Enhanced nitrogen removal and associated microbial characteristics in a modified single-stage tidal flow constructed wetland with step-feeding

This study was conducted to explore nitrogen transformation and associated microbial characteristics in a modified single-stage tidal flow constructed wetland (TFCW) at five different shunt ratios. Shunt ratio significantly affected nitrogen removal during operation of the TFCW with adoption of a modified step-feeding mode. When the shunt ratio was 1:2, TFCW had the best pollutant removal performance and was particularly effective for total nitrogen (TN). The abundance of nitrogen transformation microorganisms was also affected by the shunt ratio of the system. Molecular biological analyses demonstrated that both denitrification and anammox were enhanced when the shunt ratio was greater than 0:1, resulting in the development of multiple and complete nitrogen removal pathways in the TFCW. These results show that the optimal shunt ratio of the modified single-stage TFCW for effective nitrogen removal was 1:2.