Identification And Formation Of Halobenzoquinones Disinfection By-products

Halobenzoquinones?HBQs?are a new class of disinfection by-products?DBPs?that have received increasing attention in recent years.Although HBQs are only at ng/L levels in drinking water,quantitative structure-toxicity relationship and toxicological studies have shown that HBQs are more toxic than regulated DBPs.Environmental exposure studies have also shown that HBQs are present in drinking water and swimming pool water.Therefore,this study would explore the formation of HBQs in water plants,tap water and swimming pools based on the establishment of an efficient and sensitive method for determining HBQs.The study would provide the evidences for HBQs control,and quality standards establishment of drinking water and swimming pool water.Part?Establishment of method for determining halobenzoquinones disinfection by-productsObjectives:The objective of this study is to establish an efficient and sensitive method for the detection of HBQs,and to provide technical support for the future investigation of HBQs pollution in drinking water and swimming pool.Methods:The solid phase extraction?SPE?method was used to extract HBQs from water samples.The extracts were analyzed using ultra performance liquid chromatography-tandem mass spectrometry?UPLC-MS/MS?for seven HBQs?2,5-DCBQ,2,6-DCBQ,2,5-DBBQ,2,6-DBBQ,DCMBQ,TetraBBQ,and TetraC-1,2-BQ?.Results:The results of SPE-UPLC-MS/MS showed that the retention time of seven HBQs was between 10.19±0.01¹6.76±0.01 minutes.The total analysis time was about 16.76 minutes.Except for 2,5-DCBQ,the calibration curve R² of the other six HBQs was greater than 0.9990.Methods detection limit of seven HBQs was between 0.26¹.76 ng/L.The recoveries were between 62.5%¹02.9%,and the relative standard deviations were less than 5%.Conclusions:The method of SPE-UPLC-MS/MS could separate seven HBQs completely.As a result of this method is stable,high sensitivity,high accurate and simple to operate,is an ideal method for determination of HBQs in water in laboratory.Part ? Determination and formation of halobenzoquinones disinfection by-products in drinking waterObjectives:The aim of this study is to detect the levels of HBQs in drinking water and explore the formation of HBQs in water plants and tap water.Methods:Source water,finished water,and tap water were collected from six water plants in September 2017,December 2017 and March 2018,respectively.Seven HBQs levels were determined by SPE-UPLC-MS/MS.And the levels of residual chlorine,COD,humic acid,calcium ion,chloride ion,bromide ion,ammonia nitrogen,UV₂₅₄,pH and temperature of the water samples were determined.The effect of tap water processing technology,season,delivery distance and water quality indicators on the formation of HBQs in drinking water was analyzed.Results:?1?Three HBQs?2,6-DCBQ,2,6-DBBQ and TetraC-1,2-BQ?were identified in finished water.The total HBQs?THBQs?concentration was1.85²0.28 ng/L.And 2,6-DCBQ occurred in the water samples at the highest concentration and detection rate.?2?The chloride ion level of source water in December was higher than September and March?P<0.05?.The bromide ion level of source water in September was higher than December and March?P<0.05?.The levels of humic acid of source water were higher in December and March than in September?P<0.05?.There was no significant difference in THBQs level between seasons?P>0.05?.?3?The finished water showed significantly higher levels of THBQs,residual chlorine,chloride ions,and bromide ions than the source water?P<0.05?,and the levels of humic acid,COD,UV₂₅₄,and pH were significantly lower than the source water?P<0.05?.There was no significant difference in the levels of calcium ion,ammonia nitrogen and temperature between the treatment process points?P>0.05?.In addition,the plant which using liquid chlorine disinfection or sodium hypochlorite disinfection showed significantly higher levels of THBQs of finished water than chlorine dioxide disinfection.?4?The result of correlation analysis shows that the relationship of chloride ion of finished water,residual chlorine of finished water and HBQs formation were positive correlation?P<0.05?.The results of multiple linear regression analysis showed that the