Kinetic study on anaerobic oxidation of methane coupled to denitrification

•Kinetic parameters for AOM-D were estimated experimentally.•The maximum specific growth rate of AOM-D culture was 0.121/d.•The maximum specific substrate-utilization rate was estimated at 28.8 mmol CH4/g cells-d.•The half maximum-rate substrate concentration was determined at 83 μM CH4.•The threshold substrate concentration was 28.8 μM CH4.

Monod kinetic parameters provide information required for kinetic analysis of anaerobic oxidation of methane coupled to denitrification (AOM-D). This information is critical for engineering AOM-D processes in wastewater treatment facilities. We first experimentally determined Monod kinetic parameters for an AOM-D enriched culture and obtained the following values: maximum specific growth rate (μmax) 0.121/d, maximum substrate-utilization rate (qmax) 28.8 mmol CH4/g cells-d, half maximum-rate substrate concentration (Ks) 83 μΜ CH4, growth yield (Y) 4.76 g cells/mol CH4, decay coefficient (b) 0.031/d, and threshold substrate concentration (Smin) 28.8 μM CH4. Clone library analysis of 16S rRNA and mcrA gene fragments suggested that AOM-D reactions might have occurred via the syntrophic interaction between denitrifying bacteria (e.g., Ignavibacterium, Acidovorax, and Pseudomonas spp.) and hydrogenotrophic methanogens (Methanobacterium spp.), supporting reverse methanogenesis-dependent AOM-D in our culture. High μmax and qmax, and low Ks for the AOM-D enrichment imply that AOM-D could play a significant role in mitigating atmospheric methane efflux. In addition, these high kinetic features suggest that engineered AOM-D systems may provide a sustainable alternative to nitrogen removal in wastewater treatment.