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Algae turns wastewater into resources

"What we see as waste can become a valuable resource that creates cleaner water and greener energy," says researcher.

Microalgae are very good at purifying water, but it is difficult to collect them after they have completed the purification job. Suvidha Gupta compares it to collecting dust from the air when it is windy.
Georg Mathisen
Presented by: NMBU, Norwegian University of Life Sciences
Published

"Our findings could revolutionise wastewater treatment. We transform wastewater into a valuable resource while reducing pollution," says Suvidha Gupta.

She researches what tiny algae – microalgae – can do with wastewater from a dairy. 

"When producing dairy products, the dairy also generates large amounts of wastewater. This can be harmful to the environment if not properly treated," she explains.

Microalgae in wastewater

The focus is on wastewater – the water used to clean production facilities. 

When machines and floors are washed, the water carries away milk residues and other remnants from production.

Suvidha Gupta in the laboratory at NMBU.

"We grow microalgae in this water. These tiny organisms are like superheroes. They can consume all the harmful substances and help us purify water naturally. At the same time, they grow and produce valuable sugars, fats, and proteins," says Gupta.

In scientific terms, this is called biomass – material derived from living plants or microorganisms.

Threads and clumps 

Microalgae are very efficient at purifying water, but it is difficult to collect them after they have completed their purification job. Suvidha Gupta compares it to gathering dust from the air on a windy day. 

Her solution is to combine two algae species. 

One is microalgae that grow in the water and purify it. The other is a species that also cleans wastewater but produces long, thin threads. 

These threads capture the small algae. Together, the two algae species form clumps heavy enough to sink to the bottom of the water.

"This process allows us to purify the water and produce valuable biomass without using expensive equipment or energy. We don’t need chemicals, large amounts of electricity, or heat, yet we can harvest the microalgae and turn them into green fuel and valuable products," she explains. 

The biomass can also be converted into biodiesel and biochemicals, which in turn can be used as raw materials for pharmaceuticals.

Created a 'magnet'

The researchers face another challenge: They need effective methods to extract valuable substances from the algae.

"We need to break open the algae to access the beneficial components inside, like sugars. These microalgae have very thick cell walls. You can compare them to the shell of a coconut, making it hard to access these ingredients," says Gupta.

She has developed a completely new tool: a multi-enzyme magnetic nanocatalyst. 

She describes it as small scissors that cut the algae into pieces and release sugars and fats. These scissors can be reused multiple times and remains effective for at least the first five uses.

Waste becomes a resource 

Sugars serve as food for bacteria that convert them into important chemicals, while the fats are turned into biodiesel. While these processes have been known for a long time, the method of transforming pollutants into raw materials is new. 

The quantities are small. It takes two litres of wastewater to extract one gram of microalgae. But at that point, the water is clean enough to be released directly into nature, and 55 per cent of the microalgae consist of sugars. 

These figures come from the work Gupta’ has done in the laboratory at the Norwegian University of Life Sciences (NMBU). In a real dairy, the composition of the wastewater varies from place to place and from day to day. 

"But above all, we have demonstrated that this is feasible. What we see as waste can become a valuable resource that creates cleaner water and greener energy," Gupta concludes.

Algae research

Algae are organisms that perform photosynthesis, like plants, and live in moist environments. Microalgae are so small that individual algae can only be seen under a microscope.

The research project AlgalBB aims to develop a cost-effective process to use microalgae to purify wastewater from dairies, then convert the algae into biofuels and valuable chemicals. 

Wastewater from the dairy sector is challenging and expensive to treat. Without treatment, it is harmful to the environment. Current biological treatment methods are energy-intensive, they often produce sludge that requires additional management and disposal, increasing environmental and economic challenges. 

AlgalBB is conducted at NMBU's Faculty of Science and Technology and is funded by the EU Horizon Europe programme. 

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