Scientists Effectively Eliminate Algal Blooms in Taihu Lake Using Reproductive Control Technology Without Chemicals.
Taihu Lake – the third largest freshwater lake in China, spans 2,250 km2 across Jiangsu and Zhejiang provinces, two of the most populous and prosperous regions in eastern China. For decades, this lake has been plagued by rampant blooms of cyanobacteria caused by wastewater discharge from nearby cities, factories, and farms.
Algae covering Taihu Lake in China. (Photo: Reuters)
However, a special type of boat developed by Cong Haibing, a professor at the School of Science and Engineering at Yangzhou University, can reduce the density of floating algae in Taihu Lake by over 80%, as reported by the South China Morning Post on August 21. The drone-guided boat approaches a cluster of algae as soon as they appear on the lake’s surface and employs a “reproductive control” technique without the use of drugs or chemicals.
According to Cong, cyanobacteria have evolved a small gas bag in their bodies that helps them float and access sunlight for growth and reproduction. The boat is equipped with devices that disrupt these gas bags, causing the cyanobacteria to sink to the bottom of the lake and die. The algae do not die immediately but will wither in the darkness underwater.
In research published in the journal Environmental Science and Technology, Cong and colleagues from the Wuxi Cyanobacteria Control Agency likened the new method to China’s family planning program. Experiments conducted this summer have demonstrated the technology’s effectiveness, and the program of “reproductive control” in Taihu Lake has officially launched.
Cyanobacteria are among the oldest forms of life on Earth, existing for 3.5 billion years. They can consume almost anything containing nitrogen and phosphorus. Due to human influence, their preferred food sources now include urban wastewater, industrial pollutants, and agricultural fertilizers. Algal blooms caused by cyanobacteria are rampant in both developed and developing countries worldwide. Hot weather exacerbates these blooms, which can reduce oxygen levels in water and produce harmful toxins detrimental to both animals and humans.
Current methods for dealing with algal blooms include manual removal or chemical poisoning, but these processes are costly, potentially harmful to the environment, and often ineffective. The main difference between the new technology and previous algal bloom control methods is that the pressure used to disrupt the gas bags does not kill the organism. After losing their gas bags, the algae can continue to live for several days at the bottom of the lake, but their reproduction rate slows significantly to about 1% of normal because they cannot gather enough energy from sunlight for photosynthesis.
“This method could be called a ‘family planning’ for cyanobacteria,” Cong shared. “Implementing family planning in the early stages of algal growth can prevent blooms, proving to be effective while requiring less effort.”
Cong’s boat uses two large water tanks to process the algae. Water from the lake is pumped into the tank using a small 500-watt pump before the water pressure is increased to burst the gas bags of the algae. The boat operates at a low cost, consuming only 0.005 kilowatt-hours of electricity to process one cubic meter of water containing cyanobacteria.
