System and method for treating nitrate nitrogen sewage by constructed wetland

A system for treating nitrate nitrogen sewage by autotrophic denitrification subsurface flow constructed wetland, the system comprising:

• a wetland pool body, a wetland substrate, a water distribution device, a water outlet device, and plant;
• the wetland substrate is filled in the wetland pool body;
• the wetland substrate comprises pyrite, volcanic rock and biochar;
• the water distribution device is located at a surface of the wetland substrate, and influent water entering the wetland pool body by the water distribution device flows out by gravity;
• the water outlet device is located at a bottom of the wetland pool body;
• the plant is planted in the wetland substrate;
• a dissolved oxygen concentration of the system for treating nitrate nitrogen sewage by autotrophic denitrification subsurface flow constructed wetland is maintained at 1.2~2.8 mg/L to construct a dissolved oxygen environment conducive to growth and metabolism of autotrophic denitrifying bacteria and not conducive to growth of heterotrophic anaerobic denitrifying bacteria;
• and, when the system for treating nitrate nitrogen sewage by autotrophic denitrification subsurface flow constructed wetland is running, by controlling a hydraulic retention time, nitrate nitrogen in the influent water is fully contacted with autotrophic denitrifying bacteria and reduced to nitrogen gas.