April 2008, Vol. 20, No.4

Research Notes

Seeking To Destroy Hormonelike Pollutants in Wastewater

 

When it comes to endocrine-disrupting compounds and other microconstituents, the burden of removal from wastewaters is often put on the shoulders of wastewater treatment plant facilities, rather than the source. But thanks to new research, that burden may be lightened.

Researchers report the effectiveness of a powerful, environmentally friendly catalyst in the destruction of various estrogens that currently escape complete removal in wastewater treatment plants. Their study appeared recently in the American Chemical Society (ACS; Washington, D.C.) publication Environmental Science & Technology.

In the new study, Nancy Shappell, a research physiologist at the U.S. Department of Agriculture’s Biosciences Research Laboratory in Fargo, N.D., and colleagues explain that endocrine disruptors — both natural hormones and hormonelike compounds — have been detected in surface waters, according to an ACS press release. Many of these endocrine disruptors have estrogenic activity. Ethinylestradiol, for instance, is an active ingredient in birth-control pills and is a major source of environmental estrogenic activity, ACS said.

To address this problem, the researchers tested a new catalyst called Fe-TAML, or Fe-B*. In the presence of hydrogen peroxide, the catalyst quickly and effectively destroyed various forms of estrogens typically found in post-treatment wastewater, removing 95% of the chemicals — including ethinylestradiol — in 15 minutes.

Estrogenic activity also was diminished to a similar extent. Further research will evaluate Fe-B*’s efficacy on actual wastewater, in addition to more extensive evaluation of byproduct toxicities. Usefulness in wastewater treatment could be doubly beneficial, as Fe-B* has been reported to destroy harmful bacterial spores.

To download a copy of “Destruction of estrogens using Fe-TAML/peroxide catalysis,” access pubs.acs.org/cgi-bin/sample.cgi/esthag/asap/pdf/es7022863.pdf.

Decontamination System Kills Anthrax Rapidly With No Lingering Effects

Researchers at the Georgia Tech Research Institute (GTRI; Atlanta), in collaboration with Stellar Micro Devices Inc. (SMD; Austin, Texas), have developed prototypes of a rapid, nondisruptive, and less expensive method that could be used to decontaminate bioterrorism hazards in wastewater in the future, according to a GTRI news release.

Using flat-panel modules that produce X-rays and ultraviolet-C (UV-C) light simultaneously, the researchers can kill anthrax spores in 2 to 3 hours without any lingering effects. While the system also has the ability to kill anthrax spores hidden in such places as computer keyboards without causing damage, with increased efficiency, UV-C panels could be used for purification applications.

“We may be able to use UV-C panels to clean wastewater, which would be better than the lamps currently used,” noted Mark Eaton, president and CEO of SMD. “In the environment where the lamps must operate, they are very difficult to clean, whereas flat panels could be cleaned with a squeegee.”

“This is certainly an improvement over previous techniques,” said Brent Wagner, GTRI principal research scientist and director of its Phosphor Technology Center of Excellence. “The UV-C attacks spores on surfaces, and the X-rays penetrate through materials and kill spores in cracks and crevices.”

X-ray irradiation is used commercially to sterilize medical products and food by disrupting the ability of a microorganism to reproduce, according to the news release. UV-C also prevents replication, but both types of radiation can penetrate the outer structure of an anthrax spore to destroy the bacteria inside.

UV-C light in the modules is produced using the optical and electrical phenomenon of cathodoluminescence. Numerous electron beams are generated by arrays of cold cathodes, each acting like the electron gun in a cathode ray tube.

“When an electron beam hits a powder phosphor, it luminesces and emits visible and/or nonvisible light,” explained Hisham Menkara, a senior research scientist in GTRI’s Electro-Optical Systems Laboratory.

Wagner and Menkara had to determine the best UV-C emitting phosphor and optimize its properties for use with X-rays in SMD’s small flat-panel display, according to GTRI.

To find the best phosphor that emitted light in the UV-C region of the spectrum — wavelengths below 280 nm — the emission spectra of each phosphor were measured against the DNA absorption curve. This curve shows the optimal wavelengths to destroy an organism’s DNA, the news release states.

After investigating many different phosphors, the researchers chose lanthanum phosphate:praseodymium as the most efficient phosphor, with a power efficiency near 10%. Since the UV emission didn’t fall completely under the DNA absorption curve, the relative “killing efficiency” was approximately 50%.

