LAUSR

Abstract Photolysis is one of the main pathways for 17α-ethinylestradiol (EE2) removal in natural systems. Organic matter in the effluent from biological wastewater treatment facilities contains abundant photosensitive substances, which could play an important role in the photodegradation of micropollutants such as ethinylestradiol. In order to explore the source of such photosensitive substances, extracellular and intracellular polymeric substances from aerobic and anaerobic bacterial cultures were tested for their ability to photodegrade EE2 under anaerobic conditions. Degradation was promoted at higher concentrations of the extracts, except for the extracellular polymers from anaerobic cultivation. The contribution of triplet state substances was more important than that of singlet oxygen or hydroxyl radical. The contributions of various triplet state substances were strongly correlated with their quantum yield coefficients. The fluorescence intensity values of the proteins and amino acids were in line with the observed photodegradation rates mediated by the four cellular polymers. Proteins or amino acids may play an important role in the production of triplet state substances. This study has suggested the sources of photosensitive substances in effluent organic matter and could further explain the fate of estrogens in natural photodegradation.