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 (NO) 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 and 0.6 L min, 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%), NH-N (96.6%), and TN (74.7%) was achieved under the optimal conditions, and moderate NO emission (282 μg m·h) 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.