Study On DBP Formation Characteristics And Control Technology Using DOM As Precursors In Dry And Wet Deposition

The safety of drinking water is a major livelihood issue related to thousands of households.In order to protect the microbiological safety of drinking water,it is necessary to disinfect the drinking water,but during the disinfection process,the dissolved organic matter(DOM)in the drinking water will react with the disinfectant to generate disinfection by-products(DBPs)that are toxic to the human body.In order to ensure the safety of drinking water,it is necessary to control DBPs in drinking water.DOM in the water sources has a direct relationship with the generation of DBPs.Controlling DOM in drinking water before disinfection is the most effective way to control DBPs.Atmospheric sources of DOM also have important contributions to surface water sources.Studying the characteristics of atmospheric sources of DOM has important implications for the control of DBPs.In addition,due to the scarcity of water resources,rainwater as an alternative drinking water source has a long application history at home and abroad,but microbial problems are still one of the main causes of poor rainwater quality,and it will deteriorate further during rainwater storage,therefore,it is very necessary to disinfect rainwater and maintain of rainwater containing an appropriate amount of residual chlorine,but this will also lead to the risk of DBPs.In order to ensure the drinking safety of rainwater,it is necessary to study the control technology of DBPs in disinfecting rainwater.This paper first simulated the experiment of the impact of atmospheric dry deposition on surface water to explore the effects of dry deposition on the characteristics of DOM and the generation of DBPs,and then studied the effects of different factors on formation of DBPs in rainwater when disinfected with UV/chlorine and UV/chloramine,and finally explored the impacts of the conventional treatment process of drinking water plants and the four pre-oxidation technologies on the formation of DBPs in rainwater.The main contents of the research included:(1)the characteristics of dry deposition DOM as DBP precursors and its DBP formation,(2)the characteristics of DBP formation in rainwater during UV/chlorine and UV/chloramine disinfection,(3)the removal of DBP precursors from rainwater by conventional drinking water treatment processes,(4)the effect of pre-oxidation on DBP formation in rainwater.The results of research on the characteristics of dry deposition DOM showed that the hydrophilic fraction(HPI)contributed the most DOM and low molecular weight DOM(<10 kDa)was the main component of HPI.In addition,aromatic proteins and soluble microbial products-like compounds were the dominant fluorescent species in DOM derived from dry deposition,and<10 kDa in transphilic(TPI)was the most abundant.The concentrations of DBPs generated by DOM from dry deposition were trihalomethanes(THMs)>haloacetic acids(HAAs)>haloaldehydes>haloacetamides>haloacetonitriles>halonitromethanes for both chlorination and chloramination.The main contributors of calculated toxicity are TPI and hydrophobic for chlorination and chloramination respectively.Therefore,Dry deposition PM was deduced to contribute DOM and DBP formation after chlorination in surface water,especially THMs and HAAs.These results presented herein provide key information for controlling DBPs in drinking water from the perspectives of atmospheric dry deposition,especially in the case of heavy air pollution.The experimental results of the formation characteristics of DBPs in rainwater showed that(1)there were fewer DBPs generated by UV/chloramine disinfection;moderate UV dose would reduce the formation of HAMs;Under alkaline conditions,the least HAMs are generated;(2)Except that HAMs were not affected by Br~-concentration during UV/chloramine disinfection,the formation amount of other DBPs gradually increased with the increase of Br~-concentration,and brominated DBPs were the main DBPs;(3)I~-concentration had almost no effect on the formation of THMs during UV/chlorine disinfection,but increased with the increase of I~-concentration during UV/chloramine disinfection.Coagulation-sedimentation had almost no effect on the control of DBPs in rainwater,and sand filtration(SF)and activated carbon filtration(GAC)could effectively control DBPs;Among all treatment processes,SF+GAC was most effective treatment process for removing DBP precursors from rainwater;Considering overall economics,GAC and chloramine disinfection treatment processes were very promising for controlling the comprehensive toxicity risk of DBPs in rainwater.Among four pre-oxidation techniques,pre-chloramine was most effective in reducing the overall toxicity of rainwater DBPs at higher doses of oxidant(2.0 mg/L),and UV/chloramine was most effective in reducing the overall toxicity of rainwater DBPs at lower doses(0.5 mg/L)and higher UV dose(720 mJ/cm~2).