Sorption of 17beta-estradiol and 17alpha-ethinylestradiol by colloidal organic carbon derived from biological wastewater treatment systems.

Sorption coefficients (K(COC)) between 17beta-estradiol (E2), 17alpha-ethinylestradiol (EE2) and size-fractionated colloidal organic carbon (COC) derived from two biological wastewater treatment facilities were quantified by fluorescence quenching. The two wastewater treatment systems included a full-scale activated sludge system (FSAS) and a membrane bioreactor (MBR). The K(COC) coefficients were highly variable and ranged between (<1 to 179) x 10(3) L/kgCOC for E2 and (<1 to 430) x 10(3) L/kgCOC for EE2 and were higher than expected from the analytes octanol-water partition coefficient. Correlations between the molar extinction coefficients measured at 280 nm (e280) and K(COC) coefficients were weak but stronger for E2 compared to EE2. Attempts at correlating sorption behavior with colloidal protein and polysaccharide concentrations were only marginally successful (r2 approximately 0.4). These low correlations suggest that aromatic content, protein, or polysaccharide concentration can not adequately explain E2 and EE2 sorption behavior to COC and that other fractions of the organic matter pool play an important role in binding. A substantial portion of the aqueous E2 and EE2 concentrations (up to 60%) may be associated with colloidal material, suggesting that COC may play a role in the fate and transport of E2 and EE2 during the activated sludge process.