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Abstract
The effluents discharged from sewage treatment works (STWs) are major sources of environmental estrogens, which poses an urgent need to explore appropriate techniques for effluent-polishing. In light of the debate concerning the effectiveness of constructed wetlands (CW) for the elimination of estrogens, the present study evaluated and compared the performance of two basic types of CW, free water surface (FWS) and subsurface flow (SSF) systems. Two FWS and two SSF field CW mesocosms were fed continuously with an STW effluent. All the mesocosms provided an effective elimination of estrogens and estrogenic activity. Unexpectedly, the performance of FWS mesocosms was not inferior to that of SSF mesocosms. Additional shading experiments demonstrated that the presence of filamentous green algae along with the sunlight enhanced the removal of estrogens and estrogenic activity in FWS mesocosms, enabling FWS mesocosms to perform comparably to SSF mesocosms. Microbial inhibition tests further indicated that Spirogyra sp. itself rather than algae-attached bacteria played an important role in the removal of estrogen and estrogenic activity.
Acknowledgements
This work was supported by the Grant-in-Aid for Scientific Research (Grant 1907118) from the Japan Society for the Promotion of Science, and the Provincial Natural Science Foundation of Jiangsu, China (BK2008322, BK2008500). The Global Center of Excellence program on Ecosystem Adaptability at Tohoku University from the Ministry of Education, Culture, Sports, Science and Technology of Japan is also appreciated.