Pharmaceutical industry filtration requirements may be the highest among all industries. Having participated in multiple GMP workshop filtration system designs, I share some practical experience.
Purified water systems typically use two-stage filtration. The first stage is 5-micron precision filtration, primarily removing large particles and colloidal substances to protect the downstream terminal filter. The second stage is a 0.2-micron terminal filter cartridge, serving as the final bacterial barrier. Piping between the two stages should use circulation design to keep water flowing continuously and prevent bacterial growth in dead zones.
Water for injection systems are more complex. Besides filtration, thermal preservation must be considered. Filtered water should be kept circulating above 80 degrees Celsius and cooled when in use. Filter cartridges here must use high-temperature resistant PTFE materials.
Another easily overlooked issue is filter cartridge integrity testing. Each batch should undergo bubble point testing or diffusion flow testing before use to confirm the filter cartridge is not damaged.
