Iron ore or manganese ore filled constructed wetlands enhanced removal performance and changed removal process of nitrogen under sulfamethoxazole and trimethoprim stress.

Abstract

Iron ore and manganese ore were used as substrate of constructed wetlands (CWs) to enhance nitrogen (N) removal. However, the N purification performance in CWs filled with iron or manganese ore under antibiotics stress needs further study. In this study, three groups of CWs filled with river sand, limonite (a kind of iron ore), and manganese ore sand were constructed, which were named as C-CWs, Fe-CWs, and Mn-CWs, respectively. The effect and mechanism of the composite antibiotics sulfamethoxazole (SMX) and trimethoprim (TMP) on N removal in CWs were investigated. While the addition of SMX and TMP inhibited about 40% nitrification and promoted about 25% denitrification in all CWs, Fe-CWs and Mn-CWs always had better N removal performance than C-CWs. Changes in microbial community structure in CWs indicated that the better N removal performance in Fe-CWs and Mn-CWs was attributed to the presence of more abundant and diverse N-associated bacteria, especially Fe- and Mn-driven autotrophic denitrifying bacteria. What's more, the addition of iron ore or manganese ore contributed to the better N removal performance with highest relative abundance of N-transferring bacteria under antibiotics stress.