Biotransformation of Estrogens in Nitrifying Activated Sludge Under Aerobic and Alternating Anoxic/Aerobic Conditions

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Natural and synthetic estrogens present in municipal wastewater can be biodegraded during treatment, particularly in activated sludge. The objective was to assess the extent of transformation of 17-β-estradiol (E2) and 17-α-ethinylestradiol (EE2) by nitrifying activated sludge and evaluate potential relationships between availability of oxygen, nitrification rate, and estrogen removal. For each batch experiment, two reactors were set up—aerobic and alternating anoxic/aerobic—which were then amended with E2 and EE2 from methanolic stock solutions. The EE2 was persistent under anoxic conditions; under aerobic conditions, the observed level of its removal was 22%. The E2 was readily converted to estrone (E1)—faster under aerobic (nitrifying) than anoxic (denitrifying) conditions. During the initial anoxic conditions, a metabolite consistent with 17-α-estradiol transiently accumulated and was subsequently removed when the reactor was aerated. Higher removal rates of estrogens were associated with higher nitrification rates, which supports the contention that the nitrifying biomass was responsible for their removal.

Keywords: activated sludge; biodegradation; endocrine disruptors; estrogens; nitrification

Document Type: Research Article


Publication date: January 1, 2008

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  • Water Environment Research® (WER®) publishes peer-reviewed research papers, research notes, state-of-the-art and critical reviews on original, fundamental and applied research in all scientific and technical areas related to water quality, pollution control, and management. An annual Literature Review provides a review of published books and articles on water quality topics from the previous year.

    Published as: Sewage Works Journal, 1928 - 1949; Sewage and Industrial Wastes, 1950 - 1959; Journal Water Pollution Control Federation, 1959 - Oct 1989; Research Journal Water Pollution Control Federation, Nov 1989 - 1991; Water Environment Research, 1992 - present.
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