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.
Microfiltration
Microfiltration (MF) membranes are extremely cost-effective to operate, largely as the result of the low energy consumption involved. They also have the advantage of eliminating the frequent replacement and disposal of the cartridges and other consumables used in traditional dead-end filtration. Microfiltration is used on feed streams where the aim is to remove small diameter dispersed solids such as bacteria, fat and oil globules without affecting the balance of the components dissolved within the stream.
Ultrafiltration
Ultrafiltration (UF) uses membranes in which the pores are somewhat smaller, with a cut-off range from 1,000 to 100,000 Molecular Weight (MWCO), and where the applied pressure is relatively low. Salts, sugars, organic acids and smaller peptides pass through the pores of the membrane, whereas proteins, fats and polysaccharides do not. Using appropriate ultrafiltration membranes also makes it possible to separate a feed stream into two distinct streams. Each contains dissolved components with different molecular weights.
Nanofiltration
Nanofiltration (NF) uses membranes with pores that are even smaller – down to 600 daltons. Operating at pressures of up to 50 bar, small ions pass through, whereas larger ions and most organic components do not. Our nanofiltration elements are used for the high-yield concentration and demineralization of products such as whey and ultrafiltration permeate. These special membranes are used for filtering out large salts with a divalence in excess of 2, while small monovalent salts pass into the permeate. They can also be used in producing low-alcohol beverages, because the alcohol component passes through the membrane, while the colour and aroma remain in the retentate.
Reverse osmosis
Reverse osmosis (RO) uses membranes with pores so minute that only small fractions of salts can pass through, along with the water that is the prime component of the permeate. Certain organic compounds with low molecular weights can also pass through – but only to a limited extent. However, it is impossible for any other components suspended or dissolved within the liquid flow (salts, sugars, etc.) to do so.
