Device for advanced nitrogen and phosphorus removal in sewage treatment

A device for advanced nitrogen and phosphorus removal in sewage treatment, comprising a pre-denitrification zone, an anaerobic zone, an anoxic zone, an aerobic zone, a sedimentation zone, a biological filtration zone, and a clear water zone that communicate with each other in sequence according to a sewage treatment process, wherein a sludge return system is provided between the pre-denitrification zone and the sedimentation zone, and the sludge return system can return sludge in the sedimentation zone to the pre-denitrification zone;

• a nitrification liquid return system is provided between the anoxic zone and the aerobic zone, and the nitrification liquid return system can return a nitrification liquid in the aerobic zone to the anoxic zone;
• a filler layer is provided in the biological filtration zone, and the filler layer divides a cavity in the biological filtration zone to form an upper water inlet cavity and a lower water outlet cavity;
• the water inlet cavity communicates with a top of the sedimentation zone, and the water outlet cavity communicates with a bottom of the clear water zone;
• a backwash aeration pipe is provided in the water outlet cavity, and a backwash water outlet is formed in the water inlet cavity;
• and the backwash water outlet is connected to a sludge concentration and storage tank or the pre-denitrification zone.