Distribution of estrogenic steroids in municipal wastewater treatment plants in Tehran, Iran

Background: Estrogenic steroids such as estrone (E1), 17 beta-estradiol (E2), estriol (E3), and 17 alpha-ethinylestradiol (EE2) are among the most potent endocrine disrupting compounds (EDCs). Compared with North America, Europe and Japan there is no reliable information on the concentration of steroid hormones in wastewater treatment plants (WWTPs) influents and effluents in Iran. The aim of the present study was to determine the amounts of E1, E2, E3, and EE2 influents and effluents of 7 municipal WWTPs across Tehran, the capital city of Iran, in two seasons, summer and autumn, through solid-phase extraction (SPE) gas chromatography-mass spectrometry (GC-MS). Results: The results showed that the concentrations of E1, E2, and EE2 in influents ranged from 6.54-18.76 ng/L, 1.02-8 ng/L and 4.18-11.76 ng/L, respectively. Also, the concentrations of E1, E2, and EE2 in effluents ranged from 1.04-4.99 ng/L, 0.5-2.20 ng/L and 0.5-2.58 ng/L, respectively. The levels of E3 were below the detection limit (0.5 ng/L). The percentage removal rate of E1, E2 and EE2 ranged between 61.76-87.25%, 50.98-82.63%, and 66.3-90.25%, respectively. Results indicated no significant correlation between hormone concentrations and seasons. Conclusions: The study showed that WWTP number 7 had significant differences in influent hormone concentrations compared with others. Results only showed a significant relationship between hormones and TSS removal rate, but there was no significant relationship between hormones and COD removal rate. The removal rate of hormone in WWTP number 4 and 7 were significantly different from the others. There was no significant correlation between hormone concentrations and seasons.