The effect of biomass characteristics on the partitioning and sorption hysteresis of 17α-ethinylestradiol

A membrane bioreactor (MBR) and a conventional bioreactor (CBR) were operated under various conditions to manipulate the biomass characteristics and evaluate the ensuing effects on the partitioning and sorption hysteresis of 17 alpha-ethinylestradiol (EE2). When the biomass was grown without nitrogen limitation, the biomass mean particle size had a dramatic effect on the observed partitioning coefficient (K-d) and on sorption hysteresis index (HI). MBR K-d (0.33-0.57 L/g) values were equal to or larger than those of the CBR (0.25-0.33 L/g). Under nitrogen-deficient conditions, the correlations between the biomass particle size and K-d and HI were poor, likely because of extracellular polymeric substances. The K-d and HI were determined for initial EE2 concentrations between 100 and 1000 mu g/L. Changing the SRT did not manipulate particle size, and the effects on K-d and HI were not dramatic. This study also numerically explored the impacts of sorption hysteresis on the removal of pharmaceutical compounds. (c) 2007 Elsevier Ltd. All rights reserved.