Effects of 17α-ethinyl estradiol (EE2) and removal potential by two microalgal species Chlorella vulgaris and Scenedesmus obliquus

Abstract

17α-ethinyl estradiol (EE2) is the primary component in birth control pills and is highly bioavailable when taken orally. However, 80 % of the administrated dose is excreted un-metabolized in feces and urine, leading to its detection in water bodies and wastewater effluent from conventional treatment plants. EE2 negatively impacts on aquatic ecosystems, including disruption to the endocrine system of organisms, causing feminization in males, egg production and fertilization perturbation.Microalgae-based wastewater treatment is a promising biological approach for removing pollutants from the environment, including emergent and persistent contaminants. In this study, we evaluated the tolerance of two microalgal species Chlorella vulgaris (C. vulgaris) and Scenedesmus obliquus (S. obliquus) to various EE2 concentrations (0, 0.05, 0.10, 0.20, 0.30, 1.00, 8.0 and 22.0 mg L−1). Their potential to remove EE2 and the corresponding degradation kinetics were also assessed. The results showed that both species tolerated concentrations up to 8.0 mg EE2 L−1; however, at 22.0 mg EE2 L−1, C. vulgaris biomass decreased, and S. obliquus growth was inhibited. S. obliquus removed over 90 % of EE2 for most concentrations tested, while C. vulgaris achieved a maximum removal of 64 %. EE2 removal was attributed to microalgal biodegradation rather than sorption or bioaccumulation. The kinetic parameters determined that EE2 half-life was one day in S. obliquus culture and nine days in C. vulgaris. These findings confirmed that S. obliquus, especially, could reduce EE2 half-life in the environment, facilitating its removal. This information is valuable to understand EE2 degradation in aquatic ecosystems with microalgae presence.