Membrane Cartridge Filters Explained by Micron Rating

When precision, product quality, or sterility is critical, membrane cartridge filters are the final line of defence in a liquid or gas filtration process. Their ability to provide absolute retention — capturing particles and microorganisms down to submicron levels — makes them essential across industries such as pharmaceuticals, food and beverage, microelectronics, and municipal water treatment.

But not all membranes are the same. One of the key selection criteria is the micron rating — the nominal or absolute pore size of the membrane that determines what contaminants are removed and what passes through. Choosing the correct micron rating ensures optimal process protection without unnecessary pressure drop or premature blockage.

Let’s explore the typical applications of membrane cartridge filters by micron rating, from coarse clarification through to final sterilisation.

1.0 Micron Membranes — Coarse Clarification & Prefiltration

At this range, membranes are typically used as prefilters to remove visible particles, rust, and coarse colloids before finer downstream filtration steps.

Typical Applications

• Food & Beverage: Clarifying water used in bottling or blending; removing haze-forming particles in spirits or soft drinks.
• Pharmaceuticals: Protecting expensive 0.2 µm sterilising membranes from premature fouling by upstream particulates.
• Microelectronics: Removing coarse particles from rinse water or process chemicals before submicron filtration.

Common Materials

PES (Polyethersulfone) membranes with absolute ratings in this range are popular, often combined with depth prefilters for staged particle reduction.

0.45–0.65 Micron Membranes — Bioburden Reduction & Fine Clarification

This range bridges the gap between particle removal and microbial control. Filters in this class are often termed bioburden reduction filters.

Typical Applications

• Pharmaceutical & Biotech: Reducing bacterial load prior to 0.2 µm sterilising filters, extending their life.
• Beverage Processing: Cold sterilisation of beer, cider, and bottled water; yeast removal in final filtration of wine.
• Diagnostics & Laboratory: Clarifying buffers, reagents, and serums before sterile filtration.
• Industrial Processes: Fine filtration of coatings, resins, or inks where particle-free consistency is required.

Common Materials

Membranes such as PES, Nylon, or PVDF offer high flow rates and low protein binding in this range.

0.2 Micron Membranes — Sterilising Grade Filtration

This is the most critical class of membrane filters in industries where microbial sterility is essential. A 0.2 µm membrane is validated to remove Brevundimonas diminuta — the benchmark organism for sterilising-grade filters.

Typical Applications

• Pharmaceuticals & Biotech: Final sterile filtration of injectables, vaccines, WFI (Water for Injection), and media solutions.
• Food & Beverage: Cold sterilisation of wine, beer, bottled water, and soft drinks without the need for heat treatment.
• Microelectronics: Filtration of ultrapure water and chemicals such as photoresists, developers, and solvents.
• Laboratory & Research: Sterile filtration of culture media, buffers, and serums.

Common Materials

Hydrophilic PES or PVDF for aqueous solutions; hydrophobic PTFE for gases or solvents. Filters are integrity-testable and validated to pharmaceutical standards (e.g., ASTM F838).

0.1 Micron and Below — Ultraclean or Virus Retentive Filtration

Sub-0.1 µm membranes approach the ultrafiltration boundary, used when extremely high purity or bioburden control is required.

Typical Applications

• Pharmaceutical & Biotech: Removal of mycoplasma and small bacteria; virus reduction steps in biologics manufacturing.
• Microelectronics: Filtration of high-purity chemicals and ultrapure water for semiconductor wafer cleaning.
• Healthcare & Life Sciences: High-purity water systems in dialysis or laboratory reagent production.

0.02 Micron - Gas Filtration

In dry gases PTFE membrane filters can be rerated for virus and phage removal due to the improved performance of the mechanisms of filtration. For more on this read our blog – Ensuring You Use The Optimum Sterile Gas Filter

Typical Applications

• Pharmaceutical & Biotech: Inlet and outlet gases from fermenters and bioreactors protecting the contents, but also the environment by ensuring containment.
• Beverage, Water Treatment, Cosmetics, Dairy: Venting of storage tanks and vessels for used for final product storage and storage tanks used in the manufacture of products.

Common Materials

Advanced PES or PVDF membranes with high throughput and low extractables; PTFE for aggressive solvents and gases.

Hydrophilic vs. Hydrophobic Membranes — A Quick Note

• Hydrophilic membranes (e.g., PES, Nylon) are used for aqueous solutions — they wet easily and don’t require pre-wetting.
• Hydrophobic membranes (e.g., PTFE, PVDF) are used for air and gas filtration, or for solvents — they repel water and prevent liquid breakthrough in vent and sterile gas applications.

It should be noted that certain manufacturers offer modified PTFE and PVDF membrane cartridge filters so that they act as hydrophilic membranes.

Choosing the Right Micron Rating

Selecting the correct membrane micron rating depends on:

• Process objective: Clarification, bioburden reduction, or sterilisation
• Fluid type: Water, solvent, chemical, or biological
• Particle load and upstream filtration: To avoid premature fouling
• Regulatory or quality requirements: Sterility validation, integrity testing, etc.

Often, a graded filtration train provides the best performance — starting with a depth filter (e.g., 5 µm), followed by a finer prefilter (0.45 µm), and ending with a 0.2 µm sterilising membrane.

Summary Table: Membrane Filter Applications by Micron Rating

Final Thoughts

Membrane cartridge filters are precision-engineered tools that directly influence product quality, process efficiency, and regulatory compliance. Matching the micron rating to the right application isn’t just about removing particles — it’s about protecting downstream processes, extending filter life, and ensuring consistency from batch to batch.

When in doubt, start with a clear understanding of your process contaminants, product requirements, and validation needs — then work backwards to define your filtration train.

If you have any questions about membrane cartridge filtration, then you can give us a call or send us an email - we’d be more than happy to help. 

You can also view our full product ranges for membrane filters or read more in our blogs:  

• Membrane Cartridge Filters & Sterile or Final Filtration
• The Differences Between Membrane and Depth Filters in Microfiltration
• Guide to Selecting the Right Micron Rating
  

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