Mechanism of stable power generation and nitrogen removal in the ANAMMOX-MFC treating low C/N wastewater

This study investigated the mechanism of enhanced power generation and nitrogen removal in an ANAMMOX-MFC reactor through subsequent acetate addition. Data showed that nearly 99% total nitrogen removal (≤1 mg L-1) and 1.41 W m-3 power generation were achieved synchronously under low COD/N (∼1.5) after the subsequent addition of acetate (100 mgCOD·L-1). The columbic efficiency of the system has increased by 15 times (from 0.64% to 9.48%) after adding acetate. Batch tests showed that the denitrification and ANAMMOX progress occurred synchronously before acetate addition the nitrogen removal rate was accelerated. A distinct shift of bacterial community driven by acetate addition was discovered. The high throughput sequencing analysis indicated acetate addition stimulated the enrichment of denitrifiers, such as Aquimonas, Bradyrhizobium, Thauera, and the potential exoelectrogens changing from Comamonas to Pseudomonas. Functional genes forecasts based on KEGG database and COG database showed that the expressions of TCA functional genes were highly promoted in ANAMMOX-MFC, which demonstrated the enhanced electron transfer pathway driven by acetate addition under low COD/N ratio.