“Water, water everywhere, nor any drop to drink.” When Samuel Taylor Coleridge wrote these words in his epic poem The Rime of the Ancient Mariner, he was considering the plight of a sailor in the north Atlantic surrounded by vast stretches of salt water but dying of thirst. The countries of the Gulf region are currently suffering a similarly ironic fate. Fortunately, however, industrial desalination has come to save the day.
The desalination industry has been around for over a century, but it has really taken off in the last thirty years. As natural water resources dry up and the world’s population burgeons, the industry is only going to expand.
It is estimated that there are already over 100,000 desalination plants on-line in more than 120 countries. Over half of that capacity is in the Gulf, where at least 60% of water available for consumption comes from desalination plants. A small, but rapidly growing percentage of Oman and Egypt’s water supplies come from desalination. Israel has the largest reverse osmosis (RO) facility in the world and it has four more desalination plants in the works. In Saudi Arabia, 66% of the water supply will come from desalination by 2025. Some countries like Qatar and Kuwait already rely on desalinated water to meet more than 60% of their domestic and industrial water needs.
And the industry is growing. According to a report by Global Water Intelligence, between 2006 and 2010, there will be a 61% increase in installed capacity, from 39.9 million cubic meters per day to 64.3 million cm/d. This means that capital investment in the industry will total some $25 billion by the end of 2010.
Amazingly, more than half of this will come from the private sector. Heavy private sector involvement in the field is unique in a sector where protective bureaucracies strive to keep valuable natural resources under their control. However, as the human resources of the region are not yet sufficient, Gulf countries are forced to find outside help. The recent oil boom has seen “Gulf governments looking for first class technology for their citizens and at the same time on the local level there is really a lack of know how,” says Patrice Fonlladosa, President and CEO of Veolia Water Africa/Middle East/India.
This need for human resources has seen firms from North America, Europe and the Far East vying for the many lucrative desalination contracts currently up for grabs.
Desalination technology
Removing salt from seawater or brackish water is the crux of desalination technology. Historically, solar powered stills were used for this purpose. The sun’s warmth would evaporate seawater and then the steam would condense, be trapped and finally utilized. This method of desalination is cheap, as it requires a few basic materials and no more energy than a bright, sunny day. Unfortunately, it is not possible to translate this to a larger scale. While it may be possible to generate enough water for one or two people with this method, supplying a village or a city is out of the question. Hence, modern science has worked out new ways of desalting water.
Contemporary commercial desalting is based on two main technologies: membrane desalination and thermal desalination. The first type of desalting works on the RO model whereby feed water passes through a semi-permeable membrane, which filters out the salt. Thermal desalination, on the other hand, sees feed water evaporated and then condensed, much like the solar still model.
Top 10 thermal plant suppliers by contracted capacity 2001-2005
Reverse osmosis
Although reverse osmosis was discovered and studied as early as 1850, it was not pioneered for use in desalination until the 1960s. RO, as its name suggests, is the reversal of the natural process of osmosis and it was finally commercialized for desalination in the 1970s. Perhaps the best way to understand the process is to imagine a glass beaker full of water, split down the middle with a membrane that will allow water, and nothing else, to pass. If salt is added to one side of the container, at first the water levels will remain the same. With time, however, fresh water would begin to seep through the membrane to the salt-water side because of osmotic pressure.
Osmotic pressure varies according to the ratio of salt to water. Average seawater has an osmotic pressure of 26 bars. In order to reverse the osmotic process and push seawater back through the membrane, more than 26 bars of pressure must be exerted. Most commercial RO facilities push feed water through their membrane elements at 50-60 bars worth of pressure.
It is also important to note the incredibly small size of the perforations in the membranes. These holes must be big enough to let water molecules past through, but stop salt ions. One industry expert likened a square centimeter of membrane to the size of France.
“Now,” he explained, “if you took a coin from your pocket and placed it on the ground in France that would be the relative size of the perforation in one square centimeter of membrane.” Not surprisingly, these membranes are rather difficult to manufacture. Advances in technology over the past 15 years, however, have dramatically lowered RO costs.
These advances mean that the core technology for RO has matured and prices are not likely to go much lower than $0.48 per cubic meter. Yet there is scope for improvement in the pretreatment of feed water. This is because, unlike in thermal desalination, pretreatment of RO feed water is critical. Bacteria can ‘foul’ membranes easily and other impurities can do much worse.
Unfortunately, because seawater is not the same the world round, there is no standardized pretreatment for RO. The process requires constant monitoring and minute adjustments to chemical inputs.
