By Han Ji, Gao Lin and Guo Juan

Not long ago, the biggest seawater desalination factory in Asia started construction in Dagang District, Tianjing City. It is introduced that the handling capacity of the project per day after being finished can reach up to 150,000 tons, and the tension of water supply will be greatly appeased.

According to statistics, there are 1.4 billion people in the world that are in short of safe and clean drinking water, and every one out of five people are lack of water; water crisis is becoming a global topic. China is regarded by the UN as one of the thirteen water-deficient countries in the world: there are 300 cities suffering from water shortage, among which 110 cities are extremely lack of water, mainly located in North China, North East China, North West China and coastal regions. The severe shortage of water resources has become an important factor that restricts the economic and social development of China, especially the coastal regions.
 
Today, developing the seawater (including brackish water) desalination technology has become a consensus of all the countries in the world to solve the water crisis. China has a long coastline of 32,647 kilometers; and the coastal regions and the central and western regions also boast abundant ground brackish water resources. Under the circumstance that drawing ground water and transferring water across regions are restricted by more and more conditions, developing and exploiting seawater and brackish water resources and practicing seawater desalination have become an effective and important strategic approach to relieve the tension of fresh water deficiency in China.

Compared with trans-regional water transfer, seawater desalination enjoys obvious advantages. Trans-regional water transfer involves project investment, operation fees, management fees, and losses like evaporation, seepage, river closure and pollution, as well as the occupation of large amount of lands; moreover, along with the advancement of technology and the expansion of the handling capacity per day, the cost of sea water desalination has been reducing continuously. Consequently, the cost of seawater desalination will be lower than that of water transfer.   

Moreover, water transfer is also influenced by the water capacity of the supplying region. Once the water source areas suffer from low water, the regions introducing water will become very passive. While sea water desalination, is not influenced by time, space and climate and also is of good water quality and stable water supply.

At present, distillation and reverse osmosis are the two most used ways in the world for desalination. There have been over 13,000 sea water desalination factories in the world with a production capacity of 35 million cubic meter fresh water per day, 80 percent of which is used for drinking. This has solved the water supply problem for over 100 million people.

The research of engineering technology of seawater desalination in China was started in 1958, and a set of mid-and-small sized projects have been implemented in recent 50 years. Up to now, there have been more than 20 sea water desalination projects, among which Shandong Huangdao Power Plant, Hebei Huanghua Power Plant, the No.7 Petroleum Factory of China Petroleum Dalian Petrochemical Corporation, Tianjin Economic-technological Development Area, Shandong Yantai City and Hebei Wangtan Power Plant are relatively large-scale sea water desalination enterprises that have put into production and will put into production; the accumulative production capacity of these projects have reached around 30,000 tons per day now.

Zhao Liang, researcher of The Institute of Sea Water Desalination and Multipurpose Utilization, SOA (Tianjin), introduced that China has a huge potential to develop sea water desalination; industry is getting increasingly matured after 40 years of key technology study; the output of constructed projects is around 31,000 cubic meters per day, and the output of the projects under construction and to be constructed is around 381,000 cubic meters per day. Take Tianjin Dagang Power Plant for instance, it has altogether utilized 27 billion cubic meters sea water in the past 10 more years; the desalinated seawater can not only satisfy the demand of industrial water supply, but can also meet the living water standard.

However, the development of seawater desalination technology hasn't led to the general application of the technology. Liu Zirong, director of Institute of Marine Development Strategy, SOA, attributed the reason to "over-high cost and investment cost". In China, besides technological reasons, seawater desalination needs policy support more urgently to solve the problem of over-high cost and investment cost.

At present, the supply of running water in China still employs planned economic system. Running water companies have mainly operated in the pattern of relying on public subsidies. The price of running water is relatively low, about 1.5 to 2 Yuan per cubic meter; as a result, financial departments are loaded with heavy burdens since the price of running water deviates severely from its value. Comparatively, the sea water desalination accounts everything including water drawing, equipments, production, operation and management into its cost in a marketized way, and the current price of desalinated water is between 4.5 to 8 Yuan per cubic meter. The price of desalinated water doesn't enjoy advantages compared with that of running water; as a result, the market gives cold responses to the new technology of sea water desalination.

As the fresh water resources getting more and more deficient, the government pointed out that the leverage role of price should be utilized, reasonable water price forming mechanism should be built up, and water price should be increased appropriately. Subsequently, many cities successively issued their own water saving measures, and carried out the limitation of running water use and charged extra fees for over-consumption. On the other hand, the advancement of sea water desalination technology has provided robust support to the reduction of sea water desalination cost. At present, the cost of sea water desalination in China has been reduced to 4 to 7 Yuan per cubic meter, and that of brackish water desalination to 2 to 4 Yuan per cubic meter.

In China, hundreds of billions Yuan of economic losses caused by water shortage every year appeals that the industrialization base of China's sea water desalination must be completed as soon as possible.

In addition, the welcome news is that China's sea water desalination equipment enjoys relatively strong international competitiveness due to its perfect technology and relatively low price. Ruan Guoling, Director of The Institute of Sea Water Desalination and Multipurpose Utilization, SOA (Tianjin), introduced that the price of China's technological equipment is about 50 percent lower than that of foreign equipment, enjoying obvious advantages with promising market prospect.

[Photo: Google]