Driving factors and microbiology for the enrichment of denitrifying anaerobic methane oxidation (DAMO) microorganisms

The application of the denitrifying anaerobic methane oxidation (DAMO) in a biological nitrogen removal system has received much attention since methane is used as the sole carbon source and produced in the anaerobic digestion process of wastewater treatment plant. DAMO reaction is performed by DAMO archaea (Methanoperedens nitroreducens) and DAMO bacteria (Methylomirabilis oxyfera, M. sinica, M. limnetica, and M. lanthanidiphyla belonging to NC10 phylum). In the presence of methane, nitrate, or nitrite are used as the substrate, then the reaction takes place under the anoxic condition. Due to extremely slow growth and stringent metabolic requirements, these microbes are difficult to be cultured and applied in the wastewater treatment. In this paper, driving factors and microbiology for the enrichment of DAMO process in previous studies are reviewed, especially the effects of inoculum, reactor types, and environmental factors (substrate concentration, pH, dissolved oxygen, and temperature) on the DAMO process. Besides, key factors that can effectively control microbial community structures and enhance the optimization strategies for DAMO enrichment are identified in this review. In the future study, there are still some challenges to be addressed, such as growth factors affecting DAMO process performance and the stable operation of ecosystem in the cultivation process.