Abstract: To understand the purification performance and microbial community structureresponse of constructed wetlands to antibiotics additions of fluoroquinolones (FQs), sulfonamides (SFs) and tetracyclines (TCs), we measured the antibiotic contents and microbial community structure in horizontal subsurface flow constructed wetlands with single-layer matrix structure and multi-layer matrix structure (3 and 6 layers) which have been in operation for many years, with solid phase extraction-high performance liquid chromatography and high-throughput sequencing, respectively. We analyzed the removal results of eight antibiotics belonging to three types in wetland systems, the effects on the removal of conventional pollutants, and changes of microbial community structure. The results showed that the constructed wetlands had good removal effects on FQs, sulfathiazole, sulfamethazine and oxytetracycline (>95%), but with relatively poor effects on sulfadiazine and tetracycline (61.9%-66.8%) under the same conditions. The purification effect of multi-layer wetland systems on antibiotics was 3.2% higher than that of single layer wetland system. The addition of antibiotics increased the removal efficiency of COD and NH₄⁺-N by 18.5% and 16.5%, respectively, but decreased that of TP by 28.6%. After the addition of FQs, SFs, and TCs, mean Shannon index in the three wetland systems decreased from 5.80 to4.66, while mean Simpson index increased from 0.017 to 0.063. Before and after the addition of antibiotics, the main dominant phyla (Proteobacteria and Bacteroidetes) remained unchanged, while the primary and secondary positions of the other dominant phyla (Chloroflexi, Firmicutes, Verrucomicrobia, and Acidobacteria) changed. There were obvious changes in the structure of dominant genera. The abundance of denitrifying bacteria Acinetobacter, Aquabacterium and Pseudomonas were significantly increased, replacing the phosphorusremoving bacteria Dechloromonas and Flavobacterium as the main dominant genera.

Key words: horizontal subsurface flow constructed wetland, antibiotics, microbial community.