Degradation and adsorption to activated sludge of Bisphenol-A, 17-β-Estradiole and 17-α-Ethinylestradiole

摘要

Several substances which have estrogenic effects on aquatic organisms were observed at relevant concentrations in the effluent of wastewater treatment plants. In order to evaluate and optimise the efficiency of wastewater treatment plants a basic knowledge of the behaviour of these substances during the different steps of wastewater treatment has to be derived. Investigations on degradation and adsorption behaviour of Bisphenol-A (BPA), 17-β-Estradiole (E_2) and 17-α-Ethinylestradiole (EE_2) were conducted. Adsorption experiments were performed with activated and inactivated sludge. The sludge was taken from a low loaded wastewater treatment plant. The results showed no significant difference between activated and inactivated sludge during the first 24 hours. The sludge showed a high adsorption potential with up to several mg Bisphenol-A per g total suspended solids (TSS) as well as for E_2 and EE_2. Due to this it can be assumed that adsorption processes to the sludge are dominating the removal of these substances from the liquid phase. The adsorption behaviour was described with the Freundlich kinetic. Adsorption was also shown to be dependent on the pH. Desorption processes were observed at pH values higher than 10. Degradation tests under stabilizing conditions have been performed whereby different increasing concentrations of the investigated substances were added. The selected substances were solved in effluent of a wastewater treatment plant and different carbon sources were added as substrates to the degradation test in order to discover a possible relation between the elimination and different substrates. Considering the starting concentration elimination rates could be calculated and a sigmoidal gradient was obtained.