Determination of estrogenic hormones in sewage and effluent of a decentralized sewage treatment plant by activated sludge

Abstract

Estrogenic hormones from sewers reach water bodies and can disrupt aquatic organisms. Secondary treatment of sewage treatment plants (STP) can remove some of those hormones, even in decentralized STPs, although there are few studies regarding this. In activated sludge systems, efficient removal has been attributed to hydraulic retention time (HRT), sludge age, biological denitrification and organic load. This study sought to quantify the hormones estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethynylestradiol (EE2) in the sewage and effluent of a decentralized STP with activated sludge, and also to characterize this college campus STP regarding received organic matter, hydraulic retention time and nitrogen removal. Hormone levels were determined by liquid chromatography with UV detection. The results showed hormone concentrations far superior to those found in the literature in both the sewage (5.158 ± 2.747; 7.434 ± 4.356; 5.200 ± 3.331 e 5.638 ± 4.312 μg L^-1 of E1, E2, E3 and EE2) and the effluent (5.062 ± 3.366; 4.191 ± 3.527; 7.743 ± 3.951, 2.550 ± 2.162 of E1, E2, E3 and EE2). In the sewage, the high concentration could be related to a large predominance of urine, given the high level of nitrogen detected, or to low generation of sewage and to sample collection in dry periods causing decreased dilution of hormones. Insufficient removal of estrogens due to short HRT (2h05) and irregular denitrification (-54 to 61%) can be the reason for high concentrations of estrogens found in the effluent. Furthermore, deconjugation of hormones may have occurred during treatment.