Enhancing nitrogen removal via the complete autotrophic nitrogen removal over nitrite process in a modified single-stage tidal flow constructed wetland

•High-rate N removal could be achieved via CANON route in a modified TFCW.•Step-feeding significantly influenced N transformation in the TFCW.•Appropriate shunt ratio benefited the occurrence of the CANON process in the TFCW.•The TFCW with a shunt ratio of 1:1 removed N most effectively.

This study attempts to achieve a high-rate nitrogen removal via the complete autotrophic nitrogen removal over nitrite (CANON) process in a modified single-stage tidal flow constructed wetland (TFCW) with step-feeding, and nitrogen transformation pathways in the TFCWs treating domestic wastewater were explored under shunt ratio constraints. Shunt ratio significantly affected nitrogen transformation pathways in the TFCWs throughout the experiment. The anammox bacteria were enriched most effectively at the shunt ratio of 1:1, and then the initiation of a CANON process was accomplished in the TFCW under the appropriate limited oxygen condition. The mean TN removal rate reached up to (127.00 ± 13.78) mg (L d)−1 correspondingly. It could be concluded that autotrophic nitrogen removal via CANON process developed in the TFCW with optimized microenvironment that developed as a result of appropriate shunt ratio. The optimal shunt ratio of the TFCW for nitrogen removal was 1:1.