Development of aerobic methane oxidation, denitrification coupled to methanogenesis (AMODM) in a microaerophilic expanded granular sludge blanket biofilm reactor

Abstract

The issue of enhancing nitrogen removal and managing dissolved methane emission in anaerobic treatment systems is a major bottleneck in its wider application to treat high-strength organic wastewater with nitrate. Herein, a novel aerobic methane oxidation, denitrification coupled to methanogenesis (AMODM) process was developed in a glucose-fed microaerobic expanded granular sludge blanket biofilm reactor (EGSBBR) through in-situ utilization of produced methane for nitrogen removal. The 162-day operation demonstrated that long-term treatment performance under the decreased COD/NO3−-N (C/N) ratio from 66.7 to 10 and the optimal C/N ratio for completing AMODM was found to be 16.7. Microbial community analysis further evidenced that Methanothrix as key methanogen predominated in the sludge bed, while Methlogaea as aerobic methane oxidizer was mainly detected in the packing bed of the hybrid system. Meanwhile, some facultative heterotrophic and dissimilated nitrate-reduction (DNRA) genera also co-existed. The profiling of key functional genes further proved concurrent occurrence of methanogenesis, aerobic methane oxidation and denitrification. Furthermore, possible microbial mechanism on AMODM process was elucidated from the prospective of targeted species interaction within the reactor. This research provides a robust and environment-friendly alternative process treating nitrate-containing organic wastewater towards efficient nitrogen removal, low resource consumption, bioenergy recovery and greenhouse gas reduction.