Rejection of trace organic chemicals by a hollow fibre cellulose triacetate reverse osmosis membrane

The rejection behaviours of 41 trace organic chemicals (TrOCs) by a hollow fibre cellulose triacetate (CTA) reverse osmosis (RO) membrane for potable water reuse were evaluated. Results reported here suggest that the rejection behaviours of TrOCs by the CTA RO membrane are mostly similar to those previously reported for the polyamide (PA) RO membrane. However, in comparison to the PA based RO membrane, hydrophobic interaction plays a greater role while electrostatic interaction is less significant in governing the rejection of TrOCs by the CTA RO membrane. No difference in rejection between positively and negatively charged compounds by the CTA RO membrane could be observed. The rejection of neutral TrOCs by the CTA RO membrane varied significantly from 25% to over 95%. Molecular size (i.e. minimum projection area) was found to be an important factor governing the rejection of neutral TrOCs. Further investigation using N-nitrosamines reveals that in addition to molecular size, hydrophobicity could significantly influence their rejection by the CTA RO membrane, while N-nitrosamine rejection by the PA RO membrane was mostly governed by molecular size. In contrast to the neutral TrOCs, most charged TrOCs selected in this investigation exhibited over 90% rejection, regardless of molecular size.