April 2011, Vol. 23, No.4
An organic hop toward reducing estrogen in wastewater
Rabbit food could offer an inexpensive treatment solution to reduce estrogen in wastewater.
A team of scientists tested the ability of a variety of materials, including rabbit food, to see if any might reduce estrogen levels in wastewater. The team, including University of Cincinnati (UC) professor of environmental engineering Makram Suidan and environmental engineering student Ruth Marfil-Vega and U.S. Environmental Protection Agency research engineer Mark Mills, also tested the efficacy of these materials in reducing concentrations of male hormones such as testosterone, androstenedione, and progesterone, according to a UC news release.
The researchers used synthetic wastewater in stainless steel containers — to avoid any absorption of the hormones by plastic containers — to test the materials’ ability to reduce estrogen levels after a 72-hour contact period. They found that rabbit food resulted in abiotic transformation and absorption of four different types of estrogen. The rabbit food worked on both naturally occurring and synthetic estrogen, reducing levels of the hormones by more than 80% in wastewater.
The other four materials tested — clays, starch, casein, and tryptone — were found to reduce estrogen levels in wastewater by only 10%, a UC news release says. None of the treatment materials, including rabbit food, had any effect on male hormone levels.
Rabbit food, made of organic vegetable matter, was chosen because it is free of hormones. Similar vegetable matter could be safely added to wastewater, Suidan explained in the news release.
Further studies will seek to determine how the rabbit food reduced estrogen levels. The researchers believe a catalytic process occurred where the estrogen compounds appeared to bind to the rabbit food in the presence of oxygen, Suidan said in the news release.
Study findings were published in the article “Abiotic Transformation of Estrogen in Synthetic Municipal Wastewater: An Alternative for Treatment,” in the November 2010 issue of Environmental Pollution.
Iron-recycling bacterium exemplifies sustainability
A marine bacterium could be the poster child for sustainability, surviving by recycling iron. Because iron is scarce in oceans, the bacterium, Crocosphaera watsonii, uses its iron differently during the day and night.
During the day, it uses iron in enzymes for photosynthesis to make carbohydrates; during the night it appears to reuse the same iron with different enzymes to produce organic nitrogen for proteins, according to a news release by the Woods Hole Oceanographic Institution (WHOI; Falmouth, Mass.).
Scientists at WHOI and the Massachusetts Institute of Technology (MIT; Cambridge) call the capacity to conserve iron and use it to satisfy two metabolic demands “hot bunking,” which refers to a practice where more than one person is assigned to the same bunk on a ship and uses it at different times.
Crocosphaera, which is a type of cyanobacteria,is one of the few marine microbes capable of converting dissolved nitrogen gas into organic nitrogen. As the sun rises, the bacterium breaks down iron-containing nitrogenase enzymes, releasing iron that can be used to make photosynthetic enzymes. The photosynthetic enzymes are needed to convert dissolved carbon dioxide into carbohydrates. When the sun sets, many of the photosynthetic enzymes are broken down, releasing the iron again to be recycled back into nitrogenase, the news release explains.
WHOI scientists used proteomics — the study of proteins made from instructions encoded in genes of an organism — to study Crocosphaera. They used mass spectrometers to distinguish between and measure the inventory of iron-containing proteins during dark and light periods, the news release says. The scientists found nitrogen-fixing enzymes largely absent during the day and present at night. Iron-containing photosynthetic enzymes decreased during dark periods and reappeared during light periods. The scientists estimate that the organism survives with about 40% less iron than it would need if it maintained both sets of enzymes, the news release says.
Scientists at MIT explored the implications of Crocosphaera’s hot bunking ability, using a numerical model that simulates global ocean circulation, biogeochemistry, and ecosystem dynamics. The model showed that the bacterium’s ability to reduce its iron requirements enabled it to inhabit ocean regions with low levels of iron. It also allowed the same iron supply to support more growth of the cyanobacteria and more nitrogen fixation that supports other marine life higher up on the food chain, the news release says.
The National Science Foundation, the WHOI Ocean Life Institute, the National Science Foundation-funded Center for Microbial Research and Education, and the Center for Environmental Bioinorganic Chemistry at Princeton (N.J.) University funded the research. The findings were reported Jan. 10 in the Proceedings of the National Academy of Sciences.
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