17-Estradiol Removal by Electrochemical Technology in the Presence of Electrochemically Active Bacteria in Aerobic Aquatic Environments

17-Estradiol (E2) is normally detected in water at nanogram per liter levels, which could alter normal hormone functions and the physiological status of wildlife. In this study, biodegradation of E2 with microorganisms from activated sludge showed a high removal efficiency of 99.2% in 60h. This was greater than the efficiency using single Escherichia coli. To remove E2 effectively, a system combining electrochemical and biological degradation was used to remove E2 from an aqueous solution. E2 removal efficiency using the combined system was increased at high dissolved oxygen concentrations and low pH and could reach 99.3% after 90min. An electric current density of 20mA/cm(2) inhibited the growth of most bacterial species; however, dominant bacterial strains such as Bacillus, Lysinibacillus, and Aeromonas survived, leading to promotion of E2 degradation. From analysis of E2 degradation products by gas chromatography-mass spectrometry, E2 degradation was explained by the following process. First, E2 was oxidized to form hydroxylation products. Then, ring-opening oxidization of the products formed macromolecules and small-molecular-weight organic carboxylic acids. Finally, organic carboxylic acids were mineralized. It was also demonstrated that E2 degraded more quickly and completely by the combined system than by biological degradation.