Sub-micron Filtration

Last Updated
January 20 2021
Sub-micron Filtration

What is Sub-micron Filtration? 

Filters essentially work in the same way as a sieve and provide a physical barrier based on pore size to the passage of particles, while allowing water to pass through. Pre-treatment may include one or more filters with pore sizes ranging from 1 to 100 microns to remove gross particulates but within the purification system sub-micron filtration is used to remove contaminants including fine particulates, colloids and bacteria – microporous filters (0.05 to 0.22 micron) or ultrafilters (0.001 to 0.01micron).

What does Sub-micron Filtration remove from water?

Microporous screen filters remove all particulates greater than the specified pore size. Filters with a pore size of 0.22 micron or less will trap bacteria. Positively charged membranes will also remove endotoxins. Ultrafilters can remove micro-organisms and large organic molecules including nucleases and endotoxin.

How does Sub-micron Filtration work? 

Microporous screen filters provide a physical barrier to the passage of particles and microorganisms in purified water systems. Screen filters, characterised by absolute particle size ratings, retain all particles larger than the controlled pore size on their surface. Trapped material can build up on the surface and be leached through the filter so filters need to be sanitised or autoclaved periodically or replaced.  They are often fitted as point-of-use devices at the very end of the purification chain to ensure the absence of bacteria and to protect the system from back-contamination. 

Positively charged microporous filters provide additional highly effective removal of negatively charged species such as endotoxins.

Ultrafilters are membrane filters with pore size of typically 1 to 50 nm which can remove particles as small as protein macromolecules. They produce greater back-pressure than microporous filters and are often used in the form of hollow fibres to maximise the surface area.  Ultrafilters are used in the polishing purification loop.

What are the benefits of Sub-micron Filtration?

Filtration below 0.2 micron has proved essential in maintaining purified water free of bacteria and other particulates. Finer filtration removes large molecules and biologically active materials such as endotoxins. Point-of-use filters are widely used to protect purification systems from back-contamination and are easy to autoclave or replace.

How does ELGA LabWater use Sub-micron Filtration?

Point-of-use sub-micron filters can be fitted to most ELGA PURELAB systems including Chorus 1 and and Complete. The purification loop passes just before the filter ensuring as much of the system is protected by recirculation. Additional filtration is included in the recirculation loops of some of the polishers: 0.05micron filtration in the Chorus 1 Analytical Research and ultrafiltration in the Chorus 1 Life Science.

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Relevant Impurities