Distillation plant development and cost update

Recent developments in desalination technology have resulted in significant savings in cost compared with earlier plants. Both distillation and reverse osmosis processes are now viable means of water production from a seawater source in the developing countries of the MENA area as well as in the more traditional oil-producing Gulf States. Three processes are commercially available for large size plants for desalinating seawater: multi-stage flash distillation (MSF), multiple effect distillation (MED) and reverse osmosis (RO). This paper describes the current development of the MSF and MED distillation processes and compares the costs of water production with seawater RO. Advances in plant technology and in energy efficiency have resulted in savings of up to 50% compared with costs only a few years ago. Water costs in the range of 0.7 to 0.9 US $/m3 are now achievable, either with RO or large distillation plants, depending on the seawater source and cost of available energy. Future developments should reduce costs even further.

• MSF distillation is a proved and mature technology, but with high-energy consumption. This process is competitive only for very large plants and where energy costs are low. • MED distillation is more flexible and has lower energy consumption and greater development potential than MSF. Unit size is presently limited to about 5 migd. MED has the potential to compete with RO in the lowto medium-range of energy costs. • Recent developments in RO technology have led to significant cost savings both in capital and operating costs. Energy consumption is considerably lower than distillation, making RO less sensitive to high-energy costs. Developments such as brine concentrator technology will help to reduce costs still further. • Seawater desalination has now developed to the point where costs are competitive with conventional and established technologies for large-scale water production in the MENA area.