Another method for producing process water is reverse osmosis.
Two chambers, separated by a semipermeable membrane that is exclusively permeable to water molecules, are responsible for the purification.
If the pressure in the raw water chamber is now greater than the corresponding osmotic pressure, the water migrates against its concentration gradient through the membrane into the process water chamber. To meet the high requirements of the process water, several modules are usually installed in series.
Compared to conventional purification methods (distillation, ion exchange), the advantages of the reverse osmosis system (Cold WFI) lie in the significantly lower energy consumption and the much more compact design.
Since April 2017, the cold membrane process (Cold WFI) for the production of water for injection purposes has also been approved by the European Directorate for the Quality of Medicine and Healthcare (EDQM).