Modelling drinking water chlorination at the Breakpoint: II. Calculation of the chlorine and chloramine concentrations along municipal pipe

Abstract

This study is focused on the determination of added chlorine dose in low ammoniacal concentration contained in distribution pipe of drinking water. The chlorine concentration in disinfected water varies between events of lack and excess that must be regularly controlled. The chlorine transport from the inlet to the outlet of pipe is carried out in turbulent flow where the phenomena of diffusion and convection are in charge to convey chlorine and chloramines formed along the polyvinylchloride pipe. The chlorine decay is principally due to ammonia consumption in the water bulk. The chlorine demand serves to generate inorganic chloramines and the formation of an uncertain intermediate, which helps to destruct them, and the reactions series of formation-destruction are referring to Breakpoint chlorination. The set of presented reactions at Breakpoint chlorination are not clear and the observed rate constants are not similar in the researchers found in the literature. Then, their choices are not easy because they cause large differences between the experimental profiles of disinfectants concentrations taken from literature and the predicted profiles of disinfectant concentrations investigated in the present paper. The set of differential equations are resolved simultaneously by the method of finite differences. Therefore the concentrations of free residual chlorine, ammonia, monochloramine, dichloramine, trichloramine, nitrogen hydroxide and total chlorine are calculated at different points constituted the municipal pipe.

Keywords:

• Chlorination
• Bulk decay
• Observed rate constants
• Modelling
• Equation transports

Acknowledgments

We thank Pr S. Samra for the revision and the correction of the present work.