Electron Donating Capacity: A Promising Surrogate Indicator for the Optimization of Oxidative Water Treatments

The redox-active moieties of dissolved organic matter (DOM) significantly influence the degradation of pollutants in oxidative water treatments. Because electron donating capacity (EDC) directly probes the redox properties of DOM, it tends to be a promising surrogate indicator to reflect changes in the DOM oxidation state. Given the complexity of applying EDC to optimizing oxidation processes, this review summarizes a history of advances in EDC analytical methods and discusses key factors for the standardization of EDC measurement. The EDC and UV254 reductions induced by chemical oxidation are summarized to develop tailored water treatment control strategies. In addition, the applicability of EDC to indicate micropollutant abatement and disinfection byproduct formation is evaluated. Oxidative water treatments with chlorine, chlorine dioxide, permanganate, and ferrate yield a more pronounced reduction in EDC than in UV254 due to the formation of quinone moieties, while ozonation causes a comparatively smaller EDC reduction but a larger UV254 reduction. For oxidative water treatments in which the oxidant dosage is difficult to predict, EDC could serve as a promising surrogate indicator to meet treatment goals.