New Rapid Methods for Assessing the Production and Removal of Labile Organic Carbon in Water Treatment Using Fluorescence and Oxygen Measurements

Labile organic carbon is a major nutrient, controlling microbial activity in aquatic ecosystems and contributing to the global cycling of carbon. During the production and distribution of drinking water, labile carbon fractions often escape treatment, which threatens water quality and biostability. This study proposes and compares two rapid methods for monitoring the production and removal of labile organic carbon in freshwater. One method measures the consumption of oxygen by bacteria during their initial exponential growth phase and uses this to predict how much labile organic carbon is present. The other method uses an a priori model of the fluorescence composition of dissolved organic matter to estimate the relative amount of biodegradable carbon fractions. In water treatment plants and in lab-scale experiments, both methods showed selectivity for biodegradable fractions of natural organic matter and indicated similar changes in scale and direction when water samples were exposed to biodegradation, with higher precision for the fluorescence measurement (coefficient of variation ∼1.5%) compared to the oxygen method (coefficient of variation ∼15%). Software is provided to aid in the implementation of these new methods, enabling their exploration and refinement in future studies.