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Seawater Desaliation Urgently Needed to Develop

Yuan Li

China has a coastline of more than 18,000 km long. Apart from its land area of 9.60 million sq.km., China boasts a seawater area of about 3 million sq.km, ranking as one of the large maritime states in the world.

Other coastal countries, like China, are facing a crisis of fresh water. But since the start of the 1990s, some of them have bent their eyes upon the ocean.

China is one of those countries that have controlled the technology of desalinizing seawater. However, the actual situation is that many coastal cities in the country are still sparing no effort to draw water from underground while anxiously introducing a policy of restriction on water consumption in the cities.

It is no wonder that Wang Shuguang, director of the State Oceanic Administration, stressed once more the social significance of seawater desalination at the working conference held on September 2 this year.

“We have to pay attention to the advantage of coastal cities in drought resistance. But they have not yet been conscious of it. Scanty water supply is still a problem in these cities. They are still draining the resources of water on the ground together with the inland cities close to them. As a result, the coastal cities also put on rations for water supply this year just as the inland cities do, he said.

According to a group of statistics adopted by the United Nations, the average volume of water per capita in China ranks the 109th in the world, though China’s total capacity of water resource ranks the sixth.

“In China, there are 10 provinces, municipalities and autonomous regions whose water resources are estimated below the benchmark of existence. In these areas, the average volume of water resource per head is less than 1000 cubic meters,” he continued. So China is listed as one of the 13 countries with scanty water resources in the world by the United Nations.

Meanwhile, the Ministry of Water Resources points out, in its “report on the program for water supply sources for those main cities in shortage of water,” that about 300 cities across the country are in shortage of water, 110 of which, widely distributed in north, northeast, northwest China and the coastal area, are in serious shortage of water. The report also notes that after the year 2010, China will enter a stage of serious shortage of water. By 2030, the volume of water in shortage will reach 40-50 billion cubic meters and a peak of shortage of water will be close at heel.

According to the government, one of the causes of water shortage is the concentration of cities. So far the number of coastal cities has accounted for 46 percent of the total of cities in the nation. And more than 50 percent of the coastal cities are large and medium-sized ones. The density of cities doubles the average level of the country. As a result, the population of the 11 coastal provinces and cities accounted for more than 40 percent of the nation’s total and their industrial output value made up 64 percent of the total value of the country. And 80 percent of the city water supply are consumed by industrial enterprises.

It is estimated by relevant department that before the year 2010, more power capacity of at least 35000 MW is needed in coastal areas, resulting in the demand for 65 million cubic meters more of quality water each year.

A strategic study on the sustainable development of water resources in China proposed by the Chinese Academy of Engineering points out that according to the normal consumption of water in China and under the circumstance of not draining extra volume of water from underground sources, China is still in wanting of about 30-40 billion cubic meters of water. Even in a regular rainfall season, there will be about 13 million hectares of farmland in shortage of irrigation water. And the damage by drought will surpass a loss caused by floods.

At the very beginning of the 20th century, a saying went that the world “fought for coal in the 19th century, for petroleum in the 20th century and will fight for water in the 21st century.” Some people also predicted at the end of 20th century that the 21st century would be “a century of maritime.”

The State Oceanic Administration proposed that to guarantee a sustainable social and national economic development in the 21st century, it would be a practical approach to develop the use of seawater in a bid to solve the crisis of fresh water shortage in the country. The Hangzhou Water Treatment Technological Development Center (HWTTDC) under the administration began studying the technology of seawater desalination forty years ago almost from the same starting point with its counterparts in developed countries. Twenty years later, the administration set up its seawater desalination research institute in Tianjin. At the end of the 1980s, China became one of the few countries in the world that have mastered the technology in seawater desalination.

HWTTDC Director Cheng Yifang said, in present China, desalted seawater can be produced on scale through the processes of reverse osmosis, distillation and electroanalysis. The process of reverse osmosis consumes less energy source while the process of distillation can produce fresh water by using the remaining heat at a low cost.

In recent years, the reverse osmosis technology has greatly improved and perfected. In other countries, the desalination rate of membrane element has exceeded 99 percent. And many developed countries and rich countries that are in shortage of water resource have planned to make use of seawater. According to statistics, about 100 enterprises in China are engaging in the production and marketing of the technology of membrane elements, with an annual output value of 2 billion yuan.

Restriction on the Use of Water

This summer, Tanggu, a coastal city in Tianjin, also introduced the policy. A leading official of the city said that it would be in a precarious state when a city has only one source of water supply.

Suffering from two years of drought in running, Weihai, a coast city in east China’s Shandong Province, is now facing again the shortage of water. So, the city introduced the water restriction policy this year, which rations 2 tons of water for each person every month and the extra consumption shall be charged 40 yuan per ton. The policy is practical and efficient and it is never late to make a mend. Since the policy was enforced, every household in the city has been mobilized. As a result, the city can survive with fresh water for another two months. But if it has no rainfall after that, it would be too much trouble for the city, the residents complained.

