| The disinfection by-products produced by chlorination disinfection process in water purification plants are a threat to human health.Natural or ganic matter(NOM)in water is the main precursor of DBPs.In addition,in recent years,due to seawater intrusion,salt tide backfilling and other reasons,there are certain concentrations of bromine and iodine ions in the source water.Their presence will interact with NOM and disinfectants to produce brominated and iodine disinfecti on by-products which are more carcinogenic than chlorinated disinfection by-products.This poses a new challenge to the safety of drinking water.In order to accurately grasp the existing status of water quality and disinfection by-products generation potential in Xijiang River Basin,the water quality indicators such as dissolved organic carbon,TN and DBPFP in the reservoir water were periodically detected,the change of concentration of each substance with sampling location and sampling time was analyzed,and the cor relation between trihalomethane generation potential,haloacetic acid generation potential and DOC was analyzed.The results show that the water quality indexes s how obvious seasonal variation.The water quality indexes such as DOC,TN,NH3-N,UV254 are on the high side in winter salty tide period(December to February).During the sampling period of raw water disinfection by-products,trichloromethane and dichloroacetic acid accounted for the highest proportion in trihalomethane and haloacetic acid respective ly,and the concentration of other disinfection by-products were higher in the saltwater period.During the upstream of the saltwater period,the concentration of chloride and ammonia nitrogen in the influent will be increased.The urban drinking water con tains high concentration of chloride.At the same time,the pollutants in the downstream of the water plant will be upstream together,so as to improve the water quality index in the raw water and the generation risk of disinfection by-products.The correlation between THMFP and DOC is good,and that between haafp and UV 254 is good.Therefore,DOC can be used to characterize the precursors of trihalomethane and haloacetic acid.In addition,it is generally believed that the precursor of disinfection by-products mainly comes from the natural organic matter in the water,In this study,the molecular weight distribution characteristics and three-dimensional fluorescence spectrum of dissolved organic matter in Xijiang water source of Zhongshan City were studied by means of molecular weight distribution and three-dimensional fluorescence.The organic matter in raw water is divided into hydrophilic,weak hydrophobic and strong hydrophobic components by hydrophilic and hydrophobic separation,and the main precursors of two disinfection by-products,trihalomethane and haloacetic acid,are identified,The influence of the characteristics of organic compounds in Xijiang water source on the formation of disinf ection by-products was studied.The results show that the majority of organic matter in the raw water of Xijiang River in Zhongshan is 3-5k Dalton,followed by the component with molecu lar weight less than 3K Dalton;Most of the organic compounds in water source are aromatic proteins;The content of hydrophilic organic mat ter in the dissolved organic matter of raw water is higher than that of hydrophobic organic matter;Hydrophilic organic compounds are the main precursors of dichlorodibromomethane,dichlorodibromomethane,monochlorobromoacet ic acid and dibromoacetic acid,Trichloromethane,dichloroacetic acid and trichloroacetic acid are mainly formed by highly hydrophobic organic compounds.In this paper,the raw water with different concentration ratio of bromine and iodine ions was disinfected with liquid chlorine and sodi um hypochlorite with different reaction time and chlorine dosage.The results showed that the contents of bromotrihalomethane and iodide trihalomethane produced in the process of chlorine disinfection were affected by chlorine dosage,reaction time and bromine ion concentration.Among them,the production of Br-THMs can be effectively controlled by controlling the amount of chlorine,the reaction time and the concentration of bromine ions.Compared with liquid chlorine,sodium hypochlorite can produce more Br-THMs as disinfectant;The total I-THMs production increased first and then decreased with the increase of chlorine dosage,and reached the maximum when the chlorine dosage was about 15 mg/L;I-THMs were rapidly generated within 2 hours,and then the growth rate slowed down with the increase of reaction time;the total I-THMs production increased first with the increase of iodine ion amount,and with the increase of iodine ion concentration,the promotion effect of liquid chlorine on the formation potential of i-thms was more obvious.Compared with liquid chlorine,sodium hypochlorite can generate less I-THMs as disinfectant,so using sodium hypochlorite as disinfectant can effectively control the production of I-THMs. |
PDF Full Text Request