Methane-dependent denitrification by a semi-partitioned reactor supplied separately with methane and oxygen

Abstract Methane (CH 4 ) can be used as an alternative carbon source for denitrification with added oxygen (O 2 ). However, the off-gas of denitrification reactors using a CH 4 –O 2 mixture contains unused CH 4 and O 2 in proportions that make it unusable for fuel, carry explosion risks, and, if released into the atmosphere, contribute to the greenhouse effect. This study tested a novel reactor with a partition dividing the headspace completely and extending partly into the liquid layer. When CH 4 and O 2 were supplied separately to the liquid layer on opposite sides of the partition, the methane-dependent denitrification (MDD) activity was similar to that when the two gases were supplied as a mixture. In reactors with separate gas supplies, the off-gas from the CH 4 supply side was high in CH 4 and low in O 2 , and was usable for fuel, and that from the O 2 supply side was very low in CH 4 , and might be released into the atmosphere. MDD activity increased with the O 2 supply rate, and separate discharge of CH 4 and O 2 was maintained. The concentration of dissolved methane in the effluent was decreased by lowering the CH 4 /O 2 supply ratio to 1.0 and drawing the effluent from the O 2 supply side. This novel reactor enhances the safety of MDD, allows reuse of methane as fuel, and reduces methane leakage to the atmosphere.