Ozone nanobubbler deployed to clear Lincoln Memorial Reflecting Pool
A $1.7 million ozone nanobubbler is being used after algae turned the Lincoln Memorial Reflecting Pool green within days of a costly renovation.
A $1.7 million ozone nanobubbler was being used to rescue the Lincoln Memorial Reflecting Pool after a June renovation left the iconic basin green within days, raising new scrutiny over a costly fix at one of the National Mall’s most visible landmarks.
The Reflecting Pool was not completed in time for the Lincoln Memorial’s dedication on May 30, 1922, but it became one of Washington’s most recognizable and filmed sites. Designed as part of the memorial landscape by Henry Bacon and Frederick Law Olmsted, Jr., it sits on the east-west axis between the Lincoln Memorial and the Washington Monument, and it served as a route for more than 200,000 people who marched to the Lincoln Memorial steps on Aug. 28, 1963.
The pool was refilled with about 6.5 million gallons of water across more than 300,000 square feet, then developed an algae bloom within days of the renovation. The project cost about $14 million; another estimate put the cost at more than $15 million. The Trump administration tied the work to the nation’s 250th anniversary celebrations, wanted the water to be “American Flag Blue,” and set a self-imposed July 4, 2026 deadline.
Hydrogen peroxide and nanobubble ozone technology were being used to treat the bloom. The nanobubbles were meant to kill algae, pathogens such as E. coli, and contaminants, while the algae was “residual” from reactivated supply lines. U.S. Park Police and National Guard members were patrolling the site, and National Park Service crews were vacuuming dead algae from the bottom of the pool.
The blue liner or coating at the bottom of the pool appeared to be peeling in sections, adding another maintenance issue to the algae problem. By the afternoon of June 16, the water near the Lincoln Memorial had turned blue-gray while the east side near the World War II Memorial remained bright green.
Brooks Barrett, a Smithsonian marine biologist, said there was “no quick fix” and described the reflecting pool as an ideal environment for algae because it is warm and stagnant.
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