Desalination

The basic desalination process can be seen in the diagram below. The water is captured by means of a pump feeding directly from the sea, a beach well or a salty water well, to be sent to the chemical pre-treatment units, where the the right components will be dispensed for each case, and physical pre-treatment that consists of one or two filtration stages, multilayer sand filtration and fine filtration using wound cartridges.

Once the water has been pretreated, it is pumped at high pressure (from 10 to 25 bar for salty water and up to 70 bar for seawater) towards the membranes where the aforementioned reverse osmosis phenomenon takes place.

Two water currents are separated from the membranes, one with low salinity known as the permeate and the other that takes away the salts removed from the high concentration permeate called the reject.

The energy from the reject current can be used by means of an energy recovery system that drops the high pressure pump’s consumption either by mechanical coupling to the same pump axle or by hydraulic coupling to the feeder current.

The permeate or water produced can be used directly or pre-treated if it is going to be used for human consumption or another specific use. In the event of using it for human consumption, chlorinating the water will be sufficient to sterilise it and harden it by adding calcium.

The typical conversions for a reverse osmosis system alongside energy consumption per cubic metre of water produced can be seen in the table attached: