Effects Of Household Treatment Methods On The Removal Of DBPs And Their Associated Toxicity

Household treatment methods are the last protective barrier before drinking water enters the human body.DBPs removal efficiency of household treatment is closely related to public health.Current studies on the removal of DBPs from drinking water by household treatments mainly focused on regulated C-DBPs(THMs and HAAs),with little attention on emerging DBPs(HALs,HANs,HNMs,HAcAms,and I-DBPs,etc.).At the same time,the available studies were mostly focused on chlorine disinfection,little on emerging disinfection methods.In addition,the studies of household treatment methods were mostly about the detection and mechanism discussion of DBPs,and rarely involved the biological toxicity tests.Based on the information above,this study aims to study the variation of DBPs concentration as well as the water quality during household treatment(filtration,boiling and filtration+boiling)using urban tap water,and then the DBPs removal efficiency was evaluated and the associated mechanism were elucidated.In order to further verify the experimental conclusions,the organic matter from pine tree leaves was used to simulate the natural organic matter in source water,and another disinfection experiment was carried out to test the DBPs removal efficiency of household treatment.Finally,the biological test was also performed to evaluate the toxicity change during disinfection and household treatment process.The results were as follows:1)The concentration of C-DBPs in tap water was greater than that of N-DBPs,and THMs and HAAs ranked the first.For the same type of DBPs,highly substituted DBPs(tri-DBPs and di-DBPs)and chlorine-containing DBPs were the principal forms existed in disinfected water.The results of simulated disinfection were consistent with those of urban tap water.Compared with chlorination,chloramination could effectively reduce the production of THMs,HAAs,HALs,HANs and HNMs,and the reduction of THMs and HAAs were most significant.However,chloramination increased the formation of di-HALs,HAcAms and I-DBPs.2)The activated carbon could effectively remove residual disinfectants,some organic substances and halogen ions in tap water.Among the tested C-DBPs,activated carbon had the best effect on the removal of THMs.For N-DBPs,activated carbon had the worst adsorption effect on HAcAms.Because THMs had the largest LogP value(the larger the LogP value,the stronger the hydrophobicity of the compound,and the more easily it be absorbed by activated carbon)and the strongest hydrophobicity in C-DBPs,which was easily removed by activated carbon.Among N-DBPs,HAcAms had the smallest LogP value and the weakest hydrophobicity,which was difficulty removed by activated carbon.3)Boiling could remove the residual chlorine/chloramine and some organic compounds in the disinfection water.After boiling,the halogen concentration and pH value would increase slightly.Boiling experiments showed that the removal of DBPs was not subject to the disinfection mode,but only related to the properties of the compound itself.The boiling process was efficient for removing the unstable and volatile DBPs(THMs,HANs,HNMs,HALs and HAcAms),but not for the stable and non-volatile DBPs(e.g.HAAs).The concentration of some HAA species(e.g.DCAA)even increased during boiling process.Among the same type of DBPs,the species with high degree of substitution was generally easier to be removed than those with low degree of substitution.In addition,the removal efficiency for DBPs with iodine/bromine(especially with iodine)was preferable to those with chlorine only during boling process.4)Household treatment could effectively remove DBPs from drinking water and optimized water quality.Compared with single process treatment,the combined effect of filtration and boiling was the most significant for the removal of DBPs,and therefore it's a method worth recommending to the public.In the boiling experiment,the removal of DBPs was not affected by heating containers with different materials,but the removal rate was affected by other operational factors such as heating water volume and cooling method.Experiments revealed that small water volume and uncapped heating could facilitate the removal of DBPs during boiling,and uncovered natural cooling could further enhance the removal effect.5)Biological experiments showed that disinfected water had acute toxicity to Artemia,and the toxicity was more noticeable with the increasing concentration of organic matter.Under the influence of the poison in the disinfectant water,the oxidation-antioxidant balance state of the Artemia was destroyed,so that the SOD activity was activated to remove the excessive ROS due to external stimuli.However,the degree of oxidation in the body exceeds the scavenging ability of antioxidants,so that cells were severely damaged by oxidation and produced a large amount of MDA.In the experimental group,compared to chlorinated water and deciduous water,chloraminated water was the most toxic and caused the most serious oxidative damage to Artemia.Furthermore,the poison of disinfected water significantly interfered the activity of ACP,AKP,GOT and GPT enzymes in the body,suggesting the immune regulation,digestion and proteins metabolism were disturbed,and finally affected the normal physiological functions of Artemia.The boiling process could effectively reduce the toxicity of disinfected water,decrease the oxidative damage and the interference of normal physiological functions(immunomodulation,digestion and metabolism,protein metabolism level,etc.),so that the physiological and biochemical indicators(SOD,MDA,ACP,AKP,GOT and GPT)in the body tend to be normal.Therefore,boiling treatment for disinfected water may be an effective and inexpensive “detoxification” method.