| Halogenated benzoquinones（HBQs）,as an emerging disinfection by-product,have been paid more and more attention in recent years.Although HBQs are only ng level in drinking water,their toxicity is nearly a thousand times stronger than common trihalomethanes（THMs）and haloacetic acids（HAAs）,and there is a huge potential threat to drinking water safety.There are relatively few researches on HBQs in China.Therefore,it is necessary to investigate,analyze and remove the HBQs generated in each water source.Firstly,the water quality characteristics,organic matter components and the generation of disinfection by-products in six water sources（Queshan Reservoir,Nanjiao Reservoir,Yihe River Water,Wohushan Reservoir,Donghu Reservoir,and Dongpinghu Reservoir）in different seasons were investigated,and the main The composition and Pearson correlation coefficient were used to analyze the correlation between different water quality characteristics and the generation of disinfection by-products.The results show that the water quality of the South-to-North Water Transfer（Donghu Reservoir,Dongpinghu Reservoir）is poor,and the water quality indicators(DOC,UV254,conductivity,turbidity)are relatively high.The water quality of River water（Yihe water）,mountain water（Wohushan Reservoir）and the Yellow River Diversion（Nanjiao Reservoir,Queshan Reservoir）is good.Three-dimensional fluorescence and LC-OCD were used to analyze the organic components of different water sources.The organic matter in the water from the South-to-North Water Diversion and the mountain water was dominated by fulvic acid,the water from the Yellow River was dominated by aromatic proteins,and the water from the Yi River was dominated by microbial metabolites（SMP）.The water sources are dominated by hydrophilic organic matter（CDOC）.The levels of HBQs precursors in river water and mountain water stations were higher,and the levels of THMs in the South-to-North Water Diversion project were higher.Seasons have similar effects on water quality in different water sources,and the water quality is better in winter.The results of principal component and Pearson correlation analysis were basically consistent.Water quality characteristics can reflect the formation of trihalomethanes,but it is difficult to reflect the formation of HBQs.The SMPs and aromatic proteins in the organic fractions were highly correlated with HBQs,and the trihalomethanes were highly correlated with organics with medium and macromolecules and higher humification.It shows that the precursors of HBQs are mostly small molecules and aromatic organics,while trihalomethanes are medium and macromolecular organics.Then,the specific precursor tyrosine was used to conduct the experiment of the influencing factors of HBQs generation,and the influence of different influencing factors（p H,amount of chlorine,amount of bromine,reaction time,and concentration of precursors）on the generation of HBQs from tyrosine was investigated.The pathway of tyrosine to 2,6-dichloro-1,4-benzoquinone（DCBQ）was analyzed and verified by means of Fourier transform infrared and Orbitrap high-resolution mass spectrometry.The results show that the reaction rate of tyrosine to generate HBQs is very fast,and the maximum amount of HBQs can be generated in a short time;the optimum p H of tyrosine to generate HBQs is 6-7;the amount of HBQs generated from tyrosine basically increases with the increase of chlorine addition and precursor concentration,but too much free chlorine and tyrosine would decompose HBQs;bromide ions would increase the generation of brominated HBQs and reduce the generation of chlorinated HBQs.The way of chlorination of tyrosine to generate DCBQ is roughly as follows:tyrosine decomposes phenol,and then phenol generates 2,6-dichlorophenol,and then continues chlorination to generate 2,4,6-trichlorophenol,and then 2,4,6-Trichlorophenol as an intermediate product was further oxidized by hypochlorous acid to form DCBQ.Finally,the combination of potassium permanganate pre-oxidation,coagulation and pre-oxidation enhanced coagulation was used to treat the actual water body（Yellow River water,South-to-North Water Diversion）,and the treatment of disinfection by-product precursors and water quality parameters by different treatment methods was compared.The results were characterized by three-dimensional fluorescence,parallel factor analysis,LC-OCD,Zeta potential and changes in floc particle size.The results show that pre-oxidation enhanced coagulation is the best treatment method among the three treatment methods,and the removal rate of water quality indicators and disinfection by-product precursors is increased by 5-15%compared with coagulation.Three-dimensional fluorescence,parallel factor analysis and LC-OCD were used to characterize the organic matter before and after treatment.The results showed that the removal of organic matter by pre-oxidation enhanced coagulation was still dominated by the removal of macromolecular organic matter,and the removal of small molecular organic matter was limited.The water source of the South-to-North Water Diversion Project is rich in organic matter,and the effect of pre-oxidation enhanced coagulation on the water source of the Yellow River is better than that of the water source of the South-to-North Water Diversion Project.The Zeta potential and floc particle size of pre-oxidation enhanced coagulation were larger than those of coagulation treatment,indicating that pre-oxidation can effectively assist coagulation,increase the volume of flocs formed in the subsequent coagulation process,and improve the coagulation effect. |
PDF Full Text Request