Dans le cadre de l’eau et la santé en milieu hospitalier, une étude sur les matériaux, réalisée au Crecep, a permis de quantifier l’aptitude de six matériaux, utilisés dans des installations de distribution d’eau, à promouvoir la croissance microbienne.

Cette méthode se base sur la détermination en biomasse active dans la phase eau et sur le matériau par dosage de l’ATP microbien. Deux températures ont été utilisées, à 30 °C et à 50 °C, ainsi qu’une durée totale d’expérience de 16 semaines, avec des dosages intermédiaires à 8 et 12 semaines. Les matériaux utilisés sont : le cuivre, l’acier inoxydable (deux types), le C-PVC, le polybuthène et le polypropylène.

A European draft test method for determining the microbial growth facilitating properties of materials, in contact with water intended for human consumption, has been developed. This method, or BPP test, is based on a combination of two principles : determination of the active biomass concentration with ATP analysis and semi-dynamic test conditions, with replacement of the test water once a week.

The ability of six materials to enhance the production of biomass was studied. These materials (copper, C-PVC, stainless steels, polybutene and polypropylene) were investigated at two temperatures, 30 °C and 50 °C. Representative samples of these materials were incubated in tap water over a period of 16 weeks. The test water was initially inoculated with a mixture of naturally occurring micro-organisms derived from the Seine river. It was replaced once a week. ATP measurements were carried out on days 56, 84 and 112.

The net BPP values (corrected for the effect of the water) clearly show differences between materials. The biomass production appears to be related to the nature of the materials and to its incubation temperature. With some of the materials (metallic and synthetic products), a very slow microbial growth support potential was observed. With others, a thin biofilm was produced. Temperature has an impact on the growth potential with high BPP values at 50 °C in most of the cases. Increasing temperature may accelerate biodegradability. It may also enhance the release of biodegradable compounds from materials or lead to alternative biofilm properties.

This study has been conducted on unused materials during a short contact time. Thus, the ageing of materials, the effect of corrosion or fouling and the impact of various disinfection treatments have not been taken into account. Further investigations should be conducted to confirm the microbial enhancing properties of these materials in practical conditions.