Occurrence and Fate of Endocrine Disruptors through the San Marcos Wastewater Treatment Plant

Wastewater treatment plants (WWTPs) have been shown to be major point sources of endocrine disruptor compounds (EDCs) to the environment because they are not completely removed by traditional treatment processes. This study investigated the removal efficiencies of 23 known or suspected EDCs through the San Marcos WWTP to determine which treatment process was the most effective at removal. Of the 23 compounds monitored, the most frequently detected in the WWTP influent in part per billion concentrations were acetaminophen, nonylphenol, coprostanol, caffeine, benzophenone, triethyl citrate, DEET, bisphenol A, tris(2-chloroethyl)phosphate (TCEP), and triclosan. Comparison of influent and effluent concentrations showed that the San Marcos WWTP is effectively removing (>92%) of these compounds, with the exception of carbamazepine and TCEP. Within the WWTP, results indicate that the aeration process (biological treatment) was the most effective at removal. When compounds were not completely removed from the wastewater, they were detected in waters downstream of the effluent discharge in part per trillion concentrations in the San Marcos River. This study also investigated the occurrence of these compounds in wastewaters from the San Marcos Hospital and the finished water of the San Marcos water treatment facility (WTF). Results from samples collected at the hospital indicate that the hospital discharge is contributing to the concentration of these compounds in the San Marcos wastewater collection system (0.05 - 140 ug/L concentrations). Analyses of samples collected from the WTF indicate that there is no significant amount of these compounds in the finished drinking water supply. TCEP was only detected once at trace amounts (< 0.03 ug/L).