Prospects for progress: the Arabian Gulf states
Abdulmajeed Ali Alawadhi from Bahrain's Ministry of Electricity & Water reviews current desalination practices in the Gulf and looks at future prospects for desalination in the region, arguing that further research on MSF is needed to bring costs down.
At present the water requirements in the GCC countries are met by groundwater (90%), desalinated water (7.5%) and the balance by treated wastewater. Recycling of treated wastewater, introduced in the 1980s is expected to contribute significantly in the coming years.
The fresh water demands of Gulf countries were met almost entirely by conventional sources until desalination plants were introduced in the mid-1960s. Groundwater aquifers represent a major source of water in Saudi Arabia, Bahrain, Qatar and Kuwait, and are contained within deep geological formations. These formations extend to cover the whole of Saudi Arabia, and some extend to Bahrain, Qatar, Kuwait, the UAE, Oman, Yemen, Jordan, Syria and Iraq. As the salt content in these geological formations is different from one location to another, groundwater salinity is correspondingly different from one place to the next. Consequently, while water from some underground sources is considered acceptable, from other locations it is not so and requires still further treatment.
Although the strategic storage of groundwater in the Arabian Peninsula is estimated to be around 20 x 1012m3, renewable resources are limited due to the limited recharge. It has been estimated that about 3000Mm3/year is recharged and about 4000Mm3/year available as surface water, whereas abstraction is about 17,000Mm3/year in the GCC countries. Consequently, water is being abstracted from storage at a faster rate than it is recharged. This has resulted in the continuous decline of groundwater levels and a deterioration in quality due to seawater intrusion. There is a clear imbalance between available water resources and water demand, a gap which is expected to widen in the future. At present, total water demand is about 20,000Mm3/year, with non renewable resources accounting for 75%. The remainder is supplied by renewable conventional sources, desalination plants and recycled wastewater. Latest projections estimate total water demand to reach 28,000Mm3/year by 2020.
GCC states are considered to be the world leaders in using non-conventional sources of water, especially desalination. The bulk of the total installed capacity of all desalination plants in the world is in the Gulf region. One of the first land based seawater desalination plants in the world was commissioned in Saudi Arabia in 1907 followed by others to supply potable water more than 60 years ago. Kuwait was instrumental in developing the MSF process in the 1950s. Tremendous progress was made in the 1960s when Saudi Arabia started its massive desalination programmes, which contributed significantly to the progress of desalination technology world-wide.
By 1995, the total number of desalination plants built in the GCC states was 45, out of which 23 were in Saudi Arabia. Overall water production amounted to approximately 1900Mm3/year.
MSF is the desalination technique most widely used in many of the GCC states, followed by RO. Even though RO showed a lot of promise when it emerged two decades ago, it has not really taken off due to the raw water conditions in the Gulf.
It appears that MSF will continue to be the work horse in the Arabian Gulf in the coming years. Total desalination capacity in the GCC countries is expected to increase to 3000Mm3/year by 2020. In order to meet domestic water demands, GCC states are going ahead with the construction of large capacity desalination plants despite their relatively high cost, which ranges between $5-10/GPD of installed capacity.
Current desalination practices
There are three major distillation processes, MSF, MED and vapour compression (VC), in use commercially in the Gulf region. Although MED was a predecessor to MSF and considered thermodynamically more efficient, it could not compete with MSF for long. Its contribution in the world market has gradually dropped from a high of about 60% in 1958 to about 6% now.
The main reason for this decline is related to O&M problems due to scaling and fouling, especially at high temperature operation. The only MED plant in commercial operation in the GCC is in the UAE. Small VC plants are in operation in almost all the GCC countries. However, MSF plants provide the bulk of installed capacity.
The major membrane desalination processes in use commercially are RO, electrodialysis and membrane softening. Even though RO received a lot of attention when it was introduced in the Gulf about two decades ago, it is gradually losing its share to MSF. This is due to the problems faced with feed waters in the Gulf which necessitate complex pre-treatment systems.
MSF units are preferred for large size plants and are most competitive for plants larger than 20,000m3/d. MED can be competitive for medium sized plants while VC is used mostly for smaller plants. RO is the only process which can be competitive for any plant.
Unit cost of desalinated water
The key parameters that affect desalination costs can be classified as follows:
- plant size;
- process type and design;
- finance costs;
- feed water quality;
- intake type;
- O&M requirements;
- and environmental factors
- construction (30-40%)
- O&M (40-70%)
- energy (20-70%)
- labour, chemicals, spares (10-30%)
- membrane replacement (10-20%)
Even though preliminary studies and process design are invariably conducted within the Gulf, the region depends heavily on imports for most of its desalting machinery. Therefore, it is normal practice to award turnkey contracts supervised by consultants to ensure client's interests. Privatisation of some of the facilities is being considered in areas where possible.
R&D in the region
The Kuwait Institute for Scientific Research, functioning in Kuwait from 1960, concentrated initially on MSF. Since the introduction of RO in the region, the Institute's research includes trials with different membranes, optimisation of pre-treatment process and optimisation of the various operational parameters to arrive at minimum unit water cost.
In the UAE, the General Council for Water Resources compiles and assesses essential information on available water resources. With this information and future water demand estimates, studies are carried out to determine ways of conserving water resources.
In Oman, the Ministry of Water Resources is responsible for performing the studies, research and surveys necessary to uncover new water resources and find the means to preserve existing ones.
The Middle East Desalination Research Centre (MEDRC) was set up in Oman to develop research in the region. It remains to be seen what research will be done in Oman at this centre for the development of desalination in the Middle East. In the eastern and western provinces of Saudi Arabia there are facilities conducting research on various aspects of desalination. They are primarily involved with the optimisation of operating parameters.
It is clear that even though MSF is the workhorse of the desalination industry in the Gulf region, there is not enough research being done to improve the technology as such. Countries outside the region do not have many installed MSF plants and are therefore not interested in MSF research. Research outside the Gulf is more focussed on membrane technology, as it is more prevalent for desalting brackish water. It therefore becomes the responsibility of a well-funded organisation like MEDRC to focus on basic research on improving MSF technology.
Future desalination in the region
More and more desalination plants will need to be built in the region to compensate for the deterioration in the quality and quantity of groundwater. It is anticipated that potable water produced by desalination will double in the coming 20 years. In all the Gulf countries there are plans every year for more and more desalination plants A majority of them are for seawater plants. MSF plants with unit capacity up to 12.5MGD are likely to dominate the scene in the Gulf countries for at least another ten years. Even though the number of RO plants in the region is growing, it is highly unlikely they might be able to catch up with MSF. RO is not generally in favour in the Gulf due to the complexity of pre-treatment required for Gulf feed waters.
As desalination by MSF is energy intensive, research must be carried out on cheaper energy sources and also on alternative forms of desalination.
This paper was first presented at the IDA World Congress on Desalination and Water Reuse, San Diego, US, 29 August to 3 September 1999.