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Wayne Van Voorhies, an NMSU microbiologist, left, and Peter Lammers, research professor and technical director of NMSU’s Algal Bioenergy Program, discuss concerns about a set of enclosed photobioreactors in a hoop house at NMSU’s Fabian Garcia Science Center. (NMSU PHOTO)
LAS CRUCES — What if a new system could be used to treat wastewater without the high input of electricity that regular sewage treatment plants require? What if this water treatment system, fed by nutrients in the wastewater, was able to use photosynthesis to produce renewable surplus energy to help meet the world’s growing energy demand?
Just such a win-win approach is currently being designed and tested by researchers at New Mexico State University. If successful, their system will provide a more sustainable method for treating wastewater, a new viable approach to producing electric power and liquid biofuels, and a revenue stream to offset infrastructure improvements.
The approach is being called the POWER — photosynthetically oxygenated waste-to-energy recovery — system, according to Peter Lammers, research professor and technical director of NMSU’s Algal Bioenergy Program.
Lammers and his colleagues have found that certain types of algae are highly effective in removing carbon, nitrogen and phosphorus compounds from municipal and agricultural wastewater.
“Unlike traditional wastewater plants that use bacteria for this purpose, processing wastewater using algal photosynthesis yields more biomass than the sludge output of current systems,” Lammers said. “The economic key to the POWER system is converting algal biomass into liquid fuel and electric power.”
The desert Southwest offers an ideal environment, in many ways, for the production of algae. Abundant sunlight, mild temperatures, and wide-open spaces for algae cultivation facilities have attracted new energy companies to the state, including Sapphire Energy, El Dorado Biofuels and Joule Energy.
But one essential component is in short supply in this arid environment: water.
It is this reality that has led researchers to explore using alternatives to fresh water that are less in demand, such as brackish water and municipal wastewater.
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.
Algae would be cultivated in sewage water outdoors in large enclosed plastic bag containers — “closed photobioreactors” — that prevent evaporative water loss. They heat up much like a greenhouse but are much cheaper. Such PBRs also retain carbon dioxide, a nutrient for the algae, thus fostering high-density algae production, and they keep wastewater odors and potentially harmful microbes contained.
The success of the system as a sustainable approach relies on efficiency at every stage.
Lammers and his colleagues hope 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 nonexistent wastewater treatment.
