Assessing pharmaceutical removal and reduction in toxicity provided by advanced wastewater treatment systems

Wastewater treatment plants (WWTPs) have been considered as hotspots for pharmaceutical residues, such as antidepressants, antimicrobials and active ingredients of over-the-counter drugs. Despite evidence of ecotoxicological effects of these microcontaminants on exposed fish in the aquatic systems, there is currently no regulation in terms of the levels of pharmaceutical residues allowable for release into the environment. Depending on the extent of treatment employed in WWTPs removal of pharmaceutical residues are highly variable. This study compares the removal efficiencies for several antimicrobials, antidepressants, and other pharmaceuticals at different stages of the wastewater treatment process of seven WWTPs that employ varying treatment technologies including biological, physical, advanced chemical oxidation, and a combination of two or more of these technologies. The concentrations of the pharmaceuticals were measured by liquid chromatography/mass spectrometry at multiple points during the course of treatment. Additionally, the ecotoxicological effects of the WWTP effluents were also evaluated based on the behavioral effects in larval zebrafish. It was found that biological treatment process provided negative to low removal (<50%), while activated carbon and ozonation provided high removal (>95% overall removal) for 14 out of 15, and 9 out of 11 compounds detected in WWTP influents, respectively. Notably, the final effluents of the seven WWTPs in this study did not show any significant behavioral alterations in zebrafish, indicating that despite differences in removal efficiencies all the treatment processes investigated are sufficient in preventing short-term biological effects.