relationship of residual chlorine of finished water and HBQs formation were positive correlation?P<0.05?.?5?Three HBQs?2,6-DCBQ,2,6-DBBQ and TetraC-1,2-BQ?were identified in tap water,with a total concentration of 1.8¹1.3 ng/L.And2,6-DCBQ occurred in the water samples at the highest concentration and detection rate.?6?In tap water,the chloride ion levels of in December and March were higher than September?P<0.05?.The calcium levels in December and March were lower than September?P<0.05?.The residual chlorine level of tap water in December was higher than September and March?P<0.05?.There was a trend of UV₂₅₄54 levels in decreasing order:December>March>September?P<0.05?.The pH value was as follows:September>March>December?P<0.05?.The water temperature values ranked as September>December>March?P<0.05?.There was no significant difference in levels of HBQs,humic acid,ammonia nitrogen,and COD between seasons?P>0.05?.?7?The results of multiple linear regression showed that the THBQs levels have positive correlation with residual chlorine in tap water?P<0.05?and negative correlation with calcium ion level?P<0.05?.There was no correlation between THBQs formation and chloride ion,bromide ion,humic acid,ammonia nitrogen,COD,UV254,pH,and temperature levels?P>0.05?.?8?The THBQs and residual chlorine levels showed a downward trend with the increase of the transmission distance of the pipeline network,and there was no significant change in other water quality indexes.Conclusions:?1?In drinking water,2,6-DCBQ,2,6-DBBQ and TetraC-1,2-BQ HBQs were detected,with the ng/L levels,and 2,6-DCBQ was the most common HBQs.?2?High residual chlorine levels is helpful to the HBQs formation in finished water.High residual chlorine and low calcium ion levels are helpful to the HBQs formation in tap water.?3?As the transmission distance of the pipe network increases,the levels of drinking water HBQs decrease.Part ? Determination and formation of halobenzoquinones disinfection by-products in swimming pool watersObjectives:The purpose of this study is to detect the levels of HBQs and explore the formation of HBQs in swimming pool waters.Methods:From August to December in 2017,water samples,including the middle of swimming pools?30cm below the middle of the swimming pool surface?,the edge of swimming pools?1m from the swimming pool wall and30cm below the water surface?and source water,were collected from seven swimming pools in China.The levels of HBQs,residual chlorine,COD,humic acid,calcium ions,chloride ions,bromide ions,ammonia nitrogen,UV₂₅₄,pH,and temperature were measured.Results:?1?The water quality of swimming pools fluctuated widely,and the water qualities of different pools were significantly different.Three HBQs were found in swimming pools and their source water,including 2,6-DCBQ,2,6-DBBQ,and TetraC-1,2-BQ.Swimming pools water had a THBQs concentration of4.6⁴5.3 ng/L,while source water had a total HBQs concentration of<0.26¹3.7 ng/L,with the highest detection concentration and detection rate of2,6-DCBQ.?2?Swimming pools water showed significantly higher levels of HBQs,chloride ion,residual chlorine,humic acid,ammonia nitrogen,COD,UV254and temperature than their source water?P<0.05?.But there was no significant difference in bromide ion,calcium ion and pH between swimming pools water and their source water?P>0.05?.?3?The correlation analysis between water quality and total HBQs concentrations showed that THBQs levels have positive correlation with chloride ion,humic acid,COD,and UV₂₅₄?P<0.05?and negative correlation with calcium ion and pH?P<0.05?.There were no correlation between THBQs and other water quality indicators?P>0.05?.The results of multiple linear regression analysis showed that THBQs levels have positive correlation with chloride ion and humic acid concentration?P<0.05?and negative correlation with calcium ion concentration?P<0.05?.Conclusions:?1?Three HBQs?2,6-DCBQ,2,6-DBBQ,and TetraC-1,2-BQ?were found in swimming pool water,with the highest concentration and detection rate of2,6-DCBQ.The concentrations of 2,6-DCBQ and THBQs in swimming pool water were higher than that of the tap water.?2?High chloride ion level,high humic acid level and low calcium ion level were favorable to the HBQs formation in swimming pool waters.