Study On The Formation And Mathematical Simulation Of Different Precursors Of Typical Disinfection Of N-nitrosodimethylamine

With the research on water disinfection by-products,the generation of disinfection by-products has gradually become a research hotspot in recent years.Based on the genotoxicity and carcinogenicity of disinfection by-products,it is necessary to conduct in-depth research on the generation mechanism and control the generation of disinfection by-products from the process.In this study,N-nitrosodimethylamine（NDMA）,a new type of disinfection by-product,was selected as the research object.In this study,11 typical NDMA precursors were selected,oxidized with chloramine and their formation potential was measured.The results showed that during the oxidation of 11 precursors by chloramine,the NDMA generated by the oxidation of N,N-Dimethylbenzylamine,dimethylamine,trimethylamine and3-Dimethylaminopropylamineshowedanincreasingtrend.N,N-Dimethylbenzylamine generates NDMA at the fastest rate under the conditions of oxidation of chloramine,and the rate constant is 5.6×10^-3.The concentration of NDMA generated by the oxidation of other precursors by chloramine shows a decreasing trend.At the same time,the influence of coexisting ions in water on the formation of NDMA under chloramine oxidation conditions was explored.Among them,Br^-,SO₄^2-and NO₂^-can inhibit the formation of NDMA,and the inhibition ability is ranked from strong to weak as NO₂^->Br^->SO₄^2-.As the concentration of NH₄⁺gradually increased to 50 m M,the formation potential of NDMA showed a trend of first increasing and then decreasing.When the NH₄⁺concentration was 20m M,the NDMA concentration was as high as 13.41 mg/L,which was twice the NDMA concentration in the blank aqueous solution;when it was increased to 50 m M,the NDMA concentration decreased to 6.08 mg/L.In order to further study the quantitative relationship between other water quality factors and NDMA generation,this paper selected three types of typical NDMA precursors and fitted the mathematical model of NDMA generation under the action of chloramine and ozone disinfection.For the two disinfection methods,the overall goodness of fit R²of the nonlinear regression analysis is greater than that of the linear regression,and the significance P values of the variables are both less than 0.1.In the chloramine disinfection process,the parameter p H does not show a single linear relationship with the formation of NDMA.For ozone disinfection,within a certain concentration range,the ozone concentration is negatively correlated with the generation of NDMA,so ozone can effectively inhibit the generation of NDMA.Combined with the regression model,the water quality parameters can be adjusted for the water treatment process,thereby reducing the generation of NDMA in the process.