Application of ultrafiltration membrane pre-treatment in reverse osmosis-based beer dealcoholization

Beer has been bringing people together for generations but every experience with beer is not always a positive one. A growing awareness about the dangers of alcohol gives rise to a change in people's thinking and behaviour and this is the main reason why low-alcohol beers are particularly popular nowadays. Beer dealcoholization using reverse osmosis (RO) is a technique intervening at the very end of the brewing process. The dealcoholization system is quite compact, the beer can be processed at room temperature and a very low alcohol content can be achieved (less than 0.05 %). Nonetheless this system requires a large amount of water and the membrane is rapidly subject to fouling. The idea of this work is to study a new membrane dealcoholization system which consists in pre-treating the beer using an ultrafiltration (UF) step before sending the permeate to the reverse osmosis step. This pre-treatment step is meant to hinder the fouling phenomenon, enhance the flux and reduce the amount of beer processed in the RO step. The experimental results show an increased flux of 10 to 15 % at the beginning of the filtration when the beer is pre-filtered by UF. This is likely due to decreased concentration polarisation and gel layer resistances. The beer analyses made after the filtration using the Alfa Lava UF spiral-wound membrane showed a very low retention compared to filtration using other commercial UF flat sheet membranes. This suggests that the increase in flux could be even more enhanced with a more suitable membrane. The modelisation work demonstrated the importance of the diafiltration stage in the UF pre-treatment step but this increases the volume to be treated in the RO step. The proposed model with UF pre-treatment is more complex than the current RO system and is not enhanced in terms of water consumption and membrane area requirement. Therefore this new dealcoholization concept does not seem to be beneficial at first sight despite the flux enhancement.