Research Of THMs Formation And Its Transformation In Different Bio-treatment Processes

Wastewater reuse is serviced as one of continued and stable water resource, whichis the one of the effective means to solve the problems of water shortages. In order toensure the security of sewage discharge or recycling process, disinfection becomes anindispensable tache in sewage reuse treatment processes and also is the key measure toguarantee the water environment safety. But in recycling process, the disinfectant canreact with the organic matters, and the products may endanger the human and theecological environment. There are more kinds and amounts of organic matters in thepollutants in the city sewage than in the drinking water. In view of the research onwastewater disinfection doesn’t have a long history, so there is so much work to do. Inthis thesis, we research on the formation and transformation in the sewage recyclingprocesses, applying the NaClO as disinfectant and the trihalomethanes （THMs） as therepresentative DBPs, and then probe into the regular pattern of solubility matters to theformation and transformation. The aim of this paper is to provide the theory evidencesto reduce THMs.In this thesis, NH₄⁺-N, COD, DOC, SUVA, THMs and its precursors are tested ofinfluent, the effluent of bio treatment process and the secondary sediment ditch of thefour representative wastewater treatment plants in Xi’an City, which employ DEOxidation ditch, A²/O process, Orbal process and the Convert A²/O process,respectively. By the detection of NH₄⁺-N, COD, DOC, SUVA, THMs and itsprecursors, we can analysis the variation of the organic matters and DBPs in eachstage; by the3DEEM of each process, we can know the contents of DOM; by the resin separation technology, we can acquaintance the five fractions; by the determination ofDOC,SUVA,3DEEM and the THMFP, we can get the influence in the generation andtransformation in different bio treatment processes.The results are as follows:1. During sampling, each plant wokes regularly. After the representativebio treatment processes, the NH₄⁺-N, COD, DOC, UV₂₅₄of each process in each planthave been significantly reduced, while the SUVA and THMFP have been significantlyincreased, which is because it produces some DBPs precursors（such as SMPs） in thebio treatment;2. Monitoring results indicated in the four water plants, we get four materials:CHCl₃, CHCl₂Br, CHClBr₂, CHBr₃. There are mainly trichloromethane in the DBPs,accounting for more than90%.3. By the3DEEM, we find that there is much difference after bio treatmentprocesses, especially the Orbal oxidation ditch, increasing the fulvic like acids and thehumic acids.4. By the analysis of DOM fractions, we come to the conclusion that HIA fractioncontributes to the THMFP greatest, which has the most fulvic like acids, humic acidsand conjugated chains, and secondly is fraction HOA. So we arrive at the conclusionthat fulvic like acids and the humic acids in acid matters are the mainly THMsprecursors.5. According to the analysis of λ_0.5（λex=320nm） in each fraction, we can get theconclusion that the aromaticity of HIA is the strongest, while the HOA is weakest.Generally speaking, more conjugated bond more DBPs products. So the maximalcontribute to THMFP is HIA, secondly is HOA.