“The weak point for RO is water quality [due to pretreatment issues]. Because water quality in the Middle East is generally poor, most of our clients there prefer thermal desalination,” said Mr. Hyun-Sang Ahn, Vice President of RO/Water Treatment Business Division at Doosan Heavy Equipment. According to a study by the International Desalination Association, Doosan was number one in desalination production capacity between 2001 and 2005.
In summary, RO desalination is a solid, proven technology that is relatively cheap to install. Numerically, RO accounts for around 60% of the total desalination market and this is likely to increase over the next few years. Improvements in pretreatment will further solidify RO as the market share leader in desalination.
Thermal desalination
The other common type of desalting is thermal desalination. This method requires a cheap or free source of steam. Therefore, thermal desalination plants are usually paired with a power plant, as the excess heat from power production can be sent off to run the desalination plant. Thermal desalination is a solid performer and its feed water requires limited pretreatment. Because there are no membranes in use, there is no risk of fouling. Thermal desalination plants are simple and robust, and they support high capacities despite being more expensive to install than RO. Two main types of thermal desalination exist: multi-stage flash (MSF) and multiple effect distillation (MED).
Multi-stage flash
Thermal desalination depends on evaporation and MSF technology is no exception. In this process, preheated water is pumped into a super hot chamber, up to 120 degrees Celsius, which causes some of the water to evaporate instantaneously or ‘flash.’ The steam rises to the top of the chamber and then condenses around cooling pipes that lead the condensate into a product water (fresh water) exit channel. The remaining salt water is then pumped into an adjacent chamber, which is almost as hot as the first but has a lower air pressure. Due to the lower air pressure, the water evaporates at a lower temperature. This allows the water to pass through the system without being reheated. The process occurs throughout the length of the factory. The only factor limiting the length of the ‘train’ is the initial temperature. To date, most companies do not start the MSF process at more than 120 degrees because it results in accelerated corrosion of metal piping and fittings.
Just as in RO, the core technology for MSF is largely mature. The process has a very strong record of accomplishment. Unit sizes have increased steadily in correlation with skyrocketing demand for fresh water in recent years. Many MSF plants have been on-line for more than twenty years and show no signs of slowing down. Some have been retro-fitted and are expected to operate for at least another ten years.
Doosan Heavy Equipment is a major player in the MSF field. Ahn stated that longevity is an important factor in the desalination industry.
“Many independent water and power projects (IWPP) in the Gulf are built on 25 or even 30 year operating contracts,” he remarked. “So you have to be sure the firm will be around at least that long.”
Multiple effect distillation
Multiple Effect Distillation is older than, and functions in much the same way as, MSF. Slight operational differences between the two appear in the way feed water enters the system. For decades, MED unit sizes remained much smaller than MSF due to technical disadvantages arising from these differences. Over the last two years, however, MED unit sizes have grown substantially and they are now as productive as any other technology. SIDEM, a subsidiary of Veolia Water, was largely responsible for these advances thanks to a massive research and design effort. According to Christopher Gasson, publisher of Global Water Intelligence, “Veolia has a thermal technology that has a significant cost advantage over the main thermal desalination methods … What Veolia has done, through SIDEM, is find a way to deliver economies of scale with MED up to 800,000 cubic meters a day. This is why they have been successful.”
Veolia is excited about their revamped technology as well. “We have been very lucky to have one of our subsidiaries be specialized in MED technology for a long time. Now our MED is so good that even Suez [another French desalination firm] is utilizing Veolia when they want to install MED,” said Patrice Fonlladosa, President and CEO of Veolia Water Africa/Middle East/India. It is anticipated that Veolia will pitch its updated technology for the Ras al-Zour one million cubic meters a day desalination project in Saudi Arabia.
Given the recent advances, MED has become a potent rival to MSF. Yet Ahn of Doosan feels that, “the ability to execute a project is more important than what type of technology is used.” He also suggested that MED technology has not fully proven itself and potential desalination investors should look to experience and efficiency ahead of technology.
To sum up, MED is cheaper to install but more complex to operate than MSF. It requires less cooling water and it uses less electricity than MSF. Today, MED accounts for 24% of the thermal desalination industry. With these advantages, it is likely that MED will continue to eat away at MSF’s substantially larger share of the overall desalination market.
In conclusion, despite the appeal of MED and MSF among Gulf nations, RO will continue to take market share from thermal desalination over the coming years. By 2015 it is expected to account for 65% of the market. Furthermore, there will be a trend towards larger plants of all types. This is especially true of desalination in the Gulf as high oil prices will help to pay for some of the largest desalination plants ever unveiled, and with that, the future of desalination in the Gulf seems as bright as the Arabian sun.
Capital expenditure on desalination by country, 2006-2015
