Osmosis is a natural phenomenon whereby water passes through a semi-permeable membrane from a solution with low salt concentration into a solution of higher salt concentration until an equilibrium in the chemical potential of the water is established.

In the state of equilibrium, the differential pressure over both sides of the membrane is identical to the osmotic differential pressure. In order to reverse this osmotic flow of water, external pressure, greater than the osmotic differential pressure of both solutions, has to be applied. This additional external pressure enables the dissolved salt to be separated from the water. This phenomenon is defined as “reverse osmosis”.

Reverse osmosis processes are generally divided into three categories:

  • High-pressure reverse osmosis (5 – 10 MPa, as in seawater desalination)
  • Low-pressure reverse osmosis (2 – 5 MPa, as in brackish water desalination)
  • Nanofiltration (0.3 – 2 MPa, as in softening of drinking water)

Mechanism and Properties of RO Membranes

Reverse osmosis is a filtration process that is often used for water. It works by using pressure to force a solution through a membrane, retaining the solute on one side and allowing the pure solvent to pass to the other side.

 A reverse osmosis membrane acts in the form of a physical barrier for the hydraulic flow, allowing selective permeation of the solvent (mostly water) and partial or total retention of the other dissolved substances (mostly salt).

Membrane material, manufacturing conditions and membrane morphology are decisive factors for the retention of dissolved substances and water permeability. However separation basically takes place on a thin, selective layer of the reverse osmosis membrane.


While nanofiltration membranes are frequently considered as porous membranes, reverse osmosis membranes are defined as closed, nonporous films. The permeate is adsorbed by the membrane material and can diffuse through the structure.

Typical salt retention values for reverse osmosis are between 98% and 99.9%. A reverse osmosis membrane will completely retain all molecules which have a molecular weight of more than 150 Dalton.  



Membrane type: Poliamide thin film composite

   Residential RO Membranes

AMFOR® reverse osmosis membrane elements for home drinking water are the most reliable. Advanced membrane technology and automated fabrication allow these elements to keep consistent performance and suitable for long distance transportation.

AMFOR home drinking water elements are rated at 50psi and will purify about 20% more water than competitive elements rated at 60psi (please see the datasheet for more information)

TW30-1812, TW30-2012, TW30-2812, TW30-3012

 Commercial RO Membranes

AMFOR®  reverse osmosis (RO) elements offer the highest quality water for small commercial systems.

AMFOR membranes are available in a variety of sizes to meet a wide range of space requirements. Nowdays, AMFOR TW30XLE-3020-600, TW30XLE-3020-1000 have been widely used in commercial drinking machine.

AMFOR XLE extra low energy elements operate at the lowest pressure in the industry,resulting in lower energy costs and enabling system builders to use lower cost components.

In addition to the highest quality water and the lowest energy costs, AMFOR membranes also deliver savings by  providing the industry’s longest lasting and most reliable performance.

  Industrial RO membranes;

BW30-BWLE400-BW30XLE (-4040), BW30-365,  BW30- 400, BW30LE- 440

 Sanitary RO Membranes

AMFOR® RO elements contain a new high-rejection reverse osmosis membrane capable of wide range of food and dairy applications, including those requiring 3A compliance. These elements are especial y effec-tive in dewatering or product concentration. The ful -fit configuration is optimal for cleaning and minimizing〃 dead spaces.〃 All components comply with FDA standards and are suitable for use in food processing applications..

 RO-3838FF/31, RO-4040FF/31, RO-8040FF/31, RO-8040FF/48

 HSRO Membranes

AMFOR® HSRO heat sanitizable reverse osmosis membrane elements deliver outsanding quality water with the added capability to withstand sanitization with hot water. HSRO elements have the highest active membrane area in the industry. This high area allows system design with either lower operating flux or cost saving from fewer membrane elements. The ful -fit configuration minimizes stagnant area and is optimal for applications requiring a sanitary design. Al components comply with FDA standards.  


  Sea Water RO Membranes 

AMFOR® seawater reverse osmosis elements offer the highest productivity while maintaining excellent salt rejection

SW30 2514, SW30 2521, SW30 2540, SW30 4021, SW 4040