Reverse osmosis and nanofiltration opportunities to concentrate multicomponent mixtures of volatile fatty acids

•RO and NF spiral wound membrane modules were assessed for VFAs filtration.•Main process parameters were screened in total recirculation and concentration modes.•Temperature and pH rise lead to higher fluxes and separation factors, respectively.•RO has a potential for carboxylic acids concentration at pH ≥ 5 and 30–45 °C.•Nanofiltration can be employed for carboxylic acid fractionation.