One of the key advantages of membrane technology is that the membranes will remove essentially; all the bacteria, coagulated protein, yeast, algae, moulds, spores and viral material in the raw beer (ranging from tens of microns to sub micron). The process does not adversely affect the product flavour, clarity or head retention. At the same time, the beer will retain those components which characterise a particular product — flavour, colour, brightness and mouth-feel. These results are achievable without the use of additives.
Membrane technology also offers a further advantage in that spent additive disposal costs are eliminated. The concentrate produced by the membrane separation process can be disposed off to animal feed. Membrane separations are generally pressure processes. With microfiltration, ultrafiltration and nanofiltration, the pressure is used to force the liquid stream through pores in a synthetic membrane and the three categories differ in the size of the pores, which are usually asymmetrical to minimise fouling or plugging. Reverse osmosis relies on the use of a semi-permeable membrane. By applying a pressure to the concentrated solution greater than the osmotic pressure difference, pure water molecules can diffuse through the membrane, leaving any salts or dissolved solids behind in the concentrate.
The overall performance of a membrane system is determined by membrane selectivity and permeate flux, which is dependent upon the operating pressure, temperature, pH, pore size, feed composition and flow rate. Typical values of permeate flux may lie within the range 20-2000 l/m2/hr.