Enhanced removal performance and mechanism of NH4+/NO3− in Starch-FeS-biochar-amended vertical flow constructed wetlands under Pb stress

Abstract

The co-pollution of nitrogen (N) and lead (Pb) is one of the most serious environmental issues, and the coexistence of Pb increases the difficulty of N removal. Biochar has been proven to be efficient for promoting N removal in constructed wetlands (CWs). However, the knowledge regarding key removal pathways of N and responses of plant physiological activities and microbial community is far insufficient in modified-biochar-added CWs. Therefore, Starch-FeS@PSB biochar (SFSP) was added to vertical flow CWs serving as functional substrate to enhance N removal efficiency under Pb stress, and its mechanism on N and Pb removal was also analyzed. Results showed that adding SFSP to CWs enhanced the nitrification and denitrification intensity of ICW2, and increased removal efficiencies of NO3−-N, NH4+-N and TN by 50.77 %, 35.90 % and 43.71 %, respectively. SFSP cooperated with anammox bacteria and denitrifying bacteria enhanced the removal of N under Pb stress. Furthermore, SFSP alleviated Pb stress on Iris pseudacorus L. and increased the relative abundance of Thiobacillus, Candidatus Kuenenia, Sulfurimonas and Geobacter so as to promote microbial N removal. Therefore, SFSP can be used as an efficient and eco-friendly functional substrate in CWs to remediate N and Pb co-polluted wastewater.