Reverse Osmosis Systems (RO)
Reverse osmosis (RO) is a membrane separation process in which feed
water flows along the membrane surface under pressure. Purified water
permeates the membrane and is collected, while the concentrated water,
containing dissolved and undissolved material that does not flow
through the membrane, is discharged to the drain.
requirements of Reverse Osmosis (RO) process are a membrane and water
under a pressure. Other requirements include pre-filtration to remove
suspended impurities and carbon to remove chlorine (damages the
Most membranes remove 90-99+ % of the dissolved
impurities depending on the impurity and the composition of water.
Reverse osmosis systems (RO Systems) remove salts, microorganisms
and many high molecular weight organics. System capacity depends on
the water temperature, total dissolved solids in feed water, operating
pressure and the overall recovery of the system.
Osmosis can be
defined as the spontaneous passage of a liquid from a dilute to a more
concentrated solution across an ideal semipermeable membrane which
allows the passage of the solvent (water) but not the dissolved solids
(solutes). (See Fig. 1.) The transfer of the water from one side of
the membrane to the other continues until the head or pressure (P) is
large enough to prevent any net transfer of the solvent (water) to the
more concentrated solution. At equilibrium, the quantity of water
passing in either direction is equal, and the pressure (P) is then
defined as the osmotic pressure of the solution having that particular
concentration of dissolved solids.
If a piston is placed on the
more-concentrated solution side of a semipermeable membrane (see Fig.
2) and a pressure, P, is applied to the solution, the following
conditions can be realized: (1) P is less than the osmotic pressure of
the solution and the solvent still flows spontaneously toward the more
concentrated solution; (2) P equals the osmotic pressure of the
solution and solvent flows at the same rate in both directions, i.e.,
no net change in water levels; (3) P is greater than the osmotic
pressure of the solution and solvent flows from the more concentrated
solution to the "pure" solvent side of the membrane. Condition (3)
shown in Fig. II-2, represents the phenomenon of reverse osmosis.
Envirotech specializes in the supply of reverse osmosis systems
for desalination, industrial water reuse, electronics manufacturers,
potable water supplies and for food and beverage industries. Our
packaged RO units can supply from several cubic meters per day to
several hundred cubic meters per day.