Science - April 19, 2016

Using algae to purify Gambian water

Didi de Vries

A group of Dutch high school students have designed a water purification system that uses algae to obtain drinking water and nutrients from Gambian river water. Also collaborating on the project were Wageningen researchers Ben van den Broeck and Dorinde Kleinegris of Food & Biobased Research.

It has gone well: on 21 April Bram Klein Wentink, Carmen Swiers, Lisanne Peters and Tessa Mennink of the Ludgercollege in Doetinchem will compete in the final round of Imagine, a competition for high school graduation projects.

Gambia’s hot climate plays a major role in the water purification system. In the first of four tanks, sunlight heats river water to at least 60 degrees, killing micro-organisms. The second tank contains Chlorella, an alga which filters those heavy metals out of the water. In the third tank grows edible Spirulina algae, absorbing nutrients from the water. The alga is not particularly tasty, in Bram’s opinion.

‘Spirulina stinks of fish food and grass. Luckily you only need about 3 grams of it per day.’ The last stage is distillation, with sunlight causing the water to evaporate, after which the steam is cooled and captured for use as drinking water.

The high school students tested the growth of the algae, using water from the Oude Ijssel. ‘In the Gambia people use the river as a toilet,’ says Bram. ‘To obtain comparable water we added our own urine to the tubs of river water.’ They also added Chlorella and Spirulina. In the Wageningen laboratory they measured the pH of the water and examined the algae under the microscope. ‘It was very nice to see a real lab and talk to researchers,’ says Bram. ‘We learned that it’s not just money that enables you to solve problems in developing countries, but good ideas too.’

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