To date, WFI had to be final distilled in Europe. Distillation represents a very safe process for the production of WFI and is therefore seen worldwide as the gold standard for WFI production.
In recent decades, with the development of new manufacturing methods in water treatment, there has been a demand from the industry to use these new processes for WFI generation as well, thereby reducing costs.
With the new WFI monograph of the Ph. Eur. In parallel, the pharmacopoeias of Europe, the USA and Japan have now been harmonized to a large extent.
These pharmacopoeias now allow the recognized preparation of WFIs without distillation.

Nevertheless, in order to be able to produce WFI compliantly and reliably, a suitable plant design and appropriate monitoring of the process technology are required.
The currently existing specifications on the part of the authorities still contain ambiguities and raise questions.
This is one reason that there is not yet a common understanding.

The interdisciplinary team of experts of the ISPE D/A/CH Community of Practice (rCoP) for pharmaceutical water and steam has produced a guideline in the form of a 110-page manual (d) for understanding.
This will provide an overview of the regulatory requirements, and open questions regarding membrane-based manufacturing of WFI will be answered from the experts’ perspective. Planners, operators, equipment manufacturers, drug manufacturers, and government officials are provided with a practical guide that addresses regulatory compliance as well as technical and operational feasibility.