Screening of reverse osmosis membranes for the treatment and reuse of distillery condensates into alcoholic fermentation

Industries including a fermentation step use large volumes of water to dilute their musts. In beet alcohol distilleries, this water is recovered as condensates during stillage concentration. Because of their high organic content, these condensates cannot be discharged without a treatment. The elimination of inhibitory solutes that they contain would enable their recycling into alcoholic fermentation. Reverse osmosis is an interesting process within this framework but membrane behavior with respect to small organic solutes is little known. A pre-selection step was necessary to choose among eight appropriate membranes (ESPA2, LFC3 and CPA2 from Hydranautics, BW30 and BW30LE from Filmtec, SG, SE and CE from Osmonics) the best one for this application. Their efficiency was estimated according to permeate fluxes, fermentation ability and solute concentration measurements, obtained at two pH and volume reduction factors. Permeate fluxes were high (between 35 and 120 L.m−2.h−1). The target solutes were well rejected (between 82.2 and 99.2%) and permeate inhibitory effect was weak (between 0 and 5.2%). According to these three criteria, ESPA2 membrane appeared to be the most efficient, followed by CPA2. Results were linked to membrane manufacturers’ data and showed that the latter were not appropriate to differentiate membranes for this application. Permeabilities were calculated according to the solution-diffusion model and showed that transfer mechanism is different from one molecule to another.