Some Aspects Concerning The Modelling Of Chlorine Residuals In Drinking Water Distribution Networks

Abstract

This paper deals with the modelling of chlorine residuals in drinking water distribution
networks (DWDNs) used for transportation of treated drinkable water from the water treating
plants to consumers. To kill the microorganisms that can cause the waterborne ills, disinfection
is usually the final treatment stage in the drinking water plants. The most common disinfectant
used in DWDNs is chlorine because it is inexpensive and effectively annihilates a variety of
disease-causing organisms. But disinfectant concentration in the water may decay during the
transportation, and bacteria growth cannot be controlled if disinfectant concentration is
lower than a certain level. As a result, the bacteria and waterborne pathogens may grow.
Microorganisms can also grow up on the pipe and tank walls as not all organisms are killed
in the water treatment plants. As a consequence, distribution network water quality control
is a very important problem. A solution is the regulation of chlorine residual concentration
within a prescribed set of bounds. Since the DWDNs are large scale systems with high uncertainties
and time varying delays, in order to obtain useful models for control, in this paper, some aspects
of modelling of chlorine residuals in these multiple-inputs, multiple-outputs complex systems are presented.
The equations of chlorine residual concentration dynamics in DWDNs are obtained based on the mass conservation
and reaction kinetics using the main aspects governing chlorine concentration in DWDNs: transportation,
mixing and decay caused by chlorine reactions.