Distribution of estrogens, 17β-estradiol and estrone, in Canadian municipal wastewater treatment plants

Abstract

The distribution of female hormones, 17β-estradiol and estrone, was determined in effluents of 18 selected municipal treatment plants across Canada. Replicate 24-h composite samples were collected from the influent and final effluent of each treatment plant, and the removal efficiency compared to the operational characteristics of the plants. In conventional activated sludge and lagoon treatment systems, the mean concentrations of 17β-estradiol and estrone in influent were 15.6 ng/l (range 2.4–26 ng/l) and 49 ng/l (19–78 ng/l). In final effluents, the mean concentrations of both 17β-estradiol and estrone were reduced to 1.8 ng/l (0.2–14.7 ng/l) and 17 ng/l (1–96 ng/l), respectively. 17β-estradiol was removed effectively, >75% and as high as 98%, in most of the conventional mechanical treatment systems with secondary treatment. The removal of estrone was much more complex with removal varying from 98% to situations where the concentrations in the effluent were elevated above that detected in the influent. The estrogenicity, measured using a transfected estrogen receptor in yeast (YES) assay, was also variable, ranging from high removal to elevations of estrogenicity in final effluent. Although the apparent removals were not statistically correlated with either hydraulic (HRT) or solid (SRT) retention times, plants or lagoons with high SRT were very effective at reducing the levels of hormones. Well-operated plants that achieved nitrification also tended to have higher removal of hormones than those that did not nitrify. Laboratory aerobic reactor experiments confirmed the rapid removal of 17β-estradiol, estrone, and estrogenicity when exposed to sewage slurries.