Having been overlooked for years as a viable alternative to the thermal technologies of multi-stage flash (MSF) and multi-effect distillation (MED) on large-scale projects, RO is finally making a comeback. It is now employed in a hybrid configuration on the Fujairah co-generation plant. It was recently selected as the technology for the 26 million-g/d unit on the Barka 2/Rusayl project, in a first for a Gulf independent water and power project (IWPP). And plans are afoot to build large-scale stand-alone installations in Oman, Abu Dhabi and Dubai.

Much is riding on the success of the new wave of RO projects. 'Everyone is now

talking about RO, but it still has to overcome the credibility issue on this side of the Gulf,' says an international consultant, based in

Abu Dhabi. 'The technology has a lot of merits in terms of costs, but it now needs to perform operation-wise to give confidence to the end-user.'

On the other side of the GCC, RO has fared much better. In the deeper and higher-quality waters of the Red Sea, Saudi Arabia's Saline Water Conversion Corporation (SWCC) has built up a strong track record over the past 15 years with the technology. Developers have also shown few qualms about using it in the kingdom. A 40 million-g/d unit is being installed on the IWPP serving the Rabigh Refining & Petrochemical Company (Petro-Rabigh) development. The frontrunner for the Shuqaiq IWPP, a group headed by the local ACWAPower, is proposing RO for the 47 million-g/d desalination component.

The contrasting fortunes from either side of the peninsula underline the importance of location for RO. Even its strongest supporters acknowledge that, from a commercial standpoint, the membrane technology is not suitable everywhere especially in water where there is low circulation and which is close to industrial activity. In the shallower Gulf, RO plants also require water pre-treatment systems to reduce membrane fouling, an issue originally highlighted by the failings of the Addur plant.

'In the history of RO, Addur is now a long time ago,' says Eric Jankel, business development director for the Middle East at the US' CH2MHill. 'A lot more is understood about the RO membrane and the need for pre-treatment than 15 years ago, when Addur was built. That has been shown by clients such as the Federal Electricity & Water Authority (FEWA) in the UAE, which has been successfully running smaller RO plants for some time.'

Technology advances have also seen RO costs fall. According to Jankel, the total water costs of an RO plant, which covers the entire lifespan of a project, have dropped by

30-50 per cent over the past decade.

One of the key attractions of RO is that, unlike thermal technologies, units do not have to be built in association with power plants. In theory and often in practice they can literally be plugged into the network. In contrast, MSF and MED are very much part of co-generation, using the waste heat from thermal power plants to produce water. The difference has implications on both the cost of investment RO's is lower and of operations. With the Gulf seeing wild swings in power demand over the course of the year and water demand remaining fairly constant, power units are often run in winter primarily