A simple system for estimating the biofilm formation potential of water: first experiments on slow-sand filtered water

The new european régulation spécifies that drinking water quality should now be assessed at the consumer's tap rather than at the outlet of treatment plants. So, it is very important for all drinking water producers and suppliers, whatever their analytical means are, to have efficient tools for the quantification of biofilms, so that they can detect problems and react as quickly as possible. Thus, on the basis of a previous european programme research, we developed and tested a simple and easily reproducible experimental procedure to assess the biofilm formation potential of waters. Sturdy stainless steel incubators, highly adapted to industrial field conditions and containing glass beads were designed to allow the biofilm formation and the measurement of technically basic parameters (HPC) or more complex parameters (Fixed Total Organic Carbon, fixed total bacteria). Such incubators were connected to a surface water after a slow sand filtration stage. The maximal quantities measured were lower than those typically reported in the literature: about 103/cm2 for HPC-R2A, 104/cm2 for total bacteria and 0.5 µg/cm2 for Fixed Total Organic Carbon (FTOC). A significant linear relationship exists between FTOC and total bacteria or HPC but it seems that the most part of FTOC is of extra-cellular origin. More generally, the resutts obtained validate the use of this type of incubators as a monitoring System which is a suitable tool for all potable water producers and suppliers