How Does Reverse Osmosis Work?

In the world of Water Resources, reverse osmosis is a term that is thrown around a lot. It is a vital process it creating usable water, whether it be for irrigation or drinking. Reverse osmosis allows for the removal of salt from water, but it also allows for the removal of bacteria from wastewater. But how does it work?

In most reverse osmosis systems, there needs to be filtration before this process begins. A filter, typically made out of porous material such as carbon, filters out large pieces of sediment. Such sediment may clog other stages of the process, which may decrease the effectiveness of the reverse osmosis system.

Then, water is passed through the reverse osmosis membrane. In this membrane, many molecular-level particles are removed. This membrane is permeable, but the pores are so small that only water can flow. Pressure forces drive this water through, but leaves impure particles behind.

In cases of desalination, the membrane pulls away salt, which is regarded as incredibly difficult to remove from water. This emphasizes the necessity of a membrane that has pores that are barely small enough to block out dissolved salt particles.

The process that drives reverse osmosis is pressure. In normal osmosis, particles are driven from areas of low concentration to high concentration through a permeable surface. This creates an osmotic pressure, which such a reverse osmosis system needs to overcome (hence the name). So, it creates pressure that pushes from high concentration from low concentration. And once this osmotic pressure reaches equilibrium with the system, all of water has reached the low concentration side (with little to no dissolved particles).

Reverse common is a key process to understand when it comes to water resource engineering. It’s use is common in nearly every area of this field, and its benefits are endless. From cleaning wastewater to making saltwater drinkable, civil engineers must recognize its universality throughout modern infrastructure.