Effect Of Residual Chlorine On Migration Of Phthalate Esters In The Plastic Water Supply Pipes

Phthalate esters(PAEs)are the most commonly used plasticizers in the world.It has been proved that PAEs has been detected in many environmental medias and organisms.In addition,plastic pipe is widely used in water supply and drainage engineering because of its excellent performance.PAEs are often used to improve the properties of plastic pipes.PAEs are free in pipes,so they are easy to leach into tap water in contact with plastic pipes.This study investigated the existence of PAEs in the water of the typical process effluent and three users with different distribution distance in distribution system of a water plant in Tianjin,and evaluated the health risk of PAEs in the water of three users exposed to people by oral intake.The results show that the removal efficiency of PAEs of this water plant is 51.4%.However,due to the use of plastic water supply pipes in the distribution network,PAEs in tap water is greatly increased during the distribution system.However,health risk assessment showed that PAEs in tap water of three users exposed to people by oral intake were low.In addition,the change of PAEs concentration in the water samples was investigated in the new and artificial device made of unplasticized polyvinyl chloride(UPVC)and plyprpylene(PPR)pipes for 7 days.The results show that,for pipes of the same material,the artificial wear makes the total release of PAEs increased,among which di-n-butyl phthalate(DBP)release is increased obviously,and the release rate of PAEs by artificial wear pipeline is higher than that of the new pipe;for pipes of the different materials,the release of PAEs in PPR pipes is smaller than that in UPVC pipes,which may be due to that the PPR pipes have better measures to fix PAEs plasticizers during the process of production.Therefore,for PAEs pollution,PPR pipeline is safer than UPVC pipeline.In all pipeline experiments,when the amount of residual chlorine is 0,total PAEs concentration is the highest of the three residual chlorine conditions set in this experiment.When adding residual chlorine,the residual chlorine may have electrophilic substitution reaction with PAEs in water,resulting in the decrease of PAEs concentration in water.The higher the amount of residual chlorine is,the lower the final equilibrium concentration of PAEs will be.In general,this paper takes a waterworks and its distribution network in Tianjin as an example to evaluate the content level of PAEs in local tap water and the health risk of exposure through oral intake.In addition,this paper explores the influence of residual chlorine on the concentration level of PAEs in the water in the pipe network when it is retained in plastic pipes,and preliminarily speculates the reaction characteristics of residual chlorine and PAEs.Also,the effect of artificial wear on the release of PAEs from plastic water supply pipes of different materials was explored,which provided a new focus for the safety control of tap water quality.