Chlorine decay modeling in the S. Giacomo storage tank, Napoli

In the last years, the need for drinking water supply has been much increased; therefore, distribution systems are becoming more complex and together tied into interconnected networks in order to transfer water resources between different area services. Thus, a distribution network may be supplied by some resources, with different source and characteristics, which are mixing in the system; in this situation, water quality control appears to be a particularly relevant topic, which is increasingly studied using mathematical models that simulate transport and transformation phenomena along the various components of the drinking water network, such as the storage tank, which could be considered as a reactor, where water quality could be remarkably modified. The paper deals with chlorine decay modeling in the S.Giacomo storage tank, one of the most important of the distribution system of Naples. This tank has a volume of 60000 m³, which is divided into 6 units each one of 10000 m³; the S.Giacomo storage tank is supplied by two water resources with very different characteristics. The study has been performed applying a compartment model which predict chlorine concentration variation between inlet and outlet. The model is based on mass balance equation and on continuity equation, which are solved at finite difference with Euler method to yield chlorine concentration along the tank up to the outlet section. The tank has been subdivided into many compartments, but for the comparison data field were available only in inlet and outlet section of the tank. Furthermore, model equations have taken into consideration the particular inlet conditions, with two inflow pipes.