ISOLATION, IDENTIFICATION, AND PREVALENCE OF ESTROGEN-DEGRADING CULTURES IN ACTIVATED SLUDGE

Reproductive hormones, including estrogens, are a class of personal care prescription drugs that have been recently detected in varies aquatic environments. The presence of these compounds in our environment has caused a great concern since they have been linked to the feminization of male fish in rivers receiving treated wastewater. A number of studies that focused on the performance of existing wastewater treatment plants on estrogen removal reported a wide range of estrogen removal, varying from less than 40% to even higher than 95% depending on the types of the estrogens. Using 14C-labeled estrogen, a recent study has shown 70-80% miniralization of 17b-estrodial to CO2 in activated sludge samples. Recently, the first 17b-estradiol-degrading culture isolated from activated sludge has reported. Above findings suggested that biodegradation maybe an important removal mechanism for estrogens in wastewater and that different estrogen degraders were present in the activated sludge. However, little is known about the presence, the diversity, and the characteristics of estrogen-degraders in the systems.

To address the biodegradation potential of estrogen during wastewater treatment, we have attempted to isolate, characterize, and detect estrogen-degrading cultures from activated sludge under various operating conditions. By using three estrogens (17b-estrodial, 17a- estradiol, and estrone) as model compounds during enrichment, we have isolated 28 pure cultures capable of degrading estrogens. After preliminary screening, four pure cultures showed a high degradation ability toward 17b-estrodial, 17a- estradiol, and estrone, and were chosen for detailed studies with respect to their degradation kinetics. Molecular characterization and identification using16S rDNA sequences of these cultures are in progress. Fresh sludge samples are currently collected from varies activated sludge processes to determine the diversity and the prevalence of estrogen-degrading cultures. The results of this study will greatly improve our understanding of these cultures and their roles in estrogen degradation, which will be particularly beneficial to engineers to determine if there is a need for modification or upgrade of existing biological treatment process for better estrogen removal.