Yes, A Membrane Can Do That.
For desalination applications where thermal sources are not available, Gradiant offers the counterflow reverse osmosis (CFRO) process. The CFRO process can concentrate salt water to the saturation limit with commercial RO membranes and equipment.
Membrane brine concentration has profound implications for industrial and municipal water treatment in the United States and around the world, with significant cost reduction and environmental benefits compared to legacy mechanical vapor compression (MVC) evaporators. The CFRO process is enabling inland desalination and water reuse projects that were not previously possible due to lack of viable brine management solutions.
In the CFRO process, a dilute saline solution is introduced to the product side of the membrane to reduce the osmotic pressure barrier and thereby reduce the required feed pressure. Brine is cascaded through multiple CFRO stages, concentrating it to saturation for disposal or crystallization while producing a purified product water stream for beneficial reuse. A cascade of CFRO units arranged to enable step-wise concentration of brine is illustrated in the following figure.
The CFRO process uses less than half the energy of the most efficient evaporator and costs about half as much.