Isolation,Identification And Formation Mechanisms Of Estrogenic Disinfection By-products Of Diethylstilbestrol

Environmental estrogens(EEs)have become a risk for both ecosystem and human health in recent decades.The effluents from municipal sewage treatment plants are the main source of environmental estrogens.Some studies have shown that estrogens can be removed efficiently by disinfection processes,but some of the disinfection by-products(DBPs)still retain estrogenic activity,causing potential safety threats to the storage and reuse of reclaimed water.This study focused on the estrogenicity removal of diethylstilbestrol(DES)and formation mechanisms of DES DBPs under different disinfection processes.Estrogenic DES DBPs were separated and identified by affinity chromatography and their estrogenicities were evaluated.The ecological storage process was simulated by solar light irradiation with DES or DES DBP samples and a pilot device of combined disinfection processes was designed and established for further research.This study provided a theoretical guidance and technical support for the treatment selection and water safety of reclaimed water treatment plants.Firstly,the estrogenicity removal of DES under chlorine,ozone or ultraviolet(UV)disinfection processes was studied.Under 10 mins' disinfection,the estrogenicity removal efficiencies of DES were all above 90%,while low removal efficiencies were observed in DES samples synthesized with secondary water containing much DOC.Afterwards,5 estrogenic DBPs of chlorine,1 of ozonation and 3 of UV irradiation were isolated by affinity chromatography,and Z,Z-dienestrol from ozonation,9,10-diethylphenanthrene-3,6-diol,cis-DES and also Z,Z-dienestrol from UV irradiation were identified.Among them,9,10-diethylphenanthrene-3,6-diol was proved to have stronger estrogenic activity compared to E2 as its relative binding affinity with estrogen receptor ?(ER?)was 0.61 ± 0.06 compared with DES,which was found to be an estrogenic DES DBP for the first time,but it can be further photodegraded.Besides,solar light irradiation with DES or DES DBP samples was conducted.DES was demonstrated as a photochromic compound,whose UV induced intermediates can be transformed back to DES under sunlight.Therefore,more attention should be paid to on DES and DES DBPs during the ecological storage process of reclaimed water.Based on the research above,it was assumed that the control of estrogenic DBPs would be more effective under combined disinfection process.Hence,a pilot device of combined disinfection techniques with chlorine,ozone,UV and chlorine dioxide processes was designed and established,which has significant importance for studies on unknown estrogenic substance removal in secondary water under different disinfection processes.