Fecha de publicación: 18/10/2019 Fuente: WIPO "circular economy" The invention discloses a device and a method for denitrification of sewage with low carbon-nitrogen ratio on the basis of double reflux and gradient oxygen limitation, belonging to the technical field of biological denitrification treatment of the sewage in environmental engineering. The device comprises a regulation pool, a water distribution groove, a biological rotating disc denitrification reactor, a gradient oxygen limitation biochemical pool and a sedimentation pool. When the device is in application, to-be-treated sewage successively flows through the regulation pool, the water distribution groove, the biological rotating disc denitrification reactor, the gradient oxygen limitation biochemical pool and the sedimentation pool, wherein a part of the sewage located at the tail end ofthe gradient oxygen limitation biochemical pool respectively flows back to the front end of the water distribution groove and the front end of the gradient oxygen limitation biochemical pool, while apart of sludge of the sedimentation pool flows back to same positions, so a double reflux system is formed. The device provided by the invention has the following beneficial effects: no need of a large amount of aeration and an external carbon source, low operation cost, high treatment efficiency, stable effluent water quality, and capability of meeting the requirements of the first-class standardA of Emission Standards for Pollutants of Urban Sewage Treatment Plants (GB18918-2002) and clean water discharge standards of Zhejiang Province for ammonia nitrogen and total nitrogen.