Membrane Desalination Process

Membrane Desalination via Reverse Osmosis (RO) is becoming one of the most widely used solution. It is particularly suited in countries under water stress and with limited energy resources. 

Over the years, SIDEM, as part of Veolia Water Technologies (VWT) has gained unrivaled expertise – and moved into the leading position – in the use of membrane technology, with over 7 million cubic meters of desalinated water produced per day. 

SIDEM benefits from Veolia Water Technologies expertise : 1,950 reverse osmosis facilities were installed by VWT within the scope of projects of all sizes and all complexity levels.

Reverse Osmosis occurs when pressure stronger than the osmotic pressure is applied to a saline water solution passing through a semipermeable membrane and a flow of water going to the pure water side is observed. The membrane allows the passage of the water but not of salts. By this simple process, high quality water can be extracted from a saline water solution. RO is efficient for low or high concentrations of salts and can thus be used to treat brackish water as well as seawater. 

The saline solution to be treated is separated into two phases:

  • the permeate : freshwater free of salts and impurities
  • the concentrate stream : brine enriched with the dissolved salts retained

Reverse Osmosis membranes being sensitive to the feed water quality, a highly effective pre-treatment is necessary upstream the RO skids of a desalination plant. 


A Reverse Osmosis plant is requiring several steps : 

  • Water Intake : it can be brackish or seawater. It can be directly pumped from the sea or from beachwells.
  • Pre-treatment : is a key step in the process 
  • Reverse Osmosis : is the heart of the process
  • Post-treatment and remineralisation : Fresh water extracted from the membranes must be treated and remineralised in accordance with the client requirements.
  • Storage of the desalinated water can be dealt with by SIDEM 
  • Management of the brines : Brines must be rejected in accordance with the local regulations.
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