Degradation Of Trace Steroid Estrogens In Aqueous Environment By Ultrasound And Its Coupling Process

Estrogens in aqueous environment including estrogen(E1),17?-estradiol(E2),17?-ethinyl estradiol(EE2)and estriol(E3),which disrupt the endocrine system of wildlife and humans and lead to irreversible effects even at trace concentration,attract more and more attention.In this study estrogens distribution in different treatment processes of a drinking water treatment plant are investigated.Ultrasound irradiation and ultrasound combined with KMnO4 are used to degrade these contaminants,the mechanism and removal effects are analyzed,based on which,the coupled way of combined technique with the conventional process of water purification is discussed.Investigation results showed that E1,E2,EE2 and E3 in source water,sediment effluent and filtering effluent varied in the range of 0.0?26.2,0.0?304.0,0.0?334.0 and 0.0?83.0 ng/L respectively.Among these estrogens,E2 and EE2 were more freqently detected with ratio of 69%and 65%.Estrogens concentrations of finished water was not detected maybe for the reason of chlorination of SEs.Ultrasound is ineffective in destruction of E2(initial concentration of 484?g/L)with removal ratio of 21.1%within 60 min contact under power of 270W and frequency of 20KHz.Comparably,KMnO4 can degrade SEs,efficiently when the initial concentration of E2 was 350 ?g/L and reaction time was 30 min,the degradation rate could reach 91.5%.However,KMnO4 oxidiation has defects of longer react time,and incompletely mineralization of SEs byproducts.Ultrasound irradiation was combined with KMnO4(Ultrasound/KMnO4)to enhance the degradation effect of E2,the removal ratio was 97.8%under the same condition of single process.Influencing research results showed that optimal pH conditions for Ultrasound/KMnO4 is strong acid;presence of electrolyte(NaCl)and anionic surfactant sodium dodecyl suldatecloud can promote degradation of E2 for both investigated processes;natural organic matter(NOM)accelerates the degradation of E2 for ultrasound,while to Ultrasound/KMnO4,the effect was first promotion and then inhibition.Tert-butyl alcohol also inhibited the removal of E2 for ultrasound and Ultrasound/KMnO4.E2 control effect by Activated carbon fibers(ACFs)and ultrasound irradiation are compared in this study.The adsorption test showed that ACFs can effectively and quickly adsorb E2 and the exothermic process fitted the model of Langmuir and Freundlich very well.Influencing facter analysis showed that increasing pH,humic acid and deoxidization conditions inhibited E2 adsorption.The maximum of E2 adsorbing capacity was 128 mg/g by ACFs.However,compared with ultrasound/KMnO4,AFCs just separate E2 from water to solid phase without degradation and need regeneration.Coupling experiments were put forward for the combining processes with conventional water treatment showed that best ultrasound/KMnO4 used simutenacelly with rapid stirring coagulation was the best copoule way.Under condition of KMnO4 dosage 4 mg/L,ultrasound irradiation 5 min and polyaluminium chloride 5 mg/L,E2 removal rate was maximum(99.8%).