WATER QUALITY ANALYSIS IN NETWORK AND PRIVATE STORAGE TANKS IN INTERMITTENT DISTRIBUTION SYSTEMS

In countries suffering from chronic water shortages, water distribution systems are often operated on an intermittent basis. As a consequence, the network is involved by cyclical filling and emptying periods causing water quality degradation. During the emptying period, the distribution system is unpressurised and it may occur that pollutants move into the network. Moreover, the stagnation period can promote microbial growth. For this reason water is usually heavily chlorinated in order to maintain it potable. Due to intermittent water service users acquire private tanks, which are used for collecting water during serviced periods and distributing it when public service is not available. The tanks can greatly affect water quality and safety. The present paper aims to assess the water quality variation in a complex hydraulic system such as an intermittent distribution network with private tanks. The water quality parameters, such as residual chlorine concentration, were evaluated inside the network and at the point-of-use, downstream of the private tank, in order to evaluate the fate of disinfectants in the network and the potential risk for the users. A network simulation model was implemented, taking into account the private tanks filling and emptying process. The model was applied to one district in Palermo distribution network (Italy) where data were available both at the tap and in the network.