Monitoring occurrence and removal of selected pharmaceuticals in two different wastewater treatment plants

The occurrence of pharmaceuticals in the environment is a concern due to its potential adverse effect on human health and ecology. In this research study, the occurrence of three selected pharmaceuticals-erythromycin (ERY), sulfamethoxazole (SMZ), trimethoprim (TMP), and an antimicrobial/antifungal agent triclosan (TRL) was monitored at two Southern California wastewater treatment plants (WWTPs). Between April and October of 2017, 77 composite samples were analyzed. Results from the study revealed the presence of all four pharmaceuticals in the influent at both WWTPs. Of the four pharmaceuticals, SMZ had the highest concentration (WWTP1, 1860 ng L-1, and WWTP2, 2146 ng L-1). In WWTP1, the concentrations of ERY, TRL, and TMP ranged from 33 to 278 ng L-1, 146 to 410 ng L-1, and 410 to 1021 ng L-1, respectively, while in WWTP2, their concentrations ranged from 16.7 to 209 ng L-1, 0 to 160 ng L-1, and 407 to 672 ng L-1, respectively. Even though both plants employed secondary biological treatment protocols, their removal efficiencies are remarkably different. WWTP1 is relatively more effective in the removal of ERY, TRL, and TMP with a removal efficiency of 46%, 63%, and 61%, respectively, while at WWTP2 only 4% TMP was removed, and no removal of ERY and TRL was observed. Both plants were unable to remove SMZ. Pharmaceuticals are bioactive compounds, and as such, even at low concentration levels, they may adversely affect the environment and will require additional treatment to ensure that treated wastewater meets the specific water quality criteria for reuse.