For UAE, hope in deep ocean water desalination

The UAE is part of a highly water stressed region as the Gulf states do not have any rivers, rainfall is minimal, and what groundwater is left has largely run out. All of which makes desalination the only viable option to supply the country with stable and sustainable access to long-term fresh water, while at the same time coping with a population that is continuing to grow and is about to cross 9 million.

Desalination carries two major challenges: the high costs of conventional desalination plants with technology based on burning gas and the ever-increasing salinity of the water in the Arabian Gulf. There is a lot of ongoing work on how to mitigate the present reliance on gas by looking at more solar-based power in the UAE, but the growing salinity of the Gulf waters remains a problem.

But despite these particular challenges in the Gulf, desalination is the long-term answer for most of the rest of the world as the global population of 7 billion will continue to grow and peak at around 12 to 12.5 billion, when the current conventional supply of fresh water will not cope. The answer lies in looking outside the 2.5 per cent of global water which is fresh (of which half is anyway tied up in the two icecaps) and instead look at how to access the 97.5 per cent of the world’s water that is seawater. The search for efficient and cost-effective desalination is becoming a global priority.

There are interesting examples all over the world of how some other water stressed sites are tackling the issue. The highly populated islands of Japan and Taiwan as well as South Korea and Hawaii are very different from the desert climate of the Arabian Gulf but they are very short of water. As part of their desalination efforts for more than 10 years, they have been using a new technology which intakes the necessary seawater through long pipes running well out to sea so that they gather the water from deep under the ocean’s surface.

“Using deep ocean water from the total dark of below 300 metres has many benefits,” said Jacques Le Moigne, CEO of Ocean Fresh Water (OFW), a Paris-based company that has been studying the delivery of deep ocean water as quality drinking water for the past two years.

“It carries almost no organic matter or chlorophyll and so contains virtually no bacteria, as well as having more nutrients from the ionic minerals and trace elements at that pressure and depth. Deep ocean water is the world’s last source of pure water, and if this deep water technology can be harnessed for supply into the GCC it could also offer a solution to the growing salinity in the Arabian Gulf. To avoid ejection of high concentrations of brine by land-based desalination plants into the Gulf, a radical new solution has been designed by Ocean Fresh Water which addresses the question of high quality drinking water. It has designed mobile marine bottling plants which utilise the last pure source of water on the planet to produce drinking water rich in marine minerals while smoothly disseminating brine over a large area as they sail. Our marine bottling plants prevent severe increases in salinity and deterioration of sea life while producing high quality water,” Le Moigne told Weekend Review.

The UAE currently spends nearly Dh12 billion per year on water desalination to meet its fast-growing need of drinking water and offset dwindling reserves, according to the UAE government figures. The country has almost 70 seawater desalination plants, accounting for around 14 per cent of the world’s total output of desalinated water, an astonishingly high proportion for such a small country.

The growth in the UAE is matched by its fellow states on the Gulf coast. The population of GCC countries has risen 43 per cent from about 30 million in 2002 to nearly 43.5 million in 2010, according to World Bank and Food and Agriculture Organisation figures in 2012, and this population is expected to grow.

The scale of water stress in the Gulf region was defined by Dr Rashid Ahmad Bin Fahd, minister of environment and water, at the Emirates Centre for Strategic Research and Studies’ 17th annual conference on Water and Food Security. He said the GCC region’s water demand had increased from 6 billion cubic metres in 1980 to 26 billion cubic metres in 1995, while the annual per capita share of water had decreased from 700 cubic metres in 1970 to 170 cubic metres in 2000.

“The groundwater shortage has led to growing demand for fresh water. Around 70 per cent of available fresh water is used by the agriculture sector, while water demand in the urban sector has more than doubled. Moreover, domestic water consumption is not economical. All these factors complicate the problem,” Dr Bin Fahd said.

The brine pouring out from the hundreds of desalination plants around the coast of the Arabian Gulf is becoming a long-term threat to the stability of the Gulf’s water. Desalination brines are just dumped back into the sea, even if some more modern plants manage a modest amount of salt and rare metal extraction.

After extracting the fresh water, most of the brine has about double the salinity of natural seawater. For example, in a reverse osmosis desalination plant, water is taken from the sea and when the brine is discharged back to the sea, salinity will increase by 70 per cent overall, according to a paper in the January 2011 issue of the “International Journal of Academic Research”.

The IIAR paper goes on to argue that if a desalination plant is built close to the coast there is the opportunity to install one or more outfalls to the sea, which can minimise or reduce the environmental impact of brine discharge. The problem is that this can only refer to the immediate effect, and not the total effect over many years in a closed sea such as the Arabian Gulf, where the IIAR reports that the GCC states alone have desalination plants with a total seawater desalination capacity of approximately 45 per cent of the worldwide daily production, and this does not include the desalination going on in Iran.

The effect of all this on the Gulf seawater is drastic. Historically, Gulf salinity has been around 35,000 and 37,000 parts per million (ppm), which is not out of line with many of the world’s seas and oceans. But Dr Shawki Bargouti, who was the director-general of the Dubai-based International Centre for Biosaline Agriculture in 2009, quoted the UAE Ministry of Environment and Water showing that by 1999 salinity had got up to 42,000ppm and reached 56,000ppm in some places, or 55 per cent more salinity than standard ocean water. This is directly attributable to coastal desalination plants in the Gulf. And the figure will keep increasing.

The problem is that the Arabian Gulf is an enclosed area of water with natural evaporation from temperature and wind exceeding the freshwater input from the rivers Tigris and Euphrates, so the major inflow is from the already salty water of the Arabian Sea through the Strait of Hormuz. This natural situation was able to cope until the onslaught of modern technology. Today brine from the hundreds of desalination plants, as well as the ongoing pollution from cities and chemical-heavy agriculture around the Gulf shores, is adding its dangerous weight to the minimal natural turnover of water.

The Arabian Gulf is too shallow to benefit from desalinating deep ocean water. “At around 150 metres maximum, the Gulf cannot benefit from the environmental advantages of converting deep ocean water into quality drinking water,” said Le Moigne. “But sourcing converted deep ocean water from outside the Gulf would be of great benefit to the littoral states of the Arabian Gulf because it would both help preserve increasingly scarce groundwater resources, as well as stop the sea from disintegrating into a polluted and grossly over-saline maritime desert. This alternative delivery of good quality drinking water converted from deep ocean water is something we have been looking into for some time, based on what has been achieved in Japan, Hawaii and Taiwan.

source : gulfnews