Measurement of bacterial biomass and activity in tap water

Various methods have been investigated to estimate bacterial biomass and activity in tap water. For this study, the analyzed water samples have been collected in the distribution system of the Parisian suburbs. Three methods have been tested for the determination of bacterial biomass: plate count, measurement of DNA associated with particles with a size higher than 0.2 mu m and direct microscopic enumeration. On the basis of these tests, it seems that the direct count by epifluorescence microscopy is the most adapted method for studying the bacterial regrowth in distribution system.