BIOLOGICAL STABILITY OF DRINKING-WATER IN THE CITY OF METZ DISTRIBUTION-SYSTEM

This study was designed to monitor the water quality in summer and win ter in a sector of the drinking-water distribution system served by th e Metz water treatment plant in the city of Metz, The sampling strateg y chosen consisted of measuring three groups of parameters related to biomass, organic matter and residual oxidant concentration, The analys es carried out in 1989-91 on drinking water from the treatment system show that organic matter, micro-organisms and free residual chlorine a re always present, There was a significant rise in the biodegradable f raction of the treated water in summer which suggests that mains water is not biologically stable, Consequently there was a proliferation of micro-organisms in the system to the detriment of biodegradable organ ic matter (often called regrowth), particularly as bacteria use the di stribution system as a colonisable niche, The breakdown of the Metz wa ter distribution system into zones depending on residual chlorine show s a constant structure in spatial heterogeneity, Chlorine did not real ly control water stability during transport, Biological stability undo ubtedly depends on controlling both organic matter, the flux of enteri ng bacteria and post-disinfection.