Assessment of Current Models Ability to Describe Chlorine Decay and Appraisal of Water Spectroscopic Data as Model Inputs

Chlorine decay modeling in drinking water transport and distribution systems is a major tool for the management of disinfectant concentration. For such purposes, the models to be used in water quality simulators must describe chlorine decay in the systems as accurately as possible, requiring a minimum number of parameters and still be sufficiently robust to predict chlorine residuals under changing operational conditions. In this paper, two second-order decay models (single reactant and two reactants) were examined for their ability to predict chlorine residuals in surface raw and treated waters at a range of initial chlorine and natural organic matter concentrations. The two reactants model is necessary for chlorine residuals prediction in raw waters. However, for treated waters it only performed marginally better than the simpler single reactant model, with half the number of parameters that needed to be estimated. In addition, correlations were observed between both models parameters for reactive natural organic matter (NOM) concentration and measured fluorescence and ultraviolet (UV) spectroscopic data associated with humic-like compounds. Such findings are likely to open the door for a more exact determination of the models’ parameters and, thus, for improving the chlorine decay models’ adequacy and accuracy.