A multi-analytical approach to investigate DOM dynamics and alum dose control in enhanced coagulation process using wide-ranging surface waters

In this study, enhanced coagulation (EnC) - as a recommended water treatment process for disinfection by-product control - was investigated using jar testing, multi-analytical techniques, and a wide range of surface water sources. In addition to commonly used dissolved organic matter (DOM) concentration indices, DOM characteristics using UV-Vis spectroscopy, fluorescence EEM (fEEM) data, high-performance size exclusion chromatography (HPSEC), as well as turbidity, zeta potential and chlorophyll-a were studied. The results showed similar removal trends for the DOC, A(254) and fluorescent DOM (fDOMs) signals with increasing alum dosing. Absorbance at similar to 230 nm and fEEM data near Peak C in raw waters showed the highest correlations with enhanced dose. A decrease in weight-average apparent molecular weight following EnC, and a higher coagulability of DOM fractions with higher molecular weight, was noticed. The optimum zeta potential window was found to be 13 to +4 mV for EnC. Charge neutralization is suggested as the dominant mechanism for the EnC process. In addition to providing comprehensive information on the DOM dynamics during the EnC process, this study helps assess the potential of different water quality analysis techniques for EnC process monitoring and alum dose control, particularly using a field-deployable fDOM probe, offering potential for online, real-time applications.

Automated summary

This study investigated the application of enhanced coagulation (EnC) as a water treatment process for disinfection by-product control. Various analytical techniques were used to study dissolved organic matter (DOM) characteristics and the removal trends of different parameters with increasing alum dosing. The results showed that absorbance at around 230 nm and fluorescence EEM data near Peak C had the highest correlations with enhanced dose. The study also assessed the potential of different water quality analysis techniques for EnC process monitoring and alum dose control.