[Abstract]

Pollution of the Aquatic Environment with Steroid Estrogens

Henrik Rasmus Andersen

Pollution of the aquatic environment with steroid estrogens and xeno-estrogens from sewage outlets causes development of imposex and stimulates non physiological synthesis of vitellogenin in feral fish.

The first topic for this Ph.D. thesis was to investigate if concentrations of these estrogenic substances in sewage outlets were higher than the published effect concentrations in Denmark and therefore if it could be expected that feral fish are affected. It was concluded that estrogen concentrations are higher than published effect concentrations in a minority of the investigated cases which means that effects can occur. Based on comparisons of concentrations in sewage effluents and effect concentrations for each estrogenic chemical suspected of causing environmental effects it is concluded that the active ingredient in the contraceptive pill, 17a-ethinylestradiol, poses the highest risk of causing estrogenic effects. The natural steroid estrogens, 17ß-estradiol and estrone are also significant contributors to the estrogen load.
Xeno-estrogens, which are synthetic industrial chemicals, pose a considerable less risk for estrogen effects in the environment than the steroid estrogens.

In order to improve the knowledge about the environmental chemistry of steroid estrogens and hence the possibility to improve the removal of steroid estrogens, the fate of steroid estrogens was investigated in a sewage treatment plant with a remarkably good removal rate for steroid estrogens.

Analytical methods for quantifying steroid estrogens concentrations in sewage and sludge were developed. With these methods concentration profiles were created for steroid estrogens through the treatment process of the sewage treatment plant.

A mass balance for the steroid estrogens concluded that all three steroid estrogens were primarily degraded by biodegradation in the active sludge treatment step of the plant. Sorption to sludge removed 4 % or less of the steroid estrogens from the plant. Sorption and desorption were, however, important for the dynamic of the steroid estrogen fate inside the treatment process, which is illustrated by the steroid estrogens being mainly sorbed to sludge during some stages of the treatment process.

Comparison of the total mass balance of the sewage treatment plant with a less detailed mass balance performed on the plant before major reconstruction leads to the conclusion that the important factors for a excellent removal of steroid estrogens were a high sludge retention time and a long retention time for water in the active sludge treatment.