Study On The Concentration Residues And Removal Characteristics Of Substituted Diphenylamiine Antioxidants In Urban Sewage System

Substituted diphenylamine antioxidants(SDPAs)is a kind of widely used in the areas of producing rubber,plastics and high temperature functional liquid(lubricating oil,gear oil,hydraulic oil)so as to delay the oxidation of polymer compounds.SDPAs meets the conditions of the classification criteria of pops,and they have the characteristics of biological enrichment effect in the environment and genetic toxicity of aquatic organisms,so they are potentially harmful to human health and the environment.As a place where a large amount of sewage is collected,sewage plant is a kind of important point source of pollutants flowing into the environment.However,there are few studies on the regression of SDPAs in the sewage treatment system,so it is necessary to study the residual concentrations and removal characteristics of SDPAs in the sewage treatment system.In this study,10 sewage plants in northeast China were selected as research objects,and the pollution characteristics and removal rules of SDPAs in different sewage treatment processes were deeply studied through optimized pretreatment methods and instrument detection methods.Through the detection of SDPAs concentrations in the water phase and sludge phase of 10 sewage plants in two seasons(summer and winter),10 target substances were detected.The average concentration range of 10 target substances in the inlet water was 0.44~98.27 ng/L,the average concentration range of 10 target substances in the outlet water was 0.02~8.48 ng/L,and the average concentrations in the inlet water and outlet water were 237.86ng/L and 13.00ng/L.The detection rate of SDPAs in sludge of ten sewage plants was 100%,the concentration range of?SDPAs was114.67~1034.50 ng/g(dry weight),and the average concentration was 333.61 ng/g(dry weight).C8/C8-DPA,C4/C8-DPA and C8-DPA had the highest concentration in sewage and sludge of the ten substances.Compared with Canada,the concentrations of SDPAs in Chinese sewage plants are slightly lower but belongs to the same order of magnitude.The seasonal variation had no significant effect on the concentrations of SDPAs in water phase and sludge phase.The removal efficiency of?SDPAs in 10 sewage treatment plants ranges from69.2%to 99.9%,among which S-DPA1 and DS-DPA3 have the best removal efficiency.The average removal efficiencies of 10 sewage treatment plants were 96.99%and97.34%respectively,which are slightly lower than that of Canadian sewage treatment plants.Among the four process types of sewage plant,A~2/O process has the best removal effect on SDPAs,with an average removal rate of 96.88%,basically achieving the remove target,while SBR process has the worst removal effect,with an average removal rate of 87.14%,which needs to be improved.C8/C8-DPA is the substance with the highest concentration flowing into the environmental water and should be given priority attention to control.Through the detection of SDPAs in water phase,particle phase and sludge phase of each treatment unit of two sewage plants using A/O process,the concentration distribution of SDPAs among each medium,removal efficiency of each process segment and mass load flowing into the environment were analyzed.SDPAs had been detected in all media of the units in each part of the A/O process,and the detection rates of 10 target substances were 96%.The average concentrations of SDPAs in aqueous phase,granular phase and sludge were 51.90 ng/L,37.22 ng/L and 345.07 ng/g(dry weight),respectively.The total removal efficiency of 10 target substances in A/O process was90.01%,indicating the A/O process has a good removal effect on substituted diphenylamine substances,in which A/O section and secondary sedimentation tank are the main process sections.In water phase and particle phase,the average distribution coefficient of SDPAs in water phase is 58.55%,slightly higher than that in particle phase,while the concentration of SDPAs in sludge is very high,indicating that the removal of target may have relationship with coagulation/flocculation or sludge adsorption.After calculation,the annual mass weights of SDPAs discharged by the two sewage plants are 0.75 kg and 1.95 kg respectively,which have certain affect on the receiving water.