Desalination tech helps slake nation's thirst for fresh water

China made remarkable progress in seawater desalination in recent years through the use of membrane technology, said Xu Nanping of the Chinese Academy of Engineering.

The new technology stands out from traditional methods, such as extraction and evaporation due to its lower energy consumption and higher purification rate, Xu said.

"And it has become an effective way to deal with the water shortage in China," he added.

He noted that "China's water shortfall will reach 400 billion tons in 2050. The resulting loss in manufacturing will reach about 200 billion yuan ($32 billion) and in agriculture 150 billion yuan."

The membrane technology, which is now used in 80 percent of the seawater purification projects in the country, will not only bring down treatment costs but also greatly increase fresh water supplies to meet huge demand in coastal regions, Xu said.

China National Bluestar (Group) Co Ltd has a number of seawater desalination projects on China's eastern coast, notably in Zhejiang province, using membrane technology developed by its Hangzhou Water Treatment Technology Center.

Bluestar is a subsidiary of the China National Chemical Corp, a Fortune 500 company, which is engaged in a wide range of business, such as new chemical materials, oil processing and agrochemicals.

Using the center's advanced reverse-osmosis membrane method, a seawater desalination project is now operational on Zhejiang's Liuheng Island.

Its existing first phase can provide about 20,000 tons of fresh water a day, freeing locals from reliance on supplies from the larger Zhoushan Island.

The local government is cooperating with Bluestar to build another three phases with total capacity of 80,000 tons a day to supply Liuheng and neighboring islands.

Gao Congjie, an academic of the Chinese Academy of Engineering and researcher at Bluestar's Hangzhou Water Treatment Technology Center, also praised the new technology.

He said "China has been desalinating seawater for 60 years, but it is only in the past 10 years that breakthroughs have been made with membrane technology".

"The membrane resembles a sieve with super-fine pores that allows water molecules to pass but keeps bigger-molecule salts and impurities," Gao explained.

He noted that the current cost of seawater desalination using the technology is 4 to 5 yuan per ton, a price already acceptable to business users. The number of household users is expected to grow due to foreseeable cost savings and government subsidies.

You Jinde, secretary-general of the China Membrane Industry Association, said "we're now able to treat 660,000 tons of seawater a day with the membrane technology, and the process has gained ground in Zhejiang, Liaoning and Tianjin".

Tianjin now has 6,000 tons of desalinated seawater piped to the public every day, a figure that is expected to rise.

You said "Beijing is also considering using desalinated water from Caofeidian in Hebei province".

Government support

Seawater desalination is also gaining strong support from the central government, according to Yang Shangbao, an official with the National Development and Reform Commission.

An NDCR estimate said that China's seawater desalination capacity will be between 2.2 and 2.6 million tons a day by 2015, or three to four times the current figure. Revenues in the industry are projected to hit 10 billion yuan by that time.

But You of the China Membrane Industry Association noted the challenges ahead.

"The price gap between desalinated water and tap water and the pollution from the desalination process are pressing concerns of the government and the industry," he said.

Mark Irwin, chief operating officer of China National Bluestar Co, suggested that condensed saline water from the process can be recycled to produce soda ash.

You called for government subsidies for both desalination plants and users to make the new water resource affordable for businesses and households.

Use of membrane technology is a trend in global desalination industry, Corrado Sommariva, president of the International Desalination Association, said at an international forum last month in Beijing.

"Seawater desalination has become an important approach to getting fresh water, and 80 percent of such projects in the world are membrane based," he said.

yangfeiyue@chinadaily.com.cn