Effects Of Sulfamethazine On Performances Of Duckweed Systems For Treatment Of Anaerobically Digested Swine Wastewater And Degradation Of Sulfamethazine

In order to prevent livestock infections and treat diseases,antibiotics were added to feed as feed additives.Sulfamethazine（SMZ）was applied in swine wastewater due to its low cost and broad-spectrum antimicrobial activity.However,antibiotics cannot be completely absorbed by livestock.Thus,SMZ were discharged into swine wastewater through excretion,resulting in higher concentrations of antibiotics in swine wastewater.As antibiotics continue to be released into aquatic systems,which will lead to the antibiotic contamination.Therefore,high concentrations of antibiotics have brought serious challenges to the phytoremediation treatment of swine wastewater.Therefore,this paper focuses on the effect of sulfamethazine on the removal performance of duckweed system for the treatment of anaerobically digested swine wastewater（ADSW）.In order to provide a scientific reference for the design and application of the duckweed treatment process and wastewater resource utilization in the swine wastewater containing antibiotics.The research contents and results are as follows:1)The effect of sulfamethazine on ammonia nitrogen and total phosphorus in ADSW treated by duckweed.The results showed that sulfamethazine in ADSW had a significant inhibitory effect on the removal of nutrients including NH₃-N and TP by duckweed system,and with the increase of sulfamethazine concentration,duckweed had a significant inhibitory effect on nutrients in biogas slurry.Increased removal efficiency of substances;2)The effect of sulfamethazine on the synthesis of nutrients and physiological and biochemical indexes of duckweed.The results showed that:under the action of sulfamethazine,the content of protein and vitamin E in duckweed increased gradually with the increase of the concentration.Sulfamethazine induces the accumulation of H₂O₂ and malondialdehyde in duckweed,causing lipid peroxidation and oxidative stress;3)The effect of sulfamethazine on its own antioxidant system of duckweed.The results showed that reduced glutathione and vitamin C played a major role in duckweed alleviating sulfamethazine stress in swine biogas slurry.However,we often think that the antioxidant enzyme activities（catalase and ascorbate peroxidase）that relieve external stress are severely inhibited;4)The effect of sulfamethazine on the microbial community in duckweed.The results showed that the duckweed system could alleviate the stress effect of sulfamethazine by regulating the types of antibiotic-resistant microbial communities,and the microbial diversity decreased with the presence of sulfamethazine.Moreover,the microbial community had good bacterial abundance and stability,with dominant microbial communities detected at the phylum and genus levels.5)Intermediate degradation products and degradation pathways of sulfamethazine in the system of duckweed.The results showed that the duckweed system had better removal effect when the concentration of sulfamethazine was lower.The higher the concentration of sulfamethazine in the duckweed system,the lower the removal efficiency and the longer the degradation time.Through LC-MS analysis,the possible degradation pathways of sulfamethazine in duckweed system were proposed.