Sterile filtration

Trustworthy companion to prevent infection

Drinking water in Germany is probably subject to more controls than any other foodstuff and has to conform to strict standards. After the water has been treated, its chemical and microbiological parameters are tested at the waterworks. They must meet the quality requirements specified by law. The conditions change when drinking water is fed into the household water system. In household systems, the water pressure is lower than in the supply pipe; drinking water is heated or is used irregularly and stays in the pipes for days or weeks without moving. A small number of bacteria can enter the water system when the piping is fitted. These bacteria can multiply very well under such conditions and settle on the internal walls of the pipes. Water experts call these deposits biofilm. Biofilm is a kind of bacterial community. The bacteria use this film to protect themselves from heat and also from chemicals (e.g. chlorine). It is almost impossible to remove completely by flushing, disinfecting etc.

Germany's Drinking Water Ordinance has therefore established standards for water quality. One drop of drinking water is allowed to contain up to 100 pathogens. This amount of pathogens is not dangerous for the healthy general population. The water can be drunk without misgivings and can be used for daily personal hygiene.

Special challenges at medical establishments

Hospitals, however, are subject to numerous recommendations for the safe use of drinking water – e.g. from the Federal Environment Agency, the Robert Koch institute and the Working Group "Hygiene in Hospital & Practice". Nurses, hygiene specialists and doctors face the serious challenge of the spread of Gram negative, pathogenic bacteria, a challenge that is almost impossible to overcome without a comprehensive prevention plan.

Water outlets contribute to the risk of infection in medical establishments. There are many different reasons, some of which are not related to the original quality of the water. It was found that water could be identified as the original reservoir of Pseudomonas aeruginosa-related nosocomial infections in intensive care units in up to 50 % of cases of infection; drinking water installations are to be seen as a relevant but previously underestimated infection reservoir of Pseudomonas aeruginosa. 1 This risk must be reduced as much as possible.

In the past 15 years, sterile filtration has become firmly established as an important supporting factor in prevention. 2,3 Medical CE-marked sterile filters serve to prevent infection and reduce the risk of nosocomial infection due to waterborne pathogens. In a recent study, Pseudomonas aeruginosa was found in 8 % (11/136) of the water outlets examined at a liver transplant center. After the installation of point-of-use filters, Pseudomonas aeruginosa and Legionella and mycobacteria were no longer found in tap water samples. In addition, the rate of colonization / infection due to Gram negative rod-shaped bacteria was reduced by 47 %. 4

For successful infection prevention, a point-of-use filter placed on the faucet or shower for the sterile filtration of drinking water should fulfil the following criteria:
• Bacterial retention as required by ASTM F838-15A: > 7 log per cm2 (Brevundimonas diminuta)
• Bacteriostatic properties of the filter housing throughout the period of use
• Filter surface can be disinfected by wiping
• CE-marked medical device

Second generation of point-of-use sterile filters

With 15 years' experience in this area, i3 Membrane has employed ion-supported technology to develop compact high performance sterile filters on the basis of the formulated requirements. With the second generation of sterile filters, i3 Membrane is now setting new standards in infection prevention. Precise engineering work has further improved the high performance membrane - the centerpiece of the filter - so that sterile filtration with a high flow rate is assured even when the water quality is poor (e.g. as a result of deposits of rust, iron or silt in the pipes). It has been possible to perfect the bacteriostatic properties of the filter housing by using new technologies so that the filter counteracts retrograde contamination and biofilm formation throughout the entire period of use. Furthermore, the sterile filter ensures unlimited safe use thanks to its compact design and the laminar angled direction of the water jet.

As a manufacturer of medical devices, i3 Membrane has a quality management system that is certified in accordance with DIN EN ISO 13485; the company thus complies with the demanding requirements regarding the safety and reliability of its products and services and the minimization of the risks of its products. A complaint rate for products of less than 0.02 % confirms that the methods of development and manufacture are good.

Sterile filters for the reprocessing of medical devices

When reprocessing medical devices such as endoscopes that are used within the human body, high quality cleaning and disinfection are vital. Reprocessing must be carried out in accordance with DIN EN ISO 15883. The specifications for the quality of the water used for final rinsing need particular attention so that residues of cleaning and disinfectant solutions are removed as completely as possible from the exterior and interior of the endoscope. In their specifications for hygiene in the reprocessing of medical devices, the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch Institute (RKI) and the Federal Institute for Drugs and Medical Devices (BfArM) recommend the use of validated processes. They also provide details of threshold values for water quality to avoid the transmission of microorganisms on reprocessed endoscopes.

Reliable sterile filters for use on cleaning guns for rinsing medical devices (such as endoscopes) and inline filters as barriers on the inlet pipe of medical devices which use water (such as birth pools and cleaning and disinfection devices for endoscopes) provide additional support for infection prevention in medical establishments.


  • 16.08.2019

    Point of use sterile filters in everyday clinical practice: on risks and side effects

    In hospitals, withdrawal points for water represent a special interface between technical and hygienic requirements.

  • 05.06.2019

    On the paths of water-associated bacteria

    Examinations from numerous samplings show that clinics have a much higher excess frequency particular with Pseudomonas aeruginosa, than other public institutions.

  • 08.05.2019

    Modern and high quality separation technology

    i3 Membrane is quickly becoming a specialist in high-quality separation technology in the fields of medical care, biotechnology and environmental analysis.

  • 21.03.2019

    Where the many gram-negative germs in hospitals come from and why is it not just the water's fault?



¹ Recommendation by Deutsche Gesellschaft für Krankenhaushygiene: "Gesundheitliche Bedeutung, Prävention und Kontrolle Wasser-assoziierter Pseudomonas aeruginosa-Infektionen" in HYGIENE & MEDIZIN, 41. Jahrgang, Supplement 2, 2016, page 6

2 Recommendation by Deutsche Gesellschaft für Krankenhaushygiene: "Anforderungen an die Hygiene bei der medizinischen Versorgung von immunsupprimierten Patienten"

3 Recommendation by Deutsche Gesellschaft für Krankenhaushygiene: "Gesundheitliche Bedeutung, Prävention und Kontrolle Wasser-assoziierter Pseudomonas aeruginosa-Infektionen" in HYGIENE & MEDIZIN, 41. Jahrgang, Supplement 2, 2016, page 16

4 Zhou ZY, Hu BJ, Qin L, Lin YE, Watanabe H, Zhou Q, et al. Removal of waterborne pathogens from liver transplant unit water taps in prevention of healthcare-associated infections: a proposal for a cost-effective, proactive infection control strategy. Clin Microbiol Infect 2013,–0691.12299/abstract

Linking knowledge

i3 Membrane with headquarters in Germany and Austria links ion technology with membrane technology, thereby creating a new field of multifunctional and controllable separation techniques. In your capacity as a user of separation technologies, i3 Membrane supports you in developing your innovations in the areas of Life Science and Industry.

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