Quick, cheap method for algae removal
Lake Taihu provides drinking water to more than 33 million people, but from June through November it can be choked with algae blooms at concentrations as high as a billion cells per liter (Technology News, 2006).
Researchers in China have demonstrated that a new technology can remove 99% of toxic cyanobacteria from polluted lakes in a matter of hours. A simple and inexpensive new technology for quickly removing algae from freshwater could aid communities dealing with algae-clogged lakes, according to Gang Pan and his colleagues from the Chinese Academy of Sciences. They have demonstrated that these bacteria are particularly well suited for emergency removal of toxic cyanobacteria but also may provide a long-term strategy for permanently remediating algae-clogged lakes and restoring their ecology.
The new approach mixes local sediments and clays with chitosan (a cheap, nontoxic compound made from the hard exoskeletons (chitin) of shellfish such as lobsters) to grab hold of the algae via flocculation and drag the unwanted plants to the bottom of the lake. In a test of the method at Lake Taihu in eastern China, spraying low levels (25 milligrams per liter) of 10% chitosan-modified local soils into a test enclosure removed 99% of the algal cells within 16 hours. A month later, the algae had not returned. Local mussels and indicator aquatic plants (macrophytes) were unaffected by the process. A downside of the approach is that it could release phosphate into the water as the algae cells decompose, but the scientists say that they are developing a new method that permanently fixes this nutrient into the sediment.
Researchers in China have demonstrated that a new technology can remove 99% of toxic cyanobacteria from polluted lakes in a matter of hours. A simple and inexpensive new technology for quickly removing algae from freshwater could aid communities dealing with algae-clogged lakes, according to Gang Pan and his colleagues from the Chinese Academy of Sciences. They have demonstrated that these bacteria are particularly well suited for emergency removal of toxic cyanobacteria but also may provide a long-term strategy for permanently remediating algae-clogged lakes and restoring their ecology.
The new approach mixes local sediments and clays with chitosan (a cheap, nontoxic compound made from the hard exoskeletons (chitin) of shellfish such as lobsters) to grab hold of the algae via flocculation and drag the unwanted plants to the bottom of the lake. In a test of the method at Lake Taihu in eastern China, spraying low levels (25 milligrams per liter) of 10% chitosan-modified local soils into a test enclosure removed 99% of the algal cells within 16 hours. A month later, the algae had not returned. Local mussels and indicator aquatic plants (macrophytes) were unaffected by the process. A downside of the approach is that it could release phosphate into the water as the algae cells decompose, but the scientists say that they are developing a new method that permanently fixes this nutrient into the sediment.