Research On Distribution And Ozonation Characteristics Of Nitrosamines In Wastewater Treatment Plant Effluent

Disinfection plays a crucial role in advanced treatment of secondary effluent recycling process.However,in recent years,Studies have found that the carcinogenic properties of nitrosamine-based disinfection by-products pose a greater threat to human health than halogenated disinfection by-products such as haloacetic acid.Therefor,the paper established a method for the determination of nitrosamines disinfection by-products,analyzed the distribution characteristics of nitrosamines disinfection by-products and discussed the ozonation treatment characteristics for the disinfection of nitrosamines in WWTP effluents.It provides a theoretical basis for the control of nitrosamines disinfection by-products in wastewater treatment.Through experimental exploration and comparative analysis experiments,a method for the determination of optimal nitrosamines disinfection by-products was established..After evaluation,the linear calibration ranged from 5 up to 150ng/L?r²=0.997-0.999?,sample recovery rate was 56.9-94.1%.The results show average concentrations of NPYR 250ng/L,NDIP 45.96ng/L,NDBA 31.17ng/L,NDMA 28ng/L,NMEA 4.92 ng/L,NDPA 4.71ng/L and NDEA 2.15 ng/L in the WWTP effluent use this method.Analysis of ozonation characteristics of nitrosamines in secondary effluent water can be obtained:Although ozonation can increase the concentrations of nitrosamines in WWTP effluents,especially NPYR,NDIP,NDBA and NDMA,the nitrosamine formation potential decreases with the increase of ozone dosage.Moreover,the magnitude of reduction of the nitrosamine formation potential was more significant than its further increment.The difference between these two effects is more notable at high ozone dosages.Thus,ozonation can enhance the removal of the nitrosamine formation potential,which can reduce the formation of nitrosamine disinfection by-products during downstream advanced and disinfection processes to guarantee the safety of the reclaimed water.Based on the experimental results of the increase in the concentration of nitrosamines in WWTP effluents due to ozonation,Taking NDMA as an example,four substances such as butyryl hydrazide?DMZ?,1,1-dimethylsemicarbazide?DMSC?,dimethyl hydrazine?FDH?and acetone dimethyl hydrazine?ADMH?were selected as NDMA precursors.Explored the role of ozone and precursors in the reaction process,influencing factors,and the main oxidants in the reaction.In order to reduce the production of nitrosamines by controlling the reaction conditions.The experimental results show that the initial concentration of substrate,pH,and ozone concentration all have a certain influence on the conversion of precursors to nitrosamines disinfection by-products.When ozone concentration was 0.5 mM,C₀=20?M,and pH=7,the yield of NDMA production from the four precursors was the highest,which was 69.6%,63.1%,92.7%,and 64.2%,respectively;when the ozone concentration was 0.25 mM,C₀=100?M,and pH=3.8,the yield of NDMA was the lowest,6.6%,11.2%,10.7%,and18.2%,respectively;At the same time,it can be preliminarily considered that both O₃and·OH were involved in the conversion of precursors to NDMA,but the main oxidant is O₃.