An Israeli company said it has cleared the Roodeplaat Dam in South Africa of toxic cyanobacteria in the largest project of its kind ever successfully undertaken.
The bacteria, which is better-known as blue-green algae but technically isn’t an algae, plagues watercourses around the world. It secretes toxins to fight off competition for surface area and sunlight from green algae, killing other water life in the process. Besides abundant sunlight, the bacteria’s growth is boosted by the presence of sewage or fertilizer-rich agricultural run-off.
BlueGreen Water Technologies Ltd. killed the bacteria on the 4.3 square-kilometer (1.7 square-mile) Roodeplaat dam by coating it with a biodegradable polymer that floats on the water surface, said Eyal Harel, the chief executive officer and co-founder of the Tel Aviv-based company. Other methods for treating infestations utilize a greater volume of chemicals that often sink, making them less efficient and increase their environmental impact, he said.
Traditional methods “shock treat the entire water column, which is bad for large lakes and very expensive,” Harel said in an interview. “From an environmental point of view its catastrophic, and from an operational view it’s a nightmare.”
South Africa’s departments of environmental affairs and water didn’t immediately respond to queries about the project.
The technology used to clear the dam, which lies 22 kilometers (14 miles) north of South Africa’s capital, Pretoria, had worked very effectively, according to Sean Kerr, president of Rowing South Africa, whose members utilize the water body.
The bacteria’s absence has however encouraged the growth of water hyacinth, which now cover much of the dam — their spread having gone unchecked during a national lockdown that came into effect on March 27 to curb the coronavirus, Kerr said.
BlueGreen successfully treated the 1.3 square-kilometer Chippewa Lake in Ohio last year, and has done work in Russia and China, according to Harel.
The company is planning to treat a water-body twice the size of Roodeplaat in Florida this year, and has an even bigger project scheduled at Nanhu Lake in China’s Hunan Province. It’s also pitching for more work in South Africa, where as many as 700 water bodies may need treatment.