Study On The Effect Of Halide Ions On The Formation Of Disinfection By-products In Advanced Oxidation

Advanced oxidation processes(AOPs)have the advantages of wide application range,fast reaction rate and high treatment efficiency.It is often used to remove natural organic matter(NOM)and emerging organic pollutants in water.At present,it is found that bromate and halogenated disinfection by-products(DBPs)can be produced in the process of ozone advanced oxidation when there are halogen ions(Cl^-,Br^-)in water.In this study,humic acid was used to simulate NOM.In the presence of NOM,Br^-and Cl^-at the same time,the degradation of NOM,the formation of bromate and halogenated DBPs by advanced oxidation processes such as ozone/hydrogen peroxide(O₃/H₂O₂),ozone/ultraviolet(O₃/UV),ozone/peroxymonosulfate(O₃/PMS)and ozone/hydroxylamine were studied;the effects of organic species(fulvic acid,amino acid),dosage of PMS and ozone,p H value,concentration of Cl^-and Br^-and NOM on the generation of disinfection by-products and the removal of DBPs precursors in O₃/PMS oxidation process were discussed.The method of controlling the generation of disinfection by-products was also studied.The main results are as follows:O₃combined with H₂O₂,UV and PMS enhanced the degradation of humic acid,H₂O₂and high dose PMS could inhibit the formation of bromate;while hydroxylamine could inhibit the formation of bromate,but did not effectively promote the removal of humic acid.In addition,compared with ozone alone,O₃/PMS can increase the removal rates of DOC,UV₂₅₄and DBPs precursors by 11.0%,14.7%and 21.2%,respectively.Moreover,O₃/PMS can remove halogenated DBPs,but it can be seen that the continuous increase of PMS dosage can not continuously enhance the removal effect of O₃/PMS on DBPs precursors and halogenated DBPs.Different from other oxidation technologies,halogenated DBPs were formed in the process of humic acid oxidation by O₃/PMS.With the increase of the dosage of PMS,the amount of DBPs first increased and then decreased.In addition,using fulvic acid and amino acid to simulate NOM,it was found that the type of organic matter affected the degradation of organic matter by O₃/PMS and the formation of bromate and halogenated DBPs.The UV spectra of fulvic acid and amino acid solutions before and after oxidation were scanned.The results showed that UV₂₅₄first increased and then decreased,which was related to the formation and removal of the absorption peak of organic compounds near 210 nm.When the humic acid was oxidized by O₃/PMS,the formation of bromate and halogenated DBPs was promoted by increasing the ozone dosage and p H value;when the concentration of Cl^-increased,the formation of bromate gradually decreased,the concentration of halogenated DBPs first increased and then decreased slightly,and the addition of Cl^-promoted the formation of a variety of halogenated DBPs;with the increase of Br^-concentration,bromate first increased and then stabilized,the concentration of halogenated DBPs increased;with the increased of NOM concentration,both bromate and halogenated DBPs increased at first and then decreased,and the concentration of NOM also affected the types of halogenated DBPs.The formation of bromate and halogenated DBPs was inhibited by adding ammonia nitrogen in advance,the concentration of halogenated DBPs decreased by79.7%compared with that without ammonia nitrogen,and the types of halogenated DBPs also decreased.When the humic acid was oxidized by O₃/PMS,ozone dosage,p H value,Cl^-and Br^-concentrations also affected the removal of DBPs precursors.With the increase of ozone dosage,the formation potential of DBPs gradually decreased,and the removal effect of DBPs precursors increased.Under alkaline conditions(p H 8.22,8.96),the removal effect of DBPs precursors was better.Cl^-had a certain effect on the formation potential of trihalmethane(THMs)and haloacetic acids(HAAs),but had no significant effect on haloacetonitriles(HANs).Br^-had a significant effect on the formation potential of DBPs.With the increase of Br^-concentration,the formation potential of DBPs increased,and DBPs showed the transformation from chlorinated disinfection by-products(Cl-DBPs)to brominated disinfection by-products(Br-DBPs).