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Plant-based alternative for harmful algal bloom mitigation discovered

A research team at Clarkson University recently published a study about a plant-based alternative to traditional chemical methods of combating Harmful Algal Blooms (HABs).

, published by Clarkson University chemical engineering graduate students Temitope Orimolade and Ngoc-Tram Le, along with undergraduate student Lyle Trimble, has been featured on the cover of the journal, Soft Matter.

The team's research focuses on using Moringa oleifera to combat the cyanobacterium that causes HABs—known as Microcystis aeruginosa—and comparing it to the traditional chemical method of using aluminum salts.

HABs caused by cyanobacteria (blue-green algae) exhibit enormous threats to human health, animals, and aquatic ecosystems.

Microcystis aeruginosa cells—the cyanobacterium that causes HABs—contain a family of potent toxins known as microcystins, which can cause negative health effects in humans, from mild skin rashes to serious illnesses. They can also cause severe liver damage and even death in dogs and livestock. Any method used to treat harmful algal blooms must ensure that the cells remain intact to prevent the release of these toxins into the aquatic environment.

According to Clarkson University Professor of Chemical & Biomolecular Engineering Sitaraman Krishnan, who oversees the research team, the seeds of Moringa oleifera contain proteins that act as natural flocculants. Flocculant is the substance that causes particles in liquid to clump together, and the clumped particles are called flocs.

Aluminum salts, such as alum (potassium aluminum sulfate) and polyaluminum chloride, are commonly used as flocculants in water treatment processes. They effectively aggregate particles, facilitating their removal from water. However, their use raises environmental concerns, particularly regarding the formation of toxic sludge. This sludge can contain soluble aluminum compounds, which may leach into water bodies, posing risks to aquatic life and potentially entering the food chain.

In contrast, Moringa oleifera offers a biodegradable, plant-based alternative that is less polluting. Its use as a flocculant reduces the risk of toxic sludge formation and minimizes environmental impact.

"While we have not yet evaluated the toxicity of Moringa extracts to aquatic organisms, we expect them to be safe for the environment, especially considering that the plant is widely consumed as food in various parts of Asia and Africa," Krishnan said.

A few studies, which are reviewed in the article written by Clarkson's researchers, have previously highlighted the potential of Moringa seed extracts in flocculating Microcystis aeruginosa. However, knowledge gaps remained regarding the required flocculant dosing in comparison to alum, as well as the structure and strength of the flocs formed.

"In our study, we identified some intriguing differences between alum and Moringa oleifera in terms of how the floc structure evolves with increasing floc size," Krishnan said. "The behaviors observed were notably distinct, providing new insights into the comparative effectiveness of these flocculants."