The effect of biomass characteristics on the partitioning and sorption hysteresis of 17alpha-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 17alpha-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) (0.33-0.57L/g) values were equal to or larger than those of the CBR (0.25-0.33L/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 1000microg/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.