Microfiltration in hospitals

June 2015

Microfiltration delivering bacteriologically controlled water

Every day a healthcare facility consumes about 300 litres of water per patient, more than twice that of an individual in everyday life. Distributing good quality water is therefore vitally important.

Monitoring the bacteriological quality of water in sanitary facilities in healthcare installations is essential. More recently the need to monitor water quality has extended beyond hospitals and care homes, and applies more widely to all public buildings.

Water-related risks

Within healthcare facilities, water contamination by microorganisms is common. Water acts as a vehicle for pathogenic agents such as faecal microorganisms e.g. Salmonella and enteroviruses, which are generally found in the public water supply. These microorganisms can also be opportunistic germs such as Legionella which develop in hot water systems or germs that thrive in hospital environments which frequently contaminate stagnant water (e.g. dead legs, pipework extremities and tap aerators) such as Pseudomonas and Aeromonas.

Delivering bacteriologically controlled water

The different uses of water by the care services has led to three levels of microbiologically controlled water being identified.

Level 1 - "clean water"  - intended for hand washing all uses in clinical care services. The water is delivered through non-sterile terminal filters.

Level 2 - "ultra-clean water" - intended for protected areas such as burns units, reconstructive surgery units, rinsing endoscopes and surgical hand washing. The water is delivered through sterile terminal filters.

Level 3 relates to sterile water used for rinsing certain materials in humidifiers and for creating aerosols.

Controlling the microbiological quality of water is essential to ensure that the quality criteria for Levels 1 and 2 are met. This need justifies the implementation of a quality procedure which involves microbiological monitoring of the water, the treatment process, the maintenance and servicing procedures and the distribution system.

The performance of the treatment process used to reduce the level of contamination is linked to the service and maintenance of these systems. When these procedures are followed, these treatments must provide water that is continually bacteriologically controlled to Level 1 or 2 quality.

Hollow fibre, an innovative technical solution

Microfiltration at the point-of-use is the most effective treatment at the point-of-use to provide level 2 quality water (“ultra-clean” water). There are two types of membrane filtration for point-of-use filtration, flat or hollow fibre membranes.

DELABIE has chosen the most recent technology for its range of BIOFIL micro filters – hollow fibre membrane filtration.

Developed in the 1970s, this membrane technology is recognised as the most effective for water purification. It includes applications up to ultrafiltration (0.001 microns) in many sectors including domestic, medical and industrial.

Each BIOFIL filter has an integrated polyethylene hollow fibre membrane with a water filtration threshold of 0.1 micron absolute-rated. The hollow fibre membrane has multiple pores which vary in size from 0.01 – 0.1 micron. The water requiring treatment passes through the filter due to the pressure difference on either side of the membrane. Bacteria and any particles in suspension larger than 0.1 microns are retained permanently on the external surface of the membrane.

The large filtration surface area compared to filters with flat membranes (1,400cm² compared to approximately 500cm²) means that a larger volume of water can be filtered. As a result, the storage capacity for bacteria and impurities is also much greater, slowing the clogging of filters and increasing their lifespan. BIOFIL anti-bacterial filters are very compact and are suitable for all types of mixers and taps.

DELABIE offers a complete range of single-use water filters – BIOFIL cartridges, shower heads and spouts. BIOFIL all-germ anti-bacterial filters can be used for up to 62 days after initial installation. All models are subject to numerous quality control checks with optimal traceability to control the health risk fully.


The Health and Safety Executive (HSE) guidance for the control of legionella bacteria in hot and cold water systems states that monitoring for Legionella should be carried where there is a doubt about the efficacy of the control regime or where the recommended temperatures, disinfectant concentrations or other precautions are not consistently achieved throughout the system.

In all buildings where the Health and Safety at Work Act (1974) applies, the frequency of testing should be determined by a risk assessment, the guidance suggests for example:

- Testing should be monthly when water is treated with biocides or distribution temperatures are reduced from HSE guidelines.
- Testing should be weekly where water treatment regime control levels are not being consistently achieved.
- Where there is a high-risk of contamination e.g. hospitals and care homes, sampling should be undertaken every six months if results are satisfactory.

(Source: HSG 274 Part 2, 2014; HTM 04-01 Part B, 2016).