Impacts of O:CH ratios and CH concentrations on the denitrification and CH oxidations of a novel AME-AD system.

Aerobic methane (CH) oxidation coupled to denitrification (AME-D) is a promising process for the denitrification of low C/N wastewater. Compared with anaerobic denitrifying bacteria, aerobic denitrifying bacteria may enable AME-D have high denitrification ability under aerobic conditions. This study constructed a novel aerobic methane oxidation coupled to aerobic denitrification (AME-AD) system using the typical aerobic denitrifying bacteria Paracoccus pantotrophus ATCC35512 and the typical aerobic methane oxidizing bacteria Methylosinus trichosporium OB3b. The denitrification and CH oxidations of AME-AD with different O:CH ratios (0:1, 0.25:1, 0.5:1, 0.75:1, 1:1 and 1.25:1) and CH concentrations (0, 14000, 28000, 42000, 56000 and 70000 mg m) were investigated in batch experiments. Higher O:CH ratios can significantly improve the denitrification and CH oxidations of the AME-AD (P < 0.05). The treatment with an O:CH ratio of 1.25:1 had the highest denitrification rate (0.036 mg h) and highest CH oxidation rate (0.20 mg h). The CH concentration in the headspace was positively correlated with the AME-AD denitrification rate. The calculated CH/NO(mol/mol) in most treatments ranged from 5.76 to 6.84. In addition, excessively high O and CH concentrations can lead to increased nitrous oxide (NO) production in AME-AD. The NO production rate was up to 1.00 μg h when the O:CH was 1.25:1. These results can provide data support for the application of AME-AD for low-C/N wastewater treatment and greenhouse gas emission reduction.