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Seawater intake occurs at a distance of 2.2 kilometres from the coast and at a depth of 30 metres. It reaches the coast by means of two water pipes 1.8 metres in diameter. From here, a pumping station sends the water to the desalination plant by means of a pipeline 2 metres in diameter and 3 kilometres in length, which passes under the Llobregat river. This intake point was chosen as it is the nearest place that guarantees sufficient water quality that is not affected by the river mouth or by the extension of the port.
Seawater must be cleaned of impurities before it reaches the stage of reverse osmosis. In the first stage of pre-treatment, purification by means of flotation is carried out. Air is injected into the bottom of ten tanks and various analytes are added to coagulate the material in suspension which is then brought to the surface and removed. At this stage the water is disinfected with chloride dioxide and sodium hypochlorite.
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The water then passes to the first filtering stage. This is a group of 20 open two-layered sand filters. The second filtering is carried out by means of 20 pressure filters also with two layers of sand. The third filtering is carried out by means of 5 micron cartridge filters.
The following step is the intake of pre-treated and filtered water into the reverse osmosis system. It will be delivered at a pressure of 70 atmospheres to the membrane banks, which will only permit the passing of water and not the salt or the remaining elements.
These filters measure one thousandth of a micron. The plant will have 10 suppliers of reverse osmosis, with a unit capacity of 20,000 m3/day. The performance of the system will be 45%. Of every 100 litres of seawater, 45 will be converted into drinking water and 55 will be returned to the sea.
The water that leaves this process will be too pure for consumption. It will need to be re-mineralized with calcite beds and sodium hydroxide. It will be disinfected once again with chloride dioxide.
