Determination Of Nine N-nitrosamine4s In Water Using Ultra Performance Liquid Chromatography Tandem Mass Spectrometry And Removal Of N-nitrosamines Formation Potential Of Wastewater Effluent By Enhanced Coagulation

Secondary wastewater effluent contains relatively high concentrations of naturalorganic matter. If it is directly disposed to natural water sources, drinking watersources may be polluted. After chlorine and chloramine disinfection, polluted waterwill generate harmful disinfection by products (DBPs). In recent years, lots ofattentions were paied to N-nitrosamines because of its high carcinogenic andteratogenicity. This paper focuses on the following two parts:（1）A detection method for nine nitrosamines in water has been proposed usingultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS).And the qualitative and quantitative ions of nine N-nitrosamines in the MRM modewere determined. After comparison of different mobile phases, the performancebetween two columns and different reconstitution solvents,10mmol/L ammoniumbicarbonate water solution and methanol were used as mobile phases. A coconutCharcoal column was selected as pre-treatment SPE column and ultrapure water wasselected as reconstitution solvent. Based on the optimum sample pretreatmentprocedures and optimum instrument conditions, standard calibration curves for all theanalytes were established， the linear calibration ranged from5up to150ng/L(r2=0.997-0.999). The limits of detection (LODs) and limits of quantitation (LOQs) forthe nine nitrosamines were in the range of1.34-2.82and4.02-8.46ng/L, respectively.The intra-and inter-day relative standard deviations (RSD) were in the range of3.48-8.37%and2.81-7.5%, respectively. The method recoveries were in the range of 80.4-109.6%for the three kinds of different matrix water samples.（2）Al2(SO4)3and FeCl3were used as coagulants to treat the secondarywastewater effluent. Its effects on purification of wastewater and the formationpotential of N-nitrosamine have been studied. After enhanced coagulation of thewastewater, the N-nitrosamines reduced from four kinds (NDMA, NMEA, NDEA andNPIP) to only two kinds (NDMA and NPIP). Based on measurements of turbidity,DOC, UV254and fluorescence intensity and the formation potential of N-nitrosamines,the optimal dosages of Al2(SO4)3and FeCl3were0.135and0.27mmo/L, respectively.The optimum coagulation pH of Al2(SO4)3and FeCl3were6.0and5.5, respectively.Under optimal conditions, the removal of turbidity, DOC, UV254were71.3%and71.1%,33.1%and51.6%,28.5%and45.7%, respectively. With the increase of dose ofthe coagulants, the curve of N-nitrosamine formation potential first increased, thendecreased. Compared with the maximum formation during the coagulation, theformation potential of N-nitrosamines was reduced significantly under the optimalcoagulation conditions. For chlorination, after enhanced coagulation by Al2(SO4)3, theformation of NDMA, NPIP were removaled by53.3%and55%. For chloramination,after enhanced coagulation by Al2(SO4)3, the formation of NDMA and NPIP wereremovaled by58.8%å'Œ64.8%, respectively. For chlorination, after enhancedcoagulation by FeCl3, the formation of NDMA, NPIP were removaled by58.9%and38.1%, respectively. For chloramine, after enhanced coagulation by FeCl3, theformation of NDMA and NPIP were removaled by42.5%and51.3%, respectively.Comparing with uncoagulated samples, when the dosages of the aluminum sulfate was0.24mmol/L, after chlorination, NDMA and NPIP removal rates were20.5%and14.3%; after chloramination NDMA and NPIP removal rates were29.4%and17.6%.When the dosages of the aluminum sulfate was0.75mol/L, after chlorination, NDMAand NPIP removal rates were32.5%and33.4%; after chloramination NDMA andNPIP removal rates were6.9%and12.2%.