Fates of persistent and mobile organic micropollutants in simulated bank filtration: Column study and predictive modelling

Organic micropollutants (OMP), characterized by their persistence and mobility, are increasingly detected in aquatic environments, raising significant concerns about their impact on the safety of drinking water. This study investigated the long-term fate of selected emerging, potentially persistent and mobile OMP through column experiments conducted under varying redox conditions. Additionally, two predictive models were developed using artificial neural networks (ANN), leveraging the experimental dataset to estimate OMP concentrations at depths of 0.5 m and 1.0 m in the columns. The study revealed that the columns remained oxic within the first 0.5 m depth and anoxic below this depth, as dissolved oxygen concentrations dropped below 0.5 mg/L. Biological activity was high within the first 0.5 m depth, as high dissolved oxygen utilization, reductions in dissolved organic matter concentrations, and decreased UV absorbance at 254 nm were observed. Among the OMP studied, six exhibited persistence under both oxic and anoxic conditions, even within a hydraulic retention time (HRT) of 45 days. Other OMP showed biotransformation, with seven being 100% eliminated within an HRT of 5.5 days under oxic conditions. Some OMP displayed improved degradation with prolonged operational time in oxic conditions, while others, such as diatrizoate, were eliminated around 70% under anoxic but were persistent under oxic conditions. The ANN models demonstrated reliable predictions of OMP concentrations, achieving high correlation coefficients (above 0.91) during the training and testing/validation phases. Furthermore, the robustness of the models was highlighted by their low root mean squared error values. Overall, the study showed the critical role of HRT and redox conditions for the elimination of OMP. • Fate of organic micropollutants (OMP) in saturated sand columns. • Attenuation and persistence examined under oxic and anoxic conditions. • Six OMP persisted under both redox conditions and within 45 days residence time. • Diatrizoate was eliminated in anoxic conditions but persisted in oxic conditions. • High accuracy (R² > 0.91) in OMP concentration prediction using modelling.