The UK Ministry of Defence (MoD) in Gibraltar is a naval base of significant strategic importance to the Western NATO alliance, dedicated to the service and maintenance of the NATO fleet and the Royal Navy.

The MoD in Gibraltar has traditionally been in charge of the provision of drinking water and seawater for fire fighting and sanitary services.

For security reasons, the base utilities infra-structure is separate from the rest of Gibraltar, particularly the water supply which not only sustains the naval facility on an ongoing basis but also services visiting ships. The base also exports a certain quantity of water to the civilian population.

The MoD in Gibraltar has operated a number of desalination plants since the early part of the last century, using their own resources. The replacement of the seawater reverse osmosis plant was recognized as a priority and the MoD issued a call for tenders for the design, construction and operation of the new facility.

The requirement was the uninterrupted provision of 1200 m³/day of drinking water to EU specification and 850 m³/day of filtered seawater.

The original plant being sited within a set of caverns which were structurally distressed, it was necessary to find a different location for the new plant. Security and quality of supply were also key requirements in the project.

Ministry of Defence in Gibraltar retained Veolia Water for the design, construction and maintenance of their seawater desalination plant.

Veolia Water's scope of services includes :

• ­refurbishing the existing seawater intake by removing the need to maintain feed culverts passing through rock tunnels,
• ­replacing the existing production plant with a state-of-the art new desalination facility,
• ­progressively decommissioning the existing plant.

Since energy is very expensive in Gibraltar, a primary driver for the design of the new plant was energy efficiency. The installation is equipped with the latest energy recovery system, using a pressure exchanger, increasing the recovered energy by 30% from the previous plant and affording a significant saving to the Ministry of Defense.

Technology used :

• ­abstraction of seawater via intake pumping system,
• ­non-potable water production : seawater filtration (850m³/day),
• ­potable water production : pre-treatment system + two RO trains (2 x 700 m³/day)