Real-Time Monitoring of Dose Distribution and Simplified Indicators of Ultraviolet Reactors with a Buckingham-π Theorem-Based Dual MFSD System

Real-time monitoring of dose delivery is critical for ensuring reliable and energy-efficient ultraviolet (UV) disinfection. However, conventional methods are limited by high cost and inability to capture full dose distribution information. This study presents a novel, cost-effective approach for real-time monitoring of UV dose delivery (including dose distribution and simplified indicators) by integrating a dual microfluorescent silica detector (dual-MFSD) system with Buckingham-π theorem-based scaling. The dual-MFSD system enabled simultaneous and convenient monitoring of real-time water UV transmittance (<i>T</i>_RT), as well as a correction factor (<i>CF</i>_RT) accounting for lamp output attenuation and sleeve fouling, with an effective optical path-length difference calibrated as 1.01 cm. A dimensionless scaling method based on the Buckingham-π theorem was developed to predict full information of the UV dose distribution using real-time operating parameters (i.e., <i>T</i>_RT, flow rate (<i>Q</i>_RT), and <i>CF</i>_RT), allowing rapid calculation of simplified indicators. The predicted doses were validated by computational fluid dynamic (CFD) simulation and biodosimetry at various <i>T</i>_RT values (97% and 90%) and <i>Q</i>_RT values (40, 50, and 60 L min^-1) with a measured <i>CF</i>_RT (0.754). Additionally, a four-month field test was conducted in a secondary water supply system, demonstrating the practical applicability of this method. This study provides a real-time approach for UV dose monitoring, supporting reliable and energy-efficient UV disinfection.