Chlorate formation in water distribution systems: a modeling study

Chlorine-based disinfection agents are known to favor the production of Disinfection By-Products (DBPs), whose concentrations are restricted by international guidelines to ensure a safe consumption of drinking water. Hence, it is important to understand the behavior of DBPs within Water Distribution Networks (WDNs) to avoid users exposure to concentrations higher than guideline values. The buildup in chlorate concentration resulting from chlorinated disinfectants is here simulated with the EPANET 2.0 software for one benchmark WDN serving about 130,000 inhabitants. Chlorate generation was accounted by means of an empirical model, considering different boundary conditions (physic-chemical features of raw water, disinfectant dose). The gathered results indicate that increases in chlorate concentration within the considered WDN are narrow. Chlorate neo formation in the WDN is however strictly related to the initial amount of chlorate released by the WTP, i.e. to the input value in the WDN. If chlorate concentration in treatment plants is kept below 700 μg/L (i.e. WHO guideline), depending on the mixing conditions in tanks, the simulation results referred to the considered WDN show that the DBP buildup within the network is limited (in any case lower than 5-7% of the threshold value)