December 2013, Vol. 25, No.12

Waterline

Ice that burns provides key to more efficient desalination

Scientists are searching for an affordable process to turn salty wastewater into water suitable for irrigation and drinking. One solution could be a new type of gas hydrate desalination that removes more than 90% of salt from wastewater, according to an American Chemical Society (ACS; Washington, D.C.) news release. 

Gas hydrate consists of water and a gas such as methane. When hydrates form, salts and other impurities are left behind; and when hydrates break down, gas and pure water are released. This method removes about 70% of salt from wastewater, but forming gas hydrates for desalination requires the costly process of cooling water down to 28°F. 

Researchers Yongkoo Seol and Jong-Ho, both from the U.S. Department of Energy’s National Energy Technology Laboratory, developed a less expensive version of this method involving a variation on methane hydrates, chunks of ice retrieved from the deep sea that burst into flame when brought to the surface, the news release says. They formed hydrates from water and carbon dioxide with gases cyclopentane and cyclohexane, improving efficiency of the method and removing more salt than the previous gas hydrate technique. 

Because this process can be performed near room temperature, the need for chilling is reduced. The process could help purify highly salty water produced by hydraulic fracturing, the news release says. The research report, “Increasing Gas Hydrate Formation Temperature for Desalination of High Salinity Produced Water With Secondary Guests,” appears in the journal ACS Sustainable Chemistry & Engineering. 

 



Algae matting waterways across the country

Extreme weather and an increase in nonpoint source pollution are resulting in widespread toxic algae outbreaks. A new online map released by Resource Media (San Francisco) shows 21 states across the U.S. have issued health advisories and warnings related to harmful algal blooms at 147 different locations on lakes, rivers, and ponds during the summer. A new report provides a look at the causes as well as the effects and costs of algae spreading across waterways, according to a National Wildlife Federation (NWF; Reston, Va.) news release. 

According to the report, “Toxic Algae: Coming Soon to a Lake Near You?,” released by Resource Media in partnership with the NWF Great Lakes Regional Center, several condition are contributing to the spread of toxic algae and lake closures. They include heavy rains increasing the volume of fertilizers and livestock manure entering waterways, failing septic systems, and high summer temperatures. Algae, such as cyanobacteria, can produce toxins that harm humans and pets and can damage tourism tied to lakes and other waterways, the news release says. 

The report urges federal public officials to set limits on phosphorus entering waterways, to maintain efforts to restore waterways, and to pass a strong Farm Bill that pays farmers to take actions to protect soil and water quality, the news release says. 

See the map at www.toxicalgaenews.com and the report at www.toxicalgaenews.com/toxic-algae-report-2013.php

 


Gliders collect data on ocean temperature and marine species

Ocean-monitoring gliders have traveled between the East Coast of North America and the Continental Shelf Break to collect oceanographic and animal-tracking data, according to a Dalhousie University (Halifax, Nova Scotia) news release. The 14 autonomous gliders were equipped with sampling instruments to collect, store, and transmit data on the shelf’s thermal structure for forecasting major storms and informing migration patterns of various marine animals. 

Researchers from U.S. and Canadian institutions teamed up to coordinate this large-scale survey to monitor the oceanographic conditions that directly influence storms and animal migration. Rutgers University (New Brunswick, N.J.) leads the mission. Dalhousie-based Ocean Tracking Network (OTN) and the U.S. Integrated Ocean Observing System also are participating. 

OTN contributed two Slocum gliders; these gliders move by altering their density to ascend or descend in the water column. Wings on the gliders convert vertical motion into forward motion. 

Eight of the gliders are equipped with Vemco (Bedford, Nova Scotia) mobile transceivers to record the presence of acoustically tagged animals. Gliders also will collect thermal data from the shelf because differences between air and sea temperatures power hurricanes, the news release says.  

Find data collected during the mission at http://gliders.oceantrack.org, www.ioos.noaa.gov/observing/observing_assets/glider_asset_map.html, and http://maracoos.org/blogs/main 


Leafy greens remove heavy metals from water 

Cilantro and other similar leafy greens may offer more than just flavor for food. Ivy Tec Community College (Carmel, Ind.) researchers working with Universidad Politécnica de Francisco I (Hildago, Mexico) scientists found that these plants show promise as biosorbents to remove lead and other potentially toxic heavy metals from water, according to an American Chemical Society (ACS; Washington, D.C.) news release. 

The research, presented at an ACS meeting, showed that the microscopic cells that comprise the plant’s outer walls may be suited for sorption of heavy metals, the news release says. Related plants, including parsley and cilantro, also have similar features that could make them biosorbents, explained university researcher Douglas Schauer at the meeting. Small-scale experiments showed that cilantro may be more effective than activated carbon in removing heavy metals such as lead, the news release says. 

Because cilantro grows in abundance in developing countries that need an inexpensive option to filter for heavy metals, use of the plant to filter water may provide a lower-cost alternative to traditional treatment such as using activated carbon or ion-exchange resins. Cilantro could be used in packets or reusable water filter cartridges, the news release says.