Analysis of endocrine disrupting compounds in wastewater treatment plants: A perspective of trans-boundary waterborne pollution

Recent decades have brought an increasing concern of potential adverse human and ecological health effects resulting from Endocrine Disruptor Compounds (EDCs). In particular from new emerging compounds such as natural estrogens (e.g., 17β-estradiol, estrone), synthetic estrogens (e.g., 17α-ethynylestradiol), bisphenol A (BPA), nonylphenol ethoxylates (NPEOS), and nonylphenol (NP). These chemicals which are also known as organic wastewater contaminants are released directly to the environment after passing through wastewater treatment plants (WWTPs), which often are not designed to remove them from the effluent. The occurrence of the aforementioned compounds in surface water is becoming of increasing concern worldwide, and has led to a growing awareness that animals, and perhaps human health and function in ecosystems might become negatively impacted by continued release of these compounds into the environment at low levels (ng L-1). To determine the concentrations EDCs and the possible impact of WWTPs discharge, two different strategies were used. For the first approach, EDCs concentrations in wastewater were analyzed by Stir Bar Sorptive Extraction-Thermal Desorption-Mass Spectrometry. Simultaneously, the estrogenic activity was quantified by a chemiluminescent yeast assay which was developed to test water directly without concentration. EDCs concentration and estrogenic activity in the influent were lower in WWTPs in El Paso compared to the plants located in Mexico. Concentrations in effluent were 200% to 8000% higher in Mexico for the majority of the EDCs in study compared to the plants in El Paso. NP and NPEOS were the compounds with the higher concentration detected in influent ranging from non-detected to 8,144 ng L-1. BPA levels in effluent water were below 581.6 ng L-1 and for estrogen the levels were below 65.2 ng L-1. The removals of EDCs in WWTPs in El Paso were higher than 60% for the majority of the plants, and in Mexico lower than 60%. Estrogenic activity was removed 31% to 98% in WWTPs in El Paso. Insignificant removal of estrogenic activity was determined in plants from Mexico ranging from no removal to 86%. Based on our observation, the WWTPs with at least secondary treatment process were able to remove EDCs more effectively with an average of 85% for the EDCs analyzed in this study. In the second approach, a mass balance analysis was performed to determine the capability of two different treatment plants to remove EDCs from wastewater. Both plants were capable to eliminate up to 89 % of NP, NPEOS and estrogens. Denitrification treatment appeared to be inefficient for the removal of NP and ethoxylates from wastewater. Aerobic environment such as activated sludge treatment were responsible of degrading the majority of the compounds up to 90%. Advance tertiary treatment was more consistently efficient to remove EDCs from wastewater. The WWTPs in Mexico lacking activated sludge treatment performed the lowest removal efficiency of EDCs. It is essential that WWTPs in Mexico expand their facilities and upgrade their system to ensure that 100% of the wastewater can be treated by secondary treatment (activated sludge). The results from this study will undoubtedly serve as the initial framework upon which to expand and add more information in relation to EDCs or other contaminants in water resources along the border