Park Service continues to battle algae in renovated Reflecting Pool

Interior Department says it's using nanobubble technology to break up the green.

The National Park Service continued a push Tuesday to eradicate algae from the Lincoln Memorial Reflecting Pool as tourists and locals gathered to view the green-tinged water.

The Department of Interior has deployed both a hydrogen peroxide treatment and nanobubble ozone technology, a DOI spokesperson said, to rid the pool of algae blooms that have discolored the landmark and marred the rollout of President Donald Trump's renovation project.

Algae bloomed late last week just days after the completion of the renovation, turning the pool from deep blue to green and murky. A DOI spokesperson told CNN in a statement that the algae was "residual" and came from reactivated supply lines.

Workers were spotted dumping hydrogen peroxide into the pool Tuesday morning in videos posted to X.

The nanobubble ozone technology is "actively killing algae" and other contaminants, the spokesperson wrote. The nanobubble process releases tiny gas bubbles filled with ozone into the water, which helps to eliminate algae blooms.

Rangers from the National Park Service were also in place midday Tuesday to continue scraping algae off the bottom of the pool. A tubing system was set up in an apparent effort to siphon contaminated water out of the pool and into storm drains.

The DOI spokesperson wrote that the hydrogen peroxide would have "no harmful side effects to marine life or to the environment."

The water was noticeably cloudy, one Park Service ranger said, due to stirred-up algae that had not yet been extracted from the pool.

White House spokeswoman Taylor Rogers told ABC News on Tuesday, "under regular NPS maintenance, a high-tech nanobubble ozone technology will be deployed to kill the algae and keep the Reflecting Pool crystal clear."

Trump has touted the pool renovation in public and on social media. He said in May that the landmark was "going to have the great color," claimed the pool was "filthy" and "dirty" before the updates and criticized his predecessors for failed renovation attempts.

But the plan -- originally an expedited effort to resurface the pool and revamp its filtration in advance of America's 250th birthday -- ballooned into a nearly $15 million endeavor, federal contract records show, and a public headache for the administration.

Employees from Greenwater Services -- an Ohio-based organization that specializes in water purification and the nanobubble technology -- were on site Tuesday and were seen filling plastic water bottles with samples from the pool.

Federal records show the government paid Greenwater $1.7 million in April to install new filtration technology for the Reflecting Pool.

Greenwater directed ABC News to the DOI in response to a request for comment.

Algae has long plagued the 1920s construction -- a broad, shallow pool in which it and Cyanobacteria easily proliferate, especially during warm summer months. Former President Barack Obama made his own attempt at renovations in 2012 when he paid $35 million to construct a plumbing system that pulls water from the Tidal Basin and purifies it in a treatment plant.

Longtime Washington resident Redmond Walsh was biking by the pool on Tuesday and spoke to ABC News. He said he first inspected the pool on Sunday and posted a video of the green algae to X, where it now has 2 million views along with many detractors who claimed that he posted outdated material from 2012.

Walsh was back on Monday and Tuesday to check in on the progress. He said he would post an update to his followers saying that the pool was "getting a little better."

Tourists said they weren't surprised that the algae returned after the renovation.

David Janes, an engineer visiting from Louisville, Kentucky, said he thought the government was "back to square one" and is "going to have to do it all over again."

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