By Tracey Regan, New Jersey Institute of Technology
Amid summer’s cornucopia, there is one proliferation that is universally dreaded: the toxic algae blooms that float on lakes and streams, killing fish, gobbling oxygen from the water and chasing away swimmers. Composed of tiny organisms such as single-cell phytoplankton, macroalgae and cyanobacteria, the phosphorescent blue-green clusters are impossible to miss, but difficult to capture.
“Compared to weeds and other aquatic plants, microalgae are tiny – between 1 and 10 micrometers in width – and so there is no easy way to remove them mechanically,” explains Wen Zhang, director of NJIT’s Sustainable Environmental Nanotechnology and Nanointerfaces Laboratory, who is working with a team of biologists, engineers and entrepreneurs on a new plan of attack.
Last summer, the team launched a custom-designed boat on New Jersey’s Deal Lake that scooped up algae-laden water for treatment on board. Central to the technology is a device that injects nano- and microbubbles of air into the lake, lifting algae from as deep as four feet to the surface for collection by skimmers.
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Researchers have discovered that tiny bubbles have a host of useful properties. Suspended in liquids, they have a high degree of stability against dissolution and collapse. Their high surface area and their random movements allow them to move materials around, including nutrients to enhance plant growth, ozone used in bacteria disinfection and oxygen needed to aerate hypoxic environments.
“Bubbles that are 100-500 micrometers in diameter rise quickly to the surface, and because they’re negatively charged and adhesive, lift the clinging algae,” Zhang said. “We’re also hoping to use this technology to raise dissolved oxygen levels. We’ve found that even finer bubbles, between 100-300 nanometers in diameter, stay suspended in the water much longer, where they slowly collapse and dissolve, boosting oxygen levels for up to five days. This is much better than standard aeration. They also remediate anaerobic processes that produce smelly odors and blackish water.”
Zhang’s team, which is funded by the New Jersey Department of Environmental Protection, is working with the Meadowlands Research and Restoration Institute (MRRI) and BRISEA Inc., an environmental and energy services company, to demonstrate their prototype’s effectiveness in clearing algae. They are also developing a long-term strategy to monitor other water quality parameters, such as dissolved oxygen and turbidity, on state lakes.
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