The algae effect
Sun News Service
Nutrients are one of Lake Tahoe clarity’s arch enemies ” add too much nitrogen or phosphorous and algae will sprout, clouding the famed crystal clear waters.
So using algae to clean water of the very nutrients that help it grow is a pretty novel idea.
And it’s working, according to research done by Alan Heyvaert of the Desert Research Institute and Steve Patterson of Bio X Design.
“Kind of ironic huh?” Heyvaert said. “It’s kind of a logical natural next step when you think about it.”
Heyvaert and Patterson began their research with the idea that if water was filtered through a tank with a biofilm ” a screen covered in a layer of algae and nutrients ” the algae would absorb the nutrients it needs to grow.
Then the water filtered out of the tank would be cleaned of some of the nutrients.
“We are using the algae to remove the nutrients that they grow on when they’re in the lake,” Heyvaert said. “In the lake if you put in too much nutrients they grow and you get too much algae.”
The idea seems to be working.
The process removed almost all the nitrogen in preliminary testing the team did last year with synthetic runoff water at a lab in Tahoe City for the Tahoe Environmental Research Center.
It also removed a significant portion of the phosphorous, although the team suspects not all the phosphorous was removed because there was not enough nitrogen left after the process. Nitrogen and phosphorous work together to create algae blooms.
The process also removed 80 percent of the fine sediments in the water. The biofilms produce a gelatinous texture that attracts fine sediments, Heyvaert said.
Last year’s testing was done on a much smaller scale. About a month ago the researched moved to two stagnant storm water ponds in Incline Village near Village Boulevard. The research team installed three tall clear tanks that filter water from one dirty pond of water and let out clean water on the other side.
Heyvaert said the effects already are visible. On the clean side of the system, the surrounding water has less algae than the rest of the pond.
“There’s not much algae because the nutrients have been removed and the water coming through is clean,” Heyvaert said, pointing to a spout of water coming from the end of filtering system and going into the second pond.
The algae in the tanks in algae from Lake Tahoe, but the algae and clarity of the water varies from tank to tank. Each tank contains a different environment of algae.
“As it cleans the nutrients each tank ends up with a different set of algae growing,” Heyvaert said. “It’s like an ecological system that selects for the types of organisms that grow there.”
While the system seems effective so far, Heyvaert said it needs to go through more testing before it could be scaled up to be a large water treatment system.
One of the questions the research team faces is how to clean the biofilms if the system were to be produced on a large scale. Right now a Tahoe Environmental Research Center Research Assistant Collin Strasenburgh regularly cleans the films and tanks so that the algae does not become stagnant and ineffective.
However, that method would probably not work on a large scale, Heyvaert said.
For now, using algae to clean water of nutrients and sediments has been effective.
“It could work,” Heyvaert said. “People are pretty excited about it but it is important to remember that this is still a pilot scale system. We need to prove the technology.”