Optimizing chlorine decay factors in intermittent water supply using box-behnken design

Abstract

Chlorine decay in water distribution systems is a critical challenge that impacts disinfection efficiency and public health. Using the Box-Behnken Design this study systematically investigates the effects of pH, flow rate, pipe length, and stagnation time on chlorine residual loss through a controlled experimental framework and optimize them to maintain acceptable residual chlorine. Analysis of Variance (ANOVA) was performed and revealed that pH and stagnation time were the most significant factors. Lower pH less than 7 and longer stagnation of over 2 hours accelerated chlorine decay by up to 40%. Flow rate showed a secondary but notable effect, where higher velocities (1.0 L/min) reduced decay by 15 to 20%. A quadratic model (R^² = 0.98) demonstrated strong predictive accuracy and revealed key interactions between initial chlorine dose and pH. At optimized conditions, a target residual chlorine level of 0.34 mg/L was achieved, balancing disinfection and operational efficiency. This study offers a vital strategy for utilities to mitigate the public health risks associated with inadequate disinfection in distribution networks.