Comparison of Trace Organics and Estrogenic Activity Removal in Integrated Fixed Film Activated Sludge and Conventional Wastewater Treatment

A pilot integrated fixed film activated sludge (IFAS) system and a parallel non-IFAS control were operated to compare their removal efficiencies of trace organic chemicals, including endocrine disrupting chemicals (EDCs) and estrogenic activity as determined by the yeast estrogen screen (YES) assay. Measurements of concentration profiles of EDCs in the systems showed that the IFAS train outperformed the control with respect to EDC removal. Differences in EDC removal rates among the four biomass phases present (Control suspended, IFAS suspended, and IFAS attached phases in two sequential aerobic reactors) were determined in laboratory batch tests. Comparison of EDC and ammonia removal rates showed that there were no significant relationship between these two parameters, which suggests that EDC removal is not directly related to nitrification rates (ammonia consumption) at least in the range of EDC concentrations commonly encountered in wastewater treatment plants (WWTPs). Evidence for sorption as a major removal mechanism was evaluated by comparing measured removal efficiencies and octanol-water partition coefficient (K_ow) of individual compounds measured by GC/MS, which showed that higher hydrophobicity did not lead to enhanced removal suggesting that biodegradation, rather than sorption, controls EDC removal in WWTPs. The results suggest that IFAS systems may be beneficial for increasing removal rates of estrogenic activity and at least some trace organics, and there is evidence for removal by heterotrophic biodegradation, rather than by sorption or removal by nitrifiers.