Removal Efficiency And Mechanism Of Ofloxacin And Cr(Ⅵ) Enhanced By Iron-Carbon Micro Electrolysis Coupled Vertical Subsurface Flow Constructed Wetland

In recent years,humans have used a large number of antibiotics and heavy metals for medical treatment,livestock and poultry breeding,industrial production,etc.The residual antibiotics and heavy metals enter the water body under the action of rain,which seriously endangers human health.Therefore,how to effectively solve the problem of antibiotics and heavy metal pollution in water bodies is of great significance.Constructed wetlands(hereinafter referred to as CW)have been successfully used in the treatment of various wastewaters because of their green,economical and good purification effects.Poor performance,etc.Iron-Carbon micro electrolysis(hereinafter referred to as ICME)has been successfully applied to printing and dyeing wastewater,pharmaceutical wastewater,heavy metal wastewater,chemical wastewater,etc.Therefore,problems such as poor removal effect of constructed wetlands can be solved by iron-carbon micro-electrolysis technologyIn this study,an enhanced constructed wetland(CWB system)was constructed based on Iron-Carbon micro electrolysis(hereinafter referred to as ICME)technology,and the effect of CWB system and traditional constructed wetland(CWA system)on the removal of ofloxacin(hereinafter referred to OFL)and hexavalent chromium(hereinafter referred to as Cr(Ⅵ))were studied,the removal performance of conventional pollutants and the changes in microbial community structure before and after the addition of OFL and Cr(Ⅵ)were analyzed,and the ICME enhanced CW system was finally clear about the removal of OFL and Cr(Ⅵ).Mechanism of he removal of OFL and Cr(Ⅵ)and the effect of OFL and Cr(Ⅵ)addition on microbial community structure were studied.(1)The changes of the removal performance of OFL and Cr(Ⅵ)under the three influencing factors of reaction time,initial pH value and concentration ratio were analyzed.The results showed that the ICME material had the best removal effect of OFL and Cr(Ⅵ)when the reaction time was 6 h,the initial pH was 4,and the concentration ratio was 2:1,and the removal rates were 90.85%and 94.7%,respectively.The characterization results show that the ICME materials have different iron oxidation states and chromium hydroxides after the experiment.It can be seen that the micro-electrolysis reaction occurs.(2)The long-term purification effect of OFL and Cr(Ⅵ)of each CW system was clarified,and the effect of addition of OFL and Cr(Ⅵ)on the removal of conventional pollutants was discussed.The results showed that the removal rates of OFL and Cr(Ⅵ)in the CWB system were 25.8%and 53.5%higher than those in the CWA system,respectively,which proved that ICME could enhance the removal of OFL and Cr(Ⅵ)in the CW system.(3)The structural characteristics and diversity of microbial communities before and after the coexistence of OFL and Cr(Ⅵ)were analyzed.The results showed that the number of dominant bacteria in the microbial community of each CW system decreased significantly when OFL and Cr(Ⅵ)coexisted.,which indicated that the coexistence of OFL and Cr(Ⅵ)had a greater impact on the diversity of microorganisms.Proteobacteria,Acidobacteriota and Bacteroidota are dominant strains before and after the coexistence of OFL and Cr(Ⅵ)in each CW system,which proves that these three strains have good stain resistance ability,the relative abundance of Acidobacteria and Bacteroides in CWB system is higher than that in CWA system,because the above two bacteria can increase the electrical activity.Therefore,ICME can well enhance the CW system to remove OFL and Cr(Ⅵ).