Reverse Osmosis Filter

The reverse osmotic treatment process is an accepted method for the treatment of wastewater. But before you consider applying this form of wastewater treatment, you must know certain points about osmosis and the right pressure that has to be maintained for the proper functioning of osmotic plants. In this article I tell you how to calculate this pressure.

Osmotic Pressure

The osmotic pressure can be defined as the pressure difference found between two solutions at a state of equilibrium, but with different amount of salinity, when the two solutions are kept at the two sides of a semipermeable membrane. The osmotic treatment requires that one of the solution is of high concentration which will absorb water molecules. But in the reverse osmosis commonly employed, this principle is reversed by applying pressure on the concentrated solution which forces the water molecules out to the other side of the membrane and into the diluted solution, thus increasing the purity of the diluted solution. This process yields water with high level of purity.

When the osmotic pressure is defined in relation to water molecules, it is the difference in potential energy existing in the water molecules in two separate solutions.

The formula used to calculated the pressure required for osmotic filtration is as follows:

(RT) (Pa^o)
----In--------- = B
(Va) (Pa)

In this formula,
B represents the osmotic pressure written as "atm",
R represents the value 0.082 (l. Atm / (mo l.k)),
T represents the temperature of the solution written as (k),
Va represents the value - volume/mole of the solvent written as (l/mol). Here Va of water is 0.018 l,
Pa^o represents the pressure of vapor of the solvent in the dilute solution written as atm, and,
Pa represents the pressure of the vapor of the solvent in the concentrated solution written as atm.

To calculate the osmotic pressure of the diluted solutions the formula, B = CRT is used. In this formula, the unit C represents the concentration level of the solute written as mol/l.

The success of the reverse osmotic treatment process depends on how the osmotic pressure and the external pressure is applied to the wastewater solution and the capabilities of the separating membrane. Without the correct pressure the process will not succeed.