Biodegradation of oestrogens in nitrifying activated sludge
Xiaokang Zhou1, Jan A Oleszkiewicz
1Department of Civil Engineering, University of Manitoba, Winnipeg, Canada.
Environmental Technology
|November 5, 2010
Summary
Heterotrophic bacteria are key to removing 17beta-oestradiol (E2) from wastewater, while synthetic 17alpha-ethinyloestradiol (EE2) is more resistant to degradation in activated sludge systems.
Area of Science:
- Environmental microbiology
- Water treatment technologies
- Endocrine disruptor removal
Background:
- 17beta-oestradiol (E2) and 17alpha-ethinyloestradiol (EE2) are potent endocrine-disrupting compounds frequently detected in wastewater.
- Understanding the microbial degradation pathways of these oestrogens is crucial for effective wastewater treatment.
Purpose of the Study:
- To investigate the degradation of E2 and EE2 in aerobic activated sludge.
- To determine the influence of solid residence time (SRT) and nitrification inhibitors on oestrogen removal.
- To identify the microbial groups responsible for oestrogen degradation.
Main Methods:
- Experiments were conducted in an aerobic activated sludge system using synthetic wastewater.
- Varied solid residence times (SRTs) from 12 to 20 days.
- Nitrification inhibitor allylthiourea (ATU) was used to assess microbial roles.
Main Results:
- E2 was efficiently converted to oestrone (E1) under all tested conditions.
- E2 degradation followed first-order kinetics, with degradation rates decreasing at longer SRTs.
- EE2 removal was consistently low (~20%) and unaffected by SRT or ATU, indicating its recalcitrance.
- Ammonia-oxidizing bacteria were not significant contributors to E2 or EE2 degradation.
Conclusions:
- Heterotrophic bacteria are the primary agents responsible for the degradation of E2 and EE2 in activated sludge.
- EE2 is significantly more resistant to biodegradation than E2 in these systems.
- Wastewater treatment strategies should consider the recalcitrance of synthetic oestrogens like EE2.
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