Over the past decades of years, the state and local governments have taken a series of measures to solve the problem. A number of huge water diversion project and reservoirs have been built up. However, specialists believe that China, as a whole, is a country with scanty water resources. The diversion projects cannot increase the total capacity of fresh water in the country.

The 74 percent of the surface area of the globe on which we live are covered with water, of which, seawater accounts for 96.5 percent. China is a large maritime state covering a maritime area of 3 million sq. km. We have such a huge area of seawater, why should not we make use of it?

Since the 1950s, Hong Kong has been using seawater in daily life. At present, the 6.8 million populated region consumes about 200 million cubic meters of seawater in daily life, accounting for 75 percent of its total water use for daily life.

Over the past years, the seawater desalination research institute and HWTTDC have carried out a series studies on the daily life usage of the desalinized seawater. They have completed the study on the treatment technology of seawater mixed up with wastewater discharged by cities through a biochemical process, and the treatment technology of seawater for use in daily life.

It has been learned that in Tianjin and Dalian, a few units have applied the technology to daily life use on a trial base.

People Skeptic About Use of Desalinized Seawater

Zhang Yaojiang, deputy head of the Tianjin institute, said that as serious drought calamities have swept many coastal cities over the past two years, they are now more concerned about the development of seawater desalination research than ever. Since the summer came, the institute has been busy with calls on consultations. But so far, it has been only in a period of asking for advice. According to Dr. Yuan Guoling, who is in charge of the business, because the water supply system now practiced in the country is based on a welfare allowance policy, the cost of the tapped water is mostly subsidized by the government. As a result, the desalinized seawater as a commodity is not competitive in the market.

The technology of desalination has become mature after studies and development for 50 years. And its consumption of energy source has been reduced by about 90 percent. But each ton of desalted water still costs 4.5 to 8 yuan. On the world market, the price also ranges between US$0.67-2.5 per ton. These prices are much higher compared with the current cost of 1.4 to 2 yuan per ton of the tapped water. So, government policy support is required for desalinized seawater to be used in daily life.

No doubt, a number of people still take a skeptical attitude towards the desalinized seawater. Most of them, when asked to take a sip of it, hesitated. But they never hesitate to drink the purified water. In fact, the purified water is produced with a process basically similar to that of the desalinized seawater.

Since the 1970s, more coastal countries with scanty water resources are developing their own technology of desalination. Whatever they are oil-producing states in the Middle East or economically developed countries in the West, they have all established large desalination factories. According to the statistics made by the International Desalination Association (IDA), by the end of 1997, the output of a single desalter in the world reached 8.3 billion cubic meters a year, or accounting for one-thousandth of the total supply of fresh water of the world. Seawater has been provided for more than 100 million people in their daily life. And its usage is still growing at a rate ranging between 10 percent to 30 percent every year.

The sales volume of desalters reached US$2 billion or more a year during the 1990s. It is still growing. Most of the desalinized seawater consumers are distributed in the Middle East, and the countries along the Mediterranean Sea. By the end of 1995, according to IDA statistics, a total of 4.32 billion cubic meters of desalinized seawater were produced annually in the Middle East region, 720 million cubic meters in Europe, 1.08 billion cubic meters in North America, 828 million cubic meters in Asia, and 360 million cubic meters in Africa.

Lack of Government Policy Support

There are 30,000 people living on the Great Changshan Island Township of Changhai County, Dalian City. They all share water supply from a small water reservoir, two water ponds and four deep wells. Even under regular condition in a year, all these water sources can supply the residents each day no more than 1,000 cubic meters of fresh water. The local officials said, according to the regular volume of water required for each person each day, at least 100 liters per head are demanded. So the total daily volume of supply is 3,000 cubic meters.

The grave situation forced the county to adopt a long-term water ration system for the residents. Last April, the county was determined to build a seawater desalination project through reverse osmosis process with a capacity of 1,000 tons a day, designed by Tianjin Research Institute of Seawater Desalination and Comprehensive Use.

Last year, a most serious drought in history hit the county, making the reservoir and the two ponds all dry up. The desalination project was the only source of water supply in the place. It worked well. Therefore, the residents decided to raise fund to complete the second stage construction of the project.

At the demonstration meeting of the project, one researcher and investigator raised his right hand for a final and fatal vote. After the vote, he said, one day after the rain stopped, he came cross several schoolboys washing their face with the muddy water in small pits. He went over to see the pits and found they were pitted by the oxen hooves.

Yet not all the residents of places in shortage of water are lucky enough to have desalinized seawater. In financial straits, Weihai could not afford to complete its desalination project with a capacity of 10,000 tons. And in other coastal cities which suffer from serious shortage of water, people still take a wait-and-see attitude.

The deputy head of the Tianjin Research Institute of Seawater Desalination and Comprehensive Use said, the “age of water to be supplied inexhaustibly” has gone for good long ago. Whether to buy water or to wait and see is the question. At present, the causes of desalinized seawater failing to be widely accepted involves both the high cost of it and more important, a lack of available government policy support and the lag of people’s mind.

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