July 2013, Vol. 25, No.7


Scaling up algae operations

The San Diego Center for Algal Biotechnology has experience in growing algae for biofuel. But when the center took over a field laboratory in the Imperial Valley of California and expanded its algae growth operations to 1.6-km (1-ac) ponds, it encountered an obstacle — how to harvest algae from such a large area, according to Jim McMahon of Zebra Communications (Simi Valley, Calif.). 

Researchers tried several unsuccessful methods to harvest the algae from the ponds before finding the World Water Works (Oklahoma City) Algae Harvesting Technology Optimized dissolved-air flotation system. Pond water is pumped into the system, which separates algae from water.  

As air is dissolved into water, microbubbles form. The bubbles interact with algae particles, attaching to the biomass surface and causing them to float to the surface. They then are skimmed off the surface into a sieved Thickening BeachTM that thickens algae particles and enables free water to be drained, according McMahon. Clean water is continuously removed from the system and piped back into the ponds. 

Using the system, researchers were able to continually harvest algae from the ponds and add fertilizer to maintain a steady rate of algae production. The system processes up to 34,063 L/min (9000 gal/min) of algae-laden water at a 95% capture rate, yielding up to 20% algae concentrations, according to McMahon. 

For more information see www.algae.ucsd.edu . 

Images of snowflakes in free fall reveal crystallized complexity 

Snowflakes are unique, but most are not perfectly symmetric as is commonly believed, according to University of Utah (Salt Lake City) researchers.  

The researchers developed a high-speed camera system that has been photographing three-dimensional images of snowflakes for the past two winters, according to a university news release. Unlike other research, the device used in this study captures images of snowflakes as they fall, untouched by anything, the news release says. 

The device and supporting research can help improve computer simulations of falling snow and determine how snow interacts with radar. Snow often degrades microwave radar and communications, so the researchers want to determine how this occurs to help improve radar for weather and snowpack forecasting, the news release says. 

“Our instrument is taking the first automated, high-resolution photographs of the complexity of snowflakes while measuring how fast they fall, and is collecting vast amounts of data that can be used to come up with more accurate and more representative characterizations of snow in clouds,” said Tim Garrett, associate professor of atmospheric sciences at the university, in the release. 

Snowflakes often vary in size and composition. Flakes undergo such events as “riming,” in which water collides with and freezes on the surface, making it into an ice pellet known as a “graupel,” and collides with neighbors to become aggregate flakes.  

The researchers want to learn how the sizes and shapes of snow particles relate to how fast they fall; this is important because the life of a storm and where exactly snow falls depends on how fast snow precipitates, the news release says. 

The researchers are using automatic image-analysis software to characterize snowflakes by shape, complexity, size, and mass. They also are using radar to measure the precipitation structure in the air column and correlating this with the snowflake data.  

The device includes three industrial-grade, high-speed cameras and two sets of two motion sensors to measure the speed of falling snowflakes. 

NASA and the U.S. Army helped fund development of the camera, and the U.S. National Science Foundation funded the observations, the news release says. 

Plastic pollution travels to the Great Lakes 

The Great Lakes face yet another problem: plastic pollution. Floating plastic debris, often unnoticed because of its small size, has made its way into the lakes, according to an American Chemical Society (ACS; Washington, D.C.) news release.  

A research team led by Lorena M. Rios-Mendoza, a University of Wisconsin–Superior assistant professor, has been analyzing samples and contents of fish stomachs from the Great Lakes. Rios-Mendoza presented the team’s findings at the 245th National Meeting and Exposition of the ACS.  

The team found that 85% of plastic particles were smaller than 5.1 mm (0.2 in.), with much of it being microscopic. And between 1500 and 1.7 million particles were found per 2.59 km2 (1 mi2), the news release says. 

Researchers also collected samples from the southern Atlantic Ocean and found that the Great Lakes had 24% more microparticles than the ocean. 

Fish often mistake these particles for food, the news release says. Researchers received funding from the university.