Study On The Removal Of Antibiotics And Phosphorus By Spherical Iron-manganese Oxide Fillers In Biological Detention Facility

As a typical sponge facility,biological detention facilities can not only flexibly integrate into the landscape to beautify the environment,but also reduce rainwater runoff and improve runoff quality.In addition to the presence of conventional pollutants such as COD,NH₄⁺-N,NO₃^--N,TP,etc.in rainwater runoff,it is also one of the potential pathways for the spread and diffusion of many new pollutants such as antibiotics in the environment.Therefore,it is crucial to strengthen the research and development of bioretention facility fillers and improve the removal of antibiotics and conventional pollutants.Iron manganese oxides not only have good adsorption and oxidation effects on pollutants,but also have the advantages of low price and environmental friendliness.Loading them into biological detention facilities can strengthen the catharsis of rainwater runoff,which is of great significance for the recovery and reuse of rainwater resources.In this study,the co-precipitation method was used to prepare spherical iron-manganese oxide filler.The antibiotic norfloxacin,which has the widest chronic toxic zone in the Weihe River,and the conventional pollutant phosphorus,whose removal effect in rainwater runoff is greatly affected by the selection of filler,were selected as the research objects.The best preparation method of the filler was optimized,and the filler before and after the reaction was characterized.The removal characteristics of norfloxacin and phosphorus by spherical iron-manganese oxide fillers under different influencing factors were investigated,and kinetic fitting was carried out.The self-made spherical iron and manganese oxide filler was filled into the biological detention facility to improve it,and the removal effect of the improved biological detention facility on norfloxacin and conventional pollutants was explored under the conditions of different rainfall return periods,rainfall intervals and influent concentration,as well as the control effect on the total amount of rainwater runoff and the peak value of rainwater runoff under different rainfall return periods.The main research results are as follows:（1）When the molar ratio of iron to manganese was 4:1,the concentration of polyvinyl alcohol was 7%and the particle size was 4 mm,the spherical iron-manganese oxide filler prepared had the best removal effect of 81.10%on norfloxacin,and the removal rate of phosphorus could also reach 96.20%.The characterization results showed that there was redox reaction between the filler and norfloxacin,but no redox reaction between the filler and phosphorus.（2）In norfloxacin solution with different initial concentrations,the removal rate of norfloxacin was more than 70%when the reaction reached equilibrium.When the pH of solution was 3～9,the removal rate of norfloxacin was 72.13%～82.30%.With the reaction temperature increasing from 15℃to 35℃,the removal rate of norfloxacin by filler increased from 78.39%to 82.69%.The presence of other substances in the composite solution had a certain inhibitory effect on the removal of norfloxacin by filler,and the removal rate of Norfloxacin was reduced by 8.79%.The removal process of norfloxacin by filler accords with the quasi-first-order kinetic model,and the reaction rate constant k_obs is 0.00454 min^-1.（3）When the initial concentration of phosphorus solution was 5 mg/L～25 mg/L,the equilibrium removal rate of phosphorus could reach more than 82%.When the pH of the solution was 3～9,the removal rate of phosphorus was more than 88%.When the reaction temperature increased from 15℃to 35℃,the removal rate of phosphorus increased from91.33%to 97.80%,indicating that the increase of temperature was conducive to the reaction.The presence of other substances in the composite solution had no inhibitory effect on the removal of phosphorus by the filler.The adsorption process of fillers is more consistent with the quasi-second-order kinetic model and Langmuir model.（4）In order to verify the practical application ability of the spherical iron manganese oxide filler,the biological retention facility with the spherical iron manganese oxide filler layer and the biological retention facility with the sand layer were compared under different rainfall conditions to remove pollutants.It was found that the removal rate of norfloxacin was increased by 25.19%～36.27%by the improved biological retention facility.The removal rate of TP,NH₄⁺-N,NO₃^--N and COD were increased by 15.32%～18.90%,25.94%～29.34%,12.60%～18.08%and 7.32%～20.10%respectively.Under different rainfall recurrence periods,the total runoff reduction rate and peak reduction rate of the biological detention facilities filled with spherical iron and manganese oxides increased by 12.82%～32.15%and14.93%～36.89%,respectively,compared with the biological detention facilities filled with sand only.