Integrated fluorescence assessment of organic matter through seasonal source-water changes

Abstract

Abstract

Dissolved organic matter (DOM) in surface-water sources exhibits seasonal and hydrologically driven variability that can influence treatment performance and disinfection by-product formation in drinking water systems. In this study, fluorescence excitation and emission matrix (EEM) spectroscopy combined with PARAFAC modeling was used to characterize fluorescent DOM (fDOM) dynamics at a full-scale drinking water treatment plant (DWTP) over a one-year time period. Four fluorescent components were identified, including two humic-like components (C1, C2), a tyrosine-like component (C3), and a petroleum-associated component (C4). Humic-like components dominated influent waters and were preferentially removed through coagulation, flocculation, and sedimentation, consistent with concurrent reductions in UV 254 , DOC, and SUVA. Seasonal increases in fluorescence intensity, particularly during summer, coincided with elevated DOC and aromaticity attributed to warmer conditions and greater contributions of lake water in the source blend, which is comprised of two surfaces waters (river and lake). While the overall fDOM composition remained relatively stable, the petroleum-associated component (C4) appeared episodically during summer rainfall events and exhibited an inverse relationship with humic-like components, suggesting stormwater-driven watershed inputs. In contrast, the protein-like component (C3) remained comparatively stable but increased in relative abundance following conventional DWTP treatment due to preferential humic removal. These findings demonstrate the utility of fluorescence spectroscopy for resolving seasonal and event-driven variability in DOM character and underscore the need to further investigate petroleum-derived contributions to source water.