Nieuws - 19 maart 2009


You can get rid of blue-green algae using an extract from the seeds of the tropical ‘miracle tree’ Moringa oleifera. This was discovered by high school students in Eindhoven. Wageningen UR’s blue-green algae team are now researching this new way of making life difficult for the algae.

Blue-green algae
To give honour where it’s due: the idea of using the miracle tree against blue-green algae came from high school students. Four boys and five girls from Eindhoven developed the idea for the First Lego League, an international technology competition. The task was to tackle a climate-related problem, and the growing problem of cyanobacteria (or blue-green algae) caught the student’s attention. One thing led to another and they came across the water-purifying qualities of Moringa oleifera seeds, and wondered whether the seeds would also have an impact on the blue-green algae which affect stagnant warm water in the Netherlands in the autumn. Dr. Miquel Lurling of the Aquatic ecology chair group was called in to test the idea. And this had never been done before, Lurling discovered when he looked through the literature. ‘It was known that there was an antimicrobial effect’, says Lurling, ‘and in several developing countries the seeds are used as a natural flocking device for purifying drinking water. But no one has researched whether the seeds also kill the cyanobacteria.’ And Lurling quickly found out that they do. ‘We got hold of some seeds and tested their effect on common blue-green algae. It works, that much is clear.’
But how it works, exactly, and what the active substance is, is still not known. Research is now going on. The Ethiopian Masters student Getahun Tolla heard about the experiments and was immediately enthusiastic, says Lurling. He imported seeds, roots and leaves from the tree from his country, and went to work to test how long the extract from the seeds worked and to try to isolate the active substance. But Lurling doesn’t think that a miracle cure for blue-green algae has now been discovered. ‘You need rather large amounts. But on a small scale in the tropics it should work well. De Moringa is common in the tropics and is drought-resistant.’ Still, it only tackles the symptoms, Lurling thinks. The Wageningen research focuses primarily on tackling the root of the algae problem by ‘dephosphating’ the water. Lurling’s group uses the ‘flock & lock’ method for this: phosphates are driven to the bottom of the water by a method known as flocking, and the bottom is then covered (locked) using modified clay so that the phosphate cannot escape again. Lurling says good results are obtained with this method.