AWWA QTC97178

It has been recognized that the biochemical parameters of treated water are not necessarily constant as water moves through the distribution system, resulting in a certain degree of water quality deterioration. One important aspect of this deterioration is the unwanted growth of bacteria. In order to achieve biologically stable water, disinfectants can be added or the concentration of biodegradable organic matter (BOM) can be reduced. As heterotrophic bacteria are a significant portion of the microbial population of most distribution system biofilms, removing organic matter, specifically BOM, is conceptually a superior approach to achieving biologically stable water. The objectives of the bench-scale experiments described in this paper were to examine the heterotrophic plate count-supporting characteristics of different supporting surfaces (substrata) both for a surface and a groundwater at varying levels of chlorine and chloramine residual. For the surface water, the impact of biological filtration on regrowth potential was also assessed.