RO逆滲透淡水製造機 RO Desalinators for sea water

A container is divided in two sealed parts by a semi-permeable membrane.

The right side is filled up with seawater,

The left side is filled up with freshwater,

With no external intervention, a freshwater flow passes through the membrane from the freshwater compartment to the seawater compartment.

This is the phenomenon of OSMOSIS.


A pressure is now applied on the seawater compartment..

The pressure sufficient to stop the osmosis phenomenon is called osmotic pressure.

In the case of seawater, the osmotic pressure is approximately 28 bar.


If a pressure higher than the osmotic pressure is now applied, the flow of fresh water passing through the membrane is reversed.
The salts present in the sea water are stopped by the semi-permeable membrane. Thus, only fresh water flows through the membrane from the seawater compartment to the fresh water compartment.

This is the phenomenon of REVERSE OSMOSIS.


A semi-permeable membrane is different from a filter.

Initially, the freshwater compartment is empty and only the seawater compartment is filled up. Despite the high pressure applied in the seawater compartment, no flow will pass through the membrane.


To put it in a nutshell, to obtain the phenomenon of osmosis, one must have:

A semi-permeable membrane
A couple sea water / fresh water
To obtain the phenomenon of reverse osmosis, it is necessary, in addition, to have:

A pressure higher than the osmotic pressure applied on the seawater compartment.