Seawater Desalination Using Blue-Green Algae

Drinking water is in short supply around the world. Population growth, the salinisation of coastal regions and new demands such as hydrogen production are making it increasingly difficult to meet the rising needs of people, animals, agriculture and industry. In response, we are developing a new, environmentally friendly method of seawater desalination based on blue-green algae. 

Around 16,000 large-scale plants worldwide are currently working to convert seawater into drinking water. However, the processes used consume enormous amounts of energy and are therefore very expensive. They also produce a highly concentrated brine, which is often discharged back into the sea and, together with the chemicals involved, can cause severe environmental damage.

Instead of technical methods such as this, we rely on specific bacteria as tiny salt traps. These microscopic cyanobacteria of the genus Spirulina, also known as “blue-green algae”, are first cultivated in a very low-salt medium. When exposed to seawater, this comes as a shock to them. In response, they produce a mucus-like layer of carbohydrates to protect their cells, to which the salt binds and which can then be filtered out relatively easily. 

This is already proving effective in the laboratory. In this way, salt concentrations of 30 grams per litre, typical for North Sea water, can be reduced to drinkable levels of less than one gram per litre – and this with lower energy consumption and without problematic waste products. 

Together with the chemical company Kronos Titan, we are now testing the process on a larger scale. The company requires large volumes of filtered water from the River Weser to cool its facilities and is looking for a more sustainable alternative. In addition, waste heat and carbon dioxide are generated there, which we can harness for Spirulina production. 

At the same time, we are looking for ways to make use of the blue-green algae. They could potentially be deployed in the food, pharmaceutical or cosmetics industries, as livestock feed, or for coating seeds – which would make the process even more economically attractive.