Counter Flow Reverse Osmosis

Membrane brine concentration

Reverse osmosis (RO) can produce fresh water from salt water with low energy requirements, but RO generates large volumes of brine waste. Existing brine concentration technologies are expensive and consume too much energy. There is a critical need for a membrane process capable of concentrating high salinity water with low power consumption.


Osmotics’ Counter Flow Reverse Osmosis (CFRO) process is a low-energy, low-cost membrane process for high-salinity water treatment. Osmotics concentrates salt water to the saturation limit at pressures low enough to allow use of commercial RO membranes and equipment. It uses only half the energy required by legacy brine concentration technologies. The CFRO process has profound implications for industrial and municipal water treatment in the United States and around the world, with significant cost reduction and environmental benefits. The CFRO process is enabling inland desalination and water reuse projects that were not previously possible due to lack of viable brine management solutions.

The Technology

In the CFRO process, a dilute saline solution is introduced to the product side of the membrane. This reduces the osmotic pressure differential across the membrane and thereby reduces the required feed pressure. Brine is cascaded through multiple CFRO stages without exceeding the maximum pressure limitations of standard RO equipment, producing a saturated brine stream and purified product water stream. A schematic diagram of the pump pressure requirements for a CFRO process is given below.

A cascade of CFRO units arranged to enable step-wise concentration of the brine is illustrated in the following figure.