PREVENTION OF BACTERIAL-GROWTH IN DRINKING-WATER DISTRIBUTION-SYSTEMS

Of the many causes of drinking water quality deterioration in distribu tion systems, biological phenomena are undoubtedly the subject of the most study. They are also the most closely monitored because of short- term public health risks. A determinist model was developed to predict bacterial growth in the network and to locate the zones where the ris ks of biological proliferation are the highest. The model takes into a ccount the growth of suspended and fixed bacteria, the consumption of available nutrients in the bulk water and in the biofilm layer, the in fluence of chlorine residual on the mortality of suspended and fixed b iomass, the deposition of suspended bacteria and the detachment of bio film cells, the influence of temperature on bacterial activity and chl orine decay. The model is constructed using hydraulic results previous ly generated by PICCOLO, the SAFEGE hydraulic computer model and a num erical scheme to predict bacterial count at each node and on each link of a network. The model provides an effective and easy way to visuali se on a computer screen variations in water quality in the network. Th e first model calibration was done using data obtained from a pipe loo p system pilot. A validation of the model has been carried out by mean s of measurement campaigns on various real networks. This predictive m odel of bacterial growth in distribution systems is a unique approach for the study, diagnosis and management of distributed water quality. This tool is helpful for proposing strategies for the management of di stribution systems and treatment plants and to define conditions and l ocations of high bacterial counts in relation to hydraulic conditions. (C) 1997 IAWQ. Published by Elsevier Science Ltd.