Brine Concentration

Membrane based brine concentration is a disruptive, innovative process that substantially lowers the operating costs of new or existing Zero Liquid Discharge (ZLD) plants. It may also be used on its own for the concentration of liquids generally up to a Total Dissolved Solids (TDS) in excess of 200,000 mg/l depending on the omsotic pressure of the solution.

There are a variety of ways of doing this, such as using ultra high pressure reverse osmosis, however the most promising method is to use Osmotically Assisted Reverse Osmosis (OARO). The key to this process is lowering the differential osmotic pressure between the solution to be concentrated and the ‘permeate’ side of the membrane, by introducing a draw solution on the permeate side. Then applying hydraulic pressure, just like reverse osmosis, allows much higher concentrations to be achieved.

Diagram of osmotic processes, including forward osmosis and osmotically assisted reverse osmosis
Osmotic Processes

Processes incorporating OARO, significantly extend the range of membrane based concentration at a fraction of the energy consumption of competing processes. This is the key to their potential success.

ZLD or Minimal Liquid Discharge (MLD) processes are generally comprise a number of discrete steps, to minimise the overall operating and capital costs. Starting from reverse osmosis and ending in an evaporator crystalliser. On a typical ZLD system that does not include OARO, the energy costs of the thermal steps are about 90% of the overall opex. It’s apparent from the figure below, just what a significant impact OARO type processes have on the operating costs of ZLD or MLD systems.

Brine concentration processes

These OARO systems may be operated on their own or in conjunction with forward osmosis, with all its inherent advantages, such as low fouling and a wide variety of membrane materials and geometries available. This flexibility of design allows the use of the OARO process to be used in a large number of processes and industries, which Osmotic Engineering has substantial experience in. Basically, anywhere a solution needs to be concentrated at low operational cost when compared to conventional thermal methods. More information on one of these processes can be found in the recent Water Today magazine article.

Osmotic Engineering has a wealth of experience in the development, design, engineering and operation of OARO, FO and osmotically driven membrane processes. We can therefore offer a unique range of consulting engineer services in this new field. Please contact us for more information and to discuss your requirements.