NOVELTY - Denitrifying a film coupled type aerobic methanoic acid comprises: processing the water inflowing into an aerobic reactor through an inflow pump; controlling the flow rate of the water using mass flow controllers, and inflowing the water into a reaction bath in a form of the microbubble through a micro porous film module; removing the nitrogen from the water; precipitating large amount of microorganism; removing the nitrogen gas remaining inside the processing water by the microorganism in an aerobic state; and filtering using the micro porous film module, and ejecting using an efflux pump.    USE - The method is useful for denitrifying a film coupled type aerobic methanoic acid (claimed) form an industrial water, landscape architecture water or the water for irrigation.    ADVANTAGE - The method is capable of improving underwater material transfer efficiency of the methane having a low solubility. The supernatant is filtered through the micro porous film module so as to minimize the erasure of the microorganism and maintain the microorganism within the reaction bath with the high concentration. The gas injection, the water filtering and exhaustion process are repeated using the same micro porous film module without the additional air supply process and with reduced film blockage.    DETAILED DESCRIPTION - Denitrifying a film coupled type aerobic methanoic acid comprises: processing the water inflowing into an aerobic reactor through an inflow pump using a sewage high disposal process or a sewage processing water post denitrification process; controlling the flow rate of the water using mass flow controllers, and inflowing the water into a reaction bath in a form of the microbubble through a micro porous film module that is positioned inside the reaction bath; removing the nitrogen from the processing water using a denitrification reaction process; precipitating large amount of microorganism; removing and the nitrogen gas remaining inside the processing water by the microorganism in an aerobic state; and filtering using the micro porous film module, and ejecting using an efflux pump. An INDEPENDENT CLAIM is included for a denitrizer comprising: a reaction bath in which the processing water is flowed in by an inflow pump; mass flow controllers for controlling the flow rate of the inflow of the oxygen gas and methane gas; a micro porous film module that is located with a reactor bottom, is positioned inside the reaction bath and is connected with an upper part of reactor; a three way valve for controlling a direction of the flow; a pressure sensor for monitoring the differential pressure; and an efflux pump for ejecting the processing water.