Reverse osmosis (RO) as a main barrier to all types of impurities plays an essential role in both the production of Purified Water (PW) and cold WFI production. In the pharmaceutical industry, this module has to be heat sanitisable. The frequency of sanitisation is set in the qualification and has to be confirmed in the course of the Performance Qualification (PQ). Now the question is at which frequency should one initially start? The answer is: as often as required but not more than necessary, as sanitisation means thermic stress for the equipment.
Reverse osmosis is not the only element for water purification. RO is very often combined with an EDI unity and an ultrafiltration system. Sanitisation doesn't operate for each component separately but for the whole purification chain. Here, the EDI unity constitutes the most temperature-sensitive component. To avoid a replacement more than every five years, sanitisation by heat every three months has proven to be fruitful. A durability of 100-120 cycles can be expected. This applies to at least Europe and the Scandinavian region. Where the quality of the source water is worse, it may be necessary to increase the frequency. As already mentioned, the efficacy has to be confirmed - in any case at stage 3 of the PQ.