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Fate of EDCs in Municipal Wastewater Treatment Plants
Activated sludge aeration tank of a WWTP. Aerobic biological treatment can reduce the levels of suspected EDCs in treated effluent, but treatment performance varies greatly by plant.
Research & Development’s National Risk Management Research Laboratory (NRMRL) conducts research on the efficacy of existing risk management techniques to minimize exposure to suspected endocrine disrupting chemicals (EDCs) and develops new risk management tools for EDCs where needed. This research includes studies of concentrated animal feeding operations, drinking water treatment, contaminated sediments, pollution prevention techniques, combustion processes, and wastewater treatment.
Impact Statement: Reports in the scientific literature of suspected EDCs observed in wastewater treatment plant effluents and in surface waters impacted by plant outfalls are now familiar. The most commonly reported EDCs in studies on the impact of wastewater treatment are reproductive steroid hormones (especially estrogens) and the estrogenic biodegradation products of alkylphenol ethoxylate surfactants. For example, a recent publication by the U.S. Geological Survey showed that reproductive hormones and estrogenic alkylphenols were present in 40% and 70%, respectively, of the surveyed U.S. surface waters.
However, we know very little about why wastewater treatment plants often appear to be sources of EDCs to the environment. This project is designed to answer the following questions:
- What is the fate of relevant EDCs within typical wastewater treatment plants, i.e., what is the performance of each unit process in the plant at removing EDCs?
- For typical designs and operating strategies, what is the EDC content of the plant effluent and bio solids based on mass concentration and endocrine activity?
- Do some plant designs perform better than others?
How can typical designs be improved to increase removal of EDCs in a cost-effective manner?
One of the two pilot wastewater treatment plants used to determine the fate of EDCs within a plant's unit processes.
Project Description: The initial effort in this project area is being carried out using two pilot-scale wastewater treatment plants (see photo). The modest scale of the plants allow operating parameters to be easily varied. Pilot plants are fed an artificial “raw” wastewater of constant composition, and spiked with EDCs thereby facilitating steady state performance monitoring . Both plants are typical municipal (POTW) designs, i.e., primary and secondary treatment. The two plants differ only in the type of sludge digestion: one plant has anaerobic digestion, the other aerobic digestion. The EDCs in the feed and monitored throughout the plant include reproductive hormones (estradiol, estrone, estriol, ethinyl estradiol, testosterone, androstenedione, progesterone) and the surfactant, nonylphenol ethoxylate (n=12). Many of the biodegradation products of nonylphenol ethoxylate are monitored including all ethoxylates and nonylphenol.
The project was planned with several phases:
- Build pilot wastewater treatment plants and simulate typical POTW operation (see photo)
- Develop analytical methods to monitor target EDCs in all streams within the plants (see Products)
- Operate the plants under steady state conditions to simulate various common operating strategies. Determine the fate of the EDCs within the plants for each steady state.
- Provide recommendations on operating strategies to maximize EDC removal by typical municipal wastewater treatment plants.
Results: Future work beyond that outlined above include studies on the fate within full-scale treatment plants, and investigation of the performance of small community and on-site treatment systems, such as septic systems and constructed wetlands, on removal of EDCs.
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Publications & Products:
“Determination of Sex Hormones and Nonylphenol Ethoxylates in the Aqueous Matrices of Two Pilot-Scale Municipal Wastewater Treatment Plants” by Mar Esperanza, Makram T. Suidan, Fumitake Nishimura, Zhong-min Wang, George A. Sorial, Alan Zaffiro, Paul McCauley, Richard Brenner, and Gregory Sayles. Manuscript submitted for publication.
In Situ and On-Site Bioremediation - The Seventh International Symposium, Orlando, June 2003. "Analysis of Steroids in Wastewater" by M. Esperanza, A. Zaffiro, M.T. Suidan, G.A. Sorial, P. McCauley, and R.C. Brenner.
Effective Risk Management of Endocrine Disrupting Chemicals Workshop, Cincinnati, OH, September 18-19, 2001. "An Engineering Approach to Evaluate Estrogenic EDCs Fate During Wastewater Treatment" by Paul McCauley (PDF, 866 Kb, 24 pp).
Contact Information: For more information concerning fate of EDCs in wastewater treatment plants, please contact Richard Brenner, Paul McCauley, or Gregory Sayles.