Spectral characterization of the effect of gas–water ratio on dissolved organic nitrogen variation along a drinking water biological aerated filter

To improve the understanding of dissolved organic nitrogen (DON) variation characteristics in a biological aerated filter (BAF) used for drinking water treatment, this study investigated the effects of gas–water ratios (0, 0.5:1, 2:1, and 10:1), a controlling factor of BAF operation, on DON characteristics. The dissolved organic carbon (DOC) removal efficiency in the BAF was consistent with DON concentration and increased as the gas–water ratio increased to a certain point, above which the increase gradually decreased. The optimal gas–water ratio in this study was considered to be 2:1 from the perspective of DOC removal and DON reduction. Use of fluorescence regional integration (FRI) and parallel factor (PARAFAC) model to analyze the effects of the gas–water ratio on the spectral characteristics of DON revealed that humic acid-like substances were not sensitive to the gas–water ratio, while protein-like substances were more sensitive. Increasing the gas–water ratio was beneficial to the reduction of biodegradable DON. Correlation analysis showed that the results obtained using FRI were consistent with those obtained using the PARAFAC model under different gas–water ratios.