La chloration continue en eau chaude sanitaire : un moyen de sécurisation efficace contre les légionelles

The continue chlorination in domestic hot water: an efficiency measure against Legionella

¹ VEOLIA Environnement - Centre de Recherche sur l’Eau, Chemin de la digue, BP 76, 78603 MAISONS-LAFFITTE - France
² Aquabellec - Direction des marchés tertiaires - MAUREPAS - France

Auteur de correspondance : fabienne.jacques@veolia.com

Résumé

Cet article présente les résultats obtenus au cours des études menées par Veolia Environnement en termes de sécurisation contre les légionelles des réseaux d’eau chaude sanitaire. Des essais laboratoire, en pilote et des suivis sur site ont permis de montrer que le traitement par chloration en continu permet de maîtriser immédiatement la contamination de la phase eau. Il représente une solution efficace, plus pérenne pour la tenue des canalisations et peut être considéré comme un traitement provisoire en l’attente d’une sécurisation de l’installation conforme à la réglementation.

Abstract

This article shows the results obtained by Veolia Environment on domestic hot water safety. Several experiments (laboratory, pilot scale, full scale installation) show that continuous chlorination (chemical treatment) allows to control Legionella contamination in water phase. It will be an efficient and durable solution for the pipes and could be considered as a provisional treatment until the safety of the installation. Efficiency of various disinfection treatments against Legionella were tested on a Hot Water Distribution System (HWDS) pilot unit. A large majority of Legionella in the networks were fixed in the biofilm at the surface of the pipe (more than 98% for each loop). Chemical treatment shock, commonly used for the eradication of Legionella in hot water distribution networks, appeared to be inadequate for eradicating the bacteria in the biofilm. Chlorination shock has a punctual effect on the water phase. The partial impact on the biofilm brings about a fast re-contamination of water phase by Legionella. The continuous chlorination seems less damaging for old networks in comparison to repeated chlorinated shocks which can accelerate the degradation. In many cases it is difficult to control Legionella risk during the modifications of the network to obtain a temperature > 50°C everywhere. The best solution is to apply continuous chlorination (in function of pipes characteristics). To be effective, this treatment must be automatically controlled and equipped with alarm systems.