Study On Tailwater Purification Effect And Microbial Community Characteristics In A Large-scale Integrated Constructed Wetland

As an engineering system,constructed wetland is widely used in secondary sewage treatment,which can further remove pollutants in water.Although the research on constructed wetlands in laboratory scale has been widely reported,the knowledge of performance of large-scale integrated constructed wetland is still scarce.This paper focuses on the removal of antibiotics and nutrients by functional systems and their relationship with microorganisms,relying on the integrated constructed wetland.It has been running continuously for 6 years and treat 60,000 tons of tailwater per day.The purpose of this paper is to study the removal efficiency of antibiotics and nutrient contaminants by HPLC-MS/MS in the integrated constructed wetland,and to reveal the key bacteria for removing antibiotics and nutrients by 16S rRNA sequencing technology.The main results are as follows:(1)The nutrient removal efficiency of the integrated constructed wetland is excellent.The removal efficiency of total nitrogen,ammonia nitrogen,total phosphorus and COD are 38.57%-42.79%,83.60-83.75%,56.67%-64.44%and 34.77%-52.45%respectively.The water quality of the outlet has been significantly improved,reaching the surface water class V water standard(except the total nitrogen).In seasonal comparison,the removal rate in summer is higher than that in winter,which may be related to the flourishing growth of plants,the large number of microorganisms and high activity in summer,which helps to absorb and degrade pollutants.(2)The removal efficiency of quinolonesMas antibiotics(QNs),sulfonamides antibiotics(SAs),macrolides antibiotics()in tail water was 80.42%and 65.21%,60.42%and 53.44%,88.82%and 63.76%respectively in winter and summer.Except for ofloxacin(OFC)and enrofloxacin(ENR),the removal rate of antibiotics in winter was higher than that in summer.The subsystem with glass greenhouse of integrated constructed wetland contributes more to antibiotic removal than open-air subsystem,and the removal efficiency of antibiotics by subsurface wetland is better than surface wetland.(3)The diversity of bacterial communities and the abundance of specific bacteria affect the removal of antibiotics and nutrients.Taxa affiliated with Dechloromonas,Nitrospira,Gemmatimonadaceae,Myxococcales,Xanthomonadales may be the key bacteria involved in antibiotic degradation.Proteobacteria and Parcubacteria may play important roles in nutrient removal in constructed wetlands.This paper is the first to explore the simultaneous removal of antibiotics and nutrients in such a large-scale integrated constructed wetland,and reveal potential functional microorganisms.The results will help to provide theoretical basis and practical guidance for the design and application of constructed wetlands.