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The main purpose of this work was to evaluate the performance of a commercial reverse osmosis (RO) membrane regarding selectivity (rejection) and productivity (permeate flux) of the treatment of quaternary ammonium compounds (QAC) after electro-Fenton (EF) treatment. Pollutants treated after the EF process should be investigated for ecotoxicity, since excess ions and high conductivity are harmful to aquatic and terrestrial biota. The use of the membrane system after EF treatment acts as final polishing since some electro-oxidative treatments leave the sample with high conductivity. In this study, RO was operated with a constant flow of 1 L min −1 and feed pressures of 1 MPa, 2 MPa and 3 MPa to reject ions (sodium and iron) and to decrease the level of toxicity using representative species from different taxonomic groups: freshwater algae ( Pseudokirchneriella subcapitata ), microcrustaceans ( Daphnia similis ) and lettuce seeds ( Lactuca sativa ). Experiments carried out at different pressures showed that increased pressure caused a rise in rejection and permeate flux. At the applied pressure of 3 MPa, after 180 min, conductivity removal efficiency of 83% was obtained, 85% for sodium and 99% for iron at a flow of 13.87 L/h m 2 . In all bioassays, the use of the membrane was efficient to decrease the toxicity by rejecting the ions. The microcrustacean tested was the most sensitive organism, while alga was the most tolerant organism. The germination of lettuce seeds and the relative growth rate of the radicle after the combined EF+RO process was satisfactory. [ABSTRACT FROM AUTHOR]