Numéro |
Cahiers de l'ASEES
Volume 13, Numéro 1, 2008
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Page(s) | 17 - 23 | |
DOI | https://doi.org/10.1051/asees/20081301017 | |
Publié en ligne | 23 septembre 2010 |
Sécurisation des réseaux d'eau chaude sanitaire. Les tendances actuelles
Sanitary hot water systems securisation - the current trends
CSTB Division Eaux et Bâtiments 84 avenue Jean Jaurès Champs sur Marne 77447 Marne la Vallée Cedex 2
La mise en conformité des installations de distribution d'eaux chaudes sanitaires afin d'y assurer une bonne circulation de l'eau ainsi qu'une température suffisante en tout point est reconnu comme étant la première des choses à faire pour lutter contre les développements bactériens. Ceci n'exclut pas, en situation de crise, ou lorsque le réseau ne se prête pas aux modifications essentielles, de faire appel à des procédés de traitement sanitaire, ou des procédés de lutte contre la prolifération des légionelles. Ces traitements nécessitent un suivi soigné de la mise en oeuvre et de la maintenance, car ils doivent en permanence éviter des teneurs en bactéries dépassant les seuils prescrits, malgré la présence inévitable de biofilms sur les parois internes des canalisations.
Fort de son expérience dans le domaine du traitement de l'eau et en lien avec les professionnels du secteur, le CSTB a développé plusieurs évaluations afin d'accompagner les acteurs des réseaux d'eau dans les bâtiments. Ceci commence par la certification de diagnostic, validant ainsi les prestations de diagnostiqueurs appelés pour faire un état des lieux et éventuellement recommander des mises en conformité des installations. Les Avis techniques vont apprécier la validité d'un procédé de traitement sanitaire et/ou de lutte contre la prolifération des légionelles. La certification CSTBat Service démontrera l'aptitude de celui qui met en oeuvre le procédé à le faire conformément aux prescriptions décrites dans l'Avis Technique, aux règles de l'art ainsi qu'à la réglementation. Ces évaluations sont évolutives en fonction de l'avancement des techniques, de l'apparition d'alternatives à l'injection de produits chimiques et des recherches qui s'attachent actuellement à étudier l'interaction entre procédés de traitement anticorrosion et procédés de lutte contre la prolifération des légionelles.
Abstract
It is now demonstrated that the bad functioning of a water system is directly responsible for bacterial growth. This one finds its origin in a bad design or in modifications made after putting the installation into service or else in the system ageing (scaling, corrosion). Therefore, the first action to have in mind to bring under control the risk of bacterial growth and more particularly legionella growth is to put the system into conformity with professional rules and to ensure a good functioning. In order to help owners and managers to identify correctly their system condition and the risks it can induce to the users, diagnoses are organised. But a diagnosis is only valid if it is carried out by a competent person. It is why a reference document has been written by a working group gathering around CSTB experts, ministery of health, contractors, managers and diagnosis actors representatives. The result was the creation of certification for water systems diagnosis, now operating.
In parallel and waiting to put the systems in conformity with hydraulic specifications, the manager or the owner can decide to start a sanitization process, or a process for prevention of legionella proliferation, or both successively. These processes are based on products authorised by Health Ministry and their use as well as their technical monitoring can be assessed by a Technical Agreement procedure, based on specifications given by a specialised technical guide. A service certification, in addition to Technical Agreements, attests the conformity with technical specifications in terms of installation, putting into service and maintenance. The first processes to appear were injection of chlorinated products or injection of products containing hydrogen peroxide stabilised with silver salts. Other processes, an alternative to these products injection, develop on the market and are subject to applications to CSTB evaluation. Even thermal processes, better known and authorised, have been evaluated and one of them has got a Technical Agreement.
From one process of chemical products to the other, the nature of used product changes, but also the nature of regulation and dosing system. Injections driven by a dosing pump controlled by an emitting signals water meter can be seen as well as injections driven by two dosing pumps controlled by sensors (conductivity, free chlorine content).
Sanitary hot water systems are already subject, for some of them, to water treatments used to fight against corrosion and/or scaling. Cohabitation of these treatments with sanitization ones complicate systems operating. On one hand, introducing oxidising agents increases the risk of pathologies due to corrosion, mainly in galvanised steel systems. On the other hand, the presence of anticorrosion treatments can influence the result expected with sanitization products injection. Field experiments, on which Technical Agreements are based, show that encouraging results are obtained as well as with separated injection of two product types than with the injection of only one product combining two active ingredients. To complement these first observations, a study is in progress at CSTB. It will be based on a pilot and will have the aim of bringing out the parameters which will allow the validation of compatibility of products between themselves and with materials.
The different points of this improvement of systems with the goal of a better sanitary safety for users show that various trends appear today. The processes evaluation, essential to insure their validity, is subject to adaptations in order to follow the evolution of knowledge, practice and regulations. However, new questions are raised. Amongst them, the effect of corrosion inhibitors injection on bacterial growth or also the alternative to chemical products brought by other techniques.
© ASEES 2008