Détermination électrochimique de l'épaisseur des biofilms dans les circuits d'eau

Electrochemical determination of biofilm thickness in water sys- tems. Biofilms are growing on the internal wall of the water pipelines, this is a constant problem of health risk. The legionella which proliferate in the warm waters networks and in cooling towers, are at the origin of more than 1000 cases of Legionnaire's disease per year in France during the last three years, the death rate being about 14%. To control this bacterial development, a better understandingof biofilms ecology is necessary, in particular their growth and their composition. In this purpose, three working years of collaboration between the company Henkel Concorde and 2 CNRS research teams (UMR 6008 and UPR 15) allowed to develop a tool able to measure the biofilm thickness. On laboratory pilots and in industrial site, this biofilm thickness measurement showed a very acceptable reliability and sensitivity to follow the behaviour of a biofilm in a water circuit and to evaluate the efficiency of the treatments (dispersing, biocide) which are applied. The use of this tool allows to optimize the applied treatments (nature, dose, frequency of injection) and leads to a strong reduction of the sessile biomass. Thanks to this sensor the cleanliness of wa- ter circuits could be maintained with a better efficiency and thus a greater control of the legionella risk could be obtained.