Dynamics of dissolved organic matter and dissolved organic nitrogen during anaerobic/anoxic/oxic treatment processes

With Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and fluorescence spectroscopy, this study investigated the transformation of dissolved organic matter (DOM) and nitrogen (DON) during the widely-applied anaerobic/anoxic/oxic (A2O) processes to provide molecular insights into the removal, generation, and reduction of DOM/DON species in different biological treatment units. Results indicated that the anaerobic process decomposed the macromolecules of influent DOM/DON and decreased their mass. The anoxic process denitrified DON and generated DOM, as indicated by the decreased molecule number of CHON and CHONS and the increased CHO and CHOS species, as well as the increased overall DOM intensities. DOM mineralization and ammonia nitrogen-DON conversion occurred in the oxic process. Aromaticity and unsaturation degree increased slightly after the A2O processes, which was correlated with the relative abundance of Proteobacteria (positively) and Bacteroidetes (negatively). The results have strong implications to the understanding of DOM/DON dynamics in wastewater treatment plants.

Automated summary

Using FT-ICR MS and fluorescence spectroscopy, this study examined the transformation of DOM and DON during A2O processes, showing that anaerobic degradation reduced the mass of influent DOM/DON, anoxic denitrified DON and generated DOM, and oxic processes led to DOM mineralization and ammonia nitrogen-DON conversion. Increases in aromaticity and unsaturation degree after A2O processes were associated with Proteobacteria (positively) and Bacteroidetes (negatively), providing important insights into DOM/DON dynamics in wastewater treatment plants.