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

Abstract

For microorganisms, 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 is safe to drink. This is due to the probable presence of pathogens inside the biofilm which may be spread in the water. To keep the water quality safe, sanitization processes are regularly carried out using oxidizing biocides which can alter the physico-chemical properties of the material. Due to their surface physico-chemical properties and their high corrosion resistance, stainless steels seem to be good candidates for the making of drinking water systems. In this 2 year study, stainless steel grades were compared with materials commonly used, in respect of fouling, biofilm development 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 pilot specially designed to assess the material biocontamination on a natural drinking water loop for more than 2 years. The results confirmed the significant impact of the material on the biofilm development in terms of formation kinetic and ecology. No differences were observed between stainless steel grades whereas they displayed an intermediate behaviour compared to other materials. Corrosion attacks were only observed on galvanised carbon steel while on stainless steels, negligible release rates, much below international health requirements were measured. So stainless steels offer a good compromise to make drinking water pipes.