Comparative endocrine disrupting compound removal from real wastewater by UV/Cl and UV/H2O2: Effect of pH, estrogenic activity, transformation products and toxicity

Abstract

Extensive use of endocrine disruptor compounds (EDCs) and their release through various pathways into the environment are emerging environmental concerns. In this context, H₂O₂ and chlorine UV-based treatments were carried out to evaluate their efficiency in the removal of the bisphenol A (BPA), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) at 100 μg L^-1 from ultrapure water and from wastewater treatment plants (WWTP). Photolysis was performed under different irradiation sources, i.e. UVC and UVA. The effect of H₂O₂ (3 and 30 mg·L^-1), free chlorine concentrations (1 and 2 mg·L^-1) and pH (5, 7 and 9) were also investigated. Toxicity (Raphidocelis subcapitata) and estrogenic activity (yeast estrogen screen - YES assay) were assessed during the processes. Compound removal at optimal operating parameters reached 100% after 15 and 2 min for UVC/H₂O₂ (pH 9 and 3 mg L^-1 of H₂O₂), and UVC/Cl (pH 9 and 2 mg L^-1 of chlorine), respectively. Total organic carbon (TOC) removal achieved 37% and 45% for the H₂O₂ and Cl-UV based process, respectively. The in vitro YES assay indicated that the formed by-products were non-estrogenic compounds, while the toxicity evaluation revealed high cell growth inhibition due to UVC/Cl byproducts. During the UV-based processes, 30 transformation products (TPs) were identified, in which three new chlorinated TPs from E2 and EE2 may be responsible for toxicity effects. EDC degradation by UV/Cl is faster than by UV/H₂O₂, although chlorinated toxic byproducts were also formed during the UV/Cl process.

Keywords: Endocrine disruptors; Estrogenic activity; Transformation products; UV/Cl; UV/H(2)O(2).