Degradation Of Sulfonamides By Ultraviolet/electrochemical Oxidation And The Effects Of Treated Effluents On Microbial Community

With the increasingly severe organic pharmaceutical pollution in the environment,the risks to aquatic ecosystems are also increasing.Therefore,it is urgent to seek an effective treatment method that is practical for organic pharmaceutical.In this study,the degradation of three sulfonamides were investigated by combining ultraviolet(UV)photolysis(wavelength of 254 nm)with electrochemical oxidation technology.The degradation mechanism of the three sulfonamide antibiotics was evaluated under different conditions by changing experimental parameters.Meanwhile,to assess the potential risks of the treated effluent to the aquatic environment,the impact on microbial communities in surface water was also evaluated.The main conclusions are as follows:(1)The anode material determined the intensity of the electrochemical oxidation process.The electrode with strong chlorine evolution could generate more free chlorine and promote the degradation of sulfonamides in the system.In addition,the current(current density)determined the effect of electrochemical action.With the increased of current intensity,the yield of free chlorine increased gradually,which greatly speeded up the degradation rate of sulfonamides and slightly reduced the overall energy consumption rate.(2)The effect of aeration in the reaction process was evaluated.The results showed that aeration had a small promotion effect on the effect of UV photolysis of some sulfonamides,but the hydraulic interference of aeration seriously inhibited the formation of free chlorine in the electrochemical oxidation process,thus greatly reducing the overall degradation efficiency.(3)Due to the different hydrolytic distribution coefficients of sulfonamides,the degradation effects of UV photolysis and electrochemical oxidation on sulfonamides with different forms(cationic,neutral,and anionic)are also different.In general,the combined process of UV/electrochemical oxidation had a better degradation effect on sulfonamides than single UV photolysis or single electrochemical oxidation and was more suitable for the real wastewater treatment under various p H environment conditions than the single treatment process.(4)The degradation effect of sulfonamides was discussed by using real surface water samples.The results showed that organic matter and ammonia nitrogen in surface water might consume part of the active substances(mainly free chlorine),thus reducing the degradation effect of sulfonamides.(5)The addition of photocatalyst could reduce the light transmittance of the solution,leading to the reduction of UV photolysis,which would reduce the degradation effect of sulfonamides that easy to be degraded by UV photolysis.Therefore,the addition of photocatalyst should be judged according to the degradation preference of pharmaceuticals.(6)The treated effluent had different degrees of influence on the richness and diversity of microbial in surface water,especially after a period of treatment.The richness and diversity of microbial was significantly reduced,which could be related to the degradation products of sulfonamides.After prolonged the treatment time,the influence of effluent on microbial community could be greatly decreased,thus reducing the harmful to water environment.