Obtaining process mass balances of pharmaceuticals and triclosan to determine their fate during wastewater treatment

To better understand pharmaceutical fate during wastewater treatment, analysis in both aqueous and particulate phases is needed. Reported herein is a multi-residue method for the determination of ten pharmaceutical drugs and the personal care product triclosan in wastewater matrices. Method quantitation limits ranged from 7.6 to 76.6 ng l− 1 for aqueous phases and from 7.0 to 96.7 ng g− 1 for particulate phases. The analytical method was applied to attain a complete process mass balance of a pilot-scale activated sludge plant (ASP) operated under controlled conditions. The mass balance (inclusive of aqueous and particulate concentrations at all sample points) was used to diagnose removal, revealing pharmaceuticals to be separable into three fate pathways: (a) biological degradation, (b) sorption onto activated sludge and (c) resistant to removal from the aqueous phase. These differences in fate behaviour explained a broad range of secondary removal observed (− 8 to 99%). The ASP was also simultaneously compared to a full-scale trickling filter (TF) works whilst receiving the same influent wastewater. Performance of the ASP and TF was similar, achieving total pharmaceutical removals of 253 and 249 μg g− 1 biochemical oxygen demand (BOD) removed, respectively. This corresponded with reductions in total pharmaceutical load of 91 and 90% (ANOVA, p-value > 0.05). Interestingly, despite low suspended solid concentrations final effluents of both the ASP and TF contained significant concentrations of some chemicals in the particulate phase. Individually, triclosan and the antibiotics ofloxacin and ciprofloxacin were within the particulate phase of effluents at concentrations ranging from 26 to 296 ng l− 1.