surface filtration in oscillatory shear


Example of filtration of yeast cells
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Size distribution of yeast cell challenge

The size distribution was measured on a Coulter Multisizer and shows all material below 10 microns, with a median size of 5 microns. A very low concentration of material was measured in the permeate, which could be removed by a polishing filter if required.

The combination of VibraFilter and polishing filter ensures complete clarity of the permeate without forming a cake, or secondary membrane, on the main filter - which can remove wanted components from the permeate such as flavour and tastes.


Filtration flux and pressure performance during yeast filtration The filtration started off with just water at a flux rate of 160 l m-2 h-1, followed by yeast addition. Various flux rates up to 1240 l m-2 h-1 were used and under each condition no surface fouling was observed. Hence, the filtration pressure remained constant for the given permeate rate.

At a permeate rate of 1780 l m-2 h-1 fouling did occur, see the increasing transmembrane pressure for this fixed flux rate. However, backflushing at a rate of once every ten seconds maintained the 1780 l m-2 h-1 flux rate at an average transmembrane pressure of only 80 mbar.


Image under microscope of yeast and other cellular debris microfiltered The material filtered included complete yeast cells and debris from the cells and fermentation, which is smaller than the whole yeast cells. See the Coulter Mutisizer data for the full size distribution of all the material present.

The scale bar on the bottom left of the image is 10 microns between the two divisions.

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