Medical water is an essential resource for the operation of healthcare facilities. Particular care must therefore be taken with its bacteriological quality in order to protect patients and healthcare staff. The prevention of health risks linked to pathogenic micro-organisms in domestic hot water networks, foremost among which are Legionella, is moreover strictly regulated. To guarantee the quality of your medical water, innovative filtration solutions that are easy to implement are available. Pemflow reviews the issue.
Legionellosis: what is it?
Legionellosis is a serious lung infection caused by bacteria, Legionella, present in water or humid soils. Legionella bacteria proliferate in water systems, particularly when water temperature is between 25 and 45 °C, with an optimum between 32 and 35 °C. If the water is stagnant and/or contains other micro-organisms capable of providing the nutrients required for Legionella metabolism, limescale or corrosion elements (iron, zinc), the development of Legionella is promoted.
Legionellosis is contracted by inhaling aerosols (micro-droplets) of water contaminated with the bacteria, for example during showering. It is not transmitted from person to person. While anyone can be affected, the risks increase with age, chronic respiratory disease, smoking, etc.
The disease manifests as a high fever and a severe cough. In severe cases, it requires hospitalisation and the administration of antibiotic treatment.
Legionellosis: legal obligations
Legionellosis is a notifiable disease that healthcare professionals must report to their Regional Health Agency (ARS). For each reported case, the territorial authorities carry out an epidemiological and environmental investigation in order to identify and control potential sources of contamination.
Hotels, tourist residences and campsites, high schools and secondary schools, municipal swimming pools, as well as healthcare facilities and nursing homes—that is, all public-access buildings (ERP)—are concerned by this regulation.
Requirements are particularly stringent with regard to the production and distribution of medical water. Healthcare establishments and facilities housing elderly people are subject to special attention, as they are equipped with high-risk installations (showers) and accommodate a vulnerable population.
In its report entitled Legionella risk – Investigation and management guide, published in July 2013, the High Council for Public Health updated the recommendations relating to the actions to be taken in the event of one or more cases of legionellosis, in light of the latest epidemiological advances and regulatory and institutional developments. Similar recommendations and standards exist for other bacterial populations and endotoxins.
To learn more about endotoxin filtration in pharmaceutical waters
Bacteria and biofilm
In addition to Legionella, other bacteria, whether circulating or trapped within biofilm, may threaten the safety of medical water systems. These include, for example:
- Pseudomonas aeruginosa, or pyocyanic bacilli, increasingly responsible for nosocomial infections, which develop in humid environments (mists, taps, caps) and are highly resistant to most antiseptics;
- Non-tuberculous mycobacteria, which can cause pulmonary, cutaneous or lymphatic infections and lead to disseminated infections in immunocompromised patients.
Particular attention must be paid to biofilm, this thin layer containing micro-organisms (bacteria, algae, fungi, etc.) that lines the surfaces of installations and whose growth must be controlled.
Medical water: which filtration devices should be adopted?
Poorly insulated water pipes, hot water temperatures that are too low, insufficient flow leading to water stagnation, premises left unoccupied for long periods… all these factors promote bacterial growth and impair water quality.
Once these factors have been brought under control, it is advisable to equip certain critical points of your water system with high-performance antibacterial filtration systems.
With regard to Legionella and other bacterial contaminations, the points of use at risk are those likely to expose patients to aerosols smaller than 5 µm; these are in particular showers and taps.
On taps used for hand hygiene, it is possible to install a “terminal” sterile filter. For wall-mounted or hand-held showers, various devices can be implemented depending on the configuration: antibacterial hoses and shower heads.
These devices can be used at maximum temperatures of around 70 °C.
All of them incorporate antibacterial filters that limit biofilm formation and eliminate bacteria. To achieve this, pleated or tubular filtration membranes are used, providing terminal microfiltration. The water to be treated passes through the membrane under pressure. Particles whose size is greater than the pore size are retained by the filter. The filtered water is thus purified of suspended matter (colloids, mineral particles, organic residues, etc.) and of the micro-organisms it contains.
To learn more about microfiltration
Hollow fibre technology, your best ally
Sterilising-grade hollow fibre membranes (0.1 µm) are generally preferred to pleated membranes, which are inherently limited in filtration surface area. Depending on the manufacturer, these fibres have different diameters as well as different media qualities (polysulfone, nylon, PVDF, polypropylene).
This technology offers the major advantage of multiplying the filtration surface area by two or even three for the same filter element size, compared with a pleated membrane cartridge. Devices using hollow fibre membrane technology are therefore particularly compact, which for example makes them easier to install on existing taps.
This increased filtration surface area also makes it possible to adopt a lower filtration rating (thus ensuring better antibacterial protection) without reducing flow rate, thereby increasing filtration efficiency (for example using 0.1 µm instead of 0.2 µm), or to increase flow rate without increasing pressure drop.
To learn more about hollow fibre membrane technology
Filtered taps (or shower heads) also contain a bacteriostatic additive that reduces the risk of retrograde contamination. The latter, also known as reverse contamination, can occur when the water outlets of fittings come into contact with germs carried by water splashes. Water projections generated by the flow can indeed lead to retrograde contamination caused by bacteria present in the trap.
Ideally, taps and showers should also be equipped with a check valve, which is useful during filter replacement phases; this prevents contaminated water from flowing when the filter is removed.
To reduce the risk of retrograde contamination, silver ions can be used, for example. Incorporated into the plastic material during the filter manufacturing phase, they provide protection throughout the entire service life of the filter.
Expert advice
It is advisable to prioritise long service-life filtration devices in order to avoid the constraint of overly frequent filter replacement. For example, there are medical filters available on the market that can remain in place for up to 92 days.
Shower or tap filters can be replaced quickly thanks to screw-on end systems or clip-on connections, which also ensure perfect sealing. Flow restrictors help to reduce costs and protect the filter, thereby extending its service life.
Finally, it is essential to choose filters whose antibacterial efficiency complies with the applicable standards (for example ASTM F 838-05 and ASTM F 838-15a) for various micro-organisms (Pseudomonas aeruginosa, Legionella pneumophila, Brevundimonas diminuta, Aspergillus brasiliensis, etc.).
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