The basic technology behind membrane filtration involves using a semi-permeable membrane to separate a liquid into two distinct streams.     Pumping this liquid across the surface of the membrane creates a positive trans-membrane pressure that forces any components smaller than the porosity of the membrane to pass through, forming the permeate. Any components larger than the pore size simply cannot pass through, and remain behind in what is called the retentate. The surface of the membrane is kept free of blockages by the force of the liquid flow moving parallel to the membrane surface. Alfa Laval manufactures membranes for use in an extensive range of processes used in the food, beverage, dairy, biotech and pharmaceutical industries. They are available by the metre, as 20x20 cm sheets and for all Alfa Laval plate-and-frame configurations.