Real-scale revitalization of a large water distribution system using combined hyperchlorination, cascade and neutralization strategies

Despite well-established water treatment methods, maintaining water quality in large and complex distribution networks remains a significant engineering challenge, particularly under rapid urban expansion that requires integration of new pipeline sections into existing infrastructure. This research focuses on the consolidation and reactivation of an idle, 12 km-long, 1,200 mm-diameter pipelines segments within the water supply network, prompted by the rapid expansion of suburban areas in the Municipality of Belgrade, Serbia. The primary goal of this work was to assess the efficacy of chlorination-based disinfection, including pre-cleaning, hyperchlorination, neutralization, and flushing. This study addresses the challenges and proposes solutions by implementing chlorination disinfection processes, gravity- and cascade-based design approaches, and monitoring residual chlorine levels at selected points within a large water distribution network to enable efficient neutralization of hyperchlorinated water. The treatment achieved residual chlorine levels of 0.15–0.35 mg/L, reduced turbidity to 1 nephelometric turbidity unit (NTU), and ensuring microbiologically safe potable water. The results confirm that the carefully designed neutralization strategy, which includes the use of sodium bisulfite, aeration, and a gravity cascade system, effectively meets microbiological standards.