Carbon dioxide and weak magnetic field enhance iron-carbon micro-electrolysis combined autotrophic denitrification.

Combining iron-carbon micro-electrolysis and autotrophic denitrification is promising for nitrate removal from wastewater. In this study, four continuous reactors were constructed using CO and weak magnetic field (WMF) to address challenges like iron passivation and pH stability. In the reactors with CO + WMF (10 and 35 mT), the increase in total nitrogen removal efficiency was significantly higher (96.2 ± 1.6 % and 94.1 ± 2.7 %, respectively) than that of the control (51.6 ± 2.7 %), and FeO converted to low-density FeO(OH) and FeCO, preventing passivation film formation. The WMF application decreased the NO emissions flux by 8.7 % and 20.5 %, respectively. With CO + WMF, the relative enzyme activity and abundance of denitrifying bacteria, especially unclassified_Rhodocyclaceae and Denitratisoma, increased. Thus, this study demonstrates that CO and WMF optimize the nitrate removal process, significantly enhancing removal efficiency, reducing greenhouse gas emissions, and improving process stability.