A universal model to predict DOC removal by coagulation based on UV-Visible absorption spectrum

Dissolved organic matter (DOM) universally present in drinking water reacts with chlorine-based disinfectants to form disinfection byproducts (DBPs) such as trihalomethanes (THMs), haloacetic acids (HAAs) and other potentially more toxic compounds. Given that DOM removal is the primary goal of drinking water treatment, establishing models to predict DOM removal by coagulation is crucial for intelligent control in drinking water treatment plants (DWTPs). However, due to the lack of online methods for characterizing DOM reactivity in coagulation, predicting its performance for various water sources and variations of applicable seasonal conditions remains a great challenge. This study demonstrates that while DOC removal exhibits significant variations, it is primarily determined by the maximum DOC concentration removable by coagulation (DOC_max), the alkalinity in source waters, and coagulant type and its dosage. The main finding of this study is that DOC_max can be determined based on the properties of absorbance Band A₃, identified as a deconvoluted Gaussian band within the Ultraviolet-Visible (UV-Vis) absorbance spectra of DOM, with the Band A₃ maximum near 350 nm (R² = 0.84). This result allows developing a universal model that accurately predicts, based on UV-Vis absorbance spectra of source waters, DOC removal by coagulation for a wide range of source conditions, alkalinity, and coagulant dosage (R² = 0.93). These insights can be used to develop smart dosing systems for control of coagulation in DWTPs.