Desalination, Vol.126, No.1-3, 213-218, 1999
Submarine seawater reverse osmosis desalination system
The project presented addresses the strategic topic of providing drinking and irrigation water through seawater desalination via a very energy-efficient and cost-competitive submarine technology. In conventional surface based industrial desalination plants applying the reverse osmosis (RO) technology, the freshwater flow behind the membranes is approximately 20-45% of the inlet seawater flow, depending on membrane type and characteristics. The resulting brine is disposed off into the sea. While state-of-the-art RO installations generate the required pressure with seawater resistant high-pressure pumps, the innovative submarine approach uses seawater hydrostatic pressure. The desalinated water, produced at about atmospheric pressure and collected in a submarine tank at the same working depth, is pumped to the sea surface. This approach saves about 50% of the electricity consumption with respect to an efficient conventional RO plant (about 2-2.5 kWh/m(3)) since only the outlet desalinated water is pumped instead of the inlet seawater, thus reducing the pumping flow rate by 55-80%. It avoids the pretreatment of the inlet seawater, therefore saving costs for chemicals and equipment.