PFASs) from tap water using heterogeneously catalyzed ozonation

Drinking water is one of the most important human exposure pathways of per- and polyfluoroalkyl substances (PFASs). As conventional water treatment techniques are unable to remove PFASs efficiently, novel treatment methods for the removal of PFASs in water are urgently needed. In the present study advanced oxidation processes (AOPs) based on heterogeneously catalyzed ozonation were evaluated on laboratory- and pilot-scales for their efficiency in removing PFASs from water. Laboratory-scale ozonation experiments were conducted with different combinations of ozone, a catalyst and persulfate and showed the highest efficiency for the treatment combining all three parameters. The method was further evaluated for the treatment of spiked drinking water on the pilot-scale. The concentrations of all 18 analyzed PFASs decreased significantly within three hours of treatment in the pilot-scale set-up. The perfluorocarbon chain length had a dominant influence on the removal efficiency, where CF 7 − CF 11 PFASs were removed with more than 98% removal efficiency, independent of the functional group, CF 12 − CF 17 PFASs with 64%, and CF 4 − CF 6 with 55% on average. As the evaluated ozonation treatment is already commercially available for large scale applications today, it could easily be applied in existing water treatment trains; however, ozonation can create potentially toxic transformation products which needs to be investigated in future research