Membrane filtration is a separation process which separates a liquid into two streams by means of a semi-permeable membrane. The two streams are referred to as retentate and permeate. By using membranes with different pore sizes, it is possible to separate specific components of e.g. milk and whey. Depending on the application in question, the specified components are either concentrated or removed/reduced. Membrane filtration can basically be divided into 4 main technologies:
Microfiltration (MF)
Microfiltration is a low pressure driven membrane filtration process, which is based on a membrane with an open structure allowing dissolved components to pass while most non-dissolved components are rejected by the membrane. In the dairy industry, microfiltration is widely used for bacteria reduction and fat removal in milk and whey as well as for protein standardisation - especially of cheese milk.
Ultrafiltration (UF)
Ultrafiltration is a medium pressure driven membrane filtration process. Ultrafiltration is based on a membrane with a medium-open structure allowing most dissolved components and some non-dissolved components to pass, while larger components are rejected by the membrane. In the dairy industry, ultrafiltration is used for a wide range of applications such as protein standardisation of cheese milk, powders, fresh cheese production, protein concentration and decalcification of permeates as well as lactose reduction of milk.
Nanofiltration (NF)
Nanofiltration is a medium to high pressure driven membrane filtration process. Generally speaking, nanofiltration is another type of reverse osmosis where the membrane has a slightly more open structure allowing monovalent ions to pass the membrane. Most divalent ions are rejected by the membrane. In the dairy industry, nanofiltration is mainly used for special applications such as partial demineralisation of whey, lactose-free milk or volume reduction of whey.
Reverse Osmosis (RO)
Reverse Osmosis is a high pressure driven membrane filtration process which is based on a very dense membrane. In principle, only water passes through the membrane layer.
In the dairy industry, reverse osmosis is normally used for concentration or volume reduction of milk and whey, milk solids recovery and water reclamation.
GEA Filtration is world renowned for its design of the most advanced cross-flow membrane filtration systems. GEA Filtration and GEA Liquid Processing work closely together and are consequently able to supply complete process lines for production of a variety of products within the dairy, food, juice, brewery and biotech industries.
For more detailed information on membrane filtration in general and GEA Filtration in particular, please visit the GEA Filtration homepage.