Combination of Methane Oxidation and Denitrification Process in a Two-Stage Bioreactor

Abstract

The importance of a combination of methane oxidation and denitrification processes in a two-stage bioreactor was investigated for the removal of nitrate using methane gas. In the configuration I, methane and oxygen were supplied separately to two columns of the two-stage bioreactor, an oxic column and an anoxic column. The nitrate removal efficiency was around 25 % and nitrite presented in the liquid medium, showing that the denitrification process was not complete. In the configuration II, methane and oxygen were supplied together to one column of the two-stage bioreactor, better results were achieved. Nitrate removal efficiency increased to almost 100 %, no nitrite was found in the liquid medium. The methane oxidation and the denitrification processes seemed to be happened simultaneously in one column of the two-stage bioreactor and demonstrated its advantages. Methane utilized concentration in the medium of the methane oxidation column increased from 1 to 2.1 mg/L, which resulted in more soluble organic carbon was created and supplied for denitrifiers. The C/N utilized ratio was lower in the Configuration II showing that the aerobic methane oxidation coupled to denitrification (AMO-D) achieved higher efficiency when methane and oxygen were supplied together.