Precursors Recognition And Risk Warning Of Chloral Hydrate For Water Treatment Plant

Chlorination process for drinking water can produce a variety of disinfection by-products(DBPs)which are harmful to human health,in which chloral hydrate(CH)is the third largest class of DBPs after trihalomethanes(THMs)and haloacetic acids(HAAs).At present,nevertheless,there isn't the overall risk assessment of DBPs in water purification plants,and the study on CH precursors is not consummate.Furthermore,risk early warning methods applied to the actual engineering for CH are absent.The risk level of DBPs in a southern city in China was evaluated in this paper,and the representative source water was selected.Moreover,the characterization methods of ultraviolet spectroscopy and fluorescence spectroscopy and the separation means based on ultrafiltration and resin were applied to analyze the basic component of the precursors to identify the main precursors.Simultanoously,the kinetic study was carried out which paved the way for the research of CH formation mechanism.Ultimately,the methods of CH risk early-warning were established to provide guidance for CH control,which could have a universal applicability in some degree.The results indicated that:The excessive risk of DBPs exceeding criterion in the effluent water of the main waterworks was at a relatively low level in generally,with a certain seasonal variation trend,and it was comparatively higher in the high-temperature summer and the jumped-temperature winter.This was especially true for CH.The hydrophilic organics(HiM)and the organics with molecular weight(MW)>30 KDa were the main CH precursors components.While the weakly hydrophobic acid organic compounds(WHoA)exhibited the highest reaction activity with chlorine,in which the content of the soluble microbial products(SMP)that is classified as endogenous organic matter was dominant,i.e.,the SMP was the most important precursors.In addition,the aromatic protein(AP)substance was also the main CH precursor.The formation rate of CH and the decay rate of chlorine consumption were almost the same during the chlorination of each component.The fast reaction phase was the first 24 hours of chlorination,and the correlation coefficient of the kinetic model was mostly above 0.91.The production of CH was proportional to the square of the chlorine consumption,and they had a good relevancy.Morover,the production of CH,as funtion of ?UV265,fitted exponential expressions.Thus,the risk early warning of CH based on the chlorination consumption and ?UV265 can be conducted.In this paper,the early warning method was suitable for the raw water which pH range was 7,water temperature range was 25?35 0C and the chlorine dosage range was Cl2:DOC=1:1?3:1.In addition,since the water quality of different water sources has a great impact on the two early warning methods,there is a need to adjust the model for the other specific water sources according to the actual water treatment process to achieve the scientific early warning of CH,guiding the actual production.