Development of a Model of BDOC and Bacterial Biomass Fluctuations in Distribution Systems
On the basis of experimental microbiological studies performed on different french distribution systems, a model of the dynamics of bacteria and biodegradable dissolved organic carbon (BDOC) in distribution networks was developed (the SANCHO model). The following processes are taken into account in the model: exoenzymatic hydrolysis of dissolved organic matter by bacteria and growth of free and fixed bacteria on the hydrolysis products; bacterial mortality which releases organic matter; reversible adsorption of bacteria and their biological attachment to inner pipe surfaces, chemical consumption of free chlorine and impact of free chlorine on the activity of free and fixed bacteria. The kinetics of these processes were all studied experimentally. The model considers the case of a water body flowing down in successive pipes of decreasing diameters and calculates the spatial variations, at steady state, of BDOC and chlorine concentration, free and fixed biomass. The SANCHO model was validated by the comparison of calculated and experimental data on various distribution systems which work over a large range of conditions. Good agreement between calculated and measured values of chlorine, BDOC, suspended and fixed bacterial biomass was found for the different distribution networks. This model can be used to define the water quality required at the outlet of a given treatment plant in order to avoid problems of bacterial growth within the distribution system fed by this plant. Keywords .