Sushi, Seaweed, and Sewage

Ah, the delectable taste of sushi. Depending upon on the type of sushi you choose, those tidbits of tastiness embraced in a dark green “nori” wrap are actually encased in seaweed. “Seaweed?” you say. Yes. Seaweed.

Nori is the Japanese name for edible seaweed species of the algae genus Porphyra. While this algae has been a delightful addition to cuisine for centuries, other forms of algae are being put to use in industrial applications ranging from biofuels to wastewater.

Algaewheel image used with permission.

Arizona can pride itself on being on the cutting edge of algae biofuel research. In the Fall 2014 issue of Arizona Water Resource, The University of Arizona, College of Agriculture and Life Sciences, Water Resources Research Center (say that three times, fast), reported on two algae testbed projects being funded by the U.S. Department of Energy. The goal of this research is to promote advances in algal technology while being sensitive to the emerging technology’s water footprint.

Essentially what researchers are trying to do is figure out the best conditions to produce a large quantity of algae-based biofuel with minimal water usage. Algae’s high lipid content and the fact it is a renewable resource are two reasons it is suitable as a biofuel.  Currently “estimates for water use range from 3 gallons of water per gallon of algal biofuel to a thousand times that quantity.” With such a disparity, clearly more research needs to be done to minimize water use while maximizing biofuel production. Still, as oil supplies continue to dwindle, we can remain hopeful that algae may become a potential alternative renewable source of fuel.

Another promising algal innovation is from an Indianapolis based company called OneWater. They have developed a small scale waste water treatment system called the “Algaewheel” which was awarded the 2015 Water Environment Federation (WEF) Innovative Technology Award.

Typical waste water treatment systems use a mixture of microorganisms called “activated sludge” to breakdown waste products using a series of aeration tanks, clarifiers, filters and digesters. Most treatment plants are large scale and serve an entire community. They are expensive to build and operate and are usually located on the outskirts of town to reduce the nuisance conditions of odor and noise,

The Algaewheel system is remarkably simple. True to its name, it is essentially a series of rotating wheels coated with a biofilm of algae. OneW
ater’s company website describes the process saying “Algae grow on rotating wheels, using light, CO2 and nutrients. Algae produce oxygen, consume carbon-dioxide, and generate polysaccharides (sugars). Bacteria consume the oxygen and sugars and produce carbon dioxide – completing the cycle.”

The Indiana Department of Natural Resources (IDNR) retrofitted their seasonal waste treatment plant at Summit Lake State Park with an Algaewheel system with very good results. Commonwealth Engineers, the consulting engineers for the IDNR Summit Lake project, noted seasonal waste treatment systems have special challenges because the variability in flow rate and load can make it difficult for small treatment systems to meet permitted effluent levels.

Commonwealth Engineers has been pleased with the results at Summit Lake State Park. Their website mentions several benefits the Algaewheel waste water system offers.  Specifically, “it is modest in cost, easy to operate and maintain, readily meets effluent standards even with high variability in flows / loadings, and is operated at a fraction of the electrical costs required by competing “activated sludge” package plant facilities.”

So next time you’re out for sushi, remember that algae isn’t just for lunch anymore.

– Sandra Hurlbut

*I wrote this article in the Fall of 2015 for the Southern Arizona Contractors Association.

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