A long term study on biofilm development in drinking water distribution system: comparison of stainless steel grades with commonly used materials

EPI, ZI du Parc, 42490 Fraisses, FranceKey words:Drinking water; stainless steel;copper; cement; galvanisedcarbon steel; polyethylene;durability; biofilm; corrosion;scalingAbstract – For microorganisms, the preferred living state is adhering to surfaces that canlead to the development of a biofilm. In drinking water networks, a biofilm can affect theorganoleptic quality of the water as well as whether it is safe to drink. This is due to theprobable presence of pathogens inside the biofilm which may be spread in the water. Tokeep the water quality safe, sanitization processes are regularly carried out using oxidizingbiocides which can alter the physico-chemical properties of the material. Due to their sur-face physico-chemical properties and their high corrosion resistance, stainless steels seem tobe good candidates for the making of drinking water systems. In this 2 year study, stainlesssteel grades were compared with materials commonly used, in respect of fouling, biofilmdevelopment and composition. The tested stainless steels include ferritic (444/EN 1.4521),three austenitic (304L/EN 1.4307, 316L/EN 1.4404, and 316LN/EN 1.4429) and two duplex(2304 /EN 1.4362, and 2205/EN 1.4462) grades. The experiments were performed in a pi-lot specially designed to assess the material biocontamination on a natural drinking waterloop for more than 2 years. The results confirmed the significant impact of the material onthe biofilm development in terms of formation kinetic and ecology. No differences wereobserved between stainless steel grades whereas they displayed an intermediate behaviourcompared to other materials. Corrosion attacks were only observed on galvanised carbonsteel while on stainless steels, negligible release rates, much below international health re-quirements were measured. So stainless steels offer a good compromise to make drinkingwater pipes.Mots-cles :Eau potable ; acier inoxydable ;cuivre ; ciment ; acier galvanise ;polyethylene ; durabilite ; biofilm ;corrosion ; entartrageReceived 21 September 2011Accepted 12 October 2011Resume – Etude a long terme du developpement de biofilms dans les systemesde distribution d’eau potable : comparaison de nuances d’acier inoxydable avecd’autres materiaux couramment utilises. Les micro organismes vivent preferentielle-ment a l’etat adherent aux surfaces, ce qui peut conduire a la formation de biofilms. Dansles reseaux d’eau potable, un biofilm peut non seulement alterer les qualites organolep-tiques de l’eau mais egalement sa potabilite. Ceci, en raison d’agents pat hogenes poten-tiellement presents dans le biofilm et pouvantetre dissemines dans l’eau. Afin de preserverla salubrite de l’eau, des traitements de desinfection sont regulierement realises avec desagents oxydants susceptibles de modifier les proprietes physico-chimiques des materiaux.En raison de leurs proprietes physico-chimiques de surface et de leur excellente resistancea la corrosion, les aciers inoxydables semblent etre de bons candidats pour la conceptiondes systemes de distribution d’eau potable. Pendant 2 ans, le comportement de differentesnuances d’acier inoxydable a ete etudie et compare avec des materiaux couramment uti-lises sur le plan de l’encrassement, du developpement et de la composition des biofilms.Les aciers inoxydables testes comprennent une nuance ferritique (444/EN 1.4521), trois aus-tenitiques (304L/EN 1.4307, 316L/EN 1.4404 et 316LN/EN 1.4429) et deux duplex (2304 /EN1.4362 et 2205/EN 1.4462). Les essais ont ete realises sur un pilote specialement concu pourcette etude et representatif d’une boucle d’eau naturelle permettant d’evaluer la biocon-tamination des materiaux pendant plus de 2 ans. Les resultats obtenus confirment l’impact