Material durability and biofilm development in drinking water network – Comparison of stainless steel grades with commonly used materials

摘要

For micro-organisms, the preferred living state is adhering to surfaces that can lead to the development of a biofilm. In drinking water networks, a biofilm can affect the organoleptic quality of the water as well as whether it’s safe to drink. This is due to the probable presence of pathogens inside the biofilm which may be spread in the water. Furthermore, by locally modifying the environment in terms of pH, RedOx potential or by secreting corrosive species, biofilms can induce changes on the surface of material, sometimes causing degradation.It is well known that some materials are really prone to fouling and biofilm development while others, which are less sensitive to fouling, suffer from general corrosion leading to a non negligible ion release.The aim of this work was to compare the behaviour of stainless steel grades with materials commonly used in drinking water networks in terms of biofouling and corrosion resistance.The tested stainless steels included 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 materials used for comparison were copper, galvanised steel, polyethylene and cement. The experiments were performed in a pilot specially designed to assess the material biocontamination on a natural drinking water loop for more than 2 years.The results evidence that even after a 2-year exposure biofilms are still dynamic systems leading to the modifications of the biofilm structure and composition with time. These modifications could be the source of the evolution of Open Circuit Potential (OCP). Evidence of neither free chlorine content variation nor localized corrosion on stainless steels was found. Corrosion attacks were only observed on galvanised carbon steel. While for stainless steels, negligible release rates, much below international health requirements were measured. So stainless steels are good candidates to make drinking water pipes.