Fe-C autotrophic denitrification sludge
This study systematically investigated the effects of nitric oxide (NO) on the performance of an IC-ME autotrophic nitrogen removal system. Long-term experiments were conducted to compare nitrogen removal efficiency and N2O emission under different NO concentrations and gas flow rates. Sludge samples were collected at the steady stage under various operational conditions for batch tests to evaluate nitrogen removal rates and variations in intermediate products. Scanning electron microscopy (SEM), extracellular polymeric substances (EPS) analysis and three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) were applied to reveal the impacts of substrate changes on biofilm surface characteristics. Furthermore, high-throughput sequencing and metagenomics were employed to elucidate the underlying mechanism of NO effects on the IC-ME autotrophic nitrogen removal system. This work provides a theoretical foundation for the application of NO-enhanced IC-ME in practical nitrogen removal processes.