Reverse osmosis (RO) is a separation process that uses pressure to force a solvent through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. It is the reverse of the normal osmosis process, which is the natural movement of solvent from an area of low solute concentration, through a membrane, to an area of high solute concentration when no external pressure is applied. Osmosis membranes are semi-permeable, meaning they allow the passage of solvent but not of solute.
Membranes used for reverse osmosis have a dense barrier layer in the polymer matrix where most separation occurs. In most cases the membrane is designed to allow only water to pass through this dense layer while preventing the passage of solutes (such as salt ions). This process requires that a high pressure be exerted on the high concentration side of the membrane.
Nanofiltration is another membrane process, used most often with low TDS waters such as surface water and fresh groundwater, with the purpose of softening and removal of disinfection by-product precursors such as natural organic matter and synthetic organic matter.
Reverse osmosis and nanofiltration systems from Siemens Water Technologies are rugged, pre-engineered, pre-assembled, standardized units that minimize expensive installation and start-up costs. We offer a wide variety of systems to meet your requirements for high-purity water.