Novel yeast and oil drop microfiltration equipment

The conventional microfiltration of yeast and oil is problematic due to irreversible fouling on the membrane surface and within the internal pore structure. These problems result in the need for high shear at the membrane surface, entailing higher operating costs, the periodic replacement of the filter and cell or drop damage making filtration more difficult. A new type of filter is commercially available, which is a true surface filter with no internal structure, where each pore forms a direct channel of uniform size from one side of the membrane to the other. These membranes can be used in an oscillating filtration system, which provides a high peak shear directly at the membrane surface. The benefits of this system are high permeate fluxes, low operating pressures, long-life membranes and lower operating costs. Yeast filtration tests have been performed to validate this equipment. The frequency and amplitude of oscillation have been investigated using yeast (deformable) and calcium carbonate (non-deformable) challenge suspensions. Initial tests have shown that a higher shear provides a higher critical flux and a lower operating pressure. However, a higher shear resulted in a lower grade efficiency in the permeate. Simultaneous development work has been performed on the membrane surface coating in order to maintain a high grade efficiency at high shear, and to minimise any biological adhesion. A case will be presented to highlight the significant process benefits obtained by those industries where the microfiltration of biological material is necessary, including beer filtration and oil filtration, where biological material present in seawater easily fouls existing filtration systems.