359 - Analysis of the Chlorine Decay and Trihalomethanes Growth Sensibility to Different Body and Wall Coefficients and Decay Models in Optimal Minimum Cost Water Distribution Networks

Chlorine and trihalomethane concentrations are two key aspects to control in Water Distribution Networks (WDNs) given their direct impact on the consumers health. Residual chlorine is usually added to WDNs to preserve the quality of the water that leaves the treatment plant. However, elevated concentrations of chlorine can react with the organic matter in the water and form compounds known as trihalomethanes (THMs), which are highly nocuous to the human health. Chlorine decay is usually modeled using first order kinetics, which relies on two coefficients to estimate chlorine levels across the network, namely bulk and wall coefficients. Nonetheless, first order kinetics have been identified by several authors to be inadequate to model chlorine decay given its general inaccuracy and problems to adapt to different scenarios, hence more complex decay models have been proposed. Minimum cost WDNs are distribution networks designed with optimization techniques, which are characterized by low water ages and thus low levels of chlorine decay. In this research, a theoretical approach is followed by using different first order coefficients reported on the literature and two additional models. The aim is to forecast chlorine decay on networks designed with optimization techniques to compare the decay rates predicted by the different models while simultaneously modeling THMs formation. Eleven networks were analyzed, including literature benchmark networks and real-life networks. It was found that even for high initial doses of residual chlorine optimized networks maintain low levels of THMs. However, the behavior of chlorine decay can differ greatly from one network to another, even when using the same decay coefficients.