Study On The Formation Mechanism Of Halogenated By-products In The Process Of O₃/PMS Oxidation Of Characteristic Organic Matter In Bromine-containing Source Water

During chlorination and disinfection of water plants,organic matter in source water will react under the action of halogen ions such as Br^-and Cl^-to generate halogenated disinfection by-products(DBPs)that are toxic and harmful to human body.In the past two years,due to the spread of the new coronavirus,the large-scale dosing of chlorine-containing disinfectants in water plants has further increased the production of DBPs in water.In addition,the Br^-concentration in the lower reaches of the Yellow River in my country is about 110-200?g/L.In response to high Br^-water,the ozone advanced oxidation technology can effectively control the DBPs precursors on the one hand,and the strong oxidizing property of ozone will also promote water.Br^-generates bromate and brominated disinfection by-products.Studies have shown that the synergistic effect of bromate and halogenated DBPs enhances the toxicity of bromine-containing water.Based on this,this thesis uses ozone/persulfate technology to analyze the characteristic organic compounds in water source water:humic acid,bisphenol A,Microcystis aeruginosa extracellular organic matter and aeruginosa microbes.Intracellular organic matter of Cystis albicans is represented.Under the condition of single organic matter,pure water and water were used to conduct ozone oxidation static experiments.The effects of factors such as PMS,ozone,Br^-,Cl^-and pH value on O₃/PMS system oxidizes organic matter to generate DBPs and removes DBPs precursors.The main findings are as follows:(1)The four organic compounds have different characteristics of DBPs formation under different oxidation conditions.Halogenated DBPs were not detected in the oxidation of BPA and IOM by O₃/PMS.Decreasing PMS concentration and increasing ozone concentration,pH value and bromide ion concentration during EOM oxidation can promote the formation of trihalomethanes(THMs);higher PMS concentration,ozone concentration,pH value and chloride ion concentration can promote haloacetic acid(HAAs)generation.Lower chloride ion concentration,higher ozone concentration and bromide ion concentration can promote the generation of THMs when oxidizing HA;higher ozone concentration,PMS concentration and bromide ion concentration can promote the generation of HAAs.The amount and type of haloacetonitrile(HANs)produced during the oxidation of EOM and HA were not affected by external factors,and the unit production amount was less than 2.77?g/(mg DOC).(2)The change of Br^-/Cl^-ratio in the system when O₃/PMS oxidizes characteristic organic matter has an important influence on the generation amount and type of disinfection by-product formation potential(DBPsFP).When EOM,IOM,BPA and HA were oxidized by O₃/PMS,the types of DBPsFP generated in the oxidized system increased with the increase of chloride ion concentration.The effect of ion concentration on the production of DBPsFP varies.Among them,when EOM was oxidized by O₃/PMS,the formation potential of trihalomethane(THMsFP)and haloacetic acid formation potential(HAAsFP)increased with the increase of Cl^-concentration,while the formation potential of haloacetonitrile(HANsFP)was not affected by the concentration of Cl^-Influence.The DBPsFP of the other three kinds of organic compounds showed fluctuating changes with the increase of Cl^-concentration.When EOM,IOM,BPA and HA were oxidized by O₃/PMS,the concentrations and species of THMsFP,HAAsFP and HANsFP after oxidation increased with the increase of bromide ion concentration.(3)When O₃/PMS oxidizes characteristic organics,the concentration of oxidant has an important effect on DBPsFP.When EOM,IOM,BPA and HA were oxidized by O₃/PMS,THMsFP and HAAsFP decreased first and then increased with the increase of PMS concentration after oxidation,while HANsFP showed different laws.Among them,HANsFP showed a trend of first decreasing and then increasing with the increase of PMS concentration after IOM oxidation,and the other three organic compounds showed a fluctuating change with PMS concentration.In addition,when EOM,BPA and HA were oxidized by O₃/PMS,THMsFP and HAAsFP decreased with the increase of ozone concentration after oxidation,while HANsFP was not affected by ozone concentration.During IOM oxidation,DBPsFP decreased with the increase of ozone concentration.(4)When EOM,IOM,BPA and HA were oxidized by O₃/PMS,the types of DBPsFP generated after oxidation were not affected by pH value,but pH value had different effects on the amount of DBPsFP generated.When O₃/PMS oxidized EOM,BPA and HA,the THMsFP generated after oxidation increased first and then decreased with the increase of pH value.After IOM oxidation,THMsFP decreased first and then increased with the increase of pH value.O₃/PMS oxidized EOM and IOM.,the oxidized HAAsFP decreased with the increase of pH value,and the oxidized HAAsFP of BPA and HA was not affected by pH value.(5)In the process of O₃/PMS oxidation of EOM and HA,increasing ozone concentration,pH value and bromide ion concentration is beneficial to the formation of bromate.The formation of bromate first increases and then decreases with the increase of PMS concentration.Bromate formation has a certain inhibitory effect.In addition,during the IOM oxidation process,Br^-and Cl^-were found to promote the removal of ammonia nitrogen.