Aerobic Methane Oxidation Coupled to Denitrification: Kinetics and Effect of Oxygen Supply

Aerobic methane oxidation coupled to denitrification (AME-D) is a process in which aerobic methanotrophs oxidize methane and release organic compounds that are used by coexisting denitrifiers as electron donors for denitrification. This process is potentially promising for denitrification of wastewater or landfill leachate poor in organic carbon using methane produced onsite as external electron donor. We studied the kinetics of an aerobic methane-oxidizing denitrifying culture and investigated the effect of dissolved oxygen (DO) concentration and air supply rate on AME-D using a batch reactor and a semicontinuous reactor setup. At methane concentrations of 18-33% in air and air flow rates of 15-35 mL air L-1 liquid min(-1), the DO concentration was less than 0.01 mg L-1 and the nitrate removal reached a maximum value of 56.7 mg NO3-N g(-1) VSS d(-1) with 79% being attributed to denitrification. When the air supply rate was increased to 70 mL air L-1 liquid min(-1) resulting in a drop in methane content to 10%, the DO concentration in the bioreactor rose to about 0.8-1.0 mg L-1 and the total nitrate removal dropped to about 10 mg NO3-N g(-1) VSS d(-1) with none of it being attributed to denitrification.