Removal of sulfonamide and enrofloxacin from water by periphyton under different nitrogen and phosphorus concentrations.

Periphyton is an emerging biological technology for water purification. However, the removal effect of periphyton on antibiotic contaminants in water under different nitrogen and phosphorus levels remains largely unknown. In this study, four nitrogen and phosphorus levels [N-P (mg·L-1): 2-0.2, 5-0.5, 8-0.8, 11-1.1] were set up to grow periphyton outdoors in plastic crates. The growth, photosynthe-tic activity, species composition, and removal of sulfonamide and enrofloxacin were simulated at a medium scale. The results showed that biomass of the surrounding organisms increased with the increases of culture time. In contrast, the photosynthetic pigment content and photosynthetic activity showed a "single peak" pattern, which first decreased and then increased, indicating that algae in the biofilm would be stressed by antibioics but could quickly adapt and recover vitality. In addition, different nitrogen and phosphorus concentrations resulted in differences in community composition. With the increases of nutrient concentrations, species richness of periphyton algae gradually decreased. The relative abundance of Dictyosphaerium and Chlorella in each treatment was relatively high. Results of 16S rRNA high-throughput sequencing showed that the flora of Rhizobiaceae, Frankiales, and Moraxellaceae was significantly enriched in groups 2-0.2. The relative abundance of Chitinophagaceae in all the four treatments was the highest. The removal rate of sulfonamide in all treatments was higher than 50%, while the removal rate of enrofloxacin in all treatments was more than 90%. The removal rate of sulfonamide in (N-P) 2-0.2 mg·L-1 group (65.8%) was significantly higher than that in other groups, but with no significant difference in the removal rate of enrofloxacin among all treatments. The results showed that periphyton had an excellent ability to remove sulfonamide and enrofloxacin in a wide range of N-P levels. The removal rate of soluble nitrogen in water was not different in each treatment group, and the removal effect of soluble phosphorus was substantial. Our results provided primary data for the ecological removal of sulfonamide and enrofloxacin in water, which gave a new idea for the development of environmental removal technology for new antibiotic pollutants in water.