Robust nitrate removal and bioenergy generation with elucidating functional microorganisms under carbon constraint in a novel multianode tidal constructed wetland coupled with microbial fuel cell

Abstract

This study investigated synthetic wastewater treatment under low inflow C/N ratio and characterized NO₃^--N-transforming and electricity-producing bacteria in a multi-anode tidal constructed wetland-microbial fuel cell (TFCW-MFC). The optimal concurrent average removal rates of NH₄⁺-N and NO₃^--N were 73% and 78%, respectively, under a flood/rest/flood time of 4 h/2h/4h in "tide" mode accompanied by one recirculation. The lowest NO₃^--N concentration among all anodes was observed when the electrode gap was 45 cm. Similarly, the 45 cm anode exhibited selective enrichment of Variovorax and Azoarcus. Correction analysis showed that the high relative abundance of Azoarcus was crucial in enhancing NO₃^--N removal, and the internal resistance significantly decreased as the relative abundance of Acidovorax increased. These results suggest that NO₃^--N removal and bioelectricity generation can be promoted in a TFCW-MFC with limited carbon by improving the culture conditions for specific genera.

Keywords: Electricigens; Microbial fuel cell; Nitrate removal; Nitrogen–transformation genera; Tidal flow constructed wetland.