The water quality of Taihu Lake, the country's third-largest freshwater lake, has been greatly improved due to the introduction of sewage disposal facilities in rural areas, environmental protection authorities said.

Since 2007, the Jiangsu provincial government has installed more than 3,580 facilities, many using technology from countries such as Germany and the United States, in villages around the lake.

"About 500,000 families have benefited," said Liu Zhaoyang, an engineer at the General Office of Taihu Lake Water Pollution Prevention and Control. "The facilities have also reduced discharges into the lake."

Li Jinfu, a farmer on Lianhua Island in Suzhou, Jiangsu province, used to pour sewage directly into the lake.

"Now a disposal system using German technology collects the sewage from 39 families on the island, and the water flows into the lake after treatment," he said.

Xia Jian, deputy director of Suzhou's water resources bureau, said the sewage flows into an underground equalizing tank before it is used to water bulrushes and canna lilies planted with chemicals that can purify the pollutants.

"The water purified by the centralized treatment of sewage can reach the highest and best level of the country's water quality standard," he said. "It is finally discharged into Yangcheng Lake, one of the 180 smaller lakes and rivers in the Taihu Lake area, which is noted for its excellent water quality and delicious crabs."

Water pollution in Taihu Lake has aroused the concern of authorities since 2007, when serious blue-green algae outbreaks led to the contamination of drinking water for millions of residents in lakeside Wuxi city.

Located in one of the country's most densely populated regions, the lake provides drinking water to about 30 million people in nine cities in Jiangsu and Zhejiang provinces and Shanghai, according to the general office.

Apart from using biological and chemical treatment for wastewater, authorities have also taken a host of other measures ― including closing small chemical and papermaking mills and eliminating livestock and poultry farms ― to control pollution.

"More than 4,100 chemical plants along the shore of Taihu Lake have been shut down, as well as 1,800 livestock and poultry farms," said Zhu Tiejun, director of the General Office of Taihu Lake Water Pollution Prevention and Control.

He said by the end of this year, 63 percent of wastewater in the lake basin will be purified.

"The excessive richness of nutrients in the lake has been preliminarily controlled," Zhu said.

More than 75 billion yuan ($12 billion) has been invested in 3,000 programs to treat pollution in the last five years. The provincial government will allocate 2 billion yuan a year to control and eradicate water pollution in Taihu Lake, he added.

Contact the writers at cangwei@chinadaily.com.cn and songwenwei@chinadaily.com.cn