June 2011, Vol. 23, No.6
Determining the reaction and transport of tungsten in groundwater
Scientists are going to great depths to determine the reaction and transport of tungsten in the nation’s groundwater and aquifers.
Previously thought to be the nontoxic, environmentally friendly replacement for other metals, tungsten is a groundwater contaminant and growing concern, according to Saugata Datta, assistant professor of geology at Kansas State University (Manhattan). The naturally occurring metallic element, which is used primarily for incandescent light-bulb filaments and X-ray tubes, has been replacing lead in fishing weights and ammunition, according to a university news release. The problem is that tungsten has the potential to form toxic byproducts.
Datta began collaborating with Karen Johannesson, professor of earth and environmental sciences at Tulane University (New Orleans) to study the biogeochemistry of tungsten, finding out how it reacts and relates to groundwater and the surrounding environment, the news release says.
When tungsten is oxidized, it often seeps into the ground and even groundwater-bearing aquifers. During this process, it can mix with organic matter in soil and, in the presence of sulfur-rich solutions, form thiotungstate complexes, which are toxic, the news release says.
The researchers are looking at both pristine aquifers and aquifers affected with tungsten to create a conceptual model for this project and future studies.
Researchers are evaluating how concentrations of the metallic element change along groundwater flow paths and modify the groundwater makeup, the release says.
Tungsten has been connected to childhood leukemia in areas in the western United States with elevated concentration of tungsten in drinking water, and animal model studies show the potential for it to be toxic.
The Hydrology Division of the U.S. National Science Foundation in fall 2010 issued a 3-year grant to fund this study.
April WER open-access article reviews algal biofuel production
The April issue of Water Environment Research (WER), the Water Environment Federation (Alexandria, Va.) research journal, includes an open-access article that compares various process train options needed to produce algal biofuels. The article, “Production of Biodiesel and Biogas from Algae: A Review of Process Train Options,” looks at cultivation, harvesting, and conversion of algae into usable fuel and identifies areas where gaps in knowledge restrict the production of algal biodiesel and algae-derived biogas.
The article, which was written by researchers at the University of California–Merced, identifies energy-intensive processing and the inability to cultivate large quantities of lipid-rich algal biomass as major obstacles to algal biodiesel production. Anaerobic digestion of algal biomass requires fewer process train components and occurs regardless of lipid content. “In either scenario the use of wastewater effluent as a cultivation medium seems necessary to reduce greenhouse gas emissions and maximize water use efficiency,” the article says.
Anaerobically digesting algal biomass from low-technology wastewater treatment processes is identified as a “poorly investigated” appropriate technology approach to algal biofuels. Combining the processes can improve sanitation while providing a cleaner-burning biogas alternative to indoor biomass cooking systems, the article says.
The article concludes that anaerobic digestion is the most appropriate choice when considering energy, since it requires less processing than algal biodiesel. “These systems represent a low-technology, community-scale approach to algal biofuels,” the report says.
The article identifies technical obstacles throughout the process train for both industrial-scale and appropriate technology approaches to algal biofuels. In terms of knowledge gaps and research needs, the article notes that if genetic engineering is used to enhance lipid productivity, research on the biosynthesis of algal lipids is needed. Also, algal harvesting must be developed to bridge the technologies of anaerobic digestion of algal biomass generated during wastewater treatment processes.
The article is available free to all users at http://goo.gl/5EPbw.
Water Environment Research allows open access to one article per issue on a range of important technical issues such as nutrient removal, stormwater, and biosolids recycling. Find more at www.ingentaconnect.com/content/wef/wer.
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