Modeling the formation of disinfection byproducts in chlorinated swimming pool water: Role of body fluid analog

Abstract

The recirculation of pool water and the continuous input of pollutants and disinfectants in swimming pools intensifies the accumulation of disinfection byproducts (DBPs), which have received increasing attention. Trihalomethanes (THMs) are the most common DBPs found in swimming pool water. Developing a predictive THM model is an efficient and promising way to optimize the chlorine dosage and guarantee water safety. Because the main components of swimmer inputs and their respective quantities have been formalized and determined through body fluid analogs (BFA), the model development can rely on the chlorination of BFA components and mixtures. In this study, a well-established second-order reaction chlorine decay model with a variable reaction rate coefficient was expanded to describe the chlorine consumption in swimming pool water. The THM model with a variable formation coefficient was first developed based on the identical assumption of the chlorine model, that is, the reactivity of the reactants decreases as the reaction progresses. The results showed that uric acid exhibited the fastest initial rate coefficient for chlorine decay. Although citric acid showed a considerably high specific THM formation potential (μmol-THM, species/mg productive chlorine consumption), urea and humic acid (HA) were attributed to the fast-reacting THM formation precursors. The rate coefficients of urea and HA were higher than that of citric acid. For the mixture, the (overall) reaction rate coefficients were formulated as a function of the rate coefficient of the individual substance and the concentration of the substance remaining in the water. This concept was tested using BFA and BFA with HA. The model accurately described the chlorine consumption and THM concentrations (R2 > 0.96). HIGHLIGHTS BFA is more reactive than HA toward chlorine consumption.; HA results in more TCM formation than BFA does.; A variable reaction rate coefficient model for THM formation was developed.; The rate coefficient of mixtures depends on rate coefficient and concentration of individual substances.;

Keywords

• body fluid analog
• disinfection byproducts
• kinetics model
• swimming pool water