Monitoring DOM in drinking water supply systems using DOC, CODMn, UV and fluorescence measurements

Abstract

Dissolved organic matter (DOM) has detrimental effects on drinking water treatment, distribution water quality and human health. In this study, four methods (dissolved organic carbon (DOC), potassium permanganate index (COD_Mn), ultraviolet (UV) absorbance and fluorescence excitation emission matrix (EEM) spectroscopy measurements) were utilized to investigate the spatiotemporal variations in DOM in two conventional drinking water supply systems (DWSSs) for the purpose of assessing the applicability of various technologies for DOM monitoring. Results showed that in the water samples, DOM was dominated by hydrophilic and low molecular weight substances. The fluorescent fraction of DOM was composed of humic-like components C1 and C2 and protein-like component C3, and was mainly from autochthonous sources. DOC, COD_Mn, UV absorbance and DOM fluorescence exhibited identical behavior, with high values in the raw water, decreased levels in the treated finished water and no significant changes during distribution. The order of removal efficiency in the drinking water treatment was fluorescence > UV absorbance > COD_Mn > DOC. Among the analyzed spectral parameters, UV absorbance at 270 nm (UV₂₇₀) exhibited the best correlation with COD_Mn, a standard regulatory measurement. The findings suggest that fluorescence EEM spectroscopy is a sensitive tool for assessing the DOM removal efficiency of drinking water treatment and that UV₂₇₀ may be used as a surrogate for COD_Mn for monitoring DOM levels in DWSSs. This study highlights the importance of combining multiple techniques for DOM monitoring, and enhances the understanding of amounts, composition and sources of DOM and their variations in conventional DWSSs.