Suitability of Chlorine Bulk Decay Models for Planning and Management of Water Distribution Systems

Abstract

Effective disinfection planning and management in large, complex water distribution systems requires an accurate network water quality model. This model should be based on reaction kinetics, which describes disinfectant loss from bulk water over time, within experimental error. Models in the literature were reviewed for their ability to meet this requirement in real networks. Essential features were identified as accuracy, simplicity, computational efficiency, and ability to describe consistently the effects of initial chlorine dose, temperature variation, and successive rechlorinations. A reaction scheme of two organic constituents reacting with free chlorine was found to be necessary and sufficient to provide the required features. Recent release of the multispecies extension (MSX) to EPANET and MWH Soft's H2OMap Water MSX network software enables users to implement this and other multiple-reactant bulk decay models in real system simulations.

KEY WORDS:

• chlorine decay
• kinetic model
• bulk water
• distribution system
• network

ACKNOWLEDGMENTS

Some of the ideas and models included in this article were developed by the authors as a contribution to the distribution system research program of the Australian Cooperative Research Centre for Water Quality and Treatment, when they were members of Sydney Water Corporation's R&D team.

Notes

This distinction between fitted parameters, such as a decay coefficient, and directly measurable values, such as initial chlorine concentration, is maintained throughout this paper.