Polar mobile organic compounds (PMOC) are highly polar chemicals and tend to accumulate in short water cycles. Due to their properties, PMOC might be partially eliminated by advanced water treatment technologies. The goal of this study is to investigate the rejection of 22 PMOC (highly mobile and persistent) by reverse osmosis (RO) and nanofiltration (NF) membranes. The impact of transmembrane pressure was evaluated through lab-scale cross-flow constant pressure filtration tests. Among the investigated experimental conditions, PMOC rejection with NF at 8 bars is comparable to values obtained on RO at 15 bars. Negatively charged PMOCs are highly rejected by both RO and NF membranes while guanidine like compounds exhibit higher passage values and are strongly impacted by transmembrane pressure. In order to model the rejection mechanism, the decision tree methodology was employed to link PMOC physicochemical properties to rejection values. Based on lab-scale results, decision trees were computed and emphasized that NF rejection mechanism is governed by electrostatic interaction and sieving effect. In contrast, PMOC rejection on RO membrane strongly depends on the topological polar surface area (TPSA) of PMOC. This study suggests that micropollutants TPSA should be more investigate in order to describe RO removal efficiency. Moreover, it is shown that decision tree is a powerful numerical tool in order to reveal the specific sequence leading to micropollutants removal by RO & NF membranes.

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