Fate and transport of chlorine dioxide: Modeling chlorine dioxide in water distribution systems

This study aims to conduct a comprehensive analysis of switching disinfectants from sodium hypochlorite bleach to chlorine dioxide (ClO₂) in the water distribution system of Geyikbayiri, Antalya. For this purpose, bulk decay rates of ClO₂ at various water temperatures were determined in laboratory studies. The study revealed ClO₂ bulk decay rates of 0.12639 day^-1, 0.17848 day^-1, and 0.19621 day^-1 at temperatures 15°C, 20°C, and 30°C, respectively. The EPANET, a widely employed computer program for simulating the extended-period behavior of hydraulic and water quality in pressurized pipes, was utilized for the analysis of the fate and transport of ClO₂. A hydraulic model was first developed, calibrated, and verified using distinct data sets. The Hazen-Williams friction coefficient of the PSA was determined to be 120 by the trial-and-error method with a mean absolute error (MAE) of 0.408 m. A ClO₂ model was then integrated with the calibrated and verified hydraulic model, revealing a wall decay rate of 0.01 m/day and an average MAE of 0.034 mg/l. After calibration and verification of the ClO₂ model, several management scenarios were developed, and ClO₂ dosing rates were determined. The study showed that ClO₂ dosing rates of 0.40 mg/l and 0.45 mg/l should be applied to keep ClO₂ concentrations within certain limits. PRACTITIONER POINTS: Disinfectants must maintain a sufficient residual in water distribution systems. Chlorine dioxide requires less contact time and is not affected by pH fluctuations. Modeling serves as a decision-making tool for the management of disinfectants. Bulk and wall decay rates of chlorine dioxide are crucial for management strategies. Chlorine dioxide is a good alternative as a disinfectant in such systems.