UV photolysis and UV/H2O2 photolysis processes for estrogens removal in water

Abstract

International audienceThis study aimed at investigating the degradation of a mixture of estrogenic hormones (Estrone (E1), β-Estradiol (E2), and 17α-Ethinyl Estradiol (EE2)) in water by UV photolysis and UV/H₂O₂ photolysis. Firstly, the effects of water matrices (drinking water and treated wastewater) and H₂O₂ concentrations (10, 40, and 90 mg/L) were determined. The hormones were added in a UVC (λ=254 nm) pilot system running in semi-batch. Hormones degradation rates were measured by HPLC-UV. Secondly, a single concentration of H₂O₂ (20 mg/L) was tested in order to optimize oxidant cost. Hormones degradation rates as well as changes in estrogenic activity, measured by Yeast Estrogen Screen (YES), were followed at the same time. First results showed negligible degradation of E2 and EE2 by UV photolysis in both matrices. High UV fluences were needed to degrade 80% of E1 in drinking water (1300 mJ/cm²) and treated wastewater (1800 mJ/cm²). All hormones degradation rates were significantly improved in both water matrices at H2O2 concentration as low as 10mg/L. UV fluence of 400 mJ/cm² and 90mg/L of H₂O₂ would enable to remove 80% of all hormones in treated wastewater. Water quality could highly influence the treatment efficiency as shown by higher UV fluences required to reach the same result in treated wastewater than in drinking water. Estogenic activity, measured by YES bioassay, could not be removed by UV photolysis whereas it decreased in the same trend than E2 and EE2 removal rate when combining UV and 20 mg/L of H₂O₂. No high estrogenic by-products were formed. These results pointed out that estrogens removal can be highly enhanced by UV/H₂O₂ photolysis in drinking water and treated wastewater. By combining the approriate concentration of H₂O₂ and UV fluence, it would be possible to design a cost effective treatment for small and midlle sized WTPs