Numéro |
Cahiers de l'ASEES
Volume 12, Numéro 1, 2007
|
|
---|---|---|
Page(s) | 37 - 42 | |
DOI | https://doi.org/10.1051/asees/20071201037 | |
Publié en ligne | 27 septembre 2010 |
Traitements préventifs des Légionelles dans les installations d'eau sanitaire : Désinfection par ultraviolet C et Rétention par microfiltration à fibre creuse
Preventing Legionella in sanitary water installations: Disinfection by ultraviolet C and Retention by micro-filtration using hollow fibre
Comap SA, 16 avenue Paul Santy, 69008 Lyon
Les bactéries Légionelles, notamment la Legionella pneumophila, responsable de la maladie du Légionnaire, se développent dans des installations d'eaux chaudes sanitaires mal conçues et mal entretenues. Un traitement préventif de l'eau permet de minimiser le risque de la légionellose chez les usagers. La technologie ultraviolet C désactive ou détruit, selon les doses d'irradiation transmises, les Légionelles dans l'eau. La microfiltration à fibre creuse permet de retenir ces bactéries et constitue une sécurité supplémentaire.
Les produits de traitement d'eau basés sur ces deux technologies ont été testés au laboratoire avec des souches de bactéries Legionella pneumophila, l'expérimentation sur site réel confirme leur efficacité.
Abstract
Legionella bacteria, especially the Legionella pneumophila discovered in 1976 in the USA, are responsible of Legionnaire's disease. These bacteria are found in natural cold water in a dormant state. They are often parasitized inside other bigger bacteria, and are difficult to detect. Legionella bacteria become active and grow when the temperature rises, the optimal range of temperature for their proliferation is 25 °C-43 °C. But if the temperature continues to go upper than 60°C, the Legionella may not survive.
A sanitary water installation can create a favourable environment for Legionella's proliferation. The contamination used to occur in the installations which are badly dimensioned and maintained. In those cases, a preventive water treatment is recommended or even necessary in order to minimize the risk of Legionnaire's disease.
The ultraviolet C lights deactivate or destroy bacteria according to the irradiation dose received by the microorganism. It is possible to calculate the irradiation dose inside a cylindrical UV reactor. A computing programme has been developed as allows the dose's mapping with which input data: bactericidal power of the UVc lamp, water's transmittance, flow rate and construction features of the device (dimensioning, total number of lamps...).
Scientific studies have shown that a 5 log's reduction of Legionella pneumophila can be obtained with a dose of 8 mJ/cm2. A UVc treatment device designed for 25 mJ/cm2 (French regulation's value for drinking water treatment) has been tested. No matter the rate of Legionella pneumophila in inlet water (from 500 to 8 000 000 UFC/L), no bacterium is detectable in the outlet.
The micro-filtration technology stops particles including bacteria whose size is bigger than the mesh. A 0,1 µm filtration using hollow fibre material is suitable for removing Legionella in tap water. A micro-filtration at POU (point of use) offers an extra security for the consumer. The efficiency of such a device has been tested. Its performance is confirmed by the laboratory studies as well as the results of a field-test in a clinic's sanitary water installation.
© ASEES 2007