In the laboratory, Menkara created the phosphor by mixing precursors lanthanum oxide, hydrogen phosphate, and praseodymium fluoride in a glass beaker with methanol and ammonium chloride. Air-drying the mixture in a fume hood caused the methanol to evaporate completely. The resultant cake was crushed into a fine powder, heated in a furnace to a temperature as high as 1250°C for 2 hours, and crushed again.

“To determine the best conditions for producing the highest-efficiency phosphor, we tried different precursors and completed the firing under different atmospheric conditions and temperatures,” Menkara explained.

Test results showed that higher temperatures were more efficient, and a capped quartz tube was the best container to hold the powder inside the furnace.

With the improved phosphor, laboratory tests conducted by SMD showed that the combined X-ray and UV-C decontamination system could kill anthrax spores.

For more information, contact Menkara at hisham@phosphortech.com.

Agriculture Changing Chemistry of Mississippi River

 Midwestern farming and increased water flowing into the Mississippi River as a result have injected the equivalent of five Connecticut Rivers’ worth of carbon dioxide into the Mississippi each year during the last 50 years, according to a study published recently in the journal Nature.

“It’s like the discovery of a new large river being piped out of the Corn Belt,” said Peter Raymond, lead author of the study and an ecologist at Yale University (New Haven, Conn.). “Agricultural practices have significantly changed the hydrology and chemistry of the Mississippi.”

The research team analyzed Mississippi River data as much as 100 years old, the National Science Foundation (NSF) reports in a news release. The data had been warehoused at two New Orleans water treatment plants.

“This impressive effort has led to important conclusions about the influence of land-use practices on carbon dioxide in the environment,” said Martyn Caldwell, program director in NSF’s division of environmental biology. “The implications for other materials being transported into river systems are significant.”

The researchers tracked changes in the levels of water and bicarbonate, which forms when carbon dioxide in water in soil dissolves minerals, according to the news release. Bicarbonate plays an important, long-term role in absorbing atmospheric carbon dioxide, a greenhouse gas. Oceans then absorb carbon dioxide but become more acidic in the process.

“Ocean acidification makes it difficult, for example, for certain organisms to form hard shells,” said Eugene Turner, a co-author of the research paper and a marine ecologist at Louisiana State University (Baton Rouge).

The researchers concluded that liming and farming practices, such as changes in drainage, crop type, and rotation, likely are responsible for the majority of the increase in water and carbon in the Mississippi, according to NSF. They believe that increased nutrients in the Mississippi also are altering the chemistry of the Gulf of Mexico, into which the Mississippi flows.

Contact Raymond at peter.raymond@yale.edu. To purchase a PDF copy of the study in Nature, see www.nature.com/nature/journal/v451/n7177/pdf/nature06505.pdf.

Preventing Groundwater Contamination at Military Installations

Agricultural lime — a common gardening additive — holds the key to preventing groundwater contamination at hundreds of U.S. military installations nationwide, according to the research of Steven Larson of the U.S. Army Corps of Engineers’ Engineer Research and Development Center–Environmental Laboratory in Vicksburg, Miss.

Larson recently received a Project-of-the-Year Award from the U.S. Department of Defense’s Environmental Security Technology Certification Program for his work in demonstrating the efficacy and efficiency of using a common, inexpensive household product to avert potentially extensive, costly environmental damage at operational hand-grenade ranges.

Grenade ranges are among the most heavily used training areas in the military, according to a news release from the Defense Department’s Strategic Environmental Research and Development Program. These ranges consist of large sand pits surrounded by cement walls into which troops practice throwing live grenades. If the grenades fail to fully explode, munitions constituents, such as RDX, may remain in the sand. Over time, large amounts of RDX can accumulate in the soil and eventually contaminate the groundwater on the military installation and potentially in surrounding communities.

Larson and his colleagues successfully demonstrated that tilling agricultural lime into the sandy soil of hand-grenade ranges increases the pH level in the soil, which leads to the immobilization of heavy metals and the degradation of explosive compounds, such as RDX, the news release says.

“It sounds simple, but understanding how the lime works, proving that it works in the field, and knowing how frequently it needs to be applied is complicated science,” said Jeffrey A. Marqusee, director of the Environmental Security Technology Certification Program.

Applying lime on a regular basis can be incorporated into standard range maintenance procedures at minimal cost while having zero impact on the military’s ability to continue to train soldiers, Marqusee said. “As a result of Dr. Larson’s work, we now have the data to prove that this proactive approach should become standard best management practice for grenade ranges across DoD [the Department of Defense] in the future,” he said.

For more information, contact Larson at Steven.L.Larson@erdc.usace.army.mil.