Although the water in Taihu is safe to drink once it has been processed, water experts said it has become prone to algal outbreaks in warm weather and is in serious danger if the level of pollution increases. Keeping the lake clean will be a long-term process.

A salesman in Dongshan, Jiangsu province, holds some super-large Taihu mitten crabs. The crabs can cost up to US$32 per kg. [Qi Zhenlin/China Daily]

The State Council, the nation's cabinet, recently released a general plan for comprehensively treating the Taihu basin, which was approved by Premier Wen Jiabao. It requires surrounding communities, such as those in Shanghai municipality and provinces of Jiangsu and Zhejiang, to submit detailed proposals for action.

The plan mapped out short- and long-term targets to ensure the quality of water and set 2012 as the target date to finally rid the lake of nutrients that lead to excessive algal growth.

By then, it states, the water quality should be improved from being "worse than Grade V", the highest level of poisoning and when the lake has no biological function, to Grade V, which means the lake water is able to be processed for agricultural irrigation.

By 2020, it adds, the water quality should be improved to Grade IV, when it is able to be processed for industrial use, or Grade III, when it can be processed for drinking, swimming or aquatic farming.

The Taihu basin, the core area of the Yangtze River Delta, is the country's richest region, with a high population density, as well as a high level of industrial development.

Wuxi alone has 1,500 people per sq km, 10 times more than the national average. About 60 percent of industrial ventures contribute to its gross domestic product (GDP) and the city has 10 plants per sq km, meaning its GDP per sq km is more than 57 million yuan, 57 times more than the national average.

The ecosystem of Taihu has borne the brunt of its fast economic development. But now the focus is on creating sustainable development, even if it slows the high rate of growth.

"The period since May 2007, when the blue-green algae outbreak hit Wuxi, has been the hardest time in my 20-year career," said Liu Yajun, director of Wuxi environmental protection bureau.

The authority had to move the intake point in Taihu by 3,000 m to the lake's center, where the water is less polluted, to ensure clean drinking supplies, while the city also started to take water from the Yangtze River.

It now receives 800,000 tons of water from both Taihu Lake and the Yangtze River every day, with every drop first undergoing 106 strict quality tests. It previously went through only 35 tests.

Wuxi has also implemented the most stringent waste treatment standards in China. It boasts 68 waste treatment plants and has updated more than 6,000 km of pipelines.

In addition to organic pollutants, levels of nitrogen and phosphate, the main causes of algal growth, have also been reduced, while real-time and online monitoring systems have been improved.

More than 1,400 small factories that consumed high levels of energy, or released a lot of pollution but produced little in the way of economic advantage, have already been closed down.

Neighboring cities have cooperated in a biological approach to the pollution, with more than 10,000 mu of wetlands recovered with the planting of reed marshes and a forest belt 200 m wide planted along the shore.

Water farms and floating restaurants have been permanently removed.

Meanwhile, the blue-green algae has been put to good use by the Wuxi authorities as a biomass for electricity generation and fertilizer for the young trees.

The Taihu basin has become almost a pilot experiment in introducing market instruments to reduce pollutants, such as cap and trade, paid emission rights and a biological compensation system.

Some measures, though, have aroused controversy, including the introduction of water from the Yangtze River to dilute the pollution, which experts claimed could transfer pollution into the Yangtze.

Plans to dump silt dredged from the lake was also heavily criticized as environmentalists said it would lead to soil pollution.

"It's impossible to get everything right," said bureau chief Liu. "The priority is to ensure an adequate supply of clean drinking water and prevent an outbreak of poisonous algae."

Given the size of the task, cutting a few mitten crabs from the menu is not such a big sacrifice.

(China Daily July 17, 2009)