Modelling chlorine decay in drinking water distribution system supplied with mixed waters of various origins and qualities

摘要

In order to control the risk of bacterial contamination in drinking water distribution systems,disinfectant is generally injected at the production point to ensure a sufficient residualthroughout the distribution system. In doing this, disinfection must be kept at a minimum rateto limit the formation of disinfectant by-products. This trade-off is even more complex to dealwith, when a network is supplied with mixed waters of various qualities. There is anincreasing tendency to choose multi-source mixing within a distribution system for hydraulic,water-quality or economical reasons.The aim of this study is to evaluate the impact of mixing waters of various origins on thedistributed water quality. To study this issue, the network of the City of Caen in Normandy(114 000 inhabitants), France was chosen because one of its distribution areas is supplied withtwo types of water of various origins and qualities: a treated surface water and a chlorinatedground water. The hydraulic modelling software SynerGEE Water was used for this study tomodel the chlorine decay. This paper addresses the methodology and the results of winter andsummer field tests which permitted the modelling of the chlorine residual. It shows how aninnovative method has been developed and successfully applied to a complex distributionsystem to help the network operator optimize the disinfection strategy.