Study On The Removal Of Parabens In Urban Sewage Treatment System

P-hydroxy benzoic acid esters(parabens)are typical compounds with the similar activity of Endocrine Disrupters,they are widely used in food,pharmaceuticals and personal care products as a kind of preservative with excellent performance.Due to the expended applications and fields,the frequency of contact and expose to them are increased for human.Animal experiments proved that parabens had the estrogen activity,and they may affect the development of human reproductive system.At present,parabens are widely detected in organisms and the environment matrix.Urban sewage treatment plant is an important sink and pollution source of receiving water,however,related studies are scarce.Therefore,it is imperative to carry out the study on the fate of parabens in urban sewage treatment system.In this study,the solid phase extraction method and HPLC-MS/MS were developed to analyze 6 parabens and 4 metabolites in wastewater and sludge.Then,wastewater and sludge samples in two wastewater treatment plants(WWTPs)with different treatment processes were analyzed.Finally,the residue characterisitics and removal pathway of parabens were deeply studied.In sewage samples,EtP was found in all samples,and the detection rate of MeP and PrP were 97%.MeP,EtP and PrP were the most abundant parabens.The concentrations of parabens in influent of the A/O treatment process were lower than those of the hydrolyzed acid and CAST process caused by the different wastewater input,while the concentrations of parabens in effluent of the A/O treatment process werehigher than those in the hydrolyzed acid and CAST process.Both the A/O treatment process and the hydrolyzed acid and CAST process have a good removal effect on parabens.The removal rates of parabens in the A/O treatment process and the hydrolyzed acid and CAST process were 56.83%~99.97% and 97.72%~100%,respectively.A/O tank and secondary sedimentation tank played a major role in the A/O process,whereas hydrolysis acidification tank,CAST tank and UV disinfection had the similar removal rate for the hydrolyzed acid and CAST process.Seasonal variation had different influences on the residues and removal rates of parabens.There was no significant difference of removal rates in the two wastewater treatment processes in different seasons.However,the concentrations and composition distributions of parabens in A/O tank and CAST tank showed significant seasonal variation.The detection rates of parabens and metabolites in sludge samples were 100%.Among metabolites,the concentration of 4-HB was the highest,followed by 3,4-DHB,OH-MeP and OH-EtP.The sum concentrations of 4-HB,3,4-DHB,OH-MeP and OHEtP in influent,effluent and sludge were 35238.21 ng/L,33.59 ng/L and 146.24 ng/g,respectively.Totally,5.07 kg and 16.82 kg parent parabens and 24.35 kg and 16.01 kg parabens metabolites were discharged into environment every year through effluent and sludge.The main removal pathways of parabens in wastewater treatment process were adsorption to sludge,degradation or loss in the whole process,and discharged with effluent.Generally,the removal of metabolites in the A/O treatment process is better than parent parabens.The degradation and loss was the main removal pathway of parabens in WWTPs.BuP and OH-MeP were degraded and lost by 48.8% and 43.41%,while other compounds were degraded and lost higher than 70%.Parabens were removed in urban sewage treatment plant easily,and the removal of metabolites of parabens were more easilier than parent parabens.