Study of the Anaerobic Methane Oxidation Coupled to Nitrate Denitrification
Methane can be a potentially inexpensive, widely available electron donor for biological denitrification of wastewater, landfill leachate or drinking water, while no studies have clearly shown nitrate reduction to nitrogen gas. Recently anaerobic methane oxidation (AMO) coupled to partial denitrification (nitrite to nitrogen gas) was found by several studies. A microbial consortium, enriched from anoxic sediments, oxidized methane to carbon dioxide coupled to denitrification in the complete absence of oxygen, though the rates and pathways of AMO coupled to denitrification are still poorly understood. In this study, direct AMO coupled to denitrificaiton of nitrate was proved to be possible and its kinetic parameters were experimentally determined. Using a set of batch experiments designed to provide the best estimates of each parameter, these parameters were obtained: maximum specific growth rate (µmax) = 0.121/day, maximum substrate consumption rate (qmax) = 1.63 mg COD/mg cells-day, true yield (Y) = 0.074 mg cells/mg COD, half maximum-rate substrate concentration (Ks) = 85 µM CH4, and endogenous decay rate (b) = 0.03/day. This study firstly characterized kinetic parameters of anaerobic methanotrophic denitrifiers, which will substantially help understand anaerobic methane oxidation in natural systems and accelerate methane-utilizing denitrification in engineering systems.