Joint Photolysis And Biodegradation Of 17?-ethynylestradiol Mediated By Reduced Humic Acid

In recent years,there has been growing concern over the potential risk posed by natural and synthetic chemicals that can produce adverse effects on human and wildlife by interacting with the endocrine system,which containing the synthetic chemical of 17?-ethynylestradiol(EE2).Though the conventional municipal wastewater treatment methods,typically based on biological processes,are capable of removing some ordinary substances,whereas non-biodegradable compounds such as endocrine disrupting chemicals may escape the treatment and be released into the invorenment.Dissolved organic matter(DOM)widely present in the aquatic environment and play an important role in the transformation of many pollutants.There are many studies about the effect of DOM on the removal of EE2 by biodegradation and photodegradation.But the effect of DOM on the transformation of EE2 in the joint photolysis and biodegradation processes has barely studied.Therefore,we investigate EE2 photodegradation mediated by DOM in the presence of microorganisms under anaerobic condition.The key conclusions can be listed as follows:(1)EE2 could be removed by Shewanella putrefaciens under anaerobic condition and the removal efficiency of EE2 was 8.94%.The biodegradation of EE2 was greatly promoted with the present of HA and the removal efficiency of EE2 increased to 30.1%in 72 h.This phenomenon indicated that HA could act as electron acceptor in the process of EE2 biodegradation probably.The electron donated capacity was decrease of HA after photo modification.And the role of HA in the biodegradation process decrease at the same time.(2)The roles of HA in the photodegradation processes of EE2 varied with different conditions,including the concentration of HA and pH of solutions.On the one hand,a red shift of EE2 adsorption spectra occurred with the increasing of pH.On the other hand,HA was found to be a heterogeneous mixture and a weak acidic polyelectrolyte,which might be ionized when pH exceeded 5.0,and absorbed more incident light and produced more reactive species.Because of the increased of UV-vis absorption,fluorescence intensity,humification degree and the ability of combine with EE2 of HA,the photodegradation of EE2 was greatly promoted with the present of bio-modified HA.(3)The removal of EE2 was studied in a photolysis process containing bacteria,and EE2 degradation rate was promoted greatly when bacteria were added.The degradation efficiency varied with pH changes and HA concentration.Namely,neutral pH and 10.0 mgC?L~-11 HA were beneficial to the EE2 degradation.The EE2 loss through biodegradation could be neglected in 6 h.The roles of RHA were compared with PHA in the respects of contribution rate and amount of reactive substances.And RHA had superior photochemical properties than PHA.The estrogenic activities of solutions were reduced after joint degradation.