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A desalination plant is a facility that converts salt sea water into water suitable for human consumption, or for industrial and irrigation uses.

There are several desalination processes:

  • Distillation with a still, (a process similar to that which occurs naturally during the water cycle) consisting of boiling seawater in a still, collecting the steam and condensing it to obtain fresh water.

  • Solar distillation: Imitating the water cycle, it consists of evaporating seawater in large facilities with roofs where it condenses and is collected in the form of fresh water.

  • Reverse osmosis: It is the most used process and consumes less energy than the rest as it is based on the use of semipermeable membranes that let water pass, but not salt.

  • Nanofiltration: Process similar to reverse osmosis, but in which nanotube membranes of greater permeability are used that, in addition to removing salt, also eliminate traces of contaminants.

  • Electrodialysis: The process by which fresh water is obtained by moving salt water through electrically charged membranes that trap salt ions dissolved in water.

  • Formation of gaseous hydrates: Process in which salt water is combined with gaseous hydrates such as, for example, propane, at high pressure and low temperature. Once combined, the temperature is raised, obtaining fresh water free of salts and impurities.

In any of the above desalination procedures, a water catchment system is necessary and in the last four described, a brine evacuation system.

Water collection and brine discharge systems have evolved over the years mainly due to the need to adapt to new environmental regulations, improvements in technological innovation and increased efficiency of new desalination plants.


Water intake

To transport the water from the intake point to the well or pumping tank, it is necessary to execute one or more sea outfalls. The execution of these by microtunnel is considered one of the best options due, to a large extent, to its low environmental impact on the marine ecosystem.

Brine lines

Sea outfalls are also essential as a point of outlet for brine from desalination plants. One of the most suitable solutions for the execution of the sea outfall is also the realization of a microtunnel that, in this case, will be connected to a diffuser in the discharge area.



  • By Miguel Bello, Mario. Catchment systems in seawater desalination plants (I). Iagua. June 2016


  • Peter Hennig y Lutz zur Linde, (18 de Mayo del 2011). Trenchless installation methods of Sea Outfalls. OSMGP.


  • Desalination: the process to convert seawater into drinking water - Iberdrola

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