July 2013, Vol. 25, No.7

Research Notes

Net-energy-producing system harnesses algae to treat wastewater

Producing energy while treating wastewater may seem too good to be true, but New Mexico State University (NMSU; Las Cruces) researchers are developing a system for the job. The POWER — photosynthetically oxygenated waste-to-energy recovery — system is being designed and tested to produce electricity and liquid biofuels while removing carbon, nitrogen, and phosphorus from municipal and agricultural wastewater, according to a university news release. 

University researchers working in the U.S. desert Southwest have found ample amounts of sunlight, mild temperatures, and open spaces for algae cultivation. But the other essential component — water — is in short supply. So, researchers explored using the alternatives of brackish water and municipal wastewater for algae cultivation, the news release says. 

The conceptual breakthrough was to go beyond thinking about wastewater as an ingredient in algae production to thinking about algae as an ingredient in a newly designed sewage treatment system,” the news release says. 

For the system, researchers cultivate algae in enclosed plastic-bag containers, or closed photobioreactors, to prevent evaporative water loss, the news release says. The system retains carbon dioxide, which is a nutrient for algae, to foster high-density algae production and contain both odors and potentially harmful microbes, the news release says. 

Researchers also have found that certain types of algae are more effective at treating wastewater and better at thriving in different climates. In a warm climate, the enclosed system reaches high heat levels, which can kill algae. Traditional systems address this problem by regulating water temperature with a cooling system, which requires a lot of electricity. The researchers used an alternative approach, testing strains of algae to find those evolved to handle high-temperature geothermal environments, the news release says. These algae thrive in warm environments, producing large amounts of biomass quickly while removing nutrients to yield clean water, the news release says. An added benefit is that the strains provide an acidified environment that at high daytime temperatures neutralize microbial pathogens in the wastewater.  

The algae also are mixotropic, thriving during periods of low sunlight by removing organic carbon in the wastewater, the news release says. Some of the algae even can tolerate high carbon dioxide levels, suggesting possible applications for recycling carbon dioxide, the news release says.  

The system could be employed using various types of algae that thrive in different temperature profiles and other conditions, the news release says. The system also should be scalable for various sizes. And because it is a net-energy producer, it should be adaptable in developing countries, the news release says. 

Several enclosed-system prototypes are being tested in a hoop house near existing algae test beds at NMSU’s Fabian Garcia Science Center. The house was constructed to enable testing that would maximize system heat during the winter months, the news release says. Researchers also are working with a species of hot-springs algae and a species of Chlorella that produces maximum levels of biofuel oil at lower temperatures, the news release says. 


Turning your mobile phone into an advanced scientific tool  

A new device could turn your mobile phone into an advanced tool for scientists and doctors. The device, which can be modified to fit any mobile phone that has a camera, brings fluorescent microscopy and flow cytometry to areas with limited resources, according to a Journal of Visualized Experiments news release.  

The tools, used in biomedical research, often require expensive, bulky equipment. In resource-poor countries, there’s a need for more-compact, cost-effective devices, the news release says.  

Flow cytometry is used to count and characterize cells in a liquid sample, particularly in the fields of molecular biology, pathology, and immunology. It enables everything from the detection of white blood cells in blood to Escherichia coli contamination in water and other liquids, the news release says.  

With the device, a retrofitted mobile-phone camera can capture images from a fluorescent microscope and flow cytometer so professionals can perform a range of tests, such as checking for contaminated water, the news release says.  

Bringing these tools to a common mobile phone expands their reach. The United Nations estimates that there are more than 6 billion mobile phones worldwide, providing a massive network able to conduct complex biological tests, the news release says.  

The journal has published a new video article by Aydogan Ozcan demonstrating the technology. In the video, Ozcan and other electrical and biological engineers from the University of California–Los Angeles show the construction of the device and how it can be modified to fit phones, the news release says. 

Ozcan and his colleagues have filed intellectual property licenses as part of Holomic LLC (Los Angeles) for the mobile device. 


Examining prevalence of antibiotic resistance genes in anaerobic digesters  

Conditions at water resource recovery facilities have been described as a “breeding ground” for the “selection, transfer, and dissemination of antibiotic resistance genes,” according to a research report published in the May issue of Water Environment Research. 

The report describes how Virginia Polytechnic Institute and State University (Blacksburg) researchers set out to determine the effect that antibiotic and silver nanoparticles have on the occurrence of antibiotic resistance genes in thermophilic anaerobic digesters.  

The researchers hypothesized that antibiotics and silver nanoparticles could act as selection agents for proliferation of antibiotic-resistant genes in anaerobic digesters, the report says. They found that mesophilic and thermophilic anaerobic digestion reduces but does not eliminate antibiotic resistance gene loadings to the environment, and they found no significant difference between gene numbers in increasing concentrations of antibiotics and silver nanoparticles in the digesters.  

“Antibiotic resistance gene reductions remained constant despite the application of selection pressures which suggests that digester operating conditions are a strong governing factor of the bacterial community composition and thus the prevalence of [antibiotic resistance genes],” the report says. 

The report, “Effect of Silver Nanoparticles and Antibiotics on Antibiotic Resistance Genes in Anaerobic Digestion,” is available as an open-access document and can be downloaded free at http://goo.gl/pWxlq. 

Water Environment Research allows open access to one article per issue on a range of important technical topics such as nutrient removal, stormwater, and biosolids recycling.