A Systems Approach to Modelling Chlorine Decay in Water Dis- Tribution Systems

Disinfectant concentration (i.e. mainly monochloramine and dichlo-ramine in the present case) at every point in a water distribution system is an important indicator of water quality. However chlorine decays in water due to reactions with various substances and thus possibly fails to disinfect the distribution system properly. In particular bioolm formed by bacteria on the walls of distribution system pipes may exhibit water quality problems due to greater resistance against chlorine. This paper gives an outline of two experiments designed for a 1.4 km long test rig aimed at establishing the relationships between chlorine decay in water and ow rate, initial chlorine concentration, or amount of bioolm present. The system under investigation is described with emphasis on processes related to water quality. The experimental setup and problems involved in collecting data in a system like this are discussed. Finally the goals, ideas, and a sketch of the design of the proposed experiments are presented and anticipated results of these experiments are given. The approach taken in this paper is inspired by systems science, viewing the test rig as a system of independent variables ((ow rate, initial disinfectant concentration), dependent variables (disinfectant residual, bioolm), and parameters (e.g. temperature , pipe material, source water quality, initial bioolm present) and their relationships .