Chlorine decay studies in water supply system

Water supplied to the public through municipal water works should be qualitatively good and quantitatively sufficient. It is important that the potability of water is maintained at the consumer end. The presence of residual chlorine is invariably considered as an indicator of water quality. The chlorine consumption rate, which is categorized into bulk and wall reactions, governs the chlorine dosage given at the treatment plant. Bulk water chlorine reactions are system specific as water quality significantly affects the chlorine decay. The variability of chlorine reaction rates in different water qualities, viz. raw, sand filtered and distributed water from a real life water works, is studied in the present work. The potential applicability of two popular models, such as first order and two-component second order to represent the bulk water chlorine reactions, is evaluated. The range of reaction rate parameters involved in these models is also determined and it will help the modeller to choose appropriate values of input parameters while simulating water quality. The initial chlorine concentration also affects the reaction rates. The reaction rate parameters vary inversely with the initial chlorine concentration. Further, the repeated rechlorination studies carried out on sand filtered water show the reduction in chlorine consuming power of water.