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Downstream Without Hormones: Can Rabbit Food Solve an Emerging Environmental Problem?

EPA and partner scientists team up to investigate a potential inexpensive, sustainable solution for removing estrogen from wastewater.

Water treatment

Sometimes laboratory work does not always go as planned. EPA-supported investigators from the University of Cincinnati (UC) were puzzled by an unexpected occurrence: estrogen levels in the brew of artificial wastewater they created for testing dropped mysteriously, even before they had a chance to run the water through the scaled-down treatment plant setup for experimentation.

The research team was gearing up to investigate new practices and technologies to remove estrogen and similar hormone and hormone-like contaminants from wastewater.  The work is part of EPA’s commitment to protect human health and meet a requirement from the U.S. Congress to assess how a variety of chemicals, known collectively as Endocrine Disrupting Chemicals (EDC),  interact with the basic functions of the endocrine systems of people, fish, and wildlife.

While the female hormone estrogen is found naturally in the environment, increasing levels of synthetic estrogen, used in oral contraceptives, are a concern in wastewater discharge zones. Estrogen (and other hormone and hormone-like compounds) released into the environment through wastewater can disrupt normal development in fish and wildlife, and has the potential to adversely affect human health.  

Researchers looking over water treatment

EPA Postdoctoral Scientist Ruth Marfil-Vega and Makram Suidan at a Wastewater Treatment Plant. (Photo Courtesy of Dottie Stover/University of Cincinnati.)

To closely match the effluent that flows into working treatment facilities, the researchers added vegetation and other organic matter to create synthetic wastewater, then introduced steroids and other chemicals for testing. When the estrogen levels quickly fell to much lower levels than the amounts added, the scientists hit the “pause” button on the research.
“We worked hard at isolating what was reducing the estrogen levels so we could conduct our experiments,” says EPA postdoctoral researcher Ruth Marfil-Vega, Ph.D. Marfil-Vega was a graduate student at the University of Cincinnati (UC) during the rabbit food study, and generated a number of hypotheses on what caused the estrogen levels to drop.

After extensive testing, Marfil-Vega, her laboratory director at UC, Makram Suidan, Ph.D., and EPA researcher Marc Mills, Ph.D., identified what they suspected was behind the disappearing estrogen levels: the vegetable matter added to the test water. 

The researchers then moved to turn this “happy accident” into a potentially sustainable solution for wastewater treatment. Marfil-Vega was a UC graduate student during the rabbit food study, and generated a number of hypotheses on what caused the estrogen levels to drop. They chose a convenient source—rabbit food composed largely of compressed vegetable matter—and came up with striking results:  the rabbit food reduced the levels of four estrogens tested by more than 80 percent over a 72-hour contact period. The rabbit food even proved to reduce levels of synthetic estrogen typically used in oral contraceptives. Such estrogen presents a challenge to wastewater facilities because it is persistent in the environment, having long staying power in wastewater discharges.

Water treatment equipment

Wastewater treatment simulator in the laboratory used by the investigators. (Photo: Makram Suidan, University of Cincinnati).

Could the application to full-scale wastewater treatment systems mean that vegetation-containing materials as abundant as rabbit food, leaves, or even grass cuttings significantly reduce excess estrogen concentrations in treatment plant discharges? That's the next big question.

The researchers say they are confident the discovery meets or exceeds the “proof of concept” test and plan to continue working on ways to scale up the research in a cost-effective way. EPA’s Mills cautions that some questions remain in terms of how vegetable matter may work in “real” wastewater instead of the synthetic test waters the team created, how the vegetable matter would be removed after treatment, and other challenges.

According to UC’s Suidan, “It would be an inexpensive process to replicate in wastewater treatment plants and we are now experimenting to find out, specifically, why the rabbit food proved so effective in reducing estrogen levels.”

The investigators recently published their research results in the scientific journal Environmental Pollution (Ruth Marfil-Vega, Makram T. Suidan, Marc A. Mills. Abiotic transformation of estrogens in synthetic municipal wastewater: An alternative for treatment? Exit EPA Disclaimer Environmental Pollution, 2010) and are sharing their findings at professional conferences. They are optimistic that the translation of their discovery has a good chance of promoting a sustainable solution to a growing set of environmental and public health concerns—the payoff of persevering through a happy accident into a greener world.


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