Water
The membrane separation is a technique based on the use of a physical barrier, a porous permeable membrane, to separate and concentrate the substances contained in a liquid. This process does not require heating and leads to the formation of two final fractions (permeate and retentate) which can both be employed in several industrial fields, in water treatment as well as in food industry.
The main membranes technologies can be distinguished in the following main categories:
- Reverse osmosis which enables the separation of ions, unwanted molecules and substances characterized by a very low molecular weight (salts, sugars and acids) by applying a pressure higher than the osmotic one to the treated solution. It can be applied for the demineralization of well water or network water for industrial use, seawater and brackish desalination as well as for contaminated water purification.
- Nanofiltration is a method that requires a membrane with 1-10 nanometer-sized porous and a lower operating pressure compared to reverse osmosis. It is mainly used to remove divalent ions, nitrates and other mineral salts from water for water softening.
- Ultrafiltration is a membrane filtration technology aiming at the purification and concentration of macromolecular solutions such as protein solutions: the suspended solids characterized by high molecular weight are separated from the filtrate by passing through the membrane at a pressure between 1-10 bar. It can be employed for surface water treatment, civil and industrial wastewater purification and seawater treatment.
- Microfiltration where a contaminated fluid passes through a special pore-sized membrane for the separation of microorganisms and suspended particles bigger than 1 micron. This process is used for the removal of the solution turbidity due to the presence of fine colloids.
