Algae "scrubber" tackles harbor pollution

In their quest to cure Baltimore's ailing harbor, advocates and authorities have tried one gadget after another: floating wetlands, a solar-powered aerator, even a trash wheel.

Add now the "algal turf scrubber," a long wooden sluiceway in which harbor water is pumped over a bed of slimy green algae. The ecological restoration firm Biohabitats and the Living Classrooms Foundation invited news media to see the contraption set up on a former chromium plant site in Fells Point.

The gutter, 350 feet long by one foot wide, uses native algae to strip nutrients, suspended sediment and carbon from water and inject oxygen into it before returning it to the harbor. The algae feed on the nutrients in the water pumped down the sluiceway, just as they do in the open waters of the harbor and the Chesapeake Bay. 

"We call it 'ecological engineering,'" said Patrick Kangas, director of the Algal Ecotechnology Center at the University of Maryland. "What you see here is basically a controlled algae bloom."

Kangas and colleagues have been experimenting with algae scrubbers for several years now, testing them in the Susquehanna River, on the Eastern Shore and in Virginia.  The scrubber set up at Harbor Point is the same one he was using at Peach Bottom nuclear power plant two years ago when I wrote about his research. At that location, it was estimated the scrubber was able to remove 640 pounds of nitrogen and 90 pounds of phosphorus from the water.

The scrubber has been sloshing harbor water through since December.

"We've never done it in a spot like this before," Kangas said. He welcomed the chance to try it there because he hoped it might be able to impact water quality in a dead-end canal by the Living Classrooms campus on Caroline Street.  "Our intention was to to use this site to show we can overturn a 'dead zone,'" he said, referring to the condition where algae blooms rob the water of oxygen fish need to breathe.

"It's been a long time coming," said Peter May of Biohabitats, whose firm is also working with a scrubber using algae to remove nutrients from wastewater in New York.  Besides cleaning the water, he notes, there's the added value of the algae raised, which can be converted to organic fertilizer or even have its natural oils processed into fuel.  He displayed a small vial of clear "bio-butanol" refined from the New York algae. 

Now, though, it's not clear how long the harbor scrubber can stay where it is, as construction is to begin before long at Harbor Point on the new offices for Exelon, the energy company that acquired Constellation Energy.

Kangas says in any event, he's tired of testing and wants to scale up this "pilot" project soon to something large enough to have real impact on water quality.

Others are ready to try a bigger-scale experiment, too.  Scott Raymond of Living Classrooms suggested there might be room to install an acre-sized scrubbing facility along the reclaimed South Baltimore shoreline at Masonville.

"There's enough pollution that's goign to get into the Inner Harbor," Raymond said. "It's critical to have the technology to fight it."

Kangas and like-minded scientists think large-scale scrubbers - covering thousands of acres of land or water - could at least theoretically cure the Chesapeake's nutrient pollution.  But Kangas acknowledges that the ambitious engineering fix faces a major hurdle in the inability to find available waterfront on which to site such facilities.

Biohabitats' May has more modest ambitions, for now.

"We never want to say this is going to solve all of the problems," he said.  "It's one of the tools.'