Standard filtration uses diatomaceous earth (Kieselguhr) into filter-press and consists in the retention of solid particles (yeast cells, macrocolloids, suspended matter) and solutes responsible for haze. After use the disposal of Kieselguhr (after filtration) are a major difficulty due to their polluting effect. From the health perspective, the used diatomaceous earth is classified as ‘hazardous waste’ before and after filtration. The membrane microfiltration (cross-flow or dynamic) is used to provide an alternative to the conventional technologies. However this operation must satisfy the same economic and qualitative criteria as standard filter-press filtration. The variety of compounds (chemical diversity, wide-size range) to be retained makes this operation one of the most difficult to control.
RVF has been extensively investigated for the clarification of rough beer (lager beer type) and compared with other microfiltration technologies (cross-flow MF onto ceramic and organic membranes of tubular and hollow fiber types).
Rough beer clarification (elimination of yeast cells and suspended matter) was achieved with RVF technology and stainless steeel membranes with ceramic selective layer. It was demonstrated that
- the selected membrane and chosen conditions of filtration may satisfy quality and flux criteria,
- the performances were validated for volume reduction factor VRF > 10 (Fig.1.2),
- yeast cells remain a major contribution to fouling but are not critical during the concentration phase,
- presented performances constitute a significant improvement in comparison with conventional membrane techniques reported in literature and actually applied in brewery industry.