Enhancement of the complete autotrophic nitrogen removal over nitrite process in a modified single-stage subsurface vertical flow constructed wetland: Effect of saturated zone depth

- SZD significantly affected N transformation in the VSSF.
- Suitable SZD benefited enhancement of CANON process in the VSSF.
- The VSSF with SZD of 45 cm achieved high-rate N removal via CANON route.
- Less N2O emission was achieved owing to enhancement of CANON process in the VSSF.

This study was conducted to explore enhancement of the complete autotrophic nitrogen removal over nitrite (CANON) process in a modified single-stage subsurface vertical flow constructed wetland (VSSF) with saturated zone, and nitrogen transformation pathways in the VSSF treating digested swine wastewater were investigated at four different saturated zone depths (SZDs). SZD significantly affected nitrogen transformation pathways in the VSSF throughout the experiment. As the SZD was 45 cm, the CANON process was enhanced most effectively in the system owing to the notable enhancement of anammox. Correspondingly, the VSSF had the best TN removal performance [(76.74 ± 7.30)%] and lower N2O emission flux [(3.50 ± 0.22) mg·(m2·h)−1]. It could be concluded that autotrophic nitrogen removal via CANON process could become a primary route for nitrogen removal in the VSSF with optimized microenvironment that developed as a result of the appropriate SZD.