Effect of Real Wastewater on Biotransformation of 17α-ethynylestradiol by Ammonia-Oxidizing Bacteria in Nitrifying Activated Sludge

17α-ethynylestradiol (EE2) is a synthetic estrogen
used as a key ingredient in an oral contraceptives pill. EE2 is an
endocrine disrupting compound, high in estrogenic potency.
Although EE2 exhibits low degree of biodegradability with common
microorganisms in wastewater treatment plants (WWTPs), this
compound can be biotransformed by ammonia-oxidizing bacteria
(AOB) via a co-metabolism mechanism in WWTPs. This study
aimed to investigate the effect of real wastewater on
biotransformation of EE2 by AOB. A preliminary experiment on the
effect of nitrite and pH levels on abiotic transformation of EE2
suggested that the abiotic transformation occurred at only pH <6.8.
Biotransformation of EE2 under the presence of municipal or
industrial wastewater demonstrated that different types of wastewater
affect EE2 biotransformation differently. Organic matters in
wastewater were believed to deteriorate EE2 biotransformation via
the competition effect. At a lower initial ammonium concentration,
EE2 biotransformation can be retarded and the extent of the
deterioration was COD-concentration dependent. However, when an
initial ammonium concentration was elevated, thisphenomena
disappeared. This is because when increasing the amount of the
primary substrate, more AMO enzymes can be produced resulting in
unlimited transformation of all compounds in the tests reducing the
competitive effect of organic matters on EE2.

• Natthawan Likitmongkonsakun
• Tawan Limpiyakorn

• 17α-ethynylestradiol
• ammonia-oxidizing bacteria
• nitrifying activated sludge
• wastewater.

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