Biological wastewater treatment followed by physicochemical treatment for the removal of fluorinated surfactants

Perfluorinated surfactants (PFS) have become compounds of high concern during the last decade. While “conventional surfactants” are degraded to a great extent in the biological wastewater treatment process, partly or perfluorinated surfactants are not only stable against biodegradation but also against oxidizing agents, they even resist OH-radical attacks. Our objectives were to eliminate the fluorinated surfactants perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) by adsorption, separation or degradation with a balance of precursor compounds and follow-up of degradation products. Therefore, municipal wastewater was spiked with these fluorinated surfactants before membrane bioreactor (MBR) treatment—applying microfiltration membranes—was performed and before permeates were treated using ozone (O₃) or different advanced oxidation treatment (AOP) techniques. O₃ or hydrogen peroxide (H₂O₂), both in combination with UV radiation or in combination with catalysts, was applied. Removal by adsorption or membrane separation as well as degradation were monitored by substance specific determination and identification. High resolution mass spectrometry after high performance liquid chromatography (HPLC/HRMS and -MSⁿ) was used for analysis. Contact to Teflon^® and/or glass during all analytical procedures was avoided.