Modelling of chlorine decay in a portable water distribution network : case study of Kampala Distribution Network, Uganda

Abstract

The most expensive component of a water supply system is the distribution network. Proper understanding, characterization and prediction of water quality behavior in drinking water distribution systems are critical in meeting regulatory requirements and ensuring customer oriented expectations. Since chlorine content is one of the most important variables used to indicate water quality, special attention should be paid to its decay and factors influencing it in the distribution network. This study presented the behavior of residual chlorine using mathematical modeling for a section of the distribution network located in Kampala, Uganda. The purpose of this study was to investigate the variation in the concentration of residual chlorine and water quality in a section of the Kampala distribution network under prevailing distribution conditions and develop a tool that could be used to predict the concentration of residual chlorine in the selected distribution network. Sampling points were selected and residual chlorine concentration and water quality for each determined for a period of six months. The average physiochemical quality parameters of water for the two treatment plants were as follows, pH 7.21, electrical conductivity 144 µS/cm, turbidity 0.74 NTU, color 11PtCo, TSS of 1.0 mg/L, temperature of 24 C and residual chlorine of 0.42 mg/L. The study found that residue chlorine was detected at all sampling points. Results from the laboratory assessment of water quality indicated that the treated water at the Water Treatment Plants conformed to WHO guidelines for potable water. Results also showed that the kinetics of first order could adequately describe the behavior of residual chlorine in this type of network. This study proved that residual chlorine modeling in this section of the distribution network in particular was a valuable tool for monitoring the water quality in the distribution network, which was useful to comply with water quality guidelines.