Enhancement of nitrate-dependent anaerobic methane oxidation via granular activated carbon.

Denitrifying anaerobic methane oxidation (DAMO) is a bioprocess utilizing methane as the electron source to remove nitrate or nitrite, but denitrification rate especially for nitrate-dependent DAMO is usually limited due to the low methane mass transfer efficiency. In this research, granular active carbon (GAC) was added to enhance the nitrate-dependent DAMO process. The results showed that the maximum nitrate removal rate of GAC assisted DAMO system reached as high as 61.17 mg L-1 d-1, 8 times higher than that of non-amended control SBR. The porous structure of GAC can not only adsorb methane, but also keep the internal DAMO archaea from being washed out, and thus benefits for DAMO archaea enrichment. The relative abundance of DAMO archaea accounted for 96.3% in GAC-SBR, which was significantly higher than that of non-amended control SBR system (29.9%). Furthermore, GAC amendment up-regulated metabolic status of denitrification and methane oxidation based on gene sequence composition. The absolute abundances of function genes (NC10 pmoA and ANME mcrA) in GAC-SBR were almost 20 times higher than that of non-amended control SBR. This study provides a novel technique to stimulate the nitrate-dependent DAMO process.