Ask an Expert – Reverse Osmosis Temperature Differential


Hi Chris,

We are working on a Gold Mine in Ontario and as part of the scope we have a small RO plant planned for the treatment of excess surface water.

This unit will possibly be small in size and will only be used for managing and treating the excess surface water that will be discharged into a river stream that makes it’s way to a lake.

Can you please provide some generic rules of thumb regarding temperature range for an RO unit?



A reverse osmosis (RO) water treatment process utilizes a semi permeable membrane to act as a barrier to dissolved salts and inorganic materials, allowing for separation of these contaminants from a solution. The process itself does not typically impart energy to a water stream. Provided that the RO unit and associated piping are sized adequately for the water flow, the concentrate and permeate water temperate are generally considered to be equal to the influent water temperature.

While a RO unit does not typically affect a system’s water temperature, the influent water temperature does affect the RO system performance. Standard test conditions for RO equipment are typically 25o C. As such, care must be taken when sizing RO equipment that will be used in a cold climate.

Lynda Smithard, PEng, COO