The Impact of Surface Water Organic Matter Characteristics on Coagulation Efficiency

This study investigates the influence of organic matter properties in surface waters on the efficiency of single- and two-stage coagulation processes in drinking water treatment plants. The research was conducted at three treatment plants supplied by different surface water sources over a 15-month monitoring period. The analyzed parameters included total and dissolved organic carbon (TOC and DOC), biodegradable dissolved organic carbon (BDOC), water color, UV absorbance, zeta potential, and molecular weight distribution of organic substances. The results showed that coagulation efficiency depends strongly on both the concentration and the molecular characteristics of organic matter. The highest removal efficiency was observed for high-molecular-weight fractions (>2.0 kDa), mainly humic substances, whereas low-molecular-weight compounds were removed less effectively. The study also demonstrated that surrogate spectrophotometric parameters, particularly UV254 absorbance and color at 410 nm, can be used to monitor and optimize the coagulation process. Given the increasing frequency of extreme climate events and rapid shifts in raw water quality, optimizing single- and two-stage coagulation configurations has become an urgent operational necessity. This work provides a novel direct linkage between simple spectrophotometric indexes and precise chromatographic molecular ranges, delivering an immediate, high-impact predictive tool for real-time dosage optimization in water treatment engineering.