AWWA JAW28840

To maintain the biological stability of drinking water during distribution in large, complex networks, high standards have to be met--namely, low bacterial densities and low levels of biodegradable organic carbon. Second-stage granular activated carbon (GAC) filtration (without regeneration of carbon) is used for this purpose at the Choisy-le-Roi, Paris, France, treatment plant. Effective removal of dissolved organic carbon has been observed with such filtration--mainly because of a reduction in the biodegradable organic carbon. To study the microbial processes involved in this removal, new methods based on the use of radio-labeled tracers have been developed in order to measure the bacterial biomass and activity associated with GAC. Includes 26 references, tables, figures.