Kinetics of THM Species in Finished Drinking Water

Abstract

The U.S. Safe Drinking Water Act and its amendments impose restrictive rules for filtration of surface water and maximum contaminant levels for total trihalomethanes (THMs) in distribution systems. Extension of these regulations can potentially address the possibility of limiting each individual THM compound since the health risks associated with these compounds are not all alike. Current models of THMs are predicated on empirical reaction kinetic equations derived from linear and nonlinear multiregression analysis. This paper applies nonlinear optimization to model the kinetics of THM species under representative extreme conditions. The proposed approach combines site-specific trends with stoichiometric expressions based on average representative bromine content factors. The model was tested and validated using data from finished (desalinated) water collected in the United Arab Emirates. Reasonable agreements between model-predicted and measured values of different species were consistently obtained, indicating the applicability of the approach with a full dynamic water-quality transport model. This model can lead to improved management of water quality and assist utilities in attempting to optimize chlorine disinfection practices in water distribution systems.