Managing dissolved methane gas in anaerobic effluents using microbial resource management-based strategies

This study reports the findings of three independent microbial resource management-based strategies to manage dissolved methane (D-CH₄) gas in anaerobic effluents. In the first approach, an aerobic methanotroph Methylococcus capsulatus was immobilized. A maximum of 1.75 kg COD m^-3 d^-1 at a hydraulic retention time of 0.5 h was recorded in the attached growth aerobic methane oxidizing reactor. In the second strategy, denitrifying methane oxidizing organisms (DAMO) were first enriched in a lab-scale batch reactor which enabled a maximum methane oxidation rate of 0.31 kg COD m^-3 d^-1. In the last strategy, a mixed community of aerobic ammonia oxidizers was immobilized on sponge carriers and used to convert the D-CH₄ gas into useful biofuel methanol at a rate of 0.73 kg COD m^-3 d^-1 equivalent of COD with a methanol production of 31.5 g COD m^-3 d^-1. On a COD basis, the amount of methanol generated could denitrify nearly 7 mg L^-1 of NO₃-N.