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Filtration in Medical Device Reprocessing

The majority of filtration in medical device reprocessing is for water. Water is used for everything from mixing detergents and other chemicals used in cleaning and high level disinfection to the final rinse water. Filtration is critical for a number of reasons, the most obvious being the protection of patients from bacteria that might be deposited on devices if plain tap water is used. Another, less obvious critical application for filters is to remove particulates that, if mixed with chemicals, can bond to the surfaces of instruments and cause visual defects or affect the functionality of the instrument.


Filters in Instrument Wash Water Systems

Particle Filtration and System Prefiltration in Reverse Osmosis Water Systems

Removal of sediment and other suspended particles is critical to the efficient, cost effective operation of any RO treatment system. Performed using depth filtration media, particle filters and system prefilters preserve the performance of each water treatment step and assure efficient RO membrane performance. Using these filters can reduce the frequency of RO membrane cleaning and extend the useful life of the membranes.

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Trap Filtration

Treated process water often passes through tanks containing activated carbon powder that may release small particles. Softeners and deionization tanks contain resin beads that may break down, fracture and release small particles. In both cases, filters are used to trap the particles and prevent their migration into downstream treatment process steps. Again, depth filtration is most often used for this function.

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Bioburden Reduction and Sterilizing Filtration

Chlorine must be removed from water entering most RO systems, so there is no protection against the growth of organisms that may become trapped in the system. Those organisms can grow and be released downstream to contaminate a distribution system and/or medical devices and treatments. To protect downstream systems, and prevent possible pathogens from reaching patients, filters are used to remove bacteria.

Devices Reprocessed via High Level Disinfection
Some medical devices that cannot be sterilized using high temperatures (such as in an autoclave) are reprocessed using high level disinfection (HLD). The most common devices fitting this description are endoscopes. The endoscopes are usually reprocessed, after manual cleaning, in a machine that flushes the device with detergents and then exposes the device to an approved chemical disinfectant. The water used for mixing the chemicals and rinsing the devices may be treated as in the schematic above, but most facilities use municipal or other potable water sources to feed the reprocessing machines. The water is almost always filtered, regardless of the source.

Bioburden ReductionSterilizing Filtration



Tank Vent Filters

Filters help prevent contamination of treated water in a storage tank, protecting both the system and patients. The air around tanks is full of airborne bacteria, other organic contaminants and particulates. Drawing water from a tank also draws that contaminated air into the tank.

Very few healthcare facilities have water systems in controlled spaces similar to cleanrooms. Also, many tanks used for water storage are not sealed but have a loosely attached cover over an opening used for inspection and cleaning. Securely closing the cleaning hatch and adding particulate filtration for air may keep dust out of the system.

Some facilities may want to protect the water system from airborne bacteria. Sealing the tank and installing a hydrophobic membrane filter will protect tanks from bacteria and small particles and also protect patients.

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Filters for Medical Device Rinse Water


Particle Removal/Prefiltration in Device Reprocessing

The schematic shown above has a filter to remove particles and a second, optional filter to remove either more particles or some of the bacteria that might be in the water. Both filters are in place to protect the final, bacteria filter from premature fouling (clogging).

The type and number of filters used by any facility is determined by incoming water quality. If incoming water has a high particle content, then it may be necessary to use 2 prefilters to capture those particles before they foul the bacteria filter. If the water is from a source that has fewer particles, then a single prefilter is probably all that is required.

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Bacteria Control in Device Reprocessing Water

For water used in device reprocessing, most facilities use a filter to remove bacteria from the water so that the system can supply ‘bacteria-free’ water. Filter manufacturers designate many different filters as ‘bacteria removal’ filters. The version most often used in healthcare facilities is a membrane-based filter rated at 0.22 or 0.2 microns. In most cases, the filter is supplied with certifications from the manufacturer stating that the filter has been tested to assure it will remove all bacteria.

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To estimate the number of filters you will need for your application, use our unique sizing tools.

Contact Critical Process Filtration if you have any questions, wish to discuss a specific application or want to learn more about any of our Products and Services. We look forward to hearing from you!