Removal of polar organic micropollutants by mixed-matrix reverse osmosis membranes

Mixed-matrix reverse osmosis (RO) membranes have been proposed to outperform standard polyamide thin-film composite (TFC) membranes for the production of high-quality drinking water. We investigated the passage of 30 persistent polar micropollutants (MPs) in a pilot-scale RO system equipped with a 4-inch zeolite-embedded thin-film nanocomposite (TFN) membrane fed with raw riverbank filtrate. Additionally, MPs passage was investigated in a bench-scale system equipped with a 1.8-inch aquaporin-embedded RO membrane. Benchmark TFC membranes were used in both systems. In pilot-scale RO, MPs passage did not exceed 15% and 6% with the TFC and TFN membranes, respectively. In bench-scale RO, MPs passage values of up to 65% and 44% were quantified for the aquaporin and TFC membranes, respectively, suggesting a more open structure of the 1.8-inch modules. In both RO systems, uncharged polar MPs displayed the highest passage values. While neutral MPs of molecular weight lower than 150 Da were better removed by the TFN membrane in pilot-scale RO and by the TFC membrane in bench-scale RO, no substantial differences between passage values of other MPs were observed. Overall, this indicated that nanocomposite and biomimetic membranes are as effective as TFC membranes of the same module size in preventing breakthrough of polar organics.