Investigation of sorption behavior between pyrene and colloidal organic carbon from activated sludge processes

The sorption behavior of pyrene for different size fractions of colloidal organic carbon (COC) originating from two biological wastewater treatment facilities (a full-scale activated sludge system (FSAS) and a membrane bioreactor (MBR)) was investigated by fluorescence quenching. Fluorescence lifetime measurements demonstrated a dynamic quenching component in all samples, including the colloidal-free filtrates. COC sorption coefficients (K-coc) for pyrene ranged from < 1 x 10(3) L/kg(coc), to 80 x 10(3) L/kg(coc) and were comparable to values obtained in the literature for natural organic matter. Both linear and nonlinear behaviors were observed in the Freundlich-described converted isotherms (n = 0.89-2.1). The aromatic content of COC was quantified by the molar extinction coefficient at 280 nm (e(280)). Good correlations were observed between COC-pyrene sorption coefficients and e(280) coefficients, suggesting that e(280) may be a useful tool for predicting colloidal transport of hydrophobic organic compounds (HOCs) from activated sludge systems. The removal of COC from treated effluents may appreciably reduce the concentrations of HOCs discharged to receiving streams.