Impeller meters using reverse osmosis membrane technology

Reverse osmosis is a process for filtering out molecular-sized particles. In normal filtration, impure water is pressed against a filter material. The molecular-sized particles remain behind on the filter and the water molecules pass through.

In reverse osmosis, a semipermeable membrane is used as the filter. This membrane is not permeable to water but can absorb water into its molecular structure.
Dissolved substances of a solution are selectively separated. For example water, under the pressure of a
semipermeable membrane, will lets water molecules pass through, but not the impurities. Viruses, sugar, proteins, pectines or salt (desalination of sea water) can then be separated from a solution. Pressures up to 100 bar can be used in this process, and it requires a pump. The pump pressure must be higher than the osmotic pressure which arises at the surface of the membrane. On the one side of the membrane, pure water is collected and on the other side, impurities are routed away.

Physical plants with a reverse osmosis modules, such as sea water desalination facilities, are currently in operation using reverse osmosis.
The following example shows the reverse osmosis of a smaller plant in which the input water, i.e. drinking water under pump pressure. The “pure water” is collected on the one side of the membrane (permeate), the impurities (concentrate) are routed into the effluent.