Determination of the optimal aeration for nitrogen removal in biochar-amended aerated vertical flow constructed wetlands.

Nitrogen removal in vertical flow constructed wetlands (VFCWs) is still a key problem especially for treating low C/N wastewaters. In this study, nitrogen removal and nitrous oxide (N2 O) emission in biochar-amended aerated VFCWs were evaluated under the varying intermittent aeration (different aeration times and aeration rates). The results indicated that the optimal aeration time and rate were 2 h d-1 and 0.6 L min-1 , which could create alternant of aerobic and anaerobic conditions for the simultaneous nitrification and denitrification in VFCWs. Much higher removal efficiency of COD (95.9%), NH4 + -N (96.6%), and TN (74.7%) was achieved under the optimal conditions, and moderate N2 O emission (282 μg m-2 ·h-1 ) was observed simultaneously. The results can be used to select the optimal aeration in the further design and application of biochar-amended aerated CW treatments.