Why Is Desalination Becoming So Important?
Desalination is a technology which includes several processes that remove salt and other minerals from seawater to produce freshwater. In recent decades, this technology developed rapidly and becoming more and more popular around the world. This essay will focus on the effects of using desalination. It begins with the reason why this technology develop rapidly in the recent years. After that, some economic and environmental benefits and drawbacks of desalination will be analysed. Finally, give a conclusion.
Water is a basic and crucial resource for survival and growth of life. We can not live without water. However, there is a research by Fiorenza (2002) shows that nearly one fourth of mankind is suffering from inadequate fresh water supply, both of quality and quantity. Considering water shortage concerns about 80 countries and has caused some serious results in many places, the water shortage phenomenon is becoming a serious global problem that affects people’s daily life and hindered the social development. Because of the increasing number of global population and expansion of both industrial and agricultural activities, the water requirement will increasing rapidly in a very near future. It is obviously that the traditional fresh water supply system can not meet the requirement any more. An alternative water supply option is need to help us deal with this problem.
Water is so important for human beings, therefore, we have already developed many kinds of water supply systems. But all of them have a common problem and also the fatal problem is that they all need natural fresh water resources. The research by Khawaji (2007) illustrates that nearly 97% of the earthââ‚¬â„¢s water is seawater while another 2% is fresh water but locked in icecaps and glaciers. The available fresh water just accounts for about 0.5% of the earthââ‚¬â„¢s total water supply. Another point should be considered is human activities have polluted a large amount of fresh water resource. It means that all the traditional water supply systems just can use much less than 0.5% water resource. It is obvious that we can not just rely on these traditional water supply systems any more. Comparing with these traditional options, the desalination technology does not need natural fresh water resources, desalination equipment can produce fresh water from seawater. This technology give human beings an opportunity that we can use the majority of earthââ‚¬â„¢s water resource. This is really a revolutionary change that we need not rely on natural fresh water resources any more. Because of this unique advantage, desalination has developed rapidly in recent decades and playing an important role in many countries now. For example, according to research by Zhou (2003), in Saudi Arabia the desalination equipment produces more than 6,000,000 m3 of freshwater per day. This technology has become a reliable fresh water source for human beings.
In fourth century BC, Aristotle found that when saltwater turns into vapor, salt and freshwater will separated. This was the first desalination theory and it has already been discoverd more than 2000 years. The previous analysis shows that desalination has a lot of advantages, but it can be questioned just used in recent years. It is because the former desalination technology cost too much and was not reliable enough. This is also the main reason why there are many critics against the use of desalination. However, the desalination technology has advanced a lot in the last 30 years, especially, the invention of multi-stage flash process and reverse osmosis. According to the research by Tsiourtis (2001) shows that 86% desalination factory use these two desalination processes now. In addition, these two methods are the most commercially important desalination technologies. Furthermore “technological advances were made on the multi-stage flash (MSF) process (materials and process) and on reverse osmosis (RO), with improvement on the membranes and the energy recovery equipment.” (qtd. Tsiourtis, 2001) So these technological advances in the last 30 years have driven down the cost of desalinated water very much. The figure 1 illustrats that the price of desalination shows a decreasing trend from 1988 to 2000. The total cost of desalination decreased from1.7$/m3 in 1998 to 0.7$/m3 in 2000. It is an acceptable price for many countries now and due to the decreasing trend, it can be predicted that the desalination will more cheaper in the future.
The decreasing cost trend is just one economic benefit of desalination. Another reason is in some situations, desalination is a cheaper water supply option. For example, China’s water resources are uneven distributed and many places in northern China are facing the water shortage problem. So, the government decides to build a long pipeline to transfer water from the Yangtze River to area in northern China. Research by Liu and Zheng (2002) shows the main canal would be 1150 km long. From the research by Kally (1993) we already find that the cost of transport is around 0.061$/m3 per 100 km. Therefore, it means that the cost of transferring water will more than 0.07$/m3. It is higher than using desalination, additionally, because of the desalination cost has fallen from 1.7$/m3 to 0.7 $/m3 and still keep an decreasing trend. There is no reason to believe that the trend will not continue in the future. So desalination also has its economic benefits in some situations.
Desalination not only has economic benefits, but also has many environmental advantages. Firstly, compares with the water transport, desalination does not need so much pipeline and pumping stations. It means that less land will be occupied and less energy will be wasted in the transferring process. After that, because these traditional water supply options need fresh water supply, the overuse of surface water and groundwater has caused many serious consequences. For instance, the ground surface settlement happened in many places in China just because of the abuse of groundwater. Research by Chai et al. (2004) shows that due to the abuse of groundwater, surface surveys of land subsidence is 2 to 3 meters in the central area of Shanghai. Ground surface settlement is harmful to a building’s foundation and will cause dangerous results. However, desalination’s resource is seawater, it will never limited and never will have these troubles. So, compare with some traditional water supply options, the desalination system also has some of it’s own environmental benefits.
From the above analysis we find that a desalination system has it’s own advantages no matter in economic and environmental aspects. But it is undeniable that this technology still has some drawbacks in both aspects.
Firstly, the desalination process has a by-product called brine, What is “a kind of water that contents double salt of seawater and also contains membrane cleaning chemicals and other chemicals used for scale and corrosion control”(qtd .Tsiourtis, 2001). If we can not treat the brine well, it will cause serious pollution. Then there are some chemicals will be used in the desalination process. It also will cause some pollution. After that, noise pollution is another problem, the noise produced by these machines will trouble people. Furthermore, comparing with other water supply options, desalination still a little expensive than these traditional ones in normal situations, many countries can afford this technology as the option to solve their water shortage problems.
Overall, desalination is already becoming a very important water supply option, especially in these energy-rich, dry and lack of freshwater resource areas, such as these Middle East countries. This technology give human beings an new option to solve water shortage problem. Although, this technology still have some problems but because of its own advantages and the trend of desalination technology development, we can believe that desalination will have a bright future. This technology will play an more important role in future.
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