(584f) Enhanced Pfas Removal through Synergistic Biofiltration and Nanofiltration Treatment: Role of NOM-Pfas Characteristics

Nanofiltration is a promising technology that has demonstrated success in removing emerging contaminants, such as per- and polyfluoroalkyl substances (PFAS), from source water (around 90%). However, frequent fouling of the membrane by natural organic matter (NOM) and biological components of water reduces the PFAS rejection and permeation. In addition, the interaction between NOM and PFOS might change the physicochemical properties of PFOS such as aggregate size and surface charge that negatively impact the PFOS rejection. Therefore, a pre-treatment process to remove the NOM and biological compounds of feed water contribute significantly in enhancing the PFOS rejection and water permeation while reduces the fouling of membranes. Therefore, this project aims to reduce the fouling of nanofiltration membranes for enhanced PFAS removal through a synergistic treatment process of biofiltration and nanofiltration (NF). We aim to understand the interactions between NOM and PFAS using multiple characterizations like the parallel factor analysis of fluorescence excitation-emission matrices and dynamic light scattering techniques. PFAS removal is quantified using LC-MS/MS and organic matter removal using TOC across the hybrid biofiltration- nanofiltration treatment process and identify the sequential reduction in fouling for enhanced PFAS removal. The different concentrations of humic acid solution (3, 15 and 45 ppm) show an aggregate size of around 200 nm and a negative surface charge of 20 mV. The 2 ppm PFOS solution has a negative surface charge of 5 mV. The mixture of HA and PFOS showed a slight increase in size (250 nm) compared to humic acid but almost twice the surface negative charge (50 mV) as humic acid. The biofiltration shows to remove less of humic-like components, than protein like components in 15 min of Empty bed contact time (EBCT) through biofilter and showed no effect on removing PFOS in water. On the other hand, the NF membrane showed higher humic type component removal than protein-like component. NF membrane without pre-treatment showed 92% PFAS removal and 90% HA removal for a pure PFAS and HA solution as wells as for a mixture of PFOS and HA.