Mitigating greenhouse gases and ammonia emission from the storage of digested pig slurry: Adaption of dissolved oxygen

Dissolved oxygen (DO) plays a vital role in the emission of carbon-nitrogen gaseous (CNs: NH3, CH4 and N2O) in livestock wastewater, but the effect of different DO concentration on the emission of CNs is yet unclear. In this study, the continuous emission of CNs from swine manure biogas digestate (BD) storage under different DO concentrations was monitored using the dynamic emission vessel method for 60 consecutive days, and the emission mechanism was explored combined with the microbial analysis. Results showed that the cumulative emission fluxes of GHGs in BD with DO concentrations of 1.0, 2.0, and 4.0 mg L- 1 were reduced by 58.66 %, 70.46 %, and 66.81 %, respectively, compared with the static storage BD. Verticia might inhibits the activity of acetoclastic genera (Methanosaeta and Methanosarcina). DO concentrations was positively correlated with the Verticia. Increasing the concentration of dissolved oxygen reduce CH4 emissions. N2O and NH3 emissions were positively correlated with DO concentration, but the total N loss showed the opposite changes. The results of this study provide a deeper insight into the effect of DO concentration on the CNs emission, and an appropriate concentration of 1.0-2.0 mg L- 1 is recommended for the reduction of CNs in swine manure BD.