On Air
0:00
0:00
Open In Popup
MPR News

A new old way to combat toxic algae: Float them up, then skim them off

Share story

In Florida's Lake Okeechobee, huge blooms of blue-green algae have become an annual occurrence. The Army Corps of Engineers is testing methods based on wastewater treatment to remove the green slime, which can produce toxins that threaten drinking water supplies, local economies and human health.
In Florida's Lake Okeechobee, huge blooms of blue-green algae have become an annual occurrence. The Army Corps of Engineers is testing methods based on wastewater treatment to remove the green slime, which can produce toxins that threaten drinking water supplies, local economies and human health.
Wilfredo Lee | AP

In Florida, the Army Corps of Engineers is working to combat a growing environmental menace: blue-green algae. Nitrogen and phosphorus runoff from farms and subdivisions combines with warm summer weather to create massive blooms of algae in rivers and lakes that can be toxic.

In central Florida, Lake Okeechobee has been hit hard in recent years. In Moore Haven, on the western shore of the lake, Dan Levy was recently working on a solution. He was standing on a platform peering into a large water-filled tank. Inside, floating on top of the water was a thick mat of blue-green algae. "This is our treatment system," said Levy. "This is where we actually float the algae up and skim it across."

Levy is with AECOM, an engineering and infrastructure company that's working with the Army Corps of Engineers on the nagging and sometimes devastating problem. Algal blooms aren't just a nuisance. The algae, actually cyanobacteria, can produce toxins that threaten drinking water supplies, local economies and human health.

Levy says the technology being tested at Lake Okeechobee has long been used at water treatment plants and wastewater facilities. "We have applied it to use in this particular manner to harvest algae," he says. "It's a new use of a proven process." The process is called "dissolved air flotation." David Pinelli, also with AECOM, says, "We attach billions and billions of microscopic air bubbles to the solids. It imparts buoyancy to the solids, and those solids float to the surface. When they float to the surface, we can skim them off."

Algal blooms can be huge. One in Lake Okeechobee last year covered half the lake, more than 300 square miles. The system under development by AECOM can clean as much as 100 million gallons a day.

For the Army Corps of Engineers, which manages Lake Okeechobee, algae removal is something new. Linda Nelson, of the Corps' research branch, says the federal agency received funding last year from Congress to tackle a problem it's seeing not just in Florida but in Oregon, Oklahoma, Texas and other areas across the United States. "We're trying to make scalable solutions to the problem," she says. "But we're also trying to make sure they're technologies that can be applied elsewhere. It's not just a South Florida problem. It's a problem nationwide."

Last year, algae from a massive bloom in Lake Okeechobee flowed down waterways to Florida's east and Gulf coasts, forcing beach closures and hurting local businesses. Something similar happened this year in Mississippi because of a bloom caused by floodwaters released into the Gulf of Mexico.

To make it sustainable over the long term, the Army Corps of Engineers is looking at possible uses for the tons of algae removed from the lake, including converting the algae into biofuel or using the algae in consumer products like yoga mats or sneakers.

Martin Page, with the Army Corps of Engineers' Engineer Research and Development Center, says the ultimate goal is to develop a process that's portable and can be deployed quickly. "If there's any community in the country where there's a harmful algal bloom upstream, developing some tools to help them mitigate the impacts on some downstream communities is what we're shooting for," says Page.

On a body of water like Lake Okeechobee, that might mean placing large algae-skimming systems on rivers flowing out of the lake, protecting coastal communities from seeing their beaches covered with a thick green slime.  

Copyright 2019 NPR. To see more, visit https://www.npr.org.