A new device called an algae turf scrubber is being used to help clean the water in Baltimore's Inner Harbor.Go look at the video at the site (alas, it was not embeddable). Pretty cool construction for a bunch of kids, and a good way to learn some biology.
The device works by pumping polluted water into a shallow screened trough, and as the water flows through the trough, algae from the water attaches to the screen, experts said.
Once it's attached, the algae cleans the water, and the clean water is pumped back into the Inner Harbor.
"We know for sure that algae, just by the very fact that it's growing, removes nutrients. Because it's photosynthetic, it's adding oxygen to the water just by doing what it normally does," said Spencer Carroll of the Living Classrooms Foundation. "We know that it increases water quality, but we don't know to what extent."
Students at Living Classrooms have created a scale mode of the algae turf scrubber to learn about the system and conduct their own research.
As for cleaning the Harbor? Well, not so much. The scale of a system necessary to clean the Harbor would be a significant fraction of the size of the harbor itself, and while I'm sure there is some wasted land around Baltimore to use, I would guess the amount and cost of the land would be prohibitive, never mind the energy costs of running the pumps to power the thing. You could burn the algae to run the pumps, but that would release the nitrogen (one of the main pollutants they're trying to trap) back out into the air, unless they installed a power plant sized air scrubber. You get the idea.
And besides, Baltimore's bigger pollution problem is toxic materials sequestered in the sediments, and while the algae will take some out of the water, it would require geologic times to remove a the toxic metals and organics from the sediments.