Spectral characterization of the effect of gas-water ratio on dissolved organic nitrogen variation along biological aerated filter for micropolluted source water pre-treatment

Abstract In order to improve our understanding of dissolved organic nitrogen (DON) variation characteristics in the biological aerated filter (BAF) for drinking water treatment, this study focused on gas-water ratio, a controlling factor of BAF operation, to study spectral characteristics of DON under different gas-water ratio conditions (0, 0.5:1, 2:1 and 10:1). The variations of dissolved organic carbon (DOC) and DON concentrations showed that DOC removal efficiency was consistent with DON concentration, both of which increased with the increase of gas-water ratio, but the increase gradually reduced and was certain limited. Three-dimensional excitation–emission matrix (3D-EEM) spectroscopy combined with parallel factor (PARAFAC) model and fluorescence regional integration (FRI) technique were applied to analyze the effect of gas-water ratio on spectral characteristics of DON, PARAFAC analysis results identified the main component of DON were tryptophan and protein related substances. The resistances of various fluorescent substances in the FRI technique under the influence of gas-water ratio were shown as: protein substances > humic acid and fulvic acid substances ≈ SMPs-like substances. Correlation analysis showed that the variation of FIS from PARAFAC model was consistent with corresponding normalized integration volume in FRI analysis under different gas-water ratios.