Toxic Effect And Mechanism Of Typical Emerging Pollutants On Phosphorus Accumulating Organism In Wastewater Treatment

The extensive development and application of antibiotics and nano materials not only bring convenience and progress to human society,but also bring environmental risks due to human abuse.With human activities,antibiotics and nano materials will enter the municipal sewage treatment system with municipal sewage as the carrier.Activated sludge process is widely used in secondary biological treatment of sewage.Antibiotics and nano materials will inevitably contact with bacteria in activated sludge.Under the combined effect of these two kinds of pollutants,the effect on functional bacteria in sludge and the complex mechanism still to be studied.In this study,phosphorus accumulating organisms which is the main functional bacteria in the process of dephosphorization of sewage were selected as the object microorganism,nano ZnO,ciprofloxacin,norfloxacin,sulfamethazine and sulfamethoxazole were selected as pollutants,individual pollutant experiment and complex pollutants experiment were designed to explore the toxic effect and mechanism of antibiotics and nano ZnO.In this study,the ability of phosphorus and CODcr removal of phosphorus accumulating organisms was used to reflect the toxicity of selected pollutants.The toxic mechanism of complex pollution of nano ZnO and antibiotics on phosphorus and CODcr removal of phosphorus accumulating organisms was analyzed through the metabolic transformation process of main polymers in polyphosphate accumulating bacteria and the characterization of compound products between nano ZnO and antibiotics under sterile conditions.It was found that nano ZnO and norone antibiotics（ciprofloxacin and norfloxacin）had significant toxic effects on phosphorus accumulating organisms,while sulfamethazine and sulfamethoxazole had no significant toxicity.In addition,the toxic effect of nano ZnO combined with quinolones（ciprofloxacin and norfloxacin）was antagonistic,while that of nano ZnO combined with sulfamethazine and sulfamethoxazole was not significant.This is because at the cellular level,the combination of nano ZnO with ciprofloxacin and norfloxacin has an obvious antagonistic effect on the inhibition of the synthesis of polyphosphate;when nano ZnO is combined with sulfamethazine and sulfamethoxazole,there is no significant composite effect on the synthesis of polyphosphate.Finally,in the sterile water,through the UV full wavelength scanning,X-ray diffraction and infrared spectrum analysis of the composite products of nano ZnO and antibiotics,it is found that the antibiotics can coordinate with the Zn²⁺released by nano ZnO.The production of complexes changes the molecular structure of antibiotics,affects the normal play of their antibacterial effect,and thus shows different complex effects.