The enhancement of nutrients removal performance in a vertical up-flow constructed wetland system using iron-carbon substrates

The reclaimed water was usually further treated by the constructed wetland (CW) to remove nitrogen and phosphorus before it was discharged to water bodies. In this work, the iron-carbon (Fe-C) substrate and plant-based carbon source were added to the vertical up-flow CWs to enhance the denitrification of reclaimed water. It was found that the removal efficiency of nitrate (NO3--N), total nitrogen (TN) and total phosphorus (TP) in the Fe-C amended CWs were significantly increased by 20–35%, 10–25%, and 10–35%. Moreover, the plant-based carbon source also contributed to TN and TP removal. The additional substrates also reduced the emission of NO2 and CH4 from the CWs. Finally, the microbial community was analyzed to disclose the mechanism involved in the enhanced performance of CWs. The enriched hydrogenotrophic and heterotrophic denitrifiers by the Fe-C substrates and pine bark contributed to the enhanced nitrification.