Lammers and his colleagues are exploring an alternative approach, specifically testing strains of algae that have evolved in high-temperature geothermal environments.

Such algae thrive in the hotter PBR temperatures. As an added benefit, these strains provide an acidified environment that, at the high daytime temperatures, promises to neutralize microbial pathogens in the wastewater. The algae are also mixotrophic, which means they can thrive during periods of low sunlight by removing organic carbon in the wastewater.

"Some of these hot springs algae can also tolerate extremely high CO₂ levels, compared to most plants," said Wayne Van Voorhies, an NMSU microbiologist working on the project. "To cultivate these algae, we could use flue gasses directly out of a power plant, which are 10-15 percent CO₂."

This suggests a role for such algae in CO₂ recycling strategies.

Lammers and his colleagues hope that their enclosed PBR-based system could be adapted worldwide by employing a variety of different algae types with optimum temperature profiles compatible with different climates. It should also be scalable for communities of various sizes and, since it is a net energy producer, should be adaptable for communities in developing countries with inadequate or non-existent wastewater treatment facilities and severe resultant public health challenges.

According to Lammers, approximately two billion of the world's seven billion people live where there is no wastewater processing whatsoever.

 

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Adrian Unc is an environmental microbiologist in NMSU's Department of Plant and Environmental Sciences whose expertise is in wastewater and  human pathogens. He believes the system has great potential for improving human health.

"We think it would be rather easy and rapid to deploy such a system in any developing country that has the climatic conditions required, meaning sun and heat," he said.

Lammers also stressed that this basic approach could be adapted for waste treatment on large-scale dairy and livestock operations.

Several enclosed PBR prototypes are now being tested in a hoop house near existing algae testbeds at NMSU's Fabian Garcia Science Center. The hoop house was constructed to allow initial testing that would maximize system heat during the winter months.

The researchers are working with a species of hot springs algae from Yellowstone National Park and, with local winter climate conditions in mind, a species of Chlorella that Lammers says produces maximal levels of oil at somewhat lower temperatures.

Full outdoor testing will commence in the late spring. The performance of the various PBR designs and algae types will be evaluated to determine which combinations work best in the local environment.

"Modern sewage treatment processes were invented in an era of cheap energy," Lammers said. "'Business as usual' will not supply 7 billion humans with clean air, clean water and energy."

In addition to Lammers, Unc and Van Voorhies, the multidisciplinary team of researchers on the POWER system includes Shuguang Deng in Chemical Engineering and Nirmala Khandan in Civil Engineering.

For more about NMSU algal biofuels research, go to http://research.nmsu.edu/erl/algalbiofuels/testbed/.

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