Desalination is vital in providing the region's cities with supplies of potable water. But the process itself is pouring more and more brine back into the sea, raising the question of whether the technology will one day cease to be economically feasible.
Never mind peak oil, or even peak water: Some experts are pondering the possibility of the UAE's development being limited by "peak salt" - the notional point at which the Arabian Gulf becomes so salty that relying on it for fresh water stops being economically feasible. There is cause for concern, says Dr Shawki Barghouti, director-general of the International Centre for Biosaline Agriculture (ICBA) in Dubai. "Kuwait, Qatar, Bahrain, Saudi Arabia and the UAE all have their desalination plants along the Gulf's shores," he said. "The brine that these desalination plants produce is being dumped back into the ocean." In addition, damming of rivers has cut the flow of fresh water into the Gulf - and the water that does flow in is increasingly polluted.
"All fresh water in the Gulf has been minimised significantly," said Dr Mohammed Dawoud, manager of the water resources department at the Environment Agency-Abu Dhabi (EAD). "The pollution load has increased dramatically." The implications of this, says Dr Barghouti of the ICBA, are exacerbated by the Gulf's small size, relative shallowness and slow circulation. "The Gulf is a small water body, it is more like a lake," he said. "It is open to the ocean at the Strait of Hormuz, but because the opening is narrow, water is replaced once every eight to nine years."
This means the polluted water that comes from cities, farms, factories and desalination plants around the Gulf's shores takes longer to flush out, and the amount of pollution is significant and rising. In the north, the outflow of the Shatt al-Arab river carries with it "the polluted water of Basra and Baghdad", said Dr Barghouti. Kuwait, Saudi Arabia and Qatar all have sewage treatment plants that are "not up to the full standards", he said, while coastal cities in Iran are dumping raw sewage into the sea.
"In addition to all this, you have thousands of tankers entering the Gulf and washing their tanks illegally," said Dr Barghouti. "Between the tankers, pollution from urban centres and the brine disposed from desalination plants, the Gulf is almost dead." Because of its shallowness and the high evaporation rates in the hot summer season, the Gulf is one of the saltiest seas, and this is already a challenge for even the latest desalination technologies. Experts in the region have been pressing for the adoption of membrane desalination - reverse osmosis - which is more energy-efficient and kinder to the environment than thermal processes, which currently provide the bulk of the UAE's potable water, but the high salinity presents a challenge to the membrane technology.
"The water of the Arabian Gulf is much higher in salinity, therefore the pre-treatment necessary for reverse osmosis is more difficult here," said Leon Awerbuch, president and chief technical officer of the US-based Leading Edge Technologies, which has worked on many desalination projects in the region. The question is whether a time will come when no technology can cope with the salt load - peak salt, in other words.
"That becomes a very speculative question, and the answer you will receive today is speculative," said Rob Huehmer, desalination technology leader at CH2M HILL, a global company that provides engineering, construction and operations services. "I have read at least one scientific study that made that premise, but we are a long way away from having a consensus on this," he said. What is certain is that in coastal areas close to desalination plants, the sea is getting ever saltier.
Historically, Gulf salinity was measured at between 35,000 and 37,000 parts per million (ppm), but Dr Barghouti quotes figures by the UAE Ministry of Environment and Water which show that 10 years ago salinity was at 42,000 ppm but in parts is now close to 56,000 ppm. "At Umm al Nar," where one of the emirate's power and water plants is located, "I have measured 50,000 ppm myself," said Dr Dawoud.
The EAD is drafting a proposal to install electronic monitoring stations to measure the impact of desalination plants. "If the concentration of salt increases, desalination plants will need more energy to remove it," said Dr Barghouti. "Definitely the future is going to be more expensive." One possible solution to offset the problem of hyper-salinity was to discharge the salty waste far out at sea through "diffuser lines", which promote better mixing of the brine and sea water, said Mr Huehmer of CH2M Hill. This, however, would add anything between three and eight per cent to the overall cost of a project.
Another answer might be to abandon the Arabian Gulf as a source and tap the waters of the Gulf of Oman. Abu Dhabi has already done this; one of the emirate's nine major desalination plants is in Fujairah. But recent experiences emphasise just how vulnerable the UAE is when it comes to freshwater supplies. Until recently, the Fujairah plant was battling another problem - a bloom of toxic algae that started in August 2008 and lasted until March this year, killing thousands of marine animals and, according to the Abu Dhabi master plan, disrupting water production and causing daily losses of more than Dh367,000 (US$100,000).
"This red tide has led some desalination plants to temporarily shut down as a precautionary measure in order to avoid contamination of water," said a spokesman for Veolia Water, the world's largest water and waste water services provider and a partner in the Fujairah plant, a hybrid of the reverse osmosis and multiple-effect distillation processes. But beyond any technical innovations, more governmental oversight and regional co-operation had a vital role to play, said Dr Barghouti.
"The strategy has so far been that the private sector can handle it," he said; instead, the operation of desalination plants "has to be carried out under proper public supervision". Above all, regional co-operation was vital if the quality of the Gulf's waters was to be improved. "There is now no co-ordination between countries," and a scheme similar to the broad co-ordination that exists in the Mediterranean and the Black Sea regions should be implemented in the Gulf, Dr Barghouti said.