Blue-green algae appeared again in the lake in Wuxi, Jiangsu, last year. SONG RONGCHENG FOR CHINA DAILY

The Suzhou Office of Taihu Lake Water Pollution Prevention and Control said experiments have been carried out in about 350 hectares of water near the city to control the growth of aquatic plants and identify a suitable mix of different types.

Physically removing the algae from the lake has also proved an effective way of reducing pollution, according to the Wuxi government, which has removed 6.72 million tons since 2007, equal to the removal of 1,794 tons of nitrogen and 450 tons of phosphorus.

Last year, the pollution office investigated 223 lakeside businesses and closed 59 of them for failing to treat wastewater properly.

Since 2007, the provincial government has allocated 2 billion yuan annually to manage water pollution in the lake. By the end of 2013, it had invested more than 106 billion yuan to set up 1,450 projects to deal with the heavily polluted water.

Wuxi has also partnered with other lakeside cities, including Suzhou and Changzhou, to implement pollution-control measures.

Yixing, a county-level city under the jurisdiction of Wuxi, has invested more than 5 billion yuan to establish a sewage collection and disposal system, plus a garbage-treatment system that serves the whole city. It has also closed about 600 chemical factories and related businesses as well as more than 400 glazed-tile enterprises that were thought to have adversely affected the local environment.

Despite these achievements, pollution remains a major problem. "The industrial wastewater and sewage discharged into the lake, although treated, often fails to meet the national standards," Zhu Tiejun, director of the general